ABSTRACT

The Triassic to Late Cretaceous deep-marine sediments of the Hamrat Duru Group, Oman Mountains, represent a subunit of the Hawasina nappe-complex which was deposited in a deep marine basin. During the Late Cretaceous SSW-directed obduction of the Semail Ophiolite, the Hawasina complex was emplaced onto the autochthonous cover of the Arabian basement, while the original configuration of the basin was destroyed.

New lithostratigraphic results and high-resolution radiolarian and conodont biostratigraphy lead to a revised stratigraphic scheme of the Hamrat Duru Group which conforms with the standard stratigraphical nomenclature. The Hamrat Duru Group is divided into six formations: (1) The Early Triassic (Olenekian) to Late Triassic (Upper Norian) Zulla Formation (Limestone and Shale Member, Sandstone and Shale Member, Radiolarian Chert Member and Halobia Limestone Member); (2) The Late Triassic (late Norian to Rhaetian) Al Ayn Formation; (3) The Early Jurassic (late Pliensbachian) to Middle Jurassic (early Callovian) Guwayza Formation (Tawi Sadh Member and Oolitic Limestone Member); (4) Middle Jurassic (Callovian) to Late Cretaceous (Cenomanian?) Sid’r Formation (Lower Member, Upper Member); (5) Late Cretaceous (Cenomanian? to Santonian?) Nayid Formation; and (6) Late Jurassic (early Callovian) to Early (Late?) Cretaceous Wahrah Formation. Most of the lithostratigraphic units (formations and members) show isochronous boundaries between the different outcrop areas.

The stratigraphic architecture of the Hamrat Duru Group megasequence is controlled by alternating siliciclastic and carbonate sedimentation possibly related to the second-order sea-level variations. The sediments accumulated on the continental rise of the Arabian margin mostly by submarine sediment-gravity flows and hemipelagic to pelagic rainout. A close relationship of the evolution of the Arabian Platform and the adjoining slope and basinal environments is evident. Changes in carbonate supply, oceanographic circulation and/or variations in silica productivity resulted in two distinct phases of radiolarian sedimentation. The first phase corresponds to the Triassic late Anisian-early Norian time interval; the second started in the Early Jurassic late Pliensbachian and lasted, with some interruptions, up to the Late Cretaceous Coniacian. The litho- and biostratigraphic similarities between the Mesozoic Hamrat Duru Basin of the northern/central Oman Mountains and the Mesozoic Batain Basin of northeastern Oman are seen as related to Neo-Tethys-wide palaeoceanographic changes and suggest a strong interdependence of the two basins with the evolution of the Arabian Platform.

INTRODUCTION AND PREVIOUS WORK

Regional Geotectonic Framework

During the last decades of geological research it has been generally accepted that the allochthonous cover of the northeastern Arabian Plate originated from the southern margin of the Neo-Tethys Ocean (Figure 1a). The Late Permian and Mesozoic Hawasina sediments were deposited in the Hawasina Basin which consisted of at least two sub-basins (Figure 1b), before being emplaced in a SSW direction onto the autochthonous cover of the Arabian Platform, coeval with the late Coniacian to Campanian (84-80 Ma) obduction of the Semail Ophiolite (Allemann and Peters, 1972; Glennie et al., 1973; Béchennec, 1987; Bernoulli et al., 1990; Cooper, 1988). The Hamrat Duru sedimentary rocks represent a base of slope and abyssal plain sedimentary facies of a distinct sub-basin of the Hawasina Basin along the Arabian Platform. The sedimentation in the Hamrat Duru Basin was mostly characterised by submarine sediment-gravity flows such as turbidity currents and debris flows, as well as hemipelagic rain out and radiolarian productivity (Glennie et al., 1974; Murris, 1981; Cooper, 1986).

The first comprehensive study of the Oman Mountains was presented by Glennie et al. (1973, 1974) who recognised five main structural units (Figure 2). From bottom to top, these are:

  1. Autochthonous A (folded Proterozoic to Palaeozoic rocks) and B (Permian to Cretaceous carbonates and deeper marine sediments), representing the lowermost outcropping tectonic units,

  2. Sumeini Nappes, characterized by Neo-Tethyan slope deposits of Permian to Cretaceous age,

  3. Hawasina Nappes, subdivided into several groups comprising Permian to Cretaceous basinal sediments,

  4. Semail Ophiolite, sequence of Cretaceous oceanic crust, and

  5. Neoautochthonous, sedimentary platform sequence ranging in age from the Late Cretaceous to Miocene, which unconformably overlies all older units.

Previous Stratigraphic Work and Palinspastic Reconstructions

Glennie et al. (1973, 1974) interpreted the Hawasina Complex as a stack of nappes with sediments deposited in an oceanic basin along the northern Arabian passive continental margin. Mainly based on lithostratigraphic criteria, they subdivided the Hawasina sediments into the Hamrat Duru Group and into several formations such as Halfa Formation, Haliw Formation, Wahrah Formation, Al Ayn Formation, Ibra Formation, Al Aridh Formation, and the Oman Exotics. Glennie’s et al. (1974) first palinspastic reconstruction of the Hawasina Basin assumed Permian to Late Triassic-Early Jurassic rifting and simple in-sequence thrusting during emplacement. Later workers (see below) correlated the facies between the tectonic units to set up regional stratigraphic schemes, grouping similar sediment types of similar age throughout the area as a whole.

Béchennec (1987) synthesised the stratigraphic work of the BRGM (Bureau de Recherches Géologiques et Minières) which was carried out during regional mapping of the Central Oman Mountains. The geological studies carried out between 1984 and 1993 by the BRGM resulted in the publication of geological maps at different scales of the entire Oman territory (e.g. Béchennec et al., 1993; Le Métour et al., 1995; Michel, 1993). New palaeontological data allowed more accurate dating of many stratigraphic sequences (Béchennec et al., 1993; Béchennec et al., 1990; De Wever et al., 1988). Most of the formations established by Glennie et al. (1974) were abandoned or were redefined by the BRGM geologists (Figure 3). This has led to considerable confusion with respect to the Hamrat Duru lithostratigraphy, especially as Béchennec and co-workers modified their stratigraphic scheme repeatedly as their mapping project progressed (Figure 3). The problems related to this approach are discussed in Robertson et al. (1990). According to the BRGM, the evolution of the South Tethyan Oman continental margin started in the Early to Middle Permian with a phase of extension. This rifting led to the formation of the Hamrat Duru Basin, separating the Arabian Platform in the south from the Baid Platform in the north. During the Middle Triassic, desintegration of the Baid Platform caused the development of new palaeogeographic realms, i.e. the Al Aridh Trough, the Misfah Platform and the Umar Basin (Figure 1b; Baud et al., 1993; Béchennec et al., 1990; Béchennec et al., 1988; Pillevuit, 1993; Pillevuit et al., 1997). The palinspastic reconstruction of Béchennec et al. (1988) is, as that of Glennie et al. (1974), based on the assumption of simple in-sequence thrusting during emplacement.

Cooper (1987) carried out the first comprehensive sedimentological study of the deep-water sediments of the Hamrat Duru Group, from the Dibba Zone (Musandam) in the northwest to the Semail Gap in the southeast. He extended the stratigraphic scheme of Glennie et al. (1974) by correlating sediments between different tectonic units and grouped sediments of similar facies and age throughout the area as a whole (Figure 3). Cooper (1987) further subdivided the Triassic Zulla Formation into four informal units (Figure 3). Cooper’s reconstruction of the Mesozoic Hawasina Basin was supported by numerous measured sections and led him to differentiate two individual deep-water basins (the shale-rich Al Ayn Basin and the Duru Basin) separated by a submarine high (Al Ayn Basin ridge; Cooper, 1987, 1990).

Bernoulli and Weissert (1987) and Bernoulli et al. (1990) dated the Radiolarian Chert Member of the Triassic Zulla Formation using radiolarians and also discussed the age of the other members of the formation. Previously, the Zulla Formation was regarded as a long-ranging very distal unit consisting mainly of chert with shale interbeds (Glennie et al., 1974); whereas it is now seen as only the Triassic part of a relatively proximal succession. Bernoulli and Weissert (1987) and Bernoulli et al. (1990) also analysed the Triassic palaeoenvironmental changes in the source areas and discussed basin-wide palaeoceanic fluctuations. Finally, the finding that the sequence of thrusting is complex (including in-sequence and out-of-sequence thrusting) led to a new palinspastic reconstruction of the Hawasina Basin which represented a significant improvement of Glennie et al.’s (1973, 1974) reconstructions (Bernoulli and Weissert, 1987; Bernoulli et al., 1990).

Recent studies in the Batain Plain, eastern Oman Mountains revealed that latest Carboniferous to Early Permian break-up of Gondwana led to the formation of two separate basins, the Batain Basin and the younger Hawasina Basin (Figure 1a, Immenhauser et al., 2000).

Rationale of this Study

As laid out before, the different stratigraphic concepts proposed led to considerable confusion regarding the Hamrat Duru stratigraphy (Figure 3). The situation is even more complicated because the same name for a formal stratigraphic unit (e.g. Sid’r and Nayid formations) commonly refers to different lithologies and/or time periods. Moreover, the present biostratigraphy of the Hamrat Duru succession, based largely on reworked platform and slope-derived biogenic material remains inaccurate and incomplete. Therefore, it is necessary to improve the time control and the understanding of the stratigraphic architecture of the Hamrat Duru Group in order to gain a better understanding of the evolution of the Hawasina Basin in time and space.

In this paper we present a stratigraphic architecture that gives evidence for the development of a passive continental margin from the rifting phase up to the closure of the Neo-Tethys Ocean. We provide new lithostratigraphic data, radiolarian and conodont biostratigraphies in order to: (1) develop a coherent and comprehensive stratigraphic scheme for the Hamra Duru Group; (2) determine the basinwide time-lithofacies relationships; and (3) discuss the tectono-stratigraphic evolution of the Hamrat Duru Basin from the Triassic to the Late Cretaceous.

METHODS

This study is based on 27 measured sections, located in the Oman Mountains between the Hawasina Window and the Wadi Bani Khalid (Figure 2). Locations of the individual sections are given in Universal Transverse Mercator (UTM) grid data using the World Geodetic System (WGS) 84. Sections were measured to a resolution of about 10 cm and their total length is 5,800 m. Grain size was estimated directly in the field, either with a ruler for coarse to very coarse-grained sediments, or using a grain-size comparison chart for sand-sized sediments. Bed thickness is described using the descriptive classification after Ingram (1954) in Blatt et al. (1980). Thin sections were studied with standard petrographic techniques.

The classification of sandstones used is that presented by Pettijohn et al. (1987). The scheme used for the limestones divides them on the basis of grain size after Tucker (1991). The classification of hybrid sandstones which contain a non-clastic component is also based on Tucker (1991). Palaeocurrent observations were made on flute casts and ripple/dune cross-bedding and corrected, where necessary, for plunge and folding (Blechschmidt, 2002).

In this paper simplified logs are shown that emphasize lithology, grain size and schematic bed thickness (Legend, Figure 4). These logs include important biostratigraphic data (B: general rock samples, BR: radiolarian samples, BC: conodont samples) and basic lithologic informations. Because of lateral facies changes and due to some incomplete sections, most of the formations are documented by at least two overlapping sections providing in total a complete succession and/or local variations between these two sections. The sections described in the text are numbered 1 through 27 and section numbers are shown in bold type (e.g. Figure 2: 1).

The biostratigraphy is mainly based on radiolarians extracted from about 700 samples of siliceous Triassic to Late Cretaceous sedimentary rocks. The radiolarian sample numbers together with the determined ages are shown on the logs. However, due to limited space and high species diversity usually only the assemblages of bottom and top samples of each member/formation are listed in the Appendix. Extracting the radiolarians from siliceous limestones and cherts was possible with the etching technique developed by Dumitrica (1970) and first described by Pessagno and Newport (1972). Conodont data were obtained from 20 limestone samples and supplement the Triassic radiolarian ages. Those samples shown on the logs or discussed in the text are listed in the Appendix. Benthic foraminifers were determined by R. Martini and L. Zaninetti in thin sections and were helpful in dating Middle Jurassic to Early Cretaceous carbonates. These new biostratigraphic data allow an accurate chronostratigraphic dating of the lithostratigraphic units and their regional correlation between the different outcrop areas of the Hamrat Duru Group.

The new stratigraphic scheme presented here follows the rules of the North American Commission on Stratigraphic Nomenclature (Nomenclature, 1983) and the guidelines for stratigraphic classification, terminology and procedure defined by Hedberg (1976), Holland et al. (1978) and Salvador (1994).

REVISED STRATIGRAPHY OF THE HAMRAT DURU GROUP

The Late Permian to Late Cretaceous Hamrat Duru Group is named after the Hamrat ad Duru Range in the southwestern foreland of the Oman Mountains and was first introduced by Haremboure and Horstink (1967). The main exposure belts of the Hamrat Duru Group are in the southern mountains (Hamrat ad Duru Range, Jabal Hammah, Jabal Safra, Jabal Wahrah, Hubat antiform, Al Hammah Range and Birkat al Mawz area) and in the central and northern Oman Mountains (Wadi Al Ayn, Hawasina Window) (Figure 2). Throughout the fore-mentioned regions, no sedimentary record older than Early Triassic is known. Deep-water sediments and volcanics of Permian age are scarce and occur in tectonically isolated outcrop areas. They are strongly deformed and no complete succession from the Permian into the Triassic of the Hamrat Duru Group was reported until now. Therefore the relation of the Permian successions to the Hamrat Duru Group is controversial. Glennie et al. (1974) and Béchennec et al. (1990) suggested that the Permian lies at the base of the Hamrat Duru Group; whereas its base is the Triassic Zulla Formation according to Cooper (1987). The Permian is not further discussed in this paper.

The Hamrat Duru Group consists of six formations extending from the Early Triassic to the Late Cretaceous; from bottom to top: Zulla, Al Ayn, Guwayza, Sid’r, Nayid, and Wahrah. The Wahrah Formation is included within the Hamrat Duru Group as it represents a distal facies equivalent of the Sid’r and the Nayid Formations (Béchennec et al., 1986, 1988, 1993; Cooper, 1990) (Figure 3).

With the exception of the Al Ayn, Sid’r and Nayid formations, the proposed nomenclature (Figure 3) follows that of Glennie et al. (1973), Cooper (1987) and Bernoulli et al. (1990). The Sid’r and Nayid formations sensu BRGM (mapping project 1984-1990, 1993) represent easily-mappable lithostratigraphic units and have become well established in the literature. Therefore, we follow the BRGM lithostratigraphic definition for these two formations (Figure 3). The sandstone of the Al Ayn Formation of Glennie et al. (1974) has been included within the Hamrat Duru Group by Bernoulli and Weissert (1987) after its recognition as a synonym of the Guwayza Sandstone (Figure 3). Based on a careful revision of the Guwayza Sandstone, this unit is now divided in two parts of which the lower one is revived as Al Ayn Sandstone in a new sense. The upper part is introduced as the new Tawi Sadh Member of the Guwayza Formation proper. The Al Jil and Matbat formations sensu BRGM (Béchennec, 1988) are considered as synonyms of well established members of the Zulla Formation and their use cannot be further supported.

Zulla Formation

Type section

The stratotype sequence was established by Glennie et al. (1974) in Wadi Zulla (=Wadi Dil) in the Hawasina Window (Figure 2: 1) and later slightly modified by Cooper (1987) at the same locality.

Lithologically identical sections were measured by Bernoulli et al. (1990) in the Wadi Al Ayn area, some 50 km to the southeast (Figure 2). This is also the type region of the Al Jil and Matbat formations of Béchennec (1987) which are regarded fully, or partly, as synonyms of the Zulla Formation. Cooper (1987) and Bernoulli et al. (1990) recognised four lithostratigraphic units in the Zulla Formation. This subdivision is retained, but the basal ‘Turbiditic Calcarenites and Shales’ member of Bernoulli et al. (1990) is replaced by the ‘Limestone and Shale Member’ to avoid the genetic connotation (Figure 3).

The Zulla Formation in the type area is tightly folded and shows a low-grade metamorphic overprint that destroyed a major part of the microfaunal content, except conodonts. In the Wadi Al Ayn area (Figure 2) the formation is only slightly deformed and has produced stratigraphically relevant radiolarian faunas. The sections in this area (Figure 2: 4 and 5) are well exposed and show a complete succession of all lithostratigraphic units. They are thus used for the litho- and biostratigraphic subdivision of the Zulla Formation as described below, and the section in Wadi Al Ayn (Figure 4: 5, and Figure 5a) is proposed as a hypostratotype.

Boundaries

The Zulla Formation is thrust over the Sumeini Group in the Hawasina Window and over the duplexes of the Hamrat Duru Group in the Wadi Al Ayn area (Cooper, 1987). Therefore, its base is always tectonic, whereas the upper boundary is undisturbed and transitional to the overlying Al Ayn Formation.

Age

According to previous studies (Cooper, 1987; Bernoulli et al., 1990; Béchennec, 1987; Béchennec et al., 1990, 1993) and new data shown in Figure 4, the Zulla Formation extends from the Early Triassic (Olenekian) to the Late Triassic (late Norian; Figure 3). There is no indication for a Permian age of the base of the Zulla Formation in the investigated areas.

Synonymy

The four members of the Zulla Formation described in this paper are identical to the Zulla I to IV units of Cooper (1987) and Bernoulli et al. (1990) (Figure 3). The Limestone and Shale Member, the Sandstone and Shale Member, and the Radiolarian Chert Member correspond to the Al Jil Formation of Béchennec et al. (1988). The Halobia Limestone Member represents the Lower Member of the Matbat Formation (Mb1) of Béchennec et al. (1988).

Zulla Formation - Limestone and Shale Member

Lithology and sedimentary features

The measured thickness is about 25 m (Figure 4: 5) but the base of the unit is strongly deformed. The succession consists of partially calcareous grey-green shale with intercalations of 10-30 cm thick peloidal mudstone and calcarenite and thinly bedded platy calcilutite in the basal part. The rare calcarenite beds contain transported and redeposited shallow-water carbonate material (e.g. ooids, pellets).

The sediments are characterised by: (1) normal-grading, parallel lamination and/or ripple cross-bedding mainly from large-scale linguoid ripples (calcarenites, Figure 5b); (2) non-graded massive to platy calcilutite; and (3) structureless massive to platy shale. Starved ripples are also common. Cross-bedding indicates transport of the sediment from south to north and from southwest to northeast (Blechschmidt, 2002).

Boundaries

The base of the Limestone and Shale Member is always tectonic and characterised by thrusts and associated folding. The contact to the overlying Sandstone and Shale Member is gradational and is arbitrarily set to the first appearance of dolomitic layers and silty shale.

Age

The conodont assemblages (Figure 2: 4 - Appendix: BC353, Figure 4: 5, BC769, BC355) reveal an early Olenekian (Smithian) to early Middle Triassic (late Olenekian-Anisian) age for the member.

Zulla Formation - Sandstone and Shale Member

Lithology and sedimentary features

The lower part of the succession is dominated by shale and beige dolomitic calcilutite and marked by a fining- and thinning-upward trend. The upper part consists of thinly to thickly bedded, well-sorted silty to sandy greenish quartz arenite and sublitharenite interbedded in a shale-dominated succession (Figure 5c). The sandstone beds are composed mainly of quartz (up to 95%) and lesser amounts of feldspar and lithic grains (up to 25%). They generally show normal-grading followed by parallel lamination and topmost cross-bedding passing upwards into structureless shales. Towards the top of the member a slight thickening of beds can be observed. Flute casts and cross-bedding indicate transport of the sediment from southwest to northeast (Blechschmidt, 2002). This unit reaches a stratigraphic thickness of about 30 m (Figure 4: 5).

Boundaries

The lower boundary of this member is set at the first appearance of prominent shale beds with rare dolomitic interlayers. The contact to the overlying Radiolarian Chert Member is also gradational and characterised by a shale-dominated level with rare intercalations of radiolarian chert and siltstone.

Age

The age of the Sandstone and Shale Member is bracketed by the conodont data of the underlying Limestone and Shale Member and the radiolarian data of the overlying Radiolarian Chert Member and corresponds, accordingly, to the late Olenekian (early Spathian) to middle/late Anisian.

Zulla Formation - Radiolarian Chert Member

Lithology and sedimentary features

This member consists of an approximately 50-70-m-thick sequence of thinly-bedded, red and/or green radiolarian ribbon chert with interbedded siliceous shale (Figure 5c). The upper part of the member is marked by an interval of brown weathering, fine-grained, redeposited calcarenite to calcilutite up to 3 m thick. The top of this member is dominated by green shale, green radiolarian chert and silicified marl.

The sediments are characterised by: (1) non-graded massive to platy radiolarian chert beds; or (2) radiolarian chert beds with graded radiolarian layers, parallel lamination and/or flaser bedding; and (3) platy, structureless intercalated shale. The chert beds can be laterally traced for several tens of metres before they wedge out. Some individual layers are characterised by chert nodules or lenses. The minor internal primary structures of the chert beds are sometimes destroyed by bioturbation (e.g. Chondrites and other unidentified ichnofossils).

Boundaries

The lower boundary was established at the level where the percentage of chert exceeds that of the shale and siltstone. The upper boundary is marked by the transition to the limestone and shale of the Halobia Limestone Member and it is set above the uppermost chert bed. Both lower and upper boundaries are gradational.

Age

The radiolarian assemblages indicate a late Anisian (Illyrian) age for the base of the Radiolarian Chert Member and an early Norian (early Lacian) for its top. Since radiolarians from the stratotype are poorly preserved the age of this member is based on assemblages extracted from the hypostratotype (Figure 4: 5 and Appendix) and from other sections such as the one in Wadi Bani Khalid (Figure 4: 26 and Appendix), one of the best sections for radiolarian biostratigraphy in the study area. The oldest radiolarian assemblage of the hypostratotype (Figure 4: 5 - BR419, Appendix) contains a radiolarian assemblage indicative of the late Anisian (middle-late Illyrian) Tiborella florida subzone of Kozur (1995). The same subzone is indicated by this radiolarian assemblage in all the other sections proving that radiolarian productivity started practically simultaneously throughout the Hamrat Duru Basin.

The radiolarian assemblage from the top of the hypostratotype of the Radiolarian Chert Member (Figure 4: 5 – BR437-BR438, see Appendix) contains a fauna with Capnodoce spp., Capnuchosphaera tricornis De Wever, Capnuchosphaera spp., Corum spp., Mostlericyrtium sitepesiformis Tekin, Selenella triassica Tekin, Xiphotheca rugosa Bragin, and a few other species described by Tekin (1999) from the early Norian (E. abneptis conodont Zone) of Turkey. A much richer assemblage at the same stratigraphic level was found at the top of this member in the Wadi Bani Khalid section (Figure 4: 26 - BR929, Appendix). In both sections this radiolarian assemblage is at a few metres below the level with Halobia beyrichi Moj. (Figure 4: 5: B345, 26: B1010) indicative of the early Norian.

Between the late Anisian and the early Norian almost all radiolarian zones established in Europe (Kozur and Mostler, 1994) and Japan (Sugiyama, 1997) can be recognized in the succession of the Radiolarian Chert Member. A detailed radiolarian biozonation of the stratigraphic interval recorded in this member as well as a taxonomic study of the radiolarians will be presented separately.

Zulla Formation - Halobia Limestone Member

Lithology and sedimentary features

The total stratigraphic thickness of the Halobia Limestone Member measured in the Wadi Al Ayn (Figure 4: 5) and Hawasina Window (Figure 2) is about 60 m thick. The lower part of the sequence is dominated by partially silicified grey-green shale, thinly-bedded radiolarian-bearing calcilutite and layers packed with filaments, thinly-shelled pelagic bivalves of the Halobia type (Figure 5d). The bivalve shells are generally aligned parallel to the bedding. The base of the Halobia Limestone Member contains both, in the Wadi Al Ayn outcrop area (Figure 4: 5) and in the Wadi Bani Khalid (Figure 4: 26), a marker horizon with Halobia beyrichi Mojsisovics (Figure 5d). Up-section, medium-bedded calcarenites consisting of redeposited platform material, such as ooids, echinoderm and mollusc fragments increase in abundance, associated with a higher input of siliciclastic detritus (quartz and feldspar grains and shale clasts). The often-folded, respectively tectonically truncated, upper part of this member consists of up to 20 m of shales alternating with calciturbidites and rare sand- and siltstones (Figure 4: 5 and 26). This interval is rarely well exposed and until now has been variously incorporated in the lower Guwayza Formation, the Al Ayn Formation or the lower Matbat Formation (Glennie et al., 1974; Béchennec, 1986; Figure 3). This is not consistent with our new data, which indicate a stratigraphic gap and the main depositional sequence boundary above and not below this interval.

The sediments are characterised by: (1) non-graded massive to platy calcilutite; (2) normally-graded, parallel laminated and/or ripple cross-bedded calcarenites; and (3) structureless shale. Cross-bedding indicates transport of the sediment from west to east and from southwest to northeast (Blechschmidt, 2002). The primary sedimentary structures in the basal part of the sequence are often disturbed by bioturbation (e.g., Chondrites, Ophiomorpha, Bergaueria, Imponoglyphus torquendus, Nereites, Thalassinoides, Halymenites, Helminthopsis, Archeozostera, A. Wetzel, written communication, 2002).

Boundaries

The lower boundary of this member is gradational. The contact to the overlying Al Ayn Formation is drawn at the appearance of massive sandstone beds with no or only thin shale intercalations (Figure 4: 5).

Age

Based on the age of the top of the Radiolarian Chert Member and on the conodonts and pelagic bivalves species, the Halobia Limestone Member is early to late Norian in age (sections in the Wadi Al Ayn area: Al Jil, Figure 2: 4 - Appendix: BC349, BC351; Al Ayn, Figure 4: 5 - B345 - Halobia beyrichi Mojsisovics, BC767; Tawi Shannah section, Figure 4: 7 - Appendix: BC347; and from Wadi Bani Khalid, Figure 3: 26 - B1010 - Halobia beyrichi Mojsisovics).

Regional variations

The Zulla Formation in the Wadi Al Ayn and in the Hawasina Window shows no significant lateral variations in thickness and facies. Further to the southeast, in the Zukayt area (Figure 2: 19), carbonate beds increase in abundance and the Sandstone and Shale Member is devoid of sandstone beds. In the Wadi Bani Khalid outcrop area (Figure 2 and 4: 26), the succession shows a reduced thickness of both the Radiolarian Chert Member (c. 40 m) and the Halobia Limestone Member (c. 35 m). The sandstone facies of the Sandstone and Shale Member is absent once more and the member is dominated by shale with minor radiolarian-bearing calcilutite in the upper part.

Al Ayn Formation

Type section

The type locality of the Al Ayn Formation is situated in Wadi Al Ayn close to the village of Tawi Shannah (Figure 2: 7). In this area of the central Oman Mountains this formation is well exposed, but very poor in relevant index fossils. The Wadi Saal area in the southern Hamrat Ad Duru Range (Figure 2: 10), in contrast, shows an almost complete succession with well exposed conglomerates containing stratigraphically relevant faunas of reworked sponges, corals and foraminifers. Therefore, the Wadi Saal section is proposed as a hypostratotype of the Al Ayn Formation.

Lithology and sedimentary features

The Tawi Shannah section (Figure 6: 7,Figure 7a) shows one of the most complete successions of the Al Ayn Formation in the Wadi Al Ayn area. Its stratigraphic contact to the underlying Zulla Formation and the overlying Guwayza Formation is well exposed. The sequence consists of 140 m of thinly- to thickly-bedded quartz arenite and interbedded shale. At the type locality a 10 m thick transition interval with thinly-bedded limestone, cherty shale and siltstone is found between the Zulla and Al Ayn formations. This interval is overlain by a 30-m-thick alternation of greyish-green shale and siltstone with a pronounced coarsening- and thickening-upward trend grading into brown-weathered, decimetre- to metre-bedded, medium- to coarse-grained quartz arenites and interbedded shales comprising the middle part of the formation (c. 90 m). The uppermost c. 25 m of the formation show a general fining- and thinning-upward trend grading into a shale facies with subordinated thinly-bedded sandstone and siltstone.

The sediments of Al Ayn Formation are characterised by: (1) normally-graded, parallel laminated and/or rippled sandstones with common convolute bedding (Figure 7a); and (2) interbedded structureless shales and laminated silty shales. In the middle part of the sequence, thickly-bedded, amalgamated beds are common. In the lower and upper parts of the succession thickening-upward small-scale cycles are well developed, whereas in the middle part fining-upward small-scale cycles are partially observed. Flute casts and current ripples indicate mainly north and east directed sediment supply.

A well-preserved ichnofauna including Palaeodictyon, Desmograpton, Desmograptus pamiricus, Circulichnus, Thalassinoides, Helminthopsis, Palaeophycus, Imponoglyphus, Glockerichnus, Protopalaeodiction, Nereites, Nereites labyrinthica, Rhabdoglyphus, Phycosyphon, Megagrapton can be observed at the base of many beds (A. Wetzel, written communication, 2002).

Boundaries

In most of the studied areas, the lower part of the formation is tectonically truncated, except in the Hawasina Window and the Wadi Al Ayn area where the formation conformably overlies the Zulla Formation. The boundary to the overlying Guwayza Formation is marked by an abrupt change to a shale-dominated facies including poorly exposed silicified lime- and mudstone.

Age

Due to the lack of index fossils, the age of the Al Ayn Formation in most of the outcrop areas can only be determined indirectly. Based on conodont data from the underlying top Zulla Formation and the radiolarian data from the overlying Tawi Sadh Member, a Latest Triassic (Rhaetian) age is assumed for the Al Ayn Formation. Common conglomerates in the middle and upper part of the succession in the Wadi Saal (Figure 6: 10) and Jabal Safra (Figure 2: 21) contain reworked reef talus with abundant sponges and corals (Figure 6: 10 - B309/2, B310/2, B313/2, B317/2, B318/2 and B320/2 - Disjectopora sp. and Spongiomorpha sp., M. Bernecker, written communication, 2002, Figure 7b) and foraminifers such as Galeanella sp. (Figure 6: 10 - B309; R. Martini and L. Zaninetti, written communication, 2001) which prove a Late Triassic (Norian to Rhaetian) age close to the top of the Al Ayn Formation. No indication for a Jurassic age was found.

Synonymy

The Al Ayn Formation incorporates part of the Sandstone Member of the Guwayza Formation and the Al Ayn Sandstone (Al Ayn Formation) as defined by Glennie et al. (1974), the Guwayza Sandstone Formation established by Cooper (1987) and the siliciclastic part of the Upper Member of the Matbat Formation (Mb2 – ‘russet sandstone’) as defined by Béchennec et al. (1986) and Béchennec (1987).

Regional variations

Besides lateral variations in thickness, the Al Ayn Formation shows a large variability in composition. In contrast to the northwestern outcrop areas (Figure 2: 1, 4 to 7), which are dominated by a quartz arenite lithofacies (quartz > 90%), the southern and southeastern outcrop areas of the Oman Mountains (Figure 2: 10, 18, 20, 21 and 22,Figure 7b) are characterised by a more mixed carbonate/siliciclastic lithofacies (calcarenaceous sandstone and quartz-bearing calcarenite) with common limestone conglomerates as described above. However, the variability in thickness and in facies of the Al Ayn Formation is difficult to quantify because most of the successions are incomplete due to thrust-contacts to under- or overlying tectonic units.

Guwayza Formation

Type section

The Guwayza Formation (including the Sandstone Member and the Limestone Member) established by Glennie et al. (1974) is named after the Wadi Guwayza in the eastern Hamrat Ad Duru Range (Figure 2). The Guwayza Formation was subdivided into the Matbat Formation and overlying Guwayza Formation sensu stricto and redefined several times by the BRGM team (Figure 3). Based on lithological arguments, the Guwayza Formation is herein revised and divided into two formal, mappable lithostratigraphic members that are from base to the top: the Tawi Sadh Member and the Oolitic Limestone Member (Figure 3).

Guwayza Formation - Tawi Sadh Member

Type section

The newly introduced Tawi Sadh Member is named after the nearby small village of Tawi Sadh, located in Wadi Mu’aydin (Figure 2 and 8: 18) at the southern extension of Jabal Akhdar. Other sections have been measured in the Wadi Muti (Figure 2 and 8: 20,Figure 9a) and in the Jabal Safra area (Figure 2: 21).

Lithology and sedimentary features

The lithological properties of the Tawi Sadh Member are highly variable, and in places the member dies out altogether. At the type locality (Figure 8: section Wadi Mu’aydin, 18) the whole member is characterised by greenish to dark-grey shale. The lowermost part consists of more than 45 m of grey-green, thinly-bedded radiolarian chert and strongly silicified limestone up to 10 cm thick and interbedded dark shale and marl. Up-section the number of radiolarian chert beds decreases and up to 20 cm thick strata of brown-coloured calcarenite appear.

The upper part of the member is an approximately 100 m thick yellow-brown weathered, mixed carbonate/siliciclastic sequence (Figure 8: 18 and 20). Oolitic and pelletal calcarenites with a variable content of sand-sized quartz and limestone lithoclasts are the dominant lithologies in this interval. Minor cherty beds are also common. The detrital quartz content in the uppermost part of the Tawi Sadh Member commonly exceeds 50% of the grains (calcarenaceous sandstone). Up to 4 m thick sandstone beds are common. Coarse-grained sandstones and conglomerates with floating boulders of intraclasts are locally developed (Figure 9a). At the top of this sequence, a fast transition into the Oolitic Limestone Member is observed with decreasing content of siliciclastic detritus. The total thickness of the type section is 150 m.

The sediments are characterised by: (1) normally-graded, parallel laminated and/or rippled calcarenite and sandstone; (2) minor non-graded massive sandstone (partially with floating sandstone/limestone boulders); and (3) interbedded structureless shales. The radiolarian cherts and silicified limestones at the base of the member show minor parallel lamination and/or flaser structures. The thickness of single sandstone and calcarenite beds is laterally highly variable. Erosive contacts and slump structures are common, particularly in the upper part of the sequence. Flute casts indicate transport of the sediment from south to northwest/northeast.

Well-preserved ichnofossils (e.g. Halymenites, Chondrites, Protovirgularia, A. Wetzel, written communication, 2002) can be observed on the bases of fine-grained, thinly-bedded calcarenite beds in the middle part of the succession.

Boundaries

The base of the Tawi Sadh Member is generally poorly exposed or a tectonic contact characterised by thrusts and associated isoclinal folds. However, good exposures in Wadi Saal (Figure 6: 10) reveal a hitherto undetected paraconformity beween the sandstone facies of the Al Ayn Formation and the soft shales forming the base of the Tawi Sadh Member. A comparable succession is developed in the Tawi Shannah section (Figure 6: 7). The contact to the overlying Oolitic Limestone Member is gradational and is arbitrarily set at the base of the lowest massive oolitic limestone beds.

Age

Radiolarian assemblages from the studied sections reveal a late Pliensbachian? - early Toarcian age for the lower part of the member and an early or middle Bajocian age for its top. The base of the member, however is poorly constrained due to insufficient exposure conditions and because many successions are incomplete due to thrust contacts to underlying tectonic units. The occurrence of late Pliensbachian radiolarians closely above the base and the presence of Triassic fossils in the top of the underlying Al Ayn Formation, is seen as a clear indicator of a stratigraphic gap encompassing Hettangian and Sinemurian-early Pliensbachian. The radiolarian fauna from the base of the member is comparable with the late Pliensbachian to early Toarcian faunas from Oregon studied by Yeh (1987), containing, among other species, Bistarkum bifurcum Yeh, Canoptum anulatum Pessagno and Poisson, Napora relica Yeh, Pleesus aptus Yeh, Pseudoristola obesa Yeh. This fauna is the most frequently found in the sections described here. Late Toarcian and Aalenian radiolarians, otherwise, are comparably rare either because of facies or tectonics. One of the best sections regarding the radiolarian fauna of this time interval is located in the Jabal Safra area (Figure 2: 21) whereas the Aalenian fauna found in the Al Sawad section (Figure 8: 20 - BR560-590) is poorly preserved. The top of the Tawi Sadh Member was dated in the type locality (Figure 8: 18 - BR1131) as well as in several sections, as for instance in the southeastern part of Jabal Safra (Figure 2: 21 - Appendix: BR828) and in the section Kadrah Bani Dafa’a (Figure 2: 22 - Appendix: BR454, BR457) where the radiolarian assemblages indicate either an early or a middle Bajocian age.

Synonymy

The radiolarian chert level at the lower part of the member in the Wadi Mu’aydin area (Figure 2: 17, 18 and 20) was alternatively mapped as the upper unit of the Al Jil Formation or as the upper part of the Upper Member of the Matbat Formation (Béchennec et al., 1992; Hutin et al., 1986; Figure 3). The upper part of the Tawi Sadh Member (dominated by lithoclastic sediments) incorporates the Upper Matbat Member (Mb2) of Hutin et al. (1986). Glennie et al. (1974) and equally Cooper (1987) did not distinguish the differences between the Triassic sandstone sequence (Al Ayn Formation) and the Jurassic sandstone sequence (Tawi Sadh Member). In contrast, Al Sulaimani et al. (1991) pointed out that a separate level of at least 40 m in thickness is present consisting of yellow-brown weathered, partially quartz-bearing, lithoclastic limestone and green chert at the base of the oolite-dominated facies of the Guwayza Formation in the central Hamrat Ad Duru Range.

Regional variations

The largest variability in thickness and lithofacies of all units of the Hamrat Duru sediments is observed in the Tawi Sadh Member of the Guwayza Formation. The thickness decreases from more than 150 m in the Wadi Mu’aydin area to about 100 m in the Hamrat Ad Duru Range (Figure 2: 9 and 10, ca. 100 m, Figure 9b) and less than 50 m in the Jabal Safra area (Figure 2: 21). This change is accompanied by a diminishing amount of detrital quartz (Figure 9c). In the Jabal Safra (Figure 2: 21), Jabal Wahrah (Figure 2: 2), Wadi Al Ayn (Figure 4: 7) and Jabal Hammah area (Figure 1: 14), chert and sandstone are rare and the Tawi Sadh Member is represented by a high amount of shale and partially silicified limestone. In some of the outcrop areas it is therefore difficult to identify the Tawi Sadh Member because the characteristic lithofacies types are either missing or are represented by a thin level of less than 20 m of dark grey shale and minor silicified limestone layers.

Guwayza Formation - Oolitic Limestone Member

Type section

The Oolitic Limestone Member was first defined by Glennie et al. (1974) in the Wadi Guwayza, eastern Hamrat Ad Duru Range, as an informal Limestone Member of the Guwayza Formation. Here, the basal part of the Limestone Member sensu Glennie et al. (1974) is included in the newly introduced Tawi Sadh Member. Other localities exposing a well developed Oolitic Limestone Member lie in the south and southwest of the Jabal Akhdar area (see also Hutin et al., 1986). The sections described below are shown in Figures 8 and 10.

Lithology and sedimentary features

The successions in the Wadi Mu’aydin and Wadi Muti are rather thick and exceptionally well-exposed (Figure 8: 18 and 20 and Figure 10: 20,Figure 11a). There, the Oolitic Limestone Member is comprised of a more than 300-m-thick sequence consisting mainly of light grey-weathered, amalgamated metre-bedded, coarse-grained calcarenite dominated by resedimented ooids and carbonate lithoclasts such as fawn dolomite and dark coloured recrystallized limestone (Figure 11a). This coarse-grained facies forms three major intervals, each up to tens of metres in thickness (Figure 10: 20 and 10). These intervals are separated by predominantly calcilutite packages and subordinate calcarenite, radiolarian chert and shale (Figure 11b, Figure 7b). Common calcirudites in the middle and uppermost part are made up of thickly bedded carbonate conglomerates with boulders of mostly Triassic reefal and lagoonal limestones (Figure 11c) measuring up to several metres in diametre. These boulder to pebble-sized clasts are sub-rounded to rounded. The calcirudites are mostly clast-supported with an oolitic matrix. The near sheet-like conglomerate bodies can be traced for more than 25 km along the southern footwall of the Jabal Akhdar (Rathmayr, 2000). The clast composition of the uppermost conglomerate level is dominated by lagoonal dolomites (Triassic?), recrystallized dark bioclastic limestones (Liassic?) and intraclasts.

Generally, the sediments are characterised by: (1) normally-graded, parallel laminated and/or rippled calcarenite; (2) massive calcarenite partially with floating granules, rafted intraclasts and carbonate lithoclasts; (3) massive, mostly structureless calcilutite; (4) stratified, normally- or inversely- to normally-graded calcirudite; and (5) disorganised to normally-graded calcirudite (Figure 11c). Thick beds frequently containing oversized clasts are commonly amalgamated. Flute casts and large scale cross-bedding generally indicate sediment transport from south to north in the proximal facies and from northwest to the southeast in the most distal facies. At the base of fine-grained calcarenite beds ichnofossils are common (e.g. Thalassinoides, Helminthopsis, Palaeodictyon, A. Wetzel, written communication, 2002).

Boundaries

The lower boundary of the Oolitic Limestone Member is marked by the transition from quartz-bearing lithoclastic limestone and shale of the Tawi Sadh Member into ooid-dominated calcarenites. The lower boundary is arbitrarily set at the lowermost thickly bedded oolitic limestone. The top is characterised by a rapid transition or an abrupt contact to the silicified limestones, radiolarian cherts and spiculites of the overlying Sid’r Formation. A thin level of radiolarian-bearing green chert commonly marks the top of the member.

Age

Based on the age of the uppermost part of the underlying Tawi Sadh Member and some radiolarian faunas from a green radiolarian chert bed directly beneath the lowermost thickly-bedded oolitic limestone at the base of the Oolitic Limestone Member, the base of the latter is dated as middle Bajocian. Such green radiolarian chert beds were observed in Wadi Saal (Figure 2: 10 - Appendix: BR138) and Wadi Yail (Figure 2: 9 - Appendix: BR107) in a similar stratigraphic position. The age of the top of the Oolitic Limestone Member is again established on the basis of radiolarian faunas extracted from green radiolarian chert beds intercalated between the uppermost oolitic limestone beds in the Zukayt section (Figure 12: 19 - BR139) and in the Qusayd-Shulayshil section (Figure 2: 3 - Appendix: BR942). These faunas, although poorly-preserved, indicate a middle/late Bathonian to early Callovian age (UAZ 5-7 of Baumgartner et al., 1995). Reworked shallow water foraminifera (B49, B168, B175, B292, B300, B337, B367/C - Protopeneroplis, Trochammina, Trocholina, Endothyridae, Miliolidae, Textulariidae) in the oolitic facies of Wadi Saal (Figure 6: 10), Wadi Yail (Figure 2: 9), Jabal Safra (Figure 2: 21), Firq (Figure 12: 17) and Kadrah Bani Dafa’a (Figure 2: 22) also suggest a Middle to Late(?) Jurassic age (R. Martini and L. Zaninetti, written communication, 2001).

Synonymy

The Oolitic Limestone Member corresponds closely to the informal Limestone Member of Glennie et al. (1973), the Guwayza Limestone Formation of Cooper (1987), the Guwayza Formation in Hutin et al. (1986) and Béchennec (1987) (Figure 3). The Oolitic Limestone Member also incorporates the Lower Limestone Member of the Wahrah Formation sensu Glennie et al. (1973).

Regional variations

The Oolitic Limestone Member is represented by a large number of complete successions. These are marked by strong variations in the measured thickness with a distinct decrease in grain size and bed thickness from more proximal (17, 18 and 20: thickness > 300 m) to distal sequences (2: thickness < 70 m; 3: thickness < 100 m; 14: thickness < 100 m; 24: thickness < 70 m). The most proximal sequences are characterised by the occurrence of calcirudites and slump horizons with oversized blocks within the sequences. In all successions, the calcarenites are dominated by reworked ooids, in contrast to the calcirudites which consist mainly of platform-derived exoclasts of Permian and Triassic age.

In contrast to the outcrop areas discussed above, the uppermost part of age-equivalent successions in the Jabal Safra area (21), in the Wadi Sid’r (11), in Kadrah Bani Dafa’a (22) and in the south of the Hamrat ad Duru Range (10 and 11) is marked by particularly well-exposed metre-sized exotic carbonate olistoliths, associated with contorted strata produced by slumping. The olistoliths comprise Triassic limestone in Hallstatt facies, Permian reefal limestone (Hutin et al., 1986; Tozer and Calon, 1990) and limestone with Late Permian fusulinids (D. Vachard, oral communication, 2001). Since the Triassic in Hallstatt facies is not known from the autochthonous of the Arabian Platform, the source of these olistoliths was, according to Tozer and Calon (1990), not the Arabian Platform edge as assumed previously (Béchennec, 1988; Robertson, 1987; Searle and Graham, 1982), but oceanic buildups such as seamounts or isolated oceanic platforms.

Sid’r Formation

Type section

The Sid’r Formation was established by Glennie et al. (1974) in the Wadi Sid’r in the southeastern Hamrat Ad Duru Range (Figure 2: 11) and later redefined by Béchennec et al. (1986) and Béchennec (1987) in Wadi Nayid, in the northwest of the Hamrat Ad Duru Range (Figure 2: 13). Béchennec et al. (1986) recognised three lithostratigraphic units in the Sid’r Formation, a Lower Member (Sid’r1), a Middle Member (Sid’r2) and an Upper Member (Si2C). The Upper Member (Si2C), a radiolarian chert and silicified limestone-dominated unit, was later included in the basal part of the Nayid Formation (Béchennec et al., 1992). Thus the Sid’r Formation remained with only two members: Lower and Upper Members. Characteristic sections are shown in Figure 12 (17 and 19).

Boundaries

The lower boundary of the Sid’r Formation is in most sections marked by an abrupt or a gradual increase in silicification and a decreasing amount of redeposited carbonate material (Béchennec, 1987; Béchennec et al., 1986; Cooper, 1990, Figure 13a). The top of the Sid’r Formation is characterised by a rapid transition or by a sharp contact to strongly silicified fine-grained limestones and cherts of the overlying Nayid Formation.

Synonymy

The Lower Member sensu Béchennec et al. (1986, 1992) incorporates the Sid’r Formation of Glennie et al. (1973) and Cooper (1987). The Upper Member sensu Béchennec et al. (1992) represents the lower part of the Nayid Formation of Glennie et al. (1974) and the Nayid Formation of Cooper (1987).

Sid’r Formation - Lower Member

Lithology and sedimentary features

The Lower Member generally comprises partially to completely silicified, thinly- to medium-bedded calcarenite and calcilutite, radiolarian chert and minor shale; microbreccias are also common. The calcarenites and microbreccias in the Wadi Mu’aydin area (Figure 12: 17 and 19) contain a high amount of carbonate lithoclasts such as fawn dolomite and dark-grey coloured limestone. A characteristic feature of the Lower Member is the presence of nodular or layered cherts and silicified limestone and a pinky-orange colour (Figure 13a). The thickness of the member is highly variable, reaching more than 100 m (section Firq, Figure 12: 17). In section Firq, the Lower Member constitutes a fining-upward succession which grades into the silicified limestone, chert and radiolarian-bearing, calcilutite-dominated upper part of the member (Figure 12: 17). In section Zukayt (Figure 12: 19) the lower 20 m of the section are dominated by red and light-grey radiolarian chert, followed by about 40 m pinky-orange, silicified limestone.

Normal-grading, parallel lamination and/or cross-bedding and flaser-bedding are common, particularly in the coarser-grained sediments. In the most proximal successions, flute casts and cross-bedding indicate a sediment transport from south to north or from northwest to southeast in the distal sections. The tops and bases of the beds commonly show various ichnofossils (e.g., Chondrites, Thalassinoides, Helminthoida, Cosmoharphe, Phycosiphon, A. Wetzel, written communication, 2002).

Age

There are difficulties in precisely dating the base of the Lower Member because this several metres thick interval of green or grey shale contains none-to insufficiently-preserved radiolarian fauna. In the Zukayt section, the oldest datable sample (Figure 12: 19 - BR140) has a fauna assignable to the UAZ 7 of Baumgartner et al. (1995) corresponding to late Bathonian-early Callovian. Therefore, the base of the member practically coincides with the Bathonian/Callovian boundary, which is in agreement with the age of the top of the underlying Guwayza Formation. However, due to poorly-preserved radiolarian assemblages at the base of the Lower Member in many other sections the oldest sample with a datable radiolarian fauna reveals Oxfordian (Figure 2: 8 - Appendix: BR627; Figure 10: 10 - BR52; Figure 12: 17 - BR490), or even late Tithonian-earliest Berriasian such as in the Jabal Safra (Figure 2: 21) and the Kadrah Bani Dafa’a section (Figure 2: 22). In the last two sections the Lower Member of the Sid’r Formation is represented by cherty limestones in Maiolica facies with radiolarians preserved only in chert nodules or in their incompletely silicified margins (Figure 2: 21 - Appendix: BR536-552, 22 - Appendix: BR464-465). The Lower Member in radiolarian-bearing Maiolica facies was also recorded in Wadi Sid’r (Figure 2: 11 - Appendix: BR68-81) and in Wadi Nayid (Figure 14: 13 - BR84-97) where this facies reaches up to the Hauterivian as indicated by the youngest radiolarian found in the Lower Member.

Boundaries

The basal boundary of the Lower Member in section Zukayt (Figure 12: 19) is marked by an abrupt increase in silicification and a decreasing amount of clastic material, whereas in section Firq (Figure 12: 17) the Guwayza Formation grades into the Sid’r Formation with a fining- and thinning-upward of the beds, accompanied by an increase in silicification. In both sections the boundary to the overlying Upper Member is set at the distinct change from strongly silicified fine-grained radiolarian-bearing limestones and cherts to non-silicified calcarenites.

Sid’r Formation - Upper Member

Lithology and sedimentary features

The Upper Member, measuring approximately 70 m in the Firq section (Figure 12: 17), is characterised by a distinct reduction in silicification and the appearance of centimetre-to-metre-bedded, medium-grained to coarse-grained, light grey-weathered calcarenite. The calcarenites contain a high amount of reworked ooids and carbonate lithoclasts such as fawn dolomite and dark-grey coloured limestone. Common calcirudites consist of boulders of Permian(?)/Triassic reefal and lagoonal limestones, and of intraclasts (cherts, calcarenite and calcilutite). In section Zukayt (Figure 12: 19) the sequence is dominated by about 25 m of thickly bedded calcarenites and calcirudites.

The sediments generally show normal-grading, parallel lamination and/or ripple cross-bedding. Small, metre-sized erosive channels are common. Thalassinoides and Berganeria ichnofossils are frequently observed at the base of the beds (A. Wetzel, written communication, 2002).

Age

Biostratigraphic dating of the Upper Member is difficult because radiolarians are commonly missing. One sample in the section Kathmah (Figure 2: 16 - Appendix: BR727) and another in the section Musallah (Figure 2: 8 - Appendix: BR637) indicate a late Albian to early Cenomanian age. Taking into account the dating of the Lower Member and of the overlying Nayid Formation, the age of the Upper Member is considered to be Barremian to Cenomanian. The common foraminifers in the section Zukayt (Orbitolinidae, Textulariidae and large Miliolidae - Figure 12: 19 - B68, B82) also suggest an early Barremian to Cenomanian age for the Upper Member (R. Martini and L. Zaninetti, written communication, 2001).

Boundaries

In both sections (Figure 12: 17 and 19), the lower boundary of the Upper Member is marked by a distinct change from pervasively silicified limestones and radiolarian cherts to non-silicified calcarenites. The boundary to the overlying Nayid Formation is characterised by a decreasing amount of carbonate lithoclasts, accompanied by a rapid increase in silicification.

Regional variations

In most of the studied sections, the two members of the Sid’r Formation with their characteristic lithofacies are present (Figure 2: 8, 13, 16, 17, 19, 21 and 22). Typically, the Lower Member is marked by major variations in thickness, degree in silicification and amount of calcarenite/calcirudite from proximal (Figure 2: 17, 18 and 20, ≅ 100 m; 10 and 11, > 150 m) to more distal settings (Figure 2: 16 and 19, < 65 m; 8 and 21, < 55 m). Successions representing more distal facies show a fast transition from the underlying calcarenites of the Oolitic Limestone Member into a radiolarian chert, silicified mudstone- and limestone-dominated facies with shale intercalations. The more proximal facies shows a fining- and thinning-upward trend from the coarse-grained top of the Oolitic Limestone Member into the Lower Member. In these sections, a gradual increase in silification and the occurrence of radiolarian chert can be observed. Conglomerate and/or breccia beds are still common in the basal part but disappear completely up-section. The successions of the Upper Member show the same proximal to distal trend in thickness and lithofacies as the Lower Member of the Sid’r Formation. The thickness of the Upper Member varies from less than 40 m (Figure 2: 8, 13, 16, 19 and 21) to more than 80 m (Figure 8: 18,Figure 12: 17). The most proximal facies is found south of Jabal Akhdar (17 and 18), where it is characterised by a less pronounced silicification and conspicuous coarse pebble to fine-boulder-grade conglomerate and breccia, with oversized blocks in the uppermost part of the member. The calcarenites in all sections are dominated by lithoclastic material (Figure 13b), whereas the conglomerates and breccias contain mainly reworked platform detritus of Triassic/Permian? age and diverse intraclasts.

Nayid Formation

Type section

The Nayid Formation, first established by Glennie et al. (1974) in Wadi Nayid in the northwest Hamrat Ad Duru Range (Figure 2: 13), was later redefined by Béchennec (1987) and Béchennec et al. (1986, 1992) in the same area. A typical section from Wadi Nayid (13) is shown in Figure 14, exposing the contact to the underlying Sid’r Formation.

Lithology and sedimentary features

The base of the Nayid Formation is generally marked by a 10-to-15 m thick level of pinky-orange ‘fine-grained’ silicified calcarenite and radiolarian-bearing calcilutite and chert (Béchennec et al., 1993). Up-section follow c. 90 m of thinly- to medium-bedded, fine-to medium-grained, pale light brown weathering calcarenite and subordinate microconglomerate (Figure 13c). The succession is well-bedded and characterised by normally-graded, parallel laminated and/or rippled beds and partially well-preserved convolute bedding (Figure 13c). Primary structures in the upper part of the beds are commonly blurred by burrowing, mostly by Zoophycos and Chondrites (A. Wetzel, written communication, 2002).

Boundaries

The basal boundary of the Nayid Formation is characterised by the appearance of strongly silicified limestones, cherts and fine-grained calcarenites (Béchennec, 1987; Béchennec et al., 1986; Cooper, 1990; Glennie et al., 1974). The top of the Nayid Formation is generally a tectonic contact to an overlying thrust slice.

Age

Most cherts of this formation are spiculites. Tests of Radiolaria or planktonic foraminifera are scarce. However, one sample (BR654) from a radiolarian chert in section Firq (Figure 12: 17) indicates a late Turonian - early Coniacian age, and a second sample (BR100a) from the Wadi Nayid section (Figure 14: 13) reveals a Coniacian - early Santonian age. Therefore, a tentative Cenomanian-Coniacian - ?Santonian age can be assumed.

Synonymy

The Nayid Formation sensu Béchennec et al. (1992, 1993) equals to the upper part of the Nayid Formation in Glennie et al. (1974) and to the Riyamah Member (Muti Formation) of Cooper (1987).

Regional variations

The Nayid Formation is observed in a few outcrop areas only (Figure 2: 8, 13, 17, 19 and 21) and it is always incomplete, with the top missing due to tectonic contacts to overlying thrust slices. The maximum thickness of the Nayid Formation occurs at the southern end of the Jabal Akhdar (Figure 14: 17, ≅ 150 m) and in Wadi Nayid (Figure 14: 13, ≅ 100 m). The studied sections show no significant regional variations in lithofacies.

Wahrah Formation

Type section

The type section was established by Glennie et al. (1973) in the Jabal Wahrah area (Figure 2), north of the Hamrat Ad Duru Range, where the formation was subdivided into five informal members. Later workers modified the lithostratigraphic terminology of the Wahrah Formation (Figure 15). The Wahrah Formation is divided into a basal Variegated Mudstone Member and a Red Bedded Chert Member, both defined by Kickmaier and Peters (1990) and later also described by Biaggi and Steinmann (1995), and Kickmaier (1995). The ‘Lower Limestone’ of Glennie et al. (1973) has been atributed to the Guwayza Limestone Formation by Béchennec et al. (1993) and is no longer part of the Wahrah Formation (Figure 9). The ‘Upper Limestone’ or ‘Upper Member’ (Figure 15) of previous workers was not found during our investigations and should be abandoned. Typical sections in the Jabal Wahrah and Jabal Hammah are shown in Figure 16 (2 and 14).

Boundaries

The boundary between the Guwayza and Wahrah formations is characterised by an abrupt decrease in grain size and an increase in silicification. The tops of the measured sections are always thrust-controlled and characterised by strong folding respectively thrusting.

Age

Radiolarian assemblages of three intensively studied sections, namely Al Dhaby (Figure 16: 14 - BR23, 29 and BR36-51a), Qabil (Figure 16: 2 - BR387 and BR388-415), and Al Hammah Range (Figure 2: 24- Appendix: BR832-851 and BR852-862), reveal a Callovian to Kimmeridgian age for the Variegated Mudstone Member and a Tithonian to late Barremian/early Aptian age for the Red Bedded Chert Member. Because of the truncated top the first (14) and the last (24) of the above-mentioned sections end up tectonically in the Berriasian, and the middle (2) in the late Barremian/early Aptian (Aurisaturnalis carinatus perforatus subzone of Dumitrica et al., 1997).

Wahrah Formation - Variegated Mudstone Member

Lithology and sedimentary features

The Variegated Mudstone Member contains up to 30 m of lilac to brownish, thinly-bedded, siliceous mudstone, radiolarian-bearing calcilutite and some radiolarian chert and silicified limestone (Figure 16: 2 and 14). Calcarenites are also common (Figure 16: 2). Up-section, beige/orange coloured, centimetre-bedded, strongly silicified lime- and mudstone and chert dominate the sequence. The sediments are characterised by parallel lamination and/or rare cross-bedding and flaser structures. Primary sedimentary structures are partially modified by bioturbation.

Boundaries

The contact between the Variegated Mudstone Member and Red Bedded Chert Member is gradational and is arbitrarily set at the level with mainly well-bedded red radiolarian chert.

Synonymy

The Variegated Mudstone Member corresponds to the Mudstone Member established by Glennie et al. (1973) and to the lowermost part of the Wahrah Chert respectively of the Lower Member established by Béchennec (1987) and Béchennec et al. (1990) as shown in Figure 15.

Wahrah Formation - Red Bedded Chert Member

Lithology and sedimentary features

This member consists of characteristic ribbon cherts with thinly-bedded, red-brown radiolarian chert layers alternating with red, siliceous shale beds (Figure 13d). In the Qabil section (Figure 16: 2) a c. 5-10-m-thick succession of strongly silicified calcarenite is observed in the middle part of the member. Up-section, manganese is enriched and forms up to 60 cm thick black coloured levels (Figure 16: 14). Most of the chert beds can be traced laterally over several tens of metres before they wedge out. Some individual layers are characterised by large chert nodules or lenses. Parallel to wavy lamination and flaser structures are common. The chert beds are commonly strongly bioturbated by Chondrites and other unidentified sediment dwelling organisms.

Synonymy

The Red Bedded Chert Member corresponds to the ‘Upper Chert’ of Glennie et al. (1973), the ‘Wahrah Chert’ of Béchennec (1987) and Béchennec et al. (1990) and the Lower Member of Béchennec et al. (1993) as shown in Figure 15.

Regional variations

The Wahrah Formation represents the most distal Late Jurassic to Early Cretaceous lithofacies of the Hamrat Duru Basin and is coeval to the Sid’r Formation (Figure 3). The top of the succession is always marked by a tectonic contact to the overlying thrust slice, therefore the measured sections are never complete. Lateral variations, mainly restricted to the Variegated Mudstone Member, comprise differences in the degree of silification and marked changes in thickness from e.g. 25 m in section 2 to ca. 15 m in section 14 (Figure 16). It appears that the mangenese enrichments get more important from the western to the eastern outcrop areas.

STRATIGRAPHIC ARCHITECTURE

The new biostratigraphic framework allows for a correlation of time-equivalent facies throughout the Hamrat Duru Basin. The correlation of the described sections and their lateral and vertical facies relationships record the complex stratigraphic evolution of a passive margin through time and space (Figure 17). The Hamrat Duru Group represents a vertically mixed carbonate/siliciclastic system punctuated by two phases of high radiolarian productivity and siliceous sedimentation. The six formations of the Hamrat Duru Group are in most cases separated from each other by rapid vertical changes in lithofacies. With the exception of the paraconformal Al Ayn - Guwayza Formation boundary, the vertical contacts between the lithostratigraphic units are conformable and most of the boundaries are variously sharp or gradual. Within the limits of biostratigraphic resolution the formations and members of the Hamrat Duru Group are isochronous with the exception of the base of the Nayid Formation which is time-trangressive (Figure 17).

Independent from tectonically induced local variations, the thickness of most units decreases markedly from proximal to distal settings for most of the units within one continuous outcrop area (Figure 17). For example, the Guwayza Formation and the Upper Member of the Sid’r Formation show a general thinning from southwest to northeast, as shown in Figure 17. Furthermore, the Lower Member of the Sid’r Formation shows increasing silicification of the limestones and greater abundance of radiolarian chert and again a general thinning from southwest to northeast towards more distal positions, where radiolarian cherts become volumetrically important (Figure 17: serial section B and C).

DISCUSSION

Depositional Environment

The sedimentary rocks of the Hamrat Duru Group represent base-of-slope to abyssal plain sedimentary facies that accumulated in the Hamrat Duru sub-basin (Glennie et al., 1974; Murris, 1981; Cooper, 1986; Watts and Blome, 1990). Generally, the sedimentological features show that the whole succession is mainly represented by mass flow deposits such as turbidites and debris flows which originated from the nearby Arabian Platform and/or platform margin, and from the platform hinterland, by shedding of reworked carbonate and terrigenous clastic material.

Depositional Systems

Three different types of depositional systems are developed in the Hamrat Duru Basin: (1) siliciclastic submarine fan system; (2) a carbonate submarine fan system; and (3) a radiolarian chert system. The siliciclastic and carbonate submarine fan systems show different fan geometries as described below. In the proximal facies, flute casts and current ripples indicate northerly sediment transport, whereas in the distal settings the transport direction is towards the east or southeast. These trends in the palaeocurrent directions together with the lithofacies pattern shown in Figure 17 suggest a NW-orientated basin axis, particularly from the Middle Jurassic to the Early Cretaceous. Sediment supply and dispersal mechanisms in the siliciclastic and carbonate systems were controlled by submarine sediment-gravity flows. The carbonates are dominated by reworked shallow-water material such as ooids, peloids, bioclasts and carbonate lithoclasts from the adjacent Arabian Platform. The Triassic and Jurassic terrigenous clastics were derived from metamorphic and/or sedimentary basement rocks in the hinterland of the carbonate producing areas. In addition, oceanic build-ups such as seamounts and/or isolated platforms related to the faulted continental margin also shed material, representing an exotic carbonate facies (e.g. Permian reef limestone, Triassic Hallstatt facies; Hutin et al., 1986; Tozer and Calon, 1990) into the Hamrat Duru Basin. The petrographic composition of the siliciclastic sandstones reflects detritus derived from sediments generated from a stable continental basement and transported to a passive continental margin (craton interior and transitional continental after Dickinson, 1985; or TE-composition after Yerino and Maynard, 1984). Successions dominated by siliceous sedimentation such as radiolarian chert and silicified limestone are attributed to raised calcite compensation depths associated with high sea-levels, decreased clastic input and high radiolarian productivity.

The siliciclastic deep-sea fan system is well documented in the Al Ayn Formation. It is quartz sanddominated in at least two local areas (Hawasina Window and Wadi Al Ayn area, Figure 2) separated by regions with mixed carbonate/siliciclastic deposits. This regional facies distribution and the sand/shale ratios suggest a canyon-fed point source in each case. It can be described by the classical submarine fan model with turbidite successions (Mutti and Ricci Lucchi, 1972). The detritus that built up the siliciclastic fans bypassed the shelf, whereas mixing of siliclastic and carbonate components occurred on the carbonate platform or ramp prior to their deposition on a mixed fan system (Figure 18a). In the proximal fan areas, channelled and amalgamated sandstones and conglomerates are found (e.g. southern Hamrat ad Duru Range, section 10). Coarsening-up sandstone lobe sequences of the middle fan pass vertically and laterally into a shale/siltstone alternation of the basin plain.

The carbonate deep-sea fan system is best represented by the Oolitic Limestone Member of the Guwayza Formation. In the proximal outcrops it is developed in a calcarenite-rich facies with massive amalgamated, laterally continuous, sheet-like high density turbidite beds and debrites, alternating with a calcilutite-rich facies. Major channel systems are not developed. Both facies are interrupted by massive laterally extensive mega-conglomeratic debrites that are thought to have been generated by tsunami waves (Blechschmidt, 2002). The more distal facies of the carbonate deep-sea fan system is characterised by a distinct decrease in grain size and bed thickness compared to the proximal sequences. This facies shows coarsening-up calciturbidite and calcilutite lobe sequences which pass vertically into a mudstone/chert alternation of the basin plain.

Generally, the proximal to distal decrease in bed thickness and grain size combined with the orientation of palaeocurrents indicate numerous sediment sources along the platform edge located to the south and southwest of the Hamrat Duru depocentre (Cooper, 1989). The carbonate deep-marine fan system is controlled by sediment gravity flows which bypassed the upper slope to form sheet-like sediment aprons passing basinward into elongated fan complexes (Figure18b) (Eberli, 1991; Stow, 1992). This is supported by the palaeocurrent directions indicating transport mainly to the north in the proximal apron facies and turning to the southeast in the distal facies following the basin axis.

The radiolarian chert system is represented by two distinct depositional phases of dominantly siliceous sediments. The older one corresponds to the late Anisian-early Norian, the younger started in the late Pliensbachian or early Toarcian and lasted, with some interruptions, until the Coniacian.

The late Anisian-early Norian phase corresponds to the Radiolarian Chert Member of the Zulla Formation and represents an interval of practically uninterrupted pelagic siliceous sedimentation. Its onset was gradational and started as short productive intervals during a predominantly shaly phase in the upper part of the Sandstone and Shale Member of the Zulla Formation. With time these high productivity intervals became more and more frequent during the late Anisian and dominated the sedimentation pattern at the beginning of the Ladinian. In the Ladinian and early - middle Carnian the colour of the radiolarian cherts is usually red and silicification complete. The colour of the radiolarian cherts and shales gradually changes to grey-green in the middle Carnian to early Norian part as the degree of silicification decreases. In Wadi Al Ayn (e.g. Figure 2: 4, 5) the red colour of the rocks has almost disappeared in favour of green. In Wadi Bani Khalid (Figure 2: 26), however, red-coloured radiolarites and shales reappear at some intervals in the Carnian.

The transition to the overlying Halobia Limestone Member is gradational. It is marked by an increasing percentage of limestone beds or calcium carbonate in the silicified beds, a decrease of the preservation of the radiolarian tests, and a decreasing number of recognizable radiolarian tests. This suggests a decrease in radiolarian productivity and upwelling activity, and a drop of the calcite compensation depth (CCD).

The practically synchronous onset and disappearance of the radiolarian sedimentation in the Zulla Formation and the almost general change in colour in the entire study area suggest deposition of the Radiolarian Chert Member in a rather uniform basin with similar palaeoceanographic conditions. The exceptions in the general trend from red to green colours mentioned above (sections: 5, 24) might be related to submarine currents; since red-bedded cherts were sedimented in oxic conditions with stronger bottom currents, and green or grey cherts in relatively stagnant conditions with weak bottom currents (Douzen and Ishiga, 1993) colour reflects primarily the palaeoenvironment and is of only limited biostratigraphic value. The development of the radiolarian chert facies is most probably related to an intense upwelling activity (De Wever, 1988; De Wever and Thiébault, 1981; De Wever et al., 1995) and a reduced carbonate supply. During the Triassic the Hawasina Basin was part of the Neo-Tethys Ocean which was open towards the east. This general geometry is assumed to have resulted in a clockwise oceanic gyre like the one present today in the North Pacific, and promoted a strong upwelling activity (De Wever and Thiébault, 1981).

Hemipelagic siliceous productivity in the whole Hawasina Basin ceased between the early Norian and late Pliensbachian. The carbonate and subsequently the siliciclastic deposits of this interval suggest a shallowing of the basin and changes in the circulation patterns related to a much wider Neo-Tethys Ocean at that time (Stampfli et al., 2001). The siliceous beds occurring in this interval are represented only by spiculites with large sponge spicules, typical for a still deep but more proximal setting and indicating reworking by submarine currents.

Siliceous hemipelagic sedimentation and the upwelling activity started again in the late Pliensbachian when the Hamrat Duru Basin deepened again. In agreement with the global context, the sea floor was commonly poorly oxygenated during the Early and Middle Jurassic. As a result, almost all radiolarian rocks deposited during this time interval are green or grey in colour. There are only two local occurrences of red cherts, one in the late Pliensbachian-early Toracian of Qabil (2) and another one in the Bajocian of the Jabal Safra (21).

The hemipelagic sedimentation was temporarily interrupted by the input of mostly reworked shallow-water carbonate material during the deposition of the Oolitic Limestone Member. Carbonate input decreased rapidly or ceased during the Callovian with the reinstallation of upwelling conditions suggested by the lithology and biogenic contents of the Wahrah and Sid’r formations.

The Red Bedded Chert Member of the Wahrah Formation contains abundant radiolarians and few, small sponge spicules which is typical for a distal, pelagic facies. In contrast, the cherty limestone of the Lower Member of the Sid’r Formation usually contains abundant, large sponge spicules and radiolarians. This assemblage is characteristic of shallower waters, for example plateau sediments or sediments deposited on the continental slope. The facies of the Lower Member of the Sid’r Formation and the preservation of radiolarians in slightly silicified layers or in chert nodules strongly resemble the Maiolica limestone from the Southern Alps in northern Italy (Lombardian Basin) and from many other parts of the Neo-Tethys Ocean (Wieczorek, 1988). This implies similar palaeoceanographic conditions throughout the Neo-Tethys Ocean.

Taking into account the abundance of radiolarians and the frequency of chert beds, the climax of upwelling occurred in the late Tithonian-Berriasian. This is the time interval of maximum development of the red radiolarian cherts of the Wahrah Formation and of the silicified Maiolica-type limestones of the Lower Member of the Sid’r Formation representing resedimented periplatform oozes which possibly form small turbidite fans (Figure 18c). The radiolarian cherts and shales of the Wahrah Formation are true pelagites with minor evidence of currents. The radiolarian sedimentation in the Hamrat Duru Basin continued into the Barremian when another maximum of radiolarian productivity occurred. During the remaining time of the early Cretaceous and during the late Cretaceous, radiolarian productivity was less pronounced and was restricted to some short intervals, recorded in thin radiolarian-bearing silicified beds. In the Nayid Formation, the most frequent if not exclusive siliceous components are large sponge spicules suggesting a rather proximal environment and strong transport currents.

TECTONOSTRATIGRAPHIC AND BATHYMETRIC INTERPRETATION

Cooper (1986, 1990) concluded that the sedimentary characteristics of the Hamrat Duru successions reflect relative sea-level fluctuations, with significant carbonate input in the deep-marine basin during periods of platform flooding and high carbonate production on the stable platforms. Changes from high to low stands of relative sea level were accompanied by a significant reduction in carbonate production and increased input of siliciclastic sediments. Raised calcite compensation depths associated with high sea levels resulted in the deposition of siliceous sediments. During periods of low sea level, terrigenous clastics prograded across or by-passed the platform into the Hamrat Duru Basin.

A simplified comparison of the Mesozoic Arabian Plate sequence and the deep-marine sequences of the Hamrat Duru Basin and Batain Basin with the proposed standard curve (Haq et al., 1987; Vail et al., 1977, 1991) is shown in Figure 19. At this scale, a broad relationship between the long-term, sea-level cycles (second order: 3-50 My, Vail et al., 1991) and the evolutionary trends of the Mesozoic megasequences of the Arabian Platform and the Hamrat Duru Basin is clearly recognisable. The similar evolution of the successions of the Hamrat Duru Group in different outcrop belts points to a eustatic control of facies patterns.

Triassic Evolution (Zulla Formation, Al Ayn Formation)

The Early Triassic (Olenekian) dominance of carbonate material in the Hamrat Duru Basin (Limestone and Shale Member) is related to the presence of a coeval Arabian carbonate shelf which was already established by the Late Permian (Murris, 1980; Le Métour et al., 1995). Carbonate sedimentation ended and was replaced by the deposition of siliciclastics in the late Olenekian (Sandstone and Shale Member). The nearly coeval turnover (within biostratigraphic resolution) in different outcrop belts (Figure 2: Hawasina Window, Wadi Al Ayn, Wadi Bani Khalid) indicates an external control factor such as eustatic variation. The relatively small volume of mostly fine-grained, well-sorted sandstone can be related to a prograding delta complex during a period of rising sea-level and hinterland uplift. According to Bernoulli et al. (1990), the supply of siliciclastics might be connected to an Anisian sea-level drop during a third-order cycle (Figure 19). In the latest Anisian to earliest Norian interval, a continuous relative sea-level rise led to a deepening of the basin, reflected by the deposition of the Radiolarian Chert Member (Figure 19). The return to carbonate deposition (Halobia Limestone Member) during the early to middle Norian signals a deepening of the CCD related to a change in phyto- and zooplankton productivity and/or an increased supply of periplatform material (Bernoulli et al., 1990).

In comparison, the Triassic sequences of the Batain Basin (Sal Formation) (Immenhauser et al., 1998; Hauser, 2001; Hauser et al., 2001, 2002) and Hamrat Duru Basin (Zulla Formation) show a different lithostratigraphic development (Figure 19). The Sal Formation is subdivided in three lithostratigraphic members including from base to top: the Mudstone Member (late Olenekian to middle Anisian), the Chert Member (late Anisian) and the Calcarenite Member (Ladinian to Norian). In contrast to the Zulla Formations, carbonates are more abundant in the Sal Formation and the Anisian sandstone facies is completely missing. However, cherts are also common in the Sal Formation and radiolarians extracted from these rocks reveal a late Anisian to middle Norian age (Hauser et al., 2001), representing the same time interval of radiolarite deposition in both, the Sal and Zulla formation. The general time-equivalent lithostratigraphic trends of both formations (i.e., Early Triassic limestone and mudstone sedimentation, late Anisian to early Norian occurrence of radiolarian chert, early Norian Halobia-bearing carbonate) therefore indicate a close relationship between the evolution of the Arabian Platform (Figure 19; Glennie et al., 1974; Le Métour et al., 1995) and slope (Maqam Formation of the Sumeini Group; Watts and Garrison, 1986) and its two adjacent deep-marine basins in Oman. These trends may be related to global features, including sea-level variations and circulation patterns in the southern Neo-Tethys.

The Al Ayn Formation, deposited during the latest Triassic, is possibly related to a global sea-level fall during a second order cycle (Figure 19) starting already during the deposition of the mixed siliciclastic/carbonate top portion of the Zulla Formation. This sea-level drop is also recorded by the occurrence of a coeval fluvial and coastal sandstone sequence on the Arabian Platform (Minjur Formation, Figure 19; Murris, 1980). A distinct stratigraphic gap of several million years in the early Liassic in the Wadi Saal section (Figure 6: 10) corresponds to a major sea-level lowstand around the Triassic-Jurassic boundary evident also in the carbonate platform of the northern Oman Mountains (Murris, 1980; Haq et al., 1987).

Jurassic and Cretaceous Evolution (Guwayza, Sid’r, Nayid formations)

The lithologic trend of the Early to Middle Jurassic Tawi Sadh Member of the Guwayza Formation is related to a gradual Jurassic sea-level rise mirrored by the stratigraphic evolution of the Arabian Platform (Figure 19). The shale and/or chert-dominated facies at the base of this member succeeded by a carbonate-producing system corresponds to the evolution of the Arabian shelf during flooding. This general trend is interrupted locally by the input of siliciclastics occurring in the upper part of this member below the Oolitic Limestone Member of the Guwayza Formation. This led to distinct lateral changes in facies and thickness of the Tawi Sadh Member. The highly variable amount of reworked platform material in this sandstone facies is attributed to prograding siliciclastics crossing the carbonate shelf. This resulted in mostly mixed sequences with either alternating siliciclastic and carbonate beds, or beds with mixed carbonate and siliciclastic components. In addition, the occurrence of slumping, massflows with large oversized intraclasts including oolitic calcarenite and calcilutite boulders in the most proximal sections and clastic dykes in the more distal sections, mark a tectonically active phase within the earliest Middle Jurassic passive margin history. The accumulation of the deep-marine Oolitic Limestone Member from the middle Bajocian to the early Callovian is directly related to the Jurassic sea-level rise and highstand system in a second-order cycle and corresponds to the growth of a stable Arabian carbonate shelf in Oman (Figure 19: Dhruma Formation, Murris, 1981; Sharland et al., 2001). The occurrence of mega-conglomerates, olistoliths and slump-controlled debris sheets in the proximal Hamrat Duru sections indicates tectonic activity leading to the collapse of the platform margin and/or fault-bounded highs in the basin (Tozer and Calon, 1990; Watts and Garrison, 1986). The Jurassic to Cretaceous slope deposits of the Mayhah Formation (Sumeini Group), which are also characterised by huge mass movements, reveal depositional conditions similar to those of the Oolitic Limestone Member of the Guwayza Formation (Watts and Blome, 1990). Strong tectonic activity during the Middle Jurassic led to a basin reorganisation recorded in the development of a distinctly NW-striking basin axis and a change in palaeocurrent directions from dominantly northwards to southeastwards in the distal facies. Occurrence of distinct internal cycles measuring up to several tens of metres in the Oolitic limestone Member (see also tripartite system by Cooper, 1989, 1990) are possibly related to relative sea-level variations of higher frequency (i.e., third order, 0.5 - 3 My, Vail et al., 1991). Furthermore, storm and/or tsunami controlled events also caused clastic inputs into the Hamrat Duru Basin during that time (Blechschmidt, 2002).

In the Batain Basin, the sedimentation of calcareous sandstone and terrigenous shale (Sandstone Member) during the latest Triassic and that of the sandy Guwayza Formation during the Early Jurassic indicates a similar evolution to that of the Al Ayn and Guwayza formations (Hauser, 2001; Hauser et al., 2001, Figure 19).

Thus, the sedimentary sequences record two main extensional tectonic phases (Le Métour et al., 1995): (1) the Permian phase which caused the break-up of northeastern Gondwana and the formation of the Arabian Platform and the Hamrat Duru Basin, and (2) the Late Triassic tectonic phase which caused major volcanic activity in the distal zones and the formation of new morphostructures including the Umar Basin. The Jurassic has been seen as a time of a relative stable, passive-margin phase without significant tectonic activity (Le Métour et al., 1995). According to these authors, sedimentation during the Jurassic was predominately controlled by eustatic changes with the development of a vast carbonate platform during the main Early Jurassic sea-level rise. The new data shown here, however, suggest that the “relatively stable” evolution (Le Métour et al., 1995) of the Jurassic was interrupted by distinct phases of tectonic instability with uplift and erosion of the platform, block faulting and increased subsidence which caused deposition of conglomerates and olistoliths at the base of the slope (Figure 20). Furthermore, slope and platform instability during this time led to a reorganisation of the Hamrat Duru Basin geometry. Following the Middle Jurassic sea-level highstand the Callovian/Oxfordian time is marked by a distinct drop in sea-level which resulted in reduced carbonate production on the Arabian Platform, locally marked by breaks in sedimentation (Figure 19 and Le Métour et al., 1995). In the Hamrat Duru Basin the Callovian/Oxfordian sea-level fall is recorded as an abrupt decrease of resedimented ooids, greater abundance of radialorian chert and spiculites as well as locally by the input of lithoclastic platform material (Sid’r and Wahrah formations).

In general, the Early to Middle Jurassic sediments of the Batain Basin reveal a similar evolution to that of the Hamrat Duru Basin with siliciclastic influx (uppermost Sal Formation/lower Guwayza Formation) and ooid-dominated upper Guwayza Formation with levels of radiolarian cherts of Middle Jurassic age (Hauser et al., 2001, 2002; Peters et al., 2001). Sea-level rise during the Late Jurassic-Early Cretaceous (Figure 19) and increased tectonic subsidence (Tithonian-Berriasian) led to a deepening of the Hamrat Duru Basin and also caused drowning of the Arabian Platform (Béchennec et al., 1990; Cooper, 1990; Le Métour et al., 1995). This resulted in decreased carbonate production and deposition of a Maiolica-facies on the Arabian Platform (Le Métour et al., 1995) and in the proximal Hamrat Duru Basin (Lower Member of Sid’r Formation) as well as in the formation of radiolarian chert in the distal part of the Hamrat Duru Basin (Wahrah Formation).

Both the Late Jurassic to Cretaceous radiolarian ribbon cherts of the Wahrah Formation of the Batain Group (Peters et al., 2001) and of the Wahrah Formation and Lower Member of the Sid’r Formation of the Hamrat Duru Group suggest an important palaeoceanographic turnover which led to a Tethyan-wide change from calcareous deposition to a radiolarian chert and/or silicified limestone-dominated facies. An Hauterivian-Barremian sea-level fall led to a re-establishment of the carbonate platform and/or ramp environments in the formerly drowned areas and increased the export of re-deposited platform material (Upper Member of the Sid’r Formation) into the Hamrat Duru Basin (Le Métour et al., 1995). Similarly, on the continental slope, siliceous pelagic lithologies are overlain by calcarenite and calcirudite made of reworked Arabian Platform material deposited during this time span (Sumeini Group, Huwar Formation, Le Métour et al., 1995). A final steepening of the slope and increased basin subsidence resulted from the approach toward a north-dipping subduction zone (Robertson, 1987; Watts and Blome, 1990) possibly connected to an Albian-Cenomanian eustatic sea-level rise (Figure 19). This may have resulted in the accumulation of the mostly fine-grained, partially silicified limestone and chert at the base of the Nayid Formation. The high amount of large sponge spicules suggests a rather proximal slope environment for the Nayid Formation.

CONCLUSIONS

(1) The Mesozoic base-of-slope to basin plain deposits of the Hamrat Duru Group of the Oman Mountains are subdivided into six formations, separated from each other mostly by a rapid vertical change in lithofacies. New biostratigraphic data led to a more precise dating of these lithostratigraphic units of the Mesozoic Hamrat Duru sediments compared to previous studies. Moreover, the new biostratigraphic framework better discriminates time-equivalent facies belts throughout the Hamrat Duru Basin. This work forms the basis for forthcoming studies of the deposits of the southern Tethyan margin in Oman. A next step might be an improved time-stratigraphic correlation with the Arabian Platform sequence. (2) The Hamrat Duru Group represents a mixed carbonate/siliciclastic system punctuated by two distinct phases of high radiolarian productivity (late Anisian to early Norian and late Pliensbachian to Coniacian). Sedimentological features within the individual successions show that the dominating sedimentary processes were mass flows such as turbidity currents and debris flows originating from the nearby platform margin. The Hamrat Duru Basin was controlled by various types of submarine fan systems at the base-of-slope and the abyssal plain which are related to a complex passive margin evolution. (3) The Hamrat Duru megasequence also reflects sea-level changes relative to the Arabian Platform. A direct correlation between the proposed long-term cycles of global sea-level change (first order: 50+ My and second order: 3 - 50 My, Vail et al., 1991) on the evolution of the base-of-slope and abyssal plain deposits of the Hamrat Duru Basin is evident. (4) Increasing abundance of radiolarian chert and radiolarian-bearing silicified limestone records higher surface-water productivity that is possibly related to changes in palaeoceanographic circulation patterns. It is proposed that such changes in surface productivity caused basin internal lateral variations in shale and/or radiolarian chert distribution. (5) Besides the two main extensional phases (Permian and Late Triassic) which are extensively discussed in Le Métour et al. (1995), the Middle Jurassic of the Hamrat Duru Basin also records tectonic activity which finally led to the development of a distinctly NW-oriented basin axis and a change in palaeocurrent directions from dominantly northwards to southeastwards in the distal facies associated with the deposition of conglomerates, olistoliths and slumps. (6) The northern (Hamrat Duru Group) and eastern (Batain Group) Oman palaeomargins show a similar sedimentary evolution that is mainly related to Tethyan-wide palaeoceanographic changes and the processes acting on the Arabian Platform. Lithological differences between the Hamrat Duru and the Batain Group are restricted to the Triassic. During this time interval the Batain Group (Sal Formation) was dominated by carbonate deposition, and a sandstone facies is completely missing. In contrast, the coeval Zulla Formation of the Hamrat Duru Group is characterised by turbiditic sandstones, less carbonate and abundant radiolarian chert. From Late Triassic onward both basins show a comparable sedimentary evolution which continued up to the Early Cretaceous. Since the Late Jurassic the facies pattern of both basins was identical and reflects the climax of the oceanisation process of Oman’s passive palaeomargins.

ACKNOWLEDGEMENTS

The present paper is a result of a geological research program of the University of Bern supported by the Swiss National Science Foundation (project No. 2000-050681). L. Krystyn was sponsored by the Austrian National Committee for IGCP (proj. 467 Triassic Time). The authors thank the Ministry of Commerce and Industry, Sultanate of Oman, especially Dr. Hilal Al Azri, Director General of Minerals, for his hospitality and for logistic support during field work. Henk Droste and Adrian Immenhauser are thanked for helpful reviews that greatly improved the manuscript. The design and drafting of the final graphics was by Gulf Petrolink.

APPENDIX

Overview of the radiolarian assemblages and their age mentioned in this contribution. A complete list may be ordered from the corresponding author.

Radiolarian assemblage

Sample No. BR20

UTM Coordinates 526238/2515183

Age : Late Bajocian-Early

Bathonian

Angulobracchia digitata Baumgartner

Leugeo aff. parvispinatus Hull

Levileugeo ordinarius Yang and Wang

Palinandromeda depressa (De Wever and Miconnet)

Palinandromeda praecrassa (Baumgartner)

P. sognoensis Baumgartner

Paronaella aff. kotura Baumgartner

Parahsuum aff. natorense (El Kadiri)

Paronaella aff. mulleri Pessagno

Podobursa aff. helvetica (Rüst)

Teichertus aff. notus Hull

Tetraditryma corralitosensis (Pessagno)

T. pseudoplena Baumgartner

Sample No. BR23

UTM Coordinates 526238/2515183

Age: Early-Middle Oxfordian

Angulobracchia biordinalis Ozvoldova

Bistarkum femur (Li)

Cinguloturris carpatica Dumitrica

Dicerosaturnalis angustus (Baumgartner)

Emiluvia orea Baumgartner

E. sedecimporata (Rüst)

Eucyrtidiellum takemurai Hull

Hexasaturnalis aff. suboblongus (Yao)

Higumastra inflata Baumgartner

Homoeoparonaella argolidensis Baumgartner

Obesacapsula morroensis Pessagno

Pterotrabs arcubalista Dumitrica, Baumgartner and Gorican

Ristola altissima (Rüst)

Tethysetta mashitaensis (Mizutani)

Transhsuum brevicostatum (Ozvoldova)

Triactoma blakei Pessagno

Tritrabs casmaliaensis (Pessagno)

T. ewingi (Pessagno)

Sample No. BR29

UTM Coordinates 526238/2515183

Age: Early Kimmeridgian

Acastea cf. diaphorogona (Foreman)

Angulobracchia biordinalis Ozvoldova

Archaeodictyomitra minoensis (Mizutani)

Cinguloturris carpatica Dumitrica

Dicerosaturnalis angustus (Baumgartner)

D. trizonalis (Rüst)

Ditrabs sansalvadorensis (Pessagno)

Emiluvia chica Foreman

E. ordinaria Ozvoldova

E. pentaporata Steiger and Steiger

E. salensis Pessagno

E. sedecimporata (Rüst)

E. ultima Baumgartner and Dumitrica

Eucyrtidiellum ptyctum (Riedel and Sanfilippo)

Haliodictya (?) antiqua (Rüst)

Higumastra coronaria Ozvoldova

H. aff. gratiosa Baumgartner

H. imbricata (Ozvoldova)

Homoeoparonaella argolidensis Baumgartner

Loopus aff. primitivus (Matsuoka and Yao)

Mirifusus dianae (Karrer)

Napora lospensis Pessagno

Palinandromeda cf. crassa (Baumgartner)

Paronaella kotura Baumgartner

Paronaella mulleri Pessagno

Parvivacca blomei Pessagno and Yang

Perispyridium ordinarium (Pessagno)

Podobursa polyacantha (Fischli)

P. spinosa (Ozvoldova)

Podocapsa aff. foremanae Yang

Praeconosphaera cf. sphaeroconus (Rüst)

Protunuma costatus (Heitzer)

Ristola altissima (Rüst)

Sethocapsa tripes Yang

Spongocapsula palmerae Pessagno

Svinitzium okamurai (Mizutani)

Syringocapsa spinellifera Baumgartner

Teichertus catenarius (Ozvoldova)

Tethysetta mashitaensis (Mizutani)

Tetraditryma pseudoplena Baumgartner

Tetratrabs zealis (Ozvoldova)

Triactoma blakei Pessagno

T. foremanae Muzavor

Tetratrabs bulbosa Baumgartner

Tritrabs casmaliaensis (Pessagno)

T. exotica (Pessagno)

Zhamoidellum ovum Dumitrica

Sample No. BR36

UTM Coordinates 526238/2515183

Age: Late Tithonian

Archaeodictyomitra apiarium (Rüst)

Dicerosaturnalis dicranacanthos (Squinabol)

Emiluvia chica Foreman

Eucyrtidiellum pyramis (Aita)

Loopus yangi Dumitrica

Mirifusus dianae (Karrer)

Obesacapsula cetia (Foreman)

O. morroensis Pessagno

O. polyedra Steiger

Podocapsa amphitreptera Foreman

Protunuma costatus (Heitzer)

Pseudodictyomitra leptoconica (Foreman)

Pyramispongia barmsteinensis (Steiger)

Ristola cretacea (Baumgartner)

Spongocapsula banala (Jud)

Stichomitra doliolum Aita

Sample No. BR51a

UTM Coordinates 526238/2515183

Age: Berriasian

Acaeniotyle umbilicata (Rüst)

Acanthocircus furiosus Jud

Alievium regulare (Wu and Li)

Archaeodictyomitra apiarium (Rüst)

A. excellens (Tan)

A. minoensis (Mizutani)

A. tumandae Dumitrica

Archaeospongoprunum patricki Jud

Becus triangulocentrum Dumitrica

Deviatus diamphidius (Foreman)

Dicerosaturnalis dicranacanthos (Squinabol)

D. longispinosus (Donofrio and Mostler)

Ditrabs sansalvadorensis (Pessagno)

Emiluvia chica Foreman

E. pessagnoi Foreman

Hiscocapsa grutterinki (Tan)

Loopus yangi Dumitrica

Mirifusus dianae (Karrer)

Obesacapsula bullata Steiger

Pantanellium aduncum (Parona)

P. squinaboli (Tan)

P. tredecimporatum (Rüst)

Parapodocapsa furcata Steiger

Phalangites acus (Jud)

Praecaneta cosmoconica (Foreman)

Pseudodictyomitra carpatica (Lozynyak)

Pseudoeucyrtis tenuis (Rüst)

Pseudoxitus omanensis Dumitrica

Sethocapsa leiostraca Foreman

S. zweilii Jud

S. uterculus (Parona)

Spongosaturnalis breviaculeatus Donofrio and Mostler

Suna echiodes (Foreman)

Svinitzium depressum (Baumgartner)

Tethysetta boesii (Parona)

T. mashitaensis (Mizutani)

Tritrabs ewingi (Pessagno)

Sample No. BR52

UTM Coordinates 489020/2524022 Age: Oxfordian

Angulobracchia digitata Baumgartner

Archaeospongoprunum imlayi Pessagno

Emiluvia premyogii Baumgartner

E. salensis Pessagno

Eucyrtidiellum ptyctum (Riedel and Sanfilippo)

Hexasaturnalis minor (Baumgartner)

H. aff. suboblongus (Yao)

Higumastra imbricata Ozvoldova

Mictyoditra decora (Rüst)

Napora deweveri Baumgartner

Podobursa helvetica (Rüst)

P. rosea Hull

Pseudocrucella sanfilippoae (Pessagno)

Pseudoeucyrtis firmus Hull

Tetraditryma corralitosensis (Pessagno)

Transhsuum brevicostatum (Ozvoldova)

T. maxwelli (Pessagno)

Tripocyclia jonesi Pessagno

Tritrabs casmaliaensis (Pessagno)

Zanola cornuta (Baumgartner)

Sample No. BR68

UTM Coordinates 501605/2499923

Age: Late Beriassian

Acanthocircus furiosus Jud

Angulobracchia portmanni Baumgartner

Becus triangulocentrum Dumitrica

Bistarkum irazuense (Aita)

Crolanium bipodium (Parona)

Cyclastrum rarum Squinabol

Deviatus diamphidius (Foreman)

Dicerosaturnalis dicranacanthos (Squinabol)

D. longispinosus (Donofrio and Mostler)

Dicroa periosa Foreman

Ditrabs sansalvadorensis (Pessagno)

Emiluvia chica Foreman

E. pessagnoi Foreman

Fluegellium symmetricum Steiger and Steiger

Hsuum feliforme Jud

Milax adrianae Jud

Pantanellium squinaboli (Tan)

Paronaella tubulata Steiger

Podobursa aff. quadriaculeata (Steiger)

Podocapsa amphitreptera Foreman

Pseudoaulophacus (?) pauliani Jud

Pseudocrucella (?) elisabethae (Rüst)

Pseudoeucyrtis sceptrum Jud

P. tenuis (Rüst)

Spongosaturnalis minispineus Yang

Spongosaturninus minimus (Squinabol)

Svinitzium compressum (Baumgartner)

Tritrabs ewingi (Pessagno)

T. exotica (Pessagno

Sample No. BR69

UTM Coordinates 501605/2499923

Age: Late Berriasian-early Valanginian

Acaeniotyle umbilicata (Rüst)

Acanthocircus furiosus Jud

Acaseta diaphorogona (Foreman)

Acastea (?) glebulosa (Foreman)

Alievium regulare (Wu and Li)

Angulobracchia portmanni Baumgartner

Archaeotritrabs gracilis Steiger

Crucella collina Jud

Cyclastrum rarum Squinabol

C. trigonum (Rüst)

Deviatus diamphidius (Foreman)

Dicerosaturnalis dicranacanthos (Squinabol)

Dicroa periosa Foreman

Emiluvia chica Foreman

E. pessagnoi Foreman

Fluegellium symmetricum Steiger and Steiger

Halesium biscutum Jud

Homoeoparonaella peteri Jud

Hsuum arabicum Dumitrica

H. mclaughlini Pessagno and Blome

Katroma milloti Schaaf

Pantanellium squinaboli (Tan)

Paronaella trifoliacea Ozvoldova

P. tubulata Steiger

Phalangites acus (Jud)

Savaryella guexi Jud

Spongosaturnalis breviaculeatus (Donofrio and Mostler)

S. aff. multidentatus (Squinabol)

Stichocapsa pulchella (Rüst)

Suna echiodes (Foreman)

Syringocapsa aff. vicentina (Squinabol)

Tetriastrum aff. tenue Yang

Triactoma luciae Jud

Tritrabs ewingi (Pessagno)

T. exotica (Pessagno) Xitus robustus Wu

Sample No. BR73

UTM Coordinates 501605/2499923

Age: Early Valanginian

Acanthocircus furiosus Jud

Acastea diaphorogona (Foreman)

Angulobracchia portmanni Baumgartner

Becus triangulocentrum Dumitrica

Dicerosaturnalis dicranacanthos (Squinabol)

Dicroa periosa Foreman

Emiluvia chica Forema

Halesium palmatum Dumitrica

Hemicryptocapsa capita Tan

Homoeoparonaella aff. peteri Jud

Paronaella tubulata Steiger

Pseudoeucyrtis tenuis (Rüst)

Triactoma luciae Jud

Sample No. BR75

UTM Coordinates 501605/2499923

Age: Late Valanginian

Acastea diaphorogona (Foreman)

Angulobracchia portmanni Baumgartner

Archaeodictyomitra conica (Aliev)

A. elegans (Tan)

Cecrops septemporatus (Parona)

Deviatus diamphidius (Foreman)

Dicerosaturnalis dicranacanthos (Squinabol)

D. major (Squinabol)

Ditrabs sansalvadorensis (Pessagno)

Halesium biscutum Jud

Pantanellium squinaboli (Tan)

Paronaella trifoliacea Ozvoldova

Pseudodictyomitra carpatica (Lozyniak)

Pyramispongia aff. barmsteinensis (Steiger)

Saitoum elegans De Wever

Savaryella guexi Jud

Spongosaturninus minimus (Squinabol)

Syringocapsa vicentina (Squinabol)

Tethysetta boesii (Parona)

Triactoma luciae Jud

Sample No. BR77

UTM Coordinates 501605/2499923

Age: Early Hauterivian

Acanthocircus furiosus Jud

Archaeospongoprunum patricki Jud

Archaeotritrabs gracilis Steiger

Aurisaturnalis variabilis variabilis (Squinabol)

Bistarkum irazuense (Aita)

Cecrops septemporatus (Parona)

Crucella lipmanae Jud, C. remanei Jud

Cyclastrum rarum Squinabol

Dicerosaturnalis dicranacanthos (Squinabol)

D. major (Squinabol)

Mictyoditra columbarium (Renz)

Pantanellium squinaboli (Tan)

Spongosaturninus squinaboli (Donofrio and Mostler)

Suna echiodes (Foreman)

Sample No. BR81

UTM Coordinates 501605/2499923

Age: Late Hauterivian

Acaeniotyle umbilicata (Rüst)

A. florea Ozvoldova

Acastea diaphorogona (Foreman)

Archaeospongoprunum patricki Jud

Aurisaturnalis cf. variabilis (Squinabol)

Cecrops septemporatus (Parona)

Cyclastrum planum Jud

Hemicryptocapsa agolarium (Foreman)

Mirifusus chenodes (Renz)

Parvicingula (?) usotanensis Tumanda

Podocapsa (?) imperialis Jud

Praecaneta longa (Jud)

Pseudodictyomitra nodosocostata Dumitrica

Pseudoeucyrtis tenuis (Rüst)

Sethocapsa orca Foreman

S. trachyostraca Foreman

Spongotripus (?) satoi Tumanda

Stylodictya titirez Jud

Suna echiodes (Foreman)

Svinitzium columnarium (Jud)

Thanarla lacrimula (Foreman)

Sample No. BR84

UTM Coordinates 519340/2511690

Age: Late Tithonian

Acanthocircus furiosus Jud

Acastea diaphorogona (Foreman)

Dicerosaturnalis dicranacanthos (Squinabol)

Ditrabs sansalvadorensis (Pessagno)

Emiluvia pessagnoi Foreman

Halesium irregulare Steiger

Katroma milloti Schaaf

Obesacapsula cetia (Foreman)

Pseudodictyomitra carpatica (Lozyniak)

Spongosaturnalis breviaculeatus (Donofrio and Mostler)

S. horridus (Squinabol)

Triactoma luciae Jud

T. tithoniana Rüst

Tritrabs ewingi (Pessagno)

Sample No. BR88

UTM Coordinates 519340/2511690

Age: Berriasian

Alievium regulare (Wu and Li)

Angulobracchia portmanni Baumgartner

Archaeodictyomitra excellens (Tan)

Deviatus diamphidius (Foreman)

Dicerosaturnalis dicranacanthos (Squinabol)

Emiluvia chica Foreman

E. hopsoni Pessagno

Pantanellium aduncum (Parona)

P. tredecimporatum (Rüst)

Parapodocapsa furcata Steiger

Podobursa triacantha (Fischli)

Podocapsa amphitreptera Foreman

Praecaneta cosmoconica (Foreman)

Pyramispongia barmsteinensis (Steiger)

Sethocapsa (?) concentrica (Steiger)

S. leiostraca Foreman

Triactoma tithonianum Rüst

Tritrabs ewingi (Pessagno)

Sample No. BR94

UTM Coordinates 519340/2511690

Age: Latest Berriasian?-Earliest Valanginian

Acaeniotyle umbilicata (Rüst)

Acastea diaphorogona (Foreman)

Angulobracchia heteroporata Steiger

A. media Steiger

A. portmanni Baumgartner

Archaeodictyomitra aff. pseudomulticostata (Tan)

Archaeospongoprunum patricki Jud

Archaeotritrabs gracilis Steiger

Becus triangulocentrum Dumitrica

Bistarkum irazuense (Aita)

Cyclastrum rarum Squinabol

Deviatus diamphidius (Foreman)

Dicerosaturnalis dicranacanthos (Squinabol)

D. longispinosus (Donofrio and Mostler)

Ditrabs sansalvadorensis (Pessagno)

Emiluvia chica Foreman

E. pessagnoi Foreman

Halesium biscutum Jud

H. palmatum Dumitrica

Hsuum arabicum Dumitrica

H. feliformis Jud

Katroma milloti Schaaf

Mictyoditra thiensis (Tan)

Paronaella trifoliacea Ozvoldova

P. tubulata Steiger

Phalangites acus (Jud)

Podocapsa amphitreptera Foreman

Praecaneta longa (Jud)

Pseudocrucella (?) elisabethae (Rüst)

Pseudoeucyrtis fusus Jud

P. tenuis (Rüst)

Pyramispongia barmsteinensis (Steiger)

Saitoum elegans De Wever

Savaryella guexi Jud

S. spathulata Dumitrica

Sethocapsa leiostraca Foreman

Spongocapsula verbana (Parona)

Spongosaturnalis multidentatus (Squinabol)

Spongosaturninus minimus (Squinabol)

Syringocapsa limatum Foreman

Tetratrabs radix Jud

Tritrabs aff. casmaliaensis (Pessagno)

Xitus robustus Wu

Sample No. BR97

UTM Coordinates 519340/2511690

Age: Valanginian

Angulobracchia aff. biordinale Ozvoldova

Archaeodictyomitra apiarium (Rüst)

A. tumandae Dumitrica

Dicerosaturnalis major (Squinabol)

D. trizonalis (Rüst)

Emiluvia chica Foreman

Mirifusus dianae (Karrer)

M. odoghertyi Jud

Pantanellium squinaboli (Tan)

Praecaneta cosmoconica (Foreman)

Sethocapsa trachyostraca Foreman

Triactoma tithonianum Rüst

Sample No. BR100a

UTM Coordinates 519340/2511690

Age: Coniacian-Early Santonian

Alievium gallowayi (White)

Dictyomitra formosa (Squinabol)

Patellulla planoconvexa (Pessagno)

Praeconocaryomma universa Pessagno

Pseudoaulophacus floresensis Pessagno

Pseudodictyomitra sp.

Sample No. BR107

UTM Coordinates 482424/2535125

Age: Early-Middle Bajocian, UAZ3

Archaeodictyomitra exigua Blome

Canutus izeensis Pessagno and Blome

Diacanthocapsa (?) operculi Yao

Eoxitus baloghi Kozur

E. hungaricus Kozur

Eucyrtidiellum unumaense (Yao)

Japonocapsa fusiformis (Yao)

Praewilliriedellum convexum (Yao)

P. japonicum (Yao)

Striatojaponocapsa plicara (Matsuoka)

Svinitzium kamoense (Mizutani and Kido)

Transhsuum maxwelli (Pessagno)

T. hisuikyoense Isozaki and Matsuda

Unuma latusicostatus (Aita)

Sample No. BR117

UTM Coordinates 489020/2524022

Age: Late Pliensbachian-Early Toarcian

Canoptum sp., Canutus sp.

Pantanellium sp.

Praeconocaryomma immodica Pessagno and Poisson

Praeconocaryomma spp.

Sontonaella sp. E. of Yeh (1987)

Sontonaella spp.

Orbiculiforma aff. multifora Pessagno and Poisson.

Sample No. BR131

UTM Coordinates 489020/2524022

Age: Early Toarcian

Bistarkum rigidum Yeh

Broctus sp., Droltus sp.

Katroma megasphaera Yeh and Cheng

Pleesus aptus Yeh

Podocapsa cf. abreojosensis Whalen and Carter

Pseudoristola obesa Yeh

Sample No. BR138

UTM Coordinates 489020/2524022

Age: Bajocian, UAZ3-4

Eoxitus hungaricus Kozur

Eucyrtidiellum unumaense (Yao)

Japonocapsa fusiformis (Yao)

Praewilliriedellum robustum (Matsuoka)

Protunuma costatus (Heitzer)

P. turbo Matsouka

Saitoum levium De Wever

Sethocapsa funatoensis Aita

Striatojaponocapsa plicara (Yao)

Svinitzium kamoense (Mizutani and Kido)

Sample No. BR139

UTM Coordinates 576289/2531795

Age: Middle-Late Bathonian-Early Callovian, UAZ6-7

Acaeniotylopsis variatus triacanthus Kito and De Wever

Archaeospongoprunum imlayi Pessagno

Hexasaturnalis aff. suboblongus (Yao)

Higumastra imbricata (Ozvoldova)

Mirifusus guadalupensis Pessagno

Palinandromeda cf. depressa (De Wever and Miconnet)

Praewilliriedellum convexum (Yao)

Stichomitra (?) takanoensis Aita

Svinitzium (?) kamoense (Mizutani and Kido)

Tetraditryma pseudoplena Baumgartner

Transhsuum brevicostatum (Ozvoldova)

Tritrabs ewingi (Pessagno)

Sample No. BR140

UTM Coordinates 576289/2531795

Age: Late Bathonian-Early Callovian, UAZ7

Angulobracchia jasperensis Hull

Archaeospongoprunum imlayi Pessagno

Cinguloturris carpatica Dumitrica

Emiluvia premyogii Baumgartner

Eucyrtidiellum ptyctum (Riedel and Sanfilippo)

E. unumaense (Yao)

Higumastra imbricata (Ozvoldova)

Mirifusus guadalupensis Pessagno

Palinandromeda depressa (De Wever and Miconnet)

Pseudoeucyrtis firmus Hull

Tetraditryma corralitosensis (Pessagno)

Tritrabs casmaliaensis (Pessagno)

Sample No. BR159

UTM Coordinates 576289/2531795

Age: Late Hauterivian

Acastea diaphorogona (Foreman)

Alievium regulare (Wu and Li)

Dicerosaturnalis dicranacanthos (Squinabol)

Pantanellium squinaboli (Tan)

Praexitus alievi (Foreman)

Pyramispongia barmsteinensis (Steiger)

Sethocapsa orca Foreman

Suna echiodes (Foreman)

Xitus normalis (Wu and Li)

Sample No. BR383

UTM Coordinates 463868/2573077

Age: Late Bajocian-Bathonian

Emiluvia lombardensis Baumgartner

Eucyrtidiellum unumaense (Yao)

Parahsuum officerense (Pessagno and Whalen)

Stichocapsa robusta Matsuoka

Sample No. BR387

UTM Coordinates 463868/2573077

Age: Kimmeridgian-Early Tithonian

Angulobracchia biordinalis Ozvoldova

Archaeospongoprunum imlayi Pessagno

Dicerosaturnalis minor (Baumgartner)

Emiluvia orea Baumgartner

E. pentaporata Steiger and Steiger

Mirifusus chenodes (Renz)

Orbiculiforma lowreyensis Pessagno

Paronaella centrodepressa Steiger and Steiger

Podobursa spinosa Ozvoldova

P. triacantha Fischli

Ristola altissima (Rüst)

Spongocapsula palmerae Pessagno

Tripocyclia jonesi Pessagno

Tritrabs ewingi (Pessagno)

T. imperfectas Hull

Sample No. BR388

UTM Coordinates 463868/2573077

Age: Late Tithonian

Archaeodictyomitra apiarium (Rüst)

A, excellens (Tan)

A. minoensis (Mizutani)

Artocapsa amphorella Jud

Cinguloturris cylindra Kemkin and Rudenko

Deviatus diamphidius (Foreman)

Dicerosaturnalis dicranacanthos (Squinabol)

Ditrabs sansalvadorensis (Pessagno)

Eucyrtidiellum pyramis (Aita)

Mirifusus dianae (Karrer)

Obesacapsula cetia (Foreman)

Paronaella tubulata Steiger

Podocapsa amphitreptera Foreman

Protunuma costatus (Heitzer)

Pseudodictyomitra cf. carpatica (Lozynyak)

Spongocapsula banala (Jud)

Syringocapsa spinellifera Baumgartner

Tethysetta boesii (Parona)

T. mashitaensis (Mizutani)

Sample No. BR415

UTM Coordinates 463868/2573077

Age: Late Barremian-Early Aptian, A. carinatus perforatus subzone

Acaeniotyle umbilicata (Rüst)

Angulobracchia heteroporata Steiger

Archaeodictyomitra lacrimula (Foreman)

A. longovata Dumitrica

Archaeospongoprunum patricki Jud

Aurisaturnalis carinatus perforatus Dumitrica and Dumitrica-Jud

Cyclastrum infundibulum (Rüst)

Dibolachras tytthopora Foreman

Dicerosaturnalis trizonalis (Rüst)

Mictyoditra columbarium (Renz)

Mirifusus chenodes (Renz)

Praeconosphaera sphaeroconus (Rüst)

Pseudodictyomitra lanceloti Schaaf

Sethocapsa orca Foreman

Suna hybum (Foreman)

Tethysetta boesii (Parona)

Samples No. BR416, BR417 UTM Coordinates 463868/2573077

Age: Late Pliensbachian-Early Toarcian

Bagotum cf. maudense Pessagno and Whalen

Bistarkum rigidum Yeh

Canoptum anulatum Pessagno and Poisson

Katroma bifurca Yeh K. inflata Yeh

Neowrangellium pessagnoi Yeh

Orbiculiforma callosa Yeh

Pleesus aptus Yeh

Pseudoristola obesa Yeh

Stauromesosaturnalis deweveri Kozur and Mostler

Sample No. BR419

UTM Coordinates 495050/2565965

Age: Late Anisian (Middle-Late Illyrian)

Hindeosphaera spinulosa (Nakaseko and Nishimura)

Paroertlispongus multispinosus Kozur and Mostler

Pentactinorbis awaensis (Nakaseko and Nishimura)

Pseudoertlispongus mostleri Kozur

Pseudostylosphaera japonica (Nakaseko and Nishimura)

Tiborella florida (Nakaseko and Nishimura)

Samples No. BR437, BR438 UTM Coordinates 495050/2565965

Age: Latest Carnian?-Early Norian

Canesium lentum Blome

Capnodoce spp.

Capnuchosphaera tricornis De Wever

Capnuchosphaera spp. Corum spp.

Mostlericyrtium sitepesiformis Tekin

Paronaella sp.

Selenella triassica Tekin

Xiphotheca rugosa Bragin

Sample No. BR454

UTM Coordinates 603865/2525960

Age: Middle Bajocian

Archaeohagiastrum longipes Baumgartner

Ares cylindricus (Takemura)

Eospongosaturninus protoformis (Yao)

Hexasaturnalis hexagonus (Yao)

H. suboblongus (Yao)

H. tetraspinus (Yao)

Higumastra gratiosa Baumgartner

Linaresia falloti (El Kadiri)

L. rifensis (El Kadiri)

Mirifusus praeguadalupensis Baumgartner

Palinandromeda depressa (De Wever and Miconnet)

P. sognoensis Baumgartner

Pantanellium sincerum Pessagno and Blome

Parahsuum officerense (Pessagno and Whalen)

Parasaturnalis diplocyclis (Yao)

Praewilliriedellum convexum (Yao)

Saitoum levium De Wever

Spongosaturninus bispinus (Yao)

Xiphostylus vallieri Pessagno and Yang

Zartus thayeri Pessagno and Blome

Sample No. BR457

UTM Coordinates 603865/2525960

Age: Middle Bajocian

Angulobracchia digitata Baumgartner

Eucyrtidiellum unumaense (Yao)

Hsuum matsuokai Isozaki and Matsuda

Palinandromeda sognoensis Baumgartner

Parahsuum officerense (Pessagno and Whalen)

Praewilliriedellum convexum (Yao)

Stichocapsa robusta Matsuoka

Stichomitra (?) takanoensis Aita

Transhsuum brevicostatum (Ozvoldova)

T. hisuikyoense (Isozaki and Matsuda)

Sample No. BR464

UTM Coordinates 603865/2525960

Age: Late Tithonian?-Berriasian

Acanthocircus furiosus Jud

Alievium picum Kiessling

Archaeospongoprunum patricki Jud

Becus triangulocentrum Dumitrica

Dicerosaturnalis dicranacanthos (Squinabol)

Katroma milloti Schaaf

Pantanellium aduncum (Rüst)

Paronaella tubulata Steiger

Spongosaturnalis breviaculeatus Donofrio and Mostler

Sample No. BR465

UTM Coordinates 603865/2525960

Age: Early Berriasian, UAZ5-8 of Jud, 1994

Acaeniotyle umbilicata (Rüst)

Alievium picum Kiessling

Dicerosaturnalis dicranacanthos (Squinabol)

Emiluvia chica Foreman

E. ultima Baumgartner and Dumitrica

Mirifusus dianae (Karrer)

Obesacapsula bullata Steiger

O. polyedra Steiger

Pantanellium squinaboli (Tan)

Podocapsa amphitreptera Foreman

Praecaneta cosmoconica (Foreman)

Ristola cretacea (Baumgartner)

Sethocapsa concentrica Steiger

S. leiostraca Foreman

S. trachyostraca Foreman

Suna echiodes (Foreman)

Svinitzium columnarium (Jud)

Syringocapsa agolarium Foreman

Tethysetta boesii (Parona)

Thanarla praegutta Dumitrica

Tritrabs ewingi (Pessagno)

Xitus robustus Wu

Sample No. BR489

UTM Coordinates 565130/2536004

Age: Callovian-Oxfordian

Eucyrtidiellum takemurai Hull

Paronaella broenimanni Baumgartner

Parvicingula dhimenaensis Baumgartner

Pseudocrucella adriani Baumgartner

Transhsuum brevicostatum (Ozvoldova)

Tritrabs casmaliaensis (Pessagno)

Sample No. BR490

UTM Coordinates 565130/2536004

Age: Callovian-Oxfordian

Angulobracchia digitata Baumgartner

Bernoullius sp.

Crucella theokaftensis Baumgartner

Tritrabs casmaliaensis (Pessagno)

T. exotica (Pessagno)

Sample No. BR499

UTM Coordinates 565130/2536004

Age: Hauterivian

Angulobracchia portmanni Baumgartner

Mirifusus dianae (Karrer)

Pyramispongia barmsteinensis (Steiger)

Spongocapsula obesa Jud

Syringocapsa limatum Foreman

Williriedellum petersmittae Schaaf

Sample No. BR536

UTM Coordinates 581991/2513455

Age: Late Tithonian-Berriasian

Alievium regulare (Wu and Li)

Deviatus diamphidius (Foreman)

Dicerosaturnalis dicranacanthos (Squinabol)

Ditrabs sansalvadorensis (Pessagno)

Pantanellium squinaboli (Tan)

Triactoma tithonianum Rüst

Tritrabs ewingi (Pessagno)

Sample No. BR537

UTM Coordinates 581991/2513455

Age: Berriasian

Acanthocircus breviaculeatus Donofrio and Mostler

Acanthocircus furiosus Jud

Alievium picum Kiessling

Archaeospongoprunum patricki Jud

Bistarkum irazuense (Aita)

Deviatus diamphidius (Foreman)

Emiluvia chica Foreman

E. hopsoni Pessagno

Katroma milloti Schaaf

Parapodocapsa furcata Steiger

Saitoum elegans De Wever

Tethysetta boesii (Parona)

Sample No. BR552

UTM Coordinates 581991/2513455

Age: Berriasian

Acanthocircus furiosus Jud

Angulobracchia portmanni Baumgartner

Archaeodictyomitra excellens (Tan)

Dicerosaturnalis dicranacanthos (Squinabol)

Emiluvia chica Foreman

Praecaneta cosmoconica (Foreman)

Praeconosphaera sphaeroconus (Rüst)

Pseudoeucyrtis fusus Jud

Pseudoeucyrtis tenuis (Rüst)

Suna echiodes (Foreman)

Svinitzium depressum (Baumgartner)

Tethysetta boesii (Parona)

Tetratrabs radix Jud

Tritrabs ewingi (Pessagno)

Sample No. BR560

UTM Coordinates 578108/2544420

Age: Aalenian

Archaeohagiastrum cf. longipes Baumgartner

Ares sp.

Elodium pessagnoi Yeh and Cheng

Higumastra sp.

Parahsuum (?) magnum Takemura

Tripocyclia yaoi Yeh and Cheng

Triversus cf. spinifer Takemura

Sample No. BR591

UTM Coordinates 578108/2544420

Age: Aalenian-?Bajocian

Acaeniotylopsis variatus triacanthus Kito and De Wever

Archaeohagiastrum longipes Baumgartner

Diacanthocapsa (?) cf. normalis Yao

Dictyomitrella (?) kamoensis Mizutani and Kido

Hsuum matsuokai (Isozaki and Matsuda)

H. primum Takemura

Hsuum (?) sp. 1 of Baumgartner et al. 1995

Parahsuum officerense (Pessagno and Whalen)

Transhsuum fukazawaense Sashida

Sample No. BR597

UTM Coordinates 503500/2571500

Age: Late Anisian

Paroertlispongus chinensis (Feng)

Sample No. BR598

UTM Coordinates 503500/2571500

Age: Late Anisian

Paroertlispongus multispinosus Kozur and Mostler

P. rarispinosus Kozur and Mostler

Plafkerium (?) contortum Dumitrica, Kozur and Mostler

Pseudostylosphaera sp.

Triassocampe spp.

Sample No. BR616

UTM Coordinates 503500/2571500

Age: Latest Carnian-Early Norian

Capnuchosphaera lea De Wever

C. theloides De Wever

C. tricornis De Wever

Mostlericyrtium sitepesiformis Tekin

Spongostylus carnicus Kozur and Mostler

Syringocapsa turgida Blome

Xiphotheca karpenissionensis De Wever

Sample No. BR627

UTM Coordinates 504457/2537267

Age: Late Callovian?-Oxfordian

Acaeniotylopsis variatus triacanthus De Wever and Kito

Cinguloturris carpatica Dumitrica

Dicerosaturnalis angustus (Baumgartner)

Emiluvia orea Baumgartner

E. salensis Pessagno

Eucyrtidiellum takemurai Hull

Hexasaturnalis minor (Baumgartner)

Homoeoparonaella argolidensis Baumgartner

Mirifusus guadalupensis Pessagno

Obesacapsula morroensis Pessagno

Palinandromeda podbielensis (Ozvoldova)

Pterotrabs arcubalista Dumitrica, Baumgartner and Gorican

Ristola procera (Pessagno)

Sethocapsa funatoensis Aita

Striatojaponocapsa conexa (Matsuoka)

Tetraditryma coldspringensis Pessagno, Blome and Hull,

Transhsuum brevicostatum (Ozvoldova)

T. maxwelli (Pessagno)

Tripocyclia jonesi Pessagno

Tritrabs casmaliaensis (Pessagno)

Zanola cornuta (Baumgartner)

Sample No. BR637

UTM Coordinates 504457/2537267

Age: Late Albian-Cenomanian

Pseudodictyomitra

pseudomacrocephala (Squinabol)

Rhoplaosyringium sp.

Stichomitra communis Squinabol

Sample No. BR648

UTM Coordinates 526238/2515183

Age: Bajocian

Hexasaturnalis suboblongus (Yao)

Parvicingula (?) dhimenaensis Baumgartner

Praevilliriedellum convexum (Yao)

Spongocapsula cf. palmerae Pessagno

Stichomitra (?) takanoensis Aita

Sample No. BR654

UTM Coordinates 565130/2536004

Age: Late Turonian-Coniacian

Alievium cf. praegallowayi Pessagno

Cryptamphorella conara (Foreman)

Dictyomitra formosa Squinabol sensu Pessagno

Gongylothorax werbeeki (Tan)

Hemicryptocapsa polyhedra Dumitrica

H. prepolyhedra Dumitrica

Praeconocaryomma universa Pessagno

Pseudodictyomitra tiara (Holmes)

Squinabolum fossile (Squinabol)

Sample No. BR655

UTM Coordinates 565130/2536004

Age: Late Norian-Rhaetian

Paelospongia turgida Mostler

Pentactinocarpus cf. sevaticus Kozur and Mostler

Sample No. BR704

UTM Coordinates 489020/2524022

Age: Late Bajocian-Early Bathonian

Archaeodictyomitra rigida Pessagno

Praewilliriedellum convexum (Yao)

Praewilliriedellum ? spinosum Kozur

Spongocapsula sp.

Striatojaponicapsa plicarum (Yao)

Transhsuum maxwelli (Pessagno)

Sample No. BR727

UTM Coordinates 548585/2493300

Age: Late Albian-Early Cenomanian

Rotaforma mirabilis Pessagno

Spongosaturnalis venetus (Squinabol)

Stichomitra communis Squinabol

Sample No. BR828

UTM Coordinates 586090/2512975

Age: Bajocian

Elodium sp.

Hsuum exiguum Yeh and Cheng

Linaresia chrafatensis El Kadiri

Mirifusus praeguadalupensis Baumgartner

Transhsuum breviaculeatum (Ozvoldova)

T. medium Takemura

Sample No. BR832

UTM Coordinates 621930/2494940

Age: Late Bathonian?-Callovian

Archaeospongoprunum imlayi Pessagno

Cinguloturris carpatica Dumitrica

Eucyrtidiellum takemurai Hull

Hexasaturnalis minor (Baumgartner)

H. aff. suboblongus (Yao)

Higumastra imbricata (Ozvoldova)

Leugeo ordinarius (Wu and Li)

Mirifusus dianae (Karrer)

M. guadalupensis Pessagno

Obesacapsula morroensis Pessagno

Palinandromeda podbielensis (Ozvoldova)

Spongocapsula palmerae Pessagno

Transhsuum brevicostatum (Ozvoldova)

T. maxwelli (Pessagno)

Tritrabs casmaliaensis (Pessagno)

Wilvemia whiskeyensis Pessagno, Blome and Hull,

Sample No. BR836

UTM Coordinates 621930/2494940

Age: Oxfordian

Archaeospongoprunum elegans Wu

Bernoullius dicera (Baumgartner)

Cinguloturris carpatica Dumitrica

Emiluvia cf. orea Baumgartner

Eucyrtidiellum takemurai Hull

Hexasaturnalis minor (Baumgartner)

Mirifusus guadalupensis Pessagno

Palinandromeda crassa (Baumgartner)

Palinandromeda podbielensis (Ozvoldova)

Paronaella mulleri Pessagno

Saitoum cf. elegans De Wever

Tethysetta mashitaensis (Mizutani)

Sample No. BR845

UTM Coordinates 621930/2494940

Age: Middle-late Oxfordian

Archaeodictyomitra rigida Pessagno

Archaeospongoprunum imlayi Pessagno

Bernoullius dicera (Baumgartner)

Cinguloturris carpatica Dumitrica

Hexasaturnalis minor (Baumgartner)

H. aff. suboblongus (Yao)

Mirifusus dianae (Karrer)

Olanda olorina Hull

Paronaella mulleri Pessagno

Podobursa spinosa Ozvoldova

Spongocapsula palmerae Pessagno

Tetratrabs zealis (Ozvoldova)

Transhsuum brevicostatum (Ozvoldova)

T. maxwelli (Pessagno)

Tripocyclia cf. jonesi Pessagno

Tritrabs casmaliaensis (Pessagno)

T. ewingi (Pessagno)

Sample No. BR850

UTM Coordinates 621930/2494940

Age: Kimmeridgian

Angulobracchia biordinale Ozvoldova

Archaeodictyomitra minoensis (Mizutani)

Archaeospongoprunum cf. patricki Jud

Cinguloturris carpatica Dumitrica

Crucella theokaftensis Baumgartner

Deviatus hipposidericus (Foreman)

Emiluvia ordinaria Ozvoldova

E. pentaporata Steiger and Steiger

Hexasaturnalis aff. suboblongus (Yao)

Mirifusus dianae (Karrer)

Olanda olorina Hull

Paronaella centrodepressa Steiger and Steiger

Paronaella mulleri Pessagno

Protunuma costatus (Heitzer)

Ristola altissima (Rüst)

Spongocapsula dumitricai Widz and De Wever

Staurolonche spathulata Steiger and Steiger

Stichocapsa pulchella (Rüst)

Triactoma blakei (Pessagno)

Triactoma paramericana Pessagno and Yang

Tritrabs casmaliaensis (Pessagno)

Triversus cf. fastigatus Hull

Sample No. BR851

UTM Coordinates 621930/2494940

Age: Kimmeridgian

Angulobracchia biordinale Ozvoldova

A. zeissi Steiger and Steiger

Archaeodictyomitra apiarium (Rüst)

Archaeospongoprunum patricki Jud

Cinguloturris fusiforma Hori

Emiluvia cf. chica Foreman

E. pentaporata Steiger and Steiger

Eucyrtidiellum ptyctum (Riedel and Sanfilippo)

Hexasaturnalis minor (Baumgartner)

Mirifusus dianae (Karrer)

Paronaella cf. mulleri Pessagno

Podobursa kandrica (Kocher)

Podocapsa foremanae Yang

Protunuma costatus (Heitzer)

Spongocapsula dumitricai Widz and De Wever

S. palmerae Pessagno

Suna echiodes (Foreman)

Teichertus cf. cavernosus Hull

Tetratrabs bulbosa Baumgartner

Triactoma blakei (Pessagno)

Tricolocapsa cf. campana Kiessling

Tripocyclia cf. jonesi Pessagno

Tritrabs casmaliaensis (Pessagno)

T. exotica (Pessagno)

Sample No. BR852

UTM Coordinates 621930/2494940

Age: Tithonian

Acanthocircus furiosus Jud

Archaeodictyomitra excellens (Tan)

Dicerosaturnalis dicranacanthos (Squinabol)

Ditrabs osteosa Jud

Emiluvia chica Foreman

Mirifusus dianae (Karrer)

Pantanellium cf. berriasianum Baumgartner

P. cf. squinaboli (Tan)

Paronaella tubulata Steiger

Pseudodictyomitra cf. carpatica (Lozyniak)

Sethocapsa praeuterculus Aita

Spongocapsula banala (Jud)

Triactoma cf. tithonianum Rüst

Tritrabs ewingi (Pessagno)

Sample No. BR854

UTM Coordinates 621930/2494940

Age: Tithonian

Alievium picum Kiessling

Cinguloturris cylindra Kemkin and Rudenko

Dicerosaturnalis dicranacanthos (Squinabol)

Emiluvia pessagnoi Foreman

Loopus yangi Dumitrica

Mirifusus dianae (Karrer)

Obesacapsula bullata Steiger

O. cetia Foreman

Pantanellium squinaboli (Tan)

Podocapsa amphitreptera Foreman

Praecaneta longa Jud

Protunuma costatus (Heitzer)

Pyramispongia barmsteinensis (Steiger)

Sethocapsa leiostraca Foreman

Tritrabs rhododactylus Baumgartner

Sample No. BR855

UTM Coordinates 621930/2494940

Age: Tithonian

Archaeodictyomitra excellens (Tan)

A. minoensis (Mizutani)

Bistarkum brevilatum Jud

Cinguloturris cylindra Kemkin and Rudenko

Emiluvia chica (Foreman)

E. pessagnoi Foreman

Eucyrtidiellum pyramis (Aita)

Obesacapsula cetia Foreman

O. rusconensis umbriensis Jud

Praecaneta cosmoconica (Foreman)

Svinitzium depressum (Baumgartner)

Triactoma tithonianum Rüst

Tricolocapsa campana Kiessling

Sample No. BR858

UTM Coordinates 621930/2494940

Age: Latest Tithonian?-Berriasian

Alievium picum Kiessling

Archaeodictyomitra minoensis (Mizutani)

Archaeospongoprunum patricki Jud

Artocapsa (?) amphorella Jud

Deviatus diamphidius (Foreman)

Dicerosaturnalis dicranacanthos (Squinabol)

Emiluvia chica Foreman

Hiscocapsa grutterinki (Tan)

Hsuum feliformis Jud

Loopus yangi Dumitrica

Mirifusus dianae (Karrer)

Neorelumbra tippitae Kiessling

Pantanellium squinaboli (Tan)

Parapodocapsa furcata Steiger

Paronaella tubulata Steiger

Pseudodictyomitra carpatica (Lozyniak)

Saitoum elegans De Wever

Sethocapsa kitoi Jud

Spongosaturnalis breviaculeatus (Donofrio and Mostler)

Svinitzium depressum (Baumgartner)

Tethysetta boesii (Parona)

Triactoma cf. tithonianum Rüst

Xitus robustus Wu

Sample No. BR862

UTM Coordinates 621930/2494940

Age: Berriasian

Acanthocircus furiosus Jud

Alievium picum Kiessling

Angulobracchia portmanni Baumgartner

Archaeodictyomitra apiarium (Rüst)

Archaeotritrabs gracilis Steiger

Cinguloturris cylindra Kemkin and Rudenko

Deviatus diamphidius (Foreman)

Dicerosaturnalis dicranacanthos (Squinabol)

Emiluvia chica Foreman

E. pessagnoi Foreman

Eucyrtidiellum pyramis (Aita)

Hsuum raricostatum Jud

Loopus yangi Dumitrica

Mictyoditra thiensis (Tan)

Mirifusus dianae (Karrer)

Obesacapsula cetia (Foreman)

Pantanellium squinaboli (Tan)

Pseudodictyomitra carpatica (Lozynyak)

Pyramispongia barmsteinensis (Steiger)

Ristola cretacea (Baumgartner)

Sethocapsa kitoi Jud S. leiostraca Foreman

Spongosaturnalis breviaculeatus (Donofrio and Mostler)

Stichomitra doliolum Aita

Tricolocapsa (?) campana Kiessling

Sample No. BR876

UTM Coordinates 462334/2558546

Age: Middle Bathonian-Early Callovian, UAZ6-7

Archaeospongoprunum elegans Wu

Cinguloturris carpatica Dumitrica

Gongylothorax sakawaensis Matsuoka

Pseudoristola nova Yang and Wang

Stichomitra (?) takanoensis Aita

Transhsuum brevicostatum (Ozvoldova)

Sample No. BR895 UTM Coordinates 706511/2496352

Age: Late Anisian (Middle-Late Illyrian)

Hindeosphaera spinulosa (Nakaseko and Nishimura)

Paroertlispongus diacanthus (Sugiyama)

P. multispinosus Kozur and Mostler

Spongosilicarmiger italicus Kozur and Mostler

Tiborella florida austriaca Kozur, Krainer and Mostler

Sample No. BR929 UTM Coordinates 706511/2496352

Age: Latest Carnian?-Early Norian

Capnodoce anapetes De Wever

C. sarisa De Wever

Capnuchosphaera constricta (Kozur and Mock)

C. crassa Yeh

C. tricornis De Wever

Kahlerosphaera kemerensis adentata Tekin

Mostlericyrtium sitepesiformis Tekin

M. striatum Tekin

Parentactinia globus (Sugiyama)

Spongostylus tortilis Kozur and Mostler

Trialatus robustus (Nakaseko and Nishimura)

Tritrabs (?) trammeri (Kozur and Mostler)

Xiphotheca karpenissionensis De Wever

X. rugosa Bragin

Sample No. BR942 UTM Coordinates 470315/2555220

Age: Latest Bathonian-Early Callovian

Angulobracchia cf. digitata Baumgartner

Archaeospongoprunum imlayi Pessagno

Higumastra imbricata (Ozvoldova)

Leugeo parvispinata Hull

Mirifusus guadalupensis Pessagno

Transhsuum hisuikyoense (Isozaki and Matsuda)

Sample No. BR956 UTM Coordinates 463868/2573077

Age: Late Aalenian-Early Bajocian

Bistarkum sp.

Tricolocapsa sp.

Sample No. BR1094/2 UTM Coordinates 569514/2538712

Age: Late Bajocian-Early Bathonian

Linaresia chrafatensis El Kadiri

Striatojaponocapsa plicara (Yao)

Tetraditryma sp.

Tritrabs ewingi (Pessagno)

Sample No. BR1120, BR1121 UTM Coordinates 569514/2538712

Age: Late Pliensbachian?-Early Toarcian

Bagotum erraticum Pessagno and Whalen

Bistarkum bifurcum Yeh

Jacus (?) anatiformis De Wever

Canoptum anulatum Pessagno and Poisson

Formania sandilandensis Whalen and Carter

Paracanoptum simplum Yao

Parasaturnalis diplocyclis (Yao)

Praeconocaryomma parvimamma Pessagno and Poisson

Pseudoristola obesa Yeh

Trillus elkhornensis Pessagno and Blome

Sample No. BR1131 UTM Coordinates 569514/2538712

Age: Aalenian?-Early Bajocian

Acaeniotylopsis variatus triacanthus Kito and De Wever,

Eucyrtidiellum unumaense (Yao)

Hsuum primum Takemura

Hsuum sp.1 in Baumgartner et al., 1995

Overview of the conodont assemblages and their age mentioned in this contribution.

Conodont assemblage

Sample No. B C347

UTM Coordinates 498805/2568647

Age: Middle Norian

Epigondolella slovakensis (Kozur and Mostler)

Sample No. BC349

UTM Coordinates 503500/2571500

Age: Early Norian

Epigondolella triangularis (Budurov and Stefanov)

Sample No. BC351

UTM Coordinates 503500/2571500

Age: Early Norian

Epigondolella cf. quadrata Orchard

Sample No. BC353

UTM Coordinates 503500/2571500

Age: Early-Middle Triassic (Scythian-Anisian)

Ellisonia sp.

Sample No. BC355

UTM Coordinates 495050/2565965 Age: Early-Middle Triassic (Scythian-Anisian)

Ellisonia teicherti Sweet

Sample No. BC769

UTM Coordinates 495050/2565965

Age: Middle Scythian (Olenekian/

Smithian)

Scythogondolella milleri (Müller)

Neospathodus spathi Sweet

Ellisonia triassica (Müller)

Ellisonia sp.

Sample No. BC767

UTM Coordinates 495050/2565965

Age: Early Norian

Epigondolella cf. triangularis (Budurov and Stefanov)

ABOUT THE AUTHORS

Ingo Blechschmidt is a Research Scientist at the Institute of Geological Sciences at the University of Bern, Switzerland. He received an MSc in Geology from the University of Jena in 1998 and a PhD from the University of Bern in 2002. His main fields of interest are the sedimentological and structural evolution of mixed carbonate-siliciclastic deep-marine systems. For the past four years Ingo has been mainly involved in basin analysis research including 3-D reconstructions of facies patterns and the stratigraphic architecture of the allochtonous sedimentary units from the Hawasina Complex, Oman Mountains.

blechschmidt@geo.unibe.ch

Paulian Dumitrica is a Consulting Micropalaeontologist specialising in the taxonomy and biostratigraphy of siliceous microfossils (radiolarians, silicoflagellates and ebridians), and Associate Researcher at the University of Lausanne. He previously worked as a Micropalaeontologist at the Geological Institute of Romania in Bucharest until 1993. Paulian holds a PhD in Miocene Silicoflagellates from the University of Bucharest. Since 1994, in collaboration with the University of Bern, he has been deeply involved in the biostratigraphy of the Mesozoic formations from Oman.

paulian.dumitrica@igp.unil.ch

Albert Matter is Professor Emeritus at the University of Bern from where he received his PhD in Geology in 1964. His areas of interest include sedimentology, groundwater hydrogeochemistry and clastic diagenesis. Since 1967 Albert has been working in Oman, partly in cooperation with Petroleum Development Oman. Currently he is involved in sedimentological studies in Oman and in a palaeoclimate project which aims to develop palaeoclimate records of variation in Monsoon rainfall in Oman, Yemen and Saudi Arabia during the Pleistocene and Holocene.

albert.matter@geo.unibe.ch

Leopold Krystyn is Professor of Palaeontology at Vienna University. He is a specialist in Mesozoic ammonoids and in Triassic conodonts with special emphasis on the refinement of the Triassic time scale. Other research interests are the Triassic magnetobiochronology and the palaeo (bio) geography of the early Neo-Tethys as well as the sedimentary history of its margins. He is a member of the Subcommission on Triassic Stratigraphy, chairman of the Norian-Rhaetian boundary working group and co-leader of IGCP project 467.

leopold.krystyn@univie.ac.at

Tjerk Peters is Emeritus Professor at the University of Bern, from which he received a PhD in 1963. Since 1968 he has worked in the Oman Mountains. Tjerk’s research projects on the regional geology of the allochthonous magmatic, sedimentary and metamorphic rocks on the northern and eastern edge of the Arabian continental margin are aimed at the tectonic-magmatic evolution of the Southern Tethys and Western Indian Ocean.

tjerk@bluewin.ch