ABSTRACT The concept of this volume was, initially conceived in June of 1977 at a “Gasthof ” situated on the Austrian-Italian border at Nassfeld, Austria. During that Summer I had been invited by the Geologische Bundesanstalt of Vienna, through the courtesy of Dr. Harald Lobitzer, to lecture on Paleozoic organic buildups at the University of Vienna. After a brief stay in Vienna, a small group including Lobitzer, myself, my wife, and Dr. Werner Pil 1er of the University of Vienna, embarked The concept of this volume was, initially conceived in June of 1977 at a “Gasthof ? situated on the Austrian-Italian border at Nassfeld, Austria. During that Summer I had been invited by the Geologische Bundesanstalt of Vienna, through the courtesy of Dr. Harald Lobitzer, to lecture on Paleozoic organic buildups at the University of Vienna. After a brief stay in Vienna, a small group including Lobitzer, myself, my wife, and Dr. Werner Pil 1er of the University of Vienna, embarked on a field excursion to examine Mesozoic organic buildups throughout Austria. During this excursion we visited many spectacular Mesozoic (mainly Triassic) reef outcrops, and I was impressed by the amount of detailed work that had been, or that was in the process of being, com-pleted on these outcrops by both Geological Survey and academic workers. I was informed that some of this detailed information was already published, albeit in regional journals of rather limited distribution, and of course, written in German. Still, I was unaware of much of this information, especially that related to ongoing work, and even of some of the older work, which until James Lee Wilson's text on Carbonate Fades in Geologic History was made available in 1975, had previously not been generally known to an English-reading audience. After visiting exceptional reef exposures at Adnet, I suggested to my host colleagues the possibility of perhaps gathering to-gether a number of Austrian Mesozoic reef studies, translating them into English, and publishing them as a so-called “Reef Volume.” We continued to discuss this proposition and considered a number of alternatives until we arrived in the Carnic Alps of southernmost Austria. Here, we were joined by Dr. Erik Flügel, Director of the Paleontological Institute at Erlangen, West Germany, along with a number of his graduate students, During dinner of the first evening we asked Erik Flügel his opinion of our rather preliminary intention to organize a group of Austrian workers for the purpose of publishing an English volume on some of the visited Austrian reef outcrops. His response was immediate and positively enthusiastic, and he further suggested that we broaden the scope of the volume to include “reef models” from all over Europe, concentrating our attento various colleagues and that Lobitzer would act as Coordinator for our efforts and initially receive any forthcoming manuscripts. Thus the idea for a “European Fossil Reef Models” volume was born.

Abstract Accurate interpretations of facies in ancient reefs requires both proper “classification” of the reef and an understanding of the sedimentologie and biologic processes active during the formation of the reef. Study of modern reefs provides evidence for the processes affecting facies in reef complexes with a rigid organic framework and steep fore-reef wall, but generally reveals only the incipient products of these processes because most Holocene reefs have been growing for only a few thousand years following the Holocene transgression. Only where underlying topography approximates the profile of a mature reef complex can well developed examples of the sedimentologie facies of a mature reef complex be found in modern reefs. Study of these pseudo-mature reef complexes reveals a sequence of sedimentologie facies (from basin toward land) consisting of: I. distal talus, 2. proximal talus, 3. reef-slope, 4. reef framework, 5. reef-crest, 6. reef-flat, and 7. back-reef sand. Knowledge of the characteristics and distribution of these facies should facilitate facies interpretation in comparable ancient reef complexes. Reef framework forms only a few percent of the volume of a mature reef complex, whereas the vast majority of the complex consists of debris in fore-reef and back-reef facies; the debris being derived largely from the framework. This has particular significance in hydrocarbon exploration because most wells drilled toward the top of a seismicly defined ancient reef complex would penetrate only the back-reef carbonate sand facies. However, this is as it should be because the reef framework facies generally has little preserved primary porosity due to sediment infilling of cavities and extensive marine cementation. The facies of modern reef complexes discussed here exist due to the presence of a significant marginal (as opposed to centrally located) shallow water, wave resistant, rigid organic framework composed largely of scler-actinian corals. Similar facies may be expected in those fossil reef complexes with a more or less comparable organic framework such as the Devonian stromatoporoid/tabulate coral reefs, the Permian algal/sponge/marine cement reefs, and the Neogene coral reefs. However, different facies must occur in ancient reefs that lacked rigid organic frameworks such as the Paleozoic bryozoan and/or crinoid mounds, Late Paleozoic phylloid algal mounds, Cretaceous rudistid banks, and early Tertiary Nummulites banks.

ABSTRACT Silurian reefs of northern Europe occur in cratonic sedimentary sequences which have been relatively well documented stratigraphically and paleontologically although the reefs have generally been less closely examined than the level bottom communities. Reef development adjacent to the Caledonian Belt was restricted by siliciclastic sedimentation and this is also reflected in the low proportions of carbonate rocks in the Welsh Borderland and Oslo successions. Marine sequences in the Baltic areas of Gotland and Estonia are relatively thin and contain much higher proportions of both carbonates and reefs. Four main types of reef are recognizable on Gotland. Axelsro (previously termed Upper Visby) and Hoburgen Reefs are essentially tabulate coral and stromatoporoid dominated bioherms of moderate to high diversity. Their dense structure and argillaceous matrix made them locally unstable and prone to marginal collapse and internal displacement. Important accessory reef builders include rugose corals, calcareous algae, Problematica, and bryo-zoans. Similar bioherms, particularly of the smaller tabulate rich Axelsro type, are well developed in the Wenlock Limestone of the Welsh Borderland of England where good examples occur at Wenlock Edge. They are also present in the Oslo Region of Norway, together with tabulate dominated bioslromes and Rothpletzella-Wetheredella bioherms, and occur at several horizons, sometimes very extensively, in the Llandovery and Wenlock. In Gotland, Hoburgen reefs are especially widespread at numerous horizons, but a unique feature is the occur-rence of Kuppen and Holmhällar type stromatoporoid biostromes which have rigid dense to frame structures and relatively low diversity. They are interpreted as shallow water, high energy linear reefs which developed prefer-entially'in the cratonic interior.The Estonian Silurian sequence shows close similarities to that in Gotland. Reefs are developed at a number of horizons but are generally little documented in detail. Reef geometry and organic composition were controlled by environmental factors. The size and morphology of the organisms in turn determined the internal structure of the reefs. The bioherms show internal displacement and differential compaction of adjacent sediments in response to their own weight and to subsequent overburden. The biostromes behaved more rigidly and compaction was taken up mainly by stylolitization of adjacent large skeletons.

ABSTRACT Devonian reefs are widespread in Europe, but with the exception of those in Germany and Belgium most have not been widely described in the international geological literature. The present paper aims to amend this situation by providing a general synthesis of published data on all significant European Devonian reef occurrences. Particular attention is paid to their classification and, where possible, to the factors which governed their location and evolution. The earliest reefs occur in that part of Europe, the “internal” zone of the Hercynian Orogen, which was not strongly affected by the Siluro-Devonian Caledonian earth movements and in which there was continuous marine deposition from the Lower Paleozoic through to at least the Middle Devonian (southeastern Alps, Bohemia, Armorican Massif, and the Cantabrian and Pyreneean Mountains). In the “external” zone (e.g., the “Rhenoher-cynian” be!t, including southwestern England, the Ardennes, Rhenish Schiefergebirge, Harz Mountains, Poland, and Moravia), which experienced uplift and mild deformation on the periphery of the Caledonian Orogen, and where the Devonian usually overlies the Lower Paleozoic unconformably, reef growth did not begin until the Middle Devonian. Here, Lower and early Middle Devonian deposits (and locally the whole Devonian succession) are in a clastic fluviatile or neritic facies. In some cases the Lower Devonian is absent altogether. In most areas, irrespective of this early history, reef growth continued until the late Frasnian or earliest Famennian, when (among other factors) widespread rise in relative sea level caused their extinction, and pelagic sedimentation became the norm. European Devonian reefs fall into five broad morphological categories: 1. banks, 2. biostromal complexes, 3. barrier-reef complexes, 4. isolated reef complexes (reef-mounds and atolls), and 5. quiet water carbonate buildups (“mud-mounds”). These possess characteristic sedimentary and organic facies associations and distribution patterns. Types 2. to 4. exhibit lateral differentiation into facies-zones (e.g., reef-core and back-reef in atolls, barrier-reef and biostromal complexes, plus fore-reef in most well developed buildups). Factors which influenced the location and development of reefs in the European Devonian included: 1. local crustal flexures and movement on basin-margin hingelines, 2. synsedimentary faulting, 3. synsedimentary volcanicity, 4. the distribution of small scale elevations on the seafloor (e.g., buried reefs, calcarenite banks), and 5. changes in relative sea level where not clearly attributable to one of the previous factors. Variation in the relationship between reef growth and changes in, or inconsistencies in the rate of change, of relative sea leve! are expressed in basin-marginal reef complexes as sequences of transgression and regression, and in isolated reef complexes as vertical eco!ogical and facial zonation. Successive minor transgressive pulses within broader trends are recorded in the back-reef facies of Middle and Upper Devonian biostromal and barrier-reef complexes of central Europe, and of Middle and Upper Devonian reefs of the southeastern Alps, as depositional cyclicity on the scale of a few meters. Time-equivalent deposits of European Devonian reefs are shelf and basinal black shales and pelagic limestones. These commonly contain intercalations of reefal debris as turbiditic or “allodapic” limestones. Following extinction some reefs were buried relatively rapidly by subsequent sediments, whereas others underwent prolonged periods of submarine, or very locally subaerial exposure, and were buried only in the latest Devonian or early Carboniferous. Concomitant with the late growth and early post-growth stages, many reefs developed extensive systems of fissures which were filled both syngenetically and post-genetically with fibrous carbonate cements and internal sediments. The latter commonly contain faunas which are substantially younger than the host reefal limestones themselves. Early diagenetic carbonate cements are features in many reefal facies, and vary in character from one of these to another. Early vadose cements (microstalactitic and drusy pore linings) are most important in back-reef facies, while in reef-core and fore-reef deposits synsedimentary submarine fibrous cements predominate. In “mud-mounds” stromatactis is an important early diagenetic structure. Dolomitization is extensive in some areas, but is a difficult feature to qualify; some occurrences, especiaUy in central Europe, may be early stage replacement. Later cementation appears to have followed much the same course in all areas for which data presently exist, though neomorphism and response to tectonic stress of the carbonates was more varied. To date, no significant hydrocarbon deposits have been discovered in European Devonian reefs, although minor traces do occur in central Europe.

ABSTRACT Carbonate buildups representing “stratigraphie reefs” were formed during the Lower Permian (Sakmarian) and lower Artinskian at the margins of carbonate platforms in southern Austria and northern Italy. These buildups were formed by the interaction of encrusting algae (Tubiphytes and Archaeolithoporella), bryozoans, and syndepositional eogenetic radial-fibrous cements.

ABSTRACT A major linear reef ultimately more than 100 meters high protected the seaward edge of the carbonate shelf of the Upper Permian Middle Magnesian Limestone in northeastern England, and is overlain by an extensive stromatolite biostrome. Rocks of both structures are almost completely dolomitized. The reef is founded on a patchy lenticular coquina, and much of its lower parts is formed of typically unbedded bryozoan biolithite which appears to have formed subaqueously and grew mainly upwards. Some contemporaneous lithification and rigidity is indi? cated by the presence of biolithite debris in associated talus. Middle stages of reef growth are characterized by a progressive increase in the proportion of algal rocks and laminar organic or inorganic encrustations at the expense of the bryozoa that dominated in early stages, and a tendency towards bedding may indicate shallowing towards the end of this phase. Stromatolitic and other laminar rocks became dominant in latest phases of reef growth, where the evidence of active contemporaneous erosion, roughly horizontal bedding and lateral rather than upwards growth is thought to indicate proximity of the top of the reef to sea level. The growth and increasing asymmetry of the reef led to progressively more complete separation of environments to landward and seaward of the reef, culminating when the reef approached sea level in the formation of a lagoon and a starved or semi-starved basin. Scattered small patch-reefs occur locally in lagoonal beds in the north of the area and considerably larger masses of reef rock in the same area are probably also patch-reefs but could be outliers of a much widened main reef. The stromatolite biostrome is a relatively uniform tabular body up to 30 meters thick formed of finely-laminated subtidal algal stromatolites on the flat top of the Middle Magnesian Limestone reef. Algal growth forms are diverse only at the lagoonal and basinal margins of the biostrome, the basinal margin also being varied by the presence, in its lower part, of conglomerates composed of rolled cobbles and boulders of biolithite possibly derived from the underlying reef.

ABSTRACT Patch-reefs commonly 10 to 25 meters across and 3 to 8 meters thick are abundant in dolomitized skeletal oolite of the Upper Permian Lower Magnesian Limestone in Yorkshire, England, and are themselves dolomitic. They are roughly circular or oval in plan and irregular in section, with a common tendency for a shallow inverted cone to be surmounted by a gentle dome. All are stratigraphically younger than a widespread coquina which lies near the base of the formation and may have provided a stable foundation for reef forming organisms. Most of the reefs comprise an untidy assemblage of sack-shaped bodies ('saccoliths'), each composed mainly of closely-packed sub-parallel remains of the ramose bryozoa Acanthocladia (generally predominant) and Thamnis-cus in a finely crystalline dolomite matrix, which commonly also contains a low diversity community of other invertebrates. It is tentatively suggested that each saccolith is founded on a singly colony of Acanthocladia anceps (Schlotheim). The reefs probably were formed entirely under water on a broad shallow tropical carbonate marine shelf, and the tops of most were less than 2 meters higher than surrounding contemporaneous sediment. Mud-trapping and binding by bryozoa appears to have been the main constructional process, with encrusting foraminifers and early submarine cements adding stiffening and bulk. Bryozoa die out in upper parts of the formation, where the reefs are composed largely or wholly of algal stromatolitic dolomite that was also probably formed subaqueously but in shallower water than the earlier bryozoan parts of the reefs.

ABSTRACT The Middle Triassic Wetterstein Limestone platform north of Innsbruck, Austria, forms a gently dipping platform that contains various organic buildups. The upper part of this platform is dominated by a massive reef laid down in shallow water (Hafelekar Reef complex), whereas the lower portion of the Wetterstein Limestone contains conspicuous patch-reefs. The massive shallow water reef in the upper part of the Wetterstein Limestone shows a distinct biotic zonation. This zonation reflects a rather simple pattern of ecological zones attesting to a smooth transition of biological adaptation by various reef organisms. Reef growth in the patch-reef sequence appears to have been influenced by subsidence associated with sea level changes, and a gradual increase of skeletal debris derived from actively accreting shallow water reefs. It is throught that a sea level rise in excess of 10 meters would prove sufficient to obstruct patch-reef growth. Sea level rise activated short lived basinal sedimentation adjacent to the reef area. Basinal sediments are characterized by radiolarian-bearing limestones. This same event however, initiated a revival of rapid reef growth on the platform. Here reefs are composed of calcisponges, Tubiphytes, and tubular foraminifers. Reef and lagoonal areas are separated by a barrier of skeletal sand shoals. Large scale syngenetic submarine cementation of the reefs was followed by early diagnetic dolomitization. Subsequent sedimentation and cementation produced conspicuous thick coatings of fibrous spar (?aragonite), and these are interpreted as diagenetic fabrics that formed during an early burial stage. Synsedimentary tectonics was especially active along the rim of the Wetterstein carbonate platform, as part of a much broader tectonic phase that was active and affected the Middle Triassic Tethys. In general, development of the Wetterstein carbonate platform was a regressive phase frequently disrupted by disturbances caused by continued subsidence in association with block-faulting tectonics.

ABSTRACT Six circular-shaped quiet water coral bioherms of Upper Triassic (Cordevolian) age, ranging from 25 to 140 meters in height and from 50 to 180 meters in diameter, outcrop 20 kilometers north-northwest of Idrija in western Slovenia, northwestern Yugoslavia. Within the biohermal depositional area two distinctive lithological and faunal associations have been identified. These are: 1. the biohermal core and marginal breccias which pass into, 2. surrounding bedded biopelmicritic limestones. The biohermal cores are composed primarily of corals and consist of various biolithites and biopelmicritic limestones. A relatively quiet water depositional environment is suggested for these bioherms. This interpretation is reinforced by the occurrence of only modest accumulations of marginal breccias, and the occurrence of layered pelbiomicritic limestones between individual bioherms. These circular bioherms are surrounded and embedded in a sequence of interbedded sandstones and shales.

ABSTRACT Four Upper Triassic patch-reefs exposed in the Northern Limestone Alps of the Salzburg area of Austria were subjected to detailed study. Especial emphasis was placed on facies development and paleoecologic zonation of the reef complexes. The Adnet Reef structure grew directly on a carbonate platform in a shallow water carbonate setting; the Rötelwand and Feichtenstein Reef complexes grew out of the Kössen Basin in two distinct stages: 1. a deeper water mud-mound stage and 2. a shallow water reef stage; whereas, the Gruber Reef, which also developed within the Kössen Basin, only shows a deeper water mud-mound stage, since a shallow water phase did not develop at this location. The shallow water reef stages of the reef complexes display a lateral facies zonation consisting of five different facies units: 1. coral-sponge facies of the central reef areas, 2. oncolitic facies of the exposed upper reef-slopes within zones of highest water energy, 3. algal-foraminiferal facies of the exposed lower reef-slopes, and as the foundation of the Adnet Reef structure, 4. reef detritus-mud facies of the leeward and deepest portions of the reef-$Iopes, where reefal components interfinger with Kössen basinal sediments, and 5. terrigenous-mud facies of the basin proper. The Rötelwand and Feichtenstein Reef complexes display a linear facies zonation, while the Adnet Reef Structure displays a circular and somewhat patchy facies zonation. Organism communities forming the reef biota are characterized by the association of various reef framebuilders and their epi- and endobionts. The compositional relationships of the various patch-reefs, their gross morphology, paleoecologic setting, and depositional environments have been studied in detail. This study has demonstrated that calcareous algae, various microproblematica, and foraminifers show very distinct distributional patterns within the reef complexes, and can be used as facies indicators as well as differentiating different biotopes within the central reef areas.

ABSTRACT Reinvestigation of the Upper Triassic (Norian-Rhaetian) Steinplatte “reef ? of the Northern Limestone Alps near Salzburg, Austria, revealed a clear facies zonation of this carbonate complex. The upper Kössen Beds are of a basinal facies and are composed of dark bedded limestones, poor in fossils, and partly intercalated with marls. The “Oberrhatkalk,” which is the time equivalent of the uppermost part of the Dachstein Limestone, can be subdivided into a fore-reef, reef, and back-reef facies. The fore-reef is characterized by crinoids and by reef derived particles, which were deposited on a slope with dips up to 35 degrees. The upper boundary of the fore?reef is marked by a coquina, built by shells of bivalves and brachiopods. The reef is represented by a narrow zone (less than 100 meters wide) which can be subdivided into: 1. reef-slope, with a diversified organism community of various corals, calcareous sponges, hydrozoans, tabulozoans/bryozoans, and microproblematica, embedded in a micritic matrix, and 2. reef-crest, represented as a belt of large phaceolid corals. Facies zonation consists of a back-reef facies, and a patch-reef facies which is characterized by two types of patch-reefs: one dominated by large dendroid corals, similar to the reef-crest, and the other with high organism diversity in a micritic matrix and similar to the reef-slope. Within this facies the most important organisms are megalodontid bivalves. Sediment composition changes rapidly, and the primary particles are oncoids, peloids, “lumps,” and various bioclasts. With increasing distance away from the reef, patch-reefs become scarcer and in the eastern lagoon various facies types occur, e.g., grape-stone, foraminiferal-algal, oncolithic, and oolitic. Near the eastern margin of the Steinplatte Platform intertidal algal stromatolites occur, indicating a transition into the Lofer facies of the bedded Dachstein Limestone.This facies interpretation differs widely from that postulated previously, in that a good reef zone is delineated, and the so called fore?reef breccias are now regarded as part of the back-reef sediments. Investigations of adjacent carbonate platforms (Loferer, Leoganger Steinberge, and Steinernes Meer) demonstrate that these areas, which today are isolated by erosion and tectonics, represent the continuation of the shallow water lagoon of the eastern part of the Steinplatte Platform. The bedded Dachstein Limestone of all these platforms developed in Lofer facies with cycles of supra-, inter-, and subtidal members. The supratidal member is charac-terized by green or red marly limestones, the intertidal member by partly dolomitized Loferites (mainly algal stromatolites), and the subtidal member by megalodont limestones with various grain types. In the eastern part of Steinernes Meer the sediments change. Here, limestone was deposited in the subtidal zone and is composed of bioclastic arenites, which are mainly reef derived. The Hochkönig Massif is located eastward of Steinernes Meer and represents a large Dachstein Limestone reef, with a thickness of 700 meters. This reef fringes the carbonate platform on its southeastern edge, with well developed fore-reef breccias towards the basin. Therefore the Stein-platte Reef represents only a small part of an Upper Triassic shallow water carbonate platform, approximately 40 kilometers wide, which was fringed by reefs on the northwestern edge (Steinplatte), and on the southeastern edge (Hochkönig). Whereas the Hochkönig Reef existed throughout almost all of Norian-Rhaetian time, the Steinplatte Reef was initiated only in the uppermost Norian-Rhaetian. During early Norian-Rhaetian time the carbonate plat-form was connected to the land by widespread tidal-flats of the Hauptdolomite, and only when the Kössen Basin separated this land-connected platform did the Steinplatte Reef develop as a relatively small barrier on the margins of the Kössen Sea.

ABSTRACT In the Northern Calcareous Alps of Austria and Bavaria, Upper Triassic reefs are known from the Carnian (parts of the Wetterstein Reefs; Tisovec Limestones), and from the Norian and Rhaetian (Dachstein Reef Limestones; “upper Rhaetian” reef limestones; Kössen coral limestones). The Dachstein reefs developed predominantly on the southern exposed platform edges. The upper Rhaetian Reefs were formed upon shoals within the relatively shallow Kössen Basin (Rötelwand, Feichtenstein, Gruberalm), near the inner boundary of the Dachstein Platform (Stein-platte), or upon the Dachstein Platform (Adnet). Dachstein Reefs and upper Rhaetian Reefs can be compared with respect to their generic and specific composition of the framebuilding biota, but striking differences are evident with regard to constructional types. Upper Rhaetian Reefs seem to have been developed with an initial mud-mound stage followed by a second stage in which an ecological reef formed in the turbulent zone. In the Dachstein Reefs only the second stage appears to be represented, and the distinction between a central reef area (upper reef-crest and reef-flat) with various framebuilding communities, a fore-reef slope with coarse reef breccias, and an extended back-reef area with open and restricted lagoons, is much more pronounced. The organisms involved in the construction of the primary and secondary framework of Upper Triassic reefs consist of sessile foraminifers, segmented and non-segmented calcisponges, hydrozoans, corals, bryozoans, tab-ulozoans, calcareous algae, and many microproblematica. Reef dwelling organisms are vagile foraminifers, bra-chiopods, gastropods, lamellibranches, a few ammonites, serpulids, crustaceans, ostracodes, echinoderms, fishes, reptiles, and some algae. Our knowledge of the reef biota is strongly biased with respect to the framebuilding organisms, which have been studied in great detail during the last few years. The most important framebuilders are corals and calcisponges, followed by hydrozoans and solenoporacean algae. Corals and calcisponges are generally restricted to different parts of the reefs, and in different zones of water energy. A critical review of the reef building organisms from the upper Rhaetian and Dachstein Reefs reveals great difficulties in their systematical treatment, especially corals, “hydrozoans,” bryozoans, and “tabulozoans,” but also clearly indicates the very strong facies control of the reef biota. This facies control is expressed by the unique distributional patterns of the foraminifers, calcareous algae, and the microproblematica, by which different environments (and facies units) can be recognized. Another hint as to facies control is furnished by a rather regular distribution of the secondary framebuilders, and by the zonal distri-butional patterns of the various reef communities. Using distributional patterns and microfacies types of the limestones, 12 “facies units” can be differentiated within the Upper Triassic reef and platform carbonates: these consist of restricted shelf-areas with tidal-flats, open-shelf environments, areas of winnowed edge sands, and reef complexes. The lateral arrangement of these facies units can change depending upon the paleogeographical setting in which the reefs were formed. In spite of some success in understanding upper Rhaetian Reefs, some important questions still have to be resolved. These include the relationships between the Wetterstein Limestone reefs and the Dachstein Limestone reefs, constructional style of the larger Dachstein Reefs, and the evolution of the reef building communities through time. The latter is one of the topics which is presently being studied by the 4'Erlanger Reef Research Group,” comparing Upper Triassic reefs in the Alps with those in Sicily, Solvenia, and Greece.

ABSTRACT An Upper Jurassic (Oxfordian and lower Kimmeridgian) reef complex is well exposed in the area of Slovenia, northwestern Yugoslavia. This reef complex is thought to be a barrier-reef that developed along the shelf-margin of an ancient carbonate platform. From basin to lagoon the following subdivisions have been delineated: a fore-reef area characterized by carbonate breccias and blocks of reef debris; a central reef area with abundant hydrozoans and corals that can be further subdivided into actinostromariid and parastromatoporid zones; and, a back-reef area with locally developed lagoons and patch-reefs defined as the Cladocoropsis zone.

ABSTRACT During Upper Jurassic time (middle-upper Oxfordian) a number of relatively small organic buildups, principally composed of siliceous sponges and algae, developed in the area of southern Germany. This study concentrates on one of these organic structures, the Müllersfelsen buildup (northern Franconian Alb near Streitberg). It is dem-onstrated that the dominant buildup constructional organisms are siliceous sponges, principally of two morphologies (cup-shaped and dish-shaped forms), and cyanophycean algae, which aided in forming the mound configuration. The Müllersfelsen buildup developed during several cyclic stages which occurred in relatively deeper water subtidal depositional environments, without strong current and wave action. Three facies types have been recognized, these are: 1. sponge-crust boundstone facies characterized by micritic boundstone rich in calcified siliceous sponges, tuberoids, and crusts; 2. lithoclastic packstone facies in which spheroidal sedimentary particles (lithoclasts, tu-beroids, and bioclasts) are the dominant grain-supported allochems; and 3. tuberolitic wackestone facies in which mud-supported sedimentary particles are dominant. The spatial distribution of these microfacies indicate that the sponge-crust boundstone facies is the mound constructional facies, whereas both the tuberolitic wackestone and packstone facies are only developed in those areas marginal to the main organic buildup. The uppermost portion of the Müllersfelsen buildup is dolomkized.

ABSTRACT Coral-nidist buildups are known from three outcrop areas of Cretaceous age (Berriasian to Maestrichtian) in France. These are: 1. Paris Basin, 2. Sud-Est Basin, and 3. Aquitaine-Pyrénées Basin. During Berriasian time coral-rudist buildups were limited to the Sud-Est Basin, and here they only occur locally in relation to “Purbecktype” sediments. The Vaianginian Stage corresponds to an extensive phase of marine shallow water carbonate sedimentation containing coral-rudist buildups. These deposits are recorded from both the Jura Subalpine and Provence-Pyrénées Platforms, while isolated coral beds have been reported from the Paris Basin. During the Hauterivian, regional tilting of former carbonate platforms caused a reduction of coral-rudist buildups, nevertheless isolated coral beds have been reported from the Paris Basin. Barremian and lower Aptian times were marked by a considerable extension of platform-type carbonates in the Sud-Est Basin and in the Pyrénées. In these areas “Urgonian” limestones are better represented than coral beds. During the upper Aptian deepening of the Sud-Est Basin led to the disappearance of coral-rudist buildups in most areas, except in the Aquitaine-Pyrénées region. Albian tectonism caused the disappearance of most shallow water carbonates. The Cenomanian transgression followed, leading to reestablishment of coral-rudist buildups, especially in the Aquitaine-Pyrénées and Provence regions. In lower Turonian time another deepening phase occurred and caused the disappearance of shallow water carbonates. During upper Turonian time a new surge of rudist buildups occurred coincident with an increasingly more important influx of terrigenous sediments. Only relatively small carbonate platforms containing lenses of rudists have been recorded from the lower Senonian of the Pyrénées-Provence region. The upper Senonian is mainly a regressive sequence characterized by an extension of deltaic deposits and restriction of coral-rudist lenses primarily to the Aquitaine-Pyrénées Basin. Two groups of coral-rudist formations have been distinguished: 1. those associated with off-shore “highs,” and 2. those associated with carbonate platforms. Three types of off-shore “highs” have been recognized. These are: 1. coral “highs,” known only from the Lower Cretaceous, 2. oobioclastic/coral “highs” from the lower Barremian of the subalpine area, and 3. rudist banks present only in the Upper Cretaceous. We regard “highs” as topographic units of limited lateral extent that can be divided into a small number of ecological and sedimentological zones, and are surrounded by deeper water sediments. Platforms are regarded as morphological units of regional extent composed of several adjacent biofacies and lithofacies related to the hydrodynamic properties of their aquaeous environment, and which may laterally grade into a continental facies. A platform may be subdivided into two zones: 1. an outer zone with high energy deposits and organic buildups (mainly corals in the Lower Cretaceous and corals and rudists in the Upper Cretaceous), and 2. an inner zone of quiet to moderate energy deposits characterized by abundant rudists. Development of coral-rudist formations appears to be governed by six important factors. These are: 1. shallow water conditions, mainly infralittoraJ, 2. relative basement stability (although in some instances tectonism may create “highs” on which organisms may thrive), 3. eustatic stability or transgression, 4. low terrigenous influx, 5. absence of organism restricting océanographie conditions, and 6. a warm climate of tropical to subtropical nature.

ABSTRACT Deposition of Upper Cretaceous carbonate sequences in central Italy (westcentral Latium) appears to be directly related to the tectonic evolution of an epioceanic Central Apennine Platform. From early Cenomanian to late Senonian time organic buildups, along with skeletal shelf-edge deposits, were laid down along the present northwestern margin of the Lepini Mountains, and the southern portion of the Prenestini Mountains. These sediments overlie rocks of the Cretaceous (Aptian-Albian) restricted platform facies. Late Cretaceous shelf-edge deposits are characterized by sequences of rudistid and coral communities laid down within varied depositional settings. The rapid development of these organic communities along a linear tectonically induced shelf-margin caused pronounced increases in the production of bioclastic debris, and the distribution of these sediments both on the marginal slope and in the back-reef areas. This bioclastic debris accumulated in offshore shoals and in tidal banks connecting patch-reefs and organic banks. The continued presence during Cenomanian time of a linear shelf-edge organic buildup complex appears to have been the dominant controlling factor in regards to inner-platform sedimentation. Here, nerineids (gastropods), ostreids (pelecypods), and radiolitid rudistid pelecypod communities, occurring in muddy skeletal wackestones, suggests deposition within both open marine shelf-lagoons and back-reef environments. In addition, the presence of mudstones (some laminated), and peloidal grainstones containing benthonic microfossils, suggests somewhat sheltered shelf-lagoonal to tidal flat depositional settings. Differential tectonism during Turonian time, causing regional sea level fluctuations, produced varied facies patterns due to changes in water circulation and sedimentation over the shelf area. An open marine shelf-lagoon facies with abundant microfossils was widespread during this time. Conditions of sea level fluctuations and influx of clean marine waters onto the platform led to the development of rudistid banks and winnowed skeletal sands along the platform-margin. The tectonism of early Turonian time caused subaerial exposure of the western portion of the Rocca di Cave area, followed by sedimentary progradation. Various changes in overall regional bathymetry, with resultant restriction in water circulation, increased during Senonian time. Isolated platform areas became outer “highs” surrounded by deeper water, although these “highs” were partially covered by shoaling transgressive sediments (Rocca di Cave). In some instances the shelf area was drowned bringing shelf-margin facies into former platform areas, and forming organic shoals and barrier islands during repeated progradation (Lepini Mountains).

ABSTRACT An Upper Cretaceous biolithitic complex exposed at Donje Orešje on Mt. Medvednica, Yugoslavia (northern Croatia), is composed of a central portion designated as a barrier-reef made up of rudistid and coral bioherms. Associated with the barrier-reef are fore-reef and peri-reefal breccias (reef talus) that originated from destruction of the reef-front. This breccia is unsorted, and contains the rubble of reef building organisms and biocalcarenite fragments. The breccia grades into detrital limestones, and more distally, the sediments are basinal hemipelagic and pelagic limestones with conspicuous turbidity features (“Scaglia”-beds). The backreef area contains nerineid (gastropod) biostromes and detrital limestone. The lagoon is mainly represented by clastic terrigenous deposits, through some rudist patch-reefs (“Gösau”-beds) occur rarely. Sporadically, the lagoon also exhibits fresh water characteristics. The reef-flat was successively contaminated by terrigenous clastic material transported from the lagoon, e.g., material derived from erosion on an island arc. The porous reef-frame acted as a barrier, preventing transport of clastic material toward the open sea, but trapping it in the lagoon. Areas with no barrier-reefs, or the areas where the reef was breached or destroyed, turbidity currents could and did deposit flysch-type sediments into the basin. Numerous fossils (rudists, corals, benthic and pelagic foraminifers, and nannoplankton) indicate that the Donje Orešje biolithitic complex is Upper Cretaceous in age (Santonian to lower Campanian). Barrier-reefs of the Donje Orešje type developed in the Upper Cretaceous and lower Paleogene of the Inner Dinarides on the slopes of island arcs. These island arcs and correlative trenches, as well as the inter-arc basins, were formed in a subduction zone of Tethyan oceanic crust beneath the Panonian, e.g., Rhodope Plate. The subduction zone is characterized by the occurrence of ophiolites and mélanges. The Adriatic Plate (the Outer Dinarides) is marked by uniform shallow water carbonate sedimentation (“Carbonate platform”). During its east-ward motion this plate was uplifted at the end of Cretaceous time (“Laramian Orogeny”), and accordingly sedi-mentation reflects regression and bauxite deposition. However, a continuous depositional sequence between Cre-taceous and Paleogene time has been determined for the Inner Dinarides. Apparently, there was not one simple slope between the Outer and Inner Dinarides, with transition from shallow water to basin sediments in the sense of a “classical géosynclinal concept,” but shallow water and basinal facies were successively reestablished due to the influence of island arcs. Distribution of the biolithitic complexes and other Upper Cretaceous facies in regular bands demonstrates that since Cretaceous time there has not been any regionally extended nappes. Such overthrustings would certainly have dislocated the original paleogeographical distribution of Upper Cretaceous facies belts. The main Dinarides “orogenic phase” occurred by the end of the Eocene, when intensive northward and northeastward movement of the African Craton caused a maximal compression and junction of the Adriatic and Panonian Plates. As a consequence, tectonic movements on the plates, as well as in the area of the “oceanic suture” of the Inner Dinarides, brought about the uplift of the Dinarides.