Abstract The comparison of seismic and core data from the western Great Bahama Bank with the exhumed Maiella Platform margin and its adjacent slope in the Apennines of Italy relates the seismic facies to depositional facies and processes. Both platforms evolved similarly from an escarpment-bounded, aggrading platform in the Cretaceous to a prograding platform in the Tertiary. This comparison helps to improve seismic interpretation of isolated carbonate platform systems. Platform interior deposits are typically horizontally layered cycles of shallow-water carbonates, but the seismic sections from Great Bahama Bank are dominated by a chaotic to transparent seismic facies. Synthetic seismic sections of the Maiella Platform margin demonstrate that the chaotic to transparent seismic facies is a product of low-impedance contrasts in the platform carbonates. Both platforms were bounded in the Cretaceous by an escarpment that separated the platform from onlapping basinal and slope sediments. This juxtaposition of facies is recorded in the seismic facies by the lateral change from chaotic platform toinclined continuous reflectionsof the slope. The outcrops of the Maiella Platform margin help assess the processes that formed these escarpments. Small concave scallops and associated megabreccias in the basinal section document episodic erosion during the platform growth, indicating that the escarpment was growing simultaneously with the platform. Both platforms prograde after burial of the escarpment by basinal sediments. On the western margin of the Great Bahama Bank, progradation started in the middle Miocene and advanced the platform margin approximately 25 km westward to its present position. Progradation is documented on the seismic data by clinoform geometry and the expansion of the interpreted platform seismic facies. The prograding system of western Great Bahama Bank consists of sigmoidal clinoforms with foresets that are approximately 600 m high. The foresets are characterized by reflections with variable amplitude and continuity. Discontinuous high-amplitude packages are interrupted by low-amplitude, nearly transparent units of periplatform ooze. Channels of variable size dissect the entire slope but deep incisions with a persistent cut-and-fill geometry occur preferentially at sequence boundaries. These incised submarine canyons are oriented downslope perpendicular to the strike of the platform margin. Most of the gravity-flow deposits bypassed the upper and middle slope and are deposited on the lower slope and on the toe-of-slope. These redeposited carbonates are seismically characterized by discontinuous to chaotic high-amplitude reflections that suggest a heterogeneous environment of depositional lobes. Core data indicate that a tripartite facies succession of slope, reef margin, and platform interior deposits forms the topsets of the prograding clinoforms on Great Bahama Bank. This facies succession is also found in the Maiella Platform margin that prograded across the underlying slope during Eocene time. Synthetic seismic sections show that the reefal units appear as transparent zones on the seismic data, corroborating the calibration made by a core-to-seismic correlation in the Bahamas. Along the Maiella Platform margin, incised slope canyons are exposed, revealing the lithologies of the channel fills. The Maiella canyons are filled with coarse, fining-upward mass gravity-flow deposits that fine upward. The outcropsinthe Gran Sasso area display the heterogeneityof the toe-of-slope environment thatischaracterizedbysmall, amalgamated lobes with feeder channels in largely pelagic background sediment.

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Abstract The close association of serpentinites, basalts and radiolarites, later known as the Steinmann Trinity, was clearly described by Steinmann from the south Pennine Arosa zone and its southern prolongation, the Platta nappe of the eastern Swiss Alps. This classical ‘ophiolite’ is distinctly different from typical fast-spreading ridge associations and can be compared with the transitional crust occurring along non-volcanic passive continental margins in present-day oceans. It includes serpentinized peridotites that we interpret as subcontinental mantle rocks, which were exhumed along low-angle detachment faults and locally overlain by extensional allochthons of continental crust, minor gabbroic intrusions, tholeiitic pillow lavas and flows and a succession of oceanic sediments. The serpentinized peridotites record deformation at falling temperatures during extension leading to final exposure of the mantle rocks at the sea floor and their inclusion in tectonosedimentary breccias (ophicalcites). Field relationships, and mineral-chemical and radiometric data show that the gabbros intruded already serpentinized mantle rocks at shallow depth 161 Ma ago. They are Mg gabbros, Fe gabbros and Fe-Ti gabbros, cut by dioritic pegmatoid veins and albitite dykes, which originated by differentiation from the same parental magma. All gabbros show the same metamorphic evolution, i.e. intrusion at relatively low pressure, oceanic hydration at elevated temperature and a subsequent static oceanic alteration. The pillow lavas stratigraphically overlie the exhumed mantle rocks and the tectono-sedimentary breccias related to the exhumation of both mantle rocks and gabbros. However, both gabbros and pillow basalts are characterized by eNd values typical for an asthenospheric mid-ocean ridge-type source of the melts. They may be the products of a steady process that combined extensional deformation with magma generation and emplacement. They appear to document the onset of sea-floor spreading across an exhumed subcontinental mantle during the earliest phases of a slow-spreading ridge.

Abstract Cenomanian to mid-Campanian rudist lithosomes, exposed along a transect across the Maiella carbonate platform margin (central Apennines, Italy), are described in terms of faunal and matrix composition, geometry, and facies association. On the external platform, the lithosomes reveal a complex geometry and a comparatively high faunal diversity, whereas lithosomes of the inner platform are generally thinner and show a simple, sheet-like geometry. Based on the abundance of lithosomes and of the associated rudist-derived calcarenites, we propose that lithosome formation and, hence, sediment production preferentially occurred on the outermost platform, although the preservation potential of bioconstructions was low in these high-energy environments. Reworking of rudists led to sediment export both towards more internal areas as well as towards the adjacent basin. In contrast, on the inner platform, rudist lithosome formation was restricted by the lack of an adequate substrate and by higher sedimentation rates.

Abstract Carbonate slopes are key areas for correlating shelf and basinal sediments. They provide important clues to the problem of correlation of sequential units on platforms with unconformity-bounded and conformable units on the slope and in the deep basin. This study aims to define packages of genetically related sedimentary units in a base-of-slope succession and to compare them to second-order sequences defined on a nearby carbonate-platform margin. The Lower Cretaceous to Oligocene pelagic and redeposited carbonate sediments, now lithified and exposed in the Gran Sasso d'Italia area, were deposited along the base of slope separating the Lazio-Abruzzi carbonate platform to the southwest and the Maiella platform margin of the Apulia carbonate platform to the southeast from the Umbria-Marche basin to the north. Three major facies types can be distinguished: (1) breccias and megabreccias, containing a large variety of platform- and slope-derived lithoclasts, originating from the collapse of platform-margin areas, and minor skeletal fragments; (2) rurbiditic packstone and grainstone beds, with mainly skeletal fragments and minor amounts of smaller lithoclasts shed from the nearby platforms; and (3) pelagic foraminiferal lime mudstones and wackestones. The interplay of the different sedimentary processes caused changes in facies associations, not only downslope but also along depositional strike. Although slope deposits were reworked, most of the redeposited material was derived from the adjacent platforms and, therefore, provides additional evidence for platform evolution. The sedimentary succession of the Gran Sasso area is subdivided into six formations, separated from each other by unconformities or rapid vertical changes in facies associations. Each of these formations is characterized by a distinct depositional system, which changed drastically across formational boundaries. These changes in depositional system were largely controlled by changes in sedimentary regime that took place on the adjacent platforms and that were related to second-order (10–20 m.y.) platform cycles. The platform cycles were in turn controlled by relative changes in sea level, which in the case of the middle Cretaceous unconformity were related to tectonic events. A comparison of geohistory (i.e., depth vs. time) curves of the Maiella platform-margin, the Gran Sasso base of slope, and the Umbria-Marche basin deposits indicates that platform evolution also appears to have controlled the amount of sediment that accumulated on the base of slope. Along the base of slope, higher sedimentation rates during times of massive redeposition were compensated by periods of submarine erosion and nondeposition, resulting in bulk sedimentation rates comparable to those in the Umbria-Marche basin where pelagic sedimentation was essentially continuous.

Abstract In the central Mediterranean area, a major, second-order transgressive event spanning from the Burdigalian to the Serravallian is recorded by the widespread deposition of deeper-water facies on carbonate shelves and is matched to a large extent by changes in carbonate facies, including the sudden disappearance of corals and coral reefs and the corresponding rise in the abundance of temperate and cool-water carbonate facies. Two sections from the Maiella platform margin in the southern Apennines and the Hyblean Plateau in Sicily provide us with time series based on oxygen and carbon isotopes and detailed biostratigraphic and strontium isotope ages of unprecedented resolution to compare these facies changes to the global Neogene cooling trends and to the paleoceanographic conditions existing at the time in the Mediterranean area. An evaluation of the timing of facies change indicates that the major cooling interval in the Neogene, between 14 and 12 Ma, postdates the change from tropical to temperate carbonate facies in the Mediterranean, which began at approximately 20 Ma. Our oxygen isotope record from the Hyblean Plateau suggests relatively cool temperatures during the Serravallian (within biozones N10-N12) with progressive warming within biozone N11 (11.9–11.8 Ma). This signature is opposite to the one recorded in pelagic sections in other locations of the world and is interpreted to reflect regional conditions within the Mediterranean, as after 20 Ma, the connection to the Indian Ocean became closed or reduced to a very shallow si11, which prevented the outflow and inflow of intermediate and deeper waters. The second-order transgressive event in the central Mediterranean coincides with an increase in the δ 13 C values of skeletal carbonates. These isotope data, combined with biotic evidence, suggest increased productivity of surface waters during the transgressive event. The onset of this event predates by approximately 3 m.y. the major positive carbon isotope excursion recorded worldwide in pelagic sections (the Monterey event); its termination coincides with the end of the Monterey excursion. Our data indicate how variations in water temperatures, coupled with drastic changes in water circulation, severely affected rates of carbonate production during the deposition of a second-order sequence and had the effect of accentuating the transgressive trend within the sequences. Rates of carbonate production reached a minimum during the transgressive and early-highstand systems tracts. This low production was not linked to a decrease in the size of the carbonate-producing area along the depositional ramp but rather to changes in production rates due to environmental change. A better understanding of the response of carbonate facies to paleoceanographic changes needs to be developed, so that these changes can be used to predict sequence stratigraphic architecture in a given time slice and to better estimate the reliability of the sea-level signature preserved in carbonate sequences.

Abstract Sequence and biostratigraphic analysis of the margin of the Apulian carbonate platform in the Montagna della Maiella (central Italy) reveal a platform margin evolution that is controlled by long-term sea-level changes, tectonism and changing platform morphology. The Upper Cretaceous to Miocene strata can be subdivided into six supersequences that are separated by deeply incised truncation surfaces. Biostratigraphy documents a major hiatus for all but one of these boundaries. The supersequences reflect distinct stages of platform development, thus the depositional systems remained the same within each supersequence but changed across the supersequence boundaries. The Apulian platform grew on a passive margin of the Jurassic-Cretaceous (Neo-) Tethys. During the early platform history, subsidence rates decreased exponentially with time and controlled the long-term aggradation potential of the platform. The generally decreasing total subsidence rates permitted the basin in front of the platform to be filled up by the Late Campanian strata (Supersequence [SS] 1), resulting in a change from aggradation to progradation. This enabled slope carbonates of Late Campanian to Late Eocene age (SS 2 to 4 and lower part of SS 5) and finally shallow-water platform carbonates of Late Eocene to Late Miocene age (upper part of SS 5 to SS 6) to prograde basinwards. The supersequence boundaries are to a large extent controlled by long-term (2nd-order) eustatic sea-level changes, but climate and tectonism influenced their duration and expression. Climate, initially tropical to subtropical but temperate in Miocene time, and the respective evolution of flora and fauna were major controls on sequence architecture but did not significantly influence the formation of the supersequence boundaries. The tectonic movements related to Alpine orogeny and foreland basin development were not able to completely obliterate the long-term eustatic signal but greatly enhanced the boundaries, although the exact amount of this influence cannot be assessed. Platform morphology was very influential on sequence architecture. From at least Early Cretaceous to Late Campanian time, the presence of a steep escarpment resulted in detached sequences, consisting of an onlapping basinal part and an aggrading part on the platform top, separated by a bypass slope. In Late Campanian to Oligocene time, a distally steepened slope profile was deeply incised, most pronounced along the platform margin and the upper slope, during 2nd-order sea-level lowstands. Sea-level fluctuations along the gently inclined Miocene shelf resulted in deposition of deepening-upward sequences under conditions of low carbonate productivity.

Abstract Name: Maiella platform Authors: Gregor P. Eberli, Daniel Bernoulli, Diethard Sanders, and Adam Vecsei Location: From 42° 05' to 07' north latitude and 14° 08' to 09' east longitude, provinces of Aquila, Chieti, and Pescara, Italy Geologic time interval: Early Cretaceous-late Miocene Tectonic-sedimentary setting: Southern continental margin of Jurassic-Cretaceous Tethyan ocean, part of large late Tertiary sedimentary decollement nappe of the Southern Apennines, exposed in a broad frontal anticline Basin type: Passive continental margin Paleoclimate: Generally warm and only seasonally humid, some humid intervals (bauxite); paleolatitude was 10° to 30° north Platform type: Part of isolated platform with escarpment Platform geometry: Escarpment changing to low angle slope and distally steepened ramp. Thickness is 2000 m (Lower Cretaceous-upper Miocene). Length exposed north-south is approximately 30 km, probably corner of the large Apulian platform, which is largely buried below Tertiary rocks, approximately more than 400 km (750 km?) long. Width exposed is 10–15 km. Facies and fossils: Cretaceous shallow water platform margin in the south and a pelagic facies (Scaglia) with intercalated gravity flow deposits in the north, separated by an escarpment. Late Cretaceous platform margin rimmed by rudist biostromes (Hippurites and Caprinides) Systems tracts and stacking patterns: Unconformities and exposure surfaces separate sequences; onlap and downlap patterns occur in the sequences. Platform highstand systems tracts composed of aggradational and progradational parasequences with rudist biostromes at the margin. Basin assemblage of pelagic deposits and turbidites (biodetritus) deposited during sea level highstands. Lowstand systems tracts have incised channel fills, small slope fans, and gravity flow deposits. Transgressive systems tracts hard to distinguish from highstand systems tracts.

Abstract The main Alpine-Mediterranean Mesozoic lithofacies, excluding flysch, are outlined and placed in their paleogeographic setting within the broader context of an evolving ocean basin. In the external (ophiolite-free) zones of the Alpine-Mediterranean orogen, Mesozoic pelagic facies almost invariably overlie kilometers-thick successions of Bahamian-type platform carbonates. Wherever the basement of these platform carbonates is exposed, it is continental, comprising low- to high-grade metamorphic rocks and granites. We suggest that the pelagic sediments of these zones were deposited on a deeply submerged continental margin of the Atlantic type. Palinspastic reconstructions of the central Alpine-Mediterranean area place the depositional setting of most of these pelagic facies on the southern continental margin of the Tethys. In this area supply of clastics and organic matter was minimal, thus encouraging pelagic conditions. The earliest pelagic sediments of the Alpine-Mediterranean region are of Triassic age and comprise gray and red limestones or cherts that commonly are associated with volcanics. These sediments were deposited in embayments and basins between extensive carbonate platforms and reefs. During the Liassic Epoch, a phase of block faulting, probably related to rifting in the oceanic Tethys, destroyed many of these shallow-water sites, and pelagic conditions became more widespread. During the Jurassic Period a basin-swell morphology was produced by irregular subsidence of the different blocks. On submarine highs, or seamounts, the following stratigraphically condensed facies were developed: pisolitic ironstones, red biomicrites containing ferro- maganese nodules and crusts, crinoid-pelagic bivalve-gastropod-ammonite biosparites, pelagic pelmicrites and micro-oncolitic sparites, and certain red, fine-grained, nodular limestones. In the neighboring basins, more expanded successions containing slumped blocks and turbidites accumulated; the basinal facies were developed as red, more clay-rich, nodular limestones, gray limestone-marl interbeds, radiolarian cherts, and white nannofossil limestones. The Cretaceous Period saw a smoothing of submarine topography and a general deepening of the water as the continental margin continued to founder. Deposition of varicolored marls and red and white coccolith limestones was widespread. True ocean-floor lithofacies are represented by those rocks associated with, or lying upon, ophiolites. In the central Mediterranean area they comprise ophicalcites, umbers, radiolarites, white nannofossil limestones, and black shales. Their age is Jurassic and Cretaceous. In the western central Atlantic pelagic facies of Late Jurassic and Cretaceous ages occur. These facies resemble both the continental margin and ocean-crust lithologies of the Alpine-Mediterranean Tethys. A section through the Mesozoic portion of this undeformed continental margin and ocean-basin complex comprising the Bahamas, the inter-platform straits, and oceanic realm illustrates a paleogeographic arrangement that strongly resembles the reconstructed section for the Alpine-Mediterranean Tethys. This resemblance illustrates the parallel evolution of these two now widely separated areas, so that they both can be considered as representatives of an east-west Mesozoic seaway, or Tethyan realm, that stretched from the Caribbean to Indonesia.