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Abstract: Twelve cored wells through the Silurian section of the Wabash Platform, Indiana, U.S.A., and 2 non-cored basinal wells with cuttings, were studied to define the sequence stratigraphy of a sediment-starved ramp within a low-latitude epeiric sea during the latest Ordovician icehouse to Silurian greenhouse transition. The Wabash Platform (approximately 200,000km2 area) was bounded to the north by the Michigan Basin, to the east by the Appalachian foreland basin, and passed to the southwest into the Vincennes Basin, which was open to the ocean. Facies developed include: platform-fringing buildups (stromatactis wackestone core, stromatoporoid skeletal wackestone caps and crinoidal rudstone/packstone flank facies); and non-buildup crinoid grainstone–packstone sheets (shoals), skeletal wackestone (variably cherty; between fair weather and storm wave base; deep lagoon and deep ramp) and carbonate mudstone (clean to argillaceous; sub-storm wave base, deep lagoon and deep ramp/basin). The eleven sequences, 2m to 30m thick and 1 to 4m.y. durations (average ∼2.5m.y.), generally can be correlated to global sea-level cycles. The lower three sequences are disconformity-bounded (reflecting moderate ice sheets) but the others are relatively conformable. The most easily mapped regional surfaces are the transgressive surfaces, because the correlative conformities are cryptic. The wide well spacing prevented mapping of lowstand system tracts. The transgressive systems tracts are upward-deepening, upward-fining carbonate units, that become more argillaceous and silty upward. The highstand systems tracts are upward-coarsening carbonate mudstone to wackestone–packstone and rare grainstone. Barrier bank complexes and isolated buildups aggraded during deposition of the upper 4 sequences to form a discontinuous raised rim (∼40m relief) to the ramp while the interior of the platform remained sediment starved. Subsidence rates in the basin were very low (0.6 to 1.2cm/k.y.), but the low platform accumulation rates (0.2cm/k.y. to 0.8cm/k.y.) prevented the seafloor from building to sea level in all but the lower three sequences and later over barrier banks (accumulation rates 2cm/k.y.). Parasequence development in high-accommodation settings elsewhere in the Silurian in North America records transition from moderate ice-sheets to an ice-free world. This is weakly expressed on the Wabash Platform due to the dominantly deeper subtidal setting. The remarkably low sedimentation rates resulted from the epeiric sea being isolated from the open ocean, and they likely are typical of the large epeiric seas of the Paleozoic. [Copyright &y& Elsevier]

The internal facies and sequence architecture of a Late Jurassic (Late Kimmeridgian) shallow carbonate ramp was reconstructed after the analysis and correlation of 17 logs located south of Teruel (northeast Spain). The studied rocks are arranged in five high-frequency sequences A–E (5–26 m thick) bounded by discontinuities traceable across the entire study area (20 × 25 km). Facies analysis across these sequences resulted in the reconstruction of three sedimentary models showing the transition from interior ramp environments (i.e., lagoon, backshoal, and shoal) to the progressively deeper foreshoal and offshore areas. Coral-microbial reefs (meter-sized patch and pinnacle reefs) have a variable development throughout the sequences, mostly in the foreshoal and offshore-proximal environments. The preferential occurrence and down-dip gradation of non-skeletal carbonate grains has been evaluated across the three models: low-energy peloidal-dominated, intermittent high-energy oolitic-dominated and high-energy oolitic–oncolitic dominated. The predominance of these non-skeletal grains in the shoal facies was mainly controlled by the hydrodynamic conditions and spatial heterogeneity of terrigenous input. The models illustrate particular cases of down-dip size-decrease of the resedimented grains (ooids, peloids, oncoids) due to storm-induced density flows. Offshore coarsening of certain particles (intraclasts, oncoids) is locally observed in the mid-ramp areas favorable for microbial activity, involving coral-microbial reef and oncoid development. The observed facies variations can be applicable to carbonate platforms including similar non-skeletal components, where outcrop conditions make the recognition of their three-dimensional distribution difficult. [ABSTRACT FROM AUTHOR]

Detailed litho- and biofacies investigations of the Lower–Middle Cambrian carbonate Láncara Formation resulted in its subdivision into nine lithofacies types: (1) claystone, (2) recrystallized mudstone, (3) laminated mudstone with laminoid-fenestral fabrics, (4) stromatolite, (5) laminated aggregate grainstone, (6) non-laminated aggregate grainstone, (7) oolitic-bioclastic floatstone, (8) echinodermal packstone, and (9) bioclastic grainstone. The thicknesses of lithofacies 1–7 (lower member of the Láncara Formation) decrease from south to north. Lithofacies types 8–9 (upper member of the Láncara Formation) are characterized by similar thicknesses and low facies and faunal gradients and are thus indicative of deposition on a carbonate ramp. From palaeoecological, palaeo(bio)geographical, palaeomagnetic, and tectonic considerations, the depositional environment of the Láncara Formation is re-interpreted as an eastward/north-eastward sloping, low morphology carbonate ramp. The Cantabrian Zone, with a primary lateral extension of about 300 km, is further construed to be an element of a widespread and connected, discontinuous drowned Perigondwanan depositional system. [ABSTRACT FROM AUTHOR]

The Oligocene represents a key interval during which coralline algae became dominant on carbonate ramps and luxuriant coral reefs emerged on a global scale. So far, few studies have considered the impact that these early reefs had on ramp development. Consequently, this study aimed at presenting a high-resolution analysis of the Attard Member of the Lower Coralline Limestone Formation (Late Oligocene, Malta) in order to decipher the internal and external factors controlling the architecture of a typical Late Oligocene platform. Excellent exposures of the Lower Coralline Limestone Formation occurring along continuous outcrops adjacent to the Victoria Lines Fault reveal in detail the three-dimensional distribution of the reef-associated facies. A total of four sedimentary facies have been recognized and are grouped into two depositional environments that correspond to the inner and middle carbonate ramp. The inner ramp was characterized by a very high-energy, shallow-water setting, influenced by tide and wave processes. This setting passed downslope into an inner-ramp depositional environment which was colonized by seagrass and interfingered with adjacent areas containing scattered corals. The middle ramp lithofacies were deposited in the oligophotic zone, the sediments being generated from combined in situ production and sediments swept from the shallower inner ramp by currents. Compositional characteristics and facies distributions of the Attard ramp are more similar to the Miocene ramps than to those of the Eocene. An important factor controlling this similarity may be the expansion of the seagrass colonization within the euphotic zone. This expansion may have commenced in the Late Oligocene and was associated with a concomitant reduction in the aerial extent of the larger benthonic foraminifera facies. Stacking-pattern analysis shows that the depositional units (parasequences) at the study section are arranged into transgressive–regressive facies cycles. This cyclicity is superimposed on the overall regressive phase recorded by the Attard succession. Furthermore, a minor highstand (correlated with the Ru4/Ch1 sequence) and subsequent minor lowstand (Ch2 sequence) have been recognized. The biota assemblages of the Attard Member suggest that carbonate sedimentation took place in subtropical waters and oligotrophic to slightly mesotrophic conditions. The apparent low capacity of corals to form wave-resistant reef structures is considered to have been a significant factor affecting substrate stability at this time. The resulting lack of resistant mid-ramp reef frameworks left this zone exposed to wave and storm activity, thereby encouraging the widespread development of coralline algal associations dominated by rhodoliths. [ABSTRACT FROM AUTHOR]

The Mesozoic sedimentary cover belonging to the Monte Carmo-Rialto unit of the Ligurian Briançonnais domain is composed of Scythian clastics and Anisian to Carnian carbonate rocks over 300 m thick. This paper focuses on the stratigraphy of this carbonate complex, its environmental significance, and its evolution in light of dynamic stratigraphy. Our facies analysis of limestones and dolomites of the Triassic complex allowed us to reconstruct an environmental model. Data support a distally steepened carbonate ramp of Anisian age evolving to a more diversified Ladinian platform with an oolitic sand-bar belt separating the lagoon from the slope. The Monte Carmo-Rialto slope facies are the only witnesses of deep sedimentation in the Triassic terrains of the Ligurian Briançonnais domain, otherwise represented by shallow-water carbonate deposits. On the basis of facies succession, we have identified nine medium-scale cycles (third-order sequences) in the study area, comparable to those evidenced in the Briançonnais s.s. domain by the French authors. Small-scale cycles analysis evidenced mainly shallowing-upward trends in the examined sequences; although a few evidences of transgression-related deposits (deepening upward cycles) have been found at the base three sequences, they have been mostly obliterated by dolomitization and masked by local tectonics. For this reason, we can undoubtedly distinguish only the part of each sequence belonging to HST, while the TST, though present, still remains a partition that cannot be precisely characterized. In the same way, LSTs are not present in the Monte Carmo-Rialto unit, due to the original relative landward position of the examined area. Sequence stratigraphy analysis indicates different long-term dynamics for the two evolutionary stages of the Triassic Ligurian platform: a general landward backstepping to moderate progradation during the Early Anisian and true progradation during the latest Anisian and Ladinian. In addition, a good fit with the sequences proposed by the SEPM chart has been found, indicating a correspondence for the third-order sequences of the Middle Triassic. [ABSTRACT FROM AUTHOR]

The Campanian to Maastrichtian Aruma Formation represents a distinctive depositional system of the carbonate-dominated ramp along the Arabian plate. Sedimentologic characteristics and stratigraphic relations are integrated with carbon and oxygen stable-isotope data to interpret the depositional environments in a sequence stratigraphic framework. One siliciclastic facies association (FA1) and eight carbonate microfacies (MF 1–8) belonging to four facies belts (FB1–4) were identified. Facies characteristics support accumulations on a carbonate ramp environment that extends from offshore/outer ramp to middle and inner ramp settings. Stable-isotope data are correlated to the oscillating global sea-level curve and global excursions' events in order to refine the sequence stratigraphy of the Aruma Formation. Carbon-isotope chemostratigraphy shows remarkable long-time excursions, which are correlated to the two global negative excursions (Late Campanian event "LCE" and Campanian–Maastrichtian boundary event "CMBE") as well as the positive δ13 C excursion of Middle Maastrichtian event "MME" and the uppermost negative δ13 C excursion toward the K–Pg boundary. The negative shift in the δ13 C values associated with relatively positive values in the δ18 O herald three marked sea-level falls, which can be coincided with global sequence boundaries. The merged surfaces TS1/SB1 and TS2/SB2 can be correlated to the Campanian events KCa3 (80 Ma) and KCa6 (75.4 Ma), respectively. The coplanar surface TS3/SB3 matches well with the Maastrichtian event KMa3 (69.4 Ma). The positive values of δ13 C and/or negative values of δ18 O coincide with periods of maximum transgressions. The minor pulses are mostly attributed to cyclic fourth-order sequences. The established sequence stratigraphic architecture and depositional model of the outcrop data herein will be useful in regional correlations with analogous subsurface successions along the Arabian plate and enhancement of potential petroleum explorations. • Facies analysis shows that the Aruma Fm was deposited on a regional carbonate ramp. • Chemostratigraphy reveals remarkable excursions, coinciding with the K2 global events. • Late Campanian to Middle Maastrichtian "LCE, CMBE and MME" events were documented. • Aruma Fm (second-order sequence) comprises three main third-order sequences. • The reported sequences herald Campanian to Maastrichtian global sea-level pulsations. [ABSTRACT FROM AUTHOR]

Abstract: Photozoan and heterozoan skeletal assemblages are controlled by their trophic requirements (i.e. light-based photosynthesis versus other sources) and temperature. Photozoan associations tend to dominate tropical and subtropical waters, whereas heterozoan carbonate systems tend to occur in cooler waters and in localised areas that are affected by nutrient-rich upwelling or terrestrial runoff. Because of the wide climatic spectrum in which heterozoan carbonates are found, their interpretation is often problematic. We present a high-resolution analysis of the Attard Member of the Lower Coralline Limestone Formation (Upper Oligocene, Malta). The biotic associations and palaeolatitudinal reconstructions suggest that carbonate sedimentation took place in tropical waters under oligotrophic conditions. An important factor controlling the spread of heterozoan assemblages in the Late Oligocene of Malta seems to be related to the palaeoecology and evolution of zooxanthellate. The limited capacity of corals to thrive in high-light conditions and to form a wave-resistant reef promoted the diffusion of heterozoan assemblages. [Copyright &y& Elsevier]

Abstract: The sedimentary succession of the southern Amanos Mountains, bordering the eastern margin of the Karasu Rift in south central Turkey, provides a record of environmental change from the Eocene (Lutetian) to the Upper Miocene (Tortonian) that charts the final evolution of the northern margin of the Arabian plate prior to and during continental collision. Eocene shallow-marine carbonates (Hacıdağı Formation) are interpreted as the youngest unit of the Arabian passive margin succession deposited on a northwards facing carbonate ramp. Subsequent deformation and uplift took place during the Oligocene represented by folding of the Eocene and older strata. This is interpreted to be the result of initial continental collision between Arabia and Eurasia. Unconformably overlying the Eocene limestone are Lower Miocene conglomerates, sandstones and palaeosols up to 150 m thick (Kıcı Formation). These were deposited in a range of marginal marine settings consisting of alluvial fan/fan delta facies, flood plain as well as basinal facies. Subsequently, during the Middle Miocene, local patch reefs developed in restricted areas (Kepez Formation) followed by Upper Miocene sediments (Gökdere Formation) composed of relatively deep water hemipelagic marl, with clastic interbeds, which represent a transgression during this period. The Upper Miocene becomes sandier upwards, this records the regression from the relatively deep water facies to coastal sediments. Water depth gradually became shallower until during Pliocene time the area became continental in nature. By the Quaternary rifting had resulted in the development of the Karasu Rift with active alluvial fans along the margins and braided rivers depositing coarse conglomerates in the axial zone. These conglomerates are interbedded with basaltic lava flows that resulted from the region extension across the area. This research shows that initial continental collision occurred in this area after the Lutetian (40.4 Ma) and before the Aquitanian (23.03 Ma) supporting the hypothesis that the southern Neotethys Ocean closed during the Late Eocene to Oligocene. This was a time of climatic change including the onset of southern hemisphere glaciation, in which the closure of the southern Neotethys may have had played an important role. [Copyright &y& Elsevier]

Abstract: Study of four closely-spaced El Garia Formation reservoirs (offshore Tunisia) has identified diagenetic controls on variation in reservoir quality. The Ashtart, Didon and Zarat Fields have been affected by significant dissolution porosity, which occurred during burial diagenesis, with vuggy pores preferentially forming in micritic sediment. However, inter-crystalline porosity due to dolomitisation is the principal control on reservoir quality in the Hasdrubal Field. This spatial variation in porosity type reflects, to some extent, the structural and sedimentological isolation of Hasdrubal within the facies trend, surrounded by deep water embayments and, unlike the other studied fields, not directly underlain by salt diapirs. Burial corrosion appears to have formed where mid to outer ramp, mud-rich El Garia Formation facies directly overlie salt domes, a consequence of the circulation of aggressive fluids related to increased heat flow above the salt. Inorganic CO2, focused into the reservoir prior to hydrocarbon emplacement by faults related to salt movement, is the most likely candidate responsible for the burial dissolution porosity observed in the Ashtart, Didon and Zarat fields. A salt diapir does underlie the most basinward (north-east) margin of Hasdrubal, and minor dissolution porosity is present, but we conclude that the absence of significant dissolution in Hasdrubal is due to its offset position, away from the highly faulted roof zone immediately above the salt. Although we favour this model, we cannot rule out that the absence of dissolution porosity in Hasdrubal may reflect the early emplacement of hydrocarbons from an older (non-Bou Dabbous Formation) source, or differences in the timing of salt movement and consequent fault creation below Hasdrubal compared to the other fields, local temperature and/or acid concentration effects, or a different source of CO2. Differences in the distribution of dissolution porosity in the Ashtart, Didon and Zarat Fields may be related to the presence of intra-reservoir permeability barriers, due to increased nummulithoclastic (= fragmented Nummulites) content. This may also explain the strata-bound nature of the dolomite in Hasdrubal, which, like the dissolution porosity in Ashtart, is overlain by sediments with an increased nummulithoclastic content. Although dolomite is present in variable quantities in all of the studied fields, the significant volume of dolomite in Hasdrubal may reflect a local ‘plumbing’ effect, with dolomitising fluids entering the reservoir via a fault network that does not affect the other fields. [Copyright &y& Elsevier]

Abstract: Calciclastic submarine fans are rare in the stratigraphic record and no bona fide present-day analogue has been described to date. Possibly because of that, and although calciclastic submarine fans have long intrigued deep-water carbonate sedimentologists, they have largely been overlooked by the academic and industrial communities. To fill this gap we have compiled and critically reviewed the existing sedimentological literature on calciclastic submarine fans, thus offering an updated view of this type of carbonate slope sedimentary system. Calciclastic submarine fans range in length from just a few to more than 100 km. Three different types can be distinguished: (1) Coarse-grained, small-sized (<10 km) fans, which are characterized by the abundance of calcirudites and the scarcity of mud. They have relatively long leveed channels and small radial lobes. (2) Medium-grained, medium-sized fans are typified by the abundance of calcarenites and lesser amounts of calcirudites and mud. They have a tributary network of slope gullies, which merge to form a leveed channel that opens to the main depositional site, characterized by extensive lobes and/or sheets, which eventually pass into basinal deposits through a narrow fan-fringe area. These fans are between 10 and 35 km in length. (3) Fine-grained, large-sized fans are rich in calcarenites and mud, but poor in calcirudites. They have wide and long slope channels that feed very extensive calciturbiditic sheets, the total length always exceeding 50 km and generally being close to 100 km. In terms of grain-size distribution the three fan types compare well with sand/gravel-rich, mud/sand-rich and mud-rich siliciclastic submarine fans, respectively. However, they show notable differences in terms of size and sedimentary architecture, a reflection of the different behaviour of their respective sediment gravity flows. Most calciclastic submarine fans were formed on low-angle slopes and were sourced from distally steepened carbonate ramps subjected to high-energy currents. Under these conditions shallow-water loose grainy sediments were transferred to the ramp slope and eventually funnelled into the submarine fan by sediment gravity flows. These conditions seem to have been more easily met on leeward margins in which the formation of reefs was hampered by cool waters, nutrient enrichment or oligophoty. Another circumstance that contributes to the transfer of shallow-water sediments to the distal ramp slope is a low sea level, forcing the carbonate factory closer to the slope break and destabilizing sediments by increased pore-water pressure. However, the most important factor controlling the development of calciclastic submarine fans was the existence of an efficient funnelling mechanism forcing sediment gravity flows to merge downslope and build up a point-sourced sedimentary accumulation. In most cases this occurred through a major slope depression associated with tectonic structures, an inherited topography, or large-scale mass failures. [Copyright &y& Elsevier]

Abstract: In eastern Sardinia, the first Jurassic sedimentary cycle (Bajocian–Kimmeridgian) develops in response to the opening of the Alpine Tethys Ocean. Starting during the Bajocian (Middle Jurassic), over a horst-and-graben system initially drowning to the northeast, at first siliciclastic sediments take place, related to continental to transitional environments. In time, they are gradually followed by marine carbonate, assigned to inner to outer ramp deposits. Afterwards, the latter, in their turn, become shallow; they are newly covered with an inner ramp lithofacies. The Kimmeridgian–Tithonian unconformity ends the cycle. Therefore, this sedimentary cycle as a whole can be interpreted as a transgressive–regressive megasequence linked to tectono-eustatic factors. All the pertaining stratigraphic units have been included within the ‘Baunei Group’, newly described. A comparison with the neighbouring areas, with particular regards to the Jurassic series of the Corsica, has been made, attempting to improve the reconstruction of this part of the Tethyan Ocean Western margin. [Copyright &y& Elsevier]

Abstract: Analyses of facies associations and biotic assemblages integrated with backstripping analysis are presented to improve understanding of the development of a shallow water Miocene carbonate ramp in the Central Apennines (Italy), with special reference to the relationships between tectonic subsidence and the internal architecture of the ramp. Subsidence curves were calculated for six measured sections located in different sectors of the platform. Dating is derived from Sr isotope analyses (from previous studies) and regional correlations. Corrections for eustasy and paleobathymetry were deduced from biota and facies analyses. The subsidence curves show rates that vary both in space and time. By analysing the vertical motions in different sectors of the ramp over a fixed time span (Burdigalian to Tortonian), it was possible to evaluate the control on platform architecture exerted by tectonically induced changes in sea-floor bathymetry and highlight the effects of tectonic migration. Most analysed sites experienced a short period of tectonic uplift or stability followed by a period of slow subsidence. This preceded increased subsidence which resulted in drowning of the shallow-water carbonate platform. The stability/uplift is progressively younger towards the north-eastern sectors that correspond to progressively more external zones of the foreland relative to the Apenninic orogenic belt. The subsequent drowning is related to the diachronous down-flexure of the Adriatic lithosphere due to its eastward retreating subduction under the Apennines. The small magnitude of the uplift suggests that the formation of a foreland bulge due to subduction-related flexure of the Adriatic plate was probably not the responsible mechanism. Hence, this uplift is related to the development of proto-thrusts or to the propagation of compressive stresses in the foreland. These vertical motions influenced the geometry of the platform during the 17.5–16 Ma stage. During this period the platform was characterised by exceptional progradation of the bryomol-dominated proximal outer ramp facies belt. This rapid spreading may be induced by the combined effect of increased eutrophic conditions and a contemporaneous decrease in the sea-floor bathymetry resulting from the tectonic uplift. From the Tortonian onwards, when the platform became involved in the eastward migrating foredeep system, the tectonic subsidence curve records a short period of fast tectonic subsidence rates followed by a period of slow subsidence or slight uplift during basin drowning and infilling, respectively. [Copyright &y& Elsevier]

Abstract: The correspondence analysis used in the present study, which consists of a semiquantitative approach, tries to reconstitute a model showing a facies organisation in different parts of a carbonate ramp. As an example, we studied the Lower–Middle Turonian carbonates outcropping in central Tunisia (jebel Bireno). The whole components of the carbonate facies are represented on the axis where the repartition of allochems may express a gradient from the shoreline (negative part of the axis 1) to deeper marine environments (positive part of the axis 1). In the proposed model, the position of the different samples along this axis may express pulsations that are related to proximal–distal or regressive–transgressive evolutions. [Copyright &y& Elsevier]

Abstract: During the Middle Triassic, a broad carbonate ramp developed at the western end of the Tethys Ocean. In the early phase of the ramp evolution dark grey or black, finely crystalline carbonates were deposited over a considerable part of the ramp. In the Aggtelek Karst, northeastern Hungary, carbonates of the Aggtelek facies of the Silica Nappe are exposed. In the latest Early Triassic, bioturbated mudstones–wackestones and occasionally packstones were formed in the outer ramp zone below the storm wave-base. During the Early Anisian, oxygen-depleted bottom conditions evolved. Gradual changes took place in the sedimentary features of mud-dominated deposits that is attributed to increasing oxygen depletion as a result of density stratification of seawater in the deeper ramp areas. Remarkable ecological and sedimentary changes began with the colonisation by sponges and microbes in the Aggtelek facies area that occurred coevally with a relative sea-level fall. The appearance of the foraminifer Glomospira densa points to late Early Anisian age for these changes. This unit is very variable in lithology and facies compared to the monotonous development of the lower units. Massive limestones and dolomites of microbial origin are ubiquitous; additionally, oolites with micro-oncoids, cross-bedded and cross-laminated bioclastic, peloidal packstones–grainstones, thin-bedded bioclastic wackestones–mudstones, laminated and brecciated dolomites with evaporite pseudomorphs, and dolocretes are also present. Specific microfacies types, i.e. automicrite (varicoloured micrite–microspar groundmass) and cuneiform spongy microfabric preserved by cryptic microbial films, are recognised and interpreted as sponge–microbe mud-mound deposits. The microfacies of pilot samples from Northern Calcareous Alps, Inner Western Carpathians and Dinarides exhibit similar sedimentary features. Tectonic setting, biota evolution after the end-Permian mass extinction, relative sea-level changes and hypersalinity may have been the most important controlling factors of the non-skeletal carbonate factory, which produced dark grey mud-dominated deposits. [Copyright &y& Elsevier]

Abstract: This paper provides new data on the Cenomanian (Late Cretaceous) carbonates in Lebanon, which, due to their location and considerable thickness, represent an important segment of the broader Eastern Mediterranean platform. Detailed field and microfacies investigations have shown that the Late Albian–Cenomanian succession (i.e., the Sannine Formation in Lebanon) consists of a number of lithologically distinct strata. These are: micritic limestone, silicified micrite, bioclastic limestone, chalky limestone (foraminifera-wackestone), marl and marly limestone, dolostone and dolomitic limestone. The laminated micritic limestones are typically associated with chert nodules and bands, and are interpreted to have been deposited in deep marine environments. The bioclastic limestones have abundant skeletal fragments suggesting deposition in relatively shallow marine settings, an interpretation that is further supported by the presence of local palaeo-channels within the limestones. Geochemically, the formation includes five distinct chemical groups, each characterized by certain chemical traits reflecting the lithological nature of the various facies. The micritic limestones have relatively low concentrations of most major and trace elements (Mg, Sr, Si, Al, K, P, Ti and Rb). In sharp contrast, the marly limestone samples have the highest concentrations of most of these elements. The silicified micrites have a wide range of Si and Sr contents, but abundances of most elements are intermediate between those of the micritic limestones and the marly limestones. The chalky limestones have relatively low Si and Al, but relatively high P contents. The dolomitic limestones have the lowest Rb and Sr concentrations. The normalized REE patterns of representative samples of most of these rocks are parallel to subparallel and nearly flat. Based on facies analysis and chemical traits, we have constructed a carbonate platform ramp model for this succession, in which the dolostones and marly limestones were deposited in back ramp to subtidal environments, the bioclastic limestones accumulated in shallow, wave-dominated to deep ramp environment, and the micritic limestones and silicified micrites formed in a deep ramp environment. This ramp was influenced by sea-level fluctuations and tectonic activities. The proposed model has wider implications for the geodynamic evolution of the eastern Mediterranean region during the Cretaceous Period, and is consistent with interpretations of some other tectonically active margins worldwide. [Copyright &y& Elsevier]

In the locality of Colle (Cantabrian Zone, NW Spain), the upper part of the Valporquero Shale Formation (Emsian, La Vid Group) contains an interval of shales and marlstones (barren, greenish-grey shales and fossiliferous, greenish-grey or reddish shales/marlstones) with beds and packages of homogeneous and cross-bedded skeletal limestones. Metre-scale mud mounds and coral biostromes occur encased in the fossiliferous reddish and greenish-grey shale/marlstones, respectively, with the coral biostromes overlying conspicuous skeletal limestone bodies. These rocks were deposited on a carbonate ramp, ranging from above storm wave base for the cross-bedded skeletal limestones to below the storm wave base for the remaining deposits, organic buildups included. The vertical stacking of these facies and the occurrence of the two types of buildups are interpreted to reflect the interplay among several (possibly 4th and 5th) orders of relative sea-level variations, during a 3rd-order highstand. Coral biostromes occur in early 5th-order transgressive system tracts developed within late 4th-order highstand, and are interpreted to have thrived on a stable granular substrate (skeletal limestones) in non-turbid waters, being later aborted by the onset of muddy sedimentation. Biostrome features suggest that they developed under environmental conditions essentially different from those related to the sedimentation of their granular substrate. Mud mounds occur in 5th-order transgressive and early highstand system tracts tied to early 4th-order sea-level rise. Field relationships suggest that mud mounds grew coevally with muddy sedimentation, with high-frequency variations in carbonate vs. terrigenous mud sedimentation influencing their development. [ABSTRACT FROM AUTHOR]

Carbonate mud that accumulated in the deep parts of a late Kimmeridgian carbonate ramp (Iberian Basin, NE Spain) was partly derived by resedimentation from shallow water production areas. High-frequency sea-level changes, probably driven by climatic changes in tune with precession and short-eccentricity cycles, affected carbonate production and the amount of exported sediment. Facies analysis and correlation of three outcrops located in middle and outer ramp settings allows a comparison of high-order sequences (bundles of beds and sets of bundles) across a ramp transect and an assessment of the carbonate factory. Analysis of the storm deposits found in middle ramp settings identifies deepening to shallowing high-frequency cycles based on the level of exported carbonate. In outer ramp areas, many of the bundles exhibit a thinning trend, indicating a progressive decrease of carbonate production and hence, carbonate export during periods of high-frequency sea-level rise. δ13Ccarb values show a gradual increase through the studied long-term transgressive interval ranging from 1·5‰ to 2·8‰. Within this long-term evolutionary trend, short-term δ13Ccarb fluctuations occur that correspond with some of the high-order cycles defined from sedimentary facies analysis. These short-term δ13Ccarb shifts are interpreted as shifts in carbonate export from shallow reef regions to the outer ramp. A consequence of this study is that variation in δ13Ccarb can be used for correlation in outer ramp successions, at least on a basin-wide scale. [ABSTRACT FROM AUTHOR]

Abstract: Lower Tortonian distally steepened carbonate ramp of Menorca mostly consists of foramol and rhodalgal facies deposited in inner-middle ramp, ramp slope and outer ramp settings. Red algae are abundant from the middle ramp to the lower part of the slope and their taxonomic assemblages are clearly related to the bathymetric position. Melobesioids percentage increases basinward, passing from 55.8% in the middle ramp to 97% in the toe of slope. Mastophoroids are more abundant in the middle ramp (43.1%) and decrease toward deeper paleoenvironments (1.2%). Lithophylloids and sporolithaceans appear as accessory components from the middle ramp to slope settings. The percentage of melobesioids and mastophoroids observed in the middle ramp suggest that growth of the rhodoliths started in a water depth below 10–20 m. The deepest occurrence of the rhodoliths is in the ramp slope environment, where the dominance of melobesioids and the low percentage of shallower-water subfamily suggests a water depth range of 70 to 100 m. Shape and structure of rhodoliths are indicative of high-energy conditions in all ramp settings and they do not reflect a decrease in hydrodynamic energy related to water depth increase. These conditions are related to the presence of unidirectional currents that produced cross-bedded grainstones existing in the middle ramp, ramp slope and at the toe of the ramp slope settings. The high percentage of mastophoroids in the shallowest environments and the presence of Lithoporella and Sporolithon in the coralline assemblages suggests that carbonate production took place in tropical waters. [Copyright &y& Elsevier]

The Buah Formation is a carbonate unit of late Neoproterozoic age, exposed in the Jabal Akhdar of northern Oman and the Huqf region of central Oman. The Buah Formation is interpreted as a distally steepened storm-dominated ramp, containing inner ramp tidally influenced oolitic shoal and back-shoal lagoon facies and storm-dominated mid ramp facies. A slope break separates mid-ramp facies from outer ramp facies characterized by accumulation of redeposited carbonates on gently inclined slopes (1–2 degrees). Combined facies stacking patterns and outcrop correlation via δ13C profiles suggest that Buah carbonates formed as a highstand systems tract characterized by a general upward shallowing of facies and strong lateral progradation. On a regional scale, Buah facies distributions across Oman were controlled by the presence of basement highs defining areas of reduced subsidence, which promoted lateral progradation of the Buah carbonate ramp for tens of kilometers, while the faster-subsiding areas became sites of deep-water deposition. [ABSTRACT FROM AUTHOR]

The presence of foramol, rhodalgal and bryomol skeletal grain associations in ancient shallow-marine limestones is commonly interpreted as evidence for non-tropical palaeoclimate, despite temperature being only one of several factors influencing skeletal grain associations. Such interpretations neglect the multitude of factors other than temperature that influence carbonate-producing biota. These include nutrients, water energy, water transparency, depth of the sea floor, salinity, oxygen, Ca2+ and CO2 concentrations, Mg/Ca ratio, alkalinity, substrate requirements, competitive displacement as well as biological and evolutionary trends. This uniformitarian approach also disregards the probability that conditions of present-day biological systems may not be representative of past conditions of analogous systems. Here, the importance of considering these other factors is illustrated through two examples of carbonate platforms in the western Mediterranean. These platforms are dominated by foramol, rhodalgal and bryomol associations of Miocene age in spite of having formed in tropical conditions. The platforms discussed are: (1) the Lower Tortonian ramp on Menorca, Balearic Islands; and (2) the Lower–Middle Miocene ramps of the central Apennines, Italy. Evidence for tropical conditions in the Mediterranean during the period of growth of these platforms is provided by species of red algae and larger foraminifera, by data from coeval continental basins and by global oxygen isotope data. [ABSTRACT FROM AUTHOR]

The northern Sinai Upper Aptian to Middle Cenomanian succession represents an example of a carbonate platform, where stratigraphic interpretations are mainly based on benthic foraminifera, ostracods and rudists. This paper presents a concept combining the stratigraphic study of benthic organisms with graphic correlation and sequence stratigraphy, at a scale that determines the timing of sequence boundaries and quantification of sediment-accumulation rates. Biostratigraphic analyses result in multibiostratigraphic zonations and contribute to a northern Sinai fossil range chart for benthic larger and smaller foraminifera, ostracods and rudists. The age interpretation results from the careful comparison of the ages given in the literature and the distribution patterns in the northern Sinai sections. The northern Sinai chart for many fossil ranges matches with other studies, but also indicates some exceptions. Ostracods were grouped into assemblages characterised by short local ranges, which enables the exact correlation of different sections. The use of graphic correlation techniques within this framework improves the stratigraphic resolution and results in timing of the sequence boundaries. These chronostratigraphic assignments allow comparison of the Sinai sequence boundaries with those described from other regions. Furthermore, graphic correlation measures long-term sediment-accumulation rates of the northern Sinai. Based on their variations, we calculate the relative sea-level changes, resulting in a detailed second-order sea-level curve. In the Upper Aptian to Middle Cenomanian succession, important changes in the long-term sediment-accumulation rate were measured. They reflect three second-order sea-level cycles, which subdivide a general relative sea-level rise. 18 sequences superimpose the second-order sea-level change: 3 sequences in the Upper Aptian, 11 sequences in the Albian, and 4 sequences in the Lower–Middle Cenomanian. Both sequence-stratigraphic patterns and long-term sea-level changes were compared with those from the Tethyan domain, the African/Arabian Plate and the western Pacific. Abundance and distribution of the Sinai sequence boundaries were similar to the patterns described from other regions. We distinguish between sequence boundaries with regional extent correlating with examples from the North African/Arabian Plate or the western Pacific, sequence boundaries of possibly global or Tethyan extent and the few sequence boundaries of local extent. The influence of the regional and global signals on the studied successions reflect the Sinai location between the southeastern and southwestern Tethyan realms. Local tectonics or changes in subsidence are only of subordinate importance for the creation of sequence boundaries. The comparison of the chronostratigraphic assignments of the second-order sea-level curve with other descriptions indicates a second-order relative sea-level history of its own for Sinai triggered by the interaction of subsidence, sediment supply and eustasy. [Copyright &y& Elsevier]

This paper provides an overview for this special publication on the geologic framework of the inner shelf and coastal zone of west-central Florida. This is a significant geologic setting in that it lies at the center of an ancient carbonate platform facing an enormous ramp that has exerted large-scale control on coastal geomorphology, the availability of sediments, and the level of wave energy. In order to understand the Holocene geologic history of this depositional system, a regional study defined by natural boundaries (north end of a barrier island to the apex of a headland) was undertaken by a group of government and university coastal geologists using a wide variety of laboratory and field techniques. It is the purpose of this introductory paper to define the character of this coastal/inner shelf system, provide a historical geologic perspective and background of environmental information, define the overall database, present the collective objectives of this regional study, and very briefly present the main aspects of each contribution. Specific conclusions are presented at the end of each paper composing this volume. [Copyright &y& Elsevier]

Facies, stratal and spectral analyses of an outer ramp lime mudstone succession (Aguilo´n, north Iberian Ranges, Spain) are presented in this work. The studied succession is Late Kimmeridgian (eudoxus and beckeri zones) in age and comprises the transgressive and highstand deposits of a third-order depositional sequence. A number of higher-order sequences (bundles and sets of bundles) have been identified based on the comparative analysis of the bedding planes. The bundles and sets of bundles show a well-defined stratal pattern. Spectral analysis has provided further independent confirmation of the cyclical nature of the bundles and sets of bundles defined from field analysis.The bundles have variable thickness (from 1 to 2 m) and are formed by up to 10 micritic beds. They have been related to sea-level changes controlled by the orbital precession cycle, affecting the shallow productivity area. A significant amount of the lime mudstones accumulated in outer ramp settings were derived from resedimentation of the shallow carbonate production areas. Many of the bundles show a lower interval with a thinning and fining-up trend, indicating a progressive decrease of the carbonate production (and carbonate export) during periods of high-frequency sea-level rise.The late transgressive and highstand deposits show sets of bundles (groups of five bundles, from 5 to 8 m) probably related to sea-level changes controlled by the short eccentricity cycle. The overall thickness and the stacking pattern observed in the sets of bundles are controlled by the long-term sea-level variation. The sets of bundles located in the late transgressive deposits show thinner micritic beds in their lower or middle part. The sets of bundles found in the highstand deposits are thinner and show a thickening-up and thinning-up trend. On the studied carbonate ramp, during periods of long-term sea-level rise, the overall carbonate production (and carbonate export) is high, although the superposition of the high-frequency sea-level rises may result in episodic flooding and drowning of the shallow ramp areas. During periods of long-term, early highstand of sea level, the overall carbonate production (and carbonate export) is more reduced, but it has maximum peaks during the transgressive (and early highstand) intervals of the high-frequency sea-level cycles. Sedimentation during the long-term sea-level fall (late highstand) was scarce and discontinuous in the outer ramp area, and resulted in the overall thickness reduction of the sets of bundles. [Copyright &y& Elsevier]

The objective of this paper is to contribute to the development of sequence stratigraphic models for extensive epicontinental carbonate systems deposited over cratonic areas. Epicontinental carbonates of the SW German Upper Jurassic were analysed in terms of microfacies, sedimentology and sequence stratigraphy based on 2.5 km of core, 70 borehole gamma ray logs and 24 quarries. Facies analysis revealed six major facies belts across the deeper parts of the carbonate ramp, situated generally below fair-weather wave base, and mostly below average storm wave base but in the reach of occasional storm events. Observed stratigraphic patterns differ in some aspects from widely published sequence stratigraphic models:

Abstract Successions across the Middle–Upper Jurassic disconformity in the Lusitanian Basin (west-central Portugal) are highly varied, and were probably developed on a large westward-inclined hangingwall of a half-graben. The disconformity is preceded by a complex forced regression showing marked variations down the ramp, and provides an example of the effects of rapid, relative sea-level falls on carbonate ramp systems. In the east, Middle Jurassic inner ramp carbonates (‘Candeeiros’ facies) are capped by a palaeokarstic surface veneered by ferruginous clays or thick calcretes. In the west, mid-outer ramp marls and limestones (‘Brenha’ facies) are terminated by two contrasting successions: (1) a sharp-based carbonate sandbody capped by a minor erosion surface, overlain by interbedded marine–lagoonal–deltaic deposits with further minor erosion/exposure surfaces; (2) a brachiopod-rich limestone with a minor irregular surface, overlain by marls, lignitic marls with marine and reworked non-marine fossils and charophytic limestones, with further minor irregular surfaces and capped by a higher relief ferruginous erosional surface. The age ranges from Late Bathonian in the east to Late Callovian in the west. This disconformity assemblage is succeeded by widespread lacustrine–lagoonal limestones with microbial laminites and evaporites (‘Cabaços’ facies), attributed to the Middle Oxfordian. Over the whole basin, increasingly marine facies were deposited afterwards. In Middle Jurassic inner-ramp zones in the east, the overall regression is marked by a major exposure surface overlain by continental sediments. In Middle Jurassic outer-ramp zones to the west, the regression is represented initially by open-marine successions followed by either a sharp marine erosion surface overlain by a complex sandbody or minor discontinuities and marginal-marine deposits, in both cases capped by the major lowstand... [ABSTRACT FROM AUTHOR]

Numerous small-scale depositional cycles are present in the Miocene sediments of seismic sequence m along the margin of Great Bahama Bank (ODP Leg 166). These cycles consist of decimetre- to metre-scale alternations between light-grey and dark-grey/black wackestones/packstones. The light-grey layers are well cemented and nearly uncompacted. They contain planktonic and benthic foraminifera, and bioclasts. Bioturbation in these layers is moderate. The dark-grey wackestones/packstones are uncemented, strongly compacted and normally strongly bioturbated. The main components are planktonic foraminifera and fine-grained bioclasts. The dark layers are rich in aragonite and organic carbon and contain around 80% carbonate. The light layers show low aragonite and organic carbon contents combined with carbonate values of up to 97.5%. Light δ13C and slightly negative δ18O values were observed in the dark uncemented layers while the cemented intervals show heavy δ13C values and slightly more positive δ18O values. The carbon isotope signal between the dark and the light layers shows variations of up to 1.45‰. Both δ13C and δ18O co-vary with carbonate content. The Formation MicroScanner images reflect the changes in carbonate mineralogy. The Natural Gamma-Ray Tool shows that variations in siliciclastic content of the examined succession displays a different frequency than the cyclic alternations in carbonate mineralogy. The internal stacking pattern of the cycles is closely tied to sea level. The dark layers are deposited during rising sea level, while the light layers reflect sediment production and export during highstand and falling sea level. These cycles thus represent a rather continuous sediment shedding pattern that is clearly related to the ramp morphology and differs from the highstand shedding pattern typical for rimmed flat-topped platforms. Most measured parameters suggest that primary sediment composition played an important role in the cementation process. The primary differences in composition were enhanced during shallow burial diagenesis. The initially high content of metastable carbonate phases in the periplatform sediments triggered rapid cementation of the primary aragonite-rich layers leading to the formation of the light beds. Dissolution of metastable high-Mg calcite and aragonite was followed by in situ precipitation of more stable dolomite and calcite. Diagenesis was enhanced by the coarse grain size of the primary aragonite-rich layers. In contrast the more pelagic, dark calcite-rich layers were only slightly affected by diagenesis and could preserve their aragonite content. The uncemented layers subsequently were subject to strong mechanical compaction, whereas the cemented beds stayed nearly uncompacted. [Copyright &y& Elsevier]

Cross-bedded grainstones on carbonate ramps and shelves are commonly related to the locus of major wave energy absorption such as shorelines, shoals or shelf breaks. In contrast, on the Early Tortonian carbonate platform of Menorca (Balearic Islands), coarse-grained, cross-bedded grainstones are found at a distance from the palaeoshoreline where they were deposited below the wavebase. Excellent exposures along continuous outcrops on the sea cliffs of Menorca reveal the depositional profile and three-dimensional distribution of the different facies belts of the Tortonian ramp depositional system. Basinward from the palaeoshoreline, fan deltas and beach deposits pass into 5-km-wide gently dipping bioturbated dolopackstone (inner and middle ramp), then into 12–20°-dipping dolograinstone/rudstone clinobeds (ramp slope) and, finally, into subhorizontal fine-grained basinal dolowackestone to dolopackstone (outer ramp). In this Miocene example, coarse-grained grainstones exist in five different settings other than beach deposits: (1) on the middle ramp, where cross-bedded grainstones were deposited by currents roughly parallel to the shoreline at 40–70 m estimated water depth and are interbedded with gently dipping bioturbated dolomitized packstones; (2) on the upper slope, where clinobeds are composed mostly of in situ rhodoliths and red-algae fragments; (3) on the lower slope, as small-scale bedforms (small three-dimensional subaqueous dunes) migrating parallel to the slope; (4) at the transition between the lower slope and the outer ramp, where mollusc-rich and rhodolithic rudstones and grainstones, interbedded in dolomitized laminated wackestones containing abundant planktonic foraminifera, infill slide/slump scars as upslope-backstepping bodies (backsets); (5) at the toe of the slope, where coarse skeletal grainstones indicate bedform migration parallel to the platform margin, induced by currents at more than 150 m estimated water depth. This... [ABSTRACT FROM AUTHOR]

Uppermost Jurassic limestones of the South-East Basin (France) are organized into four facies associations that were deposited in four distinct zones: (1) peritidal lagoonal limestones; (2) bioclastic and reefal limestones; (3) pelagic lime mudstones; (4) lime mudstones/calcarenites/coarse breccias. Calcarenite deposits of zone 4 exhibit sedimentary structures that are diagnostic of deposition under wave-induced combined flow. In subzone 4a, both vertical and lateral transitions from lime mudstone/calcarenite to breccia indicate in situ brecciation under wave-cyclic loading. Breccias were produced by heterogeneous liquefaction of material previously deposited on the sea floor. Deposits in subzone 4a record relatively long periods (>400 kyr) of sedimentation below wave base, alternating with periods of deposition under wave-induced currents and periods of in situ deformation. In this zone, storm waves were attenuated by wave–sediment interaction, and wave energy was absorbed by the deformation of soft sediment. With reference to present-day wave attenuation, water depths in this zone ranged between 50 and 80 m. Landwards of the attenuation zone, in zone 3, storm waves were reduced to fair-weather wave heights. Storm wave base was not horizontal and became shallower landwards. As a consequence, water depth and wave energy were not linearly related. On a small area of the seaward edge of subzone 4a, cobbles were removed by traction currents and redeposited in subzone 4b. There, they formed a 100-m-thick wedge, which prograded over 3 km and was built up by the stacking of 5- to 20-m-thick cross-stratified sets of coarse breccia. This wedge records the transport and redeposition of cobbles by a high-velocity unidirectional component of a combined flow. The increase in flow velocity in a restricted area is proposed to result from flow concentration in a channel-like structure of the downwelling in the gulf formed by the basin. In more distal subzone 4c, the hydrodynamic effect of wave-induced currents was quasi-permanent, and brecciation by wave–sediment interaction occurred only episodically. This indicates that, seawards of the attenuation zone, hydrodynamic storm wave base was deeper than mechanical storm wave base. Uppermost Jurassic carbonates were deposited and soft-sediment deformed on a hurricane-dominated ramp of very gentle slope and characterized by a zone of storm wave degeneration, located seawards of a zone of sedimentation below wave base. [ABSTRACT FROM AUTHOR]

The Middle Ordovician Duwibong Formation (about 100 m thick), Korea, comprises various lithotypes deposited across a carbonate ramp. Their stacking patterns constitute several kinds of meter-scale, shallowing-upward carbonate cycles. Lithofacies associations are grouped into four depositional facies: deep- to mid-ramp, shoal-complex, lagoonal, and tidal-flat facies. These facies are composed of distinctive depositional cycles: deep subtidal, shallow subtidal, restricted marine, and peritidal cycles, respectively. The subtidal cycles are capped by subtidal lithofacies and indicate incomplete shallowing to the peritidal zone. The restricted marine and peritidal cycles are capped by tidal flat lithofacies and show evidence of subaerial exposure. These cycles were formed by higher frequency sea-level fluctuations with durations of 120 ky (fifth order), which were superimposed on the longer term sea-level events, and by sediment redistribution by storm-induced currents and waves. The stratigraphic succession of the Duwibong Formation represents a general regressive trend. The vertical facies change records the transition from a deep- to mid-ramp to shoal, to lagoon, into a peritidal zone. The depositional system of the Duwibong Formation was influenced by frequent storms, especially on the deep ramp to mid-ramp seaward of ooid shoals. The storm deposits comprise about 20% of the Duwibong sequence. [ABSTRACT FROM AUTHOR]

In the castern Anti-Atlas (SE Morocco), a small sedimentary basin (Mader Basin) evolved during the late Palacozoic. The Middle Devonian deposits consist of shales and limestones with a thickness up to 700 m in the depocentre. Sedimentary structures and sole marks of Middle Devonian limestones indicate transport from the northwest and the south towards the basin centre, located in the central Mader area. Lithostratigraphic, biostratigraphic, and dynamic stratigraphic approaches were applied to correlate stratigraphic sections. Five correlatable large-scale base-level hemicycles were recognized in the Middle Devonian succession. Thickness trends of Middle Devonian deposits, regional correlations, and facies-trends reveal the geometry of a carbonate ramp. The carbonate ramp was slightly inclined (<1°) to the NE. A sedimentary wedge, consisting of limestones and limestone/marl alternations, was deposited during the Eifelian and marks the transition from the ramp to the adjacent basin. Middle Devonian water depths are estimated as close to and within the storm wave-base at the southern area of the ramp and far below storm wave-base in the northeastern part of the ramp. Shallowest conditions (inner-ramp environment), close or within the fairweather wave-base, existed during the early Givetian as documented by the abundance of recfal fauna (stromatoporoids, corals) and calcimicrobes (lumps, micritic envelopes) in the eastern and southeastern area of the ramp. [ABSTRACT FROM AUTHOR]

A sedimentological investigation of Miocene deposits at the periphery of the Zagros foreland basin, Kurdistan Region, NE Iraq, reveals a cyclical arrangement of carbonate-evaporite ramp facies. The study aims to provide rare insight into the lateral variability of microfacies and environments of such systems' inner ramp and shoreline. Between 10 and 40 depositional cycles are preserved, separated by a flooding surface, and recording an overall basinward progradation. In each cycle, a shallowing-upward trend from a lower-energy calcareous mudstone and mudstone-wackestone carbonate microfacies at the base to a higher-energy packstone-grainstone-rudstone or low-energy algal mat/stromatolitic carbonate microfacies above is evident. Evaporite deposits of supratidal sabkha origin cap each carbonate deposit. Red clastic sediments that advanced south-westward into the basin from the adjacent Zagros hinterland overlie each evaporite deposit. A flooding surface and return to calcareous mudstones mark the start of the next cycle. Outcrop and thin-section analysis of the carbonate deposits of each cycle reveals a shoaling-up to inner-ramp facies with varied environmental settings that developed under a range of hydrodynamic conditions. Microfacies analysis indicates that these environments included normal marine salinity open lagoons, hypersaline lagoons, restricted and shallow lagoons, sand shoals, intertidal and supratidal flats, supratidal ponds, and a coastal alluvial plain that included channelised deposits and palaeosols. The cyclical facies trend changes toward the top of the succession in that the relative rate of siliciclastic supply markedly increased, whereas the rate of carbonate and evaporite production decreased. Progradation and shoreline migration through time caused lateral and vertical facies changes and thickness variations over the succession. Repeated relative sea-level changes, associated changes in climate, and variations in sediment supply from the hinterlands during the collision of the Arabian and Iranian plates, combined with a variable rate of accommodation generation, are inferred to have controlled the preserved cyclicity. • Zagros Basin Fatha Formation carbonate-evaporite-red bed cycles vary laterally. • Carbonates shoal upwards to high energy or to low energy, e.g. stromatolitic, facies. • Inner ramp settings vary in hydrodynamic and salinity conditions. • Red clastics overlie supratidal sabkha evaporites; clastics flux increases upward. • Controls: Varying Middle Miocene sea level, climate, Zagros erosion and accommodation. [ABSTRACT FROM AUTHOR]

The primarily carbonate Gabbs Formation of west-central Nevada, U.S.A., remains an important, rare example of Panthalassan shallow-marine environments from the Late Triassic and through the Triassic–Jurassic boundary. Its relevance as a locality persists, particularly as the end-Triassic mass extinction interval is increasingly recognized as a carbonate crisis, evidenced by the global decline of carbonate facies and calcareous marine organisms. However, important transitions across key stratigraphic boundaries in this region have tended to be evaluated in isolation, producing an incomplete picture of sedimentation through the duration of the Late Triassic leading up to the geochemical crises and mass extinction at the close of the Triassic. In this work, multiple correlative measured sections are used to describe the facies in the mixed carbonate-siliciclastic ramp and characterize controls on carbonate facies. The outer ramp transition to inner ramp facies of the Gabbs represent a transgressive–regressive–transgressive cycle culminating in a transition to terrigenous inputs and a gradual decline of carbonate sediments stratigraphically below the mass extinction interval. This predictable loss of carbonate facies and the near continuous deposition of the Gabbs Formation allow for evidence of facies changes and acidifying conditions in the latest Triassic to be considered independently, in contrast to other global Late Triassic sections where depositional hiatuses or abrupt facies changes often compound these records. Establishing a baseline sedimentation for the Late Triassic demonstrates that the final loss of carbonate facies can be decoupled from the onset of acidifying conditions, resulting in a more precise timeline of latest Triassic environmental upheaval. [ABSTRACT FROM AUTHOR]

The results of a multiproxy study on Mishrif carbonates from the margins of the Central Mesopotamian Basin of Iraq display a wide range of rock fabrics and diagenetic features, all affecting reservoir quality and flow properties in a complex manner. Based on petrographic and facies analyses of the Mishrif Formation in the AD oilfield, the model of a homoclinal ramp geometry with twelve characteristic microfacies types is proposed. A relevant observation is that the ramp, judging from the core data of the AD oilfield studied here, reflects low-energy conditions as documented by an abundancy of fine-grained carbonates in nearly all microfacies types. This notion is perhaps best understood in the context of an intrashelf basin with significant wave-seafloor interaction leading to wave degradation and a shallow effective wave base. In contrast to the rudist bioherms that typify the more basin-marginal settings, we find mainly evidence for small, low-relief buildups characterized by green algae. The Mishrif reservoir properties are shaped by two main diagenetic features: (i) early diagenetic, aquifer-related marine-meteoric mixing zone dissolution inducing abundant fabric selective porosity and (ii) the preferential cementation of Thalassinoides burrows leading to low-porosity concretionary carbonate nodules with reservoir properties that differ significantly from those of the host carbonate. Given the somewhat more distal position of the AD oilfield, the effects of prolonged stages of subaerial exposure related to sea-level fall, as reported from more basin marginal settings, are not recognized. The bending and splaying of seams around nodules and the well-preserved skeletal material within these concretionary carbonates demonstrate that the onset of nodule cementation was early diagenetic/pre-compactional in nature. Based on integrated microfacies and reservoir properties, seven rock types (i.e., Rock Type I-VII) with distinctive reservoir qualities are recognized. Nodular concretions are mainly developed in the Rock Type I lithology and result in distinctive cm-to dm-scale heterogeneity. The contrast between small, poorly-connected pore systems in nodules and medium-sized, well-connected pore systems in the host rock are best described as an inconspicuous, dual permeability system. Data shown here and evidence from other studies dealing with the Mishrif in the Central Mesopotamian Basin are important to understand and predict reservoir properties in other carbonate fields with similar properties. • The Lower Mishrif in Iraq was deposited on a low-energy homoclinal ramp. • A genetic model to explain the relationship between bioturbation and concretion, and their impact on reservoir properties. • Seven reservoir types with distinctive porosity system are recognized based on microfacies and reservoir property. [ABSTRACT FROM AUTHOR]

Core, logging and high-resolution seismic data from ODP Leg 166 were used to analyse deposits of the Neogene (Miocene–Lower Pliocene) Bahamian outer carbonate ramp. Ramp sediments are cyclic alternations of light- and dark-grey wackestones/packstones with interbedded calciturbidite packages and minor slumps. Cyclicity was driven by high-frequency sea-level changes. Light-grey layers containing shallow-water bioclasts were formed when the ramp exported material, whereas the dark-grey layers are dominantly pelagic. Calciturbidites are arranged into mounded lobes with feeder channels. Internal bedding of the lobes shows a north-directed shingling as a result of the asymmetrical growth of these bodies. Calciturbidite packages occur below and above sequence boundaries, indicating that turbidite shedding occurred during third-order sea-level highstands and lowstands. Highstand turbidites contain shallow-water components, such as green algal debris and epiphytic foraminifera, whereas lowstand turbidites are dominated by abraded bioclastic detritus. Gravity flow depocentres shifted from an outer ramp position during the early Miocene to a basin floor setting during the late Miocene to early Pliocene. This change was triggered by an intensification of the strength of bottom currents during the Tortonian, which was also responsible for shaping the convex morphology of the outer ramp. The Miocene and Lower Pliocene of the leeward flank of Great Bahama Bank provides an example of the poorly known depositional setting of the outer part of distally steepened carbonate ramps. The contrast between its sedimentary patterns and the well-known Upper Pliocene–Quaternary slope facies associations of the flat-topped Great Bahama Bank shows the strong control that the morphology of a carbonate platform exerts on the depositional architecture of the adjacent slope and base-of-slope successions. [ABSTRACT FROM AUTHOR]