Isolated Carbonate Platform Research Articles

Pre-salt to salt stratigraphic architecture in a rift basin: insights from a basin-scale study of the Gulf of Suez (Egypt)

We propose a basin-scale (∼300 × 100 km) study of the pre-salt to salt sedimentary fill from the Suez rift based on outcrop and subsurface data. This study is a new synthesis of existing and newly acquired data using an integrated approach with (1) basin-scale synthesis of the structural framework, (2) stratigraphic architecture characterization of the entire Suez rift using sequence stratigraphy concepts, (3) lithologic maps reconstruction and interpretation, (4) isopach/depocenter maps interpolation to quantify sedimentary volumes, and (5) quantification of the sediment supply, mean carbonate and evaporite accumulation rates, and their integration into the rift dynamic. The Gulf of Suez is ca. 300-km-long and up to 80-km-wide rift structure, resulting from the late Oligocene to early Miocene rifting of the African and Arabian plates. The stratigraphic architecture has recorded five main stages of rift evolution, from rift initiation to finally tectonic quiescence characterized by salt deposits. Rift initiation (ca. 1–4 Myr duration): the Suez rift was initiated at the end of the Oligocene along the NNW-SSE trend of the Red Sea with evidences of active volcanism. Continental to lacustrine deposits only occurred in isolated depocenters. Sediment supply was relatively low. Rift widening (ca. 3 Myr duration): the rift propagated from south to north (Aquitanian), with first marine incursions from the Mediterranean Sea. The rift was subdivided into numerous depocenters controlled by active faults. Sedimentation was characterized by small carbonate platforms and associated sabkha deposits to the south and shallow open marine condition to the north with mixed sedimentation organized into an overall transgressive trend. Rift climax (ca. 5 Myr duration): the rift was then flooded during Burdigalian times recording the connection between the Mediterranean Sea and the Red Sea. The faults were gradually connected and reliefs on the rift shoulders were high as evidenced by a strong increase of the uplift/subsidence rates and sediment supply. Three main depocenters were then individualized across the rift and correspond to the Darag, Central, and Southern basins. Sedimentation was characterized by very large Gilbert-type deltas along the eastern margin and associated submarine fans and turbidite systems along the basin axis. Isolated carbonate platforms and reefs mainly occurred in the Southern basin and along tilted block crests. Late syn-rift to rift narrowing (ca. 4 Myr duration): during the Langhian, the basin recorded several falls of relative sea level and bathymetry in the rift axis was progressively reduced. The former reliefs induced during the rift climax were quickly destroyed as evidenced by the drastic drop in sediment supply. Stratigraphic reconstruction indicates that the Central basin was restricted during lowstand period; meanwhile, open marine conditions prevailed to the north and south of the Suez rift. The Central basin, Zaafarana, and Morgan accommodation zones thus acted as a major divide between the Mediterranean Sea and the Red Sea. During Serravalian times, the Suez rift also recorded several disconnections between the Mediterranean and Red seas as evidenced by massive evaporites in major fault-controlled depocenters. The Suez rift was occasionally characterized by N–S paleogeographic gradient with restricted setting to the north and open marine setting to the south (Red Sea). Tectonic quiescence to latest syn-rift (ca. 7 Myr duration): the Tortonian was then characterized by the deposition of very thick salt series (>1000 m) which recorded a period of maximum restriction for the Suez rift. The basin was still subdivided into several sub-basins bounded by major faults. The basin with a N-S paleogeographic gradient was totally and permanently disconnected from the Mediterranean Sea and connected to open marine condition via the Red Sea. The Messinian was also characterized by a thick salt series, but the evaporite typology and sedimentary systems distribution suggest a more humid climate than during Tortonian times. Pre-salt to salt transition was not sharp and lasted for ca. 4 Myr (Langhian-Serravalian). It was initiated as the result of the combined effect of (1) climatic changes with aridization and low water input from the catchments and (2) rift dynamic induced by plate tectonic reorganization that controlled the interplay between sea level and accommodation zones constituting sills.

The Extent and Patterns of Sediment Filling of Accommodation Space On Great Bahama Bank

Abstract Great Bahama Bank (GBB) is the modern example of a flat-topped, isolated carbonate platform. It is a major modern location of carbonate deposition that stands behind much of the understanding of modern processes of carbonate sedimentation, serves as a training venue for academia and industry, is the basis for numerous geological models, and is commonly used as a reservoir analog. GBB also provides valuable insight into the extent and patterns of sediment fill of accommodation space atop an isolated carbonate platform. Satellite imagery (Landsat TM and ETM+) and an extensive set of water-depth measurements (n = 5,723) were used to map bathymetry across GBB and derive a digital terrain model (DTM). Analyzing the extent, patterns, and nature of sediment fill of accommodation space was facilitated by partitioning a depositional facies map on the basis of the DTM to show that 18% of accommodation on the GBB is “overfilled and filled” (emergent to −1.5 m water depth), 52% is “underfilled” (−1.5 to −6.0 m), and 30% is “unfilled” ( −1.5 m water depth) and therefore the greater part of available accommodation (88,000 km2) remains incompletely filled with sediment. Areas of filled accommodation mostly extend platformward from the western coastlines of islands, which in turn are preferentially distributed along the eastern (windward) margin of the GBB. Seventy percent of sediment in the areas of filled accommodation is rudstone, high-energy grainstone, grainstone, and mud-poor packstone. Although dominated by grainstones (45%), since it occupies so much space (55,000 km2), the underfilled sector also contains the most heterogeneous facies mosaic and by definition, therefore, the greatest and most complex lateral facies variations. Although islands are numerous (n = 1,430) they occupy only 8%, or 8,700 km2, of the platform top. Despite their small proportional occupancy of the platform, islands play a direct role in the accumulation of muddy fabrics and exert a sphere of influence over the character of sedimentation for many tens of kilometers from their coastlines. Further, since islands represent the portion of the bank where accommodation has been overfilled, their rarity emphasizes the challenges that such a large platform faces in filling accommodation space, even given the diverse grain factories producing carbonate sediment (mud precipitation through whitings, ooids and reefs along the platform margins, skeletal sediments and nonskeletal grains such as fecal pellets, peloids, and pelletoids). Two factors can be evoked to explain the inability of GBB to fill accommodation space. First, falling sea level during the Pleistocene appears to have repeatedly aborted the filling process. By analogy, it will not be able to do so in the Holocene either, a situation exasperated by the second factor, which is that most of the Holocene GBB, particularly areas away from islands, presently lack any appreciable filling. Instead, facies analysis suggest reduced sedimentation and enhanced cementation. Through regional mapping, the work delivers a platform-wide assessment of how accommodation is filled and the facies responsible for the filling. Amongst other trends, by highlighting how the thickest accumulations of Holocene sediment are skewed to the windward margin of the GBB and related to the presence of islands, whereas the thinner accumulations, which dominate the platform interior and are more grainy but also more heterogeneous than the thicker deposits, these data might contain useful guidelines as to how depositional cycles might vary laterally in ancient systems.

A Pliocene–Quaternary analogue for ancient epeiric carbonate settings: The Malita intrashelf basin (Bonaparte Basin, northwest Australia)

During the Pliocene–Quaternary, the Bonaparte Basin is characterized by a very wide (>600 km [>370 mi]) carbonate platform and 200-km-wide (125-mi-wide) Malita intrashelf basin (ISB). Using three-dimensional and two-dimensional seismic data combined with exploration well data, this study characterizes the stratigraphic evolution of the Malita ISB during the last 3.5 m.y. Two third-order transgressive sequences can be distinguished. A late Pliocene transgression occurred over an irregular topography resulting from the flexural reactivation of the Malita graben. In the center of the ISB, carbonate aggradation resulted in the formation of isolated carbonate platforms separated by deeper water seaways and interplatform areas. Wider and more numerous carbonate platforms developed on the edges of the ISB. During the late Quaternary, renewed flexural deformation initiated a second transgressive cycle marked by higher subsidence rates in the ISB center than along its edges. High rates of accommodation creation (at third order) combined with higher-frequency (fourth-order), high-amplitude fluctuating sea levels and increased clastic input resulted in the progressive demise and burial of the carbonate platforms in the ISB center. Thus, the Pliocene–Quaternary stratigraphic architecture of the Malita ISB is strongly controlled by differential subsidence that controls spatial distribution of accommodation and ultimately platform architectures. The Malita ISB constitutes a rare recent analogue for Paleozoic and Mesozoic hydrocarbon-bearing ISBs.

川东奉节及周缘地区下三叠统飞仙关组沉积特征及相带演化

根据野外剖面观察和室内镜下岩石薄片鉴定分析，结合最新钻井资料，以岩石学、古生物及地球物理解释成果为基础，确定研究区早三叠世飞仙关组早期的孤立碳酸盐台地模式和晚期的连陆碳酸盐台地模式，细分为局限台地、开阔台地、台地边缘浅滩、台地前缘斜坡和陆棚/盆地等沉积相类型。通过关键层序界面识别，将飞仙关组划分为2个三级层序和5个四级层序，建立了四级层序地层格架。层序格架内沉积相演化规律表明，飞仙关期，自早期到晚期水体逐渐变浅，发生充填补齐的沉积作用，奉节地区沉积格局逐渐由开阔台地–台地边缘–前缘斜坡–海槽相过渡为局限台地–开阔台地，至飞仙关晚期完全准平原化为局限台地潮坪沉积。 According to the observation of field profile and the laboratory analysis of thin sections, combined with the latest drilling data and based on the results of petrology, paleontology and geophysical interpretation, it was determined that in the earlier Feixianguan Formation of Lower Triassic there existed the isolated carbonate platform mode and the latter period of the land carbonate platform, and it was subdivided into the sedimentary types of restricted platform, open platform, shoal on the platform margin, platform fore-slope, shelf/basin and so on. According to the identification of key sequence boundaries, the Feixianguan Formation in the study area was divided into 2 third-order sequences and 5 fourth-order sequences, and a fourth-order sequence stratigraphic framework was established. The law of sedimentary facies evolution in sequence framework shows that the water body becomes shallow gradually from the Earlier Period to the Latter Period of Feixianguan Formation, and in this period, the filling in sedimentation appears. The sedimentary framework of Feixianguan Formation in Fengjie Area is transitioned from open platform- platform margin-platform fore-slope-shelf sedimentation zones to the restricted platform-open platform, and in the latter period of Feixianguan Formation it becomes a tidal flat sediment of restricted platform caused by complete quasi-plain.

Seismic sequence stratigraphic analysis of the carbonate platform, north offshore Taiping Island, Dangerous Grounds, South China Sea

Taiping Island, also known as Itu Aba, is the largest natural terrestrial landmass in the South China Sea and is centrally located. Using bathymetry and marine multi-channel seismic data, we explored the seismic stratigraphic features of the offshore and isolated carbonate platform north of Taiping Island. The western flank of the carbonate platform is characterized by an intercalation between high-amplitude and low-amplitude reflections, showing the landward and seaward migration of the platform foreslope deposits. In addition, there are two offshore carbonate build-ups that are underlain by normal faults. Six sequence boundaries and five depositional sequences caused by eustatic sea level cycles are identified and correlated with the eustatic sea level change chart. Although the evolution of the seismic sequences is partly controlled by local tectonics, the overall stacking pattern of the sedimentary strata in our study area reveals five third-order cycles and one second-order cycle, which is in accordance with the eustatic sea level chart. Additionally, the formations of the Western Taiping Seamount Group and the Zhenghe-Daoming Trough are preliminarily analyzed based on seismic data.

Multiscale fracture network characterization and impact on flow: A case study on the Latemar carbonate platform

AbstractA fracture network arrangement is quantified across an isolated carbonate platform from outcrop and aerial imagery to address its impact on fluid flow. The network is described in terms of fracture density, orientation, and length distribution parameters. Of particular interest is the role of fracture cross connections and abutments on the effective permeability. Hence, the flow simulations explicitly account for network topology by adopting Discrete‐Fracture‐and‐Matrix description. The interior of the Latemar carbonate platform (Dolomites, Italy) is taken as outcrop analogue for subsurface reservoirs of isolated carbonate build‐ups that exhibit a fracture‐dominated permeability. New is our dual strategy to describe the fracture network both as deterministic‐ and stochastic‐based inputs for flow simulations. The fracture geometries are captured explicitly and form a multiscale data set by integration of interpretations from outcrops, airborne imagery, and lidar. The deterministic network descriptions form the basis for descriptive rules that are diagnostic of the complex natural fracture arrangement. The fracture networks exhibit a variable degree of multitier hierarchies with smaller‐sized fractures abutting against larger fractures under both right and oblique angles. The influence of network topology on connectivity is quantified using Discrete‐Fracture‐Single phase fluid flow simulations. The simulation results show that the effective permeability for the fracture and matrix ensemble can be 50 to 400 times higher than the matrix permeability of 1.0 · 10−14 m2. The permeability enhancement is strongly controlled by the connectivity of the fracture network. Therefore, the degree of intersecting and abutting fractures should be captured from outcrops with accuracy to be of value as analogue.

Modern sediments and Pleistocene reefs from isolated carbonate platforms (Iles Eparses, SW Indian Ocean): A preliminary study

Isolated carbonate platforms occur throughout the geologic record, from Archean to present. Although the respective roles of tectonics, sediment supply and sea-level changes in the stratigraphical architecture of these systems are relatively well constrained, the details of the nature and controls on the variability of sedimentological patterns between and within individual geomorphologic units on platforms have been barely investigated. This study aims at describing and comparing geomorphological and sedimentological features of surficial sediments and fossil reefs from three isolated carbonate platforms located in the SW Indian Ocean (Glorieuses, Juan de Nova and Europa). These carbonate platforms are relatively small and lack continuous reef margins, which have developed only on windward sides. Field observations, petrographic characterization and grain-size analyses are used to illustrate the spatial patterns of sediment accumulation on these platforms. The internal parts of both Glorieuses and Juan de Nova platforms are blanketed by sand dunes with medium to coarse sands with numerous reef pinnacles. Skeletal components including coral, green algae, and benthic foraminifera fragments prevail in these sediments. Europa platform exhibits a similar skeletal assemblage dominated by coral fragments, with the absence of wave-driven sedimentary bodies. Fossil reefs from the Last interglacial (125,000 years BP) occur on the three platforms. At Glorieuses, a succession of drowned terraces detected on seismic lines is interpreted as reflecting the last deglacial sea-level rise initiated 20,000 years ago. These findings highlight the high potential of these platforms to study past sea-level changes and the related reef response, which remain poorly documented in the SW Indian Ocean.

Evidence for global Famennian and Tournaisian geologic events in the section of an isolated carbonate platform in the eastern Urals

The composition of stable carbon and oxygen isotopes in the section of an isolated carbonate platform is analyzed. Traces of several global and subglobal transgressions and regressions have been found in the limestone strata. Some of these phenomena were associated with the Upper Kellwasser (at the Frasnian–Famennian boundary) and multiphase Hangenberg (at the Devonian–Carboniferous boundary) Events. Nevertheless, there were no considerable sea level fluctuations in the platform water area. There is no evidence for subaerial erosion. The bottom water during sedimentation was mostly in oxic conditions.

Changes in marine nitrogen fixation and denitrification rates during the end-Devonian mass extinction

The end-Devonian was a critical interval in Earth history recording the transition from the Early Paleozoic greenhouse climate to the Late Paleozoic icehouse climate. A mass extinction at this time (the Hangenberg extinction) eliminated ~21% of genera and ~16% of families of marine invertebrates, although its causes remain poorly understood. The marine nitrogen cycle is intimately related to the nutrient status of seawater, microbial community composition, and the redox condition of the oceans, and, thus, it may provide insights into the mechanism(s) of the end-Devonian mass extinction and climate change. Here, we analyzed high-stratigraphic-resolution bulk-sediment nitrogen isotope variation (δ15Nbulk) in three sections from South China: (1) Long'an, an isolated carbonate platform section, (2) Qilinzhai, a shallow-water carbonate platform section between the Yangtze Oldland and the Youjiang Trough, and (3) Malanbian, a shallow-water carbonate platform section between the Yangtze and Cathaysia oldlands and distant from deep-water areas. Our δ15Nbulk records show a major perturbation to the marine nitrogen cycle in the Middle Siphonodella praesulcata Zone, which is marked by a decline in δ15Nbullk from +4‰ to 0‰ at Long'an and from +4.5‰ to +2.5‰ at Malanbian. This perturbation coincided with the main end-Devonian mass extinction as well as with a negative shift in carbonate carbon isotopes (δ13Ccarb). The shift to lower δ15N values suggests locally enhanced nitrogen fixation, possibly as a consequence of increased denitrification in response to globally expanded marine anoxia. Thus, these δ15Nbulk data are consistent with the hypothesis that intense anoxia was the immediate cause of the end-Devonian mass extinction. The δ15Nbulk records generated in this study suggest that there was significant spatial and temporal variation in the nitrogen isotope composition of seawater nitrate in the Yangtze marginal sea during the latest Devonian. This variation may have been related to the complex paleogeography of the South China Craton, which contained numerous isolated and continent-attached platforms and deep-water basins that influenced watermass circulation, nutrient inventories and primary productivity levels, and watermass ventilation and redox conditions.

Middle Permian Sedimentary Cycles and Facies Features in the Tieqiao Section in Laibin, Guangxi, South China

In the Late Paleozoic paleogeography, the Laibin area, South China, locates in the south-eastern margin of the Laibin-Heshan isolated carbonate platform. One global stratotype section for The Guadalupian-Lopingian (G/L) (The end of the Mid-Permian) transition is located in the Tieqiao section in Laibin area, which is regarded as appropriate one for the study. Based on the analysis, seven facies (open platform, restricted platform, neritic shelf, bioclastic shoal, reef, slope, and basin) are recognized in the Maokouan Formations, besides, three sequences have been identified in the Maokouan succession. They all represent a deeping-upward then shallowing-upward sedimentary cycle, and the microfacies alterna- tion conformable marine sequences at that time, which implies consistence of sequence number recorded in the Tieqiao section were little influenced by the role of sys-depositional fault, maybe controled by the paleoceanographic condition.

Peritidal carbonate cycles induced by carbonate productivity variations: A conceptual model for an isolated Early Triassic greenhouse platform in South China

Eustasy has commonly been invoked to explain peritidal carbonate cyclicity, but is difficult to explain cycles formed in a greenhouse climate when eustasy is minimal. We propose that peritidal cycles on an Early Triassic isolated carbonate platform in Guizhou, South China, were formed by hierarchical carbonate productivity variations. Most of the 149 shallowing-upward cycles are typically terminated by flooding over intertidal facies and contain rare supratidal facies and no prolonged subaerial exposure. Low-diversity benthos in the platform interior during the post-end-Permian biotic recovery were sensitive to environmental perturbations, which caused variations in benthic sediment productivity in the subtidal carbonate factory. The perturbations may be driven by changes in salinity and degree of eutrophication, or repeated platform mini-drowning by anoxic and/or CO2-charged deep water upwelled onto the banktop. They were modulated by Milankovitch orbitally-driven climatic and oceanographic factors as suggested by the hierarchical stacking pattern and spectral signals of these cycles. A one-dimensional conceptual model shows that hierarchical productivity variations alone may generate hierarchical peritidal carbonate cycles under conditions of constant subsidence and no sea-level fluctuation.

Carbonate platform-margin architecture and its influence on Cambrian-Ordovician reef-shoal development, Tarim Basin, NW China

Six types of carbonate platform marginal slope have been identified in the Cambrian-Ordovician of Tarim Basin. These include a progradational carbonate ramp platform, a progradational carbonate rimmed platform, an aggradational rimmed carbonate platform, a retrogradational rimmed carbonate platform, an aggradational margin on an isolated carbonate platform and a retrogradational margin on a submerged carbonate platform. Various platform margin architectures and reef-shoal characteristics occur in different areas of the Tarim basin. A progradational carbonate ramp platform margin began in the Early Cambrian in the Tarim basin. A progradational rimmed platform margin developed in the Middle Cambrian time in the northern Tarim basin, whereas contemporaneously a progradational ramp platform margin developed in the southwestern and central Tarim basin. A retrogradational rimmed carbonate platform developed in the northern Tarim basin, whereas an aggradational rimmed carbonate platform occupied the central Tarim basin in the Early Ordovician time. An aggradational margin on an isolated platform and a retrogradational margin on a submerged platform developed mainly during the Late Ordovician in the central Tarim basin. Platform margin-slopes migrated continually throughout the Cambro-Ordovician. The broad platform area (western Tarim Platform) that occupied most of the northwestern and central Tarim Basin in the Early Cambrian time was split by an east-west oriented shelf seaway that began to develop along the eastern and western margins of the platform in the Early Ordovician time and completely transected the platform by Late Ordovician time. The resultant central Tarim Basin platform area was much reduced, elongate east-west around the Central Tarim paleo-uplift, and terminated eastward towards region of the Late Ordovician basinal deposition across the eastern Tarim Basin. Affected by platform margin structure, Climate and paleodepth, algal reefs and shoals developed mainly in the Cambrian, and intraclastic shoals developed mainly in the Early Ordovician, followed by reef-building of framestone or bafflestone in the Late Ordovician.

The stratigraphic, sedimentological and structural evolution of the southern margin of the Kazakhstan continent in the Tien Shan Range during the Devonian to Permian

Abstract The passive margin carbonate platform in the Middle Tien Shan rests on Givetian–Frasnian red siliciclastic strata. It evolved from an attached carbonate platform in the Famennian and early Tournaisian to an isolated carbonate platform in the late Tournaisian to early Bashkirian. The open-ocean side of the platform was reef-rimmed, whereas the continental side was both reef- and shoal-rimmed. Platform interiors exhibit low-energy facies during the Famennian to early Visean and high-energy facies during the late Visean to Bashkirian. Eustatic sea-level rises in the middle Tournaisian, early Visean and near the Visean and Serpukhovian boundary caused major reorganizations in platform architecture. Deformation in the middle Bashkirian reflects the onset of a convergent margin. Flexural loading by an orogenic thrust wedge controlled basin subsidence along the southern edge of the Middle Tien Shan in the Late Pennsylvanian to Asselian. Cessation of deposition in the Asselian followed by folding and granitoid plutonism reflects the onset of a rigid collision. Devonian to Permian carbonates represent outcrop analogues of coeval oil- and gas-rich carbonate platforms in the North Caspian basin and can be used for comparative and predictive sedimentological studies. Palaeozoic carbonate reservoir facies may host subsurface Cenozoic oil fields in the Fergana Basin.

Depositional setting and basin development of the Paleocene—Lower Eocene Sinjar and Khurmala formations, Northern Iraq

Petrographic study of the Sinjar and Khurmala Formations at the Zagros and Taurus Folded Zones, in northern Iraq led to the recognition of 11 carbonate microfacies that can be grouped into seven facies associations. These facies associations deposited within outer shelf, fore-reef, reef, back-reef, lagoon, shoals/bars and channels, and tempestite subenvironments of a composite isolated carbonate platform. The digenetic imprints on the recognized microfacies are prominent and dominated by micritization, dissolution, cementation, neomorphism, dolomitization, compaction, stylolitization, and precipitation of some authigenic minerals such as pyrite, glauconite, and gypsum. Isopach and depositional facies maps of the Sinjar–Khurmala successions show three depocenters in two subbasins in the study area, two of them are elongated and coincide with the Zagroside and the Taurides trends, whereas the third accords with the trend of the Sinjar graben. The reconstruction of the history of the Sinjar and Khurmala carbonates revealed four stages of basin development within two subbasins. The first stage represents the initial deposition of the Sinjar and Khurmala Formations that was preceded by the deposition of the deep marine part of the underlying Kolosh Formation. This depositional phase is characterized by submarine fans and basinal sediments. Both subbasins were partially separated by a ridge or a series of paleohighs, which had been inherited from relieves of the Cretaceous paleosurface. During the second depositional stage, the Sinjar basin is developed by growth of another reef build-up to the southeast with a general direction from southwest near Kirkuk area to the northeast near Sulamani area. During the third depositional stage, the basin was developed through the growth of isolated carbonate platform extending from the Kirkuk to the Duhok. Such platform was drowned during the transgression that covered the northern part of the Kolosh basin and southwestern part of the Aaliji basin. The final depositional stage was represented by a still stand period, when the sea level was stilled, and led to the upgrading growth during the early Highstand system tract of the carbonate shelf . As a result, during this stage, the reef facies were prograded seaward and replaced by the back-reef facies to indicate the end of Highstand during the late regression stage.

OLIGO-MIOCENE VARIABILITY IN CARBONATE PRODUCERS AND PLATFORMS OF THE CORAL TRIANGLE BIODIVERSITY HOTSPOT: HABITAT MOSAICS AND MARINE BIODIVERSITY

ABSTRACT A holistic approach is adopted here to evaluate basin-wide trends in carbonate systems, their subenvironments and the potential marine biodiversity partitioning between different habitats within the Coral Triangle biodiversity hotspot in central Southeast Asia. The Central Indonesian Kutai Basin is typical of many Cenozoic Southeast Asian basins in having extensive and varied carbonate systems, and is one of the few regions in the Coral Triangle with detailed systematic multitaxon evaluation of Oligo-Miocene deposits. The Kutai Basin may therefore provide data, when compared with other modern and global datasets, to better understand marine biodiversity development within the global diversity foci. Carbonate systems in the Kutai Basin included small-scale ephemeral features, such as delta-associated patch reefs, mixed carbonate-clastic shelves, and large-scale (> 10 km) land-attached and isolated carbonate platforms affected by varied energy regimes. Twenty-five–plus subenvironments or habitats a...

There was no “Great Bank of Guizhou” in the Early Triassic in Guizhou Province South China

In the 1990s, some geologists named the Early Triassic isolated carbonate platform in the Luodian area of southern Guizhou Province in South China as the “Great Bank of Guizhou”. During the past twenty years, this term “Great Bank of Guizhou” was used in more than 300 articles in foreign countries. In the 1990s, the authors have studied the lithofacies palaeogeography of the Early and Middle Triassic in South China. In June 2014, we went to the Luodian area and studied the Early Triassic Bianyang section again. According to the geological data we acquired, in the Early Triassic of the Luodian area of southern Guizhou Province, there was only an isolated “Luodian Carbonate Platform”, while no bank existed, not to mention the “Great Bank of Guizhou”. It is worth further discussion.

ORGANISM-ENVIRONMENT INTERACTIONS DURING THE PERMIAN-TRIASSIC MASS EXTINCTION AND ITS AFTERMATH

ORGANISM-ENVIRONMENT INTERACTIONS DURING THE PERMIAN-TRIASSIC MASS EXTINCTION AND ITS AFTERMATH

Simulating flow through forward sediment model stratigraphies: insights into climatic control of reservoir quality in isolated carbonate platforms

Whilst sophisticated multiphase fluid flow models are routinely employed to understand behaviour of oil and gas reservoirs, high-resolution data describing the three-dimensional (3D) distribution of rock characteristics is rarely available to populate models. We present a new approach to developing a quantitative understanding of the effect of individual controls on the distribution of petrophysical properties and their impact on fluid flow. This involves simulating flow through high-detail permeability architectures generated by forward modelling of the coupled depositional–diagenetic evolution of isolated platforms using CARB3D + . This workflow is exemplified by an investigation of interactions between subsidence and climate, and their expression in spatial variations in reservoir quality in an isolated carbonate platform of similar size and subsidence history to the Triassic Latemar Platform. Dissolutional lowering during subaerial exposure controls platform-top graininess via platform top hydrodynamics during the subsequent transgression. Dissolved carbonate is reprecipitated as cements by percolating meteoric waters. However, associated subsurface meteoric dissolution generates significant secondary porosity under a more humid climate. Slower subsidence enhances diagenetic overprinting during repeated exposure events. Single-phase streamline simulations show how early diagenesis develops more permeable fairways within the finer-grained condensed units that can act as thief zones for flow from the grainier but less diagenetically altered cyclic units.

Architecture, development and geological control of the Xisha carbonate platforms, northwestern South China Sea

Newly acquired seismic data allow improved understanding of the architecture and evolution of isolated carbonate platforms on the continental slope of the northern South China Sea. The Xisha carbonate platforms were initiated on a basement high, the Xisha Uplift, in the early Miocene and have remained active up to the present. Their distribution is limited to pre-existing localized, fault-bounded blocks within the Xisha Uplift so individual platforms were small in size at the beginning of the Miocene. However, during the middle Miocene, the platform carbonate factories flourished across an extensive area with 55,900 km(2). The platforms began to backstep in response to a relative sea-level rise in the late Miocene. Platform-edge reefs, patch reefs, pinnacle reefs, atoll reefs and horseshoe reefs, all developed on various platforms. The distribution of platform carbonates shrank significantly during Pliocene-Quaternary time to isolated carbonate platforms, represented today by Xuande Atoll and Yongle Atoll. Tectonics and eustasy were the two main controls on platform development. Tectonics controlled both the initial topography for reef growth and the distribution of platforms, including those that survived the drowning event associated with the late Miocene rapid relative sea-level rise. Eustasy controlled high-frequency carbonate sequence development Crown Copyright (C) 2014 Published by Elsevier B.V. All rights reserved.

Paleotempestite Distribution across an Isolated Carbonate Platform, San Salvador Island, Bahamas

ABSTRACT Mattheus, C.R. and Fowler, J.K., 2015. Paleotempestite distribution across an isolated carbonate platform, San Salvador Island, Bahamas. Sediment cores were collected from coastal ponds across San Salvador Island, an isolated Bahamian carbonate platform, and integrated with aerial photographs and field-survey data to provide insight into how spatially variable storm records are at the island scale and what drives this variance. A better understanding of local tempestite generation and preservation potential is crucial for correlating events across more regional scales. Sandy storm layers, products of beach overwash and/or high-energy aeolian transport from the shore into coastal ponds, are easily distinguished from flocculated carbonate muds, microbial mats, and other organics that ordinarily sequester in the stagnant, low-energy coastal water bodies. Interpreted paleotempestites do not correlate well between studied ponds using a strictly stratigraphic approach, although all sites investigated a...