From platform to basin: the evolution of a Paleocene carbonate margin (Eastern Desert, Egypt)

In this study, progradation and the subsequent retrogradation of a late Paleocene isolated carbonate platform (Galala Mountains, Eastern Desert, Egypt) is demonstrated by variations of distinct facies associations from the platform margin in the north to the hemipelagic basin in the south. A combination of a sea-level drop and tectonic uplift at around 59 Ma (calcareous nannofossil biozone NP5) favored the initiation of the carbonate platform. From this time onwards, the facies distribution along the platform–basin transect can be subdivided into five facies belts comprising nine different facies associations. Their internal relationships and specific depositional settings are strongly coupled with the Maastrichtian–Paleocene seafloor topography, which resulted from local tectonic movements. Patch reefs and reef debris were deposited at the platform margin and the horizontally bedded limestones on the upper slope. Slumps and debris flows were stored on the lower slope. In the subhorizontal toe-of-slope facies belt, mass-flow deposits pass into calciturbidites. Further southwards in the basin, only hemipelagic marls were deposited. Between 59 and 56.2 Ma (NP5–NP8), the overall carbonate platform system prograded in several pulses. Distinct changes in facies associations from 56.2 to 55.5 Ma (NP9) resulted from rotational block movements. They led to increased subsidence at the platform margin and a coeval uplift in the toe-of-slope areas. This resulted in the retrogradation of the carbonate platform. Furthermore the patch-reef and reef-debris facies associations were substituted by the larger foraminifera shoal association. The retrogradation is also documented by a significant decrease in slump and debris-flow deposits on the slope and calciturbidites at the toe of slope.     

Stratal architecture and platform evolution of an early Frasnian syn‐tectonic carbonate platform,Canning Basin,Australia

Facies architecture and platform evolution of an early Frasnian reef complex in the northern Canning Basin of north‐western Australia were strongly controlled by syn‐depositional faulting during a phase of basin extension. The margin‐attached Hull platform developed on a fault block of Precambrian basement with accommodation largely generated by movement along the Mount Elma Fault Zone. Recognition of major subaerial exposure and flooding surfaces in the Hull platform (from outcrop and drillcore) has enabled comparison of facies associations within a temporal framework and led to identification of three stages of platform evolution. Stage 1 records initial ramp development on the hangingwall dip slope with predominantly deep subtidal conditions that prevented any cyclic facies arrangements. This stage is characterised by basal siliciclastic deposits and a major deepening‐upward facies pattern that is capped by a sequence boundary towards the footwall (north‐west) and a major flooding surface towards the hangingwall. Stage 2 reflects the bulk of platform aggradation, significant platform growth towards the hangingwall and the development of reef margins and cyclic facies arrangements. Thickening of this stage towards the hangingwall indicates that accommodation was generated by rotation of the fault block and overlying platform. Stage 3 records a major flooding and backstep of the platform margin. The Hull platform illustrates important elements of margin‐attached carbonate platforms in a half‐graben setting, including: (i) prominent, but limited, coarse siliciclastic input that does not have a major detrimental effect on carbonate production near the rift margin in arid to semi‐arid settings; (ii) wedge‐shaped accommodation created by syn‐depositional rotation of fault blocks and tilting of the hangingwall dip slope, resulting in shallow‐water facies and subaerial exposure up‐dip of the rotational axis and deeper water facies down‐dip; and (iii) evolution of a ramp to rimmed shelf, coincident with a sequence boundary–flooding surface, that is accelerated by tilting of the hangingwall dip slope during fault‐block rotation.     

巢县二叠系栖霞组臭灰岩段异地成因碳酸盐岩

下扬子地区二叠系栖霞组臭灰岩段广泛发育。以巢县为例 ,研究表明组成臭灰岩段的石灰砾岩并非正常沉积。剖面特征 ,岩石学、沉积学和地球化学特征的分析结果 ,显示了石灰砾岩的砾石来源于浅海碳酸盐台地 ,它们作为碳酸盐岩碎屑流的产物 ,沿着台地边缘的斜坡 ,被搬运到半深海—斜坡处再沉积。环绕于砾石周围的胶结物和砾岩层之间的薄层硅质粒泥灰岩 ,主要是由等深流沉积物组成。因此 ,臭灰岩段碳酸盐岩主要是异地成因 ,沉积环境属于碳酸盐台地周缘水体较深的斜坡。     

塔中地区晚奥陶世镶边台地沉积演化

通过大量岩芯、薄片、测井、地震等资料的对比分析,建立了塔中地区上奥陶统良里塔格组层序地层格架,并研究了沉积相演化、分布规律。晚奥陶世塔中地区为开阔台地、台地边缘组成的沉积型镶边台地。良里塔格组层序可划分出海侵体系域、高位体系域,共10个准层序组。前者包括准层序组1～4,为退积、加积准层序组,岩性以泥晶灰岩类为主、夹颗粒灰岩,局部发育生物灰岩。后者包括准层序组5～10,为加积、进积准层序组,岩性为颗粒灰岩、生物礁灰岩夹泥晶灰岩。海侵体系域时期,沉积范围逐步覆盖研究区,开阔台地与台地边缘的沉积范围相对稳定,开阔台地以滩间海、台内洼地等低能沉积亚相为主,台地边缘丘、滩沉积范围逐步扩大,出现镶边沉积特征。高位体系域时期,台地边缘沉积范围基本具有继承性,发育2～7期礁（丘）-滩的沉积旋回,形成礁滩复合体镶边特征;开阔台地大范围内为较低能滩间海沉积,局部发育2～4期丘（礁）-滩沉积旋回。该时期,台地边缘与开阔台地沉积地貌出现明显的高低分异,镶边台地成熟、定型。     

Carbonate platform evolution: from a bioconstructed platform margin to a sand-shoal system (Devonian, Guilin, South China)

ABSTRACT The depositional organization and architecture of the middle–late Devonian Yangdi rimmed carbonate platform margin in the Guilin area of South China were related to oblique, extensional faulting in a strike‐slip setting. The platform margin shows two main stages of construction in the late Givetian to Frasnian, with a bioconstructed margin evolving into a sand‐shoal system. In the late Givetian, the platform margin was rimmed with microbial buildups composed mainly of cyanobacterial colonies (mostly Renalcis and Epiphyton). These grew upwards and produced an aggradational (locally slightly retrogradational) architecture with steep foreslope clinoforms. Three depositional sequences (S3–S5) are recognized in the upper Givetian strata, which are dominated by extensive microbialites. Metre‐scale depositional cyclicity occurs in most facies associations, except in the platform‐margin buildups and upper foreslope facies. In the latest Givetian (at the top of sequence S5), relative platform uplift (± subaerial exposure) and associated rapid basin subsidence (probably a block‐tilting effect) caused large‐scale platform collapse and slope erosion to give local scalloped embayments along the platform margin and the synchronous demise of microbial buildups. Subsequently, sand shoals and banks composed of ooids and peloids and, a little later, stromatoporoid buildups on the palaeohighs, developed along the platform margin, from which abundant loose sediment was transported downslope to form gravity‐flow deposits. Another strong tectonic episode caused further platform collapse in the early Frasnian (at the top of sequence S6), leading to large‐scale breccia release and the death of the stromatoporoid buildups. Siliceous facies (banded cherts and siliceous shales) were then deposited extensively in the basin centre as a result of the influx of hydrothermal fluids. The platform‐margin sand‐shoal/bank system, possibly with gullies on the slope, persisted into the latest Frasnian until the restoration of microbial buildups. Four sequences (S6–S9), characterized by abundant sand‐shoal deposits on the margin and gravity‐flow and hemipelagic deposits on the slope, are distinguished in the Frasnian strata. Smaller‐scale depositional cyclicity is evident in all facies associations across the platform–slope–basin transect. The distinctive depositional architecture and evolution of this Yangdi Platform are interpreted as having been controlled mainly by regional tectonics with contributions from eustasy, environmental factors, oceanographic setting, biotic and sedimentary fabrics.     

四川盆地东北部长兴期沉积特征与沉积格局

四川盆地东北部长兴组（大隆组）为海洋环境的产物,根据沉积特点,可以分为碳酸盐台地沉积体系和盆地沉积体系。碳酸盐台地沉积体系又可进一步分为局限台地、开阔台地、台地边缘礁滩及缓坡等沉积相。在详细研究分析各沉积体系的沉积特点的基础上,探讨了该期沉积相带的空间分布,提出了不存在“开江一梁平”海槽的认识。笔者等认为在“开江梁平海槽”区域内,长兴组只是水体相对台地较深环境（台棚环境）的产物,为碳酸盐缓坡,不宜称为海槽。指出台地边缘浅滩及生物礁是储层最有利相带,礁白云岩及颗粒白云岩等是储层的有利微相。研究区的生物礁为碳酸盐台地边缘缓坡点礁群,沿着台地边缘断续分布。     

Mixed carbonates and siliciclastics in the Quaternary of southern Belize: Pleistocene turning points in reef development controlled by sea‐level change

The Belize barrier and atoll reefs represent one of the largest reef structures in the Atlantic Ocean. The southern shelf of Belize is a classic location of a modern mixed carbonate–siliciclastic system. Whereas knowledge of the Holocene deposits in the area is extensive, data on the Pleistocene system are fragmentary. Open questions include: (i) the nature of the reef foundations (carbonate versus siliciclastics); (ii) the ages of the deposits including the initiation of the barrier reef; and (iii) the response of the mixed system to sea‐level fluctuations. The results of a study of borings on the southern Belize shelf are presented here. Six, up to 105 m long borings were made to better understand the history of this important mixed system. Uranium‐series dating in the Pleistocene was not possible because of diagenetic alteration; however, lithostratigraphy, strontium isotopes and calcareous nannofossil biostratigraphy were used to constrain stratigraphic ages. Results support the contention that the Quaternary development in Belize was quite similar to that of other major barrier reefs such as the Florida Reef Tract and, further afield, the Great Barrier and the New Caledonian Barrier Reefs. All of these barrier reefs are mixed carbonate–siliciclastic systems and significant reef growth only began after the onset of high‐amplitude, eccentricity‐controlled sea‐level changes and as late as during the exceptionally long and warm marine isotope stage 11, some 400 ka. In Belize, Early Pleistocene sections at bases of borings include mollusc‐rich wackestones, rare coral packstones and marls, which were deposited under low to moderate energy conditions in a ramp setting before ca 900 ka, during the high sea‐levels of marine isotope stage 25 and possibly earlier (marine isotope stage 31 or 37). The Belize shelf was subaerially exposed for most of the mid‐Pleistocene and was dominated by siliciclastic sedimentation, possibly during marine isotope stages 24 to 12 when highstands were comparatively low. Continuous reefs at the shelf margin were developing during highstands. In the Late Pleistocene, beginning with the long and high highstand of marine isotope stage 11 (some 400 ka), the southern shelf was flooded entirely and carbonates started to dominate once more. Reefs developed on top of siliciclastic deposits on the shelf. A continuous barrier reef came into existence and largely developed on top of carbonates at the shelf margin. During Late Pleistocene lowstands, siliciclastics presumably no longer reached the shelf margin because of the topographic high of the barrier reef platform. The Quaternary Belize example may serve as a model for reconstructing ancient mixed systems in icehouse worlds, however, any extrapolations are limited by the fact that fast‐growing Scleractinian reef‐builders had not yet evolved in the Palaeozoic.     

城口-鄂西海槽西侧晚二叠世碳酸盐台地边缘发育新认识

基于城口-鄂西海槽西侧地区详细的露头调查、钻井资料分析,结合古生物、古生态以及地层对比,对研究区晚二叠世长兴期碳酸盐台地边缘沉积相及其演化进行详细解剖,得出区内台地边缘骨架礁-凝块石灰泥丘生态-沉积演化对碳酸盐台地边缘构筑具有积极作用的认识。研究表明区内长兴期碳酸盐台地边缘礁滩经历了三个演化阶段:第一阶段,碳酸盐台地边缘坡折带尚未形成,台地边缘礁滩欠发育,且台地前缘斜坡坡度较缓;第二阶段,碳酸盐台地镶边开始形成,发育骨架礁及滩相沉积,垂向上构成进积-加积组合序列,台地前缘斜坡变陡;第三阶段,微生物逐渐占据后生造礁生物生态空间,发育台地边缘凝块石灰泥丘,与上覆台地边缘滩构成垂向加积组合序列,促进了台地边缘正向地貌的发育,使区内台地边缘更加陡峭,台地前缘斜坡发育滑塌角砾岩。造礁生物生态演替及相对海平面变化共同影响并控制长兴期碳酸盐台地边缘构筑过程。     

白云-荔湾深水区新生界生物礁识别与发育模式及主控因素探讨

白云-荔湾地区新生界是否发育大型生物礁一直是珠江口盆地(东部)碳酸盐岩油气勘探的核心问题之一。根据已有的地质资料,总结了该区新生界碳酸盐岩及生物礁发育层段的规律性,并在此基础上首次总结了研究区生物礁地震识别特征、发育模式及其主控因素。研究表明:①白云-荔湾地区发育的大型生物礁在不同层段零星分布,多呈丘形、透镜体状外形,顶部具有强-中反射特征,底部连续可追踪,侧向上多见超覆不整合接触,内部多见加积、进积或退积地震发射特征、偶见杂乱至空白反射;②基于构造活动及古隆起背景,本区建立了3种类型的生物礁发育模式:Ⅰ台地边缘礁发育模式、Ⅱ古隆起斜坡礁发育模式、Ⅲ古隆起顶部礁发育模式;③构造运动及全球海平面变化是该区碳酸盐岩及生物礁发育的主控因素。     

An Early Paleozoic Inter‐Platform Shelf in the Southwest of Tarim Basin,NW China and its Significance for Petroleum Exploration

An early Paleozoic inter‐platform, platform, slope and shelf succession comprised of five Cambrian to mid‐Ordovician seismic sequences, has been identified in the southwestern part of the Tarim Basin. A previously unknown, elongate shelf succession that extends from east to west transects the Taxinan area of the southwestern Tarim Basin. It was flanked by carbonate platforms and platform margins, and by peri‐platform margin slopes on its north and south sides. The Markit platform margin and slope, located along the northern side of the shelf, extended nearly linearly west to east with some headlands and embayments towards the east. The Tangnan platform margin and slope, located along the southern side of the shelf, extended southwest to northeast and was more sinuous with pronounced northwest‐directed headlands flanked by embayments. Differentiation of these settings began in earliest Cambrian time during continental breakup. Initially, broad gentle slopes flanked an open shelf seaway in Cambrian time. In Early Ordovician time, the Markit and Tangnan platform margins became more distinct and rimmed, and were flanked by slightly steeper, but still very gentle slopes. During their deposition, these platform margins and their adjoining slopes exhibited some lateral migration, with a slight overall widening of the open shelf seaway between them from Cambrian to Ordovician time. The presence of these platform margin and slope successions in the southwestern area of the Tarim basin provides another focus for petroleum exploration and discovery of additional carbonate reef‐shoal reservoirs in the Markit and Tangnan areas. The adjoining deep‐water shelf shale and mudstone shelf succession itself is an additional prospective petroleum source rock in close proximity to these potential reef‐shoal reservoirs.     

Sedimentology of middle ordovician carbonates in the Argentine precordillera: evidence of regional relative sea-level changes

The Las Aguaditas Formation in the Argentine Precordillera of San Juan is the only Ordovician carbonate sequence deposited on a slope. Spiculites, mudstones and calcisiltites represent the autochthonous sediments, characterized by a fine lamination, rare fossils and their dark colour. The pelagic fauna consists of rare radiolarians/calcispheres, trinucleid trilobites, graptolites and conodonts. The latter are typical of an open marine environment and proved a Llanvirn—Llandeilo age for the Las Aguaditas Formation.In the upper part of the succession there are several intercalations of megabreccias. Their thickness decreases from about 20 to 4 m towards the top of the formation, accompanied by an increasing amount of carbonate turbidites. The clasts of the breccias are derived from the slope as well as the platform. Each of the megabreccia horizons represents a system of channels, lobes and interchannel deposits, which together form a slope apron. On top of the lower breccia a small biostrome developed, where bryozoans and crinoids are preserved in an autochthonous position.Sedimentation of the Las Aguaditas Formation started with the drowning of the underlying carbonate platform (San Juan limestones). Near the Arenig-Llanvirn boundary, a rapid ecstatic sea-level rise led to the deposition of graptolitic black shales and mudstones. Upwards, allochthonous carbonates become increasingly abundant. The onset of megabreccia deposition coincides with a major relative sea-level fall, caused by block movements in connection with rifting. The subsequent transition from breccia formation towards turbiditic sedimentation corresponds to an environmental shift from the slope towards the toe of slope and basin and marks a renewed moderate sea-level rise. Correspondence to: M. Keller     

碳酸盐台地边缘或斜坡的类型及沉积模式

横切碳酸盐台地可以出现不同的沉积环境和相,其中台地边缘、斜坡或盆地边缘的沉积环境复杂,相的类型多,变化大,而且它们是重要的油气储集岩层和层控矿床的重要控矿相位。另外,盆地边缘或斜坡的沉积相序类型及演化,是沉积盆地分析的重要方面。碳酸盐台地边缘、斜坡或盆地边缘早已引起沉积学者及构造学者的注视,并有不少的论述(Wilson,1975;Mountjoy和James,1982;Read,1982,1985;Cook,1984;曾允孚等,1984)。现将碳酸盐台地边缘或斜坡的类型及沉积模式作一简要论述。     

Compositional variations during phases of progradation and retrogradation of a Triassic carbonate platform (Picco di Vallandro/Dürrenstein, dolomites, Italy)

In this paper data are presented on the composition of sediments deposited at the toe of slope during progradation or retreat of Triassic carbonate platforms in the Dolomites (Italy). For this purpose a succession was studied from the toe of slope of a Triassic (Carnian) carbonate platform (Picco di Vallendro/Dürrenstein, Dolomites, Italy). The microfacies analysis of selected calciturbidites sequences revealed a reduced input of oncolites and ooids during progradation and an increase in clasts. The main input, however, was derived from the reefs on the platform. Retrogradation of the platform showed an increase of filaments and radiolarians (open ocean biota) as well as carbonate mud and a reduced input of grains that originated within the reefs on the platform. Both during progradation and retrogradation parts of the platform were flooded and could produce excess sediment that could be exported to the surrounding basins. However, the absence of platform interior biota documents that progradation occurred from sediments of the reefal belt, probably during relative sea-level lowstands. Carbonate composition varies systematically with toe-of-slope progradation/retrogradation and, thus, argues for carbonate production as the main driver of the geometries observed at the toe of slope.     

珠江口盆地东沙隆起生物礁地质及地震特征

东沙隆起珠江组生物礁是珠江口盆地重要的储层类型,礁灰岩主要为珊瑚藻灰岩,分为骨架岩、粘结岩及障积岩。研究区生物礁发育于开阔台地、台地边缘及台地前缘斜坡3类沉积相中,生物礁类型可分为台内点礁、台地边缘堡礁及台缘斜坡塔礁,以台地边缘堡礁为主。珠江组沉积早期,东沙隆起发育滨岸砂质沉积;中期海水逐渐淹没东沙隆起,形成镶边浅水碳酸盐台地,发育生物礁;晚期海侵台地逐渐淹没消亡,被浅海陆棚泥质沉积代替。流花台地厚度最大,最厚达563m,台地顶面地震强反射使外形轮廓清晰,台地内部中-弱振幅至空白反射,连续性降低;惠州台地厚度较流花台地薄,厚度多大于100m,顶界面强反射轮廓清晰,内部层状反射能量强-中振幅、高-中连续、中-低频,局部空白反射;陆丰台地厚约30m,只有一个高连续的强振幅。生物礁地震响应以丘形、箱型、低丘-透镜状为特征,礁顶常为强振幅,内部为波状、有时见前积结构,翼部可见上超和披覆现象等。     

Seismic characteristics and development of the Xisha carbonate platforms,northern margin of the South China Sea

The Xisha carbonate platforms, which include the modern-day Xisha Atoll, occur upon the northern continental margin of the South China Sea (SCS). In this study, we identify the seismic characteristics about various sedimentary facies of the carbonate platform and different types of reef in this area, based on the 2-D seismic data, reefs show high-amplitue moundy continuous reflection at the top and weak chaotic reflections inside. Carbonate platforms show high-amplitude continuous reflection at the top and high reflection alternative with weak reflection. The above analysis provided information about the influence of fluctuations in relative sea level, tectonic movements, paleotopography and the development mechanism of the carbonate platform. Based on the seismic data and data from drillholes (Xichen-1, Xiyong-1), we propose a schematic sedimentary model of the Xisha carbonate platforms at the northern margin of the SCS and outline five stages of development for the carbonate platform. Its sedimentary evolution consists of Initial establishment stage, development stage, exposure stage, drowning stage and large atoll reefs development stage. We also propose that several phases tectonisms supply proper environment and structural position for carbonate platform development, they can also destroyed the exist platforms. Besides, eustasy change was also the main influential factor on the development of the platforms.     

Internal architecture of mass‐transport deposits in basinal carbonates: A case study from southern Italy

Submarine mass‐transport deposits represent important stratigraphic heterogeneities within slope and basinal sedimentary successions. A poor understanding of how their distribution and internal architecture affect the fluid flow migration pathway may lead to unexpected compartmentalization issues in reservoir analysis. Studies of modern carbonate mass‐transport deposits mainly focus on large seismic‐scale slope failures; however, the near‐platform basinal depositional environment often hosts mass‐transport deposits of various dimensions. The small‐scale and meso‐scale (metres to several tens of metres) carbonate mass‐transport deposits play a considerable role in distribution of sediment and therefore have an impact on the heterogeneity of the succession. In order to further constrain the geometry and internal architecture of mass‐transport deposits developed in near‐slope basinal carbonates, a structural and sedimentological analysis of sub‐seismic‐scale mass‐transport deposits has been undertaken on the eastern margin of the Apulian carbonate platform in the Gargano Promontory, south‐east Italy. These mass‐transport deposits, that locally comprise a large proportion (50 to 60%) of the base of slope to basinal sediments of the Cretaceous Maiolica Formation, typically display a vertically bipartite character, including debrites and slump deposits of varying volume ratios. A range of brittle and ductile deformation styles developed within distinct bed packages, together with the presence of both chert clasts, folded chert layers and spherical chert nodules, suggest that sediments were at different stages of lithification prior to downslope movement associated with mass‐transport deposits. This study helps elucidate the emplacement processes, frequency and character of subseismic‐scale mass‐transport deposits within the basinal carbonate environment, and thereby reduces the uncertainties in the characterization of subsurface carbonate geofluid reservoirs.     

Lithofacies and sequence development on an Upper Devonian mixed carbonate-siliciclastic fore-reef slope, Canning Basin, Western Australia

Detailed sedimentological and stratigraphical analysis coupled with conodont biostratigraphy of a fore-reef slope succession in the Napier Range (Napier Formation) is used to develop a depositional model and relative sea-level history for late Frasnian to late Famennian reef evolution in the Canning Basin of north-western Australia. Changes in sedimentary style on the slope, reflecting differing rates of carbonate production on the platform, are linked to third- and higher order relative sea-level fluctuations. Overlapping slope aprons accumulated along the base of a steep-walled platform margin. Coarse carbonate debris was deposited adjacent to the margin as talus breccias (via rockfall) and debris-flow breccias. Depositional slopes up to 45°, and locally steeper, are demonstrated using rotated geopetal cavity fills. The predominance of channel-filling lithofacies throughout the slope succession indicates the highly channelized nature of the aprons. The middle slope is dominated by sandy oolitic-peloidal turbiditic grainstones interpreted as sediment exported from an active platform. The turbidites and associated debris-flow breccias contrast with condensed carbonate intervals and deep-water, non-fenestral stromatolites that record times of very low platform production. Lower slope turbidites and associated intraclastic breccias indicate widespread redeposition of sediment eroded from lithified and semi-lithified limestones higher up the slope. Several third-order sequences are recognized in the fore-reef succession and these are composed primarily of transgressive and highstand deposits. Carbonate production was severely restricted in the early Famennian coinciding with development of onlapping siliciclastic aprons during a relative sea-level lowstand. Evidence for a subaerial exposure event is also preserved within the siliciclastic strata. Controls on sequence development are difficult to constrain. Although two sequence boundaries can be correlated with falls on the global sea-level curve, the reef complexes evolved in an active extensional regime and it is highly likely that tectonism, in conjunction with eustasy, controlled accommodation on the platform and therefore carbonate productivity.     

Tectonic, eustatic and environmental controls on mid-Cretaceous carbonate platform deposition, south-central Pyrenees, Spain

Cenomanian–Turonian strata of the south‐central Pyrenees in northern Spain contain three prograding carbonate sequences that record interactions among tectonics, sea level, environment and sediment fabric in controlling sequence development. Sequence UK‐1 (Lower to Upper Cenomanian) contains distinct lagoonal, back‐margin, margin, slope and basin facies, and was deposited on a broad, flat shelf adjacent to a deep basin. The lack of reef‐constructing organisms resulted in a gently dipping ramp morphology for the margin and slope. Sequence UK‐2 (Upper Cenomanian) contains similar shallow‐water facies belts, but syndepositional tectonic modification of the margin resulted in a steep slope and deposition of carbonate megabreccias. Sequence UK‐3 (Lower to Middle Turonian) records a shift from benthic to pelagic deposition, as the shallow platform was drowned in response to a eustatic sea‐level rise, coupled with increased organic productivity. Sequences UK‐1 to UK‐3 are subdivided into lowstand, transgressive and highstand systems tracts based on stratal geometries and facies distribution patterns. The same lithologies (e.g. megabreccias) commonly occur in more than one systems tract, indicating that: (1) the depositional system responded to more than just sea‐level fluctuations; and (2) similar processes occurred during different times throughout sequence development. These sequences illustrate the complexity of carbonate platform dynamics that influence sequence architecture. Rift tectonics and flexural subsidence played a major role in controlling the location of the platform margin, maintaining a steep slope gradient through syndepositional faulting, enhancing slope instability and erosion, and influencing depositional processes, stratal relationships and lithofacies distribution on the slope. Sea‐level variations (eustatic and relative) strongly influenced the timing of sequence and parasequence boundary formation, controlled changes in accommodation and promoted platform drowning (in conjunction with other factors). Physico‐chemical and climatic conditions were responsible for reducing carbonate production rates and inducing platform drowning. Finally, a mud‐rich sediment fabric affected platform morphology, growth geometries (aggradation vs. progradation) and facies distribution patterns.     

海西—印支期上扬子南缘碳酸盐岩台地边缘沉积特征、演化及其控制因素

海西—印支期上扬子地块发育稳定型的碳酸盐岩大台地,在碳酸盐岩台地南缘台地边缘沉积体系发育,主要包括4种沉积类型:台地边缘滩,台地边缘礁、台地前缘斜坡、滩(礁)间海。据海西—印支期台缘沉积发育及分布特征,可分为4个沉积演化阶段:中泥盆世—晚泥盆世(SS1),台缘沿弥勒—师宗—晴隆—南丹—河池一线呈带状分布,台缘礁滩发育;早石炭世—早二叠世早期(SS2-SS3),台缘沿晴隆—六盘水—安顺呈带状分布,台缘生屑滩发育;早二叠世晚期—晚二叠世(SS4),沿贞丰—紫云—罗店—河池—柳州—娄底呈带状分布,台缘滩、台缘礁交互发育;早三叠世—中三叠世(SS5),沿贞丰—镇宁—贵阳—福泉一线呈带状分布,早三叠世主要发育台缘鲕粒滩,中三叠世台缘礁占优势。这4个阶段的台缘沉积特征表明:台地边缘礁滩沉积体系垂向演化受海平面变化控制,横向迁移主要受同沉积断裂控制,不同类型生物的出现和绝灭控制台缘生物礁滩的类型及特征。