The carbonate factory of Middle Triassic buildups in the Dolomites, Italy: a quantitative analysis

Middle Triassic carbonate buildups of the Dolomites were high in relief (500–1000m) and small in size (one to a few square kilometres in area). A paradox results from the carbonate platform model that invokes the platform top, including reef rims, as the carbonate factory and flanking beds as talus deposits. Most buildups consist largely of clinoforms (inclined at 10-50°) whereas massive reef rocks and stratified buildup interiors are poorly developed or absent. Facies and modal analysis of 323 thin sections from buildups of the Marmolada indicate that clinoforms are: (i) predominantly composed of in situ boundstones (56% of all samples); (ii) primarily made up of early cements (37 vol.%), microbial crusts (17 vol.%), micritic intraclasts (10 vol.%) and Tubiphytes (8 vol.%); and (iii) contain diagnostic shallow water grains (dasyclads, coated grains) that are less abundant by 1-2 orders of magnitude compared with buildup interior facies. These data suggest that the clinoforms themselves were the main carbonate factory of the Triassic buildups. Stratified buildup interior rocks and massive reef rocks were apparently not a prerequisite for buildup growth and clinoform progradation.     

Distribution of Chancelloriids in a Middle Cambrian Carbonate Platform Deposit, Taebaek Group, Korea

The onset of the Cambrian witnessed the diversification of “small shelly fossils (SSF)”, which affected carbonate depositional system. One of the problematic SSF, chancelloriids, are common components of the early to middle Cambrian carbonate and shale, and their contributions toward Cambrian carbonates are not yet fully understood. This study assesses distribution patterns of chancelloriid sclerites in the Cambrian Series 3 Daegi Formation based on microfacies analysis and discusses their sedimentologic implications. In the lower part of the formation, partially articulated chancelloriid sclerites occur mainly in bioclastic packstone and grainstone facies, with isolated sclerite rays in nodular packstone to grainstone facies. In the middle part of the formation, chancelloriid fragments occur only sporadically in bioclastic wackestone to packstone, bioclastic grainstone and oolitic packstone to grainstone facies, whereas boundstone facies are nearly devoid of their fragments. There are no chancelloriid fragments in the upper part of the formation, which consists of oolitic packstone to grainstone facies. Chancelloriids are interpreted to have primarily occupied platform margin shoal environments, shedding their sclerites to surrounding areas, and thus contributed as sediment producers. The distribution of Daegi chancelloriid sclerites is similar to other Cambrian examples, with the exception of common chancelloriids in Cambrian Series 2 reefs and their apparent near absence in the Daegi and other Cambrian Series 3 reefs. This disparity resulted from changes in the ecologic niche of chancelloriids after the end-Cambrian Series 2 reef crisis, coupled with an overall decline of chancelloriids in the middle Cambrian.     

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.     

泰国北部三叠系Lampang群Doi Long组的有孔虫组合与沉积环境

A rich foraminiferal assemblage, consisting of abundant Aulotortus sinuosus and A. tumidus in association with Lamelliconus multispirus, Endoteba ex gr. controversa, E. ex gr. badouxi, Endotebanella kocaeliensis, Endotriada tyrrhenica, Endotriadella wirzi, Malayspirina fontainei, Ammobaculites rhaeticus, Diplotremina astrofimbriata, Agathammina austroalpina, and others, was found in the Doi Long Formation of the Triassic Lampang Group, Northern Thailand. These foraminifers suggest that the formation is referable to the Carnian (early Late Triassic), which is consistent with the age estimated by ammonoids. In microfacies, peloidal grainstone, bioclastic grainstone, sponge-microbial boundstone, and oolitic grainstone were recognized in the Doi Long Formation. Based on microfacies, three depositional facies, the lagoon facies, reef facies, and shoal facies, are recognized in this formation. These lines of evidence are suggestive that the Doi Long Formation was deposited in a reef or bank setting rather than a ramp setting.     

Origin of facies zonation in microbial carbonate platform slopes: Clues from trace element and stable isotope geochemistry (Middle Triassic,Dolomites, Italy)

Limestones containing radiaxial fibrous cements were sampled along the southern slope of the late Anisian (Middle Triassic) Latemar carbonate platform in the Dolomites, northern Italy. The Latemar upper slopes comprise massive microbial boundstone, whereas lower slopes are made of clinostratified grainstone, rudstone and breccia. Samples are representative of a seawater column from near sea‐level to an aphotic zone at about 500 m water depth. Radiaxial fibrous cements were analyzed for carbon (δ¹³C) and oxygen (δ¹⁸O) stable isotopic composition, as well as major and trace element content, to shed light on the origin of the slope facies zonation. The δ¹³C vary between 1·7‰ and 2·3‰ (Vienna Pee‐Dee Belemnite), with lowest values at palaeo‐water depths between 70 m and 300 m. Radiaxial fibrous cements yielded seawater‐like rare earth element patterns with light rare earth element depletion (Nd_SN/Yb_SN ≈ 0·4), superchondritic yttrium/holmium ratios (≈55) and negative cerium anomalies. Cadmium reaches maximum values of ca 0·5 to 0·7 μg/g at palaeo‐water depths between 70 m and 300 m; barium contents (0·8 to 1·8 μg/g) increase linearly with depth. The downslope patterns of δ¹³C and cadmium suggest increased nutrient and organic matter contents at depths between ca 70 m and 300 m and point to an active biological pump. The peak in cadmium and the minimum of δ¹³C mark a zone of maximum organic matter respiration and high nutrient and organic matter availability. The base of this zone at ca 300 m depth corresponds with the transition from massive microbial boundstone to clinostratified grainstone, rudstone and breccia. The microbial boundstone facies apparently formed only in seawater enriched in organic matter, possibly because this organic matter sustained benthic microbial communities at Latemar. The base of slope microbialites on high‐relief microbial carbonate platforms may be a proxy for the depth to maximum respiration zones of Palaeozoic and Mesozoic periplatform basins.     

Triassic carbonate buildup flanks in the Dolomites, northern Italy: breccias, boulder fabric and the importance of early diagenesis

The flanks of Middle Triassic carbonate buildups in the Dolomites show well‐developed clinostratification, with typical angles of 30–40°. This paper focuses on the metre‐scale fabric of these clinoforms and sets these within the context of their large‐scale and microscopic features. Clinoform stratification is caused by fibrous cement crusts, by stylolites paralleling a vague stratification and by pelagic limestone interbedded with the lower portions of the clinoforms. These parts of the clinoforms locally exhibit a boulder fabric. A fracture system, subvertical to clinostratification, is filled by fibrous cements and marine internal sediment. The analysis of clinoform fabric indicates that parts consist of in situ automicrite. Other parts of the clinoforms are made up of breccia. The breccias occur as isolated pockets and lenses with random orientation and dimensions ranging from a few square decimetres to hundreds of square metres. The breccias have gradual contacts with the unbrecciated host rock. Breccia components are mostly angular, show a microfacies similar to that of the unbrecciated host rock and are composed of millimetre‐ to decimetre‐sized particles that generally float in radiaxial‐fibrous cement. Matching grain boundaries are common. Calcite cement typically makes up 20 and 40 vol.% of the brecciated areas. Clinostratification, the fracture system, brecciation and boulder fabric point to gravity induced deformation of in situ flank deposits rather than gravity induced depositional processes. Brecciation appears to result from translational sliding (millimetres to metres) on the steep buildup flanks, which caused fracturing of the vaguely stratified automicrite, followed by displacive growth of fibrous cement. Cementation occurred in a (shallow) burial, marine phreatic environment, because cement clasts are virtually absent from the flank‐derived gravity flows in the adjoining basinal sediments. Displacive cement growth indicates a volume increase of the clinoforms during diagenesis of up to 20–40 vol.% and can account for the local drag of buildup interior limestones. Similarly, the boulder fabric appears to be a diagenetic feature, which resulted from differential settling of incompletely lithified boundstone and grainstone, and the interbedded pelagic limestone.     

Microencruster-microbial-cement framework of the Upper Jurassic reef developed on the slope of the intra-Tethyan carbonate platform (Bulgaria)

The carbonate succession in the Lyalintsi section of the western Moesian Platform (western Bulgaria) displays a shallowing-upward trend. Growth of the Tithonian–Valanginian coral biostromes and low-relief bioherms was preceded by Oxfordian–Kimmeridgian sedimentation of fine-grained peloidal-bioclastic limestones and Saccocoma-bearing limestones on the homoclinal ramp and the carbonate platform slope. In the late Kimmeridgian, boundstones with very rare corals, but with easily recognisable biohermal morphology, were developed. The main components of this reef are encrusting microorganisms, microbial crusts and synsedimentary cements. Microencrusters Labes atramentosa, Crescentiella morronensis, Perturbatacrusta leini and Radiomura cautica, as well as thin crusts of calcified sponges (sclerosponges), are the main biotic components. Corals (almost exclusively microsolenids) are sparse, whereas photophilic microencrusters (e.g., “Lithocodium–Bacinella”), are absent, although they are common in the overlying shallow-water part of the Lyalintsi sequence. Microbialites and synsedimentary cements provided additional support for the reef framework. The framework, especially the biotic components, and the reefal facies position within the sedimentary succession, implies that the high-energy upper slope of the carbonate platform was the depositional setting of the microencruster-microbial-cement reef studied. Encrusting microorganisms, except for C. morronensis and sponges, are only known from the intra-Tethyan platforms. This study supports conclusion of studies of coeval Alpine reefs that the presence of the microencruster-microbial-cement framework provides insight into the palaeobathymetry, palaeogeography and tectonic configuration of the intra-Tethyan carbonate platforms.     

珠江口盆地流花油田新近系生物礁灰岩储层特征及成因分析

南海珠江口盆地东沙隆起流花油田新近系灰岩储层为典型的台地边缘生物礁储层。岩石类型包括皮壳状珊瑚藻黏结灰岩、缠绕状珊瑚藻-珊瑚骨架灰岩、泥晶有孔虫-珊瑚藻颗粒灰岩、亮晶有孔虫-珊瑚藻颗粒灰岩、含红藻石灰岩、泥晶珊瑚颗粒灰岩、生屑泥晶灰岩7类。孔缝类型丰富,包括泥晶基质溶孔、粒间溶孔、藻架溶孔、粒内溶孔、铸模孔、体腔孔、晶间微孔7类孔隙及溶蚀缝、珊瑚藻皮壳间隙缝、似缝合线溶蚀缝、构造缝4类裂缝。划分了孔洞-网状裂缝型、孔隙型、裂缝-孔洞型、致密裂缝型4种储集类型。皮壳状珊瑚藻灰岩属于孔洞-网状裂缝型储层,泥晶颗粒灰岩、含红藻石灰岩和红藻石灰岩属于孔隙型,珊瑚骨架灰岩属于裂缝-孔洞型,亮晶生屑灰岩和胶结作用较强的皮壳状藻灰岩属于致密裂缝型。沉积微相和成岩作用控制了不同储集类型的分布,生物礁形成过程中的多期暴露对沉积微相和储集空间有重要影响。沉积-成岩演化过程划分为早期成礁与早期暴露、晚期成礁与次级暴露、埋藏压实与泥岩再造水改造阶段、两期成藏与地下水溶蚀4个阶段。根据沉积-成岩演化分析,预测了研究区储集类型空间分布。     

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.     

A steep-fronted Carboniferous carbonate platform: clinoformal geometry and lithofacies (Picos de Europa, NW Spain)

A steep‐margined carbonate platform is developed in the Carboniferous synorogenic foreland basin of northern Spain. Dips of 60–90° produced during Late Carboniferous thrusting enable cross‐sections of a 4‐km‐wide portion of the marginal area of this platform (Las Llacerias outcrop) to be studied in aerial photographs at a seismic scale. Three stratal domains are observed: (1) a horizontal‐bedded platform; (2) a clinoformal‐bedded margin with a relief of up to 500 m; and (3) a low‐angle toe‐of‐slope, where slope beds interfinger with basin sediments. The slope shows well‐bedded sigmoidal clinoforms with depositional dips ranging from 15° to 32°. Based on lithology and stratal patterns, four facies groups have been recognized: (1) a flat‐topped platform, in which thick algal boundstone, skeletal packstone–grainstone and peloidal micrite wackestone with a poorly rhythmic character prevail; (2) the platform margin and upper slope, characterized by microbial boundstone spanning a bathymetric range of ≈150 m measured from the break of slope; (3) a slope, predominantly composed of margin‐derived rudstones and breccias; and (4) a toe‐of‐slope to basin zone, where a cyclic alternation of spiculitic siltstones, packstone to grainstone calciturbidites and rudstone/breccia is visible. Five successive stages of platform development are deduced: (1) Bashkirian: flooding of the pre‐existing Serpukhovian platform giving rise to the nucleation of a low‐angle ramp to the south‐east of the study area with microbial mud‐mound accumulations, and breccias and calciturbidites on the margins; (2) Early Moscovian: an influx of siliciclastic sediment buried part of the platform and reduced the area of carbonate sedimentation; (3) Moscovian: aggradation and progradation of the carbonate system produced an extensive steep‐margined and flat‐topped shallow‐water platform (shelf system); (4) Latest Moscovian–earliest Kasimovian: drowning of the platform; and (5) Kasimovian: covering of the platform by marly calcareous ramp sediments.     

Facies, geometry and geological significance of Late Ordovician (early Caradocian) coral bioherms: Lourdes Formation, western Newfoundland

Late Ordovician coral bioherms in the Lourdes Formation of western Newfoundland exhibit a complex mixing of architectural elements, including framework, boundstone and suspension deposits. The bioherms occur within a narrow (16 m) stratigraphic interval, and a prominent unconformity truncates the interval of bioherm growth and tops of many of the bioherms. The buildups developed along a carbonate ramp. They occur isolated and in groups, individuals in groups are aligned in parallel orientation. The sizes of the bioherms range from small (50–100 cm) coral piles to columnar and dome‐shaped masses (1–15 m); however, topographic relief was never more than ≈1 m. Bioherm construction reflects: (i) stacking of the tabulate coral Labyrinthites chidlensis, and less common stromatoporoids; (ii) accumulation of microbial‐stromatoporoid boundstone and suspension deposits within shelter cavities between corals; and (iii) detrital bioherm‐flank skeletal grainstone beds. Trypanites borings are common in the tops of coral heads. The bioherms exhibit three growth‐development stages: (i) seafloor stabilization, wherein rare, abraded coral colonies lie scattered within pelmatozoan/skeletal grainstone lenses; (ii) colonization, wherein corals (L. chidlensis), rare stromatoporoids (Labechia sp.), and other biota (bryozoans) produced a bioherm overlying the basal sediment base; and (iii) diversification, which is marked by a more diverse range of fauna and flora as well as occurrence of shelter‐cavity deposits. The diversification stage usually makes up more than 70% of a bioherm structure, and, in some defines multiple periods of start‐up and shut‐down of bioherm growth. The latter is defined by bored omission surfaces and/or deposition of inter‐bioherm sediment. The Lourdes bioherms have a similar ecological structure, biotic diversity and depositional environment to patch reefs in the equivalent Carters Limestone in Tennessee. The mixture of coral stacking and boundstone as architectural elements identify an Early Palaeozoic transition of reef‐design development along shallow‐water platforms that began to displace the muddy (boundstone, bafflestone) carbonate buildups more typical of the Early and Middle Ordovician time.     

Facies and sequence stratigraphic architecture of the Mural Limestone (Albian), Arizona: Carbonate response to global and local factors and implications for reservoir characterization

This study documents the detailed facies and sequence stratigraphic architecture of a multi-cyclic patch-reef and its associated ramp interior facies that formed during Oceanic Anoxic Event 1b in the Mural Limestone, Arizona, USA. Ramp interior facies are comprised of bedded wackestone/packstone, rudist build-up and coral–algal patch-reef facies located north of Bisbee, Arizona, at the Grassy Hill locality. The larger multi-cyclic patch-reef that developed coevally ca 5 km to the south of Grassy Hill consists of a high-angle windward margin with a narrow ca 70 m long reef frame containing vertically zonated Microsolena, Actinastrea, diverse branching coral and rudist assemblages, and an 870 m long low-angle leeward margin comprised of reef debris rudstone and grainstone shoal facies. Similar reef geomorphology and orientation is documented across the Gulf of Mexico and reflects the shelf-wide north to north-east-trending prevailing wind and current energies. Controls affecting reef formation and growth patterns include changes in accommodation space associated with low-amplitude global sea-level rise and regional thermotectonic subsidence, local accommodation space and nutrient fluctuations associated with the inner shelf depositional setting within a humid and siliciclastic-rich environment. Four aggradational to retrogradational high-frequency sequences are documented in Arizona: High-frequency sequences 1 and 2 represent the first pulse of patch-reef development in an overall second-order marine transgression over the Sonora/Bisbee Shelf. These sequences correlate to δ¹³C signatures associated with Oceanic Anoxic Event 1b across the Gulf of Mexico and suggest that carbonate reefs persisted on the ramp interior during this time. High-frequency sequences 3 and 4 record a second brief transgression and backstepping of reef facies followed by the final regression of shallow shelf carbonates that correlates to more robust patch-reef development in Sonora, Mexico. The patch-reef at Paul Spur is an excellent outcrop analogue for productive patch-reefs in the Maverick Basin (Comanche Shelf) of Texas. Detailed facies mapping of this outcrop analogue shows that the greatest reservoir potential is contained within the backreef grainstone shoals where primary porosity of up to 15% is observed.     

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。     

贵州中三叠世生物礁

贵州中三叠世生物礁,早在六十年代中期,殷鸿福、杨遵仪就已提出线索。作者在六十年代初研究贵州三叠纪地层时,已对三叠系相变带的特征和规模,以及板庚碳酸盐岩体有了初步认识。七十年代初,作者又到花江进行调查,发现一套壮观的藻礁灰岩。     

四川盆地仪陇-平昌地区二叠系长兴组地震沉积学研究

为明确四川盆地仪陇-平昌地区长兴组地震相及沉积特征,运用地震岩性学和地震地貌学的综合分析技术,开展井-震结合及礁体三维识别研究,以阐明长兴组生物礁滩储集体的展布特征。研究结果表明,仪陇-平昌地区长兴组主要为四个沉积区带,开阔台地相对应平行-亚平行席状中弱断续地震相、台地边缘相对应平行-亚平行丘状或透镜状中弱地震相、台地前缘斜坡相对应前积席状弱地震相,海盆相对应平行-亚平行席状中强地震相,可细分为台缘礁、台内礁和台内滩亚相;30 Hz振幅调谐体切片揭示海盆岸线为北西向展布,25 Hz调谐体切片对于海盆线西侧的台缘带礁体和台内礁滩体反应明显;生物礁滩体的平面展布特征、发育规模受控于长兴组沉积期西南高、东北低的古地貌形态,台缘礁生长发育的有利区域为台地相带两排北西向凸起带。     

塔中地区晚奥陶世碳酸盐台缘与台内沉积差异--定性和定量的碳酸盐岩微相综合分析

为揭示塔中地区东部的晚奥陶世镶边型碳酸盐台地边缘与台地内部的沉积差异,利用钻井岩芯及薄片资料,对良里塔格组开展了定性的和定量的碳酸盐岩微相分析研究。研究表明,台缘-台内沉积区发育9种微相类型（MF1~MF9）,不同颗粒岩类微相所代表的几种颗粒滩具有典型差别的粒度累积频率曲线样式。台地边缘主要发育各种高能颗粒滩的微相组合（MF1~MF4）,与台缘生物礁构成礁滩复合体;台地内部主要发育代表中-低能的潮坪-潟湖沉积的微相组合（MF5~MF9）。结合定量的粒度分析分析认为生屑砂屑颗粒灰岩微相（MF1）、生屑砾屑灰岩微相（MF2）和鲕粒颗粒灰岩微相（MF3）是冲流带（前滨）环境的产物,分别代表着台地边缘生屑滩、鲕粒滩和礁前砾屑滩沉积;球粒颗粒灰岩微相（MF5）为位于受障壁的台地内部、中等能量波浪控制的球粒滩;棘屑泥粒灰岩-漂浮岩微相（MF4）发育于台缘礁后的中-高能生屑滩。     

贵州紫云晚石炭世叶状藻礁灰岩微相特征与沉积环境的研究

紫云晚石炭世叶状藻礁发育在碳酸盐岩台地边缘内。研究以碳酸盐岩微相分析为主要手段,对叶状藻礁剖面中岩石的微相特征和沉积环境研究。主要总结出6个微相类型,为生物碎屑粒泥灰岩、生物碎屑泥粒灰岩、球粒生屑泥粒灰岩、叶状藻粒泥灰岩—叶状藻泥粒灰岩、腕足泥粒灰岩、生物碎屑颗粒灰岩。总结了一个在开阔台地与台地边缘过渡带上的局部相模式,由较深水的开阔台地相、叶状藻礁相、台内斜坡相和台内较浅水的斜坡相、较浅水的开阔台地相、台内浅滩相过渡,分析总结了叶状藻礁的沉积环境。微相组合及其在剖面纵向分布规律显示,剖面的总体沉积环境为潮下带浅水开阔台地环境。      

Lithostratigraphy and standard microfacies types of the Neogene carbonates of Rabigh and Ubhur areas, Red Sea coastal plain of Saudi Arabia

The Neogene carbonate rocks have relatively small exposure relative to the siliciclastic and evaporite rocks in Rabigh and Ubhur areas, north Jeddah, Red Sea coastal plain of Saudi Arabia. The Miocene carbonates form small hills in both areas, which conformably overlie the siliciclastics, whereas the Pleistocene coral reefs form terraces facing the Red Sea in Rabigh area. The Neogene carbonates are represented by the following microfacies types: (1) dolomitic, oolitic, foraminiferal packstone; (2) sandy, dolomitic, intraclastic, foraminiferal packstone; (3) dolomitic and oolitic wackestone; (4) dolomitic, foraminiferal, intraclastic wackestone; (5) dolomitic mudstone; (6) coral boundstone; and (7) grainstone. The diagenetic processes affecting these carbonates are compaction, dissolution, aggrading neomorphism, and replacement that took place during deposition, shallow burial, and uplift. Pervasive dolomitization by the seepage reflux mechanism is responsible for the mimic replacement of the calcite of the original component of the limestone with dolomite. Sediments, biota, and lithofacies characteristics of the studied carbonate rocks of Rabigh and Ubhur areas indicate the presence of three facies zones; these are (1) FZ 5 platform margin reefs, (2) FZ 6 (platform margin sand shoals), and (3) FZ 7 platform interior-normal marine. The standard microfacies types are represented by (1) SMF 12, limestone with shell concentration; (2) SMF 15, oolitic wackestone and packstone; and (3) SMF 18, bioclastic grainstone and packstone with abundant benthic foraminifera.     

西藏改则热那错上三叠统日干配错组碳酸盐岩岩石学特征与沉积环境*

西藏改则县热那错东沟剖面上三叠统卡尼阶至瑞替阶日干配错组沉积了厚度较大的碳酸盐岩地层,其中化石丰富。在碳酸盐岩中识别出11种主要的岩石类型：灰泥灰岩﹑含生物碎屑灰泥灰岩、生物碎屑粒泥灰岩、生物碎屑泥粒灰岩、内碎屑泥粒灰岩、内碎屑颗粒灰岩、藻颗粒灰岩、多种类型鲕粒灰岩、单一类型鲕粒灰岩、球粒泥粒灰岩和生物礁灰岩。根据岩石特征及组合类型可划分为5种沉积相：陆源碎屑滨岸相、局限台地相、开阔台地相、台地边缘浅滩相和台地边缘礁相,它们共同构成了日干配错组4个有序的海侵—海退旋回,整体显现出海侵的相序结构。     

贵州玉屏彰寨奥陶纪红花园期障积岩隆礁

该障积岩隆礁的造礁生物主要为海绵和藻,岩石类型有海绵灰岩、藻席岩、核形石凝决石灰岩、生物屑灰岩等。本文系统介绍其造礁生物的生态特征、岩石组合并分析其沉积相和礁的生长发育阶段,最后运用马尔柯夫概型分析研究期旋回沉积发育较好的礁核相地层的学积特征。