柴达木盆地西部新生界陆相湖盆碳酸盐岩沉积环境与沉积模式*

利用野外露头、岩心、测井录井和分析化验资料,对柴达木盆地西部(简称“柴西地区”)新生界干柴沟组湖相碳酸盐岩进行了研究,划分了其沉积微相类型,研究了其分布规律,分析其形成环境和控制因素,并建立了相应沉积模式。该区湖相碳酸盐岩在垂向上与碎屑岩频繁互层,湖相碳酸盐岩包括颗粒灰岩、藻灰岩、泥晶灰岩和混积岩4大类11种,划分出了灰泥坪、颗粒滩、藻丘(礁)、浅湖湾以及(半)深湖泥灰岩相等5种沉积微相。通过分析不同碳酸盐岩及其微相时空展布特征,认为其发育主要受控于湖盆构造运动、湖平面变化、陆源碎屑注入、古气候与古水介质条件、古地貌与古水深环境,并在此基础上建立了柴西湖相碳酸盐岩的沉积模式。研究认为柴达木盆地西部干柴沟组沉积时期,湖盆为典型咸化湖盆,构造活动相对稳定,湖平面上升达到峰值。碳酸盐岩主要发育在湖侵期,高频湖平面变化形成了碳酸盐岩与碎屑岩频繁互层。在枯水期,盆地坡折处发育碎屑岩滩坝或三角洲前缘沉积;在湖侵期,盆地坡折处发育了鲕粒滩及藻灰岩,盆地洼陷区发育泥灰岩或灰质泥岩。     

Deep-water stratigraphic cyclicity and carbonate mud mound development in the Middle Cambrian Marjum Formation, House Range, Utah, USA

Abstract In mid‐Middle Cambrian time, shallow‐water sedimentation along the Cordilleran passive margin was abruptly interrupted by the development of the deep‐water House Range embayment across Nevada and Utah. The Marjum Formation (330 m) in the central House Range represents deposition in the deepest part of the embayment and is composed of five deep‐water facies: limestone–argillaceous limestone rhythmites; shale; thin carbonate mud mounds; bioturbated limestone; and cross‐bedded limestone. These facies are cyclically arranged into 1·5 to 30 m thick parasequences that include rhythmite–mound, rhythmite–shale, rhythmite–bioturbated limestone and rhythmite–cross‐bedded limestone parasequences. Using biostratigraphically constrained sediment accumulation rates, the parasequences range in duration from ≈14 to 270 kyr. The mud mounds are thin (<2 m), closely spaced, laterally linked, symmetrical domes composed of massive, fenestral, peloidal to clotted microspar with sparse unoriented, poorly sorted skeletal material, calcitized bacterial(?) filaments/tubes and abundant fenestrae and stroma‐ tactoid structures. These petrographic and sedimentological features suggest that the microspar, peloids/clots and syndepositional micritic cement were precipitated in situ from the activity of benthic microbial communities. Concentrated growth of the microbial communities occurred during periods of decreased input of fine detrital carbonate transported offshore from the adjacent shallow‐water carbonate platform. In the neighbouring Wah Wah Range and throughout the southern Great Basin, coeval mid‐Middle Cambrian shallow‐water carbonates are composed of abundant metre‐scale, upward‐shallowing parasequences that record high‐frequency (10⁴?10⁵ years) eustatic sea‐level changes. Given this regional stratigraphic relationship, the Marjum Formation parasequences probably formed in response to high‐frequency sea‐level fluctuations that controlled the amount of detrital carbonate input into the deeper water embayment. During high‐frequency sea‐level rise and early highstand, detrital carbonate input into the embayment decreased as a result of carbonate factory retrogradation, resulting in the deposition of shale (base of rhythmite–shale parasequences) or thin nodular rhythmites, followed by in situ precipitated mud mounds (lower portion of rhythmite–mound parasequences). During the ensuing high‐frequency sea‐level fall/lowstand, detrital carbonate influx into the embayment increased on account of carbonate factory pro‐ gradation towards the embayment, resulting in deposition of rhythmites (upper part of rhythmite–mound parasequences), reworking of rhythmites by a lowered storm wave base (cross‐bedded limestone deposition) or bioturbation of rhythmites by a weakened/lowered O₂‐minimum zone (bioturbated lime‐ stone deposition). This interpreted sea‐level control on offshore carbonate sedimentation patterns is unique to Palaeozoic and earliest Mesozoic deep‐water sediments. After the evolution of calcareous plankton in the Jurassic, the presence or absence of deeper water carbonates was influenced by a variety of chemical and physical oceanographic factors, rather than just physical transport of carbonate muds.     

塔里木盆地阿克苏-柯坪地区寒武系-奥陶系的沉积环境

本文讨论了塔里木西北缘厚一千余米的寒武系-奥陶系暗色碳酸盐岩夹细碎屑岩系的沉积环境。寒武系以粉-细晶白云岩、微晶叠层石白云岩夹细碎屑岩为主;奥陶系以含硅粉-细晶白云岩、内碎屑岩、细碎屑岩与灰岩的混合岩互层为主。根据矿物成分、生物化石、结构构造、岩石的元素、稳定同位素、矿物组合等判断,其沉积环境为半封闭的潮坪环境至开阔的陆棚沉积环境。     

Tidal deposits of carbonate facies and their microfacies types in the Qiziqiao Formation of Middle Devonian,South China

Tidal-flat and shoal deposits of carbonate fades in the Qiziqiao Formation are widely distributed over the vast areas of Guangxi, Guangdong and Hunan provinces, constituting an important stratigraphic unit where strata-bound and stratiform ore deposits (galena-sphalerite-pyrite) are found. These types of ore deposit seem to have close relations to the tidal deposits. Recognition of tidal deposits is based upon rock fabric, texture, structure, fossil assemblage, and particular sedimentary cycle. The typical sequence of tidal-flat deposits consists mainly of three units:Amphipora limestone, laminated limestone and dolostone (from the bottom to the top). This sequence represents a complete process of sedimentation from low-tideflat through intertidal to high-tideflat or supratidal. The sequence of shoal deposits of carbonate facies consists chiefly of grainstone and algal oösparite. Two major types of tidal deposit (open and restricted marine facies) can be distinguished, with eleven microfacies as follows: 1) calcarenite (grainstone) with sparite (MF-1); 2) algal oösparite (MF-2); 3) oncolite (alga-, or stromatoporoid-encrusted grains) (MF-3); 4) bioclastic grainstone (biosparite) or rudstone with sparite (MF-4);5) Amphipora limestone (MF-5); 6) dark fossil-poor micrite (MF-6); 7) pelsparite or peloidal grainstone with sparite (MF-7); 8) laminated pellet mudstone-wackstone (MF-8); 9) micrite with onkoids (MF-9); 10) rudstone or floatstone (MF-10; and 11) bedded dolomite-gypsum-dolomite (MF-11).     

安徽巢湖二叠系栖霞组碳酸盐岩斜坡沉积

长期以来,人们均认为下扬子地区广泛发育的栖霞组碳酸盐岩属于浅海碳酸盐岩台地沉积。但以巢湖地区为例研究表明,栖霞组主要为碳酸盐岩斜坡沉积。碳酸盐岩碎屑流沉积物形成了臭灰岩段和顶部灰岩段的层状石灰砾岩,分布于斜坡上部;等深流沉积物形成了上、下硅质层段的砂屑硅质粒泥灰岩,主要分布于斜坡下部。而上、下硅质层段中的钙、硅质页 (泥 )岩属于斜坡远端和盆地沉积;唯有本部灰岩段可能属于浅海碳酸盐岩台地沉积。这一认识不仅突破了传统观念,而且有助于重新认识下扬子板块二叠纪的古地理特征和盆地构造演化。     

南海南部曾母盆地中新世碳酸盐岩的层序地层

利用钻井和二维地震资料, 对曾母盆地南康台地以及L构造中新统碳酸盐建造的三级层序发育特征进行解剖, 归纳总结研究区碳酸盐岩层序发育模式, 认为曾母盆地在中中新世-晚中新世(5.3~16 Ma)期间发育3期较大规模的碳酸盐岩沉积旋回, 在地层上可将其划分为3个三级层序, 即SQ1、SQ2和SQ3层序.其中SQ1与SQ3应该属于经典Ⅰ型碳酸盐岩层序, 在其岩性上由低位域的致密藻灰岩沉积、水进域的泥质灰岩和高位域的珊瑚灰岩组合构成, 代表了从开阔海沉积环境过渡至礁滩相沉积环境的发育过程;而SQ2应属于淹没不整合型碳酸盐岩层序, 以泥质灰岩凝缩层+高位域的珊瑚灰岩或碎屑灰岩序列组合为特征, 其发育基本处于水体环境持续变浅的沉积环境中.      

晚奥陶世五峰期扬子板块沉积模式

本文从沉积相分析及稀土元素地球化学特征来探讨扬子板块在晚奥陶世五峰期的沉积模式,认为五峰期扬子板块南部为古陆,东西北为断续分布的碳酸盐岩台地、生物礁和隆起区所环绕,中部为半封闭的浅水滞流海盆,稀土元素分析表明扬子扳块中部广泛分布的五峰组形成于陆浅海而非深海小洋盆。     

柴达木盆地西部地区第三系湖相藻(蓝细菌)灰岩储层成因类型

柴达木盆地西部地区第三系湖相藻(蓝细菌)灰岩储层的成因类型主要包括两类:滨湖亚相的藻(蓝细菌)坪灰岩和浅湖亚相的藻(蓝细菌)丘灰岩。滨湖亚相的藻(蓝细菌)坪灰岩和浅湖亚相的藻(蓝细菌)丘灰岩具有完全不同的沉积特征、岩石类型和储层特征。柴达木盆地第三系藻(蓝细菌)灰岩储层分布较广,是柴达木盆地第三系碳酸盐岩储层中最重要的油气储层。目前柴达木盆地第三系藻(蓝细菌)灰岩储层主要见于西部地区的跃西、跃东、七个泉、狮子沟、花土沟、尖顶山、南翼山和大风山等地区,层位上从下干柴沟组上段(E2₃)至上油砂山组(N2₂)均有分布。E2₃和N₁的藻(蓝细菌)灰岩主要分布于英雄岭凹陷以西(西南)地区,N1₂和N2₂的藻(蓝细菌)灰岩主要分布于英雄岭凹陷以东(东北)地区,这与柴达木盆地的湖水进退、沉积中心的迁移及盆地演化有着密切的关系。滨湖亚相藻(蓝细菌)坪灰岩储层的储集空间以次生溶孔和溶缝为主,溶孔和溶缝的形成与大气淡水的淋滤作用有关。浅湖亚相藻(蓝细菌)丘灰岩储层的储集空间以次生溶孔和溶缝为主,同时也发育原生枝管状钙藻(绿藻门的松藻科)的藻管孔,溶孔和溶缝的形成与晚期沿断裂带大气淡水的溶解作用及有机酸的溶解作用有关。     

The Messinian Sicilian stratigraphy revisited: new insights for the Messinian salinity crisis

Controversies around the Messinian salinity crisis (MSC) are because of the difficulties in establishing genetic and stratigraphic relationships between its deep and shallow‐water record. Actually, the Sicilian foreland basin shows both shallow and deep‐water Messinian records, thus offering the chance to reconstruct comprehensive MSC scenarios. The Lower Gypsum of Sicily comprises primary and resedimented evaporites separated in space and time by the intra‐Messinian unconformity. A composite unit including halite, resedimented gypsum and Calcare di Base accumulated between 5.6 and 5.55 Ma in the main depocentres; it records the acme of the Messinian Salinity Crisis during a tectonic phase coupled with sea‐level falls at glacials TG14‐TG12. These deposits fully post‐date primary gypsum, which precipitated in shallow‐water wedge‐top and foreland ramp basins between 5.96 and 5.6 Ma. This new stratigraphic framework results in a three‐stage MSC scenario characterized by different primary evaporite associations: selenite in the first and third stages, carbonate, halite and potash salt in the second one associated with hybrid resedimented evaporites.     

湘西吉首地区寒武系碳酸盐岩沉积环境的初步探讨

本文通过岩石组分、组构、沉积构造及岩石共生组合分析,认为湘西吉首地区寒武系碳酸盐岩主要形成在浅水碳酸盐台地.各类灰岩中的内碎屑、藻团粒、生物碎屑及低能鲕粒等颗粒类型广泛发育,白云岩中的残余组分及上述两类岩石普遍含有数量不等的陆源物并具各种流动浅水特征的沉积构造标志等事实支持了这一认识.与上述岩石共生间隔发育的砾屑灰岩(云岩)多属风暴沉积类型,在台地边缘斜坡上部-浅海陆棚环境中形成.     

川西北早志留世陆源碎屑──碳酸盐混积缓坡

研究区位于扬子地块西北缘，由一套巨厚的页岩、泥岩层夹生物礁及透镜状和不规则层状风暴生屑灰岩、瘤状灰岩组成。根据区内特征的岩石类型及其组合、分布和相应的化石生态，作者认为本区兰多维列期至早温洛克期时为一典型的陆源碎屑－－碳酸盐混积均斜缓坡，并且从浅到深划分为滨岸、浅缓坡、深缓坡及盆地等亚环境。滨岸区位于潮间带，以潮坪碳酸盐岩为代表；浅缓坡位于浪基面至风暴浪基面之间，岩性组合为Ａ、Ｂ类风暴岩，Ａ、Ｂ类瘤状灰岩、生物礁灰岩及粘结岩；深缓坡位于风暴浪基面至最大风暴浪基面之间，岩性以Ｄ、Ｅ类风暴岩、Ｃ类瘤状灰岩及泥页岩组合为特征；盆地处于最大风暴浪基面之下，为黑色泥页岩沉积。结合早志留世时全球冰川作用，文中讨论了海平面变化的原因及对环境的影响。     

西成铅锌矿田西部中泥盆统西汉水组碳酸盐岩沉积特征

运用岩石学和化石岩石学方法,论述了西成铅锌矿田西部中泥盆统西汉水组碳酸盐岩的沉积特征.西汉水组碳酸盐岩的组分以生物、生物碎屑、内碎屑和鲕粒最为重要;常见粒屑结构、花岗变晶结构、生物骨架结构及层纹-条带状构造;查明碳酸盐岩22种;西汉水组发育三种韵律,分别代表潮间、潮下的生物礁环境;并探讨了岩石类型与铅锌矿成矿的关系。     

A depositional model for the terminal Neoproterozoic–Early Cambrian Ara Group evaporites in south Oman

Abstract Six evaporite–carbonate sequences are recognized in the terminal Neoproterozoic–Early Cambrian Ara Group in the subsurface of Oman. Individual sequences consist of a lower, evaporitic part that formed mainly during a lowstand systems tract. Overlying platform carbonates contain minor amounts of evaporites and represent transgressive and highstand systems tracts. Detailed sedimentological and geochemical investigation of the evaporites allowed reconstruction of the depositional environment, source of brines and basin evolution. At the beginning of the evaporative phase (prograding succession), a shallow-water carbonate ramp gradually evolved into a series of shallow sulphate and halite salinas. Minor amounts of highly soluble salts locally record the last stage of basin desiccation. This gradual increase in salinity contrasts sharply with the ensuing retrograding succession in which two corrosion surfaces separate shallow-water halite from shallow-water sulphate, and shallow-water sulphate from relatively deeper water carbonate respectively. These surfaces record repeated flooding of the basin, dissolution of evaporites and stepwise reduction in salinity. Final flooding led to submergence of the basin and the establishment of an open-water carbonate ramp. Marine fossils in carbonates and bromine geochemistry of halite indicate a dominantly marine origin for the brines. The Ara Group sequences represent a time of relatively stable arid climate in a tectonically active basin. Strong subsidence allowed accommodation of evaporites with a cumulative thickness of several kilometres, while tectonic barriers simultaneously provided the required restricted conditions. Subsidence allowed evaporites to blanket basinal and platform areas. The study suggests a deep-basin/shallow-water model for the evaporites.     

震旦纪灯影组磷块岩及其生成特点

灯影组磷块岩有四种类型,即泥晶磷块岩、内碎屑磷块岩、藻磷块岩和细晶磷块岩。组成磷块岩的主要矿物是磷灰石、白云石、石英和少量伊利石等。磷块岩主要沉积在陆缘海内,它的沉积环境是与深水有联系的浅水地区。深水和浅水环境的地质背景分别为构造拗陷和碳酸盐岩台地。前者提供成矿物质,后者提供有利于磷质成矿的沉积环境。     

Upper Ordovician facies in the Lac Saint-Jean outlier, Québec (eastern Canada): palaeoenvironmental significance for Late Ordovician oceanography

Upper Ordovician (Caradocian) carbonates of eastern North America were deposited along the Iapetus continental margin and record a transition from warm- to cool-water settings despite this margin having been within the southern hemisphere tropical belt. This event has been documented from Virginia (USA) to southern Québec (Canada) although, not previously from areas close to the palaeoequator. Field, petrographic and major element geochemistry data have been gathered from the poorly-known Upper Ordovician carbonate succession outcropping in the Lac Saint-Jean outlier in central Québec. The succession consists of a lower siliciclastic formation (Tremblay) overlain by three limestone formations (Simard, Shipshaw and Galets) and capped by shales (Pointe-Bleue Shale). From macro- and microfaunal evidence, carbonate sedimentation occurred during the late Caradoc and is younger than the early- to mid-Caradoc carbonate succession present farther south. Relative sea level fluctuations recorded in the sediments suggest an overall sea level rise briefly halted by a minor end-Caradocian sea level fall. The lower limestone formation (Simard) consists of muddy sediments with algal-coral-stromatoporoid boundstones; green algae are abundant. This unit reflects low energy sedimentation on a shallow warm-water carbonate ramp colonized by a diverse chlorozoan fauna. The upper limestone formation (Galets) is typified by coarse-grained bioclastic sediments punctuated by numerous phosphate-rich hardgrounds with evidence for high energy shallow marine conditions. Faunas were dominated by crinoids and bryozoans. This unit represents high energy sedimentation on a cool shallow water carbonate ramp colonized by a brynoderm faunal association. Between both units, a deeper marine (outer shelf) limestone formation (Shipshaw) was developed. In the Lac Saint-Jean area, a transition from warm- to cool-water carbonate ramps occurred in latest Caradoc times and is litho- and biofacies-wise, similar to what is documented for lower Caradocian limestones present farther south. Upwelling of nutrient-rich cool bottom oceanic waters was a probable cause for this transition.     

广西合山地区合山组沉积相带和沉积模式

陆表海碳酸盐岩型含煤岩系是我国含煤岩系的一个重要类型,以广西晚二叠世合山组为代表。文中对该煤系中的碳酸盐岩进行了详细的微相分析,认为合山组沉积时期合山地区为温暖潮湿气候下的浅水环境,提出了包括浅海盆地、生物礁、开阔台地、潮坪和泥炭坪在内的陆表海碳酸盐台地沉积模式,并指出合山组碳酸盐台地边缘是以生物礁为代表的缓坡,最后对合山组的旋回层序进行分析,认为合山组沉积过程中,地壳沉降作用和海平面变化起了主导作用。     

新疆阿克苏地区中、上奥陶统碳酸盐岩磁化率与层序地层关系

通过对新疆阿克苏地区中、上奥陶统185块碳酸盐岩样品的磁化率测量和统计,结合碳酸盐岩微相分析和层序地层研究,探讨了碳酸盐岩磁化率变化与沉积环境、层序界面、准层序(组)等之间的关系。研究结果表明:深水低能环境下沉积的钙质泥岩、瘤状灰岩、泥灰岩等通常对应于磁化率低值,且磁化率曲线较为平直;浅水高能环境下形成的含鲕粒砂屑灰岩、鲕粒灰岩等通常对应于磁化率高值;碳酸盐岩地层中淹没型层序界面对应于磁化率测量值的明显减小;准层序(组)的上部单元碳酸盐岩磁化率值比下部单元明显增大,并且其曲线常呈高频振荡状。     

桂林地区上泥盆统碳酸盐岩沉积相

前言 桂林地区上泥盆统主要是一套海相碳酸盐地层,为岩溶发育的主要岩石之一。同期异相明显,可以划分为两个岩相:一是白云岩灰岩相,下部为桂林组,上部为融县组,整合接触,二是硅质岩扁豆状(瘤状)灰岩相,下部为榴江组,上部为三里组,整合接触。桂林组可与榴江组对比,属晚泥盆世早期沉积,融县组与三里组相当,属晚泥盆世晚期沉积。它们与下伏的中泥盆统东岗岭组为整合接触,而与上覆的下石炭统岩关阶呈整合或假整合接触关系。     

“干化蒸发”与“回灌重溶”——对鄂尔多斯盆地东部奥陶系蒸发岩成因的新认识

鄂尔多斯盆地东部奥陶系发育巨厚的蒸发岩地层,已有不少学者对其成因提出了不同的假设。本文通过对该区蒸发岩微相分布规律、剖面结构及地球化学等特征的分析,提出该区蒸发岩形成于成盐盆地与外海周期性隔绝的“干化蒸发”条件下的新认识。首次提出用“回灌重溶”机制来解释厚层石盐岩中的泥质薄夹层的成因、各种石盐岩颜色的成因及蒸发岩剖面中缺乏干化蒸发晚期阶段的钾镁盐层的原因,并由此提出 “溶积层”的概念。微相分析表明,在形成蒸发岩的盐坳盆地东部的水下古地形隆起上,发育有堤坝状的礁或生物丘等生物建隆,其在地形上的隆起构成了盐坳盆地与外海的障壁,在海平面下降期间可使盐坳与外海完全隔绝而进入干化蒸发阶段,从而形成了石盐沉积;由海平面上升所造成的突发性海水回灌事件又使先成的石盐层部分溶解（回灌重溶）,并由于不溶残余物的富集成层（溶积层）而阻止了下伏石盐层的进一步溶解。这是该区蒸发岩地层中缺少典型干化证据的主要原因。本区奥陶系马家沟组碳酸盐岩与蒸发岩间互分布的地层层序结构特征,主要受控于区域海平面变化旋回,碳酸盐岩主要形成于海侵期和高水位期,蒸发岩则主要形成于低水位期。     

Carbonate ramp-to-deeper shale shelf transitions of an Upper Cambrian intrashelf basin, Nolichucky Formation, Southwest Virginia Appalachians

The Nolichucky Formation (0–300 m thick) formed on the Cambrian pericratonic shelf in a shallow intrashelf basin bordered along strike and toward the regional shelf edge by shallow water carbonates and by nearshore clastics toward the craton. Lateral facies changes from shallow basinal rocks to peritidal carbonates suggest that the intrashelf basin was bordered by a gently sloping carbonate ramp. Peritidal facies of the regional shelf are cyclic, upward-shallowing stromatolitic carbonates. These grade toward the intrashelf basin into shallow ramp, cross-bedded, ooid and oncolitic, intraclast grain-stones that pass downslope into deeper ramp, subwave base, ribbon carbonates and thin limestone conglomerate. Ribbon limestones are layers and lenses of trilobite packstone, parallel and wave-ripple-laminated, quartzose calcisiltite, and lime mudstone arranged in storm-generated, fining upward sequences (1–5 cm thick) that may be burrowed. Shallow basin facies are storm generated, upward coarsening and upward fining sequences of green, calcareous shale with open marine biota; parallel to hummocky laminated calcareous siltstone; and intraformational flat pebble conglomerate. There are also rare debris-flow paraconglomerate (10–60 cm thick) and shaly packstone/wackestone with trace fossils, glauconite horizons and erosional surfaces/hardgrounds. A 15-m thick tongue of cyclic carbonates within the shale package contains subtidal digitate algal bioherms which developed during a period of shoaling in the basin. Understanding the Nolichucky facies within a ramp to intrashelf basin model provides a framework for understanding similar facies which are widely distributed in the Lower Palaeozoic elsewhere. The study demonstrates the widespread effects of storm processes on pericratonic shelf sedimentation. Finally, recognition of shallow basins located on pericratonic shelves is important because such basins influence the distribution of facies and reservoir rocks, whose trends may be unrelated to regional shelf-edge trends.