Neoproterozoic Molar-tooth Structure and Constraint of Depositional Facies and Environment in the North China Platform in Jiangsu, Anhui and Liaoning, Eastern China

Molar tooth structure （MTS） represented by complex ptygmatical shapes is widely distributed in the Proterozoic of the world. MTS filled by fine, equant sparry calcite （or dolomite） displays an abrupt contact with hosting rocks, which are mainly composed of carbonaceous micrites and fine-grained carbonates with local silts and stormdominated deposits with graded, cross or wave beddings, numerous erosional surfaces and truncated and fills or guttered bases. Occurrence of MTS suggests a result of the constraint of sedimentary facies, and the storm-base in ramp settings is the maximum depth for the formation of MTS. Vertical succession of MTS-bearing carbonates shows a deposition stacked by high-frequency shallow subtidal and peritidal cycles. An individual cyclic MTS-bearing sequence is characterized by thinning, shallowing and dynamic decreasing-upward, and peritidal caps of purple red iron and organic carbonaceous sediments with more complicated shapes of MTS are common on the top of individual MTS-bearing sequences.

Facies Analysis, Depositional Environment and Diagenetic Features of the Qom Formation in the Saran Semnan, Central Iran

In this study, to identify and analyze facies of depositional environment and depositional model of Qom Formation, stratigraphic Saran Section (southwest of Semnan) was selected. Qom Formation in Saran section includes about 380 meters of conglomerate at the base, chalk, limestone, marl, and shale. Petrographic studies with facies analysis have led to the identification of 12 microfacies, these microfacies have been deposited in four facies groups including tidal flat, lagoon, barrier and open marine. Study of horizontal and vertical facies changes and their comparison with recent and ancient environments reveals that Qom Formation in this section relates to shallow marine environment and its facies were deposited in a shelf carbonate platform and are comparable with contemporary shelf platforms such as Florida and old shelf platforms such as Mozduran. The most important diagenetic processes affecting the studied section include micritization, bioturbation, cementation, dissolution, neomorphism, fracturing, mechanical and chemical compaction, hematitization and dolomitization. These processes have formed in marine, meteoric and burial diagenetic environments.

Facies, Sedimentary Environment and Sequence Stratigraphy of Dalan Formation in South Fars, Iran —(Qatar-South Fars Arch) Well ASL-A

Dalan Formation is one of the most important gas reservoirs of south and southwest Iran which it belongs to Dehram Group and its age is Middle to Late Permian. The Dalan formation is interpreted as reflecting a major tectono-eustatic event related to the onset of rapid thermal subsidence of the early Neo-Tethys passive margin in Arabia and Iran, and the drowning of its rift shoulders. The Dalan formation consists mainly of medium to thick-bedded oolitic to micritic shallow-marine carbonate, with intercalations of evaporates. This formation overlies the Faraghan formation and extends up into the Lower Triassic kangan formation. The current paper is focused on the facies, sedimentary environment and sequence Stratigraphy study of the Middle to Upper Permian Dalan formation in the West Assaluyeh gas field the subsurface section of well ASL-A. Based on microfacies analysis and significant founa and flora, nineteen major facies in five facies associations including Tidal flat (A), Lagoon (B), Shoal (C), Open marine (D) and Mid ramp (E) were recognized in the Dalan formation. Facies analysis and those comparisons with modern and ancient environments indicated that the Dalan formation was deposited inner to mid parts of a homoclinal ramp. The sequence stratigraphy studies on the Dalan formation in this gas field led to assessment of seven main sedimentary sequences of the third-order in the Assaluyeh field, well ASL-A. The boundary between the third-order sequences with the Faraghan formation and between the Nar and Upper Dalan members are Subaerial Unconformity (SU) and the boundaries between the third-order sequences with each other and also with the Kangan formation are Correlative Conformity (CC). The main diagenetic processes in this formation are dolomitization, dissolution, anhydritization, cementation and compaction which played a significant role in improving reservoir quality. The shoal ooid grainstone facies with intergranular and oomoldic porosity comprise the main reservoir facies of the Dalan formation.

Research on Diageneses of Cambrian Shoal Facies Carbonate Rocks in the Xiadong Area, Hubei Province

With continuous outcrops, developed shoal facies rocks, complete types of diagenesis and changeable diagenetic environments, Cambrian strata are well developed in the Xiadong area, Yichang, Hubei Province. Under the combined influence of numerous diageneses, secondary pores can be formed, which result in better reservoir properties of the rock strata.

Process-facies Types and Sequences of Devonian Volcanic Sedimentary Successions in Northern Xinjiang and Their Relation to Plate Tectonics

The process-facies types of the Devonian volcanic sedimentary successions in northern Xinjiang include explosive facies, effusive facies, pyroclastic-calcareous-terrigenous tempestite facies, and coarse^-, medium^- and fine-grained pyroclastic turbidite facies, volcanic eruption tsunamite facies, syndepositional and soft-deformed seismite facies, sandy and silt-muddy contourite facies. This paper presents their characteristics and diagnostic indicators, and discusses the temporal and spatial structures of both the process-facies and the environment-facies of the Zhifang section, east Junggar, and the Mount Sarburti section, west Junggar, and their relation to plate tectonism. The author holds that the facies analysis dominated by process-facies is the facies analysis' nucleus in an orogenic belt and active continental margin.

SEDIMENTARY CHARACTERISTICS OF SILTY CLAY FACIES IN THE SOUTH YELLOW SEA SHELF

Grain size analysis, X ray diffraction analysis and biostratigraphy analysis of the structure, composition and formation conditions of the neritic silty clay facies sediments extensively distributed in the central part of the South Yellow Sea showed that the sediments were composed of more than 70% clay, less than 30% silt, had very little or no sand, and were characterized by homogenous texture, soapy feeling, high plasticity, light green gray color and elliptical distribution being about 3 m thick in the center, being thinner towards the margin and finally thinning out. These shelf cyclonic eddy environment sediments formed a sedimentary facies different from that of the sediments in the neighbouring area and revealed the particular sediment dynamic pattern in the environment.

Paleoenvironmental Distribution Patterns of Sequence Stratigraphy in the Paleocene-Eocene Deposits of Sekonj Trough Event (Central Iran)

The Paleocene-Eocene successions were studied in Sekonj and Abaregh sections and located in South of Kerman in order to determine the microfacies, depositional environment and sequence stratigraphy. The deposits in the studied area are mainly composed of limestone, sandstone, conglomerate and shale. The obtained data from the field and laboratory observations led to identification of 11 microfacies which represent the coastal, tidal flat, lagoon, barrier and proximal open marine which were deposited in a carbonate-siliciclastic ramp environment. The sedimentology evidences, vertical analysis of microfacies, facies and relative sea level changes represent that the Paleocene-Eocene succession deposits have two 3rd depositional sequences in the studied area. The sequence 2 cannot be recognized completely due to the lack of outcrop. Sequence stratigraphic studies show an upward shallowing trend corresponding to the global sea level changes from the base to the upward of the succession.

Subsurface Facies Analysis of the Late Cambrian Mt. Simon Sandstone in Western Ohio (Midcontinent North America)

The Cambrian Mt. Simon Sandstone (MSS) is a possible unconventional gas reservoir in the Illinois, Michigan, and Appalachian Basins, but comparatively little is known about the unit. This study used core and well logs from two deep exploratory wells to interpret the depositional environment of the MSS under western Ohio, where the MSS is about 120 m thick and found 1060 m below ground surface. In western Ohio, the MSS unconformably overlies the Precambrian Middle Run Formation, is conformably overlain by the Cambrian Eau Claire Formation, and has a distinctive gamma-ray log-signature. In well DGS-2627, the MSS consists of tan, friable, moderately sorted, rounded, coarse- to very coarse-grained siliceous quartz arenite with minor heterolithic sandstone-mudstone couplets (rhythmites) and quartz granule conglomerate. Features indicative of tidally-influenced, shallow marine settings include tidal rhythmites, lenticular-, flaser-, and wavy-bedding, herringbone cross-bedding, mud-drapes, tidal bundles, reactivation surfaces, intraclasts, and bioturbation. The unit generally coarsens- and thickens-upward, and is interpreted as migration of a tidally-influenced transgressive barrier sequence. A subsurface facies model for the MSS is developed by interpreting geophysical logs and cores from DGS-2627l, and this model is semi-quantitatively tested by first interpreting well BP-4 using geophysical logs alone, then confirming the results using core.

沉积成因Sr/Ba指示的福建潮控海湾全新世沉积环境及海平面意义

福建沿海多发育潮控型海湾,潮滩平坦宽广,海湾水深较浅,有孔虫等微体生物较为匮乏,且其化石在地层中保存相对较差,致使沉积微相辨识存在一定难度,从而限制了深入理解该区全新世海平面变化过程及沉积环境响应。本研究拟利用不受保存环境限制的沉积成因Sr/Ba指标,探索其在福建宁德三沙湾地区沉积微相的辨识潜力,并结合AMS 14C年龄,探讨该区全新世以来的沉积环境演化及区域海平面变化。结果表明:①沉积成因Sr/Ba在三沙湾潮滩和海湾表层沉积物中平均值分别为9.06和20.43,具有显著差异。潮滩沉积物中的Sr/Ba明显高于长江等大河口地区(1~3),这是该区淡水输入量较少、潮滩盐度较高所致,这说明该指标辨识海陆过渡沉积相时需要考虑区域水文特点。②晚第四纪NDGK2钻孔沉积物Sr/Ba自下而上可分为3层(Ⅰ—Ⅲ):层Ⅰ为杂色硬黏土,Sr/Ba比值全孔最低(均值5.29),但也高于淡水环境,推测为前期海相沉积物的暴露改造;层Ⅱ—Ⅲ均为深灰色黏土,其中层Ⅱ均值为10.77,接近潮滩相;层Ⅲ均值为全孔最高(13.44),接近海湾相。结合AMS 14C年龄可知,NDGK2钻孔的河漫滩-潮滩-海湾沉积相演化受控于全新世海平面上升过程,潮滩相形成于约8.9 cal.kaBP,当时该区海平面大约在−21.0±2.5 m,最大海泛面出现于约8.2 cal.kaBP,之后出现了长达6 ka的低沉积速率时期,直至约2.2 cal.kaBP海湾内加速沉积。③该区15个钻孔全新统底部Sr/Ba均显现出明显的潮滩相特征,这为重建区域全新世相对海平面提供了可行性。

基于微电阻率成像测井图像的琼东南盆地松涛隆起新近系沉积相研究

沉积相分析是恢复古地理环境、进行油气储层、烃源岩和盖层预测,为油气资源勘探开发服务的常用手段之一。基于微电阻率成像测井图像的精细解译,结合岩心、录井、常规测井与相关实验等资料,在岩心刻度微电阻率成像测井图像的基础上,以沉积学理论方法为指导,对琼东南盆地松涛隆起新近系的岩性、岩石序列组合和沉积构造等进行了识别,并以此为相标志进行了沉积相分析,建立了研究区新近系的沉积相模式。研究结果表明:(1)从琼东南盆地新近系高清微电阻率成像测井图像上共识别出泥岩、粉砂岩、细砂岩、中砂岩、粗砂岩等共5类岩性,岩性较为复杂,整体粒度较细,粒径跨度很大,垂向上岩性呈现明显的旋回性。(2)根据琼东南盆地松涛隆起新近系高清微电阻率成像测井图像中不同形态线条的组合方式,结合倾角矢量模式,共识别出5类层理类型(水平层理、波状层理、板状交错层理、槽状交错层理和块状层理),此外还识别出了钙质结核和生物扰动构造。(3)琼东南盆地松涛隆起新近系沉积环境总体为滨-浅海相、半深海和深海相沉积,局部层段发育浊流沉积;沉积演化规律表现为在渐新世晚期陵水组沉积时期全区发生海进,接受了滨海三角洲为主的各类沉积作用;到中新世早期的三亚组和梅山组沉积时期,沉积环境逐步由滨岸沉积环境过渡到浅海和半深海沉积;至黄流组和莺歌海组沉积期海水进一步加深,出现了半深海和深海沉积;而到莺歌海组沉积末期,发生了缓慢的海退,逐步变为半深海沉积。

四川盆地仪陇—平昌地区侏罗系凉高山组页岩油地质特征及富集条件

基于钻井岩心的地球化学及其他实验分析结果,结合生产测试资料,对四川盆地仪陇—平昌地区侏罗系凉高山组页岩油地质特征及富集条件进行研究,并划分了勘探有利区。研究结果表明:(1)仪陇—平昌地区凉高山组为早侏罗世第3次湖盆扩张期的沉积产物,整体经历了凉下段滨湖—浅湖、凉上段中—下部深湖—半深湖及浅湖、凉上段上部三角洲前缘和浅湖的沉积环境变化。(2)研究区凉高山组页岩可分为长英质页岩、钙质页岩、黏土质页岩等3种;页岩有机质丰度高,TOC值为0.50%~3.39%,平均值为1.30%,有机质类型以Ⅱ_(1)和Ⅱ_(2)型为主,热演化程度高,镜质体反射率(Ro)为1.00%~1.90%,处于高—过成熟阶段。(3)凉高山组页岩物性较好,孔隙度为0.48%~7.17%,平均为3.61%,发育无机成因孔、有机孔和构造缝等储集空间类型;含油性较好,以轻质组分为主,整体呈零散状、点状分布,局部呈团块状富集;凉上段下部富有机质页岩更发育,是目前勘探的重点层位。(4)凉高山组页岩油气的富集受控于前陆盆地过渡期的弱沉降环境、大面积分布的深湖相沉积、较高的热演化程度以及普遍发育的微裂缝。中南部为页岩油气潜力区,页岩储层厚度一般大于15 m,TOC值大于1.50%,孔隙度大于4.00%,R_(o)大于1.30%;凉高山组页岩油资源量为26.75×10^(8)t、页岩气资源量为1.72×10^(12)m^(3),有望成为四川盆地石油产量增加的主力层系。

西藏南部绒布地区上白垩统宗卓组沉积相与沉积环境演化

宗卓组地层作为中生代海相沉积的重要组成部分,记载了西藏南部地区白垩纪古海洋、古气候等重要地质历史信息。通过对砂岩进行镜下观察、物源分析、粒度分析等方面的研究,笔者等对绒布地区上白垩统宗卓组的沉积相类型和沉积环境演化有了新的认识。粒度分析指示沉积时期水体搬运动力较弱、存在浊流沉积;宗卓组内3种不同类型的砂岩镜下特征、地球化学特征和锆石U-Pb年龄,指示3类砂岩的物源不同。笔者等在宗卓组共识别出陆棚相、大陆斜坡相和深海盆地3类沉积相,并对其进行了更为详细的划分。晚白垩世新特提斯洋壳向北俯冲,俯冲结束后印度—亚洲大陆发生初始碰撞。结合研究区构造背景分析,笔者等推测这是导致研究区沉积环境由半深海环境变为深海环境的原因。对研究区宗卓组地层和砂岩来源进行分析后得出:在洋壳俯冲阶段,宗卓组为被动大陆边缘沉积;在之后印度—亚洲陆陆碰撞的初始碰撞阶段,特提斯喜马拉雅被动陆缘已不复存在,并完全过渡为前陆盆地。

南皮地区石盒子组沉积微相特征与有利储集相研究

大港南皮地区目的层石盒子组碎屑岩砂体分布广泛、厚度大,但沉积展布及有利储集相分析并不完善。为此,以沉积环境研究为基础,依据测井沉积学理论,利用测井曲线形态特征与岩性剖面的对应关系,对研究区单井沉积微相精细解释与划分。运用均方根振幅属性切片技术,分析了沉积相空间展布规律。研究表明,石盒子组曲流河相沉积体系主要有3种亚相7种微相,砂体由北东向南西展布。其中,河床滞留沉积相与边滩相主要以陆源砾石为主且粒度较粗,孔隙连通性好,在研究区是砂岩和储油物性最发育的层段。泛滥平原泥质含量高,孔隙喉道较窄,沉积颗粒细,储油性差。该区研究能为油气藏的合理高效开发和其他地区沉积研究提供理论依据。

塔里木盆地塔河地区中下奥陶统沉积特征及其演化模式

沉积环境对岩溶型储层的发育起着基础性作用,影响着岩溶体的规模和强度,加强沉积环境研究有助于优质岩溶储层的勘探与预测。为深入认识塔河地区中下奥陶统沉积特征,在野外调查基础上,结合岩石颜色、类型、组合、结构、构造、古生物、地球化学特征等岩石学和岩相学标志,利用岩心、测录井、地震和区域宏观沉积资料,对中下奥陶统沉积环境进行了精细识别和划分。结果显示,研究区岩石类型主要为颗粒灰岩、泥晶灰岩、生物灰岩和过渡岩类;共发育5种沉积环境,蓬莱坝组以局限—半局限台地为主,鹰山组以半局限台地、开阔台地为主,一间房组以开阔台地、台地边缘、淹没台地为主;共发育11种地震相,与各类沉积相带具有较明显的对应关系。总的来说,研究区以台地相为主,时空演化差异明显。纵向上,自蓬莱坝组至一间房组沉积水体逐渐加深,沉积环境由局限逐渐变为开阔;横向上,研究区主体以开阔台地、台地边缘为主,向东、向南至研究区外部逐渐过渡为斜坡、盆地相。综合前人资料,建立了研究区自下奥陶统蓬莱坝组局限台地→半局限台地→中下奥陶统鹰山组开阔台地→中奥陶统一间房组台地边缘→一间房组晚期、吐木休克组淹没台地的演化模式。

彬长矿区胡家河井田4号煤层沉积环境及聚煤规律研究

为研究彬长矿区胡家河井田4号煤层的沉积环境,总结聚煤规律,归纳聚煤模式,综合运用煤田地质学、岩石学、沉积学、构造地质学等多学科交叉研究方法,野外观察和室内分析相结合,对胡家河井田4号煤层的沉积环境及聚煤规律进行分析。结果表明:井田内含煤地层主要为内陆河流相沉积,其中河漫沼泽、牛轭湖以及泛滥平原上的泥炭沼泽是4号煤层的主要沉积环境;富煤带分布于中部及南部,并向东部和西部延伸,富煤中心分布于中部和西南部,与地层沉积中心有较好的对应关系;在靠近西部的古河道时,煤层出现分岔、变薄、尖灭的现象,古河道流经区域富县组和延安组地层全部缺失,形成无煤区。研究成果对于该矿煤炭资源的可持续发展以及提高煤炭资源开发和利用效率具有重要的理论与实践意义。

基于煤岩煤质煤相特征的沁水15号富锂煤古环境分析

以沁水东南部15号富锂煤为研究对象,采用显微光学、XRD等技术方法开展了宏观煤岩特征、显微煤岩特征、煤质特征和煤相研究。结果表明,沁水东南太原组15号煤属低水分、低灰分、低挥发分、高硫贫煤。宏观煤岩类型以半亮型、半暗型煤为主;显微煤岩组分以镜质组为主,惰质组次之,壳质组少见;无机显微组分以高岭石等黏土矿物为主,可见方解石、黄铁矿、石英、菱铁矿、石膏和锆石等矿物。15号煤形成于滨岸带沉积体系。古沉积环境主要为潮湿-浅覆水、强活水环境的开放沼泽相;植物组织保存程度较低,植物以水生或草本植物为主;成煤泥炭沼泽环境受地下水影响较小,海水影响较大,物源供给具有多元性。

石钱滩凹陷石炭系石钱滩组沉积环境与沉积相特征

准噶尔盆地石钱滩凹陷石炭系石钱滩组是重要的的烃源岩层系,该区石炭系巴山组天然气已证实来自石钱滩组,为早期生气阶段生成的煤成气(胡自龙等,2019)。受有限的地质资料影响,目前关于这套层系的研究主要局限于古生物、古气候等方面,关于沉积相类型及沉积体系方面的研究较少,导致有利烃源岩分布范围不明确。通过对石钱滩凹陷钻测井、露头以及分析测试等资料进行系统研究,查明了沉积环境与沉积相类型.

东昆仑三通沟北锰矿床沉积相与沉积环境

青海省三通沟北锰矿床是近年在东昆仑南部构造带上新发现的沉积型锰矿。初步研究表明,该锰矿赋存于奥陶—志留系纳赤台群硅质岩和细碎屑岩地层中,但目前该矿床研究程度较低,有关锰矿沉积相和沉积环境尚缺乏深入研究。在区域和矿床地质考察的基础上,通过典型地质剖面测量、室内镜下薄片鉴定和地球化学分析等研究工作,认为三通沟北锰矿形成于被动大陆边缘环境;矿区Ⅰ-Ⅲ主矿带形成于南部的深水盆地相,其岩性主要为硅质岩、硅质泥岩、碳质泥岩,夹泥质粉砂岩,其上与斜坡相砂岩和陆棚相砂岩—粉砂岩接触;矿区北部的Ⅳ-Ⅴ矿化带分布于陆棚相带中的局限洼地,岩性主要为泥质粉砂岩、硅质泥岩及硅质岩,含锰岩系顶板为陆棚相粉砂岩、细砂岩及碳酸盐相沉积。总体看,三通沟北锰矿形成于海相陆棚洼地和深水盆地的古地理环境。地球化学分析表明,三通沟北锰矿主矿带的形成与盆地相幕式富氧过程关系密切;锰矿的沉淀机制与通过斜坡相的密度流将浅部含氧水体幕式灌入到(近边缘)深水盆地的过程有关。

黄河下游原阳段沉积物粒度特征与沉积环境分析

为探究现代黄河下游沉积环境演化,在原阳段钻取了两个钻孔岩芯(YHX-1、YHX-2),通过对钻孔沉积物粒度测试与分析,运用沉积物粒度参数、频率曲线与概率累积曲线,结合沉积物岩性及周边钻孔年代信息,划分研究区钻孔地质年代,揭示研究区沉积水动力条件及环境演化历史。结果表明:YHX-1分为7个沉积段,YHX-2钻孔为11个阶段,中更新世时期,两根钻孔以中细砂为主,沉积相以河床亚相为主;晚更新世时期,钻孔经历短暂河漫滩微相,进入漫长的河床相沉积;全新世早期,YHX-1钻孔由湖泊沼泽沉积转变为河漫滩沉积,YHX-2钻孔为河漫滩沉积;全新世晚期,黄河改道流入当今河道,两根钻孔河床沉积相对比分析表明,改道后黄河主河道经历由北向南的变迁过程。

贵州遵义二叠纪锰矿地球化学特征与沉积环境分析:以遵义谢家坝富锰矿床为例

为分析贵州遵义二叠纪锰矿的沉积环境,对谢家坝锰矿床进行常量元素、微量和稀土元素地球化学研究。研究认为:谢家坝锰矿赋存于茅口组顶部含锰岩系中,分为下矿层豆状、角砾状菱锰矿、似层状菱锰矿,以及上矿层碎屑状、块状菱锰矿的二元结构矿石类型组合,可广泛代表遵义锰矿的矿石特征。谢家坝锰矿上下矿层之间主量元素和稀土元素含量差异较大,常量元素SiO_(2)、TiO_(2)、S、Fe_(2)O_(3)含量上矿层均大于下矿层,MnO、MgO与Al_(2)O_(3)之间均呈负相关关系;上矿层Fe/Mn值较高,属高Fe、低P型锰矿,而下矿层Fe/Mn值较低,属中低Fe、低P型锰矿。上矿层稀土元素PAAS标准化配分后呈现较明显的重稀土亏损、弱的轻稀土富集、右倾配分的特征,具有弱的Ce正异常,类似海底铁锰结核稀土元素特征;下矿层呈现弱的中稀土富集,轻、重稀土亏损,弱的帽式分配特征,具明显的Ce负异常,类似典型深部海水沉积稀土元素特征。微量元素Th/U、Ni/Co、V/Cr、V/(V+Ni)、AU等沉积环境古氧相分析指标和稀土元素PAAS标准化配分模式指示,谢家坝锰矿下矿层是在贫氧-厌氧条件下Mn^(2+)与CO_(3)^(2-)直接形成菱锰矿,上矿层在常氧-贫氧环境下Mn^(3+)、Mn^(4+)以氧化物或氢氧化物形式沉淀。