Depositional history of the early part of the Jurassic succession on the Rajasthan Shelf, western India

Part of the lowermost deposits of the Triassic to Earlymid Jurassic (up to Bajocian) sedimentary succession spread across the Rajasthan shelf on the western part of the Indian craton is found in the Jaisalmer Basin east of Jaisalmer with the best exposed sections along the Jodhpur-Jaisalmer Highway. Based on lithostratigraphic characteristics, the succession is divided into four: Odania and Thaiat members, Lathi Formation; and Hamira and Joyan members, Jaisalmer Formation. Six facies are defined from microfacies, sedimentary structures, biotic components and depositional environments: (1) ferruginous, pebbly, cross-bedded sandstone—high-energy, fluvial; (2) cross-bedded, poorly sorted, fossil wood-bearing sandstone—highenergy, terrestrial, with high influx of sediment and warm and humid climate; (3) cross-bedded to rarely bioturbated, alternating silt to fine-grained sandstone—fluctuating sedimentation rates and energy—nearshore, mesohaline embayment to lagoonal; (4) partly bioturbated, storm-dominated, mixed siliciclastic-carbonate facies—fully marine; (5) low angle cross-laminated, silt to fine-grained sandstone—nearshore shallow water, above fair weather wave base; and (6) thick rudstones with mega-ripples and reworked coral heads-storm deposits representing the peak of first major marine transgression across the basin.     

Depositional environments of Bathonian sediments from the Jaisalmer Basin, Rajasthan, western India

The pericratonic sedimentary Jaisalmer Basin, west of the Aravalli Ranges, on the westerly dipping eastern flank of the Indus Shelf, is a principal structural element of Rajasthan. Jurassic sediments in the SE comprise non-marine sandstones and conglomerates to nearshore, brackish to marine sands, silts, clays and carbonates, grouped lithostratigraphically into the Lathi, Jaisalmer, Baisakhi, and Bhadasar formations. The Late Bajocian to Oxfordian Jaisalmer Formation is divided, in ascending order, into the Hamira, Joyan, Fort, Badabag, Kuldhar, and Jajiya members. Fossil records providing a Bajocian to Bathonian age for the lower and middle parts of the formation include: a Late Bajocian coral Isastraea bernardiana (d’Orbigny) in the uppermost Joyan Member; Bathonian ammonite Clydoniceras in the basal part of the Badabag Member; Bathonian foraminiferal/bivalve assemblages in the Fort Member. The topmost bed of the Joyan Member represents the peak of first marine transgression of the Jaisalmer Basin, probably contemporaneous with the Late Bajocian one in the neighbouring Kachchh Basin. Based on faunal studies Bajocian to Bathonian sediments of the Jaisalmer Basin can be broadly correlated with those of the Kachchh Basin. The Fort and Badabag members represent the following depositional environments, in chronological order: (a) brackish to shallow fully marine; (b) fully marine with rapidly fluctuating water energy and sedimentation rates; (c) near-shore to lower shoreface with fluctuating energy conditions, salinity and sedimentation rates; (d) near-shore to shoreface channels and storm-dominated marine above fair-weather wave-base; (e) lagoon with fluctuating low to moderate energy, salinity and sedimentation rates; (f) stormdominated shelf to lower shoreface.     

Depositional environments of Bathonian sediments from the Jaisalmer Basin, Rajasthan, western India

The pericratonic sedimentary Jaisalmer Basin, west of the Aravalli Ranges, on the westerly dipping eastern flank of the Indus Shelf, is a principal structural element of Rajasthan. Jurassic sediments in the SE comprise non-marine sandstones and conglomerates to nearshore, brackish to marine sands, silts, clays and carbonates, grouped lithostratigraphically into the Lathi, Jaisalmer, Baisakhi, and Bhadasar formations. The Late Bajocian to Oxfordian Jaisalmer Formation is divided, in ascending order, into the Hamira, Joyan, Fort, Badabag, Kuldhar, and Jajiya members. Fossil records providing a Bajocian to Bathonian age for the lower and middle parts of the formation include: a Late Bajocian coral Isastraea bernardiana (d’Orbigny) in the uppermost Joyan Member; Bathonian ammonite Clydoniceras in the basal part of the Badabag Member; Bathonian foraminiferal/bivalve assemblages in the Fort Member. The topmost bed of the Joyan Member represents the peak of first marine transgression of the Jaisalmer Basin, probably contemporaneous with the Late Bajocian one in the neighbouring Kachchh Basin. Based on faunal studies Bajocian to Bathonian sediments of the Jaisalmer Basin can be broadly correlated with those of the Kachchh Basin. The Fort and Badabag members represent the following depositional environments, in chronological order: (a) brackish to shallow fully marine; (b) fully marine with rapidly fluctuating water energy and sedimentation rates; (c) near-shore to lower shoreface with fluctuating energy conditions, salinity and sedimentation rates; (d) near-shore to shoreface channels and storm-dominated marine above fair-weather wave-base; (e) lagoon with fluctuating low to moderate energy, salinity and sedimentation rates; (f) stormdominated shelf to lower shoreface.     

四川盆地洛带气田蓬莱镇组储层沉积特征研究

四川盆地洛带气田蓬莱镇组浅层气藏为多层系的岩性圈闭气藏类型,气藏的分布及气井产能严格受储层沉积微相制约,建立沉积微相与储集性之间的关系对气田开发具有重要的指导意义.通过对储层的钻井岩心、录井及测井沉积微相特征分析,认为主要存在11种岩性相类型及其Ⅰ～Ⅲ类岩相序列组合.蓬莱镇组属于浅水三角洲沉积体系,主要由三角洲前缘亚相的水下分流河道、水下决口河道和决口扇、水下分流河道间、前缘河口砂坝、远砂坝、前缘席状砂及前三角洲7个沉积微相组成.水下分流河道和河口砂坝是气藏主要储层的沉积微相.     

川南下志留统石牛栏组沉积体系与岩相古地理

四川盆地南部下志留统石牛栏组为在缓坡陆棚基础上发育起来的碳酸盐台地的沉积,可划分出4个岩性段和2个沉积旋回.沉积体系在空间展布特征上表现为由南向北的从碎屑滨岸→局限台地→开阔台地→生物礁/滩→台地边缘斜坡→浅水陆棚浅滩→泥质浅水陆棚→深水陆棚变化,在垂向上则由泥/灰质深水→浅水陆棚→碳酸盐台地的变化;海平面变化是控制沉积体系发育和空间分布的重要因素.     

靖边-安塞地区延长组长1段沉积相特征

目的探讨鄂尔多斯盆地靖边—安塞地区三叠系延长组长1段的沉积相特征及展布。方法根据野外考察资料,利用地层对比及测井相分析方法,划分了靖边—安塞地区长1段沉积相类型。结果靖边—安塞地区晚三叠世末期为湖泊—三角洲沉积环境,沉积中心在子长地区;沉积相自下至上依次为三角洲平原、三角洲前缘和前三角洲—深湖;沉积序列自下至上以粒度由粗到细的正旋回为主。结论长1期湖盆的演化受鄂尔多斯盆地中部东西向构造带控制,该湖盆中的湖相暗色泥岩有可能成为子长等地区另一套重要的烃源岩。     

百口泉油田检188井区侏罗系八道湾组沉积相特征

 以沉积学和测井地质学理论为指导,对百口泉油田检188井区170余口井的测井和钻井资料以及部分露头资料进行了综合研究。用旋回对比、标志层对比和电测曲线相似性对比等地层划分对比原则将侏罗系八道湾组划分为12小层。对各小层进行了沉积相分析,认为八道湾组为一种潮湿-半干旱气候环境下的辫状河沉积,共发育主河道、支河道和泛滥平原3种亚相,发育水道、心滩、河漫滩和河漫沼泽4种微相。其中J₁b^8-5~J₁b⁷小层主要发育主河道和支河道,物源主要来自西北方向;J₁b⁶~J₁b³小层主要发育河道和河漫滩,物源来自正北和西北两个方向;J₁b²~J₁b¹小层以发育河漫沼泽为主,物源来自西北方向。沉积演化表明,八道湾组沉积时早期气候较干旱,晚期气候较潮湿,其沉积经历了一次较完整的水进-水退过程。     

甘谷驿油田延长组长6油层沉积特征

目的 了解长6储层的沉积特征，储层的分布规律。方法 在岩心观察的基础上，研究长6油层的岩性、结构、构造特征，结合测井相资料，研究沉积相。结果 长6油层沉积为湖泊三角洲前缘及三角洲平原沉积。结论 储集砂体为左角洲平原及前缘的分流河道沉积，储层分布受沉积特征控制。     

Evolution of an Eocene-Oligocene Saline Lake Depositional System and Its Controlling Factors,Jianghan Basin,China

The Upper Eocene–Lower Oligocene Qianjiang Formation of the Jianghan Basin in central China consists of a 4 700-m-thick lacustrine succession, containing 1 800 m of halite deposits. The maximum thickne...     

石羊河古终端湖泊沉积物粒度特征与沉积环境初探

利用石羊河古终端湖泊野麻湖剖面沉积物的粒度资料,分析了粒度组成、粒度参数、概率累积曲线等粒度特征,并探讨了古终端湖泊的沉积环境．结果表明石羊河古终端湖曾经是一个稳定的湖泊环境,大约在距今４０００多年前演变成为浅湖沼环境,现在已完全干涸．野麻湖剖面记录的数层快速风成沉积代表了周期性的沙尘暴事件．     

彰武地晚侏罗世九佛堂组沉积及聚煤特征

八道壕矿区位于彰武盆在西缘,含煤地层主要是上侏罗统九佛堂组,其充填特征为“五段式”,聚煤作用主要发育于湖后阶段,聚煤环境以扇三角洲前缘及其间的沼泽为主.整个彰武盆地具有广阔的找煤前景.     

二连盆地辫状河三角洲沉积特征及含油性

为了建立二连断陷湖盆辫状河三角洲沉积相模型 ,确定油气勘探领域 ,根据二连盆地吉尔嘎朗图等 30个凹陷的钻井岩性剖面、地震剖面、沉积构造、电性特征、测试结果和油气显示等资料 ,研究了断陷湖盆缓岸的大中型砂砾岩体的形成条件、储层微相特征和含油性 ,建立了相模式 .结果表明 :这类砂体属辫状河三角洲成因 ,发育辫状河三角洲平原等三个亚相、8个微相 ,存在以牵引流成因为主的沉积构造 .它的前缘水道和分支坝具有良好的储集性能和成油条件 ,是本区油气勘探的主要方向     

鄂尔多斯盆地定边地区延9、延10、长1标志层特征及其成因

利用岩芯、测井等资料,对鄂尔多斯盆地定边东仁沟地区延长组顶部及延安组底部进行初步的地层划分对比,划分的过程中对延安组延9、延10的煤层或炭质泥岩、侏罗系与三叠系之间的不整合面等不同类型的标志层进行识别,并对其电性特征进行阐述,研究其沉积成因,从而进一步指导研究区的地层精细划分工作。延10顶部的标志层与延9顶部分布不稳定的辅助标志层将两层分开,延10底部大段砂岩与长1顶部的不整合面将三叠系-侏罗系分开。在此基础上又将延9、延10分别分为上下两个小层。     

浅析乔家湾矿区山西和太原组煤层聚煤规律及其沉积环境的变化

分析了乔家湾矿区山西、太原组的岩层及古生物化石特征、煤岩性特征、煤层结构特征、煤质特征以及山西、太原组的煤层聚煤规律及沉积环境,指出1号、2号煤层为滨海—三角洲平原沉积,9号、10号、11号煤层为三角洲海湾及碳酸盐台地沉积,从中找出它们的变化规律性,对今后的矿井建设有指导意义。     

北羌塘盆地北部晚侏罗世索瓦组地层古生物新资料

在北羌塘盆地北部乌兰乌拉湖地区测制了多条晚侏罗世索瓦组剖面,讨论了该区索瓦组的岩性组合特征、沉积环境及空间变化规律.首次系统研究了索瓦组双壳类、层孔虫及珊瑚化石的组合特征及地理分布.建立了一个双壳类生物组合带,一个层孔虫组合和一个珊瑚组合.确定索瓦组的地质时代为晚侏罗世牛津期-基默里奇期.     

南极洲伊利莎白公主地区主要离子来源传输过程的沉积方式研究

通过对南极洲伊利莎白公主地区冰雪中几种主要离子资料的分析,结合前人的工作对本地区主要离子的来源、传输过程和沉积方式做了初步探讨。结果表明;南极洲伊利莎白公主地区冰盖中的海盐离子主要来源于周边亚南极地区的海洋,nssSO4^2-主要来源于中低纬度海洋生物的释放和火山喷发,而NO3^-主要来源于中低纬度地区的闪电和极地高空中的各种大气过程;海盐离子（主要Cl^-,Na^ ,Mg^2 ,ssSO4^2-）通过近距离低空传输到南极冰盖,而nssSO4^2-和NO3^-很可能是通过远距离高空传输到极冰雪中,具体过程为：nssSO4^2-和NO3^-在对流层顶部平流层底层呈带状输送到极地上空,然后辐射下沉,再辐射到其他地区;本地区大气中各主要离子浓度足够大,足以使本地区冰雪中主要离子浓度不随积累率的变化而变化,即离子浓度并不受积累率的影响。各主要离子、湿沉积所占比重的计算结果表明,本地区离子沉积方式以湿沉积为主。     

川东南上二叠统龙潭组泥页岩发育特征

为了探讨四川盆地东南部二叠统龙潭组泥页岩的资源潜力,在总结近年来四川盆地东南部龙潭组研究现状的基础上,根据野外露头、岩心和测井等资料,以层序地层与沉积相理论为基础,建立了层序界面识别标志和层序地层格架,研究了沉积相对岩性分布的影响,总结了龙潭组泥页岩岩性组合特征和泥页岩厚度特征。研究结果表明,四川盆地东南部龙潭组由底至顶依次划分为SQ1、SQ2、SQ3三级层序,SQ1层序由低位体系域、海侵体系域和高位体系域构成,而SQ2层序和SQ3层序则皆由海侵体系域和高位体系域构成;四川盆地东南部泥页岩组合及厚度受控于沉积环境:滨岸相主要泥页岩组合为泥包砂,厚度大;潮坪相主要泥页岩组合为泥包砂,有效厚度仅次于滨岸相;混积陆棚相泥页岩组合以泥包灰为主,较薄; SQ1段、SQ2段和SQ3段泥页岩厚度总体上表现为西南部厚、东北部薄的变化趋势。     

鄂尔多斯盆地吴起王洼子地区早侏罗世沉积微相及古地貌恢复

应用印模法恢复的王洼子地区前侏罗纪古地貌主要由古河道、斜坡脊和沟组成.前侏罗纪古地貌控制着早侏罗世的沉积,延10期为辫状河亚相河道砂坝、泛滥平原,延9期为三角洲平原亚相分支河道、漫滩沼泽.研究区总体受西北物源的控制,发育北西--南东向的河道砂体.分析了侏罗系沉积前古地貌与延10、延9的成藏关系,认为油藏主要分布于紧邻高地的斜坡等地势相对较高的地带.河道砂体的发育控制着油藏的形成和分布,勘探区大面积位于古地貌的斜坡位置,北部的古河道下切河谷为延长组油气向上运移的通道.研究区侏罗系油藏发育,下一步勘探重点为前侏罗纪斜坡脊与延9、延10河道砂体的叠合区.     

A new cheirolepidiaceous conifer from the Early Jurassic of the Junggar Basin, northern Xinjiang and its paleoclimatic implications

Mesozoic sediments are extensively developed in the vast area of Xinjiang and Jurassic strata are well exposed in the Junggar Basin. The Haojiagou geological section near Urumqi in the south of the basin is a typical section for the Lower Jurassic Badaowan and Sangonghe formations. The cheirolepidiaceous conifer Brachyphyllum (Hirmeriella?) sp., which exhibits strongly xeromorphic characters, was discovered in the Sangonghe Formation and is associated with a high relative abundance (up to 75%) of dispersed Classopollis pollen. The occurrence of cheirolepidiaceous foliage and Classopollis pollen in the Sangonghe Formation indicates that a warm and dry climate prevailed in the Junggar Basin during the Early Jurassic (Early Toarcian), supporting the hypothesis for a warming event at that time.     

A new cheirolepidiaceous conifer from the Early Jurassic of the Junggar Basin, northern Xinjiang and its paleoclimatic implications

Mesozoic sediments are extensively developed in the vast area of Xinjiang and Jurassic strata are well exposed in the Junggar Basin. The Haojiagou geological section near Urumqi in the south of the basin is a typical section for the Lower Jurassic Badaowan and Sangonghe formations. The cheirolepidiaceous conifer Brachyphyllum (Hirmeriella?) sp., which exhibits strongly xeromorphic characters, was discovered in the Sangonghe Formation and is associated with a high relative abundance (up to 75%) of dispersed Classopollis pollen. The occurrence of cheirolepidiaceous foliage and Classopollis pollen in the Sangonghe Formation indicates that a warm and dry climate prevailed in the Junggar Basin during the Early Jurassic (Early Toarcian), supporting the hypothesis for a warming event at that time.