西藏侏罗纪双壳类化石组合特征

该文详细论述了西藏侏罗纪双壳类化石组合特征、地理分布和共生生物的关系,并划分为喜马拉雅和冈底斯-念青唐古拉-三江两生物地理区。     

鄂尔多斯盆地延长组遗迹化石组合与古环境

通过对野外剖面、钻井岩芯中遗迹化石组合的分析发现,鄂尔多斯盆地晚三叠世延长期发育的湖泊地层中主要有垂直居住迹(Skolithos和Cylindricum)、垂直觅食迹(Scoyenia)、U形管迹(Arenicolites)、潜穴迹(Planolites、Chondrites和Teichichnus)、水平迹(Protopaleodictyon)、逃逸迹(Fugichnia)、游泳迹及根迹.结果表明:遗迹化石的分布和组合与鄂尔多斯盆地晚三叠世湖盆的沉积环境相匹配,这对于利用遗迹化石组合恢复湖盆岩相古地理具有重要的地质意义.     

内蒙古平庄盆地中新世早期植物群与古环境

内蒙古平庄盆地晚第三纪植物群以被子植物占优势,计有16属22种,其次为裸子植物,6属7种,没有发现蕨类植物。其中裸子植物以杉科为主,被子植物以壳斗科、杨柳科、桦木科和榆科为主,连香树科、木兰科也有一定属种。该植物群总体面貌与吉林敦化秋梨沟植物群、山东山旺植物群和铁匠沟老梁底组的植物组合基本相似,时代为中新世早期。分析植物群组成特征及沉积特征,平庄植物群反映的是温暖湿润的暖温带－亚热带气候条件。     

羌塘盆地塞仁地区古油藏地球化学特征及意义

【研究目的】羌塘盆地是青藏高原北部的大型海相含油气盆地,研究区塞仁地区位于南羌塘坳陷,该区油气地球化学研究成果较少、研究程度较低。【研究方法】本文对古油藏含油层样品的族组成、及甾萜烷等地球化学特征进行总结,并结合多种生标参数得出结论。【研究结果】该地区古油藏整体处于低成熟-成熟阶段,C27甾烷较C29甾烷占优势,并且三环萜烷类化合物以C23三环萜烷为主峰,也表明母质来源以海相有机质为主,并有一定的陆源有机质贡献。油藏样品具有较低的姥植比(Pr/Ph<1),非藿烷中检测出一定丰度的伽马蜡烷以及较高的C35/C34升藿烷值特征,这些参数指示古油藏形成于沉积水体较深、还原性相对较强并具有一定盐度的沉积环境。【结论】该地区古油藏地球化学特征分析为油气成藏研究与油气富集规律认识奠定基础,确定了该地区古油藏的沉积环境和母质来源。古油藏母质来源以海相为主,沉积环境为较还原环境。     

羌塘盆地昂达尔错古油藏油气来源及成藏模式

昂达尔错油砂带是羌塘盆地内规模最大的古油藏,明确其油气来源和成藏模式对指导该地区的油气资源勘探具有重要意义。以饱和烃色谱-质谱、单体烃碳同位素和流体包裹体分析为基础,对羌塘盆地昂达尔错古油藏油气来源、成藏期次及成藏模式进行了探讨。研究表明：昂达尔错古油藏油苗与下侏罗统曲色组烃源岩具有相似的生物标志化合物组合特征,体现出两者具有较强的亲缘性;昂达尔错古油藏油气充注期次可划分为晚侏罗世(151.6～158.7 Ma)、早白垩世(142.3～143.9 Ma)与中新世(12.5～16.6 Ma)三期,其中早白垩世为该古油藏的主充注期;古油藏油源为下侏罗统曲色组页岩,储集层为中侏罗统布曲组砂屑灰岩和白云岩,盖层为布曲组泥晶灰岩,构成正常的“下生上储”式成藏组合。     

羌塘盆地那底岗日组火山岩地层时代及构造背景

野外地质调查发现,在羌塘盆地中央隆起带及其两侧的南、北羌塘拗陷中,那底岗日组及其同沉积地层之下广泛发育了一套古风化壳,古风化壳覆盖了石炭系、二叠系以及前人已确定的三叠系肖茶卡组,具有区域性展布的特点.结合在那底岗日组底部识别出来的底砾岩,证实了那底岗日组与下伏地层之间存在沉积间断.那底岗日组的沉积标志着新一轮盆地演化的开启.取自北羌塘中部胜利河地区英安岩SHRIMP 锆石U-Pb年龄为(217.1±4.9) Ma,北羌塘西部冈玛错地区辉绿岩角闪石的40Ar/39Ar坪年龄为(197±4) Ma.结合近年来在羌塘盆地东部以及西部地区获得的那底岗日组火山岩喷发年龄,表明羌塘盆地那底岗日组火山岩的喷发年龄为205～220 Ma,这一年龄也代表了羌塘中生代盆地的开启年龄.那底岗日组火山岩具有高的Nb/Zr(0.039～0.058),Ta/Hf(0.095～0.15)和Zr/Y(3.57～6.01)比值,在构造环境判别图(如Zr-Zr/Y和Th/Hf -Ta/Hf)上,那底岗日组火山岩大多位于板内玄武岩区.结合中生代盆地早期沉积演化特征,认为羌塘中生代盆地形成于伸展的构造环境.     

安塞油田前侏罗纪古地貌特征及其与油气富集关系

目的深入探究鄂尔多斯盆地安塞油田前侏罗纪古地貌特征,为侏罗系油田开发奠定基础。方法通过野外露头及岩心的详细观察和描述,结合大量测井曲线和测试分析资料,采用印模法对古地貌进行刻画。结果古河谷和河谷平原为研究区前侏罗纪主要的地貌单元,其中河谷平原可进一步分为谷坡及河漫台地;在古河谷和古坡之间形成了许多坡咀。结论古地貌控制着侏罗纪早期沉积相及砂体的发育和分布;古河谷的北缘及次级古河谷的谷坡是侏罗系油藏分布的主要位置;今后在勘探中应该重视次级古河谷谷坡的研究,开展老井复查,以期发现新的油气增长点。     

羌塘盆地达卓玛剖面古-始新世古生物群特征

详细研究了首次发现于羌塘盆地岗尼乡达卓玛剖面下第三系的介形虫、轮藻和保存完好的昆虫化石,建立了3个化石组合。根据这些组合面貌及其分布的主要层位,认为含有丰富生物化石的这套地层的时代应为古-早始新世。     

银根—额济纳旗盆地白垩纪地层、古生物群和古环境研究

利用盆地周缘露头、盆内钻井资料系统总结了银根—额济纳旗盆地白垩纪的地层、古生物特征,探讨了白垩纪的古环境.白垩系划分为下统巴音戈壁组、苏红图组及银根组,上统乌兰苏海组.地层特征盆地各区差异明显,巴音戈壁组北、东部以含烃源岩,西南部以不含烃源岩为特征;苏红图组西部以不含火山岩系和含煤层,东部以含火山岩系为特征.白垩系地层中发育介形类、双壳类、叶肢介、轮藻、藻类、腹足类、鱼类、昆虫、古植物和孢粉等多门类古生物化石.白垩纪可分为早白垩世的暖温带—亚热带干湿交替过渡性气候和晚白垩世的亚热带—热带半干旱—干旱气候.     

与大荔人头骨化石共生的双壳类化石及其环境意义

记述了与大荔人头骨化石共生的双壳类化石3属12种。通过与现生的相近双壳类生活环境的对比，得出大荔地区当时的气候环境主要受夏季风控制的暖湿气候的结论。结合对沉积特征的分析，引出了对该地区地貌演化模式的讨论。     

Middle-Late Jurassic marine dinoflagellate cysts from the eastern Qiangtang Basin in the Qinghai-Tibet Plateau, China

Dinoflagellate cysts from two Middle-Late Jurassic sections in the Wenquan and Yanshiping regions of the Qiangtang Basin comprise 24 genera and 36 species including one new taxon of the genus Tenua. Based on their stratigraphic distribution, six assemblage zones are recognized in ascending order as follows: 1) Tubotuberella egemenii Zone, probably Callovian, in the mid-upper part of the Xiali Formation; 2) Pareodinia ceratophora Zone, probably Oxfordian, in the lower part of the Suowa Formation; 3) Batiacasphaera floralis Zone, probably Oxfordian, in the middle part of the Suowa Formation; 4) Amphorula metaelliptica Zone, probably Early Kimmeridgian, in the upper part of the Suowa Formation; 5) Alisocysta spp. Zone, probably Early Kimmeridgian, in the base of the Xueshan Formation; 6) Tenua wenquanensis sp. nov. -Dichadogonyaulax schizoblata Zone, probably Late Kimmeridgian-Tithonian, in the lower part of the Xueshan Formation. Based on our analysis the Jurassic-Cretaceous Boundary in the Wenquan section is placed higher than previously.     

Middle-Late Jurassic marine dinoflagellate cysts from the eastern Qiangtang Basin in the Qinghai-Tibet Plateau, China

Dinoflagellate cysts from two Middle-Late Jurassic sections in the Wenquan and Yanshiping regions of the Qiangtang Basin comprise 24 genera and 36 species including one new taxon of the genus Tenua. Based on their stratigraphic distribution, six assemblage zones are recognized in ascending order as follows: 1) Tubotuberella egemenii Zone, probably Callovian, in the mid-upper part of the Xiali Formation; 2) Pareodinia ceratophora Zone, probably Oxfordian, in the lower part of the Suowa Formation; 3) Batiacasphaera floralis Zone, probably Oxfordian, in the middle part of the Suowa Formation; 4) Amphorula metaelliptica Zone, probably Early Kimmeridgian, in the upper part of the Suowa Formation; 5) Alisocysta spp. Zone, probably Early Kimmeridgian, in the base of the Xueshan Formation; 6) Tenua wenquanensis sp. nov. -Dichadogonyaulax schizoblata Zone, probably Late Kimmeridgian-Tithonian, in the lower part of the Xueshan Formation. Based on our analysis the Jurassic-Cretaceous Boundary in the Wenquan section is placed higher than previously.     

The calcareous nannofossil record and its geological significance in the Jurassic black shales from the Qiangtang Basin, northern Tibetan Plateau

A new record of calcareous nannofossils in Jurassic black shales from the Qiangtang Basin, northern Tibet comprises two series, representing shelf to basin settings. By microscopic observation, the first discovery of the family Watznaueriaceae has been made: Watznaueria fossacincta is distinguished from Watznaueria britannica. From the biostratigraphy and chemostratigraphy, the sediments are characterized by paucity of assemblages, prevalence of coccospheres, and a relatively high organic content. There are two classes of preservation: poorly and moderately preserved assemblages. Total nannofossil abundance and species diversity show lower values within calcareous beds, compared to the argillaceous. Assemblage composition appears quite different in the marls and argillaceous rocks compared with the limestones. Fossil abundance and preservation are partly determined by diagenesis, selective dissolution and sedimentary environment. Dysaerobic or anoxic bottom-water conditions are indicated by coccospheres, with nannofossils the main source of hydrocarbons. The black shale facies with high organic carbon contents can be attributed to coccolithophorid high productivity and blooms, indicating that the Qiangtang black shales have a great oil-generation potential.     

The calcareous nannofossil record and its geological significance in the Jurassic black shales from the Qiangtang Basin, northern Tibetan Plateau

A new record of calcareous nannofossils in Jurassic black shales from the Qiangtang Basin, northern Tibet comprises two series, representing shelf to basin settings. By microscopic observation, the first discovery of the family Watznaueriaceae has been made: Watznaueria fossacincta is distinguished from Watznaueria britannica. From the biostratigraphy and chemostratigraphy, the sediments are characterized by paucity of assemblages, prevalence of coccospheres, and a relatively high organic content. There are two classes of preservation: poorly and moderately preserved assemblages. Total nannofossil abundance and species diversity show lower values within calcareous beds, compared to the argillaceous. Assemblage composition appears quite different in the marls and argillaceous rocks compared with the limestones. Fossil abundance and preservation are partly determined by diagenesis, selective dissolution and sedimentary environment. Dysaerobic or anoxic bottom-water conditions are indicated by coccospheres, with nannofossils the main source of hydrocarbons. The black shale facies with high organic carbon contents can be attributed to coccolithophorid high productivity and blooms, indicating that the Qiangtang black shales have a great oil-generation potential.     

羌塘盆地中晚侏罗世旋回地层初步分析

羌塘盆地是中国海相侏罗系最为发育的地区之一,对该套地层开展了旋回地层学研究,初步的研究结果表明羌塘盆地中上侏罗统至少存在四种旋回类型,即沉积旋回、古生物旋回、地球化学旋回和磁化率旋回,并按级别将低频旋回划分为3个旋回级次.其中一级旋回是由顶底不整合面限制的一个总体向上变粗变浅的充填序列,持续时间为48 Ma;二级旋回显示为大型的海进-海退旋回,旋回的时间跨度为27～29 Ma;三级旋回显示为向上变粗或向上变细的不完整旋回,旋回的时间跨度为7～14 Ma.古生物旋回、地球化学旋回(碳氧稳定同位素、微量元素)和磁化率旋回与沉积旋回具有良好的响应,并与特提斯同期低频旋回具有很好的对比性.     

西藏八宿侏罗纪花岗岩的岩石学特征及找矿意义

探讨西藏八宿地区侏罗纪花岗岩的岩石学特征,为找矿提供理论依据.通过对花岗岩类岩体的地质、地球化学、成分演化程度、分异程度和氧化状态的分析,结果表明区内侏罗纪花岗岩大量分布,反映了一次大规模岩浆事件.花岗岩由北西—南东向的断裂控制.岩石组合为黑云角闪石英二长闪长岩-黑云母花岗闪长岩-花岗闪长斑岩-黑云母二长花岗岩,为过铝...     

西藏羌塘盆地东部侏罗系生油条件与油气显示

羌塘盆地目前已经发现有190多处油气显示,这些油气显示主要集中在侏罗系和三叠系中,且主要形成自生自储式的生储盖组合,在盆地东部侏罗系中又新发现多处石膏盐丘沥青为主的油气显示。研究区内侏罗系生油岩生油条件研究表明,多套生油层能提供较充足的油气源;多期构造运动控制了油气的成藏保存条件,分析认为羌塘盆地东部侏罗系和三叠系复向斜带中受断裂影响小的低背斜带有望为进一步油气勘探提供有利区块。     

羌塘晚三叠世-早白垩世裂陷盆地基底构造

探讨羌塘盆地基底构造,为油气远景评价提供依据.通过对十多年来积累的地质、地球物理资料和物性资料的研究,在羌塘盆地识别出2个基底界面,一是前寒武系结晶基底顶面的密度(重力异常)界面,二是上三叠统顶部的磁性(航磁异常)界面.根据最新的航磁异常资料,对晓三叠世-早白垩世被动大陆边缘裂陷-拗陷盆地的基底构造单元进行分析,划分出2个Ⅰ级构造单元,4个Ⅱ级构造单元,23个Ⅲ级构造单元.在此基础上识别出3个裂陷槽、2个隆起带,圈定出3个相对应的生烃凹陷,2个发育礁、滩相碳酸盐岩储集层的隆起带,圈定了3个油气运移集聚的远景区.     

柴达木盆地北缘下、中侏罗统古地理及盆地类型研究

柴达木盆地北缘侏罗系后期改造强烈,地层赋存复杂,从地面露头、钻井、地震等资料入手,采用单因素分析多因素综合作图法,对下、中侏罗统岩相古地理进行了定量研究.认为早中、侏罗世时期该区主要发育湖泊相,以滨浅湖-半深湖相为主;现今下、中侏罗统的分布范围并不代表其原始沉积盆地的边界,原始沉积盆地的北边界在南祁连山边界大断裂附近;北缘早、中侏罗世时期为伸展断陷盆地.     

西藏阿翁错盆地古近系牛堡组烃源岩地球化学特征

在西藏阿翁错盆地古近系牛堡组实测剖面的基础上,对烃源岩有机质丰度、有机质类型、有机质成熟度等方面进行研究,结果表明牛堡组烃源岩有机质丰度中等偏低,泥页岩和泥晶灰岩有机碳平均质量分数分别为0.26%和O.15%,泥页岩表现出较差烃源岩特征,泥晶灰岩则表现为中等烃源岩特征.泥页岩有机质类型以Ⅱ1型和Ⅱ2型为主,泥晶灰岩有机...