西藏南部晚白垩世-古新世大洋红层的分布与时代

特提斯—喜马拉雅北沉积亚带沉积有一套大洋红色岩层,由东往西在羊卓雍错、江孜、萨迦、萨嘎、札达一带断续出露,并与宗卓组上部地层相关。这套海相红层,根据岩性特征和浮游有孔虫可以直接进行区域对比。其时代在江孜地区为Santonian晚期—Campanian中期,包括Dicarinella asymetrica, Globotruncanitaelevata,Globotruncana ventricosa 和Globotruncanita calcarata 浮游有孔虫带;在萨迦地区限于Campanian期,鉴定有Globotruncanita elevata, Globotruncana ventricosa 和G. linneiana等具时代意义的浮游有孔虫;在萨嘎—吉隆地区为Maastrichtian期,识别出Gansserina gansseri 和Abthomphalus mayaroensis 浮游有孔虫带;在札达地区为古新世早期,以Glibigerina eugubina G. fringa化石带为代表。海相红层在西藏南部由东往西其时代逐渐变新,主要沉积时代分布在Santonian晚期—古新世早期。其总体时间跨度较大,大约长达20Ma。而事件在各个地点的延续时间有限,基本在3~8 Ma之内。根据对海相红层和沉积基质中浮游有孔虫的研究,该沉积带宗卓组的顶界时代已超出白垩纪,进入了古新世。     

阿尔卑斯-喀尔巴阡上白垩统大洋红层特征与对比

在前人研究的基础上,从时代、岩性、古生物、沉积速率、沉积环境等方面对阿尔卑斯—喀尔巴阡地区的上白垩统大洋红层进行了详细对比,发现研究区内上白垩统大洋红层最早出露于Cenomanian期,最晚可延续至古近纪,且在Campanian期出露最为广泛,其岩性以灰岩、泥灰岩和含泥灰岩为主,生物化石以浮游有孔虫为主,沉积速率较低且在各地不尽相似,在CCD面上、下均可以出现,沉积环境一般是大陆边缘盆地、斜坡和大洋盆地等远洋、半远洋环境。通过比较分析,为进一步深入研究上白垩统大洋红层提供较为全面的基础资料。     

东特提斯喜马拉雅下白垩统碎屑锆石U-Pb年代学及其古地理

东特提斯喜马拉雅在中生代位于东冈瓦纳大陆的结合部位,其古地理对于了解东冈瓦纳大陆裂解至关重要.对东特提斯喜马拉雅塔嘎地区沉积地层进行了详细的碎屑锆石U-Pb年代学研究.结果表明,东特提斯喜马拉雅塔嘎地区采样剖面沉积下限为126.6±2.7 Ma.碎屑锆石年龄谱显示东特提斯喜马拉雅塔嘎地区采样地层主要包含~520 Ma、~890 Ma和~1 200 Ma的特征峰值年龄,对比结果表明东特提斯喜马拉雅塔嘎地区沉积地层碎屑锆石年龄谱与印度东部和澳大利亚西南部地层碎屑锆石年龄谱具有一定的相似性.结合东冈瓦纳岩浆活动记录以及该剖面下部玄武岩年龄,东特提斯喜马拉雅塔嘎地区地层沉积于东特提斯喜马拉雅从东冈瓦纳大陆分离时期,其物质来源可能为印度东部、澳大利亚西南部以及南极大陆.      

雅鲁藏布江缝合带南缘混杂岩放射虫组合及其地质意义

在西藏南部雅鲁藏布江缝合带南侧的吉隆地区出露有一套混杂岩,该混杂岩中见大量的放射虫化石。其研究成果可为恢复缝合带南缘混杂岩地层层序、探讨特提斯古海洋盆地演化、揭示印度-亚洲板块的全面碰撞过程等提供重要的生物地层学证据。将吉隆地区桑单林剖面自下而上划分为宗卓组、桑单林组和者雅组3个岩石地层单元;并在其中发现有晚白垩世-始新世放射虫化石,鉴定出50属、72种,划分了4个放射虫化石带：Immersothorax cyclops带(晚白垩世Campanian期),Spongurus irregularis带(早古新世,RP1-RP3),Buryella dumitricai带(古新世中晚期,RP4-RP6),Phormocyrtis turgida带(始新世早期,RP7-RP8)。通过对古近纪时期特提斯喜马拉雅北亚带的地层、沉积等特征进行横向上的对比分析,认为古新世时处于特提斯喜马拉雅沉积带北亚带西段的吉隆地区为前渊环境,东段的江孜地区则为滨浅海沉积环境,表明西藏境内特提斯洋的闭合并不是同时发生的,而是沿雅鲁藏布江缝合带自东向西发生。     

昌宁-孟连结合带弄巴地区泥盆系、石炭系的时代及沉积环境:放射虫、碎屑锆石U-Pb年龄和Hf同位素约束

造山带中远洋深水沉积物是恢复古大洋的重要依据之一,昌宁-孟连古特提斯结合带存在大量海相沉积物,但是否存在大洋盆地相的远洋沉积还不清楚.对弄巴地区被认为最可能是洋盆相沉积的石炭系岩片和海相泥盆系岩片进行了岩石学、放射虫时代、碎屑锆石U-Pb年龄和Hf同位素研究.石炭系岩片放射虫硅质岩中鉴定出放射虫6属8种,时代为早石炭世早-中期.LA-ICP-MS锆石U-Pb定年结果显示,泥盆系岩片岩屑石英杂砂岩碎屑锆石年龄范围为387~3 266 Ma,最年轻一组年龄为387~413 Ma;石炭系岩片中与放射虫硅质岩共生的基性凝灰岩碎屑锆石年龄为341~3 403 Ma,最年轻一组年龄为341~354 Ma.综合锆石年龄和化石资料,限定泥盆系岩片原始沉积时代为早-中泥盆世,石炭系岩片时代为早石炭世早-中期.碎屑锆石U-Pb年龄谱特征和Hf同位素组成指示泥盆系岩片和石炭系岩片具有相似的物质源区,主要来源于亲冈瓦纳的陆壳,少量来自于古生代特提斯域新生岛弧.早-中泥盆世地层岩片原始沉积于亲冈瓦纳的大陆斜坡环境;早石炭世地层岩片原始沉积于亲冈瓦纳的大陆斜坡至古特提斯洋盆边缘环境,不是远洋深水的大洋盆地环境.寻找以远洋深水沉积物为代表的大洋盆地相沉积并开展研究是当前昌宁-孟连古特提斯研究的重要方向之一.      

青海柴达木盆地北缘寒武纪和奥陶纪海相红层的分布与时代

参照青海省柴达木盆地北缘寒武纪和奥陶纪地层相关文献资料,通过野外地质调查和系统样品分析结果,在柴北缘寒武纪—奥陶纪地层中梳理和识别出了19层海相红层。其中,寒武纪地层中识别出了12层海相红层,奥陶纪地层中识别出了7层海相红层。除奥陶纪石灰沟组海相红层(QORB3,QORB4,QORB5及QORB6)为深水大洋红层外,其余15层海相红层均属浅水—半深水陆棚红层。依据海相红层及其上下层位所含化石,本文初步论述了各海相红层的大致时代,并与我国主要块体的同期海相红层进行对比。上述研究对进一步开展全国乃至全球寒武纪、奥陶纪海相红层分布及对比提供了基础数据和资料。此外,通过国内同期红层的对比,本文还讨论了河北唐山寒武纪海相红层的分布及中国南方中奥陶世大坪期—达瑞威尔期早期海相红层广布事件。     

西秦岭北缘漳县中-新生代红层地层格架厘定及其地质意义

西秦岭北缘潭县地区分布的中—新生代红层地层格架和时代一直存在争议。该地区红层地层格架的正确厘定对于重建西秦岭北缘中—新生代构造地貌演化过程和认识印度-欧亚板块汇聚碰撞过程在青藏高原东北缘的远程地质响应具有重要的科学意义。通过对红层地层与下伏老地层以及不同红层地层之间的角度不整合、红层沉积序列及岩石学特征和红层地层与西秦岭北缘断层之间关系的研究,结合孢粉分析资料,重新厘定了西秦岭北缘漳县地区的红层沉积地层地质格架。研究表明,西秦岭漳县地区分布的中—新生代红层地层自下而上可分为三套地层系统,即①下白垩统紫红色砂岩、砾岩。②中新统红色砾岩、砂岩、黏土岩和深紫色-灰色泥岩、灰色泥灰岩、蒸发岩系。③上新统河流相砾岩层(韩家沟砾岩)和F1断层以北的红色洪积砾岩层。三套红层地层之间都为角度不整合面分割,相对地质关系清晰,沉积岩石特征差异明显,尽管由于断层的破坏,但没有影响到整体地层格架。三套红层地层系统反映了西秦岭北缘中—新生代不同阶段的沉积构造环境和古地貌演化过程,为研究西秦岭中—新生代陆内构造过程和青藏高原隆升、构造变形向东北缘的扩展远程效应等科学问题提供了基本的地质约束。     

羌塘-三江古生代-中生代沉积盆地演化

羌塘-三江构造-地层大区的古生代-中生代沉积盆地和构造演化受特提斯洋的控制.通过综合分析前人对羌塘-三江地区大量岩石地层、生物地层、同位素年代学及构造学等研究资料,对羌塘-三江构造-地层大区各分区古生代-中生代的沉积盆地类型进行了划分,并分析了各个沉积盆地的形成和演化过程,探讨了该区的大地构造演化:早古生代该区主体属于大洋环境;晚古生代随着特提斯洋向南东、北东方向的俯冲,该区开始发育一系列活动陆缘沉积盆地,产生金沙江弧后洋、澜沧江弧后洋和甘孜-理塘弧后洋,形成多岛洋弧盆系;中生代,随着特提斯洋向北东的俯冲消减,弧后洋逐渐闭合,羌塘-三江地区发生大规模弧-弧、弧-陆碰撞增生,逐渐转化成陆.随着白垩纪特提斯洋的闭合,印度板块与中国西部碰撞、造山,羌塘-三江地区发育陆内盆地.      

从地震信息看中国东部和中国中西部沉积盆地构造演化动力学与断块油气藏(下) 中国中西部盆地演化及断块(圈闭)油气藏

中国中西部地区以塔里木盆地及其演化为典型代表。震旦纪以来,经历了地台发育、持续沉降、拉张翘倾、挤压坳陷及断陷推覆等构造发育阶段,与中国东部一样,表现为拉张与挤压交互出现的手风琴式演化史,突出的差别在于晚喜马拉雅期在西部地区形成强烈的挤压逆掩推覆构造,而东部地区只形成坳陷式的沉积盆地。中亚—蒙古大洋、秦—祁—昆大洋、古特提斯洋、中特提斯洋、印度洋以及印度板块等在不同地质时期的板块活动是中国中西部地区盆地演化发展的动力学因素。根据地震剖面解释成果,可确定出四种断块油气藏类型,均反映后期挤压逆冲特征,尤其是燕山期—喜马拉雅期推覆前锋带断块油气藏,还可区分为拆离型、褶皱型、前冲型和反冲型等四种,且每一种还可再区分出若干种。     

昌宁-孟连结合带中三叠世含放射虫硅质岩地层的古特提斯意义

昌宁-孟连结合带中三叠世地层记录了古特提斯洋晚期演化信息,为正确认识古特提斯构造古地理格局提供了重要的解剖窗口.云南省沧源县团结地区原划泥盆系曼信组岩性为硅质岩与泥岩互层夹砂岩层（透镜体）,对其中长石砂岩和硅质岩分别开展锆石U-Pb测年和地球化学分析,在限定该地层时代的基础上探讨其古特提斯演化意义.长石砂岩夹层和透镜体碎屑锆石定年显示其时代分别不早于237.8±1.3 Ma和237.7±1.4 Ma,赋存地层区域上可与牡音河组对比.本次中三叠世放射虫硅质岩地层的发现,填补了本区残余盆地沉积记录.该地层中硅质岩的地球化学特征反映其形成于大陆边缘环境,结合其中陆源碎屑岩碎屑组分和副矿物特征,表明古特提斯残余洋盆规模有限.研究区三岔河组磨拉石沉积角度不整合于早期地层之上标志着残余洋盆最终闭合.      

Biostratigraphy and Sequence Stratigraphy of the Gurpi Formation at Deh Dasht Area,Zagros Basin,SW Iran

Abstract: A rich assemblage of planktonic foraminifera has been studied from an outcrop of the Gurpi Formation, the hydrocarbon source rock in the southwest Iran, Deh Dasht area (Kuh-e Siah anticline). Based on the distribution of the planktonic foraminifera, eight biozones have been recognized that included: Dicarinella concavata Interval Zone (Earliest Santonian), Dicarinella asymetrica Total Range Zone (Santonian to Earliest Campanian), Globotruncanita elevata Partial Range Zone (Early Campanian), Globotruncana ventricosa Interval Zone (Middle to Late Campanian), Radotruncana calcarata Total Range Zone (Late Campanian), Globotruncanella havanensis Partial Range Zone (Late Campanian), Globotruncana aegyptiaca Interval Zone (Late to latest Campanian), Gansserina gansseri Interval Zone (Latest Campanian to Early Maastrichtian). These biozones indicates that the Gurpi Formation deposited during the Early Santonian- Early Maastrichtian. These biozones are compared to the most standard biozones defined in Tethysian domain. Based on distribution of morphotype groups of planktonic foraminifera, planktonic to benthic ratio (P/B) and content of carbonate, nine third-order sequences are recognized.     

白垩纪大洋红层：特征、分布与成因

“白垩纪大洋红层”（CORB）自20世纪末正式提出后已经迅速成为白垩纪新的研究方向之一。本文在参考国外CORB的学术研究成果基础上,重点对我们在西藏南部和意大利中部两个研究程度较高地区所获得的立典研究成果予以详细介绍,同时对CORB的全球性对比进行总结和归纳,对大洋红层蕴涵的古海洋、古气候信息进行详细评述。我们认为,CORB是沉积物在原地氧化条件下的产物,导致该氧化条件出现的主要因素是底层水高含量的溶解氧,而深层古洋流的发育很可能是导致高溶解氧含量的主要原因。     

Litho- and biostratigraphy,facies patterns and depositional sequences of the Cenomanian-Turonian deposits in the Ksour Mountains (Saharan Atlas,Algeria)

The Cenomanian-Turonian deposits exposed in the Ksour Mountains, western part of the Saharan Atlas (Algeria), document marine shelf environments that had been thriving on the North African passive margin, connected northwards to the Tethys Ocean, and fringed southwards by the Saharan craton. Their lithological, palaeontological, and sedimentological characteristics have been investigated to provide new insights into the biostratigraphy, palaeo-environmental evolution and sea-level changes in this western part of the Saharan Atlas. Three formations are recognized, from base to top of the studied succession: 1. The El Rhelida Formation comprising two informal units: the mixed siliciclastic-carbonate unit deposited under different flow regime conditions, from shoreline to backshore environments, and the limestone–claystone unit including coastal mudflat deposits prone to storm events. The early Cenomanian age of the El Rhelida Formation is supported by vertebrate assemblages. 2. The Mdaouer Formation comprising two units: the evaporitic unit dominated by claystone and evaporite alternations deposited on a flat coastal sabkha with occasional storms, and the marlstone–limestone unit formed in a peritidal-lagoonal environment. The Mdaouer Formation is of early-middle Cenomanian age. 3. The Rhoundjaïa Formation comprising three units: the lower limestone unit consisting of relatively homogeneous fossiliferous limestones; the middle marly unit composed of marlstone and bioclastic limestones, and the upper limestone unit consisting of carbonates showing vertical variations in faunal content and stratonomy. The Rhoundjaïa Formation was deposited in homoclinal ramp setting. Ammonite data indicate an early late Cenomanian to early Turonian age for this interval. Within an overall transgressive trend, the Cenomanian-Turonian deposits of the Ksour Mountains record three third-order depositional sequences bounded each by regional discontinuities.     

塔里木盆地西北缘乌恰地区晚白垩世-渐新世微相分析及沉积演化

塔里木盆地西部是我国发育中新生代海相地层的少数地区之一。以沉积微相分析为手段,通过对塔里木盆地西北缘乌恰地区库孜贡苏剖面晚白垩世-古近纪岩性、生物组合、颗粒成分、基质类型及其沉积结构和构造特征等仔细研究,重点针对碳酸盐岩划分出（含）骨屑隐晶灰岩、隐晶灰岩、微（隐）晶白云岩、鸟眼隐晶灰岩、微晶鲕粒白云岩、生物碎屑灰岩、微晶球粒白云岩、生物灰岩、亮晶鲕粒灰岩等9个岩相类型。根据碳酸盐岩微相类型组合和剖面结构沉积特征,划分出潮上带、潮间带、潮下带、台地边缘浅滩和生物礁5个沉积相,并恢复了该区晚白垩世-古近纪的沉积环境演化过程,为查清白垩纪-古近纪特提斯洋演化以及重建该地区古环境和油气勘探研究提供重要的基础材料。     

Planktic Foraminiferal Biostratigraphy of the Cretaceous Oceanic Red Beds in Kangmar,Southern Tibet,China

The planktic foraminifera of the Chuangde Formation (Upper Cretaceous Oceanic Red Beds, CORBs) as exposed at Tianbadong section, Kangmar, southern Tibet has been firstly studied for a detailed for a detailed biostratigraphy elaboration. A rich and well-preserved planktic foraminifera were recovered from the Chuangde Formation of the Tianbadong section and the Globotruncanita elevata, Globotruncana ventricosa, Radotruncana calcarata, Globotruncanella havanensis, Globotruncana aegyptiaca, Gansserina gansseri and Abathomphalus mayaroensis zones have been recognized. The planktic foraminiferal assemblage points to an early Campanian to Maastrichitian age for the CORBs of the eastern North Tethyan Himalayan sub-belt, which also provides a better understanding of the shifting progress of the Indian Plate to the north and the evolution of the Neotethyan ocean. The lithostratigraphy of the Chuangde Formation of the Tianbadong section comprises two lithological sequences observed in ascending succession: a lower unit (the Shale Member) mainly composed of purple (cherry-red, violet-red) shales with interbedded siltstones and siliceous rocks; and an upper unit (the Limestone Member) of variegated limestones. The strata of the Chuangde Formation in the Tianbadong section are similar to CORBs in other parts of the northern Tethyan Himalaya area of Asia (Gyangze, Sa’gya, Sangdanlin, northern Zanskar, etc.). The fossil contents of the Chuangde Formation in the sections (CORBs) studied provide a means of correlation with the zonation schemes for those of the northern Tethyan Himalayan sub-belt and the Upper Cretaceous of the southern Tethyan Himalayan sub-belt. Paleogeographic reconstruction for the Late Cretaceous indicates that the Upper Cretaceous Chuangde Formation (CORBs) and correlatable strata in northern Zanskar were representative of slope to basinal deposits, which were situated in the northern Tethyan Belt. Correlatable Cretaceous strata in Spiti and Gamba situated in the southern Tethyan Belt in contrast were deposited in shelf environments along the Tethyan Himalayan passive margin. CORBs are most likely formed by the oxidation of Fe(II)-enriched, anoxic deep ocean water near the chemocline that separated the oxic oceanic surface from the anoxic.     

Fault-controlled stratigraphy of the Late Cretaceous Abiod Formation at Ain Medheker (Northeast Tunisia)

The palaeogeographic setting of the studied Ain Medheker section represents an Early Campanian to Early Maastrichtian moderately deep carbonate shelf to distal ramp position with high rates of hemipelagic carbonate production, periodically triggered by mass-flow processes. Syndepositional extensional tectonic processes are confirmed to the Early Campanian. Planktonic foraminifera identified in thin sections and calcareous nannofossils allow the identification of the following biozones: Globotruncanita elevata, Contusotruncana plummerae (replacing former Globotruncana ventricosa Zone), Radotruncana calcarata, Globotruncana falsostuarti, and Gansserina gansseri. The following stable C-isotope events were identified: the Santonian/Campanian boundary Event, the Mid-Campanian Event, and the Late Campanian Event. Together with further four minor isotopic events, they allow for correlation between the western and eastern realms of Tunisia. Frequently occurring turbidites were studied in detail and discussed in comparison with contourites.     

Implications of pre-mesozoic orogeny in the geological evolution of the Himalaya and Indo-Gangetic Plains

An integrated geological analysis of the Himalaya and Indo-Gangetic Plains demonstrates that the Great Vindhyan Basin incorporating large parts of these morphotectonic units were uplifted into an uneven landmass due to the Pre-Mesozoic orogenic cycle. This uneven landmass was eroded off largely during a considerable part of the Devonian and Carboniferous thereby causing partial absence of sedimentary sequences of these periods except in parts of the Tethys Himalaya. The Late Paleozoic epeirogenic movements brought about renewed sedimentation in the Lesser and Tethys Himalayas in the Krol and Tethys Basins, respectively, which was terminated by the Himalayan Orogeny during Late Cretaceous—Early Eocene.     

钛钡铬石,钛钾铬石的穆斯堡尔谱研究及晶体化学

本文在结构测定的基础上。应用穆斯堡尔谱技术。确定了钛钡铬石和钛钾铬石中铁离子的价态及结晶学位置。测试结果表明钛钾铬石中Fe的相对含量Fe~(2+)>Fe~(3+),而钛钡铬石中Fe~(2+)相似文献   

The Southeast France basin during Late Cretaceous times: The spatiotemporal link between Pyrenean collision and Alpine subduction

We present and discuss the Late Cretaceous evolution of the Southeast France Basin (SEFB) owing to the Pyrenean and Alpine belts. The available geological data (isopachs maps, boreholes and field data) were integrated in 3D GeoModeller software to build a 3D model of the geometry of the Cenomanian to Campanian sedimentary series of the Late Cretaceous period. Maps, 3D block diagrams and cross-sections extracted from the 3D model reveal a significant eastward marine regression during the Late Cretaceous with an average velocity of 0.5 to 1 cm per year. According to the location of the Late Cretaceous depocenters, two sub-basins are recognized in the SEFB and correspond to “en-échelon” synclines filled by syn-buckling sediments. These events are related to the sub-meridian “Pyrenean-Provence” crustal shortening. During Campanian time, the deepening and the tilting of the SEFB are interpreted as a consequence of the subduction of the Alpine Tethys. The Late Cretaceous SEFB is the prolongation on the European foreland of the Alpine subduction trench.     

Radiolarians,foraminifers, and biostratigraphy of the Coniacian–Campanian deposits of the Alan-Kyr Section,Crimean Mountains

Data on the distribution of radiolarians and planktonic and benthic foraminifers are obtained for the first time from the Alan-Kyr Section (Coniacian–Campanian), in the central regions of the Crimean Mountains. Radiolarian biostrata, previously established from Ak-Kaya Mountain (central regions of the Crimean Mountains) were traced: Alievium praegallowayi–Crucella plana (upper Coniacian–lower Santonian), Alievium gallowayi–Crucella espartoensis (upper Santonian without the topmost part), and Dictyocephalus (Dictyocryphalus) (?) legumen–Spongosaturninus parvulus (upper part of the upper Santonian). Radiolarians from the Santonian–Campanian boundary beds of the Crimean Mountains are studied for the first time, and Prunobrachium sp. ex gr. crassum–Diacanthocapsa acanthica Beds (uppermost Santonian–lower Campanian) are recognized. Bolivinoides strigillatus Beds (upper Santonian) and Stensioeina pommerana–Anomalinoides (?) insignis Beds (upper part of the upper Santonian–lower part of the lower Campanian) are recognized. Eouvigerina aspera denticulocarinata Beds (middle and upper parts of the lower Campanian) and Angulogavelinella gracilis Beds (upper part of the upper Campanian are recognized on the basis of benthic foraminifers. These beds correspond to the synchronous biostrata of the East European Platform and Mangyshlak. Marginotruncana coronata-Concavatotruncana concavata Beds (Coniacian–upper Santonian), Globotruncanita elevata Beds (terminal Santonian), and Globotruncana arca Beds (lower Campanian) are recognized on the basis of planktonic foraminifers. Radiolarian and planktonic and benthic foraminiferal data agree with one another. The position of the Santonian–Campanian boundary in the Alan-Kyr Section, which is located stratigraphically above the levels of the latest occurrence of Concavatotruncana concavata and representatives of the genus Marginotruncana, is refined, i.e., at the level of the first appearance of Globotruncana arca. A gap in the Middle Campanian–lower part of the upper Campanian is established on the basis of planktonic and benthic foraminifers. The Santonian–Campanian beds of the Alan-Kyr Section, on the basis of planktonic foraminifers and radiolarians, positively correlate with synchronous beds of the Crimean-Caucasian region, and beyond. Benthic foraminifers suggest a connection with the basins of the East European Platform.