北喜马拉雅地区下白垩统海底扇沉积环境   总被引：5，自引：2，他引：5       下载免费PDF全文

岳来群  史晓颖  王鸿祯 《古地理学报》2003,5(4):391-403

北喜马拉雅地区早白垩世沉积以碎屑岩为主，海底扇沉积十分发育。根据沉积岩的矿物成分、结构、构造和产状特征，可将这些海底扇分为6个亚相。根据亚相在空间的排列组合所指示的沉积环境，海底扇的发展过程可划分为萌芽、青春、成熟和消亡四个阶段。在早白垩世早、中期海底扇处于萌芽阶段和青春阶段，沉积岩的砂/?泥比值高，砂岩的矿物成分和结构多样，反映出海岸平原和大陆架较窄，海底坡度较大，从早白垩世开始沉积环境经历了由陆棚向大陆斜坡转移的过程，海平面升高，构造性质主要为水平拉张、裂陷。早白垩世晚期海底扇处于成熟阶段，海岸平原和大陆架宽度加大，砂/?泥比值降低，沉积物以泥质组分为主，富含菱铁矿、钙质结核，少见菊石等生物化石，相变缓慢，水体低能，属于缓倾斜、无明显坡折带的陆缘，反映了北喜马拉雅区的最大海侵事件。由于印度洋扩张、印度板块向北漂移，在早白垩世晚期北喜马拉雅被动陆缘已趋成熟，本区处于大陆斜坡下部强还原的深海-半深海环境。晚白垩世总体上属于海退，海底扇处于消亡阶段，其岩石由泥岩类向砂岩类直至砾岩类演化。白垩纪沉积盆地则相应经历了由陆棚→拉张断陷盆地→陆坡→深海盆地的演变。  相似文献   

An unconformity in the early Miocene syn-rifting succession, northern Noto Peninsula, Japan: Evidence for short-term uplifting precedent to the rapid opening of the Japan Sea     

Kazuhiko Kano  Toshiyuki Yoshikawa  Yukio Yanagisawa  Kenshiro Ogasawara  Tohru Danhara 《Island Arc》2002,11(3):170-184

Abstract   The present paper describes the newly discovered early Miocene unconformity in the northern Noto Peninsula, on the Japan Sea side, central Japan. The unconformity marks the boundary between an early Miocene non-marine to marine succession and a more extensive, late early to early middle Miocene marine succession, and contains a time gap of an order of 1 million years or less from 18 Ma or earlier to 17 Ma. The early Miocene succession likely represents an early phase of marine transgression and initial slow rifting. The overlying early to early middle Miocene succession records the climax of the opening of the Japan Sea at ca  16 Ma with widespread, rapid subsidence of the Japan Arc. The unconformity between the two transgressive successions may represent a global sealevel fall or, more likely, crustal uplifting because no upward-shallowing or regressive facies remains between the two successions. Early Miocene unconformities that are thought to be correlative with this unconformity in the northern Noto Peninsula occur in places along the Japan Sea coast of Sakhalin and Japan. They are likely to have been produced during rifting in response to upwelling of asthenospheric mantle, although more accurate age constraints are necessary to evaluate this idea.  相似文献   

济阳坳陷沙河街组锶硫同位素特征   总被引：2，自引：0，他引：2  

袁波  陈世悦  袁文芳  朱建伟 《吉林大学学报(地球科学版)》2008,38(4)

通过对研究区锶硫同位素特征分析,探讨济阳坳陷古近纪是否遭受过海侵作用.结果表明:沙四上亚段和沙三下亚段87Sr/86Sr值为0.707 6～0.709 9,属于同时期海相锶同位素范围;沙四上亚段δ34S为15‰～24‰,也属于同期海相硫同位素范围.结合前人研究成果,认为济阳坳陷沙四上亚段和沙三下亚段沉积时段曾不同程度受到海侵作用的影响.  相似文献   

华北盆地南部早二叠世早期聚煤作用的成因机制   总被引：5，自引：0，他引：5  

胡益成  廖玉枝 《地学前缘》1999,6(Z1):111-115

华北盆地南部早二叠世早期形成的海陆交替相含煤地层,含有多达30余层煤。这些为数众多的煤层在其形成过程中,受到海水进退和风暴潮2种动力作用的控制。频繁的海水进退,虽然多次为本区的聚煤场所提供了广阔的空间,但未能给滨海沼泽内泥炭物质的持续堆积带来足够的时间。频繁的风暴潮作用对策煤场所既有破坏性又有建设性：风暴上升流可以强烈地侵蚀滨海沼泽的泥炭层,风暴下降流又可将大量的泥炭物质携带到浅海环境再沉积;风暴上升流可以在平缓开阔的潮汐地带上建造成平行海岸线的沙脊,使沙脊靠陆一侧成为新的聚煤场所,下一次较大的风暴上升流又可荡平这些新建立起来的聚煤场所。因此本区的聚煤作用既复杂又特殊。  相似文献   

Distinction between the Storegga tsunami and the holocene marine transgression in coastal basin deposits of western Norway     

Stein Bondevik  John Inge Svendsen  Jan Mangerud 《第四纪科学杂志》1998,13(6):529-537

Many coastal lakes were inundated by both the Storegga tsunami (7000 ¹⁴C yr BP) and the mid-Holocene sea-level rise (the Tapes transgression) in western Norway. The tsunami eroded lake bottoms and deposited graded and/or massive beds of sand, rip-up clasts, and coarse plant material. By contrast, when the rising sea entered the lakes, it deposited only gyttja, silt and fine sand, without causing much erosion of the underlying lake sediments. Storegga tsunami deposits in some coastal lakes were interpreted previously as ordinary marine sediments from the Tapes transgression. Our reinterpretation of these deposits shows that the transgression maximum phase was reached after 6500 yr BP, more than 1000 yr later than previously inferred for the coast of Sunnmøre. The new data cannot be combined in a shoreline diagram without showing the 6000 yr BP and 7000 yr BP shorelines as slightly warped. © 1998 John Wiley & Sons, Ltd.  相似文献   

Initiation and early evolution of a forearc basin: Georgia Basin,Canada     

Bryan A. P. Kent  Shahin E. Dashtgard  Chuqiao Huang  James A. MacEachern  H. Dan Gibson  Gwyneth Cathyl-Huhn 《Basin Research》2020,32(1):163-185

The lower Nanaimo Group was deposited in the (forearc) Georgia Basin, Canada and records the basin's initiation and early depositional evolution. Nanaimo Group strata are subdivided into 11 lithostratigraphic units, which are identified based on lithology, paleontology, texture and position relative to both the basal nonconformity and to each other. Significant topography on the basal nonconformity, however, has resulted in assignment of lithostratigraphic units that are not time correlative, and hence, cannot reliably be used to accurately reconstruct basin evolution. Herein, we present a sequence stratigraphic framework for lower Nanaimo Group strata in the Comox Sub-Basin (northern Georgia Basin) that integrates both facies analysis and maximum depositional ages (MDAs) derived from detrital zircon. This stratigraphic framework is used to define significant sub-basin-wide surfaces that bound depositional units and record the evolution of the basin during its early stages of development. Seven distinct depositional phases are identified in the lower 700 m of the lower Nanaimo Group. Depositional phases are separated by marine flooding surfaces, regressive surfaces, or disconformities. The overall stratigraphy reflects net transgression manifested as an upwards transition from braided fluvial conglomerates to marine mudstones. Transgression was interrupted by periods of shoreline progradation, and both facies analysis and MDAs reveal a disconformity in the lowermost part of the Nanaimo Group in the Comox Sub-Basin. Stratigraphic reconstruction of the Comox Sub-Basin reveals two dominant depocenters (along depositional strike) for coarse clastics (sandstones and conglomerates) during early development of the Georgia Basin. The development and position of these depocenters is attributed to subduction/tectonism driving both subsidence in the north-northwest and uplift in the central Comox Sub-Basin. Our work confirms that in its earliest stages of development, the Georgia Basin evolved from an underfilled, ridged forearc basin that experienced slow and stepwise drowning to a shoal-water ridged forearc basin that experienced rapid subsidence. We also propose that the Georgia Basin is a reasonable analogue for ridged forearc basins globally, as many ridged forearcs record similar depositional histories during their early evolution.  相似文献   

全新世海侵以来山东荣成朝阳港泻湖沉积层与古环境记录     

周江  刘冬雁  庄振业  王祖正  刘利东 《中国海洋大学学报(自然科学版)》2008,38(5)

泻湖是全新世海侵以来发育的以淤积为主的海岸地貌,其沉积地层蕴含了丰富的古环境演变信息.对朝阳港泻湖SO4钻孔岩芯样品作粒度、软体动物、孢粉和14C等项目的测试分析,将该孔地层自下而上划分成陆相、滨浅海相、泻湖相、泻湖-沼泽相等四层和Ⅰ,Ⅱ,Ⅲ,Ⅳ个孢粉组合带.基于对地层和孢粉组合特点的深入剖析,结果表明朝阳港泻湖自全新世海侵以来经历了海湾、沙坝-泻湖和泻湖-沼泽等3个环境演化阶段,同时存在明显的沉积环境和气候变化事件,包括8～7 ka B.P.海陆相之间的不整合沉积间断事件、7～6 ka B.P.的气候暖湿事件和5～4 ka B.P.的明显降温事件.  相似文献   

陆表海盆地含煤地层的高分辨率层序地层研究   总被引：2，自引：1，他引：1  

李增学  单松炜 《煤田地质与勘探》2000,28(4):13-16

分析了鲁西南煤田陆表海盆地沉积充填序列中的T-R旋回特征;划分出陆表海盆地高分辨层序,依次为构造层序、超层序、层序、小层序组、小层序及更小级别的层序单元。在研究了陆表海盆地海平面变化特点及其对煤聚积控制作用的基础上,提出了“海侵事件成煤”观点,认为海侵事件是控制陆表海盆地煤聚积的重要事件,突发性海侵事件界面、暴露土壤化事件界面和海侵事件成因的煤层均具有等时性对比意义。   相似文献   

Geochemical record of the Holocene Jomon transgression and human activity in coastal lagoon sediments of the San'in district, SW Japan   总被引：1，自引：0，他引：1  

H. Ishiga  T. Nakamura  Y. Sampei  T. Tokuoka  K. Takayasu   《Global and Planetary Change》2000,25(3-4)

Coastal lagoon muds were analyzed to evaluate changes in sedimentary environments by the Jomon transgression from the lower to middle Holocene age and human activities. Core samples from Lake Shinji, Southwest Japan were utilized, which cover the entire Holocene Nakaumi Formation (ca. 23-m thick), and comprise the Lower, Middle, Upper and Uppermost members. Total sulfur (TS) contents and Fe₂O₃/Al₂O₃ ratios increase from the boundary of Middle and Upper members, which is 1 m below the Kikai-Akahoya (K-Ah) volcanic ash of 6300 years BP. This change coincides to the pollen flora zone boundary of the Pinus–Abies and the Cyclobalanopsis–Castanopsis, suggesting transition to a warming climate. Chemical index of alteration (CIA) values [(ratio of Al to Al+Ca+Na+K)×100] and Rb/K ratios also show gradual increase from the middle part of the Upper member, due to its derivation from highly weathered source material probably formed under warming and rainy condition. Al₂O₃/TiO₂ and SiO₂/TiO₂ show little variation from the Lower to the Upper members, probably related to consistent feldspar composition in the source rocks, and homogeneously mixed clays. In the Uppermost member (from 1500 years), sharp increases in Ti/Zr and decreases in both Nb/Y and Zr/Y occurred, suggesting heavy mineral fractionation. This change was caused by iron sand processing called Kannanagashi and charcoal-making in the most mountainous regions. Soil erosion by these processes brought changes in mud composition, shown by the enrichment in Al₂O₃, and depletion in Zr and Cr. Human activities thus had severe impacts on sedimentary environments compared with the natural changes since the Jomon transgression.  相似文献   

黔西南地区早-中三叠世沉积岩相与Ladinian-Carnian期大海侵   总被引：1，自引：0，他引：1  

李荣西  魏家庸  肖家飞  王兴理  D.J.Lehrmann 《地球科学与环境学报》2003,25(3):1-6

扬子地块主体在中三叠世晚期出现了一次大规模的海退(即著名的拉丁期大海退),但是位于扬子地块西南缘的黔西南地区在同期却出现了一次大规模的海侵,与之对应的沉积岩相也由以杨柳井组为代表的浅水碳酸盐岩沉积变为以竹竿坡组为代表的一套富含大量浮游生物和游泳生物的深水瘤状暗色灰泥岩和代表最大海泛面的瓦窑组黑色页岩和深海灰岩沉积。之后,扬子台地被一套深水陆源硅质碎屑浊积岩和一套巨厚的陆相含煤碎屑沉积岩覆盖,从此结束了其自晚元古代以来长达630Ma的碳酸盐岩台地生长演化历史。对比分析表明,黔西南地区这次大规模海侵与全球海平面变化同步,相当于全球海平面变化曲线的一级旋回UpperAbsaroka旋回(megacycle)的第三个二级超级旋回中的第一个三级旋回,具有全球对比性。  相似文献