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1.
南海西部表层沉积物钙质浮游生物分布与碳酸盐溶解 总被引：1，自引：0，他引：1
对南海西部300多个表层沉积样品中的浮游有孔虫和钙质超微化石定量分析表明，几乎所有样品均含浮游有孔虫、钙质超微化石，但丰度相差十分悬殊，浮游有孔虫丰度介于0．5～36673个／g之间，钙质超微化石丰度为0～1725个／10个视域，两者的分布规律相似。在陆坡区钙质浮游生物最富集，尤其在西沙群岛西南、南沙西部礁滩附近海区丰度最高；向深海盆区和陆架浅水区，钙质浮游生物丰度均下降。但从两者的丰度分布来看，其溶解程度不同，浮游有孔虫更容易溶解，在200～2000m水深区，丰度最高，2000m以下丰度锐减；而钙质超微化石的最富集区在500～3000m，且3000m以下仍较丰富。从碳酸盐的分布来看，本区碳酸盐的临界补偿深度(CCrD)为3500m，而CCD大于4300m，碳酸盐的溶解主要由有孔虫和钙质超微化石构成。 相似文献
2.
对南海34个站位表层沉积中的钙质超微化石进行了氧碳稳定同位素分析.结果表明,钙质超微化石δ^18O化范围为-2.656‰～0.006‰,平均为-1.517‰;δ13C值变化范围为-1.510‰～0.778‰,平均为0.140‰.通过与有孔虫同位素分析结果相比较,发现钙质超微化石δ^18O高于浮游有孔虫而低于底栖有孔虫,δ13C值低于浮游有孔虫而高于底栖有孔虫.从平面分布来看,南海表层沉积钙质超微化石氧同位素在东北和西南各存在一个小于-1.5‰的低值区,碳同位素在东北存在一个小于0的低值区.钙质超微化石与有孔虫同位素值的差异性可能与其生命效应及生活环境有关.而钙质超微化石与有孔虫同位素平面分布规律上的不同也揭示了海水温度、盐度、营养水平等海洋参数可能对超微化石和有孔虫同位素的分馏起不同控制作用. 相似文献
3.
通过对南海东北部(12°～22°N,116°～122°E)表层沉积中的浮游有孔虫、底栖有孔虫、钙质超微化石、硅质与钙质生物丰度和比值的定量分析以及碳酸盐含量的测定,发现碳酸盐含量、浮游有孔虫、钙质超微化石丰度以及钙质生物比值随水深的增大迅速减小,而底栖有孔虫占有孔虫全群的比值和硅质生物比值以及底栖有孔虫胶结质壳类的百分含量却随水深的增大迅速增加.研究表明,调查区内微体化石丰度和比值以及碳酸钙含量的高低,与碳酸盐溶跃面(lysocline)和碳酸盐补偿深度密切相关,碳酸盐溶跃面和碳酸盐补偿深度南、北还存在一定差异,碳酸盐溶跃面南部较北部深,南部在2 600 m上下,北部则在2 200 m上下;碳酸盐补偿深度也是南部的较深,南部为3 600 m上下,而北部在3 400 m上下. 相似文献
4.
通过对南海东北部(12°～22°N,116°～122°E)表层沉积中的浮游有孔虫、底栖有孔虫、钙质超微化石、硅质与钙质生物丰度和比值的定量分析以及碳酸盐含量的测定,发现碳酸盐含量、浮游有孔虫、钙质超微化石丰度以及钙质生物比值随水深的增大迅速减小,而底栖有孔虫占有孔虫全群的比值和硅质生物比值以及底栖有孔虫胶结质壳类的百分含量却随水深的增大迅速增加.研究表明,调查区内微体化石丰度和比值以及碳酸钙含量的高低,与碳酸盐溶跃面(lysocline)和碳酸盐补偿深度密切相关,碳酸盐溶跃面和碳酸盐补偿深度南、北还存在一定差异,碳酸盐溶跃面南部较北部深,南部在2600m上下,北部则在2200m上下;碳酸盐补偿深度也是南部的较深,南部为3 600 m上下,而北部在3 400 m上下。 相似文献
5.
本文采用国际大洋发现计划(IODP)第368航次U1501站位井深264.0～331.1 m的样品,通过有孔虫壳体氧同位素地层和锶同位素定年,得出该段井深年龄为晚渐新世?早中新世20.3～32.0 Ma(地震反射不整合面T60的底部年龄在28～30.5 Ma左右)。T60构造运动之后,岩芯沉积物中有机碳含量、底栖有孔虫壳体稳定碳同位素δ13C、浮游与底栖有孔虫碳同位素差值Δδ13CP-B指示海水表层生产力的降低;碳酸钙含量、有机碳/氮比值反映了陆源物质输入的减少;结合浮游有孔虫相对丰度以及底栖有孔虫的属种组合变化,共同揭示了南海北部在晚渐新世?早中新世时期,区域构造沉降运动导致了U1501站位在T60之后古水深逐步加深、离岸距离变远,相关结论从微体古生物学角度为认识T60构造事件及其沉积环境变化提供了科学证据。 相似文献
6.
西太平洋晚第三纪钙质超微化石及其古海洋学意义 总被引：2，自引：0，他引：2
本文研究了菲律宾海东部,北部“大洋钻探工程”125航次782A和786A二个钻孔晚第三纪的钙质超微化石。本区自下而上划分为13个带(或亚带),存在三个沉积间断:晚渐新世与中中新世之间;中中新世与晚中新世之间以及晚中新世与早上新世之间。据超微化石分析,本区晚第三纪存在4个相对暖水期和4个相对较凉期。根据菲律宾海东部,中部“深海钻探工程”58、59、60三个航次以及我国东海陆架、台湾东海岸及西部地区,南海北缘等地钙质超微化石分带的对比,晚渐新世与早中新世之间以及中、上新世之间的沉积间断在环西太平洋一侧具有普遍性,但形成原因不尽相同。 相似文献
7.
应用浮游有孔虫定量统计、底栖有孔虫氧同位素和磁性地层学等资料来确定南海ODP1148站深海沉积中的上新统／更新统(P／P)界线。氧同位素期(MIS)64和65之间的P／P界线在1148站位于井深112．75m处，计算年龄为1．805Ma，在地层对比上与Vrica层型剖面的P／P界线一致。浮游有孔虫Pulleniatina obliquiloculata在MIS62出现以右旋壳为主的转变，计算年龄为1．76Ma，此事件和Olduvai极性亚时顶界看来是最接近P／P界线的可靠时间面。除此以外，在1148站P／P界线及其附近没有发现重大的地层学和环境变化事件。相比之下，1148站底栖δ^18O值在3．05～2．53Ma期间快速变重，冬季表层海水温度下降了5℃，指示了北半球冰盖的形成。 相似文献
8.
南海北部ODP1148站中新世以来的碳酸盐含量变化及其古环境意义 总被引：13，自引：0，他引：13
对南海北部 ODP 114 8站采自孔深 4 6 5 m以上的 170 0个沉积物样品 ,测定了 Ca CO3含量、Ca CO3堆积速率、非钙质堆积速率、浮游有孔虫丰度、粗组分百分含量 (>6 3μm)、浮游有孔虫破壳率和底栖有孔虫在有孔虫全群中的百分含量。碳酸盐百分含量和碳酸盐堆积速率自 2 4 Ma以来的变化呈现逐步下降的趋势 ,但在 2 4 .0～ 15 .8、14 .2～ 11.6、10 .6～ 4 .8和 3.4～ 0 Ma四个时期具有高碳酸盐生产力 ,其中 10 .6～ 4 .8Ma的高生产力与印度洋和太平洋中新世晚期和上新世早期的“生物勃发”相对应。非钙质和碳酸盐两者堆积速率变化趋势在总体上相似 ,反映了陆源物质输入对碳酸盐生产力的影响。 3.4 Ma后非钙质堆积速率的大幅度增长主要与青藏高原和台湾岛的隆起有关 ,它们也是上新世晚期和第四纪 Ca CO3百分含量显著下降的主要原因。 2 4 Ma以来南海北部碳酸盐的保存逐渐变弱 ,而碳酸盐溶解作用逐渐增强 ,在 15 .8～ 14 .2、11.6～ 10 .6和 4 .8～ 3.4 Ma存在 3个显著的碳酸盐溶解事件 ,其中 11.6～ 10 .6 Ma的溶解事件与赤道太平洋和加勒比海的中—晚中新世“碳酸盐崩溃”事件相当 ,说明该事件具更广泛的全球影响 相似文献
9.
自Alvarez等(1980)提出白垩纪-第三纪(K-T)分界期出现一次火流星撞击事件之后,发生大规模生物灭绝的这个时期便引起人们的关注.撞击的影响是:浮游有孔虫和钙质超微浮游生物大规模灭绝、全球Ir异常、形成契克苏卢博撞击坑、撞击坑附近出现可疑碎屑沉积. 相似文献
10.
南海北部盛冰期以来古海洋环境变化的沉积记录 总被引：4，自引：0，他引：4
利用气候替代指标U37k-SST,浮游有孔虫Globigerinoides ruber的δ18O,δ13C,微体古生物种群变化、陆源和生源组分以及沉积物粒径等,对南海北部69孔沉积物进行综合研究.结果表明U37k-SST在冰后期为23.3～26.9℃,在末次盛冰期时为22.2～23.8℃.用浮游有孔虫转换函数法对季节温差进行估算,在冰后期为4.5～7.0℃,在末次冰期为7.0～9.0℃,两种估温法均反映了古气候变化相应的海水表层温度.69柱沉积物地层记录在末次盛冰期浮游有孔虫温带优势种Neogloboguadrina pachyderma和营养种Neogloboguadrina dutertrei丰度一致增加;热带优势种Pulleniatina obliqueloculata和Globigerinoide sacculifer以及超微化石丰度则相应减少,而冰后期则相反.浮游有孔虫、钙质超微化石组成和数量的改变也为古海洋温度升、降提供了直接的证据.研究还表明南海北部冰后期以河流搬运为主,末次盛冰期时以风力搬运占优势,这反映了冬季风强化. 相似文献
11.
珠江口盆地BY7—1—1井晚渐新世浮游有孔虫的发现及其地质意义 总被引：6，自引：2，他引：6
秦国权 《海洋地质与第四纪地质》1992,12(2):21-32
本文系统介绍了珠江口盆地最南的一个探井——BY7—1—1井浮游有孔虫生物地层和海侵层序。通过对该井有孔虫全面系统采样分析,发现了渐新世浮游有孔虫组合。这一重大发现给重新认识该区上、下第三系界线,以及对整个南海北部地层对比提供了新资料。并对有关的一些地质问题进行了讨论。 相似文献
12.
中太平洋海山铁锰结壳生物地层学研究 总被引：2，自引：0，他引：2
用生物地层学方法对位于中太平洋同一座海山上的2块铁锰结壳样品进行了生物地层学详细研究,发现2块样品的生长层位对应,生物组合也相同.经鉴定,2块结壳的主要生长期都是晚古新世、中始新世至晚始新世、中中新世至上新世、上新世至更新世,2个主要的结壳生长间断分别在渐新世和早始新世. 相似文献
13.
本文对“海洋四号”船于ＤＹ８５－３航次在东太平洋海盆ＣＣ区南部取得的ＰＣ５７９４和ＰＣ５６５３二个柱状沉积样的钙质超微化石作了详细的分析研究，进行了生物化石带的划分与对比。其中，ＰＣ５７９４自下而上划分出ＮＮ１，ＮＮ２和Ｎ３二个化石带；ＰＣ５６５３仅识别出ＮＮ２化石带。 相似文献
14.
Using recently gathered onland structural and 2D/3D offshore seismic data in south and central Palawan (Philippines), this paper presents a new perspective in unraveling the Cenozoic tectonic history of the southeastern margin of the South China Sea. South and central Palawan are dominated by Mesozoic ophiolites (Palawan Ophiolite), distinct from the primarily continental composition of the north. These ophiolites are emplaced over syn-rift Eocene turbidites (Panas Formation) along thrust structures best preserved in the ophiolite–turbidite contact as well as within the ophiolites. Thrusting is sealed by Early Miocene (∼20 Ma) sediments of the Pagasa Formation (Isugod Formation onland), constraining the younger limit of ophiolite emplacement at end Late Oligocene (∼23 Ma). The onset of ophiolite emplacement at end Eocene is constrained by thrust-related metamorphism of the Eocene turbidites, and post-emplacement underthrusting of Late Oligocene – Early Miocene Nido Limestone. This carbonate underthrusting at end Early Miocene (∼16 Ma) is marked by the deformation of a seismic unit corresponding to the earliest members of the Early – Middle Miocene Pagasa Formation. Within this formation, a tectonic wedge was built within Middle Miocene (from ∼16 Ma to ∼12 Ma), forming a thrust-fold belt called the Pagasa Wedge. Wedge deformation is truncated by the regionally-observed Middle Miocene Unconformity (MMU ∼12 Ma). A localized, post-kinematic extension affects thrust-fold structures, the MMU, and Late Miocene to Early Pliocene carbonates (e.g. Tabon Limestone). This structural set-up suggests a continuous convergent regime affecting the southeastern margin of the South China Sea between end Eocene to end Middle Miocene. The ensuing structures including juxtaposed carbonates, turbidites and shallow marine clastics within thrust-fold belts have become ideal environments for hydrocarbon generation and accumulation. Best developed in the Northwest Borneo Trough area, the intensity of thrust-fold deformation decreases towards the northeast into offshore southwest Palawan. 相似文献
15.
A 33 Ma lithostratigraphic record of tectonic and paleoceanographic evolution of the South China Sea
Qianyu Li Pinxian Wang Quanhong Zhao Lei Shao Guangfa Zhong Jun Tian Xinrong Cheng Zhimin Jian Xin Su 《Marine Geology》2006,230(3-4):217-235
The 853 m thick sediment sequence recovered at ODP Site 1148 provides an unprecedented record of tectonic and paleoceanographic evolution in the South China Sea over the past 33 Ma. Litho-, bio-, and chemo-stratigraphic studies helped identify six periods of changes marking the major steps of the South China Sea geohistory. Rapid deposition with sedimentation rates of 60 m/Ma or more characterized the early Oligocene rifting. Several unconformities from the slumped unit between 457 and 495 mcd together erased about 3 Ma late Oligocene record, providing solid evidence of tectonic transition from rifting/slow spreading to rapid spreading in the South China Sea. Slow sedimentation of 20–30 m/Ma signifies stable seafloor spreading in the early Miocene. Dissolution may have affected the completeness of Miocene–Pleistocene succession with short-term hiatuses beyond current biostratigraphical resolution. Five major dissolution events, D-1 to D-5, characterize the stepwise development of deep water masses in close association to post-Oligocene South China Sea basin transformation. The concurrence of local and global dissolution events in the Miocene and Pliocene suggests climatic forcing as the main mechanism causing deep water circulation changes concomitantly in world oceans and in marginal seas. A return of high sedimentation rate of 60 m/Ma to the late Pliocene and Pleistocene South China Sea was caused by intensified down-slope transport due to frequent sea level fluctuations and exposure of a large shelf area during sea level low-stands. The six paleoceanographic stages, respectively corresponding to rifting (33–28.5 Ma), changing spreading southward (28.5–23 Ma), stable spreading to end of spreading (23–15 Ma), post-spreading balance (15–9 Ma), further modification and monsoon influence (9–5 Ma), and glacial prevalence (5–0 Ma), had transformed the South China Sea from a series of deep grabens to a rapidly expanding open gulf and finally to a semi-enclosed marginal sea in the past 33 Ma. 相似文献
16.
Taiwan Island's outcropping strata can provide important insights into the sedimentary environment and source development of the southeast China margin. This research is based on the Eocene–Miocene strata of the Tsukeng area in the central Western Foothills, northeast shoreline of Taiwan Island and two sites of the East China Sea Shelf Basin(ECSSB), using petrology and detrital zircon U-Pb age for the analysis. Results show that central and northeast Taiwan Island experienced a transformation from continental to marine facies during the Eocene–Miocene, and the sandstone maturity changed with time. Source analysis shows that sediments from the Eocene–early Oligocene strata mainly originated from near-source Mesozoic rocks, whose zircon age is consistent with the igneous rock in the surrounding area and coastal Cathaysia, showing 120 Ma and 230 Ma peaks in the age spectrum diagram. Since the late Oligocene, peaks of 900 Ma and 1 800 Ma are seen, indicating that deposition of matter from the old block began. The sediments could be a mixture of the surrounding Mesozoic volcanic and fewer pre-Cambrian rocks sourced from the coastal river and sporadic old basement in the ECSSB instead of longdistance transportation. 相似文献
17.
Geochemical and detrital zircon U-Pb dating data for drilled sediments from the Baiyun deepwater area of the northern South China Sea demonstrate a change of sedimentary sources from the Oligocene to the Miocene.Zircon ages of the pre-rift Eocene sequences are dominated by Yanshanian ages with various peak values(110–115 Ma for U1435 and L21; 150 Ma for H1), indicating local sediment supply from the pre-existing Mesozoic magmatic belt. For the Oligocene sediments in the northern part of the basin, the rare earth elements show different distribution characteristics, indicating sediment supply from the paleo-Zhujiang River(Pearl River), as also confirmed by the multimodal zircon age spectra of the Lower Oligocene strata in Well X28. By contrast, a positive Eu anomaly characterizes sediments from the western and southern parts of the basin, indicating potential provenances from intermediate to basic volcanic rock materials. The Baiyun Movement at the end of the Oligocene contributed to a large-scale subsidence in the deepwater area and also a northward retreat of continental shelf break, leading to deepening depositional environment in the basin. As a result, all the detrital zircon ages of the Upper Oligocene strata from Wells X28, L13, and L21 share a similar distribution, implying the possible control of a common source like the Zhujiang River. During the Miocene, whereas sediments in the northern area were mainly sourced from the Zhujiang River Delta, and those in the southern deepwater area continued to be affected by basic volcanic activities, the Dongsha Uplift could have contributed as the main source to the eastern area. 相似文献
18.
Mid-Miocene (Langhian; ∼15.4 Ma) sapropels formed within the easternmost Mediterranean basin, now uplifted in northern Cyprus. These sapropels represent the oldest known sapropels in a predominantly marl succession. Six well-developed sapropels were studied. Strontium isotope dating of twelve samples gave a preferred age of ∼15.4 Ma (Langhian); i.e. during the final phases of the Middle Miocene Climatic Optimum (MCO). The age of the best-preserved nannofossil assemblage (Langhian) is close to the strontium ages. The Langhian strontium ages are preferred over an alternative early Serravallian age for less well-preserved nannofossil assemblages. Total organic carbon contents in the sapropels reach maximum values of 3.9 wt.%. Relative to the host marls, the sapropels show enrichments in terrigenous-derived minerals and related major and trace elements. Sedimentological evidence indicates that the terrigenous sediments were eroded from the northern borderlands of the deep-water basin under warm, humid conditions. High fresh-water run-off from surrounding landmasses is likely to have promoted a low-salinity lid to the eastern Mediterranean deep-water basin. This, in turn, would have restricted deep-water ventilation and promoted widespread anoxia. Exceptionally high concentrations of chalcophile elements (e.g. Cu, Ni and Zn) are consistent with anoxic conditions. Abundant nutrient-rich fresh-water input is also likely to have stimulated siliceous productivity (although any siliceous microfossils did not survive diagenesis). A significant role for diagenesis in sapropel formation is indicated by the mobilisation of Ba from sapropels to marl directly beneath. Orbitally induced dry–wet oscillation, the mechanism invoked to explain the Pliocene to Holocene sapropels, apparently was already in place during the latest stages of the MCO when the Langhian sapropels accumulated. These sapropels accumulated immediately after the Middle Miocene closure of the Southern Neotethys when the Eastern Mediterranean Sea apparently became more sensitive to orbital cyclicity. The development of a semi-enclosed deep-water basin was, therefore, a prerequisite for sapropel formation. 相似文献