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1.
赤道西太平洋末次盛冰期以来的浮游有孔虫氧碳稳定同位素记录 总被引：6，自引：0，他引：6
对西太平洋暖池核心区MD01—2386柱状样最上部5m进行了高分辨率的浮游有孔虫Globigerinoides ruber和Pulleniatina obliquiloculata的氧、碳稳定同位素分析,结合AMS^14C测年,研究表明其属于末次盛冰期-全新世的沉积。赤道西太平洋海区末次盛冰期以来δ^18O值显著降低,但有几次回返事件。表层浮游有孔虫G．ruber比次表层温跃层属种P．obliquiloculata对于环境变化的响应要快,但后者变化的幅度较大。这两个种的氧、碳同位素差值反映出温跃层深度自末次盛冰期以来逐渐加深,并存在周期性的回返事件,说明西太平洋暖池晚第四纪冰期旋回存在气候不稳定性。 相似文献
2.
石炭纪时期有孔虫具有演化快、分布广、数量丰富、分异度高的特点,对于地层的划分对比具有极为重要的意义。与全球其他重要的石炭纪沉积区相比,华南有孔虫生物地层划分精度相对较低。本文首次较为系统地报道了华南石炭系代表性岩石地层单位旧司组和上司组下部丰富的有孔虫化石及其在剖面上的分布情况,并综合现有关于华南的有孔虫化石资料,将华南维宪阶划分为7个有孔虫化石带,自下而上分别为Eoparastaffella simplex带、Viseidiscus/Planoarchaediscus带、Paraarchaediscus带、Pojarkovella nibelis带、Koskinotextularia带、Bradyina带和Janischewskina带。这些有孔虫带可与全球其他典型的石炭纪沉积区进行很好的对比,从而为相关的研究提供一个较为精细的地层格架。通过对黔南上司地区有孔虫的研究,提议中国石炭系区域性年代地层单位上司阶底界可用有孔虫Bradyina的首现定义,并将上司阶与西欧的Warnantian亚阶中上部和俄罗斯的Aleksinian亚阶—Venevian亚阶对比,对应国际维宪阶上部,为全球石炭系年代地层对比提供了可靠的化石依据。 相似文献
3.
The biostratigraphy and sedimentological evolution of the Tournaisian–Viséan (T–V) transitional strata in South China (Guangxi) have been investigated. The sediments were deposited on a carbonate platform and in slope and basinal environments. In the T–V transitional strata, six foraminiferal associations have been distinguished which allow correlation between the shallow and deep water deposits. A careful examination of the evolutionary stages of the foraminifer Eoparastaffella provides a more accurate criterion for the definition of the T–V boundary, but does not significantly modify the historical one. The distinction of two morphotypes is based on the elevation of the last whorl and the peripheral outline. Tournaisian specimens of Eoparastaffella have a well rounded periphery (morphotype 1) contrasting with the subangular periphery of younger Viséan specimens (morphotype 2). A coefficient can be deduced from simple biometric measurements for more precisely defining the T–V boundary. The sequence stratigraphy of the T–V strata in South China has been reconstructed by combining biostratigraphical and sedimentological data. It allowed the correlation of the T–V transitional strata between the platform area and the slope and basinal locations. Late Tournaisian strata were deposited during a highstand systems tract. Near the end of the Tournaisian, a major drop in relative sea-level led to the development of an unconformity in the platform area. Lowstand deposits formed during latest Tournaisian time in the basin where a detailed biostratigraphic framework has been devised. Sediments deposited during the ensuing transgressive systems tract overlie the late Tournaisian highstand sediments in the platform area and the latest Tournaisian lowstand deposits in the basin. A major drop in relative sea-level near the end of the Tournaisian has been recognized worldwide. Therefore, the possibility of using the sequence stratigraphy of the T–V strata in South China for worldwide correlations should be investigated. © 1997 John Wiley & Sons, Ltd. 相似文献
4.
对比分析了太平洋(Site 806)、大西洋(Site 664)和加勒比海地区(Site 999)末次冰期最盛期和全新世钻孔顶部不同尺寸大小的浮游有孔虫Globigerinoides sacculifer(500～600μm和300～355μm)和Globi-gerinoides ruber(300～355μm和250～300μm)的硼同位素组分变化,发现个体相对较小的有孔虫样品由于受到样品量以及样品前处理过程的影响,其硼同位素在末次冰期最盛期出现异常,浮游有孔虫硼同位素分析,尤其是冰期-间冰期时间尺度上的硼同位素分析,适合用个体相对较大的有孔虫。末次冰期最盛期太平洋和加勒比海地区溶解作用可能加强,其G.sacculifer的硼同位素偏低,但G.ruber的硼同位素不受溶解作用的影响,能够反映末次冰期海水pH值的变化。三个钻孔末次冰期最盛期G.ruber的硼同位素比全新世的硼同位素平均高(1.3±1.2)‰(2s.e.),与理论预测值1.6‰一致。 相似文献
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6.
Daisuke Sugawara Koji Minoura Naoki Nemoto Shinji Tsukawaki Kazuhisa Goto Fumihiko Imamura 《Island Arc》2009,18(3):513-525
Micropaleontological analysis of nearshore to offshore sediments recovered from the southwestern coast of Thailand was performed to clarify the submarine processes of sediment transport and deposition during the 2004 Indian Ocean tsunami. The distribution pattern of benthic foraminifers showed seaward migration after the tsunami event. Agglutinated foraminifers, which are characteristic of an intertidal brackish environment, were identified in the post-tsunami samples from foreshore to offshore zones. These suggest that sediments originally distributed in foreshore to nearshore zones were transported offshore due to the tsunami backwash. On the other hand, the distribution pattern of planktonic and benthic species living in offshore zones showed slight evidence of landward migration by the tsunami. This suggests that landward redistribution of sediments by the tsunami run-up did not occur in the offshore seafloor of the study area. Our results and a review of previous studies provide an interpretation of submarine sedimentation by tsunamis. It is possible that tsunami backwashes induce sediment flows that transport a large amount of coastal materials seaward. Thus, traces of paleotsunami backwashes can be identified in offshore sedimentary environments as the accumulation of allochthonous materials. This can be recognized as changes in benthic foraminiferal assemblages. 相似文献
7.
Xiang Rong Li Tiegang Yang Zuosheng Yan Jun Cao Qiyuan College of Marine Geosciences Ocean University of China 《海洋学报(英文版)》2003,(1)
Benthic foraminiferal analysis of 29 samples in surface sediments from the southern Okinawa Trough is carried out. The results indicate that benthic foraminiferal abundance decreases rapidly with increasing water depth. Percentage frequencies of agglutinated foraminifera further confirm the modern shallow carbonate lysocline in the southern Okinawa Trough. From continental shelf edge to the bottom of Okinawa Trough, benthic foraminiferal fauna in the surface sediments can be divided into 5 assemblages: (1) Continental shelf break assemblage, dominated by Cibicides pseudoungerianus, corresponds to subsurface water mass of the Kuroshio Current; (2) upper continental slope assemblage, dominated by Cassidulina carinata , Globocassidulina subglobosa, corresponds to intermediate water mass of the Kuroshio Current; (3) intermediate continental slope assemblage, dominated by Uvigerina hispi-da, corresponds to the Okinawa Trough deep water mass above the carbonate lysocline; (4) lower continental slope- trough b 相似文献
8.
青海南部治多-杂多-带下石炭统杂多群 总被引：1，自引：0，他引：1
在青海南部治多-杂多-带1／25万地质填图中，对杂多群进行了重新划分，自下而上分为下碳酸盐岩组、碎屑岩组和上碳酸盐岩组。下碳酸盐岩组为深灰色中层状生物屑灰岩、鲡粒灰岩夹泥岩、细粒石英砂岩，属于台地边缘浅滩相；碎屑岩组为灰色中层状细粒石英砂岩、泥岩夹灰岩、玄武岩，属于三角洲相、陆棚相和台地边缘浅滩相；上碳酸盐岩组为灰色中厚层状生物屑灰岩，见燧石结核和条带，为陆棚相和台地相沉积。丰富的筵类、非筵有孔虫、珊瑚化石，表明杂多群地质时代为早石炭世大塘期-德坞期。根据岩性组合、生物群面貌杂多群与青海南部杂多-囊谦地区杂多群、西藏东部昌都地区马查拉群可很好地对比。 相似文献
9.
川西北二叠系栖霞组小有孔虫动物群 总被引：1，自引：0，他引：1
川西北广元旺苍王家沟剖面二叠系栖霞组小有孔虫动物群由14属27种组成(含比较种、亚种而不含未定种),其中Globivalvulina属及Palaeotextularidae科的物种分异度最高,合计约占总种数的50%。在系统分类的基础上,建立了Globivalvulina组合,作为识别该区二叠纪最大海进时期的标志性动物群。通过对该剖面栖霞组小有孔虫动物群的研究,不仅丰富了四川盆地二叠纪有孔虫的资料,而且为川西北王家沟剖面栖霞组与华南其他地区同期地层的对比提供了更多生物方面的依据。 相似文献
10.
Variations of orbital-driven insolation, ice volume, and greenhouse gas effects have been proposed as major controlling factors in determining the timing and amplitude of Quaternary cyclic climate changes. However, it remains to be determined how the internal feedback in the tropical atmosphere and ocean and the coupling between the low- and high-latitude systems may have produced instability or non-cyclic changes in the long-term climate evolution. Such “abnormalities” have been reported increasingly from paleoclimatic reconstructions in East Asia and the western Pacific for a prolonged warm and humid climate interval during marine isotope stage (MIS) 13–15, ～475–610 kya. To better address the climate abnormality in MIS 13–15 that has been observed in the western Pacific, here we report high-resolution late Quaternary planktic foraminifer faunal abundance and faunal sea surface temperature (SST) records from the International Marine Past Global Change (IMAGES) program core MD972142, which was retrieved from the southeastern South China Sea (SCS). Our results indicate that the faunal assemblages and SSTs in the southeastern SCS express a substantially prolonged, unusual warm interglacial-type climate condition in MIS 13–15. The climate was abnormally warm during the cold MIS 14. Our study also suggests a lowering of sea surface salinity (SSS) during MIS 13–15. While the western Pacific climate experienced a persistently warm and humid period at MIS 14, a “normal” cooling (～2 °C) condition on the surface of the eastern equatorial Pacific existed concomitantly. While assessing possible interpretations of this “abnormal” climate interval in MIS 13–15, our study indicates that an enhanced interhemispheric and/or longitudinal temperature gradient across the basin-wide Pacific cannot be ruled out. A change in the sensitivity of the East Asian Monsoon (EAM) that controlled temperature and precipitation patterns in East Asia and the western Pacific is probably also important or responsible for this climate abnormality. Based on our evidence, we suggest that the tropical dynamics would have played a role in the climate abnormality in MIS 13–15, through maintaining or even increasing the longitudinal SST gradient in the equatorial Pacific, which may have intensified the low-latitude trade winds in the eastern component of the Walker Circulation that drove a longer duration and/or stronger intensity of the summer vs. winter EAM. 相似文献