桑给巴尔海峡(坦桑尼亚西北印度洋)第四纪洪水--利用多代研究确定古海洋学模式和古环境

IF 2.6 3区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY
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引用次数: 0

摘要

多代古环境分析是一种很有前途的工具,可用于重建浅海环境中大陆-海洋或空气-海洋的相互作用。晚更新世至全新世中期强烈的气候变异尤其说明了这一点。地球化学代用指标(143Nd/144Nd、87Sr/86Sr、δ18O 和 δ13C 同位素分析、正烷烃分析和生物标志物研究)与微古生物学数据(有孔虫、钙质浮游动物和硅藻)的独特组合,精确地描述了桑给巴尔海峡(坦桑尼亚西北印度洋)两次海洋洪水(全新世中期和更新世晚期)的特征。与全新世相比,晚更新世时期气候干旱。晚更新世洪水泛滥时期(115-130 ka)所特有的完全寡营养环境在全新世中期(5-10 ka)被强降雨间歇性打断,营养物质输入增加。全新世和更新世晚期海藻草甸占主导地位,与现代海草生态系统占主导地位的环境形成鲜明对比。全新世和晚更新世期间桑给巴尔海峡相对非放射源的εNd特征表明,非洲大陆前寒武纪基底的河流输入具有很大的影响。海水主要从南部流入,这与东非沿岸流的流向以及 3 月至 10 月季风的方向一致。作为海草/海藻草甸类型生态系统的指标,特定硅藻类群的存在可能是未来有望应用的工具。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Quaternary floodings in the Zanzibar Channel (NW Indian Ocean, Tanzania) – Identifying palaeoceanographic patterns and palaeoenvironment using a multiproxy study

Multiproxy palaeoenvironmental analyses represent a promising tool for complex reconstructions of continent-sea or air-sea interactions in shallow marine environments. This is in particular illustrated by the case of strong climatic variations in the late Pleistocene to mid-Holocene. A unique combination of geochemical proxies (143Nd/144Nd, 87Sr/86Sr, δ18O and δ13C isotope analyses, n-alkane analysis and biomarker study) together with micropalaeontological data (foraminifera, calcareous nannoplankton and diatoms) allowed to precisely characterise two marine floodings (mid-Holocene and late Pleistocene) in the Zanzibar Channel (NW Indian Ocean, Tanzania). The climate of the late Pleistocene interval was arid compared to the Holocene. The fully oligotrophic environment characteristic of the late Pleistocene flooding (∼115–130 ka) was episodically interrupted by intervals of intense rainfall with episodes of increased nutrient input during the mid-Holocene (∼5–10 ka). The dominance of seaweed meadows in the Holocene and late Pleistocene contrasts with the modern environment dominated by seagrass ecosystems. Relatively non-radiogenic εNd signatures in the Zanzibar Channel during the Holocene and late Pleistocene indicate a strong influence of riverine input draining the Precambrian basement on the African mainland. The main inflow of seawater was from the south, consistent with the flow direction of the East African Coastal Current and the directions of the March to October monsoon winds. A promising tool for future applications as indicators of seagrass/seaweed meadow type ecosystems may be the presence of specific diatom taxa.

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来源期刊
Marine Geology
Marine Geology 地学-地球科学综合
CiteScore
6.10
自引率
6.90%
发文量
175
审稿时长
21.9 weeks
期刊介绍: Marine Geology is the premier international journal on marine geological processes in the broadest sense. We seek papers that are comprehensive, interdisciplinary and synthetic that will be lasting contributions to the field. Although most papers are based on regional studies, they must demonstrate new findings of international significance. We accept papers on subjects as diverse as seafloor hydrothermal systems, beach dynamics, early diagenesis, microbiological studies in sediments, palaeoclimate studies and geophysical studies of the seabed. We encourage papers that address emerging new fields, for example the influence of anthropogenic processes on coastal/marine geology and coastal/marine geoarchaeology. We insist that the papers are concerned with the marine realm and that they deal with geology: with rocks, sediments, and physical and chemical processes affecting them. Papers should address scientific hypotheses: highly descriptive data compilations or papers that deal only with marine management and risk assessment should be submitted to other journals. Papers on laboratory or modelling studies must demonstrate direct relevance to marine processes or deposits. The primary criteria for acceptance of papers is that the science is of high quality, novel, significant, and of broad international interest.
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