A calcareous nannofossil and organic geochemical study of marine palaeoenvironmental changes across the Sinemurian/Pliensbachian (early Jurassic, ~ 191 Ma) in Portugal
A calcareous nannofossil and organic geochemical study of marine palaeoenvironmental changes across the Sinemurian/Pliensbachian (early Jurassic, ~ 191 Ma) in Portugal
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DOI：
10.1016/j.palaeo.2016.02.009
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发表时间：
2016-05
期刊：
影响因子：
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通讯作者：
J. Plancq;E. Mattioli;B. Pittet;F. Baudin;L. V. Duarte;M. Boussaha;V. Grossi
中科院分区：
文献类型：
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作者：
J. Plancq;E. Mattioli;B. Pittet;F. Baudin;L. V. Duarte;M. Boussaha;V. Grossi
Sinemurian/Pliensbachia界线(~191Ma)被认为是浮游生物，特别是甲藻和球藻等初级生产者辐射的最重要的步骤之一。到目前为止，还没有详细的研究记录浮游生物组合的变化与跨越这一边界的古海洋变化有关。本研究的目的是利用微体古生物学和有机地球化学方法，研究葡萄牙卢西塔尼亚盆地S段中穆尔统/普连斯巴契亚界线上的古环境变化。钙质超微化石组合和类脂生物标记物数据的综合记录表明，由于海平面在边界以上的大幅上升，初级生产力下降。卢西塔尼亚盆地在西尼穆尔晚期海平面相对较低的情况下尤其受到限制，这种构造导致了黑色页岩的反复发育。在海平面急剧下降之后，在最早的普连斯巴契期，盆地逐渐变得更深、更开放，随后发生了一次重大海侵。海平面的上升似乎是一个全球特征，可能与连接特提斯和古太平洋的西班牙裔走廊的开放有关。这种开放引起的古海洋和古气候变化可能对球石生物的多样化起到了作用，首次发现或定居在特提斯水域的是胎盘石型球藻。
The Sinemurian/Pliensbachian boundary (~ 191 Ma) is acknowledged as one of the most important steps in the radiation of planktonic organisms, especially primary producers such as dinoflagellates and coccolithophores. To date, there is no detailed study documenting changes in planktonic assemblages related to palaeoceanographic changes across this boundary. The aim of this study is to characterize the palaeoenvironmental changes occurring across the Sinemurian/Pliensbachian boundary at the São Pedro de Moel section (Lusitanian Basin, Portugal) using micropalaeontology and organic geochemistry approaches. Combined calcareous nannofossil assemblage and lipid biomarker data document for a decrease in primary productivity in relation to a major sea-level rise occurring above the boundary. The Lusitanian Basin was particularly restricted during the late Sinemurian with a relatively low sea level, a configuration that led to the recurrent development of black shales. After a sharp sea-level fall, the basin became progressively deeper and more open during the earliest Pliensbachian, subsequently to a major transgression. This sea-level increase seems to have been a global feature and could have been related to the opening of the Hispanic Corridor that connected the Tethys and palaeo-Pacific oceans. The palaeoceanographic and palaeoclimatic changes induced by this opening may have played a role in the diversification of coccolithophores with the first occurrence or colonization of Tethyan waters by placolith-type coccoliths.