Early Jurassic carbon-isotope perturbations in a shallow-water succession from the Tethys Himalaya, southern hemisphere
Early Jurassic carbon-isotope perturbations in a shallow-water succession from the Tethys Himalaya, southern hemisphere
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南半球特提斯喜马拉雅浅水序列中的早侏罗世碳同位素扰动
DOI：
10.1127/nos/2021/0650
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发表时间：
2021-01
影响因子：
2.2
通讯作者：
Marco Franceschi
中科院分区：
文献类型：
--
作者：
Zhong Han;Xiumian Hu;Marcelle BouDagher-Fadel;Hugh C. Jenkyns;Marco Franceschi
早侏罗世的特征是极端的碳循环扰动，与突然的环境和气候变化。然而，证据主要来自西特提斯和北方欧洲的部分：位于北方半球的地方。本文介绍了形成于特提斯东南部（南半球）的西藏基奥陶台地的新记录的生物地层学（大型底栖有孔虫）、沉积学和碳酸盐碳同位素（δ 13 Ccarb）数据。其中，有6个有孔虫带：晚Sinemurian期的Textulariopsis sinemuriensis、Pliensbachian期的Planiseptacompressa、Bosniella oenensis、Cyclor-bitopsella tibetica和Streptocyclammina liasica，以及最早的Toarcian期的Siphovalvulina sp. A.基于生物地层学，δ 13 C碳数据允许与来自特提斯西部和北方欧洲的同时代记录进行对比，通过识别负和正δ 13 C偏移。负的δ 13 C偏移是Sinemurian-Pliensbachian边界事件（SPBE）和margaritatus-spinatum带边界事件（MSBE）的特征，正的δ 13 C偏移是margaritatus带事件（ME）的特征。早侏罗世的相演化表明，在全球海平面上升的背景下，发生在基奥托台地的碳酸盐沉积的建立与SPBE部分一致，并与其他同时代的平台，碳酸盐生产的负向移动后，主要是由骨架碳酸盐。此外，基奥托台地上Lithotis动物群的扩散是在SPBE之后同位素值反弹之后。这一现象已在特提斯西部观察到，并表明全球生物钙化事件所代表的Lithiotis动物群的繁荣可能已经同步发生在特提斯，可能反映了更有利的海洋条件后，SPBE的创造。生物地层学数据表明，某些指数较大的底栖有孔虫在MSBE发生水平附近灭绝，可能是由于这一事件的有害影响。然而，在更北的地区，Lithotis动物群在Pliensbachian晚期在特提斯的浅水平台上持续存在，直到在Toarcian早期消失。
The Early Jurassic was characterized by extreme carbon-cycle perturbations that are associated with abrupt environmental and climatic change. However, the evidence mainly derives from sections in the western Tethys and northern Europe: localities situated in the northern hemisphere. This paper presents new records of biostratigraphical (large benthic foraminiferal), sedimentological and carbonate carbon-isotope (δ13Ccarb) data from the Tibetan Kioto Platform formed in the southeastern Tethys (southern hemisphere) during the Sinemurian–earliest Toarcian interval. Six foraminiferal zones have been recognized: late Sinemurian Textulariopsis sinemuriensis, Pliensbachian Planisepta compressa, Bosniella oenensis, Cyclor-bitopsella tibetica and Streptocyclammina liasica, and earliest Toarcian Siphovalvulina sp. A. Based on biostratigraphy, δ13Ccarb data allow correlation with coeval records from the western Tethys and northern Europe by the identification of both negative and positive δ13C excursions. The negative excursions characterize the Sinemurian–Pliensbachian boundary event (SPBE) and the margaritatus–spinatum zone boundary event (MSBE); the positive δ13C excursion characterizes the margaritatus zone event (ME). Facies evolution in the Early Jurassic indicates that the establishment of carbonate sedimentation on the Kioto Platform occurred in the context of a global sea-level rise partly coincident with the SPBE and that, in common with other coeval platforms, carbonate production following the negative shift was predominantly made up of skeletal carbonates. Furthermore, the spread of the Lithiotis Fauna on the Kioto Platform followed the rebound of isotopic values after the SPBE. This phenomenon has been observed in the western Tethys and suggests that the global biocalcification event represented by the flourishing of the Lithiotis Fauna may have occurred synchronously across the Tethys, possibly reflecting the creation of more favourable marine conditions after the SPBE. Biostratigraphical data indicate that certain index larger benthic foraminifera became extinct around the onset level of the MSBE, likely due to the deleterious impact of this event. However, as in more northerly localities, the Lithiotis Fauna persisted during the late Pliensbachian in the shallow-water platforms of the Tethys until its disappearance in the early Toarcian.