Evolution of the Toarcian (Early Jurassic) carbon-cycle and global climatic controls on local sedimentary processes (Cardigan Bay Basin, UK)
Evolution of the Toarcian (Early Jurassic) carbon-cycle and global climatic controls on local sedimentary processes (Cardigan Bay Basin, UK)
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DOI：
10.1016/j.epsl.2017.12.037
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发表时间：
2018-02
影响因子：
5.3
通讯作者：
Weimu Xu;M. Ruhl;H. Jenkyns;M. Leng;J. Huggett;D. Minisini;C. Ullmann;J. Riding;J. Weijers
中科院分区：
文献类型：
--
作者：
Weimu Xu;M. Ruhl;H. Jenkyns;M. Leng;J. Huggett;D. Minisini;C. Ullmann;J. Riding;J. Weijers
早侏罗世晚期Toarcian阶段是侏罗纪时期最温暖的时期，在Toarcian早期海洋缺氧事件（T-OAE; ~ 183 Ma）开始时，中纬度地区全球气温突然上升高达~ 7°C。T-OAE在两个半球的海洋和大陆演替中得到了广泛的研究，其特征是缺氧和富氧水域的广泛扩张，富含有机物的黑色页岩在地理上的广泛沉积，以及气候和环境的扰动。然而，人们对T-OAE之后的气候和环境过程知之甚少，这在很大程度上是由于缺乏对地层约束良好和完整的沉积档案的研究。在这里，我们提供了综合的地球化学和物理代用数据（高分辨率碳同位素数据（δ 13c）、整体和分子有机地球化学、无机岩石学、矿物特征、主要元素和微量元素浓度），这些数据来自英国威尔士卡迪根湾盆地Llanbedr （Mochras Farm）钻孔完整的生物地层和扩展的整个陶塔ian演系。利用这些数据，我们(1)构建了首个高分辨率生物地层学校准的几乎完整的陶拉坎期化学地层学参考记录；(2)建立了卡迪根湾盆地的古海洋学和沉积条件；(3)表明，半深海卡迪根湾盆地的T-OAE以重力流沉积的出现为标志，可能与全球大陆边缘和更深海洋（陆架）盆地的沉积物通量增强有关。(4)探索卡迪根湾盆地早陶拉纪（tenuicostatum和蛇形带）的黄铁矿形成可能与全球海洋硫酸盐浓度低和内陆铁供应增加有关，以响应气候引起的水文循环变化、全球风化速率和大规模硫化物和蒸发岩沉积。
Abstract The late Early Jurassic Toarcian Stage represents the warmest interval of the Jurassic Period, with an abrupt rise in global temperatures of up to∼ 7° C in mid-latitudes at the onset of the early Toarcian Oceanic Anoxic Event (T-OAE;∼ 183 Ma). The T-OAE, which has been extensively studied in marine and continental successions from both hemispheres, was marked by the widespread expansion of anoxic and euxinic waters, geographically extensive deposition of organic-rich black shales, and climatic and environmental perturbations. Climatic and environmental processes following the T-OAE are, however, poorly known, largely due to a lack of study of stratigraphically well-constrained and complete sedimentary archives. Here, we present integrated geochemical and physical proxy data (high-resolution carbon-isotope data (δ 13 C), bulk and molecular organic geochemistry, inorganic petrology, mineral characterisation, and major-and trace-element concentrations) from the biostratigraphically complete and expanded entire Toarcian succession in the Llanbedr (Mochras Farm) Borehole, Cardigan Bay Basin, Wales, UK. With these data, we (1) construct the first high-resolution biostratigraphically calibrated chemostratigraphic reference record for nearly the complete Toarcian Stage,(2) establish palaeoceanographic and depositional conditions in the Cardigan Bay Basin,(3) show that the T-OAE in the hemipelagic Cardigan Bay Basin was marked by the occurrence of gravity-flow deposits that were likely linked to globally enhanced sediment fluxes to continental margins and deeper marine (shelf) basins, and (4) explore how early Toarcian (tenuicostatum and serpentinum zones) siderite formation in the Cardigan Bay Basin may have been linked to low global oceanic sulphate concentrations and elevated supply of iron (Fe) from the hinterland, in response to climatically induced changes in hydrological cycling, global weathering rates and large-scale sulphide and evaporite deposition.