The middle Toarcian cold snap: Trigger of mass extinction and carbonate factory demise
The middle Toarcian cold snap: Trigger of mass extinction and carbonate factory demise
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DOI：
10.1016/j.gloplacha.2014.03.008
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发表时间：
2014-06
影响因子：
3.9
通讯作者：
François-Nicolas Krencker;S. Bodin;R. Hoffmann;G. Suan;E. Mattioli;L. Kabiri;K. Föllmi;A. Immenhauser-A.
中科院分区：
文献类型：
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作者：
François-Nicolas Krencker;S. Bodin;R. Hoffmann;G. Suan;E. Mattioli;L. Kabiri;K. Föllmi;A. Immenhauser-A.
普连斯巴契期和托阿尔西期(侏罗纪早期)以几次相对短暂的碳循环扰动、气候变化和动物群更替为特征。生物和非生物干扰的原因(S)目前尚不清楚，但最有可能的是与大火成岩省Karoo-Ferrar的岩浆活动增加有关。托尔西亚海洋缺氧事件(T-OAE)可能代表了这些事件中最极端的一次，因此，全球范围内的记录越来越充分。到目前为止，普连斯巴契亚-托尔西亚的其他关键时间段受到的关注要少得多。本文利用摩洛哥中央高等地图集的三个暴露良好和延伸的地层剖面，探讨了中Toarcian可变事件对浅海-浅海领域的影响。为了区分古环境模式和成岩模式，对112个块状泥晶样品的碳、氧同位素组成进行了分析，并与仔细筛选的腕足类化石的39个数据点进行了对比。此外，测定了109个微晶样品的磷浓度，以评价磷循环。在所有研究剖面中，都记录到中上托阿尔统由碳酸盐岩为主向碎屑岩为主的重大变化，表明存在一级碳酸盐生产危机。我们的结果表明，这些主要的沉积学模式与氧-同位素比值的增加和磷的积累速率降低相一致。这表明中托阿尔新世晚期碳酸盐岩斜坡危机与一次瞬时冷却事件有关，可能是由卡鲁大火成岩省背景下的脉冲大规模SO4呼出事件触发的。短期降温可能是由于大气CO2水平的下降而放大的，这与浅海碳酸盐降水的同期下降以及特提斯与大陆架之间的暖水团环流中断有关。这里显示的数据首次为T-OAE之后碳循环、大陆风化和浅海系统的耦合变化提供了证据。
The Pliensbachian and Toarcian (Early Jurassic) ages are characterised by several, relatively short-lived carbon cycle perturbations, climate change and faunal turnover. The cause(s) of biotic and abiotic disturbances remain unclear but most probably involved increased magmatic activity in the Karoo–Ferrar large igneous province. The Toarcian oceanic anoxic event (T-OAE) might represent the most extreme of these events, and as such, is becoming increasingly well documented worldwide. So far, other critical time intervals of the Pliensbachian–Toarcian have received considerably less attention. Here, the effects of the Middle Toarcian Variabilis event on the neritic–epeiric realm are explored making use of three well-exposed and extended stratigraphic sections in the Central High Atlas, Morocco. The carbon and oxygen isotopic compositions of 112 bulk micrite samples were analysed and placed against 39 data points from carefully screened brachiopod valves in order to differentiate between palaeo-environmental and diagenetic patterns. Additionally, the phosphorus concentrations of 109 micrite samples were determined to evaluate the P-cycling. In all studied sections, an upper middle Toarcian major change from carbonate- to clastics-dominated sedimentation is recorded, pointing to a first-order carbonate production crisis. Our results reveal that these major sedimentological patterns coincide with an increase of oxygen-isotope ratios as well as a decrease of phosphorous accumulation rates. This suggests that the late middle Toarcian carbonate ramp crisis was related to a transient cooling event, potentially triggered by pulsed massive SO4exhalation events in the context of the Karoo large igneous province. Short-term cooling was likely amplified by the drawdown of atmospheric CO2levels related to the coeval decline of neritic carbonate precipitation and the warm water mass circulation disruption between the Tethys and the continental shelf. The data shown here provide the first evidence for coupled changes in carbon cycling, continental weathering and neritic systems in the aftermath of the T-OAE.