Environmental perturbations at the early Eocene ETM2, H2, and I1 events as inferred by Tethyan calcareous plankton (Terche section, northeastern Italy)
Environmental perturbations at the early Eocene ETM2, H2, and I1 events as inferred by Tethyan calcareous plankton (Terche section, northeastern Italy)
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DOI：
10.1002/2016pa002940
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发表时间：
2016-09
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通讯作者：
R. D’Onofrio;V. Luciani;E. Fornaciari;L. Giusberti;F. B. Galazzo;E. Dallanave;T. Westerhold;M. Sprovieri;Sonia Telch
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文献类型：
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作者：
R. D’Onofrio;V. Luciani;E. Fornaciari;L. Giusberti;F. B. Galazzo;E. Dallanave;T. Westerhold;M. Sprovieri;Sonia Telch
近年来，一些始新世早期的超温流被研究，并从温度异常和海洋变化的角度进行了表征。这些气候扰动对生物群落的影响要小得多。在这里，我们提出了新的记录，从Terche部分（意大利东北部），第一次，整合了三个后古新世-始新世热最大（PETM）负碳同位素偏移（CIE）的南极有孔虫和钙质超微化石的数据。在Terche生成的生物磁性地层框架使我们能够自信地将这些CIE与始新世热最大值2（ETM 2），H2和I1事件联系起来。这些事件中的每一个都与以显著较低的碳酸钙含量（泥灰岩单元，MU）为特征的岩性异常相吻合。我们认为这些MU主要与陆源稀释增加的影响有关，因为溶解代理没有显示出显着的变化。在这些事件中，钙质浮游生物组合发生了显着变化，放射虫增加。观测到的变化表明，短暂的变暖和环境扰动，虽然更强烈的ETM 2期间，发生在每三个调查扰动。钙质浮游生物的变化表明，相对于事件发生前的条件，地表水富营养化程度有所增加，同时上层水体热分层也有所减弱。较高的养分排放量与气候变暖导致的水文循环加剧有关。这些条件在CIE早期恢复期间持续存在，这意味着环境和生物区系的恢复速度比碳循环慢。
Several early Eocene hyperthermals have been recently investigated and characterized in terms of temperature anomalies and oceanographic changes. The effects of these climatic perturbations on biotic communities are much less constrained. Here we present new records from the Terche section (northeastern Italy) that, for the first time, integrates data on planktic foraminifera and calcareous nannofossils across three post Paleocene-Eocene Thermal Maximum (PETM) negative carbon isotope excursions (CIEs). The bio-magnetostratigraphic framework generated at Terche allows us to confidently relate such CIEs to the Eocene Thermal Maximum 2 (ETM2), H2, and I1 events. Each of these events coincides with lithological anomalies characterized by significantly lower calcium carbonate content (marly-units, MUs). We interpret these MUs as mainly linked to an effect of increased terrigenous dilution, as dissolution proxies do not display significant variations. Calcareous plankton assemblages change significantly across these events and radiolarians increase. Observed changes suggest that transient warming and environmental perturbations, though more intense during ETM2, occurred during each of the three investigated perturbations. Variations among calcareous plankton suggest increase in surface-water eutrophication with respect to the pre-events conditions, coupled with a weakening of the upper water-column thermal stratification. Higher nutrient discharge was related to intensification of the hydrological cycle as a consequence of the warmer climate. These conditions persisted during the early CIE recovery, implying slower recovery rates for the environment and biota than for the carbon cycle.