Department of Geosciences, University of Oslo, Oslo, 0371, Norway.
MARUM Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany.
Sci Rep. 2017 May 31;7(1):2557. doi: 10.1038/s41598-017-02817-7.
The geological record contains evidence for numerous pronounced perturbations in the global carbon cycle, some of which are associated with mass extinction. In the Carnian (Late Triassic), evidence from sedimentology and fossil pollen points to a significant change in climate, resulting in biotic turnover, during a time termed the 'Carnian Pluvial Episode' (CPE). Evidence from the marine realm suggests a causal relationship between the CPE, a global 'wet' period, and the injection of light carbon into the atmosphere. Here we provide the first evidence from a terrestrial stratigraphic succession of at least five significant negative C-isotope excursions (CIE)'s through the CPE recorded in both bulk organic carbon and compound specific plant leaf waxes. Furthermore, construction of a floating astronomical timescale for 1.09 Ma of the Late Triassic, based on the recognition of 405 ka eccentricity cycles in elemental abundance and gamma ray (GR) data, allows for the estimation of a duration for the isotope excursion(s). Source mixing calculations reveal that the observed substantial shift(s) in δC was most likely caused by a combination of volcanic emissions, subsequent warming and the dissociation of methane clathrates.
地质记录中包含了许多全球碳循环显著扰动的证据，其中一些与大规模灭绝有关。在卡尼期（晚三叠世），沉积学和化石花粉的证据表明，在被称为“卡尼期洪积事件”（CPE）的时期，气候发生了重大变化，导致生物更替。来自海洋领域的证据表明，CPE 与全球“湿润”时期以及轻碳注入大气之间存在因果关系。在这里，我们首次提供了来自陆地地层序列的证据，至少有五次通过 CPE 记录的显著负碳同位素偏移（CIE），这些偏移既存在于总有机碳中，也存在于特定植物叶蜡化合物中。此外，通过识别元素丰度和伽马射线（GR）数据中的 405 ka 偏心率周期，为晚三叠世 1.09 Ma 的浮动天文时间尺度的构建提供了依据，从而可以估算同位素偏移的持续时间。源混合计算表明，观察到的 δC 显著偏移很可能是火山喷发、随后的变暖以及甲烷笼形化合物的离解共同作用的结果。
