【直播】【“沉积之声”学术论坛】深时旋回和气候（Deep Time Cyclostratigraphy and Climate）

本系列报告由沉积之声主办，于2021年6月5日19:00开始，授权蔻享学术进行网络直播。

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“沉积之声”学术论坛第7期有幸邀请到乔治梅森大学教授Linda Hinnov和MARUM-海洋环境科学中心研究员David De Vleeschouwer为我们介绍深时旋回和气候。

报告内容简要介绍

报告1

(Linda Hinnov)：The Triassic Lofer Cyclothems of the Dachstein Limestone, Northern and Southern Calcareous Alps, western Europe

Abstract: The Lofer cyclothems characterize the Late Norian-Rhaetian shallow marine Dachstein Limestone of the Northern Calcareous Alps of northern Austria (Fischer, 1964) and Southern Calcareous Alps of northeastern Italy (Cozzi et al., 2005). The meter-scale Lofer cyclothems are composed of three shallowing-upward subfacies–megalodont limestone, loferites and paleosols–and vertically stacked in a pattern that is suggestive of forcing by astronomically forced sea-level oscillations. Recent analysis of Italian exposures (Hinnov and Cozzi, 2021) has revealed that orbital eccentricity, obliquity and precession index frequencies characterize the Lofer cyclothemic sequence, including strong 405-kyr (g2-g5) metronomic cycling that, with future establishment of a global chronostratigraphic anchor point from carbon isotopes or magnetic reversal stratigraphy, will enable precise correlation to remote locations, e.g., the Newark Basin, St. Audrie’s Bay, Colorado Plateau and Junggar Basin.

报告2(David De Vleeschouwer)：Timing and pacing of the Late Devonian mass extinction event regulated by eccentricity and obliquity
Abstract：The Late Devonian envelops one of Earth’s big five mass extinction events at the Frasnian–Famennian boundary (374Ma). Environmental change across the extinction severely affected Devonian reef-builders, besides many other forms of marine life. Yet, cause- and-effect chains leading to the extinction remain poorly constrained as Late Devonian stratigraphy is poorly resolved, compared to younger cataclysmic intervals. In this presentation, I'll present a global orbitally calibrated chronology across this momentous interval, applying cyclostratigraphic techniques. The astronomical timescale stipulates that 600 kyr separate the lower and upper Kellwasser positive δ13C excursions. The latter excursion is paced by obliquity and is therein similar to Mesozoic intervals of environmental upheaval, like the Cretaceous Ocean-Anoxic-Event-2 (OAE-2). This obliquity signature implies coincidence with a minimum of the 2.4 Myr eccentricity cycle, during which obliquity prevails over precession, and highlights the decisive role of astronomically forced “Milankovitch” climate change in timing and pacing the Late Devonian mass extinction.

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编辑：黄琦

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