Middle Eocene astronomically-tuned benthic stable isotopes, bulk stable isotopes and Ca/Fe-ratios of IODP Expedition 342 Sites U1408 and U1410

To come to a coherent middle Eocene timescale for the Atlantic, we re-evaluate the astrochronology of chrons C20n/C20r at International Ocean Discovery Program (IODP) Expedition 342 Sites U1408 and U1410 off Newfoundland. Based on the stratigraphic work of Cappelli et al., 2019 a two-site-composite for the chrons C20n and C20r (~42-46 Ma) was constructed by transferring U1410 samples to the U1408 depth-scale. We then used previously published (U1410; Vahlenkamp et al., 2018) and new (U1408) benthic and bulk stable isotopes (d^13^C and d^18^O) to derive a revised eccentricity-tuned astrochronology for the Expedition 342 composite. The astrochronologic tuning demonstrates that the contourite deposition (reflected by the Ca/Fe ratio) at the Newfoundland Ridge occurred under an amplified climatic response to obliquity during C20n and C20r – with intermittent “astronomical flickering” to precession. […]

为构建大西洋中部中新世时期的协调时标，我们对国际海洋发现计划（International Ocean Discovery Program，简称IODP）第342次考察的U1408和U1410站位处的C20n/C20r时序的星时学进行了重新评估。基于Cappelli等人在2019年的地层学研究，通过将U1410样品转移到U1408深度标尺，构建了C20n和C20r时序（约42-46百万年前）的两站位复合时序。随后，我们运用先前发表的（U1410；Vahlenkamp等，2018年）以及新的（U1408）底栖和总稳定同位素（δ^13^C和δ^18^O）数据，对第342次考察的复合时序进行了修订的偏心率调校星时学分析。星时学调校结果显示，新不伦瑞克岛脊处的浊流沉积（由Ca/Fe比值反映）在C20n和C20r时期，经历了对赤道倾斜的气候响应放大——伴随着间歇性的“天体闪烁”至黄赤交角进动。