Orbital pacing of Eocene climate during the Middle Eocene Climate Optimum and the chron C19r event: Missing link found in the tropical western Atlantic
Orbital pacing of Eocene climate during the Middle Eocene Climate Optimum and the chron C19r event: Missing link found in the tropical western Atlantic
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DOI：
10.1002/ggge.20293
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发表时间：
2013-11
期刊：
影响因子：
3.7
通讯作者：
T. Westerhold;U. Röhl
中科院分区：
文献类型：
--
作者：
T. Westerhold;U. Röhl
高分辨率地层学对于详细破译气候变率和理解地球历史事件的因果关系至关重要。始新世中晚期为碳循环模型提供了一个完美的试验场，以重建从温室到冰窖世界的转变，因此需要一个精确的时间尺度来解码气候驱动机制。在这里，我们介绍了来自ODP站点1260 （Leg 207）的新结果，该结果涵盖了热带西大西洋一个独特的扩展的中始新世剖面（C18r至C20r，晚Lutetian至早Bartonian），包括C19r时瞬态过热事件和中始新世气候最佳（MECO）。为了建立详细的旋回地层，我们利用XRF扫描1260号岩心获得了铁强度记录。我们修正了船载复合剖面，建立了旋回地层，并利用异常偏心调制岁差旋回进行轨道调谐。新的天文年代学修正了磁极年代学C19n到C20n的年龄，验证了极长偏心极小值在40.2和43.0 Ma在轨道解中的位置，并将天文调谐地质年代学扩展到44 Ma。新数据首次为C19r事件的轨道起搏提供了明确的证据，并可能参与了极长（2.4 myr）偏心周期对MECO演化的贡献。
A high‐resolution stratigraphy is essential toward deciphering climate variability in detail and understanding causality arguments of events in earth history. Because the middle to late Eocene provides a perfect testing ground for carbon cycle models to reconstruct the transition from a hothouse to an icehouse world, an accurate time scale is needed to decode climate‐driving mechanisms. Here we present new results from ODP Site 1260 (Leg 207) which covers a unique expanded middle Eocene section (magnetochrons C18r to C20r, late Lutetian to early Bartonian) of the tropical western Atlantic including the chron C19r transient hyperthermal event and the Middle Eocene Climate Optimum (MECO). To establish a detailed cyclostratigraphy we acquired iron intensity records by XRF scanning Site 1260 cores. We revise the shipboard composite section, establish a cyclostratigraphy and use the exceptional eccentricity modulated precession cycles for orbital tuning. The new astrochronology revises the age of magnetic polarity chrons C19n to C20n, validates the position of very long eccentricity minima at 40.2 and 43.0 Ma in the orbital solutions and extends the Astronomically Tuned Geological Timescale back to 44 Ma. For the first time the new data provide clear evidence for an orbital pacing of the chron C19r event and a likely involvement of the very long (2.4 myr) eccentricity cycle contributing to the evolution of the MECO.