Orbitally tuned timescale and astronomical forcing in the middle Eocene to early Oligocene
Orbitally tuned timescale and astronomical forcing in the middle Eocene to early Oligocene
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DOI：
10.5194/cp-10-955-2014
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发表时间：
2013-12
影响因子：
4.3
通讯作者：
T. Westerhold;U. Röhl;H. Pälike;R. Wilkens;P. Wilson;G. Acton
中科院分区：
文献类型：
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作者：
T. Westerhold;U. Röhl;H. Pälike;R. Wilkens;P. Wilson;G. Acton
抽象。解读地球系统过程的驱动机制，包括表达为古海洋事件的气候动力学，需要一个完整的，连续的，高分辨率的地层学，是非常准确的日期。在这项研究中，一个强大的天文校准的年龄模型构建了中始新世早渐新世间隔（31-43马），以允许更详细的研究在这段时间内发生的异常气候事件，包括中始新世气候最佳和始新世-渐新世过渡。这项工作的一个目标是准确地确定始新世中期到渐新世早期的复合剖面的年代，该剖面是在太平洋赤道年龄样带（PEAT，IODP Exp. 320/321）。新时标的地层格架是基于对已发表和新的高分辨率记录中稳定长偏心率周期的识别，这些记录包括来自ODP站点171 B-1052、189-1172、199 -1218和207-1260以及IODP站点320-U1333的散装和底栖稳定同位素、校准的XRF岩心扫描和磁性地层数据，和320-U1334跨越磁极性Chrons C12 n到C20 n。随后，进行了对La 2011轨道解的记录的轨道调谐。由此产生的新的时间尺度修改和完善现有的轨道调谐年龄模型和地磁极性的时间尺度从31至43马。新确定的始新世-渐新世界线的绝对年龄验证了在意大利马西尼亚诺全球层型剖面和点确定的天文调谐年龄33.89 Ma。通过中晚始新世和早渐新世的气候控制的沉积变化的地球化学记录的汇编表明，在离心率带，很容易调整到最新的天文解决方案的强大力量。倾角驱动的周期性仅在2.4百万年偏心率周期最小值约35.5，38.3和40.1马是明显的。
Abstract. Deciphering the driving mechanisms of Earth system processes, including the climate dynamics expressed as paleoceanographic events, requires a complete, continuous, and high-resolution stratigraphy that is very accurately dated. In this study, a robust astronomically calibrated age model was constructed for the middle Eocene to early Oligocene interval (31–43 Ma) in order to permit more detailed study of the exceptional climatic events that occurred during this time, including the middle Eocene climate optimum and the Eocene–Oligocene transition. A goal of this effort is to accurately date the middle Eocene to early Oligocene composite section cored during the Pacific Equatorial Age Transect (PEAT, IODP Exp. 320/321). The stratigraphic framework for the new timescale is based on the identification of the stable long eccentricity cycle in published and new high-resolution records encompassing bulk and benthic stable isotope, calibrated XRF core scanning, and magnetostratigraphic data from ODP Sites 171B-1052, 189-1172, 199-1218, and 207-1260 as well as IODP Sites 320-U1333, and 320-U1334 spanning magnetic polarity Chrons C12n to C20n. Subsequently orbital tuning of the records to the La2011 orbital solution was conducted. The resulting new timescale revises and refines the existing orbitally tuned age model and the geomagnetic polarity timescale from 31 to 43 Ma. The newly defined absolute age for the Eocene–Oligocene boundary validates the astronomical tuned age of 33.89 Ma identified at the Massignano, Italy, global stratotype section and point. The compilation of geochemical records of climate-controlled variability in sedimentation through the middle-to-late Eocene and early Oligocene demonstrates strong power in the eccentricity band that is readily tuned to the latest astronomical solution. Obliquity driven cyclicity is only apparent during 2.4 myr eccentricity cycle minima around 35.5, 38.3, and 40.1 Ma.