On the duration of magnetochrons C24r and C25n and the timing of early Eocene global warming events:: Implications from the Ocean Drilling Program Leg 208 Walvis Ridge depth transect
On the duration of magnetochrons C24r and C25n and the timing of early Eocene global warming events:: Implications from the Ocean Drilling Program Leg 208 Walvis Ridge depth transect
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DOI：
10.1029/2006pa001322
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发表时间：
2007-04-06
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影响因子：
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通讯作者：
Zachos, James C.
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文献类型：
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作者：
Westerhold, Thomas;Roehl, Ursula;Zachos, James C.
在海洋钻探计划 (ODP) 第 208 段期间，在沃尔维斯海岭（大西洋东南部）超过 2200 米的深度横断面上的多个孔中钻出的五个部分产生了第一个完整的古近纪早期深海记录。在这里，我们展示了高分辨率地层记录，跨越了古新世晚期到始新世早期大约 430 万年的时间间隔。该区间包括古新世-始新世最热事件 (PETM) 以及始新世最热事件 (ETM) 2 事件。利用无损 X 射线荧光 (XRF) 岩心扫描记录和船上颜色数据制定了详细的年代表。这些记录用于细化每个站点的船上衍生拼接复合深度，然后使用 ODP 站点 1051 的记录来建立该间隔内的连续时间序列。广泛的光谱分析表明，古近纪早期沉积旋回主要受短（100 kyr）和长（405 kyr）偏心率旋回调制的进动支配。对多个地点与进动相关的周期进行计数会导致磁同步器 C24r 和 C25n 持续时间的修正估计。来自 XRF 数据的进动分量的振幅调制与最新的地球轨道偏心率模型之间的直接比较表明，PETM 和 ETM2 的开始与 100 kyr 的偏心率最大值有关。这两个事件都与 405 kyr 偏心率周期最大值偏移了大约四分之一的周期，主要区别在于 PETM 滞后，而 ETM2 领先 405 kyr 偏心率最大值。 PETM、ETM2 和磁时线边界的绝对年龄估计与重新校准的辐射年龄和最新的地球轨道偏心率模型一致，目前无法精确确定，因为这些方法的不确定性太大。尽管如此，我们提供了两种可能的调整选项，这证明了开发基于整个古近纪稳定的 405 kyr 偏心率旋回的旋回地层框架的潜力。
Five sections drilled in multiple holes over a depth transect of more than 2200 m at the Walvis Ridge (SE Atlantic) during Ocean Drilling Program (ODP) Leg 208 resulted in the first complete early Paleogene deep-sea record. Here we present high-resolution stratigraphic records spanning a similar to 4.3 million yearlong interval of the late Paleocene to early Eocene. This interval includes the Paleocene-Eocene thermal maximum (PETM) as well as the Eocene thermal maximum (ETM) 2 event. A detailed chronology was developed with nondestructive X-ray fluorescence (XRF) core scanning records and shipboard color data. These records were used to refine the shipboard-derived spliced composite depth for each site and with a record from ODP Site 1051 were then used to establish a continuous time series over this interval. Extensive spectral analysis reveals that the early Paleogene sedimentary cyclicity is dominated by precession modulated by the short (100 kyr) and long (405 kyr) eccentricity cycles. Counting of precession-related cycles at multiple sites results in revised estimates for the duration of magnetochrons C24r and C25n. Direct comparison between the amplitude modulation of the precession component derived from XRF data and recent models of Earth's orbital eccentricity suggests that the onset of the PETM and ETM2 are related to a 100-kyr eccentricity maximum. Both events are approximately a quarter of a period offset from a maximum in the 405-kyr eccentricity cycle, with the major difference that the PETM is lagging and ETM2 is leading a 405-kyr eccentricity maximum. Absolute age estimates for the PETM, ETM2, and the magnetochron boundaries that are consistent with recalibrated radiometric ages and recent models of Earth's orbital eccentricity cannot be precisely determined at present because of too large uncertainties in these methods. Nevertheless, we provide two possible tuning options, which demonstrate the potential for the development of a cyclostratigraphic framework based on the stable 405-kyr eccentricity cycle for the entire Paleogene.