Tempo and scale of late Paleocene and early Eocene carbon isotope cycles: Implications for the origin of hyperthermals
Tempo and scale of late Paleocene and early Eocene carbon isotope cycles: Implications for the origin of hyperthermals
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DOI：
10.1016/j.epsl.2010.09.004
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发表时间：
2010-10
影响因子：
5.3
通讯作者：
J. Zachos;H. McCarren;B. Murphy;U. Röhl;T. Westerhold
中科院分区：
文献类型：
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作者：
J. Zachos;H. McCarren;B. Murphy;U. Röhl;T. Westerhold
上古新世和下始新世以几个显著的(>；1‰)碳同位素(δ13C)漂移(CIE)为标志，这些漂移与瞬时全球变暖或热极大值一致，包括古新世-始新世热极大值。CIE主要在海洋沉积层序中记录，也在大陆层序中发现，偶尔发生，但似乎是由轨道强迫控制或触发的。为了限制CIE相对于长期基线变化的时间和规模，我们从东南大西洋ODP1262站发现的远洋沉积物剖面建立了一个452万年(MYR)长、高分辨率(~3kyr)的大宗沉积物碳同位素记录，横跨下始新世到上古新世(C25r-C24n)。这一段利用高分辨率岩心测井物性和地球化学记录进行了轨道调整，是迄今为止恢复的最完整的上古新统到下始新统层序。碳同位素记录的时间序列分析和XRF岩心扫描仪获得的高分辨率铁强度记录表明，整个古新世上段-下始新世，旋回变化主要集中在进动带(21kyr)和偏心带(100kyr和400kyr)。一般来说，δ13C中的极小值对应于Fe中的峰(即碳酸盐溶解)，这两个峰似乎都与偏心的极大值同相。这种协方差与海洋对同位素贫化碳的过量吸收一致，导致在高偏心率时期碳酸盐饱和度较低。这种关系包括所有晚古新世和早始新世，CIE通过轨道强迫确认了起搏。唯一的例外是PETM，它似乎与400 KYR周期不同，但可能与100 KYR周期同步，这强化了这样一个概念，即需要轨道强迫和/或额外的碳源以外的机制来解释这次事件的发生和不寻常的规模。
The upper Paleocene and lower Eocene are marked by several prominent (>1‰) carbon isotope (δ13C) excursions (CIE) that coincide with transient global warmings, or thermal maxima, including the Paleocene–Eocene Thermal Maximum (PETM). The CIE, which are recorded mainly in marine sedimentary sequences, have also been identified in continental sequences, occurred episodically, and yet appear to be paced or triggered by orbital forcing. To constrain the timing and scale of the CIE relative to long-term baseline variability, we have constructed a 4.52million year (myr) long, high-resolution (~3kyr) bulk sediment carbon isotope record spanning the lower Eocene to upper Paleocene (C25r–C24n) from a pelagic sediment section recovered at ODP Site 1262 in the southeast Atlantic. This section, which was orbitally-tuned utilizing high-resolution core log physical property and geochemical records, is the most stratigraphically complete upper Paleocene to lower Eocene sequence recovered to date. Time-series analysis of the carbon isotope record along with a high-resolution Fe intensity record obtained by XRF core scanner reveal cyclicity with variance concentrated primarily in the precession (21kyr) and eccentricity bands (100 and 400-kyr) throughout the upper Paleocene–lower Eocene. In general, minima in δ13C correspond with peaks in Fe (i.e., carbonate dissolution), both of which appear to be in phase with maxima in eccentricity. This covariance is consistent with excess oceanic uptake of isotopically depleted carbon resulting in lower carbonate saturation during periods of high eccentricity. This relationship includes all late Paleocene and early Eocene CIE confirming pacing by orbital forcing. The lone exception is the PETM, which appears to be out of phase with the 400-kyr cycle, though possibly in phase with the 100-kyr cycle, reinforcing the notion that a mechanism other than orbital forcing and/or an additional source of carbon is required to account for the occurrence and unusual scale of this event.