Layering in the Paleocene/Eocene boundary of the Millville core is drilling disturbance.
Layering in the Paleocene/Eocene boundary of the Millville core is drilling disturbance.
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Millville 岩心古新世/始新世边界的分层是钻井干扰。
DOI：
10.1073/pnas.1322077111
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发表时间：
2014
影响因子：
11.1
通讯作者：
Pearson PN
中科院分区：
文献类型：
--
作者：
Pearson PN
在对美国大西洋海岸平原（大洋钻探计划174 X-Millville）沉积物岩心的研究中，Wright和Sworker（1）声称已经解决了13年来古新世/始新世碳同位素漂移（CIE）的开始。如此快速的变化需要大量的同位素轻碳瞬间释放到海洋/大气中，这意味着彗星撞击。这种说法是基于对沉积物岩心中的韵律层的解释，即年度偶联，但在这里，有人提出，它们是钻井干扰的产物。当粘土岩被旋转取芯时，它们会破碎成“饼干”，随着钻井的进行，这些饼干在岩心筒内旋转（2）。泥浆可以被注入它们之间和周围，后来硬化成毫无特色的泥状夹层。我们在坦桑尼亚的一些始新世岩心中观察到了类似的特征（3）。饼干和分离物的交替可以令人惊讶地均匀，给人一种有节奏的寝具的假象。然而，这些分离物与结块的泥是一致的，切片时是光滑的，不像原始的沉积物，它有一个粗糙的纹理。已发表的岩心照片（参考文献1中的图1）清楚地显示了这些独特的特征（图1）。
In a study of a sediment core from the US Atlantic Coastal Plain (Ocean Drilling Program Site 174X-Millville), Wright and Schaller (1) claim to have resolved the onset of the Paleocene/Eocene carbon isotope excursion (CIE) across 13 y. Such a rapid change would require an enormous and instantaneous release of isotopically light carbon into the ocean/atmosphere, implicating comet impact. The claim rests on the interpretation of rhythmic layering in the sediment core as annual couplets but here it is proposed that they are an artifact of drilling disturbance. When claystones are rotary cored they can fracture into “biscuits” that spin within the core barrel as drilling progresses (2). Slurry can be injected between and around them, later hardening into featureless muddy partings. We have observed similar features in some Eocene cores from Tanzania (3). Alternation of biscuits and partings can be surprisingly uniform, giving the false appearance of rhythmic bedding. However, the partings are congruent with the caking mud and are smooth when sliced, unlike the original sediment, which has a hackly texture. The published core photograph (figure 1 in ref. 1) clearly shows these distinctive features (Fig. 1).