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| Titel |
Drilling disturbance and constraints on the onset of the Paleocene–Eocene boundary carbon isotope excursion in New Jersey |
| VerfasserIn |
P. N. Pearson, E. Thomas |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 11, no. 1 ; Nr. 11, no. 1 (2015-01-16), S.95-104 |
| Datensatznummer |
250117120
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| Publikation (Nr.) |
 copernicus.org/cp-11-95-2015.pdf |
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| Zusammenfassung |
| The onset of the Paleocene–Eocene thermal maximum (PETM) and associated
carbon isotope excursion (CIE; approx. 56 Mya) was geologically abrupt, but
it is debated whether it took thousands of years or was effectively
instantaneous. Wright and Schaller (2013) published a significant new record
of the onset of the CIE, and claimed that it could be resolved across 13
annual layers in a drill core through the Marlboro clay at Millville, New
Jersey (Ocean Drilling Program (ODP) Leg 174X). Supporting evidence for
similar layering was reported from another New Jersey drill site, Wilson Lake
B, and a photograph of the Marlboro clay in outcrop (Wright and Schaller,
2014). Such a short duration would imply an instantaneous perturbation of the
atmosphere and surface ocean and the impact of a comet or asteroid as the
likely cause. However, Pearson and Nicholas (2014) suggested, based on the
published core photographs, that the layers in the Marlboro clay cores could
be artifacts of drilling disturbance, so-called biscuiting, wherein the
formation is fractured into layers or biscuits and drilling mud is injected
in between the layers. (We now prefer the term core discing
following Kidd, 1978.) Here we report new observations on the cores which
support that interpretation, including concentric grooves on the surfaces of
the core discs caused by spinning in the bit, micro-fracturing at their
edges, and injected drilling mud. We re-interpret the limited outcrop
evidence as showing joints rather than sedimentary layers. We argue that
foraminifer concentrations in the sediments are far too high for the layers
to have been annually deposited in turbid waters at depths of 40–70 m,
indicating that the onset of the CIE in the Marlboro clay likely took on the
order of millennia, not years (Zeebe et al., 2014). Re-coring of Millville
aimed at minimizing drilling disturbance to allow a higher-resolution study
of the carbon isotope excursion is highly desirable. |
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