Integrated chronostratigraphic calibration of the Oligocene-Miocene boundary at 24.0 +/- 0.1 MA from the CRP-2A drill core, Ross Sea, Antarctica

Wilson, Gary S.; Lavelle, Mark; McIntosh, William C.; Roberts, Andrew P.; Harwood, David M.; Watkins, David K.; Villa, Giuliana; Bohaty, Steven M.; Fielding, Chris R.; Florindo, Fabio; Sagnotti, Leonardo; Naish, Timothy R.; Scherer, Reed P.; Verosub, Kenneth L.. 2002 Integrated chronostratigraphic calibration of the Oligocene-Miocene boundary at 24.0 +/- 0.1 MA from the CRP-2A drill core, Ross Sea, Antarctica. Geology, 30 (11). 1043-1046. 10.1130/0091-7613(2002)030<1043:ICCOTO>2.0.CO;2

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Abstract/Summary

An expanded Oligocene-Miocene boundary interval recovered in the Cape Roberts Project CRP-2A core from beneath the Ross Sea, Antarctica, has yielded a high-resolution integrated chrono stratigraphy that has, in turn, enabled a new, more direct, calibra tion of magnetic polarity and biostratigraphic events. The Oligocene-Miocene boundary interval in the CRP-2A core comprises three ∼60-m-thick, rapidly deposited (>0.5 m/k.y.) sedimentary sequences (sequences 9, 10, and 11). In sequences 10 and 11, single-crystal, laser-fusion 40Ar/39Ar analyses of anorthoclase phenocrysts from two tephra horizons independently calibrate the CRP-2A magnetic-polarity stratigraphy and age model. Sequences 10 and 11 encompass subchron C6Cn.3n, which is dated as 24.3 ± 0.1 to 24.16 ± 0.1 Ma. Sequence 9 is interpreted to encompass subchron C6Cn.2n and the Oligocene-Miocene boundary, which is dated as 24.0 ± 0.1 Ma. These ages are ∼0.2 m.y. older than those of the geomagnetic polarity time scale calibrated from seafloor-spreading ridges and ∼0.9–1.3 m.y. older than the newly proposed astronomically calibrated ages. We contend that the discrepancy with the astronomically calibrated ages arises from a mismatch of three 406 k.y. eccentricity cycles or a 1.2 m.y. modulation of obliquity amplitude in the astronomical calibration of the Oligocene–Miocene time scale.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1130/0091-7613(2002)030<1043:ICCOTO>2.0.CO;2
Programmes:	BAS Programmes > Other
ISSN:	0091-7613
Additional Keywords:	chronostratigraphy, isotope dating, Antarctica, biostratigraphy, Cape Roberts Project
NORA Subject Terms:	Marine Sciences Earth Sciences
Date made live:	28 Mar 2012 13:47 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/17519

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