Age Assessment of Eocene-Pliocene Drill Cores Recovered During the SHALDRIL II Expedition, Antarctic Peninsula

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© 2011 by the American Geophysical Union. Pre-Quaternary strata were recovered from four sites on the continental shelf of the eastern Antarctic Peninsula during the SHALDRIL II cruise, NBP0602A (March-April 2006). Fully marine shelf sediments characterize these short cores and contain a mixture of opaline, carbonate-walled, and organic-walled microfossils, suitable for both biostratigraphic and paleoenvironmental studies. Here we compile biostratigraphic information and provide age assessments for the Eocene-Pliocene intervals of these cores, based primarily on diatom biostratigraphy with additional constraints from calcareous nannofossil and dinoflagellate cyst biostratigraphy and strontium isotope dating. The Eocene and Oligocene diatom floras are illustrated in nine figures. A late Eocene age (37-34 Ma) is assigned to strata recovered in Hole 3C, and a late Oligocene age (28.4-23.3 Ma) is determined for strata recovered in Hole 12A. Middle Miocene (12.8-11.7 Ma) and early Pliocene (5.1-4.3 Ma) ages are assigned to the sequence recovered in holes 5C and 5D, and an early Pliocene age (5.1-3.8 Ma) is interpreted for cores recovered in holes 6C and 6D. These ages provide chronostratigraphic ground truthing for the thick sequences of Paleogene and Neogene strata present on the northwestern edge of the James Ross Basin and on the northeastern side of the Joinville Plateau, as interpreted from a network of seismic stratigraphic survey lines in the drilling areas. Although representing a coarse-resolution sampling of the complete sedimentary package, the well-constrained ages for these cores also allow for the broad reconstruction of marine and terrestrial paleoenvironments in the Antarctic Peninsula for the late Eocene-to-early Pliocene time interval.

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Tectonic, Climatic, and Cryospheric Evolution of the Antarctic Peninsula

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