Abstract
The Paleocene (66–56Ma) was a critical time interval for understanding recovery from mass extinction in high palaeolatitudes when global climate was warmer than today. A unique sedimentary succession from Seymour Island (Antarctic Peninsula) provides key reference material from this important phase of the early Cenozoic. Dinoflagellate cyst data from a 376m thick stratigraphical section, including the Cretaceous–Paleogene boundary, is correlated with biozones from New Zealand, the East Tasman Plateau and southeastern Australia. A detailed age model is suggested for the López de Bertodano (LDBF) and Sobral (SF) formations based on dinoflagellate cyst biostratigraphy and U–Pb dating of zircons, supported by correlated magnetostratigraphy and strontium isotope values from macrofossils. The top of the LDBF is confirmed as latest Maastrichtian to earliest Danian (~66.2–65.65Ma) in age. The overlying SF is mostly Danian in age, with an inferred hiatus near the top overlain by sediments dated as ?late Thanetian. Rare Apectodinium homomorphum first appear in the uppermost SF; the earliest in situ record from Antarctica. The distribution of marine and terrestrial fossils from uppermost Cretaceous to Eocene sediments in Patagonia, Antarctica, New Zealand and Australia required both sea and land connections between these fragments of Gondwana. Fossil evidence and reconstructions of Antarctic palaeogeography and palaeotopography reveal evidence for persistent embayments in the proto-Weddell and Ross Sea regions at this time. We conclude that a coastal dispersal route along the palaeo-Pacific margin of Gondwana could explain the fossil distribution without requiring a transAntarctic strait or closely spaced archipelago. A region in the West to East Antarctic boundary zone, elevated until the early Paleogene, perhaps acted as a site for high elevation ice caps. This supports fossil, geochemical and sedimentological evidence for cold climate intervals and significant sea level falls during the Maastrichtian and Paleocene.
Highlights
The Paleocene (66–56 Ma) was a time of cooler global climate between the greenhouse phases of the mid Cretaceous and Eocene (Zachos et al, 2001; Royer, 2006; Zachos et al, 2008)
Despite recent work on Paleocene successions in the low and mid palaeolatitudes (e.g. Hollis et al, 2012, 2014; Storme et al, 2014), little is known about the implications of these events for high southern latitude biota, or what they can tell us about Antarctic palaeogeography in the final phases of Gondwana fragmentation
Previous work has refined the age of the oldest part of the Seymour Island succession as Maastrichtian to earliest Danian using dinoflagellate cyst biostratigraphy correlated to magnetostratigraphy and strontium isotope stratigraphy (Askin, 1988a; McArthur et al, 1998; Bowman et al, 2012; Tobin et al, 2012; Bowman et al, 2013a)
Summary
The Paleocene (66–56 Ma) was a time of cooler global climate between the greenhouse phases of the mid Cretaceous and Eocene (Zachos et al, 2001; Royer, 2006; Zachos et al, 2008). Previous work has refined the age of the oldest part of the Seymour Island succession (the uppermost Snow Hill Island Formation and the López de Bertodano Formation) as Maastrichtian to earliest Danian using dinoflagellate cyst biostratigraphy correlated to magnetostratigraphy and strontium isotope stratigraphy (Askin, 1988a; McArthur et al, 1998; Bowman et al, 2012; Tobin et al, 2012; Bowman et al, 2013a). Close taxonomic similarity of the Paleocene dinoflagellate cyst floras across remnants of the palaeo-Pacific margin of Gondwana provides a broader context for this study
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