DETRITAL ZIRCON PROVENANCE TRENDS IN THE LARSEN BASIN, ANTARCTIC PENINSULA

The Larsen Basin is a nearly continuous late Mesozoic-early Cenozoic succession located east of the northernmost Antarctic Peninsula. The basin formed as a result of continental rifting during the mid-late Jurassic breakup of Gondwana, and is well-known as a key reference section for high-latitude Jurassic-Eocene paleobiology and paleoclimatology. Its sediments record significant tectonic, paleobiological, and paleoenvironmental events, including breakup-related rifting and volcanism, paleo-Pacific arc volcanism, the K/Pg extinction event, the onset of Oi-1 glaciation, and the opening of Drake Passage, while Cretaceous marine sediments deposited post-rift document high-latitude eustatic processes during and transitioning out of the Cretaceous hothouse. Detrital zircon geochronology provides additional insight into the tectonic history, sediment sourcing, and evolution of the basin and the proximal arc.

We present U-Pb analyses of detrital zircons from over 50 Larsen Basin sandstones. As expected in the early stages of rift basin formation, zircons in the Aptian-Campanian lower part of the section are primarily Mesozoic in age, reflecting dominant inputs from breakup-related volcanics and metasedimentary terranes of the proximal Antarctic Peninsula. Beginning in the late Campanian-early Maastrichtian, Paleozoic and Proterozoic populations emerge, often making up half or more of the total zircons in a sample. We propose two possible mechanisms for this dramatic provenance shift. Similar zircon populations are known in South Andean metamorphic complexes to the north and Ellsworth Mountain metasediments to the south, suggesting possible long-distance sedimentary connections between distal sources and the Larsen Basin. Alternatively, a small number of Antarctic Peninsula gneisses contain appropriately-aged zircons. Thermochronological studies of the region suggest rapid cooling and exhumation related to terrane accretion in Palmer Land circa 75 Ma, consistent with the onset of the provenance shift in the Larsen basin, though whether these rock bodies are or were large enough to provide the necessary proportion of older grains remains unclear.

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Session No. 210

Stratigraphy

Tuesday, 27 September 2016: 1:30 PM-5:30 PM

Room 402 (Colorado Convention Center)

Geological Society of America Abstracts with Programs. Vol. 48, No. 7
doi: 10.1130/abs/2016AM-287904

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