USING DETRITAL GEOCHRONOLOGY TO ASSESS THE OPENING OF MARINE GATEWAYS

The disruption of previously connected continental landmasses can cause or conduce profound changes in ocean circulation, regional and global climate, and biogeography. However, the actual importance of these marine gateways is often difficult to assess because of challenges in constraining the timing and nature of their opening. Sediment provenance analysis of Paleogene sandstones on opposite sides of Drake Passage suggests that detrital geochronology may provide valuable insight into the timing and mechanism of gateway opening. U-Pb detrital-zircon geochronology of the Magallanes foreland basin of southernmost Argentina and the Larsen Basin of the northern Antarctic Peninsula indicate that the two regions were receiving sediment from fundamentally different sources throughout the period ca. 58-34 Ma. Moreover, these data reveal a dramatic sediment provenance shift at ca. 40 Ma in the Magallanes basin, approximately coincident with independent thermochronologic and marine geochemistry evidence of an apex in Scotia arc tectonics. Together, these results suggest the opening of Drake Passage may have begun prior to the Eocene, and was more directly influenced by the kinematics of deformation in the Patagonian orocline. These and other sediment provenance analyses may thus constitute an important tool for constraining the opening history of marine gateway systems with sufficiently complete detrital records.