Presentations by Drs. Mike Kaplan and Andrew Lloyd.
Possible linkages between glaciation, geodynamics, and volcanism: A Case Study of Pali Aike, southern Patagonia
Abstract:
In a soon to be submitted NSF proposal, we seek to understand better the source of basaltic-alkaline volcanism at Pali Aike in southern Patagonia and the mechanisms that modulate it. Pliocene to near present (?) fissure volcanism in the extra-Andean Pali Aike area is to some extent enigmatic because of its great distance from the youngest portion of the Patagonia slab window (~750 km to the northwest) and other regions of contemporaneous back-arc volcanism (e.g., ~600 km to the north) that have well imaged slow mantle anomalies linked to the slab window. Pali AIke is >150 km east of the Cordillera and ~300 km east of the active Pacific rim. In contrast, regional seismic images suggest less prominent (i.e., faster) anomalies beneath Pali Aike, seemingly at odds with the volcanism observed at the surface, and larger scale models suggest upper-most mantle wave speeds somewhat slower than the global average with fast wave speeds associated with subducted slabs between 300-800 km depth. In both cases seismic images suffer from a distinct lack of seismic stations around Pali Aike and north in central and eastern Argentina, which are required to improve seismic images beneath Patagonia. Furthermore, Pali Aike’s geographic location places it in contact with the Patagonia Ice Sheet from >1.1 Ma to ~700 ka, and thereafter lobes of the ice sheet were still within 50 km. The setting raises questions about the role the ice sheet might have played in promoting melt production and effusive events, including around an older underlying Jurassic rift. To tackle these questions, we will bring together field-lab-modeling approaches and expertise in glacial history and paleoclimate, geodynamics and geophysical analyses, and petrology, volcanism and tectonics to: 1) improve seismic images of Earth structure from the transition zone to the crust, 2) improve dating and geochemically interrogate the melt source and assent evolution, 3) produce improved inferences of the thermomechanical state based on new seismic images and geochemical constraints, and 4) explore how ice sheet evolution modulates crustal stresses through space and time at Pali Aike.
