Hinterland basin records of crustal thickening, surface uplift, and paleoclimate in the northern Central Andes

Kurt Sundell
Thursday, September 15, 2022 · 4:00 pm
ESB 5104-06
Hosted by
Joel Saylor
Speaker's Bio: 

Hinterland basins in the Central Andes contain valuable information on the complex history of mountain building and geodynamic processes active during Cordilleran orogenesis. However, exposures of these critical archives are rare due to structural overprinting and cover by intense late Cenozoic volcanism. We present ~2,600 m of newly measured Oligocene-Miocene stratigraphy, interpreted in the context of new U-Pb geochronology and trace element geochemistry of zircon, and published estimates of paleoelevation and paleoclimate. Results show a dramatic shift in depositional environment from fluvial to lacustrine evaporitic between 18 and 10 Ma, a transition that is coeval with rapid Miocene surface uplift interpreted as the result of mantle lithosphere foundering. This abrupt Miocene evolution of the northern Central Andes contrasts with a more prolonged crustal thickening history of the region. Jurassic to Neogene zircon extracted from volcanic rocks, sandstones, and river sediments reveal shifts in trace element ratios that suggest major crustal thickening at 80–55 Ma and 35–0 Ma, coincident with high-flux regional magmatism. An intervening magmatic lull due to shallow subduction obscures the magmatic record from 55-35 Ma during which thickening continued via crustal shortening. Protracted crustal thickening since the Late Cretaceous correlates with early elevation gain of the Central Andean western margin, but contrasts with Miocene establishment of near modern elevation and the onset of hyperaridity along the Pacific coast, highlighting their complex spatial and temporal relationship in what appears to be the end of a complete Cordilleran cycle.