Southern Chile crustal structure from teleseismic receiver functions: Responses to ridge subduction and terrane assembly of Patagonia

Abstract

Abstract Continental crustal structure is the product of those processes that operate typically during a long tectonic history. For the Patagonia composite terrane, these tectonic processes include its early Paleozoic accretion to the South America portion of Gondwana, Triassic rifting of Gondwana, and overriding of Pacific Basin oceanic lithosphere since the Mesozoic. To assess the crustal structure and glean insight into how these tectonic processes affected Patagonia, we combined data from two temporary seismic networks situated inboard of the Chile triple junction, with a combined total of 80 broadband seismic stations. Events suitable for analysis yielded 995 teleseismic receiver functions. We estimated crustal thicknesses using two methods, the H-k stacking method and common conversion point stacking. Crustal thicknesses vary between 30 and 55 km. The South American Moho lies at 28–35 km depth in forearc regions that have experienced ridge subduction, in contrast to crustal thicknesses ranging from 34 to 55 km beneath regions north of the Chile triple junction. Inboard, the prevailing Moho depth of ∼35 km shallows to ∼30 km along an E-W trend between 46.5°S and 47°S; we relate this structure to Paleozoic thrust emplacement of the Proterozoic Deseado Massif terrane above the thicker crust of the North Patagonian/Somún Cura terrane along a major south-dipping fault.