Have the southernmost Andes been curved since Late Cretaceous time? An analog test for the Patagonian Orocline

Constraints on deformation of the Southern Andes since the Cretaceous from anisotropy of magnetic susceptibility

“…Paleomagnetic constraints indicate that the presentday shape of the Southern Andes was likely already acquired in the Late Cretaceousearly Cenozoic before the formation of the Magallanes fold-and-thrust belt. Models considering the indentation of a curved rigid indenter during the Cenozoic (e.g., Ghiglione and Cristallini, 2007) to explain the formation of the Magallanes fold-andthrust belt are, therefore, more consistent with the paleomagnetic evidence. However, the rigid indenter models proposed by Ghiglione and Cristallini (2007) produced a slightly convergent pattern of deformation paths, much less pronounced than the radial strain field characterizing the Magallanes fold-and-thrust belt.…”

“…Cretaceous-Paleocene the Southern Andes have represented a curved-to-foreland belt, similarly to the rigid indenter models proposed by Ghiglione and Cristallini (2007).…”

“…5 basement formed a curved rigid indenter that produced the compressional pattern observed in the Magallanes fold-and-thrust belt, as shown by sand-box models (Ghiglione and Cristallini, 2007). Latest models proposed a two-stage evolution of the curvature of the Southern Andes consisting of a Late Cretaceous phase of oroclinal bending during closure of the Rocas Verdes basin, followed by formation of the primary curvature of the Magallanes fold-thrust belt during the Cenozoic (Poblete et al, 2014).…”

“…A major thrusting event and uplift in the Paleogene has been also constrained using zircon (U-Th)/He dating from the eastern domains of the southern Patagonian Andes (Fosdick et al, 2013). The Eocene tectonics became much stronger towards the south affecting in particular Tierra del Fuego due to fast ~NE-directed subduction of the Phoenix plate between 47-28 Ma (Ramos and Aleman, 2000;Olivero and Martinioni, 2001;Kraemer, 2003;Ghiglione and Ramos, 2005;Ghidella, 2005, 2012;Ghiglione and Cristallini, 2007). Apatite fission track, and apatite and zircon (U-Th)/He ages constrained compressive events in the western domains of the Patagonian Andes to the late Oligocene (30-23 Ma;…”

South Georgia and Gondwana's Pacific Margin: Lost in translation?

“…Worse still, however, paleomagnetic data equivocate on the idea of oroclinal bending by any means in the southern Andes, at least since the opening of the Rocas Verdes Basin, and suggest that the process if it occurred at all probably only affected the region marginward of the basin (e.g. Burns et al,1980;Kraemer, 2003;Ghiglione and Cristallini, 2007;Maffione et al, 2009). Right now, for South Georgia, it seems safest to conclude that oroclinal bending processes are neither a suitable explanation for a Jurassic Pacific margin placement nor for a placement neighbouring Tierra del Fuego.…”