TY - JOUR A1 - Georgieva, Viktoria A1 - Gallagher, Kerry A1 - Sobczyk, Artur A1 - Sobel, Edward A1 - Schildgen, Taylor F. A1 - Ehlers, Todd A1 - Strecker, Manfred T1 - Effects of slab-window, alkaline volcanism, and glaciation on thermochronometer cooling histories, Patagonian Andes JF - Earth & planetary science letters N2 - Southern Patagonia is a prime example of ongoing oceanic ridge collision and slab-window formation sustained over several million years. The impact of these phenomena on the thermal structure and exhumation of the crust have been mainly assessed with low-temperature thermochronology of bedrock samples. Here, we infer thermal histories from new and existing thermochronological data from the region of most recent ridge collision. In particular, we evaluate the potential far-reaching thermal effects of the evolving slab window, which have previously been considered responsible for patterns of late Miocene reheating associated with back-arc alkaline volcanism. Our model results define protracted cooling since similar to 15 Ma and stepwise exhumation since the late Miocene. The pattern of stepwise exhumation closely matches the onset of Patagonian glaciation at 7 Ma and the successive pulse of glacial incision coeval with neotectonic activity since 3-4 Ma that are also documented by independent geological and geomorphological evidence in the region. Importantly, our findings challenge the recently suggested lack of glacial erosion and incision since 5 Ma in this region. Furthermore, in contrast to previous modelling studies, we find that the available data do not evidence a previously proposed northward-propagating heating event associated with alkaline volcanism. We hypothesize that the anomalous alkaline volcanism in the Patagonian back-arc might be related to trench-orthogonal tears aligned with transform faults in the subducting plate. The substantial differences from the previous modelling procedure on some of the same samples is demonstrated to result from an important lack of convergence in model runs. (C) 2019 Elsevier B.V. All rights reserved. KW - inverse thermal modelling KW - thermochronology KW - apatite (U-Th)/He KW - apatite fission track KW - Patagonian Andes KW - slab window Y1 - 2019 U6 - https://doi.org/10.1016/j.epsl.2019.01.030 SN - 0012-821X SN - 1385-013X VL - 511 SP - 164 EP - 176 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Georgieva, Viktoria A1 - Melnick, Daniel A1 - Schildgen, Taylor F. A1 - Ehlers, Todd A1 - Lagabrielle, Yves A1 - Enkelmann, Eva A1 - Strecker, Manfred T1 - Tectonic control on rock uplift, exhumation, and topography above an oceanic ridge collision: Southern Patagonian Andes (47 degrees S), Chile JF - Tectonics N2 - The subduction of bathymetric anomalies at convergent margins can profoundly affect subduction dynamics, magmatism, and the structural and geomorphic evolution of the overriding plate. The Northern Patagonian Icefield (NPI) is located east of the Chile Triple Junction at similar to 47 degrees S, where the Chile Rise spreading center collides with South America. This region is characterized by an abrupt increase in summit elevations and relief that has been controversially debated in the context of geodynamic versus glacial erosion effects on topography. Here we present geomorphic, thermochronological, and structural data that document neotectonic activity along hitherto unrecognized faults along the flanks of the NPI. New apatite (U-Th)/He bedrock cooling ages suggest faulting since 2-3 Ma. We infer the northward translation of an similar to 140 km long fore-arc sliver-the NPI block-results from enhanced partitioning of oblique plate convergence due to the closely spaced collision of three successive segments of the Chile Rise. In this model, greater uplift occurs in the hanging wall of the Exploradores thrust at the northern leading edge of the NPI block, whereas the Cachet and Liquine-Ofqui dextral faults decouple the NPI block along its eastern and western flanks, respectively. Localized extension possibly occurs at its southern trailing edge along normal faults associated with margin-parallel extension, tectonic subsidence, and lower elevations along the Andean crest line. Our neotectonic model provides a novel explanation for the abrupt topographic variations inland of the Chile Triple Junction and emphasizes the fundamental effects of local tectonics on exhumation and topographic patterns in this glaciated landscape. Y1 - 2016 U6 - https://doi.org/10.1002/2016TC004120 SN - 0278-7407 SN - 1944-9194 VL - 35 SP - 1317 EP - 1341 PB - American Geophysical Union CY - Washington ER -