Onset of Glaciation Causes Rapid Increase in Exhumation Rate Before Relaxation Towards Steady-State: Detrital Apatite (U-Th)/He Record 6 Ma to Present in Central Patagonia

Detrital Thermochronometry Reveals That the Topography Along the Antarctic Peninsula is Not a Pleistocene Landscape

“…Our results demonstrate that in a location where glacial conditions established early (and topography adjusted early), the landscape does not necessarily undergo enhanced glacial erosion during subsequent global cooling, as has been previously proposed in Taylor et al (2004) and Young et al ( 2011). This result is consistent with observations in East Antarctica and Patagonia (Christeleit et al, 2017;Thomson et al, 2013;Willett et al, 2020); similar responses may be expected in other landscapes with long glacial histories. In a cooling climate, there are several factors that may affect the relationships between glacial erosion and topographic evolution, such as (i) feedbacks between topography and physical erosion, (ii) transitions between non-glacial to glacial conditions due to climatic variability, and (iii) the presence and distribution of subglacial meltwater.…”

“…Because this topographic change causes the catchment hypsometry to transition (e.g., V-shaped fluvial valley to U-shaped glacial valley), glacial erosion rates may slow down with time (e.g., Koppes & Montgomery, 2009;Shuster et al, 2011;Willett et al, 2020). Glacial erosion, itself, may also prevent high rates of glacial erosion from being sustained because, as glaciers erode portions of their upstream accumulation areas and incise bedrock to lower elevations, they can reduce their capacity to accumulate ice (Oerlemans 1984;Oerlemans 2002).…”

“…A few studies of this sort have demonstrated the importance of the local onset of alpine glaciation (vs. global cooling) as a key control on km-scale valley incision, and that limited erosion occurred during the deep chill of the Pleistocene. For example, glacial processes significantly modified the Patagonian Andes beginning by ~10-7.4 Ma (Christeleit et al, 2017;Mercer & Sutter, 1982;Thomson et al, 2010) and subsequently decelerated (Willett et al, 2020). Thermochronometric data from the of glacial valleys began ~34 Ma, during the initial expansion of the East Antarctic Ice Sheet.…”