Quantifying Tectonic and Glacial Controls on Topography: Patagonia, South America
Final Report Abstract
This project resulted in production of a large number of new thermochronology data and field observations over >5° latitude of the Patagonian Andes. Scientific outcomes of this project were able to address the original goals of the proposal. More specifically, we found: 1) the spatial pattern of bedrock thermochronometer cooling across transects in the northern and southern Patagonian Andes document the youngest ages in high-temperature systems (e.g. AFT, ZHe, and ZFT) occur immediately east of the present day high-topography regions of the orogen (regardless of latitude). Ages are progressively older when moving westward or eastward from the high topography; 2) The previous pattern in higher-temperature thermochronometer ages can best be explained by the long-term (Cenozoic) tectonic history of the orogen, and are relatively insensitive to the more recent glacial history. The highest rates of tectonically driven exhumation (~0.5 – 1 mm/yr) are located where the youngest ages were observed, near the high topography of the range; 3) The spatial pattern of bedrock low-temperature thermochronometer data (e.g. AHe, and to some degree AFT ages) are more uniform. This pattern reflects the onset of pervasive late Miocene glaciation of the range; 4) thermo-kinematic modeling and inversion for pre-glacial paleotopography of the range documents a factor of 2–5 increase (from previous tectonically driven exhumation) in erosion rates coincident with the onset of glacial erosion. The magnitude of increase in erosion is similar in both the northern and southern Patagonian Andes; Finally, 5) application of detertial (tracer) thermochronology techniques document that glacial erosion was focused at, or below, the LGM equilibrium line altitude. This result provides observational confirmation of previous theoretical (model) based approaches for quantifying long-term glacial erosion processes. Overall, the project was deemed a success by the principal investigators. Several new scientific questions resulted from the study that will guide our future research in the region. In particular, much remains to be learned about how individual, different, glacial events in the region varied in their topographic effect and if (as many models predict) the earlier glacial events were more severe in their topographic effect than the LGM. Evaluating this requires sampling of (sparse) older glacial deposits preserved in the region.
Publications
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2016. Late Cenozoic exhumation of the Southern Patagonian Andes (47°S) constrained by low-temperature thermochronology and inverse numerical modeling. Thermo 2016, 15th International Conference on Thermochronology, Maresias – Brazil, p. 143
Georgieva, V., Sobel, E.R., Sobczyk, A., Gallagher, K., Schildgen, T., Ehlers, T.A., and Strecker, M.R.
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2019. Effects of slab-window, alkaline volcanism, and glaciation on thermochronometer cooling histories, Patagonian Andes. Earth and Planetary Science Letters, 511, 164–176
Georgieva, V., Gallagher, K., Sobczyk, A., Sobel, E.R., Schildgen, T.F., Ehlers, T.A., and Strecker, M.R.
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2019. Tectonic and glacial controls on exhumation in the Southern Patagonian Andes (47°S lat). 22nd International Conference on Deformation Mechanisms, Rheology and Tectonics (DRT-2019). Tübingen, Germany. 2019
Andrić, N., Falkowski, S., Ehlers, T.A., Georgieva, V., Glotzbach, C., Strecker, M.R.
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2019. Tectonic and glacial controls on topographic evolution in the Southern Patagonian Andes (47°S lat). Geophysical Research Abstract, Vol. 21. EGU2019 EGU General Assembly 2019
Andrić, N., Falkowski, S., Ehlers, T.A., Georgieva, V., Glotzbach, C., Strecker, M.R.
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2020. Exhumation pulses in the Southern Patagonian Andes (Torres del Paine, 51°S). Conference GeoUtrecht 2020
Andrić-Tomašević, N., Falkowski, S., Aghakhani, A., Ehlers, T.A.
