NSF Tectonics (EAR #0635923)
Collaborative Research: Lithospheric weakening, deep crustal flow and the initiation of orogenesis at a noncollisional convergent margin in the Andes.
Together with: Keith Klepeis (University of Vermont); Geoff Clarke (University of Sydney)
Thomson, S.N. Klepeis, K.A., Hervé, F. and Calderón, M. (2011). Late Oligocene erosion of Cordillera Darwin (southernmost South America) associated with rift margin uplift and opening of the west Scotia Sea. 11th International Symposium on Antarctic Earth Sciences, Edinburgh, UK.
McAtamney, J., Klepeis, K., Mehrtens, C., Thomson, S.N., Betka, P., Rojas, L. and Snyder, S. (2011). Along-strike variability of back arc basin collapse and the initiation of sedimentation in the Magallanes foreland basin, southernmost Andes (53 - 54.5°S), Tectonics, v. 30, p. TC5001, doi:10.1029/2010TC002826
Maloney, K.T., Clarke, G.L., Klepeis, K.A., Fanning, C.M. & Wang, W. (2011). Crustal growth during back-arc closure: Cretaceous exhumation history of Cordillera Darwin, southern Patagonia, Journal of Metamorphic Geology, v. 29, p. 649-672Klepeis, K.A., McAtamney, J., Mehrtens, C.J., Thomson, S.N., Betka, P.M. and Mosher, S. 2011. Along-strike variability of coupled hinterland-foreland processes during formation of the Magallanes foreland basin, Patagonian Andes. GSA Abstracts with Programs, Vol. 43, No. 5, p. 441.
Klepeis, K.A., Betka, P.M., Clarke, G., Fanning, C.M., Hervé, F., Rojas, L., Mpodozis, C., & Thomson, S.N. (2010). Ophiolite obduction and continental underthrusting during Cretaceous closure of the Rocas Verdes basin, Cordillera Darwin, Patagonian Andes. Tectonics, v.29, TC3014, doi:10.1029/2009TC002610.
Hervé, F., Fanning, C.M., Pankhurst, R.J., Mpodozis, C., Klepeis, K.A., Calderón, M. & Thomson, S.N. (2010). Detrital zircon SHRIMP U-Pb age study of the Cordillera Darwin Metamorphic Complex: sedimentary sources and implications for the evolution of the Pacific margin of Gondwana. Journal of the Geological Society, London, 167, p. 555-568, doi: 10.1144/0016-76492009-124.
McAtamney, J., Klepeis, K.A., Mehrtens, C.J. & Thomson, S.N. (2009). The transition from extensional rift basin to compressional retro-arc foreland basin in the southernmost Andes (54.5°S): New provenance data from Bahía Brookes and Seno Otway. GSA Abstracts with Programs, Vol. 41, No. 7.
Klepeis, K.A., Betka, P.M., Alvarez, J., Poblete, F., Thomson, S.N., Gehrels, G.E. & Clarke, G. (2008). Tectonic Evolution of a Doubly-Vergent, Thick-Skinned Fold and Thrust Belt in the Patagonian Andes, Southernmost South America. GSA Abstracts with Programs, Vol. 40, No. 6, p. 548.
Intellectual Merit: A fundamental problem in continental tectonics centers on resolving how orogenesis initiates and develops at noncollisional convergent margins. Field studies and thermomechanical models demonstrate that the strength and rheology of the pre-orogenic overriding plate is a crucial factor that controls structural variability in these settings. In the Andes, the archetypal noncollisional orogen, a leading cause of pre-orogenic weakening involved the formation and destruction of large extensional basins during the Mesozoic. However, in most areas, the effects of Neogene orogenesis has obscured the geologic record of how these transitions controlled the initial rise of the Cordillera from below sea level. Even fewer areas preserve a record of how the deep crust evolved through these changing tectonic regimes. The aim of this project is to determine through direct measurement how the high temperatures, thin crust, and rheological stratifications that result from intraplate extension affected the thermal and structural evolution of the deep crust during subsequent shortening. This observational approach is possible because the Darwin Complex in southernmost Chile preserves a nearly complete record of the thermal and structural evolution of the middle crust during the formation and destruction of a large extensional basin. The proposed research involves using these unique exposures to test the contrasting ways in which pre-orogenic conditions arising from intraplate extension can influence orogenic growth during subsequent contraction. We have designed an international project that combines expertise in the fields of structural geology, metamorphic petrology, U-Pb geochronology (zircon, titanite, monazite), and thermochronology (40Ar-39Ar, K-Ar, fission track and (U-Th)/He) to determine the ages of deformation and the tectonic/thermal evolution of Darwin Complex.
Last Modified: December 2nd, 2011