Synorogenic Neogene foreland basins of the southern Central Andes (32-35 degrees S) provide a sensitive, but poorly constrained, record of the spatial and temporal patterns of tectonics, magmatism and orogenic exhumation across this classic convergent continental arc system. Basin evolution is strongly influenced by the segmentation of the Nazca plate: North of 33 degrees S, the subducting slab is subhorizontal, producing basement-involved thick-skinned contractional deformation, a broken foreland, and sparse magmatism; south of 33 degrees S, the subducting slab attains a normal subduction angle, with episodic magmatic activity, thin-skinned structural deformation and development of stacked piggy back basins. Segmentation of the margin into flat, transitional and normal slab segments produces longitudinal variations in arc magmatism, structural deformation and basin development that provide an ideal laboratory to examine contrasting along-strike patterns of orogenic exhumation and basin evolution. The primary objective of this investigation is to document the temporal-spatial pattern in Neogene orogenic exhumation and its relation to structural deformation, topographic evolution, basin development and sediment dispersal patterns in the southern Central Andes (32-35 degrees S). More specifically, this investigation will examine the relationship of spatial and temporal distribution of synorogenic foreland basins to variation in slab dip, the variation in pattern and rate of orogenic exhumation along strike, and the control of pre-existing basement configuration on orogenic exhumation and basin development. A systematic field-based research program will integrate isotopic analyses of detrital zircon (U-Pb, Hf, (U-Th)/He) with stratigraphic analysis, whole rock geochemistry and apatite (U-Th)/He thermochronology to constrain the timing, episodicity, provenance, depositional architecture and subsidence rate of Neogene synorogenic basins.
The south-central Andes Mountains provides an ideal laboratory to examine the dynamic linkage between the rate and magnitude of orogenic exhumation and the spatial and temporal pattern of adjacent basin development. Understanding this linkage will provide insight into the use of basinal stratigraphy to constrain the magnitude and rate of tectonic uplift in seismically active regions, the evaluation of the accumulation and preservation of economic resources and the accurate reconstruction of earth history. The project is tightly integrated with two international (Argentina, Chile, France, and United States) multidisciplinary regional-scale investigations studying Neogene crustal dynamics along three cross-Andean transects (32-35 degrees S). Students and faculty from University of Wisconsin Eau Claire and San Diego State University will collaborate closely with these groups in field and laboratory work and joint publications. Research in Argentina will be integral in interdisciplinary experiential learning activities at the University of Wisconsin Eau Claire. The project is supported by the Tectonics Program and the Office of International & Integrative Affairs.
