Stratigraphic Evolution of a Prograding Shelf-Slope Depositional System, Upper Cretaceous Tres Pasos and Dorotea Formations, Magallanes Basin, Chile

Brian W. Romans, Stanford University, Dept. of Geological & Environmental Sciences, Stanford, CA, [email protected]

Upper Cretaceous outcrops in the foothills of the Patagonian Andes in southern South America record the transition from deep- to shallow-water sedimentation during filling of the Magallanes foreland basin. Previous workers have interpreted the coeval nature between shelf and deep marine slope strata from regional information but the detailed stratal architecture and system evolution remain unknown. The goal of this project is to determine the genetic link between slope deposits of the Upper Cretaceous Tres Pasos Formation and the shallow-marine/deltaic Paleocene Dorotea Formation in the Ultima Esperanza District of southern Chile. A multi-scale investigation will: (1) document the variability of facies and sedimentary body architecture of sandstone-rich slope deposits, (2) establish a high-resolution stratigraphic framework in which to examine the basin architecture and evolution, and (3) examine spatial and temporal relationships of the sediment source areas with provenance analyses (e.g. sandstone petrography, detrital zircon geochronology, etc.). These results will provide refinement and/or revision of stratigraphic models for prograding siliciclastic shelf-to-basin systems, with an emphasis on slope accretion. Furthermore, detailed documentation of large, three-dimensional exposures of sand-rich slope deposits within this broader context will improve the understanding and predictive capabilities regarding facies distribution and architecture in analogous subsurface systems.