Along-strike variation in crustal shortening and kinematic evolution of the base of a retroarc fold-and-thrust belt: Magallanes, Chile 53°S-54°S
The Late Cretaceous closure of the Late Jurassic–Early Cretaceous Rocas Verdes basin resulted in the development of the Patagonian fold-and-thrust belt and Magallanes foreland basin between 50°S and 54.5°S. New geologic maps, structural data, and two retrodeformed, line-balanced cross sections from the Magallanes region of Chile (53°S–54°S) constrain the kinematic evolution and along-strike correlations of deformation that occurred at the base of the fold-and-thrust belt near the brittle-ductile transition. The stratigraphic architecture of the predecessor basin controlled the position of regional decollement levels. During the initial stage of closure (Albian–Campanian), the floor of the Rocas Verdes basin was imbricated and thrust onto the continental margin to form a regional decollement within Jurassic–Lower Cretaceous shale. Continued shortening resulted in the deepening of the decollement to a ductile shear zone that formed