Stratigraphic and structural evolution of the Tertiary Cosmelli Basin and its relationship to the Chile triple junction

At the Taitao Peninsula, in southern Chile, an active mid-ocean ridge is being subducted under the South American continent. Continental crust south of the current triple junction has experienced subduction of three ridge segments since the mid-Miocene. A series of Mid-Late Tertiary sedimentary basins lies inboard of the triple junction: the Cosmelli basin lies in the region which has experienced the earlier ridge subduction events. Within the Cosmelli basin fill four sequence boundaries are delineated, with an upward increase in degree of facies dislocation, which is believed to reflect increasing magnitudes of base level fall. The early basin fill was deforming due to contractional tectonics while the later basin fill was being deposited; these processes controlled accommodation space and thus stratigraphic architecture during much of the basin life. -from Authors