CLIMATIC INFLUENCE ON A TECTONICALLY-DOMINATED LANDSCAPE; WESTERN TRANSVERSE RANGES, CA – INSIGHTS FROM MAPPING, GEOCHRONOLOGY AND MODELING
Our findings indicate that regional models for climatic control of some surficial processes are applicable to tectonically active areas in southern California, and lead to features such as flights of Pleistocene alluvial-fan terraces having ages that tend to correlate with regional chronologies and also axial-system Holocene arroyos and paleo-arroyos. We find evidence that tectonic influences on the sedimentary basin evolution dominated from the Miocene to sometime in the mid-Pleistocene, at which time a shift towards a more dynamic climate regime began to overprint tectonic signals. This is evidenced by a several-thousand-meter thick conformable and generally similarly-deformed Miocene to Pleistocene sequence of syn-tectonic basin-fills. Deposition of these terrestrial fills ended after a transition to a brief lacustrine episode sometime around ~740 ka. Since then, cyclic erosion and deposition has occurred as the Cuyama Valley transformed from a major sedimentary basin to a more topographically complex basin. Though tectonic activity continues, our application of new landscape evolution modeling indicates that many of the Late Pleistocene landforms can be explained by fluctuation in processes controlled primarily by climate.