Using Aerial Photos and Field Survey Methods to Monitor Fan Sedimentation and Landscape Evolution

The Mecca Hills at the southern end of the San Andreas strike-slip fault system exemplifies a transpression zone and provides valuable paleoenvironmental data for southernmost California to examine relationship between erosion and landscape development. Clarifying the relationships of the formation of such a transpressional region will help to construct and constrain regional erosion, sediment and landscape models. This study examines the relationships of faulting, fan sedimentation and watershed landscape development in Mecca Hills. The hypothesis of this study is that the extensional faulting related to the San Andreas Fault controls the fan sedimentation in the Northwest of the Mecca Hills. In the northwest region of the Mecca Hills, a succession of landforms, based on the aerial photographic interpretation and field mapping, two upland sections in the Northwest portion of the Mecca Hills were examined in detail to measure the faults, watershed fan sedimentation and watershed landscape evaluation. This study chose nine typical profiles that cross the fans, traces, and the washes to measure the distances and the angles, and then got the three-dimensional profiles maps for the reconstruction of the erosion, sedimentation, and landscape evolution processes. Through field surveying, mapping and aerial photos analysis for the examination of a succession of landforms in the study area, this study found that the San Andreas extensional faulting system directly influenced fan sedimentation as well as the watershed's landscape evolution in the study area. The findings of this study are that the landscape evolution is the result of a complex process in which a series of factors including climate factors, uplifting processes, and erosion processes occurred resulting in the landforms observed today. This paper is a pilot study for reconstructing the processes of erosion, sediment and landscape evolution of a proto-mountain range in the Mecca Hills.