Using aerial photos and field survey methods tomonitor fan sedimentation and landscape evolution

摘要

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