Lithologic evidence of the Transverse Ranges as a native terrane

The Transverse Ranges (TR) of southern California can be subdivided structurally into eight tectonic blocks. Analysis of paleoflow indicators and clast lithologies of Upper Cretaceous conglomerates within these blocks provide insights into the tectonic history of the TR and the interrelationships between the tectonic blocks. A thick conglomeratic section of Upper Cretaceous sediments is preserved in the Santa Ynez block. Paleoflow indicators show a northerly transport direction throughout the section. Lithologic analysis reveals a section dominated by sedimentary and quartzite clasts, with subordinate numbers of felsic plutonic and various volcanic lithologies. Plotting these data on modified QFL diagrams suggests a magmatic arc provenance area. Clasts of unaltered quartz arenite were noted in several Santa Ynez samples. Upper Cretaceous conglomerates in the San Rafael block are higher in sedimentary clasts and have a lower proportion of quartzite clasts than those in the Santa Ynez block. This, plus the presence of quartz arenite clasts in the Santa Ynez block, suggests that the stratigraphic section in these two blocks was deposited by two different fan systems which coalesced from different provenance areas. Removal of approximately 90[degree] of clockwise rotation (as suggested by paleomagnetic declination data) and 70 km of right-lateral slip places themore » pre-Tertiary Western TR in a reconstructed position west of San Diego. Thus, the Penninsular Ranges Batholith and associated rocks would have provided the sediment to the Cretaceous fan systems. The northerly flow directions be reconstructed to a westerly flow direction, which matches flow directions measured in Cretaceous fan sequences currently exposed in the San Diego area. Thus, this model successfully accounts for the northerly-directed paleoflow direction measured in the Western TR, and the magmatic arc provenance indicated by the lithologic data.« less