Depositional Facies of High-Energy Beach-to-Offshore Sequence: Comparison with Low-Energy Sequence

Abstract

Abstract A study of the nearshore zone and continental shelf of a high-energy coast was made in the Ventura-Port Hueneme area of California during the summer of 1974 to investigate depositional facies characteristics and compare them with similar facies from a low-energy coastal setting. Analysis of box cores, can cores, and vibracores permits recognition of three principal zones: (1) nearshore facies (backshore to 9 m water depth), made up primarily of parallel, ripple, and cross-bedded clean sand; bioturbation is only locally significant; (2) transition facies (9 to 18 m water depth), a zone of fine sand and silty sand, characterized by an increase in biogenic over physical sedimentary structures that are commonly preserved as laminated-to-burrowed beds; wave-ripple bedding and parallel lamination are important structures in this facies; (3) offshore facies (> 18 m water depth), sandy silt is the primary texture and bioturbation is the dominant sedimentary structure; remnant parallel lamination is the only physical sedimentary structure present. Comparison of the results of this study with a previous description of a low-energy beach-to-offshore sequence at Sapelo Island, Georgia, indicates that the two areas do not differ greatly in their facies or overall vertical sequence of sedimentary structures. The principal difference is in the thickness of the three facies: the California facies are significantly thicker than their Georgia counterparts. This difference is in direct response to the role of higher wave energy on the California coast.