Channel–Lobe Transition Zone Facies Architecture and Supercritical Bedforms, Point Loma Formation, San Diego, California, USA

Submarine-fan deposits are important archives of Earth’s history and serve as the record of turbidity current events that transfer substantial amounts of terrestrial sediment and carbon into the ocean. The geomorphology, depositional processes, and facies architecture change significantly along the submarine-fan depositional profile, particularly at the channel–lobe-transition zone (CLTZ). Recent modern-seafloor and flow-monitoring datasets showcase unprecedented complexity at the CLTZ, with upslope-migrating bedforms and erosional remnants related to bypassing flows. However, few outcrop-based studies have documented detailed CLTZ facies architecture and morphometrics of sedimentary structures that are important for reconstructing sediment transport dynamics and paleoenvironmental interpretations from ancient successions.

Excellent outcrop exposures from ancient CLTZ deposits of the Upper Cretaceous Point Loma Formation exposed at Sunset Cliffs, San Diego, California constrain the overall facies architecture, grain-size distribution, and three-dimensional geometry of sedimentary structures. The Point Loma Formation shows an abundance of supercritical bedforms exposed in three dimensions, enabling the mapping of key surfaces and facies trends significant for generating predictive models. The quantification of CLTZ deposits in this study enables a better understanding of the sediment transport dynamics and enhanced prediction of reservoir properties for comparable subsurface deposits that form hydrocarbon reservoirs and potential carbon dioxide storage.