--> --> Impact of local accommodation on the architecture and stacking patterns of three Capistrano Formation slope-channel outcrops: Point Fermin, Dana Point, and San Clemente, California

AAPG Pacific Section and Rocky Mountain Section Joint Meeting

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Impact of local accommodation on the architecture and stacking patterns of three Capistrano Formation slope-channel outcrops: Point Fermin, Dana Point, and San Clemente, California

Abstract

The stratigraphy of deep-water reservoirs is partially related to local accommodation at the time of deposition. Three outcrops of the upper Miocene-Pliocene (‘Delmontian’ stage) Capistrano Formation provide the opportunity to document contrasting channelized slope depositional systems and the effects of local accommodation on slope-channel architecture and stacking patterns. Stratigraphic columns, paleocurrent, photomosaic and LIDAR data were collected to address the stratigraphy and evolution of each depositional system. The three slope-channel systems studied are incised into slope mudstone of the middle to upper Miocene Monterey Formation. The three channel systems contain similar lithofacies types although their proportions and distributions vary by location. The architectural elements are also similar at each exposure but vary in their dimensions, geometries, and stacking patterns. The Point Fermin exposure contains a 45-m-thick, 500-m-wide half graben syn-depositionally filled with Capistrano channel deposits. These deposits represent a proximal slope setting with poorly confined sedimentation from a nearby uplift (within 2 kilometers). The strata vary, both upward and laterally toward the steep side of the half-graben, from mass-transport-complex-dominated to channel-dominated. This architecture reflects high differential accommodation that varies laterally. The Dana Point Harbor exposure contains a 30-m-thick, 900-m-wide, conduit-filling channel complex set, formed by three laterally accreting and two vertically stacking channel complexes. The accommodation is low to moderate, influenced by laterally variable internal basal channel cut topography and is locally impacted by sand volcanoes formed at the base of the early channel complex cut. The conduit which confines the Capistrano Formation at Dana Point was cut into upper slope mudstones and fed sediments from 7 to 25 kilometers to the east. The San Clemente exposure contains a 20-m-thick, 500-m-wide, mainly laterally accreting, meandering slope channel complex composed of ten non-amalgamated and amalgamated channel deposits. The amount of confinement and stacking patterns indicate a low accommodation at the time of deposition. The lower slope channel complex at San Clemente was fed sediments from the Peninsular Ranges 10 to 30 kilometers to the east.