A 1.1–1.2 km long, 3–15 m thick exposure of the late Miocene to Pliocene Capistrano Formation crops out at San Clemente, California, providing a superb example of submarine channel elements with an asymmetric cross-sectional facies distribution. Coarser-grained, thicker bedded and more amalgamated channel axial deposits are partitioned towards one side of channel elements (200–400 m wide), whilst finer-grained and thinner bedded channel margin deposits are partitioned towards the other side. Two end-member types of silty channel-base and intra-channel drapes are recognized, namely, bypass drapes and deposition drapes. There are both draping silty turbidites that show either strong (bypass drapes) or insignificant (deposition drapes) evidence of erosion and/or sediment bypass during deposition. Bypass drapes and deposition drapes are interpreted to result from flow bypass and flow stratification, respectively, and have significantly different implications for reservoir connectivity and down-dip sediment transport. Channel elements are nested to form two channel complexes. Channel complex 1 comprises four channel elements and shows a vertical aggradation dominated stacking pattern, whilst channel complex 2 comprises five channel elements and shows a mixed lateral migration/vertical aggradation stacking pattern. This study also suggests that these exposures represent only a fragment of a larger channel complex set that might bear varying degrees of resemblance to its formative geomorphic channel(s) on the paleo-seafloor. The reinterpretation of this classic outcrop provides valuable insight into other turbidite channel systems at outcrop and in the subsurface, both in a sedimentological and applied context.
Bibliographical noteThis work comprised part of the doctoral studies of PL and part of the Joint Industry Project, PRACSS, which was funded by BG Group, BP, DONG, RWE Dea, Petrochina, Statoil and Tullow Oil. PL also acknowledges the China Scholarship Council (CSC) for providing a stipend for his Ph.D. study in the UK. We are grateful to Guilherme Bozetti and Dugmar Isabel Mendez for their assistance in the field. We wish to thank Lana Nguyen, Dennis Weber, Christina Donehower and others from the state park for sample and work permission. We are also indebted to Christopher J. Stevenson, the anonymous reviewer and the editor Jasper Knight for their constructive and thoughtful reviews that improved the clarity and focus of manuscript considerably.
- Architectural asymmetry
- San Clemente
- Slope channels