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Abstract: The Rocks Sandstone Member, Reliz Canyon Formation, Northern Santa Lucia Range, California: Internal Facies Architecture of a Sand-Rich, Deep-Sea Depositional System

MASON, ELIZABETH L., Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305

The Eocene Rocks Sandstone Member of the Reliz Canyon Formation of the northern Santa Lucia basin, California, is an excellent candidate for an outcrop-based, internal architecture study of an ancient sand-rich turbidite system. This deep-sea, thick-bedded, highdensity, sediment gravity flow deposit is exceptionally well-exposed and laterally continuous for more than 6 km at its type locality in Reliz Canyon, making it an valuable analog for understanding similar petroliferous subsurface systems. This study characterizes the Reliz Canyon outcrop in detail focusing on documentation of the lateral and vertical heterogeneities of the internal architecture using a hierarchical classification scheme to characterize submarine fan systems based on major lithologic and depositional elements. The characterization also serves as a data base for creation of a synthetic seismic profile of the outcrop.

Documentation of the outcrop consists of measured sections and mapping of bedding surfaces and sedimentary structures on photomosaics taken from helicopter overflights. The type section of The Rocks Sandstone is best suited to correlation of third-order architectural elements which consist of groups of similar sedimentation units that were deposited by individual flows. Three distinct third-order elements can be identified in The Rocks Sandstone and correlated across the length of the outcrop. The lowermost third-order element consists of laterally continuous, tabular, non-erosive, upward-fining sequences. The upper two elements are coarser-grained, erosive, channelized sequences that can be distinguished by the presence of finer-grained, planar-laminated to rippled sequences in the uppermost element that are absent in the middle element. The system evolved from a non-erosive, lower energy depositional environment to a channelized, higher energy depositional environment. The section is interpreted to represent a prograding system where relatively more distal, unconfined facies grade upward to more confined, proximal facies.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah