Abstract: Paleographic Implications of Shallow Water Limestones in the Southern San Rafael Mountains, California
Katherine J. Whidden, D. J. Bottjer, S. P. Lund, W. V. Sliter
Spatially isolated limestone outcrops are found in the western Transverse Ranges and southern San Rafael Mountains. This region represents part of a distal fore-arc basin/accretionary prism, preserved as the Sur-Obispo terrane. At least two time intervals of limestone deposition can be recognized, one in the late Paleocene (P4) and one in the early middle Eocene (P9/P10). Most of the preserved
limestones consist of shallow water (photic zone) material redeposited at bathyal depths. Several distinct carbonate highs can be recognized that shed material into the surrounding fore-arc basin. In one locality, lagoonal lithoclasts redeposited at bathyal depths suggest a relative lowstand that resulted in exposure of the carbonate platform, lithification, erosion, and redeposition. The lack of such clasts in other localities suggests that the relative lowstand was localized, and thus tectonically controlled.
These topographic highs are interpreted to represent structurally controlled uplifts based on the following evidence: limestones were deposited on tilted, eroded Cretaceous fore-arc strata or exposed Franciscan Assemblage, and bathyal shale deposition was concurrent with carbonate accumulation and redeposition, implying steep topographic changes. Thrusting may have caused these localized uplifts in the accretionary prism and distal fore arc, based on previously mapped relationships of the Cretaceous and Paleogene strata.
AAPG Search and Discovery Article #90981©1994 AAPG Pacific Section Meeting, Ventura, California, April 27-29, 1994