--> Abstract: Paleogeography of Three Paleocene Limestones, Baja California, Mexico, by P. L. Abbott, D. P. Smith, W. V. Sliter, and L. R. Saul; #90958 (1995).

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Abstract: Paleogeography of Three Paleocene Limestones, Baja California, Mexico

Patrick L. Abbott, Douglas P. Smith, William V. Sliter, Louella R. Saul

Three limestone localities in Baja California span three degrees of latitude (27-30° N). Combined foraminiferal, macrofossil and nannofossil data place the rocks in late early to late Paleocene time. The rocks provide data points constraining late early to late Paleocene shoreline positions along several hundred kilometers of Baja California. The limestones are time equivalent with older portions of the Sierra Blanca Limestone in the Transverse and Coast Ranges of California. The rarity of limestone in the Cenozoic record of California and Baja California makes each new locality description potentially quite important in defining paleogeography, paleoclimatology and tectonics.

At Mesa de La Sepultura (30° N), conglomerate with abundant Turritella peninsularis is overlain by glauconitic, red algal arkose, passing upward to pure limestone -- sorted, forum-red algal biosparrudite -- deposited in increasingly deep water on a shelf isolated from terrigenous sediments during late Paleocene time. At Punta Maria (29° N), a red-algal mound over three km wide interfingers with volcanic litharenites. At Los Cuervitos (27° N), Paleocene slope talus contains limestone gravels bearing T. peninsularis that were derived from an adjacent shallow-marine environment. Overlying the slope deposits are incised beds of cross-bedded, well-washed, glauconitic, Venericardia and T. peninsularis-rich biosparrudite deposited in a tidal channel system. The upper lower to pper Paleocene limestones in Baja California show warm, shallow-marine conditions apparently adjacent to active faulting that created slopes and isolated shelf platforms.

AAPG Search and Discovery Article #90958©1995 AAPG Pacific Section Meeting, San Francisco, California