--> Abstract: Diagenesis in Fine-Grained Arkosic Wackes of the Temblor Formation (Miocene), North Belridge Oil Field, California, by D. Hanson and R. A. Horton, Jr.; #90935 (1998).

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Abstract: Diagenesis in Fine-Grained Arkosic Wackes of the Temblor Formation (Miocene), North Belridge Oil Field, California

HANSON, DAWN, and ROBERT A. HORTON, JR., Dept. Geology, California State University, Bakersfield, CA 93311

Lithic-rich arkosic wackes of the Temblor Formation at North Belridge oil field consist of well sorted fine to very fine sand in poorly sorted matrix dominated by illite/smectite. Lithic grains are dominantly volcanic with a few metamorphics. A few phosphate and glauconite grains are present as well as some calcareous fossils. Distribution and texture of the matrix suggests that it is actually pseudomatrix derived from alteration of volcanic lithics; most likely the sands originally were well sorted lithic arenites. Diagenetic pyrite is common in the pseudomatrix. Carbonates occur as minor pore-filling cement and replace feldspars and quartz. Susceptibility to replacement by carbonates was greatest for plagioclase and least for quartz. Feldspars are commonly altered to kaolinite and kaolinite also occurs as pore-filling cement. Feldspars also have been albitized. Zeolites have replaced volcanic lithics in some samples. Dissolution has affected most framework grains (except phosphate and glauconite which show little diagenetic alteration) but predominantly affected feldspars with plagioclase more susceptible than K-feldspars. Mass balance calculations suggest that Aluminum liberated during feldspar diagenesis was transported out of some samples and imported into others; however no large- scale movement of aluminum into or out of the sands is indicated.

AAPG Search and Discovery Article #90935©1998 AAPG Pacific Section Meeting, Ventura, California