--> ABSTRACT: Architecture and Internal Heterogeneity in Deep-Sea Sediment Gravity Flow Deposits from the Turonian Venado Sandstone, Sacramento Valley, California, by Bibek Ghosh; #91020 (1995).

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Architecture and Internal Heterogeneity in Deep-Sea Sediment Gravity Flow Deposits from the Turonian Venado Sandstone, Sacramento Valley, California

Bibek Ghosh

Deep-water sedimentary sequences are subdivided based on sedimentology and/or lithofacies, commonly interpreted in terms of submarine fan facies models. A more objective scheme is based on a hierarchy of lithologic architectural elements, similar to that widely used in the analysis of fluvial systems. Interpretation of these architectural elements would help in reconstructing the depositional history of a deep-sea deposit without resorting to any rigid classification scheme. Such an approach also provides a basis for better understanding and predicting reservoir properties in sand-rich deep-sea deposits at several architectural levels.

In the Turonian Venado Sandstone, Sacramento Valley, California, five principal architectural elements have been recognized, throughout an long outcrop belt 100 km long. First-order units include the individual divisions of the Bouma sequence (Ta-Te) and individual divisions of high-density turbidity-current deposits (S1-3; R1-3). Sedimentation units deposited by individual flows constitute second-order elements. Sequences of lithologically similar sedimentation units make up third-order elements. Cyclic associations of contrasting third-order units, such as alternating thick-bedded sandstone and thin-bedded sandstone-mudstone packages, constitute fourth-order elements. Several fourth-order elements make u the formation-scale fifth-order architectural element.

Different scales of correlatibility and heterogeneity are observed within the different orders of architectural elements. Thin-bedded turbidite sedimentation units can commonly be correlated over distances of 24 Km. Individual second-order thick-bedded turbidites commonly show evidence of scours and amalgamation and are generally less continuous laterally than thin-bedded units. Third- and fourth-order units are traceable for distances exceeding 10 km. The entire Venado Sandstone Member, a fifth-order unit, extends for over 160 km.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995