Eustatic controls on stratification and facies associations in deep-water deposits, Great Valley sequence, Sacramento Valley, California
The Great Valley sequence consists of submarine fan deposits that are divided into laterally persistent sandstones and conglomerates separated by thick shaly intervals. The frequency of sandstone-shale successions in the Great Valley closely corresponds to the occurrence of major eustatic falls observed elsewhere in the world during the Upper Jurassic and Cretaceous. This close correspondence between the number of observed fans and sea level cycles has implications for the timing of fan development and facies models of deep-water deposits. On the basis of seismic expression, deep-water deposits from various basins have been divided by Mitchum into a sand-prone lower fan, which has a sharp basal contact, and a younger upper fan, which exhibits downlap onto and over the lower fan. Sand-prone members of the Great Valley (e.g., Venado and Forbes) are sharp-based, fining-upward units that have an aggradational or retrogradational stacking pattern of fan lobes. Massive sandstone, pebbly sandstone, conglomerate, pebbly mudstone, turbidites, and lenticular turbidites compose the fan lithologies. These rocks are typically referred to as inner fan channel or midfan lobes. In contrast, shale-dominated sections with thin-bedded turbidites (e.g., Boxer and Yolo) that have been variously described as basin plain, outer fan, inner fan levee, and slope correspond to the upper fan. Sharp basal fan contacts, textural contrasts between the lower and upper fans, and encasement of sand-prone fans in thick shaly sections indicate that fan development is an episodic rather than a continuous process. Rapid eustatic fall causing stream incision and shelf bypass is a likely mechanism for basin-wide and interbasinal fan development. Lithofacies encountered in fan deposits are related to grain size in the source area; specific lithologies in Great Valley fans (e.g., conglomerate) may be absent in other basins.
- Research Organization:
- Exxon Production Co., Houston, TX
- OSTI ID:
- 6107151
- Report Number(s):
- CONF-870606-
- Journal Information:
- AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States), Journal Name: AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States) Vol. 71:5; ISSN AABUD
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
020200* -- Petroleum-- Reserves
Geology
& Exploration
CALIFORNIA
CONGLOMERATES
CRETACEOUS PERIOD
FEDERAL REGION IX
GEOLOGIC AGES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
GEOLOGY
JURASSIC PERIOD
MESOZOIC ERA
NORTH AMERICA
ROCKS
SANDSTONES
SEDIMENTARY BASINS
SEDIMENTARY ROCKS
SHALES
SILTSTONES
STRATIGRAPHY
USA