Abstract: Sedimentology of Fluvial to Bathyal Sandstones of Cretaceous Great Valley Sequence, California

R. W. Tillman, R. H. Groshong, Jr.

Detailed concurrent analyses of sedimentary structures, vertical sequence, population-derived grain-size data, and petrography allow genetic interpretations of continental-margin sandstones of the Great Valley sequence of California. Seven environments have been recognized: fluvial, lower foreshore, proximal fan channel, fan channel, fan lobe, interlobe and/or interchannel, and outer fan-basin plain deposits.

In the Chico Formation of the east side of the Sacramento Valley, a prograding sequence of sandstones was deposited in association with a narrow shelf. From base to top, proximal fan-channel deposits are followed by thick sequences of lower foreshore sandstones and fluvial or distributary-channel sandstones. On the west side of the valley, fan channels, fan lobes, and interchannel and interlobe environments make up thick sections of the Venado and Sites Formations.

North-south trending and east-west elongate fans dominated deposition at various times. During periods of rapid sand deposition, different areas provided the source for different units within the sequence in a manner similar to that suggested by Ricci-Luchi for the Apennines in Italy. Within the previously defined petro-facies, additional framework variations may be attributed to variations in processes of deposition and local source-area contributions. Sandstone outliers west of the Great Valley sequence are demonstrated to be part of the sequence.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC