Title: Fluvial facies of the miocene ridge route formation, Ridge Basin, California
Abstract: The upper Miocene nonmarine Ridge Route Formation consists of more than 9000 m of fluvial rocks deposited along the northeast margin of Ridge Basin, California. Five major fluvial tongues of the Ridge Route Formation cross the basin to interfinger with the Violin Breccia on the southwest. Two styles of fluvial sedimentation are inferred: (1) deposition in small braided channels on fan deltas resulting from streamflow and sheet-flood processes on the northeast side of the basin; and (2) deposition on large meandering-channel complexes in the lower parts of fan deltas and in elongate deltas which formed by point-bar accretion and overbank flooding near the center of the basin. These fluvial strata are composed of crossbedded and laminated sandstone interbedded with mudstone. The braided-channel deposits have a high sandstone-mudstone ratio (10:1), and contain lenticular beds averaging 1 m thick and 20 m long. These channels are small and of low relief (< 1 m deep). The meandering-channel deposits have a lower sandstone-mudstone ratio (2:1), occur in thinning- and fining-upward sequences up to 60 m thick, and are associated with extensive interchannel deposits. These channels are large (up to 1 km long) with moderate relief (< 3 m deep). Paleocurrents indicate that the braided- and meandering-fluvial deposits were derived from the northeast and the meandering-stream deposits have a component of transport down the axis of the basin to the south and southeast. The change from braided to meandering deposits and in paleocurrent directions suggests changes in gradient and hydraulic regime resulting from lake level and shoreline position fluctuations, which is related to tectonics and rates of sedimentation.
Publication Year: 1984
Publication Date: 1984-03-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 13
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