Bena Gravel
Bena Gravel
late to middle Miocene
A sequence of alluvial conglomerate, sandstone, and lesser siltstone and mudstone, partly interfingering with marine sandstone, cropping out along the margin of the southeastern San Joaquin Valley.
Nonmarine component consists predominantly of poorly sorted conglomerate of pebble- to cobble-size granitic clasts in a sandy matrix interbedded with massive coarse-grained arkosic sandstone (Bartow and McDougall, 1984; Chapman and Saleeby, 2012), which mostly represents a near-shore alluvial fan facies, that, in the lower part of the sequence, grades into a paralic facies. The marine strata consist of compositionally similar conglomerate and sandstone with interbedded laminated claystone and siltstone with rare oyster, barnacle, diatom, foraminifer, and marine mammalian fossils (Bartow and McDougall, 1984). 
Thickness ~950 m; age middle to late Miocene based on fossil assemblage (Bartow and McDougall, 1984). Includes the Chanac Formation.