Drakes Bay Sandstone

Shown here in red, the Drakes Bay Sandsone represents another major transgression of the sea on to a previously uplifted and eroded landmass. From the formation of the Monterey Formation the land was profoundly uplifted and eroded.

Galloway's Drakes Bay Sandstone (Tdbs)

Glauconitic sandstone overlain by finer grained rock, including glauconitic mudstone. Glauconitic sandstone is green where fresh, weathers rusty brown, and contains biotite, shale pebbles, and locally abundant bone material and carbonized wood; a thin conglomerate at the base near Pt Reyes contains large boulders of the underlying Paleocene conglomerate and granitic rock; finer grained upper part consists of light-colored, laminated shale and interbedded sandstone, white to tan siltstone and mudstone. Hard, chocolate brown, thin-bedded shale occurs locally between the two parts.


Up section to the Drakes Bay Shales