Like the Laird/Monterey sequence, the Drakes Bay Sandstone and Drakes Bay Formation represent a rise of sealevel (sinking of land?) and the development of what geologist call a transgressive sequence.
Galloway's Drakes Bay Formation (Tdbc)
White to brown-weathering siltstone and gray-to yellowish gray weathering silty mudstone, with local beds of brown to gray, fine-grained sandstone; largely unbedded to poorly bedded; contains large, rounded calcareous concretions; lacks hard, siliceous shale and thin rhythmic bedding of the Monterey Formation (Tm)
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