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Map showing publication footprint
  • Usage in publication:
    • Drakes Bay Formation
  • Modifications:
    • Named
  • Dominant lithology:
    • Sand
    • Siltstone
    • Mudstone
  • AAPG geologic province:
    • California Coast Ranges province
Publication:

Galloway, A.J., 1977, Geology of the Point Reyes Peninsula, Marin County, California: California Division of Mines and Geology Bulletin, no. 202, 72 p., (incl. geologic map, scale 1:48,000)


Summary:

Named for Drakes Bay. Type section: Drakes Bay sea cliff extending from Drakes Estero [southwest about 6 km] to granitic outcrop at east end of Point Reyes ridge, Marin Co, CA. Consists of brilliant green to gray-green, glauconitic-bearing greensand, chocolate brown shale, and overlying brown, cream and white siltstone and mudstone. Occupies syncline west of San Andreas fault zone. Is 260 m thick with range from one to less than 490 m. Top is eroded. Unconformably overlies granitic basement rocks, Point Reyes Conglomerate, or Monterey Shale; unconformably underlies Quaternary sediments. Age is late Miocene or early Pliocene.

Source: GNU records (USGS DDS-6; Menlo GNULEX).


Map showing publication footprint
  • Usage in publication:
    • Drakes Bay Formation
  • Modifications:
    • Not used
  • AAPG geologic province:
    • California Coast Ranges province
Publication:

Clark, J.G., Brabb, E.E., Greene, H.G., and Ross, D.C., 1984, Geology of Point Reyes Peninsula and implications for San Gregorio history, IN Crouch, J.K., and Bachman, S.B., eds., Tectonics and sedimentation along the California margin: Society of Economic Paleontologists and Mineralogists, Pacific Section, Field Trip Guidebook, annual meeting, San Diego, CA, April 18-21, 1984, book 38, p. 67-85.


Summary:

Drakes Bay Formation of Galloway (1977) replaced by Santa Margarita Sandstone, Santa Cruz Mudstone, and Purisima Formation. This replacement is result of geographic extension of these units into Point Reyes area, along San Gregorio fault based on very similar stratigraphic relationships, lithologies, and fossils.

Source: GNU records (USGS DDS-6; Menlo GNULEX).


For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.

Asterisk (*) indicates published by U.S. Geological Survey authors.

"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).

Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).

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