- Usage in publication:
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- Whiterock Bluff shale member
- Modifications:
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- Named
- Biostratigraphic dating
- Dominant lithology:
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- Shale
- Sandstone
- AAPG geologic province:
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- California Coast Ranges province
- Transverse Ranges province
Summary:
Named from Whiterock Bluff on north side of Cuyama Valley, San Luis Obispo Ca, CA, as middle member (of 3) of Santa Margarita formation. Occurs in Caliente Range, western Cuyama Valley and in Salisbury Canyon area. Near Whiterock Bluff consists of not less than 1500 ft of white "chalky" diatomaceous shale where it unconformably(?) overlies Monterey group and underlies Morales member (new) of Santa Margarita formation. On south side of Cuyama Valley unit consists of interbedded white clay shale, diatomaceous shale and sandstone (2000 to 2500 ft thick) where it gradationally overlies Maricopa shale (new). At Redrock Canyon unit overlies Redrock Canyon shale member (new) of Santa Margarita formation. Map legend gives age as Miocene. List of megafossils included.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
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- Whiterock Bluff shale member*
- Modifications:
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- Revised
- Biostratigraphic dating
- AAPG geologic province:
-
- California Coast Ranges province
Summary:
Whiterock Bluff shale member of Santa Margarita formation of English (1916) is removed from Santa Margarita and assigned as uppermost member of Monterey shale. Type area designated as exposures at Whiterock Bluff, sec.25 T11N R28W, Caliente Mountain 15' quad, San Luis Obispo Co, CA. Is 1200 ft thick at type. Conformably overlies Saltos shale member (new) of Monterey shale. Conformably underlies Santa Margarita formation. Grades southeastward into upper part of Branch Canyon sandstone formation (new). Age is middle Miocene (Luisian and Relizian Stages) based on microfaunal content in upper 720 ft of unit at Whiterock Bluff. Microfossils listed.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
-
- Whiterock Bluff Shale Member*
- Modifications:
-
- Revised
- Areal extent
- AAPG geologic province:
-
- California Coast Ranges province
Summary:
Whiterock Bluff Shale Member of Monterey Shale as defined by Hill and others (1958) is adopted. Unit is widely distributed in Caliente Range, La Panza Range, Sierra Madre Mountain, and in subsurface in Salinas Valley. Exposure of Whiterock Bluff Shale Member in sec.21 T28S R14E, 12 mi east of Atascadero is type locality of Luisian Stage as defined by Kleinpell (1938). Age is middle Miocene based on foraminifers.
Source: GNU records (USGS DDS-6; Menlo GNULEX).
- Usage in publication:
-
- Whiterock Bluff Shale Member*
- Modifications:
-
- Geochronologic dating
- AAPG geologic province:
-
- California Coast Ranges province
Summary:
Age of Whiterock Bluff Shale Member of Monterey Shale is around 15 to 14 Ma within context that uppermost part of unit is of early Mohnian age and the upper "Triple" basalt flow of Monterey Shale can be projected into this level (Vedder, 1973 and oral commun., 1981). [Study correlates radiometric ages with Pacific-Coast foraminiferal and North American land mammal stages.]
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 ([ ]).