San Nicholas Island (21649) (Eocene to of the United States)

Also known as USGS 21649

Where: Ventura County, California (33.2° N, 119.5° W: paleocoordinates 33.0° N, 107.1° W)

• coordinate stated in text

• outcrop-level geographic resolution

When: Unnamed Formation, Middle Eocene to Middle Eocene (48.6 - 33.9 Ma)

• 3,500 feet of alternating marine sandstone and siltstone beds that contain minor amounts of interbedded conglomerate and pebbly mudstone. Is divided into 35 mapping units in Vedder and Norris (1963) but thestratigraphic location of the fossil collections are not indicated. Small andesite dikes of Miocene age intrude the Eocene strata. Dune sand and fossiliferous marine terrace deposits of Quaternary age overlie most of the Eocene strata. Bulk of the specific identifications suggest a middle to late Eocene age based on forms conspecific with those found in the Domengine Formation, the upper part of the Llajas Formation, the Rose Canyon shale member of the La Jolla Formation, and the Tejon Formation, all of whihc are considered to be in the upper half of the Eocene in Calfornia

• bed-level stratigraphic resolution

Environment/lithology: coastal; gray, conglomeratic mudstone and medium-grained, gray, conglomeratic sandstone

• Structurally, San Nicholas Island is a broad, complexly faulted anticline that roughly parallels the long dimension of the island. Age of the main faulting is assumed to be pre-middle Miocene with continuing movement through Pleistocene time.
• Conglomeratic mudstone and sandstone sequence. Matrix ranges from mudstone to poorly sorted medium-grained sandstone that is olive-gray in fresh exposures and locally contains large angular fragments of sandstone and siltstone.

Size class: macrofossils

Reposited in the USGS

Collection methods: quarrying,

• Collected by Vedder et al. (1955, 1956). Earlier collections by Bowers (1890), Harbor and Reed (1933).

Primary reference: J. G. Vedder and R. M. Norris. 1963. Geology of San Nicolas Island, California. United States Geological Survey Professional Paper 369:1-65 [A. Miller/A. Hendy/P. Wagner]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 37928: authorized by Austin Hendy, entered by Austin Hendy on 27.03.2004

Creative Commons license: CC BY (attribution)

Taxonomic list

• Representative for mollusca, coral mentioned in text, but not listed.
 Ostreida - Gryphaeidae
"Ostrea aff. stewarti" = Pycnodonte (Crenostrea) stewarti
"Ostrea aff. stewarti" = Pycnodonte (Crenostrea) stewarti Hanna 1927 oyster
 Architaenioglossa - Ampullinidae
"Amaurellina clarki" = Pachycrommium clarki Stewart 1927 snail
 Neogastropoda - Olivellidae
 Neogastropoda - Buccinidae
 Neogastropoda - Fasciolariidae
 Neogastropoda - Volutidae
""Volutocristata" cf. lajollaensis" = Lyrischapa, Lyria aff. andersoni
""Volutocristata" cf. lajollaensis" = Lyrischapa volute
Lyria aff. andersoni Waring 1917 volute
 Neogastropoda - Turridae
""Surcula" cf. praeattenuata" = Turricula turrid
 Neogastropoda - Conidae
 Naticoidea - Naticidae
Euspira cf. nuciformis Gabb 1864 moon snail
Neverita cf. secta Gabb 1864 moon snail
 Sorbeoconcha - Potamididae
 Sorbeoconcha - Turritellidae
Turritella lawsoni turret shell
Turritella uvasana Conrad 1865 turret shell
Subspecies: Turritella uvasana etheringtoni
Turritella cf. uvasana Conrad 1865 turret shell
Subspecies: Turritella uvasana hendoni
 Architectonicoidea - Architectonicidae
Architectonica cf. ullreyana, "Architectonica cf. cognata" = Stellaxis cognata
"Architectonica cf. cognata" = Stellaxis cognata Gabb 1864 sundial
 Dentaliida - Dentaliidae
Dentalium cooperi Gabb 1864 tusk shell