Miocene gastropods and biostratigraphy of the Kern River area, California

Abstract

Miocene strata were first recognized in California on the basis of molluSl\S collected from the Kern River area in the southern part of the San .Ton(]uin Valley by William Blake during the Pacific Railroad surveys of more than 100 years ago. Description of the gastropod-rich Barker's Ranch fauna from exposures along Kern River nort.heast of Bakersfield by later workers led to the use of this fauna as the standard for middle Miocene correlation on the Pacific coast.Marine formations of early and middle Miocene age are exposed in the Kern River area. Faunal assemblages from the subsurface Vedder Sand of this area and from exposures of the overlying Jewett Sand are referred to the "Vaqueros Stage," the early Miocene part of the Pacific coast megainvertebrate chronology of Weaver and others (HJ44). A few long-ranging molluslcs occur in the overlying Freeman Silt. Foraminifera from this formation are indicative of an early Miocene age. Mollusks from the Olcese Sand and the overlying Round Mountain Silt form the faunal l.>asis for recognition of the "Temblor Stage," a unit long regarded as the middle Miocene provincial megafaunal standard. i'llolluslcs of late Mio~ene age are not known to occur in surface exposures in the Kern River area, although several assemblages have l.>een reported from well cores of the Santa Margarita Formation in oil-field areas a few miles west of the lower and middle Miocene exposures.Formational nomenclature for the Miocene sequence was originated during early exploratory and development drilling for petroleum in the Round Mountain-Mount Poso area, principally from subsurface data. Most of these units, though locally applicable in surface mapping, have not been adequately defined. Accordingly, formal description and review of the Miocene formations is undertaken to facilitate biostratigraphic characterization of the Miocene sequence.The fauna of the lower part of the .Jewett Sand, the lowest exposed• marine formation in the Kern River area, includes 46 gastropod taxa, many of which are newly described herein. Almost half of these taxa do not occur higher in the local section. In most of the upper part of the formation, mollusks are widely scattered, but tl.1ere are a few oyster biostromes near the top which contain Ostrea eldridgei yneziana and scattered Ohlam118 h01•tleini., a pectinid restricted to the "Vaqueros Stage." Important "Vaqueros" index species in the Jewett Sand include the gastropods T1tn•itella inezana, Ocenebra milicentana, and l1Jpitoni1tm clallamense and the pelecypods Lyropecten magnolia and Ostrea vaq1terosensis. Cores of the overlying Freeman Silt contain an assemblage characterized by the small pelecypods Acila conrad,i, 01}clocard,la 81tbtenta, and Nuculana ochsneri. Also occurring with this assemblage is the gastropod Priscotusus rnedi.alis, which seems to be restricted to the Jewett Sand and Freeman Silt. The small subsurface molluscan assemblages from the Freeman Silt are not diagnostic of position in the provincial megaitwertebrate sequence, but indirect evidence ...

Molecular Phylogenetics and The Evolution of Labral Spines among Eastern Pacific Ocenebrine Gastropods

“…cf. C. perponderosum (Dall, 1909) from the Jewett Sand (earliest Miocene: Aquitanian) of California (see Addicott, 1970), Ceratostoma may have originated in the Atlantic basin (Amano and Vermeij, 1998).…”

New observations on the Middle Fork Eel River coal-bearing beds, Mendocino County, California, USA

“…The family Turridae is represented by the genus Turricula. Though questionable, some specimens from the SBb closely resemble T. piercei (Arnold), a middle Miocene species reported from the Olcese Sand (Addicott, 1970), Round Mountain Silt (Addicott, 1970), Temblor (Anderson and Martin, 1914;Loel and Corey, 1932;Woodring et al, 1940), and "Vaqueros" (Arnold, 1909;Arnold and Anderson, 1910) Formations of California.…”

“…Cerithidae appears to be represented by several small turriform shells that closely resemble "Bittium" topangensis (Arnold) in having prominently raised, rounded, radial ribs, but on the SBb specimens they are inclined slightly to the left from the top to bottom of a whorl and show faint concentric ribs that may form cancellate sculpture on the radial ribs of some specimens. "Bittium" topangensis (Arnold) has been previously reported from the lower to upper Miocene of Central and Southern California (Addicott, 1970), but differs from the SBb specimens in having inclined rather than vertically oriented radial ribs. Typically, species of Bittium s.s. do not have strong radial ribs leaving open the possibility that "Bittium" topangensis and the Salt Creek "Bittium" material may be new taxa.…”

The genusAntillophosWoodring, 1928 (Gastropoda: Buccinidae) from the China seas, with description of a new species

“…This assignment was accepted by subsequent authors (e.g., Olsson 1964;Addicott 1970). Fraussen and Poppe (2005) revised the species of Antillophos from Philippines and gave this genus a diagnosis: 'the Antillophos is characterized by the presence of (a) strong abapical columellar fold(s), and by the protoconch with 1 or more strong spirals in combination with a few strong, curved axial riblets near the transition to teleoconch'.…”