assignments can be evaluated by comparison with radiochemical age assignments and late Pleistocene temperature histories inferred from one or more paleoclimatic records. The kinetic model ages can also be evaluated within the constraints of both eustatic sea-level and isotopic ice-volume records. Age assignments for many of the late Pleistocene localities investigated in this work are in the range of 100,000 to 140,000 years and these localities are correlated with the early part of Stage 5 of the marine isotopic record (Shackleton and Opdyke, 1973). These age assignments are, in all cases, consistent with the radiometric age assignments for" the calibration localities. Samples from high terraces on San Nicolas Island, Palos Verdes Hills, and San Joaquin Hills, and from the San Pedro Sand have kinetic model ages of between 350,000 and 550,000 years and appear correlative with all or part of Stages 9 and II of the marine isotopic record. Three low terrace localities in southern California have yielded samples with ages in the range 200,000 to 250,000 years (correlative with Stage 7 of the marine isotopic record), though previous interpretations of these localities had implied correlation with localities that are sho~~to be younger. Some of these older samples may have been reworked into younger deposits. Localities with late Stage 5 (80,000 to 100,000 yrs.) ages are found at Santa Cruz, California and on Point Loma, San Diego, California (the Bird Rock Terrace). Both radiometric and geologic information are consistent with these age assignments. Samples from Cape Blanco, Oregon, appear to be either lateor post-Stage 5 in age; samples from Goleta, California are definitely post-Stage 5 in age, and appear to be approximately 40,000 years in age. iii Several of these age assignments permit revisions in the interpretation of pre-existing paleoecologic data. In addition, long-term average uplift rates for each dated locality can be estimated: most of the Stage 5 localities reported herein have apparent uplift rates between .1 and .3 meters/lOOO yrs. Uplift rates of .15 to .75 meters/IOOO yrs. are inferred from the results for San Nicolas Island and the Palos Verdes Hills. Quite. rapid uplift rates of 1.5 to 2.75 meters/IOOO yrs. for Goleta and Cape Blanco are also inferred from our results.

Thls report is preliminary and hae not been edited o r reviewed for conformity with Geological Survey standards and nomenclature.

No 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 ...

No abstract