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P. C. Bateman

Publications and source records attributed to P. C. Bateman.

At least 19 recordsLinked to original sources
USGS2012

Magnetic susceptibility and relation to initial 87Sr/86Sr for granitoids of the central Sierra Nevada, California

Measurement of the magnetic susceptibility of more than 6000 samples of granitic rock from the Mariposa 1° by 2° quadrangle, which crosses the central part of the Sierra Nevada batholith between 37° and 38°N latitude, shows that magnetic susceptibility values are above 10 −2 SI units in the east and central parts of the batholith and drop abruptly to less than 10 −3 SI units in the western foothills. In a narrow transitional zone, intermediate values (10 −3 to 10 −2 ) prevail. Magnetic susceptibility appears to decrease slightly westward within the zones of both high and low values. Magnetic susceptibility in plutonic rocks is chiefly a function of the abundance of magnetite, which depends, in turn, on the total iron content of the rocks and their oxidation ratio. Lower magnetic susceptibilities of felsic members of Sierran intrusive suites and of some felsic rock units relative to adjacent mafic rock units commonly reflect differences in total iron content, but the differences of magnetic susceptibility that define the regional pattern generally are much larger and are determined chiefly by the oxidation ratios of the rocks. The relatively unaltered condition of the samples and restriction of δ 18 O to the range of +7 to +10.3‰ indicate that neither hydrothermal fluids nor subsolidus alteration were important in modifying oxidation ratios. Correlations of magnetic susceptibility with initial 87 Sr/ 86 Sr suggest that oxidation ratios have been inherited from the source regions for the magmas from which the rocks crystallized. Reduction of Fe 3+ to Fe 2+ by organic carbon or other reducing substances may also have affected magnetic susceptibility.

Journal of Geophysical Research↗
USGS1989

Geologic map of Yosemite National Park and vicinity, California

This digital map database represents the general distribution of bedrock and surficial deposits of the Yosemite National Park vicinity. It was produced directly from the file used to create the print version in 1989. The Yosemite National Park region is comprised of portions of 15 7.5 minute quadrangles. The original publication of the map in 1989 included the map, described map units and provided correlations, as well as a geologic summary and references, all on the same sheet. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution (scale) of the database to 1:125,000 or smaller.

IMAP↗
USGS1986

Isotopic variation in the Tuolumne Intrusive Suite, central Sierra Nevada, California

Granitoid rocks of the compositionally zoned Late Cretaceous Toulumne Intrusive Suite in the central Sierra Nevada, California, have initial87Sr/86Sr values (Sri) and143Nd/144Nd values (Ndi) that vary from 0.7057 to 0.7067 and from 0.51239 to 0.51211 respectively. The observed variation of both Sri and Ndi and of chemical composition in rocks of the suite cannot be due to crystal fractionation of magma solely under closed system conditons. The largest variation in chemistry, Ndi, and Sri is present in the outer-most equigranular units of the Tuolumne Intrusive Suite. Sri varies positively with SiO2, Na2O, K2O, and Rb concentrations, and negatively with Ndi, Al2O3, Fe2O3, MgO, FeO, CaO, MnO, P2O5, TiO2, and Sr concentrations. This covariation of Sri, Ndi and chemistry can be modeled by a process of simple mixing of basaltic and granitic magmas having weight percent SiO2 of 48.0 and 73.3 respectively. Isotopic characteristic of the mafic magma are Sri=0.7047, Ndi=0.51269 and ??18O=6.0, and of the felsic magma are Sri=0.7068, Ndi=0.51212 and ??18O=8.9. The rocks sampled contain from 50 to 80% of the felsic component. An aplite in the outer equigranular unit of the Tuolumne Intrusive Suite apparently was derived by fractional crystallization of plagioclase and hornblende from magma with granudiorite composition that was a product of mixing of the magmas described above. Siliceous magmas derived from the lower crust, having a maximum of 15 percent mantle-derived mafic component, are represented by the inner prophyritic units of the Tuolumne Intrusive Suite. ?? 1986 Springer-Verlag.

Contributions to Mineralogy and Petrology↗
USGS1985

Calaveras reversed: Westward younging is indicated

Samples of limestone collected from strata in the southern part of the western metamorphic belt of the Sierra Nevada, which traditionally have been assigned to the Calaveras Formation, have yielded Early Triassic conodonts, and samples of metavolcanic rock indicate an Early Jurassic Rb-Sr age. These ages, together with previously published fossil and isotopic data, are consistent with general westward younging of units rather than with eastward younging as has been assumed until recently by many workers, chiefly on the basis of sparse observations of bedding facings. The rocks are strongly deformed, and the possibility that tectonism rather than stratigraphic succession accounts for the age pattern cannot be dismissed.

Geology↗
USGS1984

Courtright intrusive zone: Sierra National Forest, Fresno County, California.

This is a field guide to a well-exposed area of plutonic and metamorphic rocks in the Sierra National Forest, Fresno County, California. The plutonic rocks, of which three major bodies are recognized, besides aplite and pegmatite dykes, range 103 to approx 90 m.y. in age. Points emphasized include cataclastic features within the plutonic rocks, schlieren and mafic inclusions. (M.A. 83M/0035).-A.P.

California Geology↗
USGS1973

Fusion Relations in the System NaAlSi3O8-CaAl2Si2O8-KAlSi3O8-SiO2-H2O and Generation of Granitic Magmas in the Sierra Nevada Batholith

Chemical analyses of 167 typical specimens indicate that about 95 percent of the intrusive rocks of the central Sierra Nevada contain more than 79 percent normative Ab + An + Or + Qz. If the composition of the lower continental crust is similar to or slightly more felsic than andesite, as seems likely, the system NaAlSi 3 O 8 -CaAl 2 Si 2 O 8 -KAlSi 3 O 8 -SiO 2 -H 2 O provides an excellent chemical model for testing various schemes of fusion of the lower crust and crystallization of the resulting magmas. From consideration of this system in conjunction with field and petrographic data, we conclude that the intrusive rocks are best explained by repeated episodes of equilibrium fusion corresponding to magmatic sequences defined by field, petrologic, chemical, and geochronologic data. Fractional crystallization of the crystal-liquid mush generated by equilibrium fusion, coupled with periodic upward or lateral movement of the less crystallized central part of the magma, would produce the characteristic mafic to felsic sequence of intrusion; each mafic to felsic sequence corresponds to a separate equilibrium fusion event. In contrast, a close approach to fractional fusion of the lower crust is inadequate for obtaining most of the plutonic rocks, because rock compositions capable of being produced by this process do not match those observed. Normal amounts of conductive heat from the mantle and from radioactive decay in the crust may have been capable of causing fusion in the deepest parts of a thickened crust under the central part of the Sierra Nevada without the aid of a transient heat source from the mantle, but would have been inadequate where the crust was thin in the western Sierra Nevada. However, upward transport of andesitic and basaltic magmas generated along a Mesozoic subduction zone dipping beneath the Sierra Nevada would have provided sufficient additional heat to make fusion of the lower crust unavoidable. This implies that a major portion of the present batholith must have been derived from the lower crust.

California↗
USGS1970

Variations of major chemical constituents across the central Sierra Nevada batholith

A study of 193 chemical analyses of plutonic rocks from 132 localities in the central Sierra Nevada shows convincingly that K 2 O decreases systematically westward and suggests that Fe 2 O 3 and TiO 2 may also decrease westward and that FeO, MgO, and CaO may increase. The ratio K 2 O/SiO 2 obviously decreases westward across six of eight provisionally established sequences of granitic rocks. Plots of analyses of rocks from each sequence form discrete fields that are strongly elongate toward zero K 2 O at 40 to 45 percent SiO 2 . The boundaries between fields on these plots and between fields on plots of normative minerals on triangular diagrams are sharp. Compositional trends within sequences are different than the compositional changes that take place across the batholith—rocks in the western Sierra Nevada probably are not compositionally identical with rocks that are present at depth beneath the eastern Sierra Nevada. Progressive decrease of K 2 O in the Paleozoic and Mesozoic country rocks westward across the batholith is consistent with the anatectic model for its origin. However, it also is consistent with the hypothesis developed to explain chemical patterns in volcanic island arcs—that K 2 O increases toward continental land masses because of increasing depth of magma generation along landward-dipping seismic (Benioff) zones. The seismic-zone hypothesis encounters several difficulties, but it cannot be ruled out.

California↗
USGS1967

Sierra Nevada batholith

The Sierra Nevada batholith is localized in the axial region of a complex faulted synclinorium that coincides with a downfold in the Mohorovicic discontinuity and in P-wave velocity boundaries within the crust. Observed P-wave velocities are compatible with downward increase in the proportion of diorite, quartz diorite, and calcic granodiorite relative to quartz monzonite and granite in the upper crust, with amphibolite or gabbro-basalt in the lower crust, and with periodotite in the upper mantle. The synclinorium was formed in Paleozoic and Mesozoic strata during early and middle Mesozoic time in a geosyncline marginal to the continent. Granitic magmas are believed to have formed in the lower half of the crust at depths of 25 to 45 kilometers or more, primarily as a result of high radiogenic heat production in the thickened prism of crustal rocks. Magma was generated at different times in different places as the locus of downfolding shifted. It rose into the upper crust because it was less dense than rock of the same composition or residual refractory rocks. Refractory rocks and crystals that were not melted and early crystallized mafic minerals that settled from the rising magma thickened the lower crust. Wall and roof rocks settled around, and perhaps through, the rising magma and provided space for its continued rise. Erosion followed each magmatic episode, and 10 to 12 kilometers of rock may have been eroded away since the Jurassic and 7 to 10 kilometers since the early Late Cretaceous.

California↗