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Geology topics

R. W. Kistler

Publications and source records attributed to R. W. Kistler.

27 records · Page 2Linked to original sources
USGS1973

Radiometric dating of intrusive rocks in the Cottonwood area, Utah

Recently completed fission-track and K-Ar dating of zircon, sphene, apatite, muscovite, biotite, and hornblende indicate that the Clayton Peak stock was intruded 37-41 m.y. ago, the Alta stock about 32-33 m.y. ago, and the Little Cottonwood stock between 24 and 31 m.y. ago. Pb-a ages on zircon, though showing the same sequence, are about twice as great and are inferred to represent a partial mixing of inherited Precambrian zircons. Acceptance of a middle Tertiary age for the Little Cottonwood stock requires revision of earlier interpretations that it could be as old as Late Cretaceous. K-Ar dates also indicate that the Keetley Volcanics are 32 to 35 m.y. old, and a single date of 37.3 m.y. was obtained on the Traverse Volcanics, suggesting that they are more closely related to volcanic activity in the adjoining Oquirrh Mountains.

Utah↗
USGS1971

Sierra Nevada plutonic cycle: Part I, origin of composite granitic batholiths

Intrusion of Mesozoic batholiths in California and the western North America Cordillera began in the Late Triassic 210 m.y. ago and ended in the Late Cretaceous 80 m.y. ago. Emplacement of granitic rocks was apparently not continuous but was accomplished during five major epochs of intrusion at approximately 30 m.y. intervals, each epoch taking 10 to 20 m.y. to complete. A progressive transgression of epicontinental seas onto the midcontinent occurred during the same interval of time as the batholithic emplacement to the west. A penecontemporaneous deformation near the loci of granitic emplacement and a temporary regression during the major progressive transgression of seas onto the midcontinent are correlated with each intrusive epoch. The locus of Mesozoic granitic rocks was a source of sediments during most of the period of time required to emplace the batholiths; the origin of the batholithic magmas cannot be related only to localized down-warping of geosynclines. The source of the major proportion of the mobile granodioritic magmas of the Sierra Nevada was within the mantle, as is indicated by Sr isotope data. All plutons now exposed in the Sierra Nevada, whether of Cretaceous age or older, were emplaced at depths of a very few kilometers, the shallowest having been emplaced at depths of 4 km or less. The spatial relationships among these synchronous geologic phenomena and the geochemical and geophysical data from the same region are accounted for by a northwestward drift of North America in the region of the western Cordillera of the United States onto and across a Mesozoic feature that had characteristics like present-day oceanic rises.

California↗
USGS1971

Sierra Nevada plutonic cycle: Part II, tidal energy and a hypothesis for orogenic-epeirogenic periodicities

The dissipative power of the solid earth tides is the order of 10 19 ergs/sec, or a few percent of terrestrial heat flow. It is proposed that this energy is concentrated along oceanic ridge systems and in the asthenosphere by mechanisms of viscous dissipation involving shear melting. Tidal energy localizes and sustains sources of sea-floor spreading through the melting mechanism, convection and magmatic transfer. Components of this energy enter the continent as magmatic heat either where ridge type sources and continents interact or where lateral motions induce shear zones and viscous dissipation within the continent. Temporal maxima of igneous intrusion into continental crust and related epeirogenic oscillations, spaced at intervals of about 30 m.y., are explained in terms of periodic thermal instabilities in the process of shear melting in the mantle. That is, maxima in rates of magma production in the mantle are relieved by vertical magmatic transfer. This process is coupled with lateral motions of the continent in a way analogous to episodic creep episodes of much shorter period in motions of active fault systems. Calculated periodicities are found to be simultaneously compatible with (l) the Sierra Nevada intrusive epochs of Part I, (2) oscillations in the eustatic curve during the Mesozoic Era, (3) concepts of sea-floor spreading, and (4) the magnitude of tidal power. More profound epeirogenic oscillations, having periods of about 200 m.y., are induced by variations in proportioning of tidal energy dissipation between the solid earth and the epicontinental seas. Thus, the tidal deformations of the earth provide information that leads to a general dynamic theory where magmatism, orogency, epeirogeny, sea-floor spreading and continent migration are systematically interrelated.

California↗
USGS1965

Isotopic ages of minerals from granitic rocks of the central Sierra Nevada and Inyo Mountains, California

Potassium-argon ages of biotite and hornblende from specimens of 17 granitic plutons in the central Sierra Nevada and the western Inyo Mountains, California, range from 69 to 183 m. y. The Mount Givens, Lamarck. and Round Valley Peak Granodiorites and related younger and more felsic quartz monzonites represent a pulse of magma emplaced in the general time interval of 80-90 million years ago, during Cretaceous time. Mineral ages of granitic rocks that flank these plutons on both the east and the west have been reduced during the emplacement of the Cretaceous intrusive rocks and are minimum ages for the time of crystallization. The ages of hornblende from the Tinemaha Granodiorite (150 to 180 m. y.) may approach crystallization dates. In conjunction with ages for other intrusive rocks in the Sierra Nevada and adjacent desert ranges they strongly suggest a magmatic episode during the Early Jurassic.

California↗