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William P. Irwin

Publications and source records attributed to William P. Irwin.

30 records · Page 2Linked to original sources
USGS1982

Paleomagnetic study of some Cretaceous and Tertiary sedimentary rocks of the Klamath Mountains province, California

Paleomagnetic investigation of Cretaceous outliers and Tertiary sedimentary strata of the Klamath Mountains province, and of onlapping Cretaceous strata, has shown the rocks to be largely remagnetized. Samples studied are from the Upper Jurassic to Upper Cretaceous Great Valley sequence, Upper Cretaceous Hornbrook Formation, Eocene Montgomery Creek Formation, and Oligocene(?) Weaverville Formation. Cretaceous samples that survived the remagnetization have a mean remanence direction that is very close to the expected direction of the Cretaceous magnetic field at the locality of the Klamath Mountains. Data from both primary and remagnetized samples suggest the possibility of 11.5° ± 15.8° of post-Cretaceous clockwise rotation of the Klamath Mountains province. None of the data from either the primary or remagnetized samples shows evidence of the large amounts (∼ 70°) of clockwise rotation that other workers have measured for the lower Tertiary of the Oregon Coast Range. Our data indicate that the Oregon Coast Range and Klamath Mountains province did not behave as a single rigid block during the early Tertiary. They also suggest that any post-Oligocene rotation of the Klamath Mountains province is less than the approximately 30° post-Oligocene rotation recently proposed for a combined Oregon Coast Range–Klamath Mountains–Cascade Range block.

California↗
USGS1978

Global distribution of carbon dioxide discharges, and major zones of seismicity

Carbon dioxide discharges of the circum-Pacific belt are in a seismically active zone and in part stem from contact metamorphism. Carbon dioxide discharges in Europe and Asia Minor, also in an area of high seismic activity, are in part from regional metamorphism and are in areas of very high heat flow.

Water-Resources Investigations Report↗
USGS1975

Geologic map showing springs rich in carbon dioxide or or chloride in California

Carbon dioxide- and chloride-rich springs occur in all geologic provinces in California, but are most abundant in the Coast Ranges and the Great Valley. The carbon-dioxide-rich springs issue mainly from Franciscan terrane; they also are rich in boron and are of the metamorphic type (White, 1957). Based on isotopic data, either the carbon dioxide or the water, or both, may be of metamorphic origin. Because of high magnesium values, the water of many of the carbon-dioxide-rich springs is thought to have passed through serpentinite. The chloride-rich waters are most common in rocks of the Great Valley sequence. Nearly all are more dilute than present-day sea water. The similarity in isotopic compositions of the metamorphic carbon-dioxide-rich water and the chloride-rich water may indicate a similar extent of water-rock interaction.

California↗
USGS1975

Paleotectonic investigations of the Pennsylvanian System in the United States, Part I: Introduction and regional analyses of the Pennsylvanian System

The Pennsylvanian is the fourth geologic system to be analyzed and synthesized by geologists of the U.S. Geological Survey in the form of a paleotectonic study covering the conterminous United States. Earlier investigations were of the Jurassic, Triassic, and Permian Systems. Results were published as Miscellaneous Geologic Investigation Maps I-175, I-300, and I-450 and in Professional Paper 515. The objective of these investigations is to provide in graphic form the factual basis for recognition of tectonic events of each system on a countrywide scale. The maps in this publication depict rock thickness, generalized lithology, ancient geography, and other regional relations of the Pennsylvanian System. Method of preparation of the maps, the stratigraphic limits of the map units, and various stratigraphic and structural features and their probable tectonic significance are discussed. Pennsylvanian data were largely compiled between 1961 and 196 by 16 geologists, including the late Harold R. Wanless, who covered the five eastern regions and contributed to several of the special studies. The areas of responsibility of the cooperating geologists are indicated in figure 1. Work in Kansas was done by Gary F. Stewart, of the Kansas Geological Survey. Results of this investigation are presented in three units. Part I comprises an introduction and 17 chapters, each describing and discussing one of the regions in which the conterminous United States was divided for purposes of study and mapping. Part II is a synthesis of Pennsylvanian history to accompany interpretive maps of the five divisions of the Pennsylvanian System treated in this publication; it also includes a series of chapters on depositional environments, climatic conditions, and economic products of the system. The final section of part II is devoted to an index of localities and sources used in construction of the principal maps of this publication. Part III consists of the plates on which are presented the major maps and sections.

Professional Paper↗
USGS1968

Isotopic age of the Nevadan Orogeny and older Plutonic and metamorphic events in the Klamath Mountains, California

Several metamorphic and plutonic events have been recognized in the Klamath Mountains utilizing potassium-argon and rubidium-strontium mineral and whole-rock ages. The oldest known metamorphic event in the region produced the Abrams Mica Schist and the co-extensive Salmon Hornblende Schist. Strontium evolution diagrams indicate that the age of primary metamorphism of the Abrams Mica Schist is approximately 380 m.y. (Devonian). The Stuart Fork Formation of Davis and Lipman (1962), the schists of Condrey Mountain, and related schists were produced during a Middle and Late Jurassic metamorphic event. Granitic plutonic rocks are divided into four groups that are different in age and somewhat different in chemical characteristics. The oldest pluton, the Pit River stock, has a minimum age of 246 m.y. (Permian) and is grouped with the Castle Crags pluton. The other three plutonic groups are Middle and Late Jurassic and are characterized by the following ranges in isotopic age: 165 to 167 m.y., 145 to 155 m.y., and 127 to 140 m.y. The principal lode gold deposits in the California part of the Klamath Mountains seem to be related to the youngest group of plutons. If the Nevadan orogeny in this area is restricted to a Middle and Late Jurassic deformational, metamorphic, and plutonic event, the orogeny includes the emplacement of plutons of the three younger groups and the metamorphic development of the Stuart Fork Formation, schists of Condrey Mountain, and related schists.

California↗
USGS1957

Franciscan group in Coast Ranges and its equivalents in Sacramento Valley, California

The Franciscan group is an assemblage of detrital and chemical sedimentary and volcanic rocks that crops out discontinuously in a structurally complex, northwesterly trending belt along the Coast Ranges of Cahfornia. On the east, along the west side of the Sacramento Valley, a thick section of detrital sedimentary rocks has been subdivided into the Knoxville, Paskenta, and Horsetown forma tions of Late Jurassic and Early Cretaceous age, and several units of early Late Cretaceous age. The Sacramento Valley section represents deposition during most of the time from Late Jurassic to early Late Cretaceous. The Franciscan group is widely held to be restricted to Late Jurassic age, the Knoxville formation to be an upper shaly phase of the Franciscan group, and the two to be overlain unconformably by detrital strata of Cretaceous age. Sparse paleontologic evidence indicates this view to be incorrect. Rather, the Franciscan group seems mainly to have been deposited contemporaneously with the Knoxville, Paskenta, Horsetown, and lower Upper Cretaceous strata, as fossils ranging from Late Jurassic to early Late Cretaceous in age have been found in the Franciscan group. The Franciscan group and strata of the Sacramento Valley section therefore may represent two fades of the same stratigraphic section.

California↗