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Gilbert H. Espenshade

Publications and source records attributed to Gilbert H. Espenshade.

18 recordsLinked to original sources
USGS1967

Geology and petrology of the Greenville quadrangle, Piscataquis and Somerset Counties, Maine

In the Greenville quadrangle, west-central Maine, slate, siltstone, and sandstone (calcareous and noncalcareous) of probable Silurian to Early Devonian age are intruded by a large mafic pluton and two granitic stocks of probable Early Devonian age. Ages of the sedimentary rocks are based upon tentative correlations with fossiliferous beds in adjacent quadrangles because the few fossils in the Greenville quadrangle are nondiagnostic; ages of the intrusive rocks are based upon radiometric age determinations. The sedimentary rocks are tightly folded about northeast-trending axes and have strong slaty cleavage. Widespread graded bedding is very useful in determining the tops of beds and thus the location of fold axes. The sedimentary rocks are in the chlorite zone of metamorphism except in the contact aureoles where the metamorphism ranges from the biotite zone, through the andalusiite-amphibole zone, to the sillimanite-cordierite zone adjacent to the intrusions; retrograde metamorphism is a minor local feature. The mafic rocks are part of the Moxie pluton, which extends southwest and northeast of the Greenville quadrangle for a total distance of about 45 miles. Troctolite and norite are the principal rock types; gabbro is less common. Plagioclase is the dominant mineral; it usually makes up 50-75 percent of the rock. Olivine and orthopyroxene are widespread, clinopyroxene is uncommon and biotite and hornblende are generally present in small amounts. The rocks can be separated into magnesium-rich and iron-rich varieties; magnesium-rich olivine and orthopyroxene are usually accompanied by plagioclase containing from 57 to 77 percent anorthite, and iron-rich olivine and orthopyroxene are associated with plagioclase containing about 50-62 percent anorithite. Compositional layering is rare, but flow structure is very common. Flow structure generally dips northward to eastward, whereas geophysical data indicate that the contacts of the pluton dip southeastward. The granitic stocks are discordant pipelike bodies that range from granodiorite to quartz monzonite in composition. Both the mafic and the felsic intrusions are undeformed and unmetamorphosed. Slate quarrying was once an important industry in the region, but in 1965 only one quarry was active at Monson just east of the report area. Slate is a potential source of raw material for lightweight concrete aggregate. There are several possible sites for stone quarries in the intrusive masses. Sand and gravel resources seem to be limited. Small amounts of sulfides that have low copper and nickel values are known at a few places in the mafic pluton.

Maine↗
USGS1956

Geologic features of areas of abnormal radioactivity south of Ocala, Marion County, Florida

Areas of abnormal radioactivity south of Ocala, Marion County, Fla., discovered in 1953 by aerial survey, were investigated by surface examination and by 10 power auger drill holes. Inter-bedded clay, clayey sand, and uraniferous phosphorite occur in the areas of anomalous radioactivityo Miocene fossils occur at three localities in these beds which are evidently outliers- of Miocene sediments on the Ocala limestone of Eocene age. The preserved outliers are southwest of the main belt of Miocene sediments. The principal uraniferous rocks are clayey, sandy, pellet phosphori1te that occurs in beds a few feet thick, and very porous, phosphatic sand rock which makes abundant float at many places. Apatite forms the phosphate pellets in the unweathered phosphorite. The very porous, phosphatic sand rock is the highly leached residuum of the pellet phosphorite and is composed mainly of quartz, kaolinite, wavellite, and crandallite (pseudowavellite). It closely resembles the aluminum phosphate rock of the 'leached zone' of the Bone Valley formation in the land-pebble phosphate district.

Trace Elements Memorandum↗
USGS1952

Annotated bibliography and index map of sulfur and pyrites deposits in the United States and Alaska (including references to July 1, 1951)

Since the end of World War II, the pattern of sulfur production and consumption in the United States and abroad has changed markedly from the pattern that existed before the war. Although production of sulfur in the United States in 1950 was more than double the average annual production for the 1935-39 period, consumption had increased at such a rate that current domestic and foreign demand for U. S. sulfur exceeds the productive capacity of the industry. Production of sulfur (including brimstone, pyrites, and all other forms) in the 1935-39 period and in 1950 are compared in the table below.

Circular↗
USGS1952

Manganese, iron, and barite deposits of the James River-Roanoke River district, Virginia

During the period 1940-1942 the United States Geological Survey made a geologic study of the manganese deposits of the James River-Roanoke River district, in the general vicinity of Lynchburg, Va. (fig. 1), as part of its program of strategic minerals investigations. This work was done by the writer and supervised by D. F. Hewett. John Rodgers and W. R. Wagner assisted during part of the project. In the course of the investigation, the geology was mapped over an area about 60 miles long and several miles wide, from Altavista on the Roanoke River northeast to Howardsville on the James River (fig. 2); and the mineral deposits-principally manganese, iron, and barite-were studied. After completion of the geologic studies, the writer participated in an exploration project conducted by the United States Bureau of Mines in the early summer of 1942 at five manganese deposits in the district. This preliminary report presents the essential information concerning the mineral deposits of the region in advance of the more comprehensive report on the geology and mineral deposits that will be published as a bulletin of the U.S. Geological Survey.

Virginia↗