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Publications and source records attributed to J.C. Wright.
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These sections were measured prior to 1960, before adoption of the metric system. Publication was delayed by other assignments of the authors and later by the untimely death of J. C. Wright. They are being released at this time because of the increased interest in the uranium potential of Jurassic rocks. The Curtis, Summerville, Entrada, and Carmel Formations are the formations of the San Rafael Group in these sections.
A zone, 1 to 50 feet thick, at the base of the Nonesuch Shale , is relatively rich in copper, chiefly as chalcocite. Pyrite is the characteristic sulfide mineral of the overlying 400 to 600 feet of the formation. The boundary of the cupriferous zone with the pyrite zone regionally transgresses both stratigraphic layering and fades gradations indicative of ancient environmental boundaries. The top of the cupriferous zone is marked by the upward sequence, chalcocite-bornite-chalcopyrite-pyrite, and by the cadmium sulfide , greenockite. The sulfide zoning does not appear to be syngenetic. The regional configuration of the cupriferous zone suggests, instead, that the copper was introduced after deposition of the entire 50-foot sequence of strata. The area in which the top of the cupriferous zone is stratigraphically highest is related spatially, and probably genetically, to a zone of wedging in the underlying Copper Harbor Conglomerate.
The lithology and stratigraphy of the ore zones near the base of the Nonesuch formation in the vicinity of the White Pine copper mine, Ontonagon County, Michigan, are shown on preliminary stratigraphic sections that have been made available for examination. Partial logs of 91 holes, drilled by the Copper Range Company from 1937 to 1949 in an area of approximately 9 square miles, are graphically presented on 15 sheets. The stratigraphic sections, at vertical scale of 1 inch equals 4 feet, show lithologic details of composition, bedding, and color, in the lower 60 feet of the Nonesuch formation and in the top of the immediately underlying rocks. The stratigraphic sections of 7 drill holes long the line of the main service drift now being driven to develop the White Pine mine have copper assays (from records of the Copper Range Company) correlated with the lithology. These assays are representative of the area, and they illustrate the stratigraphic restriction of the ore and the persistent correlation between lithology and copper content. This open-file material, entitled "Stratigraphic sections at White Pine, Ontonagon County, Michigan", records the lithologic end stratigraphic classification of these drill cores by W. S. White end J. C. Wright, end copies are available for examination in the offices of the Geological Survey: Room 1033 (Library), General Services Administration Washington, D. C.; Room 213 Science Hall, University of Wisconsin, Madison 6, Wisconsin; and Calumet, Michigan; and at the office of the Geological Survey Division, Michigan Department of Conservation, Lansing, Michigan.