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Primary Productivity by Phytoplankton in the Tidal, Fresh Potomac River, Maryland, May 1980 to August 1981

Description: Purpose and scope: The purpose of this study was to determine primary productivity and respiration of the fresh, tidal Potomac River. The data will be used by the authors and other researchers involved in modelling chemical and biological properties to calculate phytoplankton growth rates. Methods are documented in detail so that the report could serve as a reference. The report covers the period from May 1980 through August 1981. Five stations were selected for study that are representative of biologically important reaches of the fresh, tidal Potomac River.
Date: 1983
Creator: Cohen, Ronald R. H. & Pollock, Sheryl O.
Partner: UNT Libraries Government Documents Department

Gold Veins Near Great Falls, Maryland

Description: From abstract: Small deposits of native gold are present along an anastomosing system of quartz veins and shear zones just east of Great Falls, Montgomery County, Md. The deposits were discovered in 1861 and were worked sporadically until 1951, yielding more than 5,000 ounces of gold. The vein system and the principal veins within it strike a few degrees west of north, at an appreciable angle to foliation and fold axial planes in enclosing rocks of the Wissahickon Formation of late Precambrian (?) age. The veins cut granitic rocks of Devonian or pre-Devonian age and may be as young as Triassic. Further development of the deposits is unlikely under present economic conditions because of their generally low gold content and because much of the vein system lies on park property, but study of the Great Falls vein system may be useful in the search for similar deposits elsewhere in the Appalachian Piedmont.
Date: 1969
Creator: Reed, John Calvin, Jr. & Reed, John Calvin
Partner: UNT Libraries Government Documents Department

Chromite and Other Mineral Deposits in Serpentine Rocks of the Piedmont Upland, Maryland, Pennsylvania and Delaware

Description: From abstract: The Piedmont Upland in Maryland, Pennsylvania, and Delaware is about 160 miles long and at the most 50 miles wide. Rocks that underlie the province are the Baltimore gneiss of Precambrian age and quartzite, gneiss, schist, marble, phyllite, and greenstone, which make up the Glenarm series of early Paleozoic(?) age. These are intruded by granitic, gabbroic, and ultramafic igneous rocks. Most of the ultramafic rocks, originally peridotite, pyroxenite, and dunite, have been partly or completely altered to serpentine and talc; they are all designated by the general term serpentine. The bodies of serpentine are commonly elongate and conformable with the enclosing rocks.
Date: 1960
Creator: Pearre, Nancy C. & Heyl, Allen V., Jr.
Partner: UNT Libraries Government Documents Department

The Gabbros and Associated Hornblende Rocks Occurring in the Neighborhood of Baltimore, Maryland

Description: From introduction: The present paper is intended as a contribution to our knowledge of a particular phase of metamorphism in eruptive rocks, i.e., that one which is dependent on the secondary development of hornblende by the paramorphism or pseudomorphism of pyroxene.
Date: 1886
Creator: Williams, George Huntington
Partner: UNT Libraries Government Documents Department

Map Showing the Difference between the Potentiometric Surfaces of the Magothy Aquifer of September 1975 and September 1982 in Southern Maryland

Description: This is a map, scale 1:250,000, showing the difference between the potentiometric surfaces of the Magothy aquifer of September 1975 and September 1982 in southern Maryland.
Date: 1982
Creator: Mack, Frederick K.; Wheeler, Judith C. & Curtin, Stephen E.
Partner: UNT Libraries Government Documents Department