AERORADIOACTIVITY SURVEY AND AREAL GEOLOGY OF THE DISTRICT OF COLUMBIA AND PARTS OF MARYLAND, VIRGINIA, AND WEST VIRGINIA (ARMS-Ⅰ)

摘要

The Coastal Plain has predominantly low radioactivity levels, 100 to 400 cps (counts per second). Higher radioactivity (400 to 650 cps) is associated with glauconitic sand of the marine Upper Cretaceous or with detrital material that was derived from the nearby Piedmont.nThe Piedmont and Blue Ridge provinces have a wide range of radioactivity (100 to 1500 cps) because of the great variety of rocks. In general, low values (100 to 300 cps) are found over sandstone, quartzite, and mafic rocks. Areas underlain by shale, limestone, phyllite, schist, and gneiss have intermediate values of 400 to 600 cps. Highest radioactivity (more than 600 cps) is associated with granite and gneiss.