Pliocene and Pleistocene
Maryland Geological Survey, 1896-; Shattuck, George Burbank, b. 1869; Clark, William Bullock, 1860-1917; Hollick, Charles Arthur, 1857-1933; Lucas, Frederic A. (Frederic Augustus), 1852-1929; Hay, Oliver Perry, 1846-1930; Sellards, Elias Howard, b. 1875; Ulrich, Edward Oscar, 1857-1944