Issues

COVER EXPLANATION.—Exposures of the middle Tullock Member (early Paleocene, ca. 65.72–65.12 Ma) of the Fort Union Formation in Biscuit Basin (Garfield County, Montana), showing a succession of three cross-cutting channel deposits. The yellow beds to the lower left and right, and the gray beds in the middle of the image have produced some of the largest fossil collections of early Paleocene mammals.