1. Bedrock geologic map of the Grafton quadrangle, Worcester County, Massachusetts Yale Public content 2011. 2012-05-01T16:46:37Z. 2013-03-18T22:02:19Z. Walsh, Gregory J. U.S. Dept. of the Interior, U.S. Geological Survey ; For sale by U.S. Geological Survey, Information Services. English. Public. Massachusetts and Worcester County.