Till and bedrock of the Ashby-Lowell-Fitchburg-Billerica-Sterling 11-quadrangle area in Northeast-Central Massachusetts - till_bedrock

The till_bedrock data layer is part of a comprehensive study to produce a statewide digital map of the surficial geology at a 1:24,000-scale. This compilation of surficial geologic materials defines the areas of exposed bedrock, and the boundaries between glacial till, glacial stratified deposits, and overlying postglacial deposits. The till_bedrock layer shows areas of thin till, thick till, bedrock outcrops, and areas of abundant outcrop and shallow bedrock for a 11-quadrangle area in northeast-central Massachusetts. Thin till and bedrock outcrops polygons are mutually exclusive; thick till polygons overlie areas of thin till, and abundant outcrop/shallow bedrock polygons overlie areas of thin till and bedrock outcrops. This data layer should be used in conjunction with the overlying stratified_deposits, early_postglacial, and postglacial data layers.