TY - MAP T1 - Progress map of the preliminary bedrock geologic map of the Billerica quadrangle, Massachusetts Y1 - 2011 A1 - Matthew A Massey KW - #BedrockMaps KW - #FractureMaps KW - #MGSPub KW - Bedford KW - Berwick formation KW - Billerica KW - Billerica Schist KW - Boxford formation KW - Carlisle KW - Chelmsford KW - Clinton-Newbury Fault Zone KW - Concord KW - fracture KW - gneiss KW - joints KW - Lowell KW - magnetite KW - migmatite KW - nashoba KW - schist KW - Spencer Brook Fault KW - tadmuck brook schist KW - Tewksbury AB - This map also contains brittle fracture data as part of the GIS files. This map is a progress report of bedrock geologic mapping currently underway in the Billerica quadrangle. It is a compilation of ongoing field mapping (Massey, this study) and previously published work in the area (Alvord, 1973, 1975; Jahns et al.1959). The Billerica quadrangle is located approximately 20 miles northwest of Boston along Route 3, just south of Lowell, in northeastern Massachusetts, encompassing the northwestern most Nashoba terrane and it’s boundary with the Merrimack belt (Figure 1). In the Billerica quadrangle, the Merrimack Belt consists of limited exposures of highly strained metasediments, or possibly orthoschist derived from reconstituted igne- ous protolith. The Clinton-Newbury fault zone separates the Merrimack Belt from multiply deformed, polymetamorphic biotite gneisses, migmatites, and amphibolites of the Nashoba terrane. PB - Massachusetts Geological Survey U2 - 1:24000 ER -