TY - MAP T1 - Preliminary Bedrock Geologic Map of the Hudson 7.5' Quadrangle Worcester and Middlesex Counties, Massachusetts Y1 - 2014 A1 - Joseph P Kopera A1 - W.R. Hansen KW - #BedrockMaps KW - #MGSPub KW - acton granite KW - ayer granite KW - Berlin KW - Bolton KW - Boxborough KW - Clinton-Newbury Fault KW - gneiss KW - Harvard KW - Harvard Conglomerate KW - Hudson KW - magnetite KW - Malborough KW - marble KW - migmatite KW - nashoba KW - Stow KW - tadmuck brook schist KW - Vaughn Hills AB - The Hudson quadrangle straddles the Clinton-Newbury Fault Zone (CNFZ), which separates low metamorphic grade Silurian turbiditic metasediments and Devonian plutons of the Nashua sub-belt (Robinson and Goldsmith, 1991) of the Merrimack Terrane to the northwest from the high-grade, migmatitic Cambro- Ordovician arc-complex of the Nashoba Terrane (Walsh et al., 2011; Loan 2011). This general area comprises the suture between the Gander and Avalon composite terranes of the Northern Appalachians (cf. Hibbard et al., 2006). Metasedimentary rocks of the Merrimack Terrane are generally poorly exposed, with intrusives (Day, Dayp, SDgdt) and the Clinton-Newbury Fault zone and associated rocks (Ot) forming a prominent northeast trending ridge (Oak Hill in the town of Harvard) marking the eastern bordering slope of the Worcester Plateau (Emerson, 1917, p. 16). Elevation and local topographic relief gradually decreases and glacial cover increases to the east-southeast across the strike of the Nashoba Formation, which, locally, forms low-relief NE-trending strike-parallel ridges. These are cut by dramatic cross-strike cliffs and glacial spillway gorges developed along cross-strike joints and brittle faults, most notably on the western slopes of Rattlesnake Hill, southern slope of Powder House Hill and in Camp Resolute in Bolton in the west-central portion of the quadrangle, and the southern slope of the hill along the west side of Codman Hill Road in Harvard in the north-central portion of the quadrangle. The migmatitic ortho- and paragneisses, schists and associated metavolcanic rocks of the Nashoba Formation (_Sn) form a northeast striking belt underlying the southern two-thirds of the quadrangle. These are intruded by a variety of presumed Ordovician to Silurian intermediate intrusives (OSd, OSaqd) and Devonian or younger tonalites to granites (Dan, Danp, Dac). JF - Open File Report PB - Massachusetts Geological Survey U1 - Note: This map supersedes "Preliminary bedrock geologic map of the Hudson quadrangle, Massachusetts", MGS map published in 2005 Report accompanies map-- be sure to download both! ER - TY - MAP T1 - Preliminary bedrock geologic map of the Hudson quadrangle, Massachusetts Y1 - 2005 A1 - Joseph P Kopera A1 - Hansen, W.R. KW - #BedrockMaps KW - #MGSPub KW - acton granite KW - ayer granite KW - Berlin KW - Bolton KW - Boxborough KW - Clinton-Newbury Fault KW - gneiss KW - Harvard KW - Harvard Conglomerate KW - Hudson KW - magnetite KW - Malborough KW - marble KW - migmatite KW - nashoba KW - Stow KW - tadmuck brook schist KW - Vaughn Hills AB - This map has been superseded by MGS OFR 14-01: Preliminary Bedrock Geologic Map of the Hudson 7.5' Quadrangle Worcester and Middlesex Counties, Massachusetts This map is an interim update to W.R. Hansen's 1956 Bedrock Geology of the Hudson and Maynard 7.5' quadrangles (USGS Bulletin 1038). This draft version of the Bedrock Map of the Hudson Quadrangle (Kopera, 2005) has been removed pending the future release of an updated version. The above version should be considered outdated. If you would like a copy of this map, please contact Joseph Kopera at jkopera[at]geo[dot]geo[dot]umass[dot]edu

JF - Open-File Report PB - Massachusetts Geological Survey U2 -

1:24000

ER - TY - MAP T1 - Preliminary bedrock geologic map of the Westford quadrangle, Massachusetts Y1 - 2009 A1 - Joseph P Kopera A1 - D.C. Alvord A1 - Richard H Jahns A1 - M.E. Willard A1 - W.S. White KW - #BedrockMaps KW - #MGSPub KW - Acton KW - amphibolite KW - ayer granite KW - Berwick formation KW - Boxborough KW - calc-silicates KW - Carlisle KW - Chelmsford KW - chelmsford granite KW - Clinton-Newbury Fault KW - Concord KW - diorite KW - gneiss KW - Groton KW - LITTLETON KW - magnetite KW - marble KW - migmatite KW - Nashoba Formation KW - phyllonite KW - tadmuck brook schist KW - Tyngsborough KW - Westford AB - Bedrock Geologic Map contains brittle fracture data Mapping still in progress. For interim fracture database, please contact Joe Kopera JF - Open-File Report PB - Massachusetts Geological Survey U2 -

1:24000

ER - 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 -