Scientific Investigations Map 3052
The bedrock geology of the Old Lyme quadrangle consists of Neoproterozoic and Permian gneisses and granites of the Gander and Avalon terranes, Silurian metasedimentary rocks of the Merrimack terrane, and Silurian to Devonian metasedimentary rocks of uncertain origin. The Avalon terrane rocks crop out within the Selden Neck block, and the Gander terrane rocks crop out within the Lyme dome. The Silurian to Devonian rocks crop out between these two massifs.
Previous mapping in the Old Lyme quadrangle includes the work by Lawrence Lundgren, Jr. Lundgren's work provides an excellent resource for rock descriptions and detailed modal analyses of rock units that will not be duplicated in this current report. New research that was not covered in detail by Lundgren is the focus of this report and includes (1) evaluation of the rocks in the core of the Lyme dome in an effort to subdivide units in this area; (2) structural analysis of foliations and folds in and around the Lyme dome; (3) geochronology of selected units within the Lyme dome; and (4) analysis of joints and the fracture properties of the rocks.
Posted November 2009
For additional information, please contact Gregory Walsh.
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Walsh, G.J., Scott, R.B., Aleinikoff, J.N., and Armstrong, T.R., 2009, Bedrock geologic map of the Old Lyme quadrangle, New London and Middlesex Counties, Connecticut: U.S. Geological Survey Scientific Investigations Map 3052, 2 sheets, scale 1:24,000, 25-p. text, available only online at https://pubs.usgs.gov/sim/3052. (Supersedes USGS Open-File Report 2006–1296.)