A REVISED TECTONIC MAP OF CONNECTICUT: UPDATES BASED ON 3 DECADES OF MAPPING, GEOCHRONOLOGY, AND GEOCHEMISTRY

Connecticut, entirely with the Appalachian Mountains of southern New England, is underlain by numerous zones of bedrock which include ancestral North America, ancient sedimentary basins and volcanic island arcs, and exotic terranes which represent at least one full Wilson Cycle. Such a complicated geologic history takes detailed, incremental study to understand; 30+ years of study by numerous researchers since the publication of the previous Connecticut tectonic map by Rodgers (1985) have improved understanding of the regional geology.

The process of digitizing the tectonic map of Rodgers (1985) presented an opportunity to compile an updated tectonic map to more accurately portray the current geologic consensus of the bedrock geology. Results collected from a comprehensive literature review of geologic mapping, geo- and thermochronology, geochemistry and structural analyses were compiled into a NGCMP ‘09 style database in ArcGIS 10.2.2 using the Geologic Mapping Toolbar from the Arizona Geological Survey, with symbology following the FGDC Digital Cartographic Standard for Geologic Map Symbolization. Units were identified and grouped based on age, lithology, and paleoenvironment (arcs, basins, continental basement). Significant updates to the Rodgers tectonic map include areas of eastern Connecticut with the Gander terrane discriminated from Avalon terrane (after Walsh et al., 2007), division of Rodgers’ Merrimack zone into 3 Early Silurian basins, a Late Devonian Basin, and the Cambrian to Pre-Cambrian, Quinebaug Formation. Major changes to the map in the west included updated geologic lines of the Waterbury Dome (after Dietsch et al., 2010), delineation of Ordovician arc rocks which intruded Ordovician to Cambrian metasedimentary rocks, both of which are uncomfortably overlain by Silurian metasediments.

This tectonic map represents an in-progress, current understanding of Connecticut bedrock geology. Our hope is that this map will be of service to educating the public at large about Connecticut’s bedrock geology and will inspire future scientific research.