NEW GEOLOGIC MAPPING IN THE STRUCTURALLY COMPLEX HARTFORD SOUTH QUADRANGLE, CONNECTICUT

A bedrock geologic map of the Hartford South Connecticut quadrangle is being constructed by an integrated team of students and professors from Eastern Connecticut State University and personnel form the Connecticut State Geology Survey (Department of Environmental Protection). Heavy development and the presence of dinosaur tracks within the quadrangle have raised public interest in understanding the bedrock geology of this part of the Hartford Basin. The Hartford Rift Basin contains Triassic to Jurassic sedimentary formations separated by three basalt flows deposited during initial rifting of Pangaea.

Data collected from 80 new and previously known outcrops includes GPS locations, bedding attitudes, lithology, and fault/fracture orientations. These data and sample locations are being incorporated into an ArcGIS database and map, which will be published electronically for public access upon completion of the project.

This Hartford South Quadrangle is a structurally complex section of the Hartford Basin. A series of major intra-basin faults pass through the center of the quadrangle that divide the basin into regions with wide surface expression of the New Haven Arkose (in the south) and wide surface expression of the Portland Formation (in the north). The quadrangle also contains a faulted anticline with an axis perpendicular to other major structures within the hanging wall of a large listric fault (part of the Eastern Border Fault). The key to correctly mapping the area is correctly identifying the many well-exposed basalt layers and recognizing their distribution throughout the quadrangle. Geochemical analyses of basalt samples are currently being interpreted to fingerprint the basalt layers and map the distribution of individual units. We are also performing a statistical comparison of fault orientations mapped in the Hartford South Quadrangle with the those of neighboring mapped quadrangles in an attempt to determine the correct orientation of intra-basin faults. Interpreting the complex structural components in the quadrangle will improve our understanding of the Hartford Basin's tectonic history.