Bedrock Geology of the East Brookfield 7.5 Minute Quadrangle, South-Central Massachusetts

EDMAP PROPOSAL SUMMARY SHEET New bedrock mapping is proposed in south central Massachusetts that will test the extent to which dextral transpression in terranebounding midcrustal rocks extends eastward perpendicular to strike. Dextral transpression was documented in two prior EDMAP projects in central MA. A 1-10 km-wide, moderately to steeply dipping dextral high strain zone defines the eastern boundary of the Bronson Hill belt in central Mass. The proposed mapping project will specifically evaluate whether strike-slip or dipslip ductile displacement (or both) is developed in a region shown on the 1983 Massachusetts State Geologic Map as underlain by numerous ductile thrust faults in crystalline rocks.