Hadlyme Formation of Waterford Complex here defined in the Avalon terrane of eastern CT to include three extrusive volcanic facies: North Plain, Jennings Pond, and Mansfield Hollow lithofacies. Term lithofacies, rather than member, used to convey vertical or chemical continuity, not lateral continuity. Mansfield Hollow lithofacies described as light-gray-weathering plagioclase-quartz gneiss with conspicuous layering of dark hornblende and biotite, white to cream K-feldspar, and local amphibolite. Thickness varies from about 235 m to 650 m. Crops out around the Willimantic dome and in three small outliers to the south and west. Overlies Willimantic Gneiss; upper contact cut by Willimantic fault. Unit is relatively albitic and ranges from granodioritic to tonalitic to trondhjemitic.

Source: GNU records (USGS DDS-6; Reston GNULEX).