Used as Squantum Member of Roxbury Conglomerate of Proterozoic to earliest Paleozoic age. Included within main body of Roxbury; no members of Roxbury are shown separately on map.

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

Authors state, "...historic stratigraphy and stratigraphic units of the Boston basin are suspect." They suggest that the only formal nomenclature that should be retained is Boston Bay Group, undifferentiated, and perhaps the Weymouth Formation and the Braintree Argillite. Units within the Boston Bay Group--the Cambridge Argillite, and the Brookline, Dorchester, and Squantum (Tillite) Members of the Roxbury Conglomerate--were defined largely on the basis of the percentage of conglomerate, diamictite, argillite, sandstone, siltstone, tuff, and matrix present. Authors believe that recognition of these units in the field is nearly impossible and propose a facies-derived model for the Boston basin. They suggest that the Boston Bay Group was deposited in a submarine fan/slope/apron environment.

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

Squantum Member of Roxbury Conglomerate is a distinctive diamictite, exposed north of Quincy, MA; however, in Brighton and Hingham, MA, described as a coarse conglomerate. Appears to pinch out in northern part of basin. Age is Proterozoic Z and possibly Early Cambrian. Report includes geologic maps and correlation charts. [Chapters A-J in U.S. Geological Survey Professional Paper 1366 are intended as explanations and (or) revisions to 1:250,000-scale MA State bedrock geologic map of Zen and others (1983).]

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