Proterozoic Mattapan Volcanics (Zm)
These felsic rocks are exposed on the south of the Boston Basin, and lay between the Dedham Granite and the Roxbury Conglomerate. They correlate to the Lynn Volcanics in Middlesex Fells and elsewhere north of Boston. The Roxbury (PzZr) mapped on Hough’s Neck (east of “Quincy”, map) is at least partly Mattapan, as seen at Rock Island (lower photos), which was quarried for “trap rock” ~ 1910. See captions for more.
#volcanics #igneous #geology #Boston #Quincy

Proterozoic Mattapan Volcanics (Zm)
These felsic rocks are exposed on the south of the Boston Basin, and lay between the Dedham Granite and the Roxbury Conglomerate. They correlate to the Lynn Volcanics in Middlesex Fells and elsewhere north of Boston. The Roxbury (PzZr) mapped on Hough’s Neck (east of “Quincy”, map) is at least partly Mattapan, as seen at Rock Island (lower photos), which was quarried for “trap rock” ~ 1910. See captions for more.
#volcanics #igneous #geology #Boston #Quincy