Green Lodge Formation of Rhodes and Graves

Quartzite and slate; contains fossils of questionable Late Cambrian age.
State Massachusetts
Name Green Lodge Formation of Rhodes and Graves
Geologic age Upper Cambrian?
Lithologic constituents
Metamorphic > Metasedimentary > Metaclastic > Quartzite
Metamorphic > Metasedimentary > Metaclastic > Slate
Comments Part of Milford-Dedham Zone (Tertiary and Older Rocks). Secondary unit description per MA023 as reported in USGS Geologic Names lexicon (ref. MA024): Used throughout report as Green Lodge Formation of Rhodes and Graves (1931) [implying that USGS does not recognize it as a formal name]. Named by Rhodes and Graves (1931) for quartzite containing poorly preserved brachiopod impressions near Dedham, MA. Fossiliferous quartzite is in a sequence of light-gray quartzite overlain by dark-gray phyllite containing siltstone laminae and thin layers of siltstone containing limonite-bearing pits. Sequence was exposed in hill south of MA Hwy 128 near Westwood-Dedham town line. Rhodes and Graves assigned the formation a Late Cambrian age on basis of fossil impressions. Shaw (1961) examined the fossils and stated that they were too poorly preserved for reliable assignment. Therefore, Green Lodge is shown as questionably Late Cambrian on MA State Bedrock map (Zen and others, 1983). Outcrops are no longer accessible due to construction. Rhodes and Graves (1931) estimated thickness of Green Lodge to be not less than 300 m. Chute (1964) estimated about 150 m of phyllite overlying an undetermined thickness of quartzite. He also mapped similar phyllite on main Amtrak railroad line in southern Norwood, MA, but did not correlate it with Green Lodge. Green Lodge may be more extensive beneath glacial drift than it appears; it is shown on State bedrock map as covering a larger area than shown by either Rhodes and Graves (1931) or Chute (1964). Age remains Late Cambrian(?) (Goldsmith, 1991).
NGMDB product
Counties Norfolk