University of New Hampshire University of New Hampshire Scholars' Repository New England Intercollegiate Geological NEIGC Trips Excursion Collection 1-1-1976 Geologic Relationships of the Southern Portion of the Boston Basin from the Blue Hills Eastward Nellis, David A. Hellier, Nancy W. Follow this and additional works at: https://scholars.unh.edu/neigc_trips Recommended Citation Nellis, David A. and Hellier, Nancy W., "Geologic Relationships of the Southern Portion of the Boston Basin from the Blue Hills Eastward" (1976). NEIGC Trips. 243. https://scholars.unh.edu/neigc_trips/243 This Text is brought to you for free and open access by the New England Intercollegiate Geological Excursion Collection at University of New Hampshire Scholars' Repository. It has been accepted for inclusion in NEIGC Trips by an authorized administrator of University of New Hampshire Scholars' Repository. For more information, please contact
[email protected]. Trips A-4 & B-4 GEOLOGIC RELATIONSHIPS OF THE SOUTHERN PORTION OF THE BOSTON BASIN FROM THE BLUE HILLS EASTWARD by David A. Nellis boston State College and Nancy W. Hellier The structural, stratigraphic and petrologic relation ships in the Weymouth and Cohasset quadrangles are the princi ple subjects of this field trip. The Dedham Granodiorite is the oldest rock in this area and varies petrologically from granite to granodiorite to diorite. Overlying the Dedham Grano diorite are the lower Cambrian Weymouth Formation and the Middle Cambrian Braintree Argillite. The intrusive contact between Ordovician Quincy Granite and 3raintree Argillite will be noted. At some locations the Weymouth and Braintree formations are missing and the Dedham Granodiorite is overlain by the Bos ton Bay Group sedimentary and volcanic rocks of Pennsylvanian(?) age.