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National Geologic Map Database

Geologic Unit: Portland

Usage:

Portland Formation of Newark Supergroup (CT*,MA*)
Portland Arkose of Newark Supergroup (CT*)


Geologic age:

Jurassic, Early*
Sinemurian, late
Pliensbachian
Toarcian, early
Jurassic, Middle(?)
Aalenian(?)
Bajocian(?)
Bathonian(?)


Type section, locality, area and/or origin of name:

Exposures in the Portland "brownstone" quarries near Middletown, Middlesex Co., CT (Krynine, 1950).


AAPG geologic province:

New England province*
Hartford basin*
Pomperaug basin*


For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.

Asterisk (*) indicates published by U.S. Geological Survey authors.

"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).

Slash (/) indicates name does not conform with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005). This may be explained within brackets ([ ]).