Pumpkin Ground Member [of Harrison (Prospect) Gneiss] (CTOhp;0)

Pumpkin Ground (porphyritic) Member [of Harrison (Prospect) Gneiss] - Medium- to light-gray, medium- to coarse-grained, well-layered and foliated gneiss, composed of oligoclase, microcline, quartz, and biotite; some layers have numerous microcline megacrysts 1 to 5 cm across; others have hornblende. Minor layers of garnetiferous schist and gneiss. Pumpkin Ground and Beardsley Members of Harrison Gneiss, formerly considered conformable metavolcanic members, are here recognized as juxtaposed metaplutonic units and are renamed the Beardsley and Pumpkin Ground orthogneisses. Isotopic dating yields ages of 428+/-2 Ma (Early Silurian) for the Pumpkin Ground and 446+/-2 Ma (Late Ordovician) for the Beardsley, accepted by authors as crystallization ages. Pumpkin Ground intrudes the Trap Falls Formation. The Harrison Gneiss as described by Rodgers (1985) has no stratigraphic significance and cannot be correlated regionally (Sevigny and Hanson, 1993).

State	Connecticut
Name	Pumpkin Ground Member [of Harrison (Prospect) Gneiss]
Geologic age	Middle? Ordovician
Original map label	Ohp
Comments	Part of Central Lowlands; Iapetus (Oceanic) Terrane - Connecticut Valley Synclinorium; Hartland Belt Secondary unit description per CT007.
Primary rock type	gneiss
Secondary rock type	schist
Other rock types
Lithologic constituents	Major Metamorphic > GneissMedium- to light-gray, medium- to coarse-grained, well-layered and foliated gneiss, composed of oligoclase, microcline, quartz, and biotite; some layers have numerous microcline megacrysts 1 to 5 cm across; others have hornblende; minor layers of garnetiferous gneiss. Minor Metamorphic > Schistminor layers of garnetiferous schist
Map references	Connecticut Geological and Natural History Survey, DEP, in cooperation with the U.S. Geological Survey, 2000, Bedrock Geology of Connecticut, data format: shapefile, file name: bedrock, downloaded from: http://magic.lib.uconn.edu/cgi-bin/MAGIC_DBsearch2.pl?Geography=37800&Loc=0000 on 9/18/2003, scale 1:50,000. [http://magic.lib.uconn.edu/connecticut_data.html#environmental] [http://magic.lib.uconn.edu/cgi-bin/MAGIC_DBsearch2.pl?Geography=37800&Loc=0000]
Unit references	Rodgers, John, compiler, 1985, Bedrock Geological Map of Connecticut: Connecticut Geological and Natural History Survey, Hartford, Connecticut, 2 sheets, scale 125,000. Sevigny, J.H. and Hanson, G.N., 1993, Orogenic evolution of the New England Appalachians of southwestern Connecticut: Geological Society of America Bulletin, v. 105, no. 12, p. 1591-1605.
Geographic coverage	Fairfield - Hartford - New Haven