- Usage in publication:
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- Ponaganset Gneiss*
- Modifications:
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- Areal extent
- Age modified
- Revised
- AAPG geologic province:
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- New England province
Summary:
Ponaganset Gneiss is part of granite gneiss terrane of Rhode Island batholith and extends from RI and CT into MA. Assigned an age of Proterozoic Z based on similar character and intimate field relations with Proterozoic Z Hope Valley Alaskite Gneiss and Scituate Granite Gneiss. Rocks formerly mapped as Northbridge Granite Gneiss (herein abandoned) are reassigned to either Ponaganset Gneiss or Scituate Granite Gneiss (H.R. Dixon, 1978, unpub. data).
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
-
- Ponaganset Gneiss*
- Modifications:
-
- Overview
- AAPG geologic province:
-
- New England province
Summary:
Used as Ponaganset Gneiss of Proterozoic Z age. Consists of gneissic biotite granite containing megacrysts of microcline, and coarse streaks and patches of biotite. Equivalent in part to abandoned Northbridge Granite Gneiss.
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
-
- Ponaganset Granite Gneiss
- Modifications:
-
- Revised
- Overview
- Areal extent
- Dominant lithology:
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- Gneiss
- Granite
- Tonalite
- AAPG geologic province:
-
- New England province
Summary:
Sterling Plutonic Suite is here restricted to the Hope Valley terrane. (The Hope Valley together with the Esmond-Dedham terrane make up the Avalon superterrane of this report.) The Ponaganset Gneiss and the Ten Rod Granite Gneiss lie within the Esmond-Dedham terrane and are therefore removed from the Sterling. Ponaganset lies east of the Hope Valley shear zone and extends from RI into MA. [Apparently does not occur in CT.] Predominantly granite, ranges to tonalite. Gray to light gray, some pink, generally medium- to coarse-grained, but ranges from fine-grained to porphyritic. Alkali K-feldspar, plagioclase, quartz, and biotite are major minerals. The Ponaganset is interpreted as an intensely deformed phase of the Esmond Plutonic Suite. Strong lineation is defined by elongate aggregates of quartz and feldspar and trains of biotite and hornblende. Age is Late Proterozoic based on correlation with Northbridge Gneiss (MA), which has been dated at 557+/-4 Ma by Zartman and Naylor (1984).
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
-
- Ponaganset Gneiss*
- Modifications:
-
- Overview
- AAPG geologic province:
-
- New England province
Summary:
Assignment to Sterling Plutonic Suite not used here. Ponaganset Gneiss is largely found in RI, but masses of it project into MA. Intrudes Blackstone Group in RI (Quinn, 1971). In southern RI, Feininger (1963) demonstrated that Ponaganset is older than Hope Valley Alaskite Gneiss and appears to be oldest granite intrusive in Milford-Dedham terrane. Report includes geologic maps. [Papers presented as chapters in U.S. Geological Survey Professional Paper 1366 are intended as explanations and (or) revisions to MA State bedrock geologic map of Zen and others (1983) at scale of 1:250,000.]
Source: GNU records (USGS DDS-6; Reston GNULEX).
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 conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).