- Usage in publication:
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- Hope Valley Alaskite Gneiss*
- Modifications:
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- Areal extent
- Age modified
- AAPG geologic province:
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- New England province
Summary:
Hope Valley Alaskite Gneiss is continuous from RI and CT into MA in Rhode Island batholith. Recent radiometric age determinations indicate a Proterozoic Z age (Day and others, 1980; Hermes and others, 1981) rather than previous age of Mississippian(?) or older.
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
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- Hope Valley Alaskite Gneiss*
- Modifications:
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- Overview
- AAPG geologic province:
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- New England province
Summary:
Used as Hope Valley Alaskite Gneiss of Proterozoic Z age. Consists of mafic-poor, locally muscovitic gneissic granite. Gradational with Scituate Granite Gneiss.
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
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- Hope Valley Alaskite Gneiss
- Modifications:
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- Overview
- Dominant lithology:
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- Gneiss
- Alaskite
- AAPG geologic province:
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- 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. The Ponaganset is interpreted as an intensely deformed phase of the Esmond Plutonic Suite. The Sterling, as defined here, includes only the Hope Valley Alaskite Gneiss and the Potter Hill Granite Gneiss. These rocks intrude the Plainfield Formation and the Waterford Group in southeastern CT and western Rhode Island and are Late Proterozoic in age. Alaskite gneiss of the Hope Valley is mainly pink or light tan, but also gray, medium-grained, and lineated with aggregates of smoky quartz. Distinguished from the Potter Hill by its low biotite content. Magnetite common. According to Hermes and Zartman (1985), presence of disoriented metasedimentary xenoliths demonstrate intrusive nature.
Source: GNU records (USGS DDS-6; Reston GNULEX).
- Usage in publication:
-
- Hope Valley Alaskite Gneiss*
- Modifications:
-
- Overview
- Geochronologic dating
- AAPG geologic province:
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- New England province
Summary:
Late Proterozoic Hope Valley Alaskite Gneiss occurs as one of several plutonic rocks in Milford antiform. Forms tabular masses along west side of Rhode Island anticlinorium from southern RI and eastern CT to northwestern RI; flanks west side of Milford anticlinorium and terminates at north end of anticlinorium in MA. Color is light pink to tan. Intrudes Plainfield Formation in CT and Blackstone Group rocks in RI. Isotopic age of 630 Ma by U/Pb methods on zircon is reported by Zartman and Naylor (1984) from a sample in MA. Age of 601 +/-5 Ma by U/Pb methods on zircon is reported by Hermes and Zartman (1985) from a sample in RI. 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 ([ ]).