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Outer Island Geology

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Outer Island Bedrock Geology

Stony Creek Pink Granite/Gneiss

Origins: Avalonian Terraine (Proterozoic to Permian 700 - 250 MYBP).

Characteristics: Stony Creek Granite Gneiss is Red to pink, unevenly medium to very coarse grained, variably foliated granite or granite gneiss, composed of oligoclase, K-feldspar, and quartz with minor biotite and magnetite, sporatic garnet (in foliated varieties), and local muscovite.

Commonly contains granite and pegmatite of Narragansett Pier type (and probably age). In much of area both granites occur as innumerable veins penetrating other units or as larger bodies full of inclusions of those units, which can be mapped through the bodies of granite.

Narragansett Pier Granite (Permian) - Pink to red, medium- to coarse-grained (commonly pegmatitic), generally massive (not gneissic) granite, composed of microcline, oligoclase, quartz, and biotite, and accessory muscovite and magnetite. Considerable associated pegmatite.

(photograph: S. Graves; text: USGS)

 

Also see Outer Island History...