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RHODE ISLAND Jerimoth Hill 7 ½’ quadrangle: East Killingly, CT-RI Providence County Private land. (check www.Highpointers.org for access information)
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Metamorphic (metamorphosed igneous) 812 ft (247 m) |
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| The boulder at Jerimoth Hill is the highest point. (May 2005) | Closer view of the gneiss boulder, cut by an aplite dike. |
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Bedrock: Esmond Igneous Suite |
Late Proterozoic |
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Bedrock is not exposed at the highest point, but the granitic gneiss boulder there, as well as blocks along Rt.101, provide a close look at the rock. Formerly mapped as the Ponaganset gneiss, the rock is light to dark gray, fine to coarse porphyritic and porphyroblastic gneiss, commonly foliated, with oval biotite lineation splotches. The main minerals are microcline, plagioclase, quartz, biotite, plus or minus hornblende and muscovite. The Esmond Suite is part of the Avalon Terrane, which was accreted to North America in the Late Paleozoic. The highpoint lies about two miles east of a right-lateral strike-slip fault that separates the Esmond-Dedham subterrane from the Hope Valley subterranes to the west, all part of Avalon.
A side trip to see 30-foot tall ledges of Ponaganset gneiss makes a nice addition to the rather short trek to the highpoint. Take Rhode Island Rt. 94 north from Rt.101 to the western part of Durfee Hill Wildlife Management Area. Vertical ledges can be seen along a trail west of 94, and a loop trail east of 94 explores moraine topography around a small pond. Foliation and lineation in the gneiss indicates intense shearing during deformation.
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| Doug Smith at the cliff of gneiss. |
Closer view, showing lineated surfaces.
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Surficial Geology: Thin glacial till overlying bedrock.
Soil Series: Gloucester stony fine sand loam: Light grayish-brown to yellowish-brown in the subsoil, well drained, acidic, formed on granitic glacial till.
Selected References: Moore, George E., 1983, Bedrock geological map of the East Killingly quadrangle, Connecticut and Rhode Island: U.S. Geological Survey Quadrangle Map GQ-1571. Shearin, A.E. and others, 1943, Soil Survey of Providence County, RI: U.S. Department of Agriculture.
Other suggested sources of information: |
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