VT -- Putney's Geological Grimace EarthCache
VT -- Putney's Geological Grimace
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Logging Requirements:
- GC#
- Based on the definitions of "fold" and "fault" you should see evidences of "folds" here. How many are there at GZ and are they anticline or syncline? Would you consider them "major" (larger than a mobile home) or "minor"?
- based on the pile of shiny layered rock at your feet surrounding GZ, let's make some observations:
- Metamorphic rocks fall into two categories: foliated (layers visible) and non-foliated. Which are these?
- Further, are they "light" or "dark"?
- finally, are they shiny/pearly with a crinkly foliation or shiny "stack of paper" that goes 'tink' when you strick something hard against it (it sounds hollowish).If the answer is foliated, dark, and crinkly foliation that would be phyllites If the answer is foliated, light, and shiny with a 'tink' than that is slate.
In the area surrounding the Putney exit, you are crossing the axis of an anticlinal (like a hill with edges folded downward) folds.
Thanks to these folds, lots of Ordovician slates and phyllites from the core of the formation are exposed. Some geologists say that the rocks you can see here resemble those of the Littleton formation, but lack the white quartzite interlayers. In fact, the lack of quartzite (according to USGS) has caused geologists to define the rocks in the area as Putney Volcanics Formation, possibly once connected to the Standing Pond Volcanics (and thus the North American Plate) rather than the Littleton formation (and thus part of pre-ancestral African plate).
Between Putney and Bellows Falls (10 miles north) are a whole series of roadcuts visible from the interstate, that are all part of a single anticlinal fold that trends from north to south.
At GZ you can see both slate and phyllite. Slate is low-grade metamorphic formed from shale and characterized by flat cleavage plates. Phyllite low-grade fine grained schist characterized by a pearly luster on split layers that are generally less regular than slaty cleavage.
Definitions:
Fault -- Rock fracture in the earth's crust caused by movement of one mass of rocks against another.
Fold -- a rock deformation manifested by real or apparent bending of originally planar layers
References:
VanDiver, Bradford B. Roadside Geology of Vermont and New Hampshire. Missoula: Mountain Pub., 1987. Print.
"Putney Volcanics." USGS. N.p., n.d. Web. 25 Jan. 2013.
Additional Hints
(Decrypt)
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