The Skippers Pluton

NaturalSkippersOutcrop

A natural outcrop of the Neoproterozoic Skippers granite exposed in the eastern Piedmont, Greenville County, Virginia. The exposure, at the edge of a clearcut, is composed of more-erosionally resistant core stones that are elevated above the soil. William & Mary geologist Ace Yuan atop the largest core stone. Photo by B.E. Owens.

Finding bedrock outcrop in the Piedmont of Southside Virginia can be challenging.  Much of the terrain is covered by soil and saprolite, and geologists interested in this region must search high and low for outcrop.  The image above illustrates a ‘good’ natural outcrop in the Piedmont, likely the result of a relatively resistant rock that is only weakly fractured.  These are core stones of unweathered bedrock that are separated by …

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Simplified geologic map of the Skippers pluton near Emporia, Virginia.  The pluton is covered, in part, by Cenozoic sediments of the Coastal Plain, and intrudes older metamorphic rocks

Simplified geologic map of the Skippers pluton near Emporia, Virginia. The pluton is covered, in part, by Cenozoic sediments of the Coastal Plain, and intrudes older metamorphic rocks.

Chopawamsic Gneiss

ChopGarbenSch

Complexly deformed gneiss in the Chopawamsic terrane near Cuckoo, Louisa County. Photo by C.M. Bailey

This exposure in a pasture near Cuckoo exposes a poly-deformed hornblende and plagioclase-rich gneiss. Foliation in the gneiss has been refolded.  Another interesting feature is the presence of garbenschiefer or “feather amphibolite.” This unusual texture is defined by stellate and featherlike hornblende clusters in the plane of foliation. Three amphibole species occur in this rock with hornblende and cummingtonite dominating the mafic layers and actinolite, as a late stage mineral overprinting the earlier fabric. The two-stage amphibole growth is evidence for two phases of metamorphism.

Gschiefer

Close up view of stellate hornblendes forming garbenschiefer.