The Geology of Delaware

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Outcrop Bd21-a: Boulder Field at Brandywine Creek State Park

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Rock Outcrop Bd21-a: Boulder Field at Brandywine Creek State Park

In the patch of woods north of the upper parking lot in Brandywine Creek State Park are large outcrops of amphibolite. The outcrops are rounded from exfoliation, and are black with few structural features. The mafic hornblende grains are elongated parallel to a few thin felsic bands. This lineation strikes east-west and dips to the north. These boulders are located on the northwest facing slope of the valley and are probably a paraglacial feature left over from a colder period in Delaware's geologic past.

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Rock Outcrop Bd21-a: Boulder Field at Brandywine Creek State Park
Rock Outcrop Bd21-a: Boulder Field at Brandywine Creek State Park
Rock Outcrop Bd21-a: Boulder Field at Brandywine Creek State Park
Rock Outcrop Bd21-a: Boulder Field at Brandywine Creek State Park