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Regoliths of the middle-Atlantic Piedmont and evolution of a polymorphic landscape

Southeastern Geology

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Abstract

The regolith overlying the alumino-silicate rocks of the middle-Atlantic Piedmont Province consists primarily of saprolite with a thin veneer of diamictons of colluvial origin. Thickness and distribution of the saprolite is related to landform and lithology. For example, on uplands isovolumetric weathering of the Loch Raven Schist produces saprolite averaging 55 ft (17 m) thick. On Port Deposit Gneiss, saprolite beneath uplands averages 42 ft (13 m) in thickness. The saprolite results from the reaction of alumino-silicate rocks with through-flowing groundwater. Chemical weathering of the rock results in clay and resistate minerals, residual rock layers, corestones, and pinnacles. Surface erosion of saprolite with quartzite and metagraywacke residual layers may produce a 'washboard' topography. Surface erosion of a metagabbro saprolite containing corestones and pinnacles results in a surface with lag deposits of corestones and emergent pinnacles. The diamicton material comes from the underlying saprolite, weathered rock and bedrock. Generally, diamictons are thinner on uplands and upper slopes, and thicker at the base of slopes and in hollows and gathering areas of first-order streams. The saprolite and colluvium reflect response of geomorphic processes (chemical weathering, fluvial incision, and periglacial processes) to rock lithology and landscape. The modifications to the landscape have been driven by neotectonic crustal warping and alternating periglacial-humid temperate climates. Altogether these varied interactions have resulted in a Holocene polymorphic landscape.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Regoliths of the middle-Atlantic Piedmont and evolution of a polymorphic landscape
Series title:
Southeastern Geology
Volume
39
Issue:
3-4
Year Published:
2000
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
199
Last page:
222
Number of Pages:
24