Date of Award

Spring 1997

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Geology

Committee Director

G. Richard Whittecar

Committee Member

J. L. Leftwich

Committee Member

Dennis A. Darby

Call Number for Print

Special Collections LD4331.G4 Z37

Abstract

Within four study areas in the Blue Ridge Mountains of Virginia, boulder streams formed by periglacial processes carpet the bottoms of most high-altitude first-order valleys. The geomorphic indicators of periglacial formation in these long, linear accumulations of bouldery colluvium - the presence of vertical clasts, gradational upper contacts with talus deposits, confinement within valleys, and hump-like cross sectional profiles - were present in all areas mapped and in most individual boulder streams. The minimum critical elevation for boulder stream formation increases from north to south across Virginia, from 150 m in elevation in northern Virginia to 1500 m in southwestern Virginia. Thus, as predicted by the periglacial hypothesis, boulder streams should be expected in many small high-altitude valleys above the elevation critical for boulder stream formation.

The presence of near vertical clasts found in all boulder streams mapped implies that this characteristic is useful in differentiating periglacial boulder streams from other colluvial debris. Statistical analysis on the distribution of the near vertical clasts suggests these features are randomly dispersed within the boulder stream. Rose diagrams reveal a large number of the near vertical clasts oriented subparallel, and a lesser number perpendicular, to the main axis of the boulder stream. Differential flow velocities within the boulder stream could produce these preferred orientations.

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DOI

10.25777/hc5t-1b84

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