Date of Award

Summer 1989

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Geology

Committee Director

G. Richard Whittecar

Committee Member

Dennis A. Darby

Committee Member

Joseph H. Rule

Call Number for Print

Special Collections LD4331.G4R98

Abstract

The west flank of the Blue Ridge near Sherando, Virginia (Augusta County) consists of many landforms including talus slopes, bedrock cliffs, boulder streams, colluvial slopes, residual knobs, and debris fans. The purpose of this study is to describe the geomorphic history of the area by understanding the spatial and temporal relationships between landforms on the hillslopes.

Boulder streams (maximum 30 m wide, 400 m long, 6.1 m thick) exhibit a gently dipping imbricated fabric and basal shear stresses of 0.1 to 0.4 bars.

Debris fans in Group L (lower) and Group U (upper) are distinguished by topographic position, degree of stream incision, peak clay percentages and iron concentration of Bt horizons, clast weathering rind thickness, and Munsell hue. ANOVA indicates that soils on upper fans are redder, contain more iron and clay, and contain clasts with thicker weathering rinds. Surfaces of Group U debris fans are interpreted to be older than the surfaces of Group L debris fans.

Boulder streams probably moved by solifluction and associated creep during successive cold climatic periods synchronous with Pleistocene glaciations elsewhere, and may have last moved during Wisconsinan time. Debris fans probably resulted from catastrophic rainfall events during interglacial periods. Upper debris fans ceased to accrete either when boulder streams halted the delivery of fine grained sediments by choking drainages, or when marginal streams pirated debris flows. Surfaces of upper fans may be Sangamonian age or older. Lower fans formed when Back Creek lowered base level by widening its valley and may be as young as Holocene.

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DOI

10.25777/rjpj-7d98

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