Geo‐botanical evidence of late quaternary mass wasting in block field areas of Virginia

Abstract

Abstract Studies of block fields at Massanutten Mountain, Virginia, document and provide information on the magnitude and frequency of mass movement on these coarse‐grained slopes. Block fields, which traditionally have been considered relicts of Pleistocene climate, occur on and downslope from resistant Massanutten Sandstone in Passage Creek basin. Slopes are strewn with boulders and vegetative cover on the open block fields is absent to sparse. Several block fields were investigated for evidence of recent movement using the degree of lichen growth, differences in block weathering, and rock‐fall damaged trees. Temporal and spatial aspects of geomorphic processes can be inferred through dendrogeochronology. Corrasion scars and stem ages infer a minimum age for a geomorphic or hydrologic event. High flows on Passage Creek coincided with tree‐ring determined dates of block‐field movement. Although, Pleistocene periglacial climate may have facilitated original formation of block fields, some block fields now continue to spread downslope during intense runoff events. Present block‐field mass wasting may be the principal erosional process in these areas of resistant rock.