Influence of Clast Axial Ratio on Macrofabric Strength in Periglacial Colluvium

Abstract

Samples of fabric data collected from periglacial solifluction lobes in central Alaska show a systematic, positive relation between clast axial ratio and fabric strength. Samples composed of clasts with low a:b axial ratios have relatively low fabric strength. Restricting sampling to clasts with axial ratios of 1.5:1 or higher increases fabric strength and decreases its variability. To enhance comparability between fabric studies and the utility of fabric interpretation, sampling should be restricted to clasts with relatively large (Ն 1.5:1) axial ratios.

Fabric variability associated with periglacial mass-wasting at Eagle Summit, Alaska

“…Krü ger (1970) and Kjaer and Krü ger (1998) discussed the relation between clast size and fabric strength, wherein longer clasts in glacial till showed a stronger preferred parallel orientation. Yamamoto (1989) and Millar and Nelson (2003) have illustrated a strong relation between the average clast axial ratio and fabric strength in periglacial colluvium. The factors with the greatest explanatory power in this study are those associated with average clast size (factor 1), and clast platyness (factor 2), which correspond to those discussed by other workers (see Table 1).…”

“…Clast axial ratio Increasing downslope-parallel orientation with increasing axial ratio. (Holmes, 1941;Lundqvist, 1949;Yamamoto, 1989;Bertran, 1993;Kjaer and Krü ger, 1998;Millar and Nelson, 2003) Combined clast properties of size, prolateness and within sample a:b variation explain up to 16% of fabric strength; 13% of fabric shape.…”

Nuevos datos sobre el origen del Lago de la Baña (Sierra de la Cabrera, NO de España) a partir del análisis geomorfológico y sedimentológico

“…En cada caso se tomaron los datos de dimensión, orientación e inclinación del eje mayor, índice de desgaste y litología de 50 clastos, seleccionando preferentemente aquellos con una relación entre el eje mayor y el eje menor de al menos 1,5, ya que se adaptan mejor a las direcciones de flujo de los agentes sedimentarios (Millar y Nelson, 2003).…”