Formation of a pronival rampart on sub-Antarctic Marion Island

• Published in: Antarctic Science
• Main Authors: Hedding, David W., Sumner, Paul D., Holness, Stephen D., Meiklejohn, K. Ian
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2007
• Subjects: Antarctic; Antarc*; Antarctic Science; Marion Island
• Online Access: http://dx.doi.org/10.1017/s0954102007000582; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0954102007000582

Abstract The formation of a pronival (protalus) rampart on sub-Antarctic Marion Island is investigated. Morphological attributes show debris at the angle of repose on the rampart's proximal slope and at a lower angle on the distal slope. Relative-age dating, based on the percentage moss cover and weathering rind thickness of the clastic component, indicates accumulation mainly on the proximal slope and rampart crest, implying upslope (retrogressive) accumulation. This contrasts with a previously published model for pronival ramparts, which proposes rampart growth by addition of material to the distal slope. Development of the Marion Island rampart is suggested to result from the control exerted by a relatively low-angled surface and a shrinking snowbed. A small debris step formed on the proximal slope appears to be a response to decreased snowfalls due to changing climate over the last c . 50 years. Growth rate of the rampart is considered to be variable during the Holocene in response to changes in climate and debris supply.