Discrete debris accumulation


Discrete debris accumulation is a non-genetic term in mountain glacial geology to aid identification of non-lithified sediments on a valley or mountain slope or floor. It is intended that the debris accumulation is discrete such that it can be mapped, in the field and/or from aerial or satellite imagery. The origin or formative process may well not be known clearly or be changed by subsequent investigators it is advisable to have a non-genetic field reference so that discussion can then be used to ascertain, if possible, the origin. Mountain areas may currently have glaciers or have had glaciers or be subject to forms of periglacial activity. A moraine would be an easily identified DDA as would an esker. Although scree is generally easily identified and mapped, these deposits may be modified by ice, avalanches or downlope movement to create essentially new landforms. Many small slope failures and landslides can give the appearance of moraines or protalus ramparts on slopes. After mapping as a DDA, further investigation might draw light on the origin of the feature.
The term was apparently first used by Sven Lukas for a very specific feature in Svalbard.
Independently, it was suggested in the literature in W. B. Whalley and subsequently in Whalley, 2012 as relating to the basic definition and usage as above. This book chapter provides several photographic examples.
The 'cirque infills' described by Hätterstrand et al. in the Khibiny Mountains, Kola Peninsula could be described as discrete debris accumulations, although their origin is postulated by these authors as being moraine remnants of an ice sheet pushing into these cirques rather than as rock glaciers formed within the cirques.