Ribbed moraine: Till-fabric analysis and origin

Abstract

The origin of a glacier-molded drift landform known as ribbed moraine and its relationship to fluted ground moraine and eskers are examined. The principal method of study is that of till-fabric analysis.Proximal fabrics indicate some up-glacier imbrication into the slopes, while distal fabrics are slope conformable. Fabrics from curved ridges as well as from the ribbed moraine–fluted ground moraine junctures appear to have directional components additional to that of regional glaciation.The recurrent ridges of ribbed moraine transverse to the direction of regional glaciation are deduced as having resulted from a reactivation of a retreating ice front leading to the bulldozing and piling up of proglacial debris which was finally overridden. The adjacent and sometimes superposed flutings are attributed to changes in flow patterns within the ice during and after overriding. Eskers examined appear to be post-ribbed moraine in age and therefore exerted no influence on the formation of ribbed moraine. The periodicity of the ribbed moraine is not time significant and is believed to be related to the thickness of ice and the quantity of proglacial debris available.