ABSTRACT: Faonnement du modele drumlinoide par deux ecoulements glaciaires successifs au sud-ouest de Montreal [Moulding of drumlinoid landforms by two consecutive ice flows southwest of Montreal (Quebec)].

CGRG Bibliography of Canadian Geomorphology
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Abstract

Landforms and deposits of Huntingdon plain, southwest of Montreal, reveal a complex glacial history. Of that glacial heritage, we have considered elongated land-forms nearly parallel to the St. Lawrence River axis. The core of these drurnklin-like (drumlinoids) forms is a fissile and compact lodgement till, occasionally covered by a melt-out till or by coarse littoral material of probable drift ice (ice-rafted) origin. These subglacial landforms were first moulded by an important ice flow from the northeast moving up St. Lawrence Lowlands south-westwards. This is shown by indicator stones of appalachian origin, but also by till fabrics and micro-forms of glacial erosion both oriented northeast-southwest. Thus, the initial part of their genesis makes the drumlinoids more similar to drumlins than to subglacial transverse landforms like Rogen or ribbed moraines. Characteristics of the lodgement till indicate than the drumlinoids were constructed by accumulation processes, but that erosion processes responsible for an important fraction of the till were in action near by. The first ice flow from the northeast was followed by a second one from the northwest or the north without deglaciation. Even if this second ice flow let its traces all over the studied area, the initial glacial morphology was only slightly modified. The entire glacial portion of the drumlinoids belongs to the same Late Wisconsinan glacial Stage. The last important phase in the genesis of the drumlinoids was accumulation of drift ice sediments in the end of Champlain Sea episode which altered their crest but mainly their southeastern side.

Bibliography of Canadian Geomorphology