Sedimentology of the Central Region of the Brampton Esker: An Empirical Test of an Esker Sedimentation Model

Abstract

<p> Eleven facies types, distinguished on the basis of internal grain size and primary sedimentary structure, were obsereved at the central region of the Brampton esker. These facies were then used to perform an empirical test of H.C. Saunderson's model of eskerine sedimentation for this part of the esker. Primarily, the vertical sequence of facies consisted of: (a) cross-bedded gravel representing the front of a prograding delta; (b) delta-front sands that are poorly sorted and characterized by massive structure and parallel lamination; (c) cross-bedded coarse sand recording the migration of sand waves across the topset; (d) trough-shaped cross-laminae of fine sand indicating current ripple migration on top of the sand waves; (e) draped lamination grading into cross-laminae of fine sand showing stoss-side preservation as the ratio of suspended sediment to bed load decreased; and (f) thick layers of silt and clay deposited in stagnant water conditions brought about by delta abandonment. Cut-and-fill structures were also present, giving evidence of distributary channels traversing the delta. </p> <p> Saunderson's model adequately explains the origin of sediments in the central region of the esker, but some modifications were made on the basis of new evidence revealed by a recently uncovered exposure. </p> <p> The sedimentary enviroment was that of a delta which consisted of a topset network of distributary channels prograding into a glaciolacustrine enviroment.