Late Wisconsinan stratigraphy and chronology at Highlands, southern St. George's Bay, southwest Newfoundland

Abstract

Abstract This paper provides detailed sedimentological and chronological data of coastal exposures at Highlands in southern St. George's Bay, southwest Newfoundland. The Highlands section shows a coarsening upward sequence from mud to sand and gravel, and diamicton, and represents an ice-distal to ice-proximal glaciomarine environment, where sediment was introduced via a subglacial meltwater jet and deposited by underflow, current flow, debris flow, and overflow on a grounding-line fan. Diamicton forms a continuous unit along the top of the section, grading laterally from structureless to stratified, and has characteristics of subglacial, sediment gravity flow, and rainout depositional processes. At one site, a fossiliferous diamicton is interpreted to be deposited by rainout through a combination of suspension settling from meltwater plumes and ice rafting, with subsequent modification by sediment gravity flow on the fan slope. A radiocarbon date of 13,680±90 BP (Beta-120124) on paired shells from this diamicton is interpreted to represent the date of its emplacement. This date lies within the range of all other dates (∼13.1–14 ka BP) on marine organisms from sediments along the coast of southern St. George's Bay, and suggests that deposition of the diamicton was contemporaneous with sedimentation in all areas along the coast. Evidence to support a previously interpreted late-glacial readvance at ∼12.6 ka BP was not found.