Sub-ice shelf deposition during the late Devensian glaciation in western Ireland

Abstract

Glacigenic sediments preserved around the margins of Clew Bay, western Ireland, record deposition in a tidally-influenced, sub-ice shelf environment during the late Devensian glaciation (∼ 21–13 14C kyr). Thick, massive to normally-graded glacial diamictons (tills) are interbedded with laminated to massive silt and clay beds. These sediments interbed with each other on scales ranging from millimetres to metres in a generally shallowing-up sequence associated with a decrease in accommodation space. Isolated dropstones and a downward-going clastic dike are also observed. These structures and sediments reflect a waterlain environment with rhythmically-varying levels of water energy and sediment supply. Tidally-driven uplift and downdraw of a retreating ice shelf is a likely control on sedimentation patterns, and glacial dynamics, of this sensitive, Atlantic-facing ice margin.