Glacial Processes and Sediments

Abstract

Glaciers progressively modify the landscape through a complex spatial and temporal mosaic of processes, and they produce majestic landscapes that contain a remarkable range of sediments and landforms. As glaciers covered as much as 30% of the Earth's surface during maximum glacial phases in the present geological period, understanding glacial sedimentary processes and deposits is of high importance. This article provides an introduction to these processes and deposits. Glacial sediments are categorized as either primary or secondary sediments. Primary glacial sediments are those that have been deposited by processes operating only at the ice-bed interface (i.e. subglacial traction till and glaciotectonite). Conversely, secondary glacial sediments are those that have been remobilized and reworked by a variety of nonglacial processes (e.g. debris flow deposits, turbidites, fluvial bedforms). The sedimentary processes active in glacial environments result in the creation of a wide variety of glacial sediment-landform associations (sediments that have a surface expression). These associations are deposited in subglacial (e.g. drumlins), ice-marginal (e.g. ice-marginal moraines), supraglacial (e.g. kame mounds), proglacial (e.g. sandar, or glacial outwash) and subaqueous (e.g. grounding-line fans) depo-centers. Owing to the bewildering range of both glacial and nonglacial sedimentary processes operating in glacial settings, glacial depositional environments are undoubtedly the most complex of all sedimentary systems.