23 Quaternary Geology (Posters) I

IMPACTS OF GLACIER SURGES AND JÖKULHLAUPS AT TWO LARGE TEMPERATE OUTLET GLACIERS: BERING GLACIER, ALASKA AND SKEIÐARÁRJÖKULL, ICELAND

Paper number: 23-1
Program: Technical Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

Although originating in distinctively different geologic settings, Bering Glacier and Skeiðarárjökull share a remarkably similar history of glacial events, and host unique characteristics uncommon to most other glacial systems. The Bering is the largest surge-type glacier in North America and consists of a 10 km wide main trunk glacier which feeds a 35 km wide piedmont lobe. Skeiðarárjökull exits the Vatnajökull ice cap and expands from a 10-15 km wide upland valley into a 23 km wide lobe which feeds one of the worlds largest active outwash plains. Both glaciers are temperate, occupy over-deepened basins, and are subject to periodic, short-lived, high-pressure jökulhlaups that interrupt or terminate surges, as well as storage-release jökulhlaups. Geomorphological and sedimentological evidence of subglacial and proglacial high-water-pressure events of common genesis are present at both glaciers. These glaciers and associated landform assemblages are of a proper scale to serve as analogues for lower latitude Quaternary ice-masses. Discharge of high pressure, subglacial meltwater created a distinctive suite of landforms and deposits consisting of: (1) sediment-packed, hydro-fracture networks developed in glacier ice and substrate materials, (2) large englacial eskers, (3) large supraglacial, sediment-floored, ice-walled canyons, and (4) ice-contact outwash deposits displaying ice block obstacle marks and kettle-hole pits. Push moraines, extensive areas of subglacial flutes and drumlinoid topography were produced by surge-related ice flow. The development of a series of large proglacial trenches at both glaciers has allowed the development of a peripheral, ice-marginal drainage system during ice retreat. Landform-sediment assemblages at Bering Glacier and Skeiðarárjökull, known to be associated with specific surges and jökulhlaups, provide a model for the interpretation of the sedimentary record of Quaternary ice sheet margins.