HR: 1330h
AN: PP32B-0286    [PDF]
TI: Glacial Features on the Northern Insular Margin of Iceland
AU: * Helgad\'{o}ttir, G
EM: gudrun@hafro.is
AF: Marine Research Institute, Sk\'{u}lagata 4, Reykjav\'{\i}k, 101 Iceland
AU: Brandsd\'{o}ttir, B
EM: bryndis@raunvis.hi.is
AF: Science Institute, Univ. of Iceland, Haga, Hofsvallagata 53, Reykjav\'{\i}k, 107 Iceland
AU: Detrick, R S
EM: rdetrick@whoi.edu
AF: Woods Hole Oceanographic Institution, 360 Woods Hole Road, Woods Hole, MA 02543 United States
AU: Driscoll, N
EM: ndriscoll@ucsd.edu
AF: Scripps Institution of Oceanography, Univ. of Calif., 8602 La Jolla Shores Drive, La Jolla, CA 92037 United States
AB: The iceberg scoured insular margin of Iceland is incised by several major fjords which mark the pathways of major outlet glaciers during recent glaciations. New Simrad EM300 multibeam bathymetric and Chirp sonar data from the northern insular margin have revealed glacial and glaciotectonic formations some of which, to our knowledge, have not been previously recognized. The iceberg scoured bank areas are mostly devoid of loose sediments which has accumulated within the fjords. Glacial erosion along the Kolbeinsey Ridge indicates that the Iceland ice cap extended beond 67$\deg$N during the last glacial maximum. Multiple marginal moraines exist at 400--500 m depth within a 3--6 km wide, U-shaped valley along the western margin of the ridge (at 66$\deg$55'N). The region east of the ridge is dominated by large volcanic complexes which bear the marks of glacial erosion, however, volcanic deposits from postglacial eruptions have blanketed all glacial features in this region. Scoured bedrock surfaces and eskers reflect the direction of two major outlet glaciers, into Skagafj\"{o}rdur-Skagafjardardj\'{u}p and Eyjafj\"{o}rdur-Eyjafjardar\'{a}ll. The region between 66$\deg$20'N and 66$\deg$35'N in Eyjafjardar\'{a}ll is dominated by a system of a $\Lambda$-shaped highly reflective (till?) ridges, which are characteristically up to 1 km long and 300--500 m wide and open towards the presumed glacial flow. The northernmost ridges strike NNE-SSW, parallel to a 10 km long lateral moraine, which most likely separated the two main outlet glaciers in this region, i.e.\ from Skagafj\"{o}rdur and Eyjafj\"{o}rdur. Further south, they change direction gradually, along with the fjord curvature. The $\Lambda$-shaped ridges most likely represent glaciotectonic features formed during repeated glacier advances. They are not drumlins as drumlins generally increase in volume up-glacier but the ridges down-glacier. Instead they represent some sort of composite ridges intervening depressions conforming to the general shape of the glacier margin that produced them. A highly crevassed, advancing glacier snout could generate such formations from bulldozed basal till, making these ridges a new? form of lateral crevasse-squeeze ridges or push moraines. Both transverse and lateral basal crevasse-fill ridges have been observed with surging glacier margins in Iceland but none with similar pattern as those within Eyjafjardar\'{a}ll.
DE: 0930 Oceanic structures
DE: 1625 Geomorphology and weathering (1824, 1886)
DE: 1827 Glaciology (1863)
DE: 3022 Marine sediments--processes and transport
DE: 4267 Paleoceanography
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting