HR: 0800h
AN: H51G-0449    [Abstracts]
TI: Offshore Extent of the Iceland Ice Cap During the Last Glacial Maximum Inferred from Multibeam Bathymetric Data and Sediment Cores.
AU: * Helgadottir, G
EM: gudrun@hafro.is
AF: Marine Research Institute, Skulagata 4, Reykjavik, IS-101 Iceland
AU: Brandsdottir, B
EM: bryndis@hi.is
AF: Institute of Earth Sciences, University of Iceland, Sturlugata 7, Reykjavik, IS-107 Iceland
AU: Geirsdottir, A
EM: age@hi.is
AF: Institute of Earth Sciences, University of Iceland, Sturlugata 7, Reykjavik, IS-107 Iceland
AU: Björnsson, H
EM: hb@raunvis.hi.is
AF: Institute of Earth Sciences, University of Iceland, Sturlugata 7, Reykjavik, IS-107 Iceland
AB: The insular margin of Iceland is incised by several major troughs, which mark the pathways of outlet glaciers during the last glaciations. Multibeam bathymetric data have revealed features of glacial erosion and sedimentation pertinent to the extent of the Iceland ice cap during the Last Glacial Maximum. Marginal moraines have been identified at the southern, western and northwestern edge of the insular margin. Furthermore, glacial erosion and sedimentation along the Kolbeinsey Ridge, North Iceland, indicates that the Iceland ice cap extended beyond 67°30'N. The ridge axis is made up of various types of seamounts, crater rows and hummocky ridges whereas older seamounts have been sculptured into roche moutonnées by glacial erosion. The far extent of the ice cap to the north is also supported by sediment studies on cores that have been retrieved from the troughs on the northern and northwestern part of the insular margin. Numerous smaller moraines exist closer to land marking stepwise retreat of the ice cap during deglacial times. Such moraines have been identified at 400-500 m depth within a 3-6 km wide, U-shaped valley along the western margin of the Kolbeinsey ridge (at 66°55'N) and within many of the costal fjords. Many of the offshore features resemble those known from land, such as streamlined bedrock features elongated in the regional direction of ice flow, eskers and subglacial meltwater channels together with erosional channels possibly formed by jökulhlaups. Extensive number of ice plough marks are revealed on bank areas and landslides on the marginal slope. Fluted surfaces and subglacially formed meltwater channels suggest formation underneath fast flowing, warm-based ice streams. These newly identified glacial features reveal new information on the spatial extent, dynamics and retreat of the Iceland ice cap during the last glaciation and deglaciation. Eustatic and isostatic contributions can be predicted from models of ice sheets and mantle rheology, which varies across the divergent plate boundary. Continuing study will focus on spatial and temporal variability of the combined effect of glaciation and isostacy as well as tectonic movements.
DE: 0730 Ice streams
DE: 1827 Glaciology (0736, 0776, 1863)
DE: 3021 Marine hydrogeology
DE: 3045 Seafloor morphology, geology, and geophysics
DE: 8416 Mid-oceanic ridge processes (1032, 3614)
SC: Hydrology [H]
MN: Fall Meeting 2005