GEOMORPHIC EVIDENCE FOR FAST ICE FLOW SOUTH OF HUNAFLOI, NORTH ICELAND

A geomorphic analysis of terrestrial landforms in the region south of Hunafloi, North Iceland, was conducted. The study area encompasses approximately 1200 km². Preliminary geomorphic analysis was performed using aerial photographs and Google Earth. Fieldwork included detailed measurements of striations and grooves carved into basaltic bedrock at 8 sites. The preservation of striations is somewhat remarkable given the fast weathering rate of basalt in Iceland. In many locations, the striations are best preserved where soil was recently removed (primarily for road construction). Approximately 30 grooves and 100 striations were measured. The length of the grooves ranges from 170 cm up to 1895 cm, with a mean length of 545 cm. The width varies from 10 cm up to 485 cm with a mean width of 75 cm. The depth of the grooves ranges from less than 1 cm up to 65 cm, with a mean depth of 15 cm. Ice flow paths are reconstructed using striation data, and there are no obvious crossing striations at the 8 sites. Drumlins, drumlinoid features, and possible Rogen moraines are observed at low elevations in the study area. It is interpreted that an ice stream filled the low, wide valleys in the study area and was constrained by mountainous regions adjacent to the low valleys. The mountainous regions contain alpine glacial features including u-shaped valleys, cirques, arêtes, horns, and hanging valleys. Cosmogenic radionuclide exposure dating is needed to constrain the timing of deglaciation, but basal radiocarbon dates of peat outcrops near sea level provide a minimum age of approximately 10 ka BP. Erosive, warm based ice covered this region, and geomorphic evidence supports the hypothesis that a region of fast ice flow was present south of Hunafloi during the last glacial maximum of Iceland.