Glacial erosion: No stones unturned?
Is erosion of landscape under ice sheets significant or negligible? In the Arctic, it seems, it is both. I show evidence for cold-based margins of Greenland ice during the Last Glacial Maximum and for warm-based center at an unspecified time in the past. Take a walk through Nyeboe Land, in the north...
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Text |
| Language: | English |
| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.495.8875 http://quebec.hwr.arizona.edu/research/egu05-zreda-glacial-erosion.pdf |
| Summary: | Is erosion of landscape under ice sheets significant or negligible? In the Arctic, it seems, it is both. I show evidence for cold-based margins of Greenland ice during the Last Glacial Maximum and for warm-based center at an unspecified time in the past. Take a walk through Nyeboe Land, in the northwestern Greenland, and, as your feet sink in the soft till, your eyes are drawn to the mountains across the Nares Strait or to the margin of the Greenland ice sheet. But one of the most remarkable features in this landscape is one of the easiest to overlook – that this surface has two generations of erratics deposited at two different times. These erratics were dated by cosmogenic 36Cl. One group of boulders, exclusively red granites, was deposited 27±2 ky ago (ky = 1000 years); the other, exclusively gray limestones, was deposited 8±1 ky ago. The small spread of individual boulder ages strongly suggests that these erratics have remained in the same position since their deposition. And the age difference suggests that there were two ice-sheet advances: the first involved a large, regional ice and wide dispersal of granitic erratics from the interior of Greenland; the second glaciation was smaller and dispersed material from the local bedrock. The |
|---|