EVIDENCE FOR EXPANDED MIDDLE AND LATE PLEISTOCENE GLACIER EXTENT IN NORTHWEST NELSON,NEW ZEALAND |
| |
| Authors: | GLENN D THACKRAY JAMES SHULMEISTER DAVID FINK |
| |
| Institution: | 1. Idaho State University, Pocatello, Idaho, USA;2. University of Canterbury, Christchurch, New Zealand;3. Australian Nuclear Science and Technology Organisation, Sydney, New South Wales, Australia |
| |
| Abstract: | The extent of Late Quaternary glaciation in the northwest Nelson region of New Zealand has traditionally been regarded as minor, with small‐scale valley glaciation in confined upland reaches. New geomorphological evidence, including moraines, kame terraces, till‐mantled bedrock and outwash terraces, indicate that greatly expanded valley glaciers flowed into the lowland valley system at the mouths of the Cobb‐Takaka and Anatoki drainages. The timing for this ice advance into lowland valleys is constrained by lowland landform characteristics and a single cosmogenic exposure age, suggesting Late and Middle Pleistocene ice expansion, respectively. Evidence for expanded upland ice on the Mount Arthur Tableland and adjacent areas includes trimlines, boulder trains and roche moutonées. Two cosmogenic exposure ages on upland bedrock surfaces suggest that major ice expansion occurred during MIS 3 and/or 4, while previously published exposure dating from Cobb Valley suggests large MIS 2 ice expansion as well. The inferred, markedly expanded ice left little or no clear geomorphic imprint on the Cobb–Takaka Gorge, and required temperature depression of 4–6°C with near‐modern precipitation levels. |
| |
| Keywords: | glaciation New Zealand paleoclimatology geomorphology |
|
|
