A cosmogenic dating study of landscape development in Central Otago, New Zealand
Abstract
The Quaternary structure and geomorphology of Central Otago are dominated by anticlines which form above buried reverse faults. Where some of these faults reach the surface on the flanks of the ranges, trenching demonstrates their Late-Quaternary activity. Earlier work on drainage patterns in the area provided information about the style, relative timing and growth of these anticlines. In particular, drainage diversion and the asymmetry of catchment areas indicated that, within one system of parallel ridges, the frontal South Rough Ridge formed later than the higher Rough Ridge, and propagated northwards. This qualitative analysis is confirmed by cosmogenic 10Be and 26Al ages of quartzites exposed by fault uplift. On the tip of South Rough Ridge we obtain an average uplift rate of 0.10-0.15 mm {yr}-1 and a lateral propagation rate of 1.0-2.0 mm {yr}-1 averaged over the last 450,000 yr (Earth and Planetary Science Letters, Vol. 195 pp 185-193, 2002). We suspect the actual exposure ages reflect the interplay between fault growth and the formation of terraces by a stream diverted by the growing anticline. We also obtain minimum 10Be exposure ages of 1Myr, which are made possible by the extremely low erosion rates in this area.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....3244B