HR: 0830h
AN: T51D-0186    [PDF]
TI: Late Quaternary displacement rate on the Alpine Fault and the timing of glacial advances in southwest New Zealand
AU: * Sutherland, R
EM: r.sutherland@gns.cri.nz
AF: Institute of Geological & Nuclear Sciences, PO Box 30-368, Lower Hutt, Wellington New Zealand
AB: Glacial features in eight river valleys crossing the southern end of the onshore Alpine Fault in South Island, New Zealand, are offset dextrally 435, 1240, or 1850 m and have only small vertical offsets. This is consistent with radiocarbon, surface exposure and speleothem evidence for extensive glaciation followed by retreat at c. 18, 58, and 79 ka. Glacial advances at c. 79 and 60 ka were higher and more extensive than 20 ka advances. Consideration of the three offset-age ranks yields an Alpine Fault slip rate with 95$%$ confidence limit (1.96 sigma) of 22.9 $\pm$ 3.3 mm/yr. Consideration of eight sites offset by about 435 m indicates the rank 1 offset has a 95$%$ confidence limit of 51 m, yielding a displacement rate and 95$%$ confidence limit of 24.2 $\pm$ 3.3 mm/yr for features of this age. Comparison with geologically determined uncertainties from each site shows that geological estimates of uncertainty in age and offset approximately correspond to confidence limits in the range 90-99$%$. 36.2 $\pm$ 3 mm/yr of total plate motion in southern South Island (NUVEL-1A) is being partitioned into 22.9 $\pm$ 3.3 mm/yr of Alpine Fault dextral strike-slip, 12 $\pm$ 5 mm/yr of heave on oblique dextral-reverse faults up to 80 km southeast of the Alpine Fault, and 5 $\pm$ 3 mm/yr of heave on reverse faults at peripheries of the plate boundary.
DE: 8107 Continental neotectonics
SC: Tectonophysics [T]
MN: 2003 Fall Meeting