New Zealand Journal of Geology and Geophysics abstracts

---

The impact of episodic fault-related folding on late Holocene degradation terraces along Waipara River, New Zealand

ANDREW NICOL

Institute of Geological & Nuclear Sciences Ltd
P.O. Box 30 368
Lower Hutt, New Zealand

JOCELYN K. CAMPBELL

Department of Geological Sciences
University of Canterbury
Private Bag 4800
Christchurch, New Zealand

Abstract  The Waipara River flows eastwards through growing folds in the tectonically active foothills of New Zealand's Southern Alps. In the middle Waipara region, flights of degradation terraces are widespread and rise to 55 m above river channels. Ages of terrace surfaces and paleoearthquakes on four faults are constrained by radiocarbon samples and weathering-rind dates from surface cobbles of Torlesse Group sandstone. Terrace ages indicate rapid incision (c. 30-100 mm/yr) of Waipara River and three tributaries during the late Holocene. Cumulative-incision curves suggest a 15-25 m lowering of regional base level over the last thousand years and an additional 20-25 m of local incision 200-600 yr BP along Waipara River where it crosses Doctors Anticline. Rapid river incision was strongly influenced by rock uplift on the anticline associated with fault rupture during an earthquake 300-400 yr BP. From incision data we infer that the earthquake was preceded and followed by aseismic fold growth. Tectonic uplift during folding was probably, at most, one-third of local river incision; this discrepancy may relate to the short sample period and to locally elevated stream erosive power due in part to a reduction in floodplain width.

Keywords  active folds; uplift; downcutting; fluvial processes; paleoseismology; aseismic; weathering rind; radiocarbon; Waipara River; Canterbury; New Zealand

New Zealand Journal of Geology & Geophysics, 2001, Vol. 44: 145-156

0028-8306/01/4401-0145 $7.00/0 (c) The Royal Society of New Zealand 2001

PDF file of entire paper: medium quality (2236K); (scanned from paper original: notes about this process)

---

This year's abstracts | Journal home page | All abstracts | Publishing home page