New Zealand Journal of Geology and Geophysics abstracts

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Resedimentation of the 1.8 ka Taupo ignimbrite in the Mohaka and Ngaruroro River catchments, Hawke's Bay, New Zealand

B. Segschneider*

C. A. Landis

J. D. L. White

Department of Geology
University of Otago
P.O. Box 56
Dunedin, New Zealand

C. J. N. Wilson

V. Manville

Institute of Geological & Nuclear Sciences
Wairakei Research Centre
Private Bag 2000
Taupo, New Zealand

*Present address: Institute of Geological & Nuclear Sciences, Wairakei Research Centre, Private Bag 2000, Taupo, New Zealand.

Abstract   Deposition of the 1.8 ka Taupo ignimbrite in the Hawke's Bay buried parts of the Ngaruroro and Mohaka River catchments beneath up to 40 m of loose pyroclastic debris. Re-establishment of the two river systems led to the remobilisation of the loose debris and followed similar patterns in both catchments. An initial period of laharic remobilisation and formation of lahar-deposit-dammed lakes was followed by two phases of fluvial remobilisation. During the first of these, streams were shallow and ephemeral to perennial, with sediment-laden flash-floods eroding headwards through valley-ponded primary pyroclastic and laharic deposits. With gradual re-establishment of vegetation, the sediment:water ratio decreased, and braided rivers with deeper, more stable channels became dominant.

Keywords   Taupo ignimbrite; pumiceous deposits; fluvial sedimentation; geomorphology; volcaniclastics

Received 24 November 2000; accepted 7 September 2001
New Zealand Journal of Geology & Geophysics, 2002, Vol. 45 : 85–101
0028–8306/02/0085 $7.00/0 © The Royal Society of New Zealand 2002

PDF file of entire paper: Print-quality (1392K)

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