New Zealand Journal of Geology and Geophysics abstracts
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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