New Zealand Journal of Geology and Geophysics abstracts
Forest burial by large rock avalanche in Miller Stream, Seaward
Kaikoura Range, New Zealand, c. 1700 years ago
R. J. Van Dissen
GNS Science
P.O. Box 30 368
Lower Hutt, New Zealand
D. G. Sutherland
USDA Forest Service
Redwood Sciences Laboratory
1700 Bayview Drive
Arcata, California 95521-6013, USA
R. J. Bowers
J. L. Redwine
Department of Geology
Humboldt State University
1 Harpst Street
Arcata, California 95521, USA
Abstract A forest buried at 1630–1730 cal. BP has
been exhumed by incision of Miller Stream, a tributary of Clarence
River that drains the steep southeast flank of the Seaward Kaikoura
Range, Marlborough, New Zealand. The paleoforest is exposed along
several hundred metres of the modern channel of the south branch of
Miller Stream, and comprises over 40 tree stumps in growth position
that are up to 2.5 m in circumference and 2 m in height. Just
over 2 km downstream, subhorizontal trees of the same age as the
paleoforest are buried by c. 14 m of a fining upward, poorly
sorted “debris flow” deposit containing clasts as large as 2 m
diameter. This deposit is capped by c. 8 m of thickly bedded
alluvial deposits. The aggradation that inundated Miller Stream, and
buried the forest, was probably caused by a large rock avalanche in its
headwaters with an estimated volume of c. 3.7 × 107 m3.
The triggering mechanism for the Miller Stream rock avalanche has yet
to be established; however, given its large size, the depth of its
source scar (≥100 m), and its close proximity (within 15 km)
to at least five major active faults (Jordan Thrust, Fidget, Kekerengu,
Hope, and Clarence Faults), we suggest that an earthquake may have been
the trigger.
Keywords rock avalanche; Seaward Kaikoura Range;
Marlborough
G05026; Received 16 June 2005; accepted 22 November 2005; Online
publication date 3 March 2006
New Zealand Journal of Geology & Geophysics, 2006, Vol. 49:
151–157
0028–8306/06/4901–0151 © The Royal Society of New Zealand 2006
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