New Zealand Journal of Geology and Geophysics abstracts
Structural evolution and landscape development of a collapsed transpressive
duplex on the Hope Fault, North Canterbury, New Zealand
J. DYKSTRA EUSDEN JR1
JARG R. PETTINGA
JOCELYN K. CAMPBELL
Natural Hazards Research Centre
Department of Geological Sciences
University of Canterbury
Private Bag 4800
Christchurch, New Zealand
email: deusden@bates.edu
1Present address: Department of Geology, Bates College, Lewiston,
Maine, 04240, U.S.A.
Abstract This study examined the transpressional Conway
segment of the Hope Fault in North Canterbury, the fastest moving fault of the
Marlborough Fault Zone in northern South Island of New Zealand, in an attempt
to reconstruct, via air photograph interpretation, detailed field mapping, and
theoretical constraints, the styles of structural geometry of the late
Quaternary deformation. We relate the evolving landscape to the development and
modification of this fault in an active tectonic setting.
The section of the fault zone studied is a 13 km long, 1.3 km wide,
asymmetric transpressional reverse fault duplex, bounded to the southwest by
the Lottery River and to the northeast by the Mason River, which tapers down to
a single fault trace to the northeast. Between the bounding faults of the
duplex are approximately 100 subsidiary fault scarps that initially formed an
imbricate set of footwall propagating reverse/thrust faults. These faults
became inactive and topographically unsupported when younger footwall
propagating reverse faults migrated northeast along the main trace of the Hope
Fault as the duplex also migrated to the northeast. The unsupported duplex
structurally collapsed back into the dilating fault zone, causing reversal of
slip on the imbricate reverse faults so that they became normal faults. As the
duplex collapsed, the adjacent hanging wall was uplifted triggering
landsliding, rapid incision by streams, formation of large alluvial fans, and
minor normal fault gravity collapse structures. The footwall block outside the
duplex became rapidly incised by streams and experienced widespread topographic
slumping and associated structurally controlled, shallow-level ridge renting.
Stream dissection of flights of late Pleistocene aggradation/degradation
surfaces also occurred at this time, leaving remnant flat-topped hills between
the dissected and slumped valleys. Our analysis of the interrelationships
between the structural geology and the landscape over time is a new approach
for the Hope Fault and reconfirms the necessity of integrating detailed
structural geology with geomorphology in areas of active tectonism.
Keywords Hope Fault; New Zealand; transpressive duplex;
landscape evolution
New Zealand Journal of Geology & Geophysics, 2000, Vol. 43:
391-404
0028-8306/00/4303-0391 $7.00/0 (c) The Royal Society of New Zealand
2000
PDF file of entire paper: medium quality (3202K); (scanned from paper original: notes about this process)
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