New Zealand Journal of Geology and Geophysics abstracts
Sea caves, relict shore and rock platforms: evidence for the tectonic stability
of Banks Peninsula, New Zealand
ADRIAAN A. BAL
Department of Geological Sciences
University of Canterbury
Private Bag 4800
Christchurch, New Zealand*
*Present address: Z & S (Asia) Ltd., 46 Ord St., West Perth 6005, WA
Australia.
Abstract Well developed but partially exposed shore platforms
at 6-8 m above mean sea level (m.s.l.) on the southwestern flanks of Banks
Peninsula have been considered previously as evidence for either general
tectonic stability or differential subsidence of the peninsula. These platforms
probably formed during an interglacial high sea-level stand,
c. 120 000 yr ago or earlier. Banks Peninsula has been assumed
to be differentially subsiding, since comparable platforms have not been
identified on the northern flanks, and adjacent late Quaternary marine and
fluvial sediments of the Canterbury Plains are unequivocally subsiding.
However, an alignment of coastal erosional features at Cave Rock and Sumner
Head, Christchurch (northwestern flank of Banks Peninsula), may represent a
relict shore platform 5-6 m above m.s.l.
These erosional features are interpreted to be correlatives of the platforms
described on the southwestern flank, and therefore suggest Banks Peninsula is
not differentially subsiding. By implication, wide (kilometre-scale) subsurface
(c. -50 to -100 m below m.s.l.) rock platforms, recently mapped by others,
are interpreted to be the product of early Pleistocene multiple glacio-eustatic
sea-level falls and/or rises. The presence of this subsurface platform, and
possible submarine correlative, suggests Banks Peninsula may have been
tectonically stable for much of the mid-late Quaternary.
Keywords shore platform; rock platform; sea caves;
glacio-eustacy; sea stack; plunging cliffs; coastal erosion; strato-shield
volcano; Quaternary; Banks Peninsula; Canterbury
New Zealand Journal of Geology and Geophysics, 1997, Vol. 40: 299-305
0028-8306/97/4003-0299 $7.00/0 (c) The Royal Society of New Zealand
1997
PDF file of entire paper: medium quality (2092K); (scanned from paper original: notes about this process)
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