New Zealand Journal of Geology and Geophysics abstracts

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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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