New Zealand Journal of Geology and Geophysics abstracts
A Holocene progradation record from Okains Bay, Banks Peninsula, Canterbury,
New Zealand
WAYNE STEPHENSON
Department of Geography
University of Canterbury
Private Bag 4800
Christchurch, New Zealand
JAMES SHULMEISTER
Research School of Earth Sciences
Victoria University of Wellington
P.O. Box 600
Wellington, New Zealand
Abstract Fifty-eight distinct ridges are preserved on the
Holocene progradation plain in Okains Bay, Banks Peninsula, Canterbury. Of
these, 48 represent beach berm and foredune complexes and the remaining 10 are
transverse dune ridges. Periods of rapid coastal progradation are marked by
multiple beach berm preservation, whereas intervening periods of lower sediment
accumulation result in a stable coastline and transverse dune formation.
Infilling of the bay began following sea-level stabilisation in the mid
Holocene. The fill is dominantly fine sand, which is derived from sediment
carried around Banks Peninsula in the Southland Current and washed into Okains
Bay by wave action. Variations in the progradation rate are therefore proxy
indicators of coastal erosion in the Canterbury Bight. We demonstrate that
there is little progradational fill preserved between c. 6500 and 2000 yr
BP. This implies significant changes in sediment delivery to the Southland
Current within the last 2000 yr, which we attribute to increased coastal
erosion in South Canterbury. We speculate that this increasing erosion resulted
from increased wave energy regimes, which in turn may relate to increasing
Southern Hemisphere seasonality following the precessional cycle.
Keywords Okains Bay; banner bank; Canterbury; continental
shelf; coastal erosion; precessional cycle; Holocene; climate change
New Zealand Journal of Geology & Geophysics, 1999, Vol. 42: 11-19
0028-8306/4201-0011 $7.00/0 (c) The Royal Society of New Zealand 1999
PDF file of entire paper: medium quality (974K); (scanned from paper original: notes about this process)
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