New Zealand Journal of Geology and Geophysics abstracts

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Clast size characteristics of gravel within rivers of the Waimea Plains, Nelson

GREG H. BROWNE

Institute of Geological & Nuclear Sciences
P.O. Box 30 368
Lower Hutt, New Zealand

JOSEPH T. THOMAS

Tasman District Council
Private Bag 4, Richmond
Nelson, New Zealand

Abstract  Gravel within rivers of the Waimea Plains near Nelson, New Zealand, was derived through the Wairoa Gorge from Paleozoic-Mesozoic basement rocks to the southeast, and to a lesser extent from Pleistocene gravels to the west. A downstream reduction of mean clast size and an increase in sorting occurs in three rivers of the Waimea Plains. Clast form is dominated by bladed clasts, with a slight tendency with transport distance to more elongate forms. Clast sizes are apparently larger in the modern rivers than in fluvial gravels of the Last Glacial period. The smaller clast size in the Last Glacial deposits may indicate more efficient clast-size reduction in glacial as opposed to modern-day rivers.

Keywords  Waimea Plains; Nelson; clast-size changes; fluvial deposition

New Zealand Journal of Geology & Geophysics, 2001, Vol. 44: 89-96

0028-8306/01/4401-0089 $7.00/0 (c) The Royal Society of New Zealand 2001

PDF file of entire paper: medium quality (792K); (scanned from paper original: notes about this process)

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