|Distribution and origin of clay minerals in surficial shelf sediments, western North Island, New Zealand|
Hume, T.A., Terry; Nelson, C.S., Campbell (1986). Distribution and origin of clay minerals in surficial shelf sediments, western North Island, New Zealand. Mar. Geol. 69(3/4): 289-308
In: Marine Geology. Elsevier: Amsterdam. ISSN 0025-3227, more
Clay minerals; Continental shelves; Distribution; Marine geology; Mineralogy; Origin; Sediments; Surface layers; PSE, New Zealand, North I., Goat I. [Marine Regions]; Marine
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Western shelf surficial sediments are mainly terrigenous muds and variably muddy fine and very fine sands of mixed modern/relict heritage. Overall their clay fraction is dominated by illite and smectite, lesser amounts of chlorite and mixed-layer clays, and some kaolinite. The close similarity of shelf clay-mineral assemblages with those in adjacent river and harbour sediments demonstrates that offshore north-south regional trends in clay mineralogy parallel regional changes in onshore geology, involving both western North Island and more distant northwestern South Island sources. The same detrital clay-mineral patterns on the shelf have persisted during the sea-level rise following the Last Glaciation and are complicated only by local concentrations of authigenic smectite from volcanogenic material. On the basis of the distribution and origin of the major clay minerals, five north-south clay petrologic zones were found to occur on the shelf.