Ngā Tohuwhenua Mai Te Rangi: A New Zealand Archeology in Aerial Photographs
The manufacture of stone tools in Polynesia ranged from sustained periods of wide-ranging trade and great sophistication in exploitation and manufacture, to apparently crude usage of poor quality, local materials. 8 The favoured stone in Eastern Polynesia was basalt, the basic geological component of all the high islands. Finegrained, easily flaked but tough stone was especially sought after, with well-known sources in Samoa, on Pitcairn Island and on the Mauna Kea volcanic plateau, Hawaii. There it was exposed in weathered forms, in most places in spectacularly steep or otherwise difficult volcanic landforms. On Mauna Kea, it is exposed above the vegetation line at 3,500 m altitude. 9 Exploring for these sources of stone probably involved a model of a volcanic landscape with readily identified sources of stone. Polynesians appear to have applied the same insights to New Zealand, where there was a wide range of potential stone usage, with much of it actually exploited.
Two main landforms were readily identified using this model of a good stone-source landscape: the basaltic lava domes that occur from the Bay of Plenty to Northland, and the very much older geological land forms containing the serpentine 'mineral belts' of Nelson and Southland. The volcanic stone, basalt, lent itself to sophisticated stone adze production. More importantly, its presence could be readily identified from the characteristics of a volcanic landscape. The hills were high and steep-sided; and they are often associated with a basalt dome emerging from a more eroded volcanic area. 10
In the Nelson region, the distinctive vegetation cover of the mineral belts would quickly be recognised. The mineral belts are zones on the earth's continental plate where the old surface rocks, volcanic or sedimentary in origin, have been pressed into the molten part of the crust. From time to time the ancient rocks have 'oozed' back up to the surface. 11 The exterior of these blocks had been 'baked' at high temperature and pressure in the earth's deep mantle, transforming the rock so that it retained its original toughness but could be worked by chipping in the same way as the basalt. As the soil and softer rock around these hard blocks erodes, the blocks themselves are left free-standing in distinctive forms.
Two views of the same complex of argillite adze quarries at Samson Bay, Croisilles Harbour, in the Nelson mineral belt
The argillite occurred in layers on the surface of some of the rock outcrops. Both the outcrops and stone scattered on the surrounding soil were chipped into adze 'blanks' and carried out of the location. The spur is vegetated with stunted growth compared with the surrounding country, caused by the toxicity of the chemicals in the soils at this location. The vegetation has also been burnt repeatedly to gain access to the stone and, in recent times, for grazing. [Above] is a distant view to the south-east.