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Zeederbergs Formation
Grid Ref (WGS84 Lat/Long in decimal degrees)
The outcrop shows a pavement of pillow lavas with spherulites, some patches of pillow breccia and a tuff band. The pillows are generally about 1-2m in cross-section and some 3-D exposures suggest lengths of 3-4m. The spherulites tend to be concentrically arranged, with some flow units consisting almost wholly of coalesced spherulites. In some pillows the spherulites appear to be located around cooling cracks.
The feldspars in these rocks are commonly saussuritised but clinopyroxene generally survives. The spherulites consist of radiating aggregates of albite in a dominantly tremolitic matrix.
The geochemistry of these rocks is discussed by Nisbet et al. (1977). They contain about 53.5% SiO2 and 8% MgO. The tuff at this locality penetrates between some of the immediately overlying pillows, but the layer is strongly sheared, a feature of most of the exposed tuffs throughout the belt.