Petrology of Mesozoic sediments from sheet N29 - Leatham

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Smale, D. 1985 Petrology of Mesozoic sediments from sheet N29 - Leatham. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report SL 15 16 p.

Abstract: Most of the Torlesse rocks in the Leatham sheet are feldspathic litharenites, but they vary from lithic feldsarenites to litharenites. Rock fragments are volcanic (mostly acid or intermediate) and sedimentary (mudstone and fine sandstone). Rocks in the tectonized zones, particularly along the Silverstream Fault Zone, are characterised by a higher proportion of ''firty'' matrix, prehnite in veins (some with pumpellyite), and on average a slightly lower clastic quartz component than between the tectonized sonzes. Tuffaceous sandstones and tuffs are restricted to the tectonized zones. Where rock fragments are more abundant in a zone several km wide south of the Alpine Fault, more may be sedimentary. However, in general it is difficult to see any systematic detrital compositional variation. The sediments appear to have been well mixed, and from a provenance consisting dominantly of sedimentary rocks, with prominent acid to intermediate volcanics and sparse granite