The geology between Bruce Bay and Haast River, south Westland

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Wellman, H.W. 1955 The geology between Bruce Bay and Haast River, south Westland. 2nd ed. Wellington: DSIR. New Zealand Geological Survey bulletin 48 46 p.

Abstract: The geology of 250 square miles of rugged country between Haast and Mahitahi rivers is described. The rocks form three well defined groups: (c) Pleistocene and Recent moraine, gravel, sand, and swamp. (b) Upper Cretaceous, lower, and mid-Tertiary breccia, coal measures, limestone. (a) Undermass, greywacke, granite, and schist. An old but still active major tectonic feature, the Alpine fault, divides the area into two almost equal parts. South-east of this fault a regular belt of schist probably of pre-Permian age is overlain only by thin Pleistocene and Recent sediments. North-west of the fault a greywacke undermass is strongly deformed, and locally changed to hornfels by discontinuous intrusions of granite. About half is overlain by upper Cretaceous and Tertiary beds. The oldest of these beds are breccia and coal measures similar to the Hawks Crag Breccia and the Paparoa and Brunner coal measures of the Greymouth district. The coal measures are many thousand feet thick and well compacted, the coal being of medium and high volatile bituminous rank, but either too thin or too disturbed to be worth mining, except perhaps for local use. Two distinct Tertiary formations overlie the coal measures. They contain few fossils and their age is uncertain. The oldest, named the Otitia Formation, consists of limestone, tuff, agglomerate, and greywacke breccia, with a few fossils of mid-Tertiary age. The unconformably overlying beds, Tititira Formation, probably of Miocene age, are composed of sandstone, calcareous mudstone, and breccia. No upper Tertiary or lower Pleistocene beds are preserved, but the middle Pleistocene is represented by over a thousand feet of slightly consolidated moraine, fossiliferous marine silt, sand, gravel, and peat. It is named the Paringa Formation and is similar to beds 38 miles north-east at Pug Creek. The Paringa beds provide evidence for two periods of glaciation separated by an interstadial period when the climate was similar to that of the present day.