The Rai Sandstone in the Dun Mountain area, East Nelson

Abstract

In the Dun Mountain area, East Nelson, the Rai Sandstone of the Permian Lee River Group .consists of over 200 m of well- to poorly-bedded grey sandstone and dark-grey mudstone with scattered Atomodesma fragments. Locally the formation contains abundant fragments and scattered complete casts of Atomodesma sp.? aff. trechmanni (Marwick) and worm tubes, and thus may bePuruhauan. It was probably deposited in an outer-shelf, continental-slope environment. Mapping has shown that it is now bounded on its east and west sides by tectonic melanges so that previous interpretations of a westward younging sequence of Pelorus, Lee River and Maitai Groups, cannot be substantiated. Instead, the possible Puruhauan age of the Rai Sandstone and the lithologic similarities between the Pelorus Group, Maitai Group, and the Rai Sandstone suggest that the three units may be in part contemporaneous.