Heavy minerals in Cretaceous sandstones in Marlborough

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Smale, D. 1985 Heavy minerals in Cretaceous sandstones in Marlborough. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report SL 14 29 p.

Abstract: Heavy minerals were examined from Cretaceous sandstones from a broad area of central Marlborough, and a more localized area in the Clarence valley. Throughout there were two main populations, both similar to Torlesse populations, on richer in semi-opaque debris (sodeb) and epidote, and the other richer in zircon. The former had greater influence in the Coverham and Wharekiri areas and in the older rocks of the Clarence valley; the zircon rich population had greater influence in the younger rocks of the Awatere and Clarence valleys. The change is everywhere most pronounced in the Motuan. In the Awatere valley it occurs between an olistostromal unit and the overlying alternation sandstone and mudstone, and is marked also by an increase in garnet; in the Clarence valley the change is most pronounced near the top of Split Rock Formation. It is not possible to determine if this change is due to provenance variation or to intrastratal solution; either is possible. (auth)