Sedimentology and stratigraphy of Prospect Formation, Te Anau Basin, western Southland, New Zealand

Abstract

The syntectonic late Miocene—Pliocene Prospect Formation, comprising over 3000 m of gravels and sands, forms the uppermost preglacial unit in the central Te Anau Basin, western Southland, New Zealand. Its inferred distal correlatives, the marine Rowallan Sandstone and Te Waewae Formation, lie to the south in the Waiau Basin. These two units are removed from the Waiau Group and, together with the previously ungrouped Prospect Formation, are placed in a newly proposed lithostratigraphic unit, the Wilderness Group. The largely nonmarine Prospect Formation is wholly subdivided into five members on the basis of lithofacies associations and petrofacies. The basal Forest Burn and Umbrella Flat Members (new) were deposited by coarsegrained deltaic systems which prograded across the marine Te Anau Basin from petrologically distinct uplifted basement terranes to either side. The upper part of the formation is dominated by gravelly braided stream deposits, subdivided into the Mt York, Little Creek, and Key Members on the basis of petrofacies and lithofacies assemblages. © 1996 Taylor & Francis Group, LLC.