Stratigraphy and Paleoecology of the Productus Creek Group, South Island, New Zealand

Abstract

Abstract In middle and late Permian time, the Productus Creek area of South land, New Zealand, was the site of simultaneous accumulation of shallow marine, biogenic carbonate and immature volcanogenic sediments. The prismatic shell fragments of the bivalve Atomodesma formed the major limestones; this suggests a well-established bank environment. Less extensive calcareous Bryozoa banks succeeded the Atomodesma banks, and were covered in turn by a prograding conglomerate in late Permian time. Trends in fossil assemblages, clay mineralogy, sediment sizes, and sediment thicknesses suggest a nearby Permian shore line north-west of Productus Creek. Two hypothetical transgression-regression models of the Productus Creek Group are discussed: (a) a migrating delta and (b) eustatic sea-level variation which takes into account contemporaneous glacial events in Australia and elsewhere. One new informal formation, the Weetwood Formation, is named, and the Mangarewa, Elsdun, and Hawtel Formations are redefined.