A possible Late Oligocene–Early Miocene rocky shoreline on Otago Schist

Abstract

Duntroonian–Waitakian limestone at Kokonga in the Maniototo district, Central Otago, New Zealand is interpreted to be a rocky shoreline facies formed near the time of maximum Cenozoic marine transgression across Zealandia. The limestone, which is correlated with the Otekaike Limestone of North Otago, contains shallow and warm water indicators such as coralline algae, oysters, echinoderms, bryozoa and a foraminiferal assemblage composed almost entirely of Amphistegina. Textural zone 2B Otago Schist cobbles, pebbles and sand within the limestone, often adjacent to invertebrate fossil and coralline algal fragments, were sourced from proximal schist exposures and may be indirect evidence of the limestone having formed near to a low-lying Otago Schist coastline. However, because the precise age of limestone deposition cannot be constrained by fossil assemblages or Sr isotopes and the timing of peak marine transgression is imprecisely known, it is not possible to state whether Otekaike Limestone at Kokonga formed before, during or after the peak of maximum Cenozoic marine transgression.