The Geology and paleoecology of Nukumaruan strata near the junction of Ruakokopatuna and Makara rivers

Abstract

The area covers four square miles, four miles South of Martinborough in Southern Wairarapa, see fig. 1. Within the area Pliocene and Pleistocene rocks folded in a general North-Easterly direction are overlain unconformably by later Pleistocene and recent unfossiliferous greywacke gravels. Pliocene massive, sparsely fossiliferous siltstones outcropping in the South and South-East portion were not examined in detail. The overlying Upper Waitotoran and Nukumaruan strata consisting of interbedded siltstones, sandstones, limestones, conglomerates, and gravels were mapped in detail, and intensive fossil collections were made with the aim of reconstructing the environment and climate during the period of their deposition. For this purpose both lithologic and biologic criteria were used. Such a study is possible in this area as it contains a continuous sequence of abundantly fossiliferous strata, which, with minor fluctuations, has an overall tendency to range from beds deposited at greater depths at the base of the sequence to shallower at the top. Thus the fossil populations occuring at different levels in the sequence would be expected to show a variation controlled mainly by the depth of deposition and edaphic conditions.