Facies analysis and sequence stratigraphy of Early Oligocene Glen Massey Formation (Te Kuiti Group), Waikato - King Country Basin, New Zealand

Abstract

This report presents a comprehensive facies and sequence stratigraphic analysis of the Early Oligocene Glen Massey Formation, one of eight formations within the Late Eocene to earliest Miocene Te Kuiti Group in the Waikato-King Country Basin in central-western North Island, New Zealand. The Glen Massey Formation is a mixed carbonate-siliciclastic succession with three main facies associations: limestone (Elgood Limestone Member), calcareous siltstone (Dunphail Siltstone Member) and calcareous sandstone (Ahirau Sandstone Member). These facies, established from field descriptions supplemented by laboratory textural and petrographic data, accumulated in a continental shelf setting above coal measure and marginal marine units in basal Te Kuiti Group or above the Mesozoic basement rocks along the eastern margin of Taranaki Basin. The formation comprises one sequence for which key surfaces are identified and described and used to establish the extent of systems tracts, representing different parts of a relative sea-level cycle. A model sequence shows the distribution of facies within systems tracts in a cross-shelf profile.