Lithofacies, paleoenvironments and elements of sequence architecture, Late Oligocene - earliest Miocene Castle Craig Subgroup (Te Kuiti Group), Waikato-King Country Basin, New Zealand

Abstract

This report presents a comprehensive facies and sequence stratigraphic analysis of the Late Oligocene Castle Craig Subgroup (Orahiri Formation and Otorohanga Limestone) within the Late Eocene – Earliest Miocene Te Kuiti Group in the Waikato-King Country Basin in central-western North Island, New Zealand. Detailed field investigations have identified 12 lithofacies within the Castle Craig Subgroup, which have been grouped into three lithofacies associations named limestone, mixed carbonate-siliciclastic sandstone, and siliciclastic sandstone after the dominant lithologies. In areas south of Aotea Harbour the subgroup comprises a wide variety of limestone types with variable siliciclastic content, dominated by coarse skeletal rudstone/grainstone, with aggregate stratigraphic thicknesses of up to 100 m. These sediments accumulated at shelf depths in a moderate to highenergy tidal seaway. Around Raglan Harbour and in areas to the north, the subgroup comprises predominantly planktic foraminiferal-rich packstone to wackestone and calcareous siltstone/marl that accumulated mainly in slope/upper bathyal settings.