A detailed biostratigraphic framework for 0–1.2 Ma Quaternary sediments of north-eastern Zealandia

Abstract

ABSTRACT Zealandia has very few biostratigraphic markers to help elucidate the often complex and discontinuously cored stratigraphy of Quaternary sequences on the margins and submarine plateaux of the subcontinent. In this study, a detailed biostratigraphic framework has been developed to help unravel the complex stratigraphy of tectonically deformed Quaternary sediments on the Hikurangi margin of north-eastern Zealandia. The framework is based on well documented and dated 0–1.2 Ma planktic foraminiferal records from Ocean Drilling Project (ODP) Site 181–1123 on the Chatham Rise, just north of the Subtropical Frontal Zone. The framework has 104 biostratigraphic markers and is subdivided using the Sinistral Truncorotalia truncatulinoides Zone (STZ) 0–533 ka, the Dextral Tr. truncatulinoides Zone (DTZ) 533–2440 ka, the lowest common occurrence (LCO) Tr. truncatulinoides (621 ka), the highest common occurrence (HCO) Neogloboquadrina pachyderma (624 ka), and the HCO Tr. crassacarina (1101 ka). Further subdivision is then based on the tops and bases of short-lived climatically-tempered influxes of Globigerinoides ruber, Hirsutella hirsuta, Hr. praehirsuta, Tr. truncatulinoides, Tr. crassacarina, and Nq. pachyderma. Most of these biostratigraphic markers are not unique, but sequences of markers that are unique to each marine isotope stage provide an unprecedented level of biostratigraphic detail and chronological dating when they are used within the contextual chronological framework of keystone biostratigraphic markers.