Foraminiferal paleoecology and initial subsidence of the early Miocene Waitemata Basin, Waiheke Island, Auckland

Abstract

Abstract Data from 29 fossil foraminiferal faunas from early Miocene strata (Waitemata Group; Kawau Subgroup) on Waiheke Island are analysed by cluster analysis. The dominant species are grouped into six species associations that occur in different inferred environments: Elphidium— beach or shallow subtidal sand; Buliminella—high energy, inner shelf; Cribrorotalia—moderately exposed, inner to mid shelf; Quinqueloculina—inner and shallow mid shelf; Nonionella—deep inner to mid‐shelf muddy sand; and Cassidulina—outer shelf. The samples are grouped in terms of relative species abundances into seven sample associations, and their paleoenvironments have been determined using the inferred environments of their constituent species associations. These assessed paleoenvironments of the seven sample associations are used to reconstruct the changing paleogeography of the Waiheke area during the early Miocene. The Waiheke strata accumulated during a period of subsidence of about 200 m early in the formation of the Wa...