Henderson Island : Atoll research bulletin

Abstract

Interpretation of SEASAT geoid anomaly data and improved seafloor mapping of the south-central Pacific suggest a complex tectonic history for the islands of the Pitcairn group. While Oeno atoll formed at ~ 16m.y.BP at a 'hotspot' now south of the Easter micro- plate, subsequent progressive island development at Henderson (13m.y.), Ducie (8m.y.) and Crough seamount (4m.y.) resulted from the lateral leakage of magma from the Oeno lineation along an old fracture zone, itself originating during the Tertiary reorientation of the Pacific plate. At all four islands cessation of volcanism was followed by subsidence, and the development of a carbonate cap. By comparison, Pitcairn has been the product of recent (clm.y.) volcanic activity along an independent, subparallel hotspot lineation. Nevertheless, this activity has interacted with the older island chain by transforming Henderson Island, through the process of lithospheric flexure, into an uplifted atoll with - 30m of relief.