U-Pb detrital zircon age patterns in sandstones from the Wellington and eastern Cook Strait area have broad Permian-Triassic and Precambrian-early Paleozoic age groups that confirm a previously established Triassic Rakaia Terrane correlation. Along the western Cook Strait coast, meta-psammitic Marlborough Schist samples have zircon patterns with a single age group, either Late Triassic or Jurassic, indicating a Waipapa Terrane ancestry. Similar data from the central Cook Strait region suggest that Waipapa Terrane basement continues northeastwards from Marlborough through Fishermans Rock to Kapiti Island. The Rakaia-Waipapa terrane boundary thus lies east of Kapiti Island and Fishermans Rock. The position of a Caples-Waipapa terrane boundary within the Marlborough Schist is less certain but most of the eastern Marlborough Schist is Waipapa Terrane.