Revision of the Piripauan and Haumurian local stages and correlation of the Santonian‐Maastrichtian (Late Cretaceous) in New Zealand

Abstract

The uppermost Cretaceous in New Zealand is represented by the local Mata Series, composed of the Piripauan and overlying Haumurian Stages. The existing definitions and subdivision of these stages, and the type section at Haumuri Bluff, southeastern Marlborough, are wholly inadequate. To address these problems, three key sections in southeastern Marlborough have been studied in detail: a tributary of Ben More Stream, the headwaters of Kekerengu River, and a railway cutting at the mouth of Conway River. All three sections have yielded rich palynomorph assemblages and the first two contain inoceramid bivalves and foraminiferal faunas. In addition, magnetostratigraphic data have been obtained from the Ben More Stream section. We propose to revise the Piripauan and Haumurian Stages from new boundary stratotypes in the Ben More Stream section. The Piripauan is defined at the lowest occurrence of the inoceramid /. pacificus. The base of the Haumurian Stage is defined at the lowest occurrence of the dinoflagellate Nelsoniella aceras. In addition, we propose to subdivide the Haumurian into formal Lower and Upper substages; the base of the Upper Haumurian is defined at the lowest occurrence of the dinoflagellate Isabelidinium pellucidum in a boundary stratotype in the Conway River railway cutting. These boundary criteria can be correlated widely within New Zealand across a broad range of marine facies. The Piripauan contains two inoceramid and three dinoflagellate zones. The Haumurian contains six dinoflagellate zones and five subzones. Based on biostratigraphic and magnetostratigraphic data, the Piripauan/Haumurian boundary is correlated with the C34‐C33 magnetochron boundary and with the middle‐upper Santonian boundary. The Piripauan and Haumurian Stages thus have durations of c. 1.7 and 19.5 m.y., respectively. In terms of content, these revisions largely preserve the stages as used previously in New Zealand and require no significant changes to existing geological maps.