Integrated biostratigraphy of the Raukumara Series (Cenomanian‐Coniacian) at Mangaotane Stream, Raukumara Peninsula, New Zealand

Abstract

The New Zealand Upper Cretaceous Raukumara Series is divided into three stages: in ascending order, the Arowhanan, Mangaotanean, and Teratan. The lower boundary stratotypes for all three stages are in Mangaotane and “Te Rata” streams, in the Raukumara Range, Raukumara Peninsula (the “Mangaotane section"). Although affected by a number of minor faults, the section is relatively complete, spans the entire series, and is well exposed. The lower boundary stratotype of the Arowhanan Stage is within Waitahaia Formation; the boundary stratotypes of the other two stages are in Karekare Formation. The section contains abundant inoceramid bivalves and has yielded poorly to moderately preserved, moderately diverse foraminiferal and dinoflagellate assemblages. The Mangaotane section is divided into six inoceramid zones, five dinoflagellate zones, and four informal foraminiferal assemblage zones. Lower boundaries of the Arowhanan, Mangaotanean, and Teratan Stages are tied to the lowest occurrences of inoceramid taxa, biostratigraphic events that can be easily recognised and widely correlated within New Zealand. Correlations to the international time‐scale are more problematic and are hampered by the lack of reliable or unambiguous biostratigraphic datums and the lack of absolute ages or other non‐biostratigraphic controls in the New Zealand succession. Based only on biostratigraphic data, the following correlations are proposed: Arowhanan Stage = upper Cenomanian to lower Turonian; Mangaotanean Stage = lower‐upper Turonian; Teratan Stage = upper Turonian to upper Coniacian.