The Warepan Stage of the Upper Triassic: Redefinition and subdivision

Abstract

Recently published studies show that the current definition of the Warepan Stage of the New Zealand-New Caledonian Upper Triassic, based upon the incoming of Monotis (Entomonotis) richmondiana Zittel, is inadequate. Past practice has relied upon the first appearance of the genus Monotis, and earliest species are not M. richmondiana but members of the subgenus Eomonotis. To avoid the stage boundary being placed within, instead of at the base of, a sequence of short-lived rapidly evolving species of the one genus, it is recommended that M. richmondiana be replaced as the Warepan index fossil by the earliest species in the region, namely, Manolis (Eomonotis) kiritehereensis G-M., M. (E.) rauparaha mokaui G-M., and M. (E.) murihikuensis taringatura G-M. Stratigraphic analysis of New Zealand sequences containing these three taxa indicates that they are likely to have been contemporaries. This redefinition calls into doubt the suitability of the Rocky Dome (South Otago) area as a stratotype, for Eomonotis has not been recorded here. Rather than take the more drastic step of selecting a new stratotype and designating a new name for the stage, the familiar name is retained and the Kiritehere coastal section, southwest Auckland, is named as a reference section to demonstrate more fully the faunal succession.Taxonomic re-evaluation of New Zealand Manotis provides the opportunity for further formal subdivision. Two substages are proposed, the Lower Warepan Kiriteherean Substage based on the rangezone of Eomonotis in New Zealand, and the Middle Warepan Marokopan Substage based on the rangezone of Entomonotis. A potential Upper Warepan substage is left undefined pending fuller description of the Warepan fauna.

Mesozoic stratigraphy of the Marokopa area, southwest Auckland, New Zealand

“…The formation is wholly Warepan in age, and this fauna is a small part of the extensive Warepan fauna recorded by Grant-Mackie (1981 from the Kiritehere coast section and elsewhere. It indicates the Richmondiana Chronozone of the Marokopan Substage (Grant-Mackie 1985). The overlying Calvata Chronozone, which is present in the Kiritehere coast section and in a track off Mangatoa Road to the south (Grant-Mackie 1981), was not found, probably because of lack of exposure.…”

The Triassic Marine Biota of Eastern Indonesia and its Interregional and Global Correlation: A Review

“…The presence of Monotis in Seram, Buton, and Rote Islands and other parts of Indonesia is not known in Misool (Hasibuan, 2007a). Monotis is widely distributed in the world such as in New Zealand, New Caledonia, Japan, British Columbia, Soviet Far East, and Western Canada of Norian age (Grant-Mackie, 1978, 1985. Monotis is an indicator for Norian Stage, because no Monotis were found other than this age (Grant-Mackie, 1978).…”

New Caledonian Triassic Bryozoa

“…reticulata Wilckens within the formation, coupled with stratigraphic location below the bivalve Manticula Grant-Mackie (1985) for New Zealand Warepan strata, with the New Caledonian zonal scheme of Campbell and Grant-Mackie (1984), showing the zones to which bryozoanbearing localities are allocated. Note that f77 could belong in either the Gigantea or Discordans zone.…”