Correlation between the Warepan/Otapirian and the Norian/Rhaetian stage boundary: implications of a global negative δ <sup>13</sup> C <sub>org</sub> perturbation
Manuel Rigo, Hamish J. Campbell
Abstract
ABSTRACT The Norian/Rhaetian boundary interval (Late Triassic) is characterised by significant biotic turnover and severe climatic changes. However, this boundary still awaits formal definition. We have investigated the δ 13 C org record within a well‐preserved marine sequence exposed in the Kiritehere section, North Island, New Zealand. This section was located at higher latitudes (above 60°S) during the Triassic, and is considered the best exposed section representative of the New Zealand Warepan/Otapirian stage boundary. This is a regional boundary pertaining to the Zealandia region of Gondwana; it is described in the New Zealand Geological Timescale (NZGT) and it has been recognised as being correlative with the Norian/Rhaetian boundary. Using an integrated chemo‐ and biostratigraphic approach, we have identified a negative δ 13 C org shift close to the disappearance of the standard‐sized monotids (fossil bivalves) in the Kiritehere section. We interpret this negative shift to be the same negative δ 13 C org shift that has been proposed to define the base of the Rhaetian. However, the position of the negative δ 13 C org shift in the Kiritehere section is ca. 6.40 m below the accepted position of the Warepan/Otapirian boundary, based on biostratigraphy. This δ 13 C org isotopic shift, best thought of as a chemostratigraphic event, is regarded here as a global phenomenon.