A possible Norian–Rhaetian boundary in the high-latitude continental Junggar Basin indicated by the δ 13 C org record

Abstract

Abstract In contrast to the Triassic–Jurassic boundary, there is no consensus on the definition and age of the Norian–Rhaetian boundary (NRB), which hampers the global correlation of Rhaetian strata and thus interpretation of the patterns and driving mechanism of the end-Triassic mass extinction. Recent works show that a significant negative carbon isotope excursion (N-CIE) occurs in the NRB interval ( c. 205.7 Ma), which probably provides a physical marker for the NRB. However, no such records have so far been reported from high-latitude continental deposits. Here we present high-resolution bulk organic carbon isotope data from the Upper Triassic continuous lacustrine-to-fluvial deposits in the Haojiagou section of the high-latitude continental Junggar Basin in northwestern China. A significant N-CIE is shown at an age of c. 205 Ma, which is most probably the expression of the NRB N-CIE in the Junggar Basin owing to their very close occurrence times. The NRB is thus probably along the N-CIE in the Haojiagou section, and a short Rhaetian stage is then supported. The Late Triassic climate in the high-latitude Junggar Basin was consistent with the global changes in climate, characterized by a long-sustained cooler and humid climate interrupted by the late Norian and latest Rhaetian warm events.