Constraining the Triassic–Jurassic boundary carbon cycle perturbations using high-resolution δ 13 C org records from the Haojiagou section in northwestern China

Abstract

Abstract Large magnitude and rapid negative carbon isotope (δ 13 C) excursions in the Triassic–Jurassic boundary (TJB) interval have been proposed as critical evidence for the hypothesis that the emplacement of the Central Atlantic Magmatic Province (CAMP) triggered global carbon cycle perturbations and the end-Triassic mass extinction (ETE). However, the pattern and timing of δ 13 C variations during the ETE remain poorly constrained. Here I present high-resolution organic carbon isotope (δ 13 C org ) records from a terrestrial TJB succession continuously exposed along the Haojiagou valley on the southern margin of the Junggar Basin, northwestern China. The δ 13 C chemostratigraphic correlations, combined with the palynological data, indicate that the position of the TJB should be placed at the base of bed 53. Importantly, the results show that two rapid negative carbon isotope excursions at the end Triassic roughly coincide with two episodes of variations in the palynological records. This observation supports the hypothesis that two pulses of biotic crisis during the ETE may have been triggered by two major episodes of CAMP magmatic activity. In addition, the data in this study support an early start for CAMP magmatic activity in the early Rhaetian, which may have led to a global carbon cycle perturbation and the related biotic crisis or turnover.