High latitude terrestrial carbon isotope and mercury perturbations across the Late Triassic Carnian Pluvial Episode in Northwestern China

The Carnian Pluvial Episode (CPE) was a Late Triassic interval of global environmental changes and biological turnovers linked to C-cycle perturbation and global warming. Records of the CPE come mainly from low latitudes, and its impact at higher latitudes is poorly known. Here, we present organic matter (OM) C-isotope and Hg concentration data of bulk samples from the Junggar Basin (Xinjiang, Northwestern China), which in the Late Triassic was located at ca. 60° N. In this fluvial-lacustrine succession, a positive C-isotope trend is interrupted by four negative C-isotope excursions (NCIEs) that can be correlated to the global Carnian C-isotope record. Two phases of enhanced Hg deposition during the CPE are found. During the first two NCIEs (Phase I), increases in Hg were likely linked to either volcanism and/or the oxidation of OM. Later Hg enrichments during the last two NCIEs (Phase II) were controlled by increased input of OM from higher plants to the lacustrine environment. The first NCIE coincides with marked changes in lithology and macroflora, indicative of a shift to a more humid climate. Our records show how the C-cycle perturbations that punctuated the CPE drove perturbations to regional hydrology and flora at northern high latitudes.