Abstract
The Late Triassic Carnian Pluvial Episode (CPE) saw a dramatic increase in global humidity and temperature that has been linked to the large-scale volcanism of the Wrangellia large igneous province. The climatic changes coincide with a major biological turnover on land that included the ascent of the dinosaurs and the origin of modern conifers. However, linking the disparate cause and effects of the CPE has yet to be achieved because of the lack of a detailed terrestrial record of these events. Here, we present a multidisciplinary record of volcanism and environmental change from an expanded Carnian lake succession of the Jiyuan Basin, North China. New U-Pb zircon dating, high-resolution chemostratigraphy, and palynological and sedimentological data reveal that terrestrial conditions in the region were in remarkable lockstep with the large-scale volcanism. Using the sedimentary mercury record as a proxy for eruptions reveals four discrete episodes during the CPE interval (ca. 234.0 to 232.4 Ma). Each eruptive phase correlated with large, negative C isotope excursions and major climatic changes to more humid conditions (marked by increased importance of hygrophytic plants), lake expansion, and eutrophication. Our results show that large igneous province eruptions can occur in multiple, discrete pulses, rather than showing a simple acme-and-decline history, and demonstrate their powerful ability to alter the global C cycle, cause climate change, and drive macroevolution, at least in the Triassic.
Highlights
The Late Triassic Carnian Pluvial Episode (CPE) saw a dramatic increase in global humidity and temperature that has been linked to the large-scale volcanism of the Wrangellia large igneous province
Two tuffaceous claystones were sampled from the uppermost part of the Tanzhuang Formation; they are similar to other Late Triassic tuffs from the Ordos Basin [28]
The single-point analysis error of standard zircons Plešovice and 91500 is less than 2.2% (SI Appendix, Table S1). These ages indicate that the topmost Tanzhuang Formation belongs to the middle of the Carnian Stage (Fig. 2 and SI Appendix, Fig. S2) and are consistent with the Late Triassic age indicated by the spore–pollen assemblage
Summary
The Late Triassic Carnian Pluvial Episode (CPE) saw a dramatic increase in global humidity and temperature that has been linked to the large-scale volcanism of the Wrangellia large igneous province. We have investigated terrestrial sediments from the Zuanjing-1 (ZJ-1) borehole in the Jiyuan Basin of the southern North China Plate (NCP) and use zircon U–Pb ages from two tuffaceous claystone horizons, fossil plant biostratigraphy, and organic C isotope (δ13Corg) and Hg chemostratigraphy to identify the CPE and volcanic activity. 234 to ∼232 Ma; Late Triassic) was an interval of significant changes in global climate and biotas [1, 2] It was characterized by warming [3, 4] and enhancement of the hydrological cycle [5,6,7], linked to repeated C isotope fluctuations [8,9,10,11] and accompanied by increased rainfall [1], intensified continental weathering [9, 12], shutdown of carbonate platforms [13], widespread marine anoxia [4], and substantial biological turnover [1, 2, 10]. Some of the new organisms may have flourished because of the spread of humid environments, such as the turtles and metoposaurids [18, 19]
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