High-latitude climatic response across the Triassic-Jurassic boundary recorded by Mg-Cu-Zn isotopes

The Triassic-Jurassic boundary is one of the most important geological boundaries in the Earth's evolutionary history. Previous paleoclimate studies focused primarily on Tethys realm at low and middle latitudes, while the northern hemisphere has yet to be studied. Here, we report Mg-Zn-Cu isotopic data for a continuous terrestrial sedimentary section in the southern margin of the Junggar Basin to constrain chemical weathering intensity and climatic change during this critical interval at high latitude. This section is enriched in heavy Mg isotopes with delta Mg-26 ranging from 0.08 parts per thousand to 0.43 parts per thousand. It displays a decreasing Zn isotopic composition with delta Zn-66 ranging from -0.05 parts per thousand to 0.24 parts per thousand, as well as limited Cu isotope fractionation (delta Cu-65 = -0.06 parts per thousand to 0.09 parts per thousand). These isotopic results, combined with major and trace elemental variations, suggest a reduced sedimentary environment and increasingly intensive chemical weathering across the boundary, responding to a warmer and more humid paleoclimate. Compared with other places located around Tethys, this regional climatic change in high latitude areas can be linked to known global climate change during this period. Our study provides new insights from high-latitude Asia to reconstruct the global pattern of climate change at the Triassic-Jurassic boundary.

Automated summary

The Triassic-Jurassic boundary is a crucial period for studying chemical weathering intensity and climatic change. In this study, Mg-Zn-Cu isotopic data from a terrestrial sedimentary section in the southern margin of the Junggar Basin in high latitude Asia are analyzed, revealing a reduced sedimentary environment and increasingly intensive chemical weathering across the boundary, responding to a warmer and more humid paleoclimate. This regional climatic change in high latitude areas can be linked to known global climate change during this period, providing new insights into the global pattern of climate change at the Triassic-Jurassic boundary.