The dynamics of carbon cycle changes and their underlying mechanisms during the Sakmarian to Artinskian transition

Abstract

The Sakmarian to Artinskian transition was marked by significant global climate change, evolving from glacial to postglacial conditions in high southern paleolatitudes. This climate transformation was accompanied by significant paleoenvironmental changes, concomitant with a realignment in biodiversity patterns. Most previous studies attributed this climatic transition to increasing atmospheric pCO₂ concentrations, but the driving mechanisms during this period have not been clearly elucidated. To address these shortcomings, an integrated multi-proxy analysis was conducted, including measurements of mercury (Hg) and nickel (Ni) concentrations, total organic carbon (TOC), and carbon isotopic compositions of organic matter (δ¹³C_org) on a Sakmarian to Artinskian succession in North China. This investigation was carried out within the context of a new U-Pb zircon age-constrained framework, ranging from 295.6 ± 0.1 Ma to 284.2 ± 2.4 Ma, which covers the interval from the Shansi Formation to the Lower Shihhotse Formation in the Dacheng coalfield, Hebei Province. Simultaneous late Sakmarian Hg and Hg/TOC peaks, temporally coupled with negative δ¹³C_org excursions and dated tuffaceous mudstone layers, demonstrate that elevated Hg levels and carbon cycle perturbations were primarily driven by volcanic activity, with wildfires as a secondary contributor. Volcanic activity potentially associated with the Tarim II Large Igneous Province likely played a role in elevating atmospheric pCO₂ concentrations around the Sakmarian-Artinskian boundary, which may have triggered the nonglacial interval that separated the P1 and P2 glaciations. Sustained elevated atmospheric pCO₂ during the earliest Artinskian stage might be additionally attributed to the contraction of tropical coal-forming forests, an emerging trend towards more arid climates, and increased wildfires. Results offer insights into the interplay among volcanic forcing, terrestrial feedbacks, glaciations, climate dynamics, and carbon cycle disturbances during this critical phase of the late Paleozoic Ice Age.