Timing and potential causes for paleo-environmental change during the Late Paleozoic Ice Age (Carboniferous-Permian transition)

Recent findings using U-Pb zircon geochronology combined with paleoenvironmental proxies and sedimentological observations have constrained the timing and extent of glacial advances and retreats across southwestern and south-central Gondwana during the Late Paleozoic Ice Age (LPIA). Sedimentary archives deposited during the transition from the latest Carboniferous to the earliest Permian reveal widespread short-term warming as reflected in the loss of subglacial deposits across Gondwana basins, some of which were fully deglaciated by the end of the Carboniferous at 299 Ma. These observations are accompanied by fluctuations in proxies for pCO₂ and δ¹³C across the Carboniferous-Permian transition. These climate oscillations require large scale, short-lived climate forcing mechanisms. One such potential cause may be greenhouse gas emissions related to widespread magmatism across central and northwestern Europe, which has been linked to a deep-seated mantle plume. The effects of igneous activity may be further amplified by the interaction of magma with widely occurring organic-rich sedimentary rocks across this region. The products of this magmatic province predominantly show silicic compositions, but intermediate and basaltic melts also occur in outcrops and cores from the British Isles and southern Sweden (predominantly in the form of dykes and sills), the Oslo and Skagerrak Graben as well as the Northern and Southern Permian Basin, which extends from the North Sea across northern Germany to Poland (predominantly filled with rhyolitic and rhyodacitic volcanics).

Available radioisotopic age constraints for these magmatic products are from different isotopic systems whose comparison requires consideration of systematic errors, and often have large uncertainties (at the several million-year level) rendering them unsuitable for studying potential causal relations to contemporaneous climate fluctuations that operate at much shorter timescales. We review these results and present new high-resolution U-Pb zircon CA-TIMS (Chemical Abrasion-Thermal Ionization Mass Spectrometry) ages from volcanic and intrusive products from the Southern Permian Basin and adjacent areas which show that the duration of magmatic activity was much shorter than previously thought. We suggest that greenhouse gas emissions from the magma, and its interaction with biogenic sedimentary rocks, may have been the cause for the observed short-term climate oscillations across the Carboniferous-Permian transition. These short-term events, and their effects, appear to be superimposed on long-term climate drivers such as continental arc volcanism, tropical silicate weathering, as well as changes in the distribution of continents in high latitudes, the opening and closing of oceanic gateways and tectonically induced variation in the equilibrium-line altitude for ice.

The research presented here is supported by NSF grant 1728705