Arc volcanism, carbonate platform evolution and palaeo-atmospheric CO<sub>2</sub>: Components and interactions in the deep carbon cycle

Abstract

Carbon dioxide (CO2) liberated at arc volcanoes that intersect buried carbonate platforms plays a larger role in influencing atmospheric CO2 than those active margins lacking buried carbonate platforms. This study investigates the contribution of carbonate-intersecting arc activity on palaeo-atmospheric CO2 15 levels over the past 410 million years by integrating a plate motion model with an evolving carbonate platform development model. Our modelled subduction zone lengths and carbonate-intersecting arc lengths approximate arc activity with time, and can be used as input into fully-coupled models of CO2 flux between deep and shallow reservoirs.Continuous and cross-wavelet as well as wavelet coherence analyses were used to evaluate trends between 20 carbonate-intersecting arc activity, non-carbonate-intersecting arc activity and total global subduction zone lengths and the proxy-CO2 record between 410 Ma and the present. Wavelet analysis revealed significant linked periodic behaviour between 75-50 Ma, where global carbonate-intersecting arc activity is relatively high and where peaks in palaeo-atmospheric CO2 is correlated with peaks in global carbonateintersecting arc activity, characterised by a ~32 Myr periodicity and a 10 Myr lag of CO2 peaks after 25 carbonate-intersecting arc length peaks. The linked behaviour may suggest that the relative abundance of carbonate-intersecting arcs played a role in affecting global climate during the Late Cretaceous to Early 2Paleogene greenhouse. At all other times, atmospheric CO2 emissions from carbonate-intersecting arcs were not correlated with the proxy-CO2 record. Our analysis did not support the idea that carbonateintersecting arc activity is more important than non-carbonate intersecting arc activity in driving changes in palaeo-atmospheric CO2 levels. This suggests that tectonic controls are more elaborate than the subduction-related volcanic emissions component or that other feedback mechanisms between the 5 geosphere, atmosphere and biosphere played larger roles in modulating climate in the Phanerozoic.

Evolution of Eye Reduction and Loss in Trilobites and Some Related Fossil Arthropods

“…Ironically, when the volcanic activity finally had calmed down, the excessive plant growth reduced the atmospheric CO2 levels. It is assumed that the loss of this CO2 contributed to a global cooling and finally a relatively short but intense period of glaciation in the landmasses of Gondwana, now shifted far to the south, took place at the very end of the Devonian (Hangenberg Event, [35,42,43]. While the Kellwasser Events had the severest effects on marine organisms such as trilobites e.g.…”