POTENTIAL ENVIRONMENTAL CONSEQUENCES OF PANTHALASSAN MARGIN VOLCANISM IN THE LATE PALEOZOIC

The late Paleozoic was a time of environmental upheaval: an ice age spanning over 50 million years was terminated, and two mass extinctions ensued. These events have been correlated to increased pCO₂: the collapse of the late Paleozoic ice age (LPIA) in the Early Permian corresponds to pCO₂ levels of ~3500 ppmv, the end-Guadalupian extinction occurred in tandem with the eruption of the Emeishan Traps, and the end-Permian mass extinction has been attributed to the volcanism of the Siberian Traps. However, a source for increased pCO₂ during the Early Permian has not been identified. It is proposed that volcanism along the >12,000 km long Panthalassan convergent margin of Gondwana amplified pCO₂ levels in the Early Permian, contributing to the transition from icehouse to greenhouse conditions. Further, Panthalassan margin volcanism was continuous throughout the Permian, and this sustained input of CO₂ may be the cause of decreased alpha diversity during this period. Continuous volcanism would have preemptively stressed biota so that they were less resilient during the eruptions of the Emeishan and Siberian Traps. Thus volcanism along the Panthalassan margin may have been a contributing driver to the end of the LPIA and the Middle and Late Permian mass extinctions.

Volcanism and other magmatic activity along the Panthalassan margin are recorded in volcanic and plutonic rocks in western South America, southern Africa, Antarctica, and eastern Australia. The Choiyoi Group of Argentina is the largest known upper Paleozoic igneous province of the Panthalassan margin, with an estimated volume of 1.5 million km^3 of volcanic rocks. CO₂ output from the Choiyoi Group alone is estimated on the order of 10^22 g. Therefore, it is proposed that the total CO₂ emissions from Panthalassan margin volcanism were ample enough to contribute to the Early Permian icehouse-greenhouse transition and to prime biotic systems for the Middle and Late Permian extinctions.