Recurrence rates of explosive volcanism in paleo-equatorial Pangaea, and implications for climate near the peak late Paleozoic ice age

Abstract

The continental Brousse-Broquiès basin (Massif Central, France) preserves a well-exposed section of upper Carboniferous pyroclastic-volcaniclastic lacustrine strata. We present high-precision geochronology and detailed sedimentology that together define a Kasimovian (305.77–306.10 Ma) volcanic recurrence interval of < 10 ky. This is the first quantification of volcanic recurrence from deep (pre-Mesozoic) time, and importantly, represents an unique opportunity to gain insight into the nature of frequent and highly explosive silicic volcanism occurring across eastern equatorial Pangaea during the peak of the late Paleozoic ice age (LPIA). These data emanate from a single, unusually well-exposed and well-constrained site. However, this site is representative of many documented but poorly preserved volcanic centers of coeval or similar ages across west-central Europe. The concentration in both time and space of such highly explosive volcanism in paleoequatorial Pangaea has large implications for the climate system during Earth’s penultimate icehouse. The recurrence rates established here support ongoing climate modeling efforts to test the hypothesis that this volcanism imposed a significant cooling effect near and during peak LPIA conditions prior to Permian icehouse collapse. In the wake of enhanced precision in geochronological tools, the integrated approach we apply for quantifying volcanic recurrence rates has broad utility in Earth’s deep-time record.