Onset of the Mulde Biogeochemical Event in the Midcontinent Basin (Silurian, USA)

The mid-Silurian (Homerian) Mulde Biogeochemical Event has one of the most highly refined chronologies in the Paleozoic. The turnover of marine benthic and pelagic faunas and floras that defines the biotic component of the event is associated with the initial rise of a double-peaked positive carbonate carbon (δ¹³C_carb) isotope excursion. Five previously published UPb ages constrain the duration of the first peak of the δ¹³C_carb excursion, which reaches values of up to +5.5 ‰, to as little as a few hundred thousand years. Establishing a robust process understanding of this biogeochemical event requires seamless integration of these high-precision UPb ages with intercontinental chronostratigraphic correlation to temporally compile the records of environmental change while parsing local from global drivers. Our new bio- and chemostratigraphic data from the Midcontinent Basin (USA) fine-tune the chronostratigraphic framework through the onset of the Mulde Event and refine intercontinental comparison with the gold-standard sections of Gotland (Sweden).