Chemoautotrophy as the driver of decoupled organic and carbonate carbon isotope records at the onset of the Hangenberg (Devonian-Carboniferous Boundary) Oceanic Anoxic Event

New high-resolution organic (δ 13 C org ) and carbonate (δ 13 C carb ) carbon isotope data from middle shelf deposits in southeastern Iowa demonstrate decoupled signals during the onset of the Hangenberg Event and across the Devonian-Carboniferous Boundary. High-resolution sampling captures a transient negative excursion in δ 13 C org during the initiation of rising δ 13 C carb values at the onset of the Hangenberg Event that ends prior to the...