Early Silurian paired δ13Ccarb and δ13Corg analyses from the Midcontinent of North America: Implications for paleoceanography and paleoclimate

Paired δ13Ccarb and δ13Corg samples from well-preserved marine carbonates of the Wayne Formation in central Tennessee were analyzed to test a previously proposed model of relative changes in atmospheric pCO2 during the well-known Ireviken (early Wenlock) positive carbon isotope (δ13Ccarb) excursion. Our investigation provides the first detailed δ13Corg stratigraphy through this interval and documents a negative excursion in δ13Corg associated with the positive δ13Ccarb excursion. This is consistent with the notion that the Ireviken positive δ13Ccarb excursion was associated with elevated global temperatures that began during an icehouse–greenhouse transition. Although our data are consistent with predictions made by the Silurian oceanographic model [Jeppsson, L., 1990. An oceanic model for lithological and faunal changes tested on the Silurian record. J. Geol. Soc. (Lond.) 147, 663–674], a link to global changes in atmospheric pCO2 remains tenuous until it can be shown that the δ13Corg trends shown herein can be reproduced globally.