Early Silurian paired δ13C carb and δ13C org analyses from the Midcontinent of North America: Implications for paleoceanography and paleoclimate

Abstract

Paired δ 13C carb and δ 13C org 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 pCO 2 during the well-known Ireviken (early Wenlock) positive carbon isotope ( δ 13C carb) excursion. Our investigation provides the first detailed δ 13C org stratigraphy through this interval and documents a negative excursion in δ 13C org associated with the positive δ 13C carb excursion. This is consistent with the notion that the Ireviken positive δ 13C carb 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 pCO 2 remains tenuous until it can be shown that the δ 13C org trends shown herein can be reproduced globally.