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

Paired delta C-13(carb) and delta C-13(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 (delta C-13(carb)) excursion. Our investigation provides the first detailed delta C-13(org) stratigraphy through this interval and documents a negative excursion in delta C-13(org) associated with the positive delta C-13(carb) excursion. This is consistent with the notion that the Ireviken positive delta C-13(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 delta C-13(org) trends shown herein can be reproduced globally. (C) 2007 Elsevier B.V. All rights reserved.