Early Silurian positive δ¹³C excursions and their relationship to glaciations, sea‐level changes and extinction events

Abstract

Abstract Evidence is presented from the upper Aeronian, lower Sheinwoodian and middle Homerian demonstrating that positive δ 13 C excursions in the lower Silurian are the result of increased carbonate weathering and probably also enhanced burial of organic carbon coincident with sea‐level falls resulting from growth of ice sheets on the South American part of Gondwana. Graptolite extinctions are coincident with the δ 13 C excursions, whereas major conodont extinction events (Ireviken and Mulde) are not, but conversely, occur at times of high sea level. This suggests very different controls on graptolite and conodont global diversity patterns. Palynological studies suggest that netromorph acritarchs may have been opportunists that flourished during positive δ 13 C excursion intervals. Copyright © 2007 John Wiley & Sons, Ltd.