Continuous record of Upper Ordovician (Katian) to lower Silurian (Telychian) global δ¹³C excursions in the Williston Basin

Abstract

The Williston Basin retained a high-resolution record of global δ 13 C fluctuations during the ~13 Ma duration Upper Ordovician-lower Silurian, and is a possible missing link in correlations between Laurentian margins and its interior. This study integrates δ 13 C and conodont biostratigraphy to yield a high-resolution, continuous composite spanning from the Upper Ordovician Aphelognathus grandis Zone into the lower Silurian Distomodus staurognathoides Zone. From oldest to youngest, six global δ 13 C excursions are identified: (1) Whitewater (=Moe) and (2) Elkhorn (=Paroveja) in the Amorphognathus divergens Zone; (3) LHICE (KaH?) in the Aphelognathus shatzeri Zone; (4) HICE in the Ozarkodina hassi Zone; (5) Early Aeronian within the Distomodus kentuckyensis-Pranognathaus tenuis zones and (6) late Aeronian within the Psuedolonchodina expansa-D. staurognathoides zones. This δ 13 C record helps to alleviate some of the uncertainties in determining the precise order, duration and timing of events influencing the biotic, climatic, oceanic and sea-level evolution of the Upper Ordovician-lower Silurian successions across Laurentia.