标题：Ordovician-Silurian Boundary Interval in the Williston Basin Outcrop Belt of Manitoba: A Record of Global and Regional Environmental and Biotic Change
摘要：During latest Ordovician to earliest Silurian time, deposition and biotas were influenced globally by environ- mental changes that led to glaciation and subsequent deglaciation in south- polar Gondwana. At the centre of equatorial Laurentia, the Williston Basin provides a record of global and regional change in an epicontinental sea. Classic localities in southern Manitoba will be compared with sites north of Grand Rapids and northeast of The Pas, including the only known exposures of the Ordovician – Silurian boundary in this vast basin. New research, integrating lithostratigraphy, biostratigraphy, and C-isotope stratigra- phy, suggests that deposits of latest Ordovician (Hirnantian) age are pres- ent and that the Ordovician – Silurian boundary is at a higher position than previously thought.
