Simultaneous changes in carbon isotopes, sea level, and conodont biozones within the Cambrian-Ordovician boundary interval at Black Mountain, Australia

Carbon isotope profiles of marine carbonate units within the Cambrian-Ordovician boundary section at Black Mountain, western Queensland, Australia, reveal cyclical changes in δ¹³C within the Georgina basin during the boundary interval. Minimum values in the δ¹³C profile are found in strata bearing lithostratigraphic evidence for sea-level drop and also correlate strongly with conodont assemblage zone boundaries. These relations indicate that direct mechanistic links existed between carbon cycles, changes in sea level, and conodont evolution.