Although widely recognized, the nature and rate of transitions between end-member “greenhouse” and “icehouse” climatic states through geologic history remain enigmatic. In this paper, Holland and Patzkowsky explore the style of cyclicity in the Late Ordovician Bighorn Dolomite, representing a time interval with isotopic evidence for a prolonged ice buildup despite elevated pCO2 and global temperatures. They document how this succession preserves systematic changes in the presence and type of cyclicity and subaerial exposure. The results of this study suggest that the cyclicity in the Bighorn Dolomite closely reflects the rate and character of this short-lived, but important, paleoclimatic transition, and illustrate how shallow-water carbonate successions provide insight into other climate transitions.
Sequence architecture of the Bighorn Dolomite, Wyoming, U.S.A.: transition to the late Ordovician icehouse by Steven M. Holland and Mark E. Patzkowsky