The Early Ordovician bathyurid faunal province includes North America, Greenland, Spitsbergen, Scotland, and western Ireland and Norway. Dominant provincial lithofacies and biofacies include a Dolomite Suite with molluscan‐stromatolite fossil content rimmed by Limestone Belts with dominantly trilobite‐brachiopod faunas on a platform. Shale Belt rocks bearing graptolites, deposited on the platform slopes, rim the Limestone Belts. Volcanic rock‐rich terrain partly borders the Shale Belts. Correlation between the lithofacies indicates that change from an expansion to contraction phase of a proto‐Atlantic coincided with uplift of the carbonate platform and with tectonic activity in the Atlantic volcanic rock rich terrain. Brachiopods replaced trilobites as dominant faunal elements in more shallow platform waters at the same time. High trilobite diversity remained in deeper waters near platform margins. The changes took place in Earliest Mohawk‐ian (Latest Arenig‐Earlies