Upper Mississippian (middle Viséan) biohermal limestones, siliciclastics, evaporites, and red beds of the lower Codroy Group (correlative with the lower Windsor Group in Nova Scotia) bevel a rugged paleokarst of Late Devonian – Early Mississippian age on the Port au Port Peninsula, western Newfoundland. Laminated limestones (Ship Cove Formation) and overlying evaporites (Codroy Road Formation) are similar to the sequence in the Bay St. George Subbasin, southwestern Newfoundland. In the Port au Port region, this sequence is laterally equivalent to biohermal limestones and plant-bearing siliciclastics of the proposed Big Cove Formation and red beds of the Lower Cove Formation. Lithostratigraphic correlation is supported by miospore and conodont biostratigraphies. Use of macrofaunal subzones is cautioned because there is evidence for the need to reevaluate the ranges of fossils that have previously been considered key indicators (e.g., Martinia galataea Bell) for parts of the Codroy and Windsor groups.The nature and lateral changes in Late Mississippian depositional environments and biofacies in the Port au Port region were the result of partial submergence of a complex predepositional topography and differential freshwater runoff (from the exposed Port au Port Ridge) creating fluctuating salinities and varying influx of siliciclastics. Limestone–evaporite sequences developed in broad, flat basins, carbonate buildups and siliciclastics accumulated in partially submerged paleokarst valleys adjacent to a rocky shoreline, and red beds formed part of the adjacent terrestrial landscape.