Ichnology of the Winnipeg Formation, southeast Saskatchewan: a glimpse into the marine infaunal ecology of the Great Ordovician Biodiversification Event

Abstract

The ichnology of the Middle Ordovician Winnipeg Formation has been analysed based on the study of cores from five wells drilled in southeast Saskatchewan (Canada). Six sedimentary facies, ranging from upper shoreface to lower offshore settings in a shallow-marine environment, have been characterized. Ichnological attributes are consistent with those in currently proposed models for shallow-marine wave-dominated settings, but ichnodiversity is lower than in post-Palaeozoic settings. Low ichnodiversity in the Winnipeg Formation most likely reflects evolutionary factors rather than environmental controls. Interestingly, low-energy, distal deposits of the Winnipeg Formation display intense degree of bioturbation, reflecting a welldeveloped mixed layer and underscoring the importance of the Great Ordovician Biodiversification Event in terms of sediment mixing.