Chazy (Middle Ordovician) trace fossils in the Ottawa - St. Lawrence Lowlands

Trace fossils are abundant in terrigenous, shallow marine clastic rocks in the lower part of the Laval Formation (Chazy Group) of the St. Lawrence Lowlands, and equivalent rocks (Rockcliffe Formation) in the Ottawa Valley. Most prevalent are crawling traces (Repichnia) and feeding burrows (Fodinichnia), followed by resting traces (Cubichnia) and dwelling burrows (Domichnia); systematic feeding traces (Pascichnia) are absent. The following 17 ichnogenera are reported from the terrigenous beds: Arthraria, Chondrites, Conostichus, Cruziana, Diplichnites, Diplocraterion, Isopodichnus, Palaeophycus, Petalichnus, Phycodes, Planolites, Rhizocorallum?, Rusophycus, Skolithos, Teichichnus, Walcottia?, and the new ichnogenus Caugichnus. Two of these, Teichichnus and Phycodes, occur as integral structures made by a single species of organism. Also present are 3 genera of borings: Trypanites, on a hardground developed on a calcarenite in the upper part of the Laval Formation, and Ropalonaria and Vermiforichnus, perforating valves of the orthid brachiopod Mirnella imperator Billings in the Rockcliffe Formation. Two overlapping shallow water facies are recognized: Seilacher's Skolithos facies (in the west), and the Cruziana facies to the east; the latter is subdivided into a Rusophycus subfacies (in the middle of the study area), and a Phycodes subfacies in the east.