DIVERSE ICHNOFOSSIL ASSEMBLAGES FOLLOWING THE P-T MASS EXTINCTION, LOWER TRIASSIC, ALBERTA AND BRITISH COLUMBIA, CANADA: EVIDENCE FOR SHALLOW MARINE REFUGIA ON THE NORTHWESTERN COAST OF PANGAEA

Abstract

Abstract Diverse and locally abundant Lowermost Triassic (lower Induan, Griesbachian) trace-fossil assemblages are described and their significance for the location and characteristics of western Pangean environmental refugia are assessed. Trace fossils within the Montney Formation in northwestern Alberta and northeastern British Columbia record the activities of a wide variety of marine invertebrates. Many forms represent the dwelling and feeding traces of allochthonous storm-transported colonizers. Anachronistic forms—more typical of Paleozoic than Mesozoic successions—including Cruziana, Diplichnites, Monomorphichnus, and Trichophycus, are common. Notably these Paleozoic holdovers, as well as Rhizocorallium, Thalassinoides, and Spongeliomorpha, were likely constructed by marine arthropods. Trace fossils are rare in both shallow water (upper shoreface and foreshore) and offshore depositional settings, but are abundant in offshore transition to distal lower shoreface depositional settings. Low diversity ...