Facies characterization and depositional architecture of a mixed-influence asymmetric delta lobe: Upper Cretaceous basal Belly River Formation, central Alberta

The Campanian basal Belly River Formation (Cycle G) of central Alberta is differentiated into two mappable facies associations (FA1 and FA2). FA1 comprises uniformly coarsening-upward successions with abundant wave- and storm-generated physical structures. FA2 forms variable and markedly heterolithic coarsening-upwards successions, dominated by current-generated structures, normal grading, convolute bedding, structureless siltstones, claystone drapes, and syneresis cracks. Both facies associations yield sporadically distributed trace fossil suites, attributable to stressed expressions of the Cruziana Ichnofacies. FA1 contains moderate-abundance and moderate-diversity ichnological suites, whereas FA2 displays low-abundance, and typically very low-diversity suites comprising predominantly facies-crossing deposit-feeding structures.