Integrated ichnological, sedimentological, and geochronological analysis of the Late Cretaceous Upper Nanaimo Group, Saltspring Island, B.C., Canada

Integrated ichnological, sedimentological, and geochronological investigation of the Late Cretaceous Nanaimo Group, Saltspring Island, B.C., Canada was undertaken to examine the existing lithostratigraphic mapping and facies characteristics of deep-water slope deposits. Maximum depositional ages from U-Pb dating of detrital zircon grains (N=3744) provide a geochronologic framework for facies relationships studied at a cm-scale over ~1500 m of stratigraphic thickness. Passive gamma-ray emissions (K, U and Th spectra) were collected using a hand-held gamma-ray scintillometer. The results of this integrated analysis suggests that: (1) almost all of the Cretaceous-aged strata in the study area belongs to the upper Nanaimo Group; (2) the youngest zircon grains in the earliest Nanaimo Basin are Middle Jurassic in age, indicating that further study of basin evolution is needed; and (3) integrated facies analysis of thin-bedded slope deposits provides improved criteria for recognizing their different subenvironments compared to employing sedimentological observations alone.