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| Upper Cretaceous Nanaimo Group / Denman Island |
This succession has been the focus of many paleomagnetic, isotope geochemistry, paleontology, and sedimentology studies with the aim of untangling the tectonic history and paleolatitude of the Insular Superterrane during the Nanaimo Group deposition some 90 to 65 million years ago.
One would think that these research papers would support each other in terms of that deposition. Much to our chagrin, we're still working through the strata to define both the formal stratigraphy, untangle if it was deposited in single or multiple basins and match it up with local and regional correlations.
The upper two-thirds of the succession is continuously and well exposed on Denman and Hornby islands and represents the best example of this part of the succession in the northern half of what we consider the single Nanaimo Basin. This area includes the previously only informally defined type areas for the Geoffrey and Spray formations, defined here formally for the first time with type sections and detailed descriptions. New interpretations of the geology of these islands demonstrate that previously interpreted major faults do not exist, resulting in stratigraphic and age controls that are both different and simpler than previously interpreted. The redefined stratigraphy of the northern part of the basin is remarkably similar to that of southern areas in both type and age, affirming both a single basin evolution and a single stratigraphic nomenclature.
