Towards an Integrated Biostratigraphic Zonation for Upper Jurassic-Cretaceous Strata of the Boreal Regions: Recent Research Results from Northern CA

James Haggart

As global climate moderates, interest in petroleum exploration in Arctic regions is on the rise. Models of basin history and resource accumulation for these regions require a detailed understanding of depositional events, tightly constrained by rigorous age control. Although advances in radiometric dating and isotopic correlation have improved understanding of the ages of Upper Jurassic-Cretaceous stratigraphic units of the Arctic regions, correlation of these strata still relies primarily on biostratigraphic analysis. Most existing Arctic biostratigraphic frameworks apply to local areas only and generally focus on a single fossil group. Adding to these obstacles is the difficulty of correlating differing lithologic units and facies, which often preclude some fossil types. To overcome such challenges, the GSC’s GEM-Energy program and field programs of CASP have undertaken studies to improve biostratigraphic correlations of Upper Jurassic-Cretaceous strata of northern CA. We have examined old and new collections from the northern Yukon Territory, Northwest Territories, and Nunavut regions and have identified molluscan taxa present in Lower and Upper Cretaceous strata (Eagle Plain Gp; Christopher Fm; Kanguk Fm) previously unknown in the Arctic region, including scaphitid, desmoceratid, and gaudryceratid ammonites, and inoceramid bivalves. These taxa have helped to constrain ages of associated microfaunal and -floral assemblages, and to improve understanding of the sequence stratigraphy and depositional environments. Some taxa are also found commonly in more southerly parts of the North American Western Interior Seaway, indicating paleoenvironmental linkages with those regions. Other taxa provide biogeographic ties with European type sections, helping to refine the ages of locally endemic faunas. Faunal distributions are likely related to changing climatic regimes and sea-level high stands during Cretaceous time. As part of our research, we have developed a palynological biostratigraphic framework, locally with associated inoceramid bivalves, for Albian-Maastrichtian strata of the Baffin Bay region of the eastern Canadian Arctic (Eclipse Gp). These rocks can be correlated with those of West Greenland (Nuussuaq Gp), strata with more abundant ammonites and inoceramids, allowing more precise correlations with European type sections. Gastropods and other faunal components found in Upper Cretaceous strata of Eclipse Gp help to assess depositional environments; these fossils are also found in strata of the Nuussuaq Gp, thus providing regional stratigraphic linkages. Further biostratigraphic field studies, integrated with isotopic analysis, radiometric dates, and review of existing faunal collections, should refine the stratigraphic ranges of index taxa and identify environmental factors which control their distributions. Our ultimate goal is to work with scientists from other countries to develop a better understanding of the complex geology of the Arctic and surrounding regions.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013