Filling Gaps in the Amber Record and Adding Facets to Bonebed Palaeoecology: Upper Cretaceous and Paleocene Amber Deposits from Western Canada
MCKELLAR, Ryan C; Royal Saskatchewan Museum, Regina, SK. COCKX, Pierre; University of Regina, Regina, SK, Canada
The Upper Cretaceous rocks of North America have provided diverse amber assemblages from famous sites such as Grassy Lake, Alberta (Campanian, ‘Canadian amber’), and New Jersey (Turonian, Raritan amber). However, these deposits represent disparate ecological settings separated by millions of years, which limits our ability to make faunal comparisons or assess diversity through time. Furthermore, few diverse amber deposits are known globally between the Campanian and the Eocene, limiting our understanding of how terrestrial arthropods responded to the end Cretaceous extinction event. Recent fieldwork efforts in the western Canadian provinces and adjacent states of the USA have resulted in the discovery of numerous fragile amber deposits that fill in this key time interval. These deposits are beginning to produce significant numbers of insect inclusions, yielding new species and providing palaeoecological information. The amber itself can also be analyzed to assess which groups of trees produced the fossil resin (using FTIR spectroscopy or GC-MS techniques) and what conditions the trees were living under (using stable isotope analyses of carbon to assess plant stress, and hydrogen for local precipitation patterns). When insect inclusions are combined with amber chemistry and composition analyses, these new deposits provide detailed snapshots of ancient forests, including a rare opportunity to observe soft tissue preservation and soft-bodied organisms. In terms of Canadian discoveries, new deposits have been found in the Upper Cretaceous and Paleocene rocks of Saskatchewan: the Campanian Foremost, Oldman, Dinosaur Park, and Bearpaw formations; the Maastrichtian Eastend and Frenchman formations; and the Paleocene Ravenscrag Formation. The Upper Cretaceous of Alberta has also been productive, with material coming from: the Campanian to Maastrichtian Foremost, Dinosaur Park, Horseshoe Canyon, and Scollard formations, and the Wapiti Group. Together, these deposits provide a sporadic amber record throughout the latter part of the Cretaceous and into the Paleocene. This provides detailed information from a warm temperate ecosystem that was variably influenced by the Western Interior Seaway, with some deposits extending coverage into high latitudes. Many of these deposits have been found within or adjacent to dinosaur bonebeds, providing a new source of information on the surrounding habitats.
Acknowledgements: Funding provided by NSERC Discovery Grant (R.M. and P.C.), and RSM Scholarship (P.C.).