Geochemical analyses of amber associated with dinosaur bonebeds in central North America

Abstract

For a long time, amber has been praised for its ability to preserve organic inclusions in spectacular detail. More recently amber has been analysed from a geochemical point of view, to gain a better understanding of the environments in which this fossilized tree resin was produced. Due to lack of fossils and detail in known paleo-environments three meters below the Cretaceous-Paleogene (K-Pg) boundary, amber geochemistry helps to fill in a gap of the fossil record. This study consists of the analysis of carbon and hydrogen stable isotopes from amber in bone beds, as well as Fourier Transform Infrared Spectroscopy (FTIR) and more traditional means of paleontological and sedimentological analysis from sites in Saskatchewan, Alberta, Montana, and North Dakota. The main aim is understanding how this geographic region of the world was changing during the Cretaceous period. Results indicate that Cretaceous ecosystems, during the last 15 million years of the Cretaceous, were relatively quite stable; however, the δ13C values leading up to the Cretaceous-Paleogene extinction boundary appear to show that many of the geographic region’s resin producing plants were experiencing some form of ecophysiological stress. They also indicate that the Western Interior Seaway underwent transgressions and regressions throughout the Cretaceous and that it was still actively playing a part in the terrestrial ecosystem’s precipitation up until the end of the Cretaceous period, although with varying degrees of influence. Finally, the data indicate that throughout the Cretaceous the main amber producing plants were trees from the Cupressaceae family. Using the geochemical information from amber along with the sedimentological and paleontological data from each of these sites, details of the environments leading up to the end Cretaceous extinction event can be constructed.