INVESTIGATIONS OF THE NATURE AND PROVENANCE OF MINERAL AND CARBONACEOUS MATERIAL IN FOSSILIFEROUS CHERTS : REVISITING THE 1.9 GA GUNFLINT FORMATION

Much of our understanding of early life and ancient paleoenvironments come from sedimentary rocks that contain fossiliferous chert. The microfossils in these cherts are typically defined by morphologies that are comparable to modern microbial cells along with the presence of biogenic carbonaceous compounds. Problems can arise when such structures viewed under a microscope are misinterpreted due to optical effects. Also, abiogenic and biogenic carbonaceous matter can share similar geochemical and spectroscopic characteristics. The conflict within the early life debate as to the nature of microfossils is redefining techniques and protocols to analyze these samples. Typically in this field new methods are initially used on young samples of unambiguous provenance. To this ends we are using high-resolution imaging and micro Raman spectroscopy on chert samples from the ~1.9 Ga Gunflint Formation as a preliminary investigation into the nature and provenance of the mineral and carbonaceous material. We will then begin a comprehensive suite of analysis using state of the art bulk and in-situ instrumentation to set a baseline by which early fossils can be measured. The wide array of morphological microstructures, carbonaceous components, and mineral assemblages in the Gunflint samples provide the perfect testing ground for these techniques, and the results give much needed information for microfossil identification in these and other biologically significant rocks.