THE ULTRASTRUCTURE AND MORPHOLOGY OF CHUARIA AND ITS IMPLICATIONS ON THE TAPHONOMY OF CARBONACEOUS COMPRESSIONS

Carbonaceous compressions are a common mode of fossil preservation throughout the Proterozoic and are the mode of fossilization for the famous Lagerstätten of the Cambrian. Despite this fame, little is known about how the taphonomic process happened, or why the preservational style largely disappeared after the Cambrian. This study is a twofold effort to deduce the details of carbonaceous compression taphonomy while reexamining the morphology and chemical structure of a typical Proterozoic carbonaceous compression fossil: Chuaria. Like its mode of preservation, Chuaria, a genus of Proterozoic macrofossils, is well-known, but little understood. They have a large range, from the Mesoproterozoic into the late Neoproterozoic, but their simple morphology of a mere carbonaceous circle has not presented itself to advanced research over the years. However, in this current study Chuaria's simple morphology lends itself as the perfect candidate for analysis, since its single tissue type eliminates the variables inherent from analyzing an organism with multiple tissues, each of which may be preserved differently. To gain a clearer picture of Chuaria's morphology and taphonomy, these fossils will be analyzed elementally with ESEM-EDAX, isotopically with SIMS, and with traditional thin sectioning and light microscopy. Also, Raman microprobe will be used to analyze the degree of graphitization of the Chuaria, and their microscopic structure will be examined externally with ESEM, and internally with a TEM. Since location-specific and taxon-specific taphonomic variables are sure to be present, Chuaria in three different sites in two different localities in the Doushantuo Formation of South China are being compared. With such a large amount of data from several different sites, we will be able to offer a more complete picture of the structure and chemistry of Chuaria than has been available before. At the same time, we will be able to piece together the diagnostic details of carbonaceous compression taphonomy.