FACIES CHANGES AND PRESERVATION STATES: A CASE STUDY

D`ANGELO J A; ZODROW, ERWIN L.

Otro; Reunión de comunicaciones de la Asociación Paleontológica Argentina; 2019

The influence of facies on preservation states of plant fossils is most generally assumed in taphonomic-related studies but seldom pursued from a geochemical view. We present a study of the seed fern Neuropteris ovata (Hoffmann, 1826; specimen CBU 85?248; Palaeobotanical Laboratory, Cape Breton University) from the Late Pennsylvanian Sydney Coalfield (Nova Scotia, Canada) that occurs both as 1) opaque coalified compression in roof shale of a coal seam, and 2) transparent fossilized-cuticle in a crevasse-splay 3,5 m above the coal seam. We hypothesized that coalified compression and fossilized-cuticle are derived from divergent pathways of organic matter transformation and facies changes. A multivariate statistical model is obtained using a chemometric method: semi-quantitative Fourier transform infrared spectroscopy -FTIR- followed by data evaluation through principal component analysis. This model permits linking transparent fossilized-cuticles with oxidation due to oxygen diffusion in the sandy matrix from an oxygenenriched Carboniferous atmosphere. At the molecular level, fossilized-cuticles are mostly characterized by oxygen-containing aliphatic compounds. On the other hand, opaque coalified compressions preserved in a comparative reducing environment are characterized, at the molecular level, by a predominantly aromatic composition. Currently, we are using advanced, mathematical methods for FTIR-signal processing to refine the data for improving the obtained study model. Despite, a far-reaching conclusion is achieved highlighting that the word ?compression? without chemical definition is meaningless as a preservation term.