1. Use of paleobiology to investigate plant biochemistry in coal
and organically preserved fossils
C. Kevin Boyce, Department of the Geophysical Sciences, University of Chicago.
The anatomy of cellularly preserved fossils can provide an underappreciated wealth of information
for geochemical studies. Tissue specific comparisons can inform questions both of paleobiology
and of the pathways leading to organic accumulations. Coal is often treated as derived primarily
from lignin, but most Carboniferous coal swamp plants had little wood. X-PEEM analyses of
fossils of the ecologically dominant tree lycopods indicate strong compositional differences
between their small amounts of woody tissue and their far more abundant cortical tissues--
suggesting the single largest contribution to coal swamp biomass was not lignified and that
lignin likely was not as dominant a biochemical input to Paleozoic coal production as assumed.
Large differences in carbonate fabric also have been found in different tissue types which may
reflect the influence of local organic matter on crystal nucleation and growth and may provide
a readily available proxy for original biochemical composition for paleontological studies.
XANES of cell walls
in different tissues
X-PEEM spectra of different tissues of a
Carboniferous fossil of a tree lycopod
(shown in cross section in the inset).
Analyses conducted at the Synchrotron
Radiation Center working with PUPA
Gilbert of the University of Wisconsin.
Carbonate crystal fabrics in different fossil tissues,
Top: polarized visible light image of (potentially
unlignified) cortical cells and infilled voids.
Bottom: X-PEEM image showing carbonate crystal
dichroism in lignified wood cells.