STABLE ISOTOPE ANALYSES OF FOSSIL TEETH AND CHARCOALS INDICATE A HEAVY CARBON LOWER PERMIAN WORLD

Stable carbon and oxygen isotope compositions of over 100 fossil teeth from reptiles, amphibians and fresh-water fish (Berkeley Museum of Paleontology collections) from Lower Permian sediments in Oklahoma, Texas, and Utah have been obtained using laser ablation mass spectrometry. The stable carbon isotope compositions of a similar number of charcoals (Smithsonian National Museum of Natural History collections) from the same sediments have also been analyzed. These data constrain the carbon isotope composition of Late Paleozoic biospheric materials and, by inference, the d¹³C of contemporaneous paleoatmospheric carbon dioxide. In turn, this information is useful for paleoecological reconstructions and constraining the concentration of carbon dioxide in the paleoatmosphere.

Carbon isotope compositions of the Lower Permian teeth and charcoals are approximately 4-5 permil enriched in ¹³C relative to Cenozoic mammal tooth enamel and wood (C3 pathway) respectively. This is similar to the difference between published Lower Permian marine carbonates and comparable Cenozoic marine carbonates. The likely reason for this difference is the deposition of enormous quantities of ¹³C depleted organic matter during the preceding Carboniferous period. Isotopic compositions of the fossil teeth vary between groups of animals. Our preliminary interpretation distinguishes two distinct ecosystems: 1) A riparian canopy ecosystem and 2) A semi-arid upland ecosystem. If this interpretation is correct, the isotopic composition of teeth can be used to evaluate landscape based food sources of these Lower Permian vertebrates. The d¹³C of charcoals define a nonlinear temporal trend from the Latest Pennsylvanian through Early Permian that is characterized by a series of shifts of 1 to 4 permil.