A PLANT-TISSUE ORIGIN FOR ULMINITE-A AND ULMINITE-B IN SASKATCHEWAN LIGNITES AND IMPLICATIONS FOR R(O)

This paper describes the petrography and organic geochemistry of Taxod iaceae wood and bark tissues within Paleocene lignites of southern Sas katchewan, Canada. The wood (secondary xylem) tissues are dominated by ulminite, which fluoresces and is solely low-reflecting (dark) variet y A. R(0) values are from 0.20 to 0.22%. The wood tissues are relative ly hydrogen-rich and oxygen-poor, have depressed T-max values (374-380 degrees C), and are rich in methoxyphenol compounds. The bark tissues are more heterogeneous in maceral and tissue compositions. They are d ominated by interlayered cork (periderm) and ''A/B'' (secondary phloem ) tissues, the latter consisting of an intimate association of ulminit e A and high-reflecting (light) ulminite B. R(0) values are from 0.24 to 0.27% for ulminite A and 0.36 to 0.44% for ulminite B. The bark tis sues are relatively hydrogen-poor and oxygen-rich and have higher T-ma x values (403-418 degrees C), and phenols are the dominant compounds. The study provides unequivocal evidence of a plant tissue origin for t he A (dark) and B (light) varieties of humotelinite macerals and revea ls fundamental problems in the A vs B classification. The existence of the humotelinite A and B varieties has significant implications for t he use of R(0) as a rank parameter, and these implications are discuss ed.