CHEMOSTRATIGRAPHIC EVIDENCE OF HIGHER-PLANT EVOLUTION IN THE TARANAKIBASIN, NEW-ZEALAND

Correlation between palynological and biomarker records of higher-plan t development during the Cretaceous and Paleogene in Taranaki Basin, N ew Zealand is good. Gymnosperms, particularly podocarps, were the chie f members of coastal plain swamp flora during the Late Cretaceous, and contributed significant quantities of diterpanes, often dominated by isopimarane, to organic-rich sediments. Angiosperms increased in relat ive abundance through the Paleocene and became the dominant higher pla nts in the Eocene; their contributions to coaly sediments are characte rized by various triterpanes, particularly 18 alpha(H)-oleanane and it s C-24 A-ring degraded counterpart. This change in dominance of higher -plant groups can be followed by the use of an angiosperm/gymnosperm i ndex (AGI) based on the relative concentrations of selected triterpane s and diterpanes in m/z 191 and m/z 123 mass chromatograms. Plant biom arker distributions do not provide as precise age indications as do po llen assemblages, but they may be more representative of the vegetatio n growing in a particular area of a peat swamp.