Application of morphological lineages in Australian palynostratigraphy

Abstract

In terms of biostratigraphic subdivision dorected towards chronostratigraphic correlation, the lineage zone is of major significance. With the application of palynostratigraphy to time correlation however, morphological lineages are little used. This perhaps reflects the consideration of dispersed sporomorphs as a minor part of the total organism, studied in isolation from the total organism (often unknown), and thus with little known of their ecological associations. Additionally, trends of morphological change in dispersed spores are difficult to unravel and define. This is the result of a combination of factors including the artificial nature of morphological classifications adopted, that one morphotype can be a product of several, very different distantly related parent plants and that plant speciation is often a product of hybridization and polyploidy. Several types of morphological series have been defined from Australian Palaeozoic and Mesozoic microfloral succession. Some of these have proved to be valuable in assisting time correlation of the stratigraphic sequence while others are inherently unreliable for such correlation studies. These differences can be accounted for in terms of biological controls on small scale morphological variations. Consequently it is essential that the biological significance of a morphological lineage be assessed before accepting its value in chronostratigraphic correlation.