CRITERIA TO DISTINGUISH PARAUTOCHTHONOUS LEAVES IN TERTIARY ALLUVIAL CHANNEL-FILLS

The plant taphonomic character of fluvial channels in the Upper Oligoc ene strata of the Weisselster basin, near Borna, Germany, has been stu died to determine if concentrated macrofloral-bearing intervals repres ent allochthonous or parautochthonous accumulations. Single bedding pl anes or leaf accumulations that represent a single cluster of leaves, the taphonomic signature of leaf fall, were examined representing 1.6 m(2) of surface area. Unequivocal autochthonous elements, such as the floating water fern, Salvinia, were excluded from the data set. Each a ssemblage was evaluated separately. Criteria useful in identifying par autochthonous leaf assemblages include: (1) a heterogenous mixture of plant parts with phytoclast concentration increasing upsection in the fill; (2) a log-normal distribution of leaf sizes in the assemblage; ( 3) a gaussian or log-normal distribution of leaf size in all dominant taxa; (4) a random directional orientation of leaves or, in the case o f taxodiaceous conifers, short shoots on any particular bedding surfac e; and (5) a biased leaf-surface orientation (one leaf surface predomi nantly facing upwards). Actualistic data are provided as justification for establishing these criteria.