| Dispersed plant remains are small fruits, seeds, megaspores, cuticle fragments and other small plant parts which are recovered from sediments by bulk maceration and sieving. Maceration of terrestrial and marginal marine sediments from the early angiosperm-bearing Dakota Formation (Cretaceous, Cenomanian) yielded a diverse assemblage of dispersed plant fossils, consisting of sixteen species of lycopod and heterosporous fern megaspores, six species of seed and fruit cuticles, four types of bilobed cuticular structures which may be reproductive structures from some unknown Mesozoic seed plant, and two species of algal cysts. The megaspore and seed cuticle flora is similar to other North American megaspore floras of Cenomanian age, and some of the species found are index fossils for the Cenomanian, thus reconfirming the age of these deposits.;Data were collected on species abundance in samples from four different facies, representing depositional environments ranging from deltaic and estuarine to fluvial and floodplain. Fifty five productive samples from seventeen localities were studied. These data were analyzed using multivariate statistical techniques, which revealed distinct trends in the distribution of species in the sediments of different depositional environments. Some taxa are restricted to non-marine deposits whereas others commonly occur in abundance in both the marginal marine and the non-marine deposits. Those found in the marginal marine deposits were probably transported downstream from plants that grew farther inland. Some fossils are restricted to certain terrestrial environments, and the habitat of the parent plant can often be inferred from the distribution of the fossils. These results indicate that this type of paleoecological analysis, using multivariate techniques in conjunction with sedimentological and botanical evidence, will prove useful in interpretation of the paleoecology of plant fossils. |
