Determination of ancient environments by the palynological approach utilizes principles derived from

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neoecology and from statistical analyses of palynological assemblages. The environmental factors generally sought are physiography, hydrography, temperature, moisture, and substrate. Their determination involves an analysis of fossil origin, preservation, identification, association, relative abundance, and successional occurrence. Palynological fossils in a deposit are commonly derived from more than one ecology and are transported to the place of burial by gravity, wind, water, or some organic vehicle. The lithofacies in which the fossils occur are indicative of the environment of preservation and, in many cases, of the physiographic-hydrographic relations. Identifications of palynomorphs can be made at the phyla level and are valid paleoecological indicators but, with narrower taxo omic recognition, the fossils become increasingly useful in environmental studies. Specific determinations and natural-affinity associations give the best paleoecological criteria for the recognition of distinct environments. Consistent association of certain palynomorph species may be indicative of certain ecological conditions, and their relative abundance can indicate the stage of regional or local environmental development. Relative abundance, however, must not be construed as indicating the absolute abundance of the parent plant or animal from which the palynomorphs were derived. The abundance of individual fossils observed may be governed by the number of spores, pollen, statoblasts, etc. produced by the parent organism, manner and distance of transport to the place of burial, type of preservation, diagenesis of the sediments, and techniques of recovery from the rock for study. Successional stages of palynological assemblages in a stratigraphic section are related to many factors and, where these are recognized, the successional stages can indicate environmental conditions not otherwise apparent.

Pleistocene paleoecological studies give clues to techniques that may be used in Tertiary and Upper Mesozoic investigations. This is especially true if the fossils have recognizable natural affinities. When dealing with Paleozoic and Lower Mesozoic palynomorphs there are problems of organic evolution. These make environmental determinations difficult, and more empirical ecological techniques are required than with the younger fossils. Although the resulting environmental conclusions are mainly hypothetical, this information has been found useful in biostratigraphic studies.

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