Pollen Analysis and the Cenozoic

Abstract

As a source of pollen and spores, the paleoecologist may utilize marine, lacustrine, alluvial, aeolian, cave, and cultural deposits, in addition to the lignites and peats of early 20th-century investigations. The variety of pollen-bearing sediments is much greater than generally imagined. Ecologists should realize that it is impossible to identify most species and even many genera by pollen and spores alone. Qualitative inventories of micro-floras are useful, but the use of percentage data offers greater promise in the study of vegetation history. For proper interpretation of fossil pollen percentages, a detailed study of both species composition and the pollen rain of natural plant communities is essential. To illustrate the relationship between plant ecology and fossil microfloras we have presented our findings in 3 Cenozoic deposits. A 960-m core from the Los Angeles Basin revealed changes in pine-pollen content and a relatively high content of herb and shrub pollen. Pollen samples from lacustrine, leaf-bearing Miocene outcrops of the Columbia Plateau, Oregon, included several genera not known as megafossils. The pollen counts provided an independent estimate of ancient forest composition, readily compared with the pollen rain of existing forests. The results modify but do not seriously alter Chaney''s interpretation of a mixed deciduous forest with both needle-leaved and broad-leaved species, quite similar to the mixed mesophytic forest communities to be found today on parts of the Atlantic coastal plain in the southeastern U. S. Pollen analysis is effective in documenting Pleistocene conditions far beyond the continental ice sheets in regions thought by some authors to have escaped the influence of glacial climatic change. Pluvial lake beds in western North America contain a pollen record revealing major changes in Pleistocene vegetation zones. These changes were comparable in magnitude to those known from the fossil record at higher latitudes near the glacial boundary.