Methods in Peat Petrology and their Application to Reconstruction of Paleoenvironments
In order to reconstruct the environments of peat deposition in southern Florida and to better understand the coal-forming processes, it was necessary to improve the techniques for collecting and analyzing modern phytogenic sediments. The need for minimizing compaction and distortion of organic sediments during field sampling required the development of a modified piston corer. The partial vacuum created by such a piston reduces compaction and holds the sediment in proper position in the coring tubes on the downstroke as well as during the uplift. Relatively undistorted microtome sections (15μ thick) were cut from oriented samples of peat impregnated with paraffin. By comparison with reference slides of modern plant tissues, it was possible to identify the genera and sometimes the species of plants contributing to the peat even though there were only much-altered fragments of these plants present. Vertically oriented sections are especially useful, because they can be easily compared with thin sections of coals. The method proved successful for study of peats of many different compositions and textures. A field test of the environmental interpretations made from oriented microtome sections showed a very good correspondence between actual surface environments and environments which had been predicted solely from analysis of microtome sections of surface peat. However, describing the vegetation in terms of the relative proportions of particular species proved to be more speculative. A relatively close correspondence was also exhibited between paleoecological interpretations made from oriented microtome sections of peat and those made by palynologic analyses. However, each method has its advantages, and interpretations based on the combined data of both methods are superior to those obtained by using either one alone.