Plant Microfossils from the Bruhn Lignite

Introduction: The collection and preliminary examination of fossiliferous material from West Tennessee, begun in the fall of 1952 with the aid and encouragement of Dr. A. J. Sharp, convinced the writer that the opportunity to extend present knowledge of early vegetational history in the area was substantial. Despite the fact that the region west of the Tennessee River has yielded a considerable amount of plant fossil evidence, mainly in the form of leaf impressions, many unsolved problems remain.

From the botanical point of view, the identification of fossil plants based on the single criterion of leaf morphology, as has been attempted in many cases, has serious limitations (Odell, 1932; Arnold, 1947, pp. 338-339) Furthermore, the restricted representation inherent with this mode of fossilization, and the special set of conditions under which it is operative have led to qualitative and quantitative interpretations that are questionable.

In recent years, the vulnerability of time-honored correlations procedures has been recognized by many geologists. Paleontology developed as a stratigraphic tool with little regard for the biological aspects of the plants and animals involved. The inevitable consequence of this stereotyped approach, which led ultimately to fallacious deductions, has been a general distrust of paleontological data. The need for reevaluation of time-stratigraphic concepts involving paleontology has been recently stressed by Allan (1948) and Newell (1953).

The increase in knowledge provided by modern geologic methods has brought about a realization that the simple stratigraphy envisioned by earlier workers such as Berry (1920, p. 333) in West Tennessee and other parts of the embayment region is not consistent with the facts. More recent geologic investigations have further emphasized the necessity for re-examining and implementing where possible the paleobotanical evidence on hand.

With these problems in mind, the writer undertook a study of fossil pollen and spores isolated from lignites and lignitic clays from West Tennessee. The wealth of such materials available for collection, and their widespread geologic occurrence made systematic organization of the total study essential. Consequently, the decision was made to select material from a particular geologic horizon that would provide a logical frame of reference upon which to establish definite geological and botanical relationships. The initial investigation is described in this thesis.