palaeoenvironment

palaeoenvironment Reconstructions of ancient geographies are essentially models of the distribution of palaeoenvironments, and the postulated relationships of these environments must comply with the general spatial relationships of modern environments. Such reconstructions are interpretations of the lithological and other properites of the rocks within the area studied. They are limited by the amount and kinds of data available, and they must fit into the geological history of the area.

For the most part, the study of palaeoenvironments is associated with the need to understand the origin of rock formations, especially fossiliferous sedimentary rocks and volcanic rocks, or the conditions under which past floras and faunas existed. Many sedimentary processes are highly discontinuous or episodic, and the rate of deposition of many geological formations is consequently uncertain or hypothetical. The flow of energy within the environments where this occurs is likely to be uneven or discontinuous and may be due to factors originating well beyond the area of study. The (physical) energy regime is important to the biota of any environment and to the transport and deposition of organic material. Thus the type and state of preservation of fossils is significant in interpretation of the palaeoenvironment.

Palaeoenvironmental reconstruction begins with the assembly of all available data. These are then compared with the data of modern well-understood environments and environmental processes. The best available fit is then chosen, but modifications to account for rock properties or features not explicable by this means have to be added and, if possible, tested against the acquisition of new data. Hutton's classic principle that ‘the present is the key to the past’ has to be applied with due circumspection, not only in regard to the physical and chemical aspects of ancient environments but also where the interpretation of organisms (fossils) in those environments is concerned.

D. L. Dineley

Bibliography

Prothero, D. R. (1990) Interpreting the stratigraphic record. W. H. Freeman, New York.
Reading, H. G. (ed.) (1996) Sedimentary environments (3rd edn). Blackwell Scientific Publications, Oxford.