Читать книгу The Economic Aspect of Geology - C. K. Leith - Страница 12

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Stratigraphy and paleontology are concerned with the sedimentary and life history of the earth. The determination of the ages of the earth's strata and of the conditions of their deposition is required in the practice of economic geology. For example, a detailed knowledge of the succession of rocks and their ages, as determined by fossils and other stratigraphic evidence, is vital to the interpretation of conditions in an oil or coal field, and to the successful exploration and development of its deposits. The success of certain paleontologists and stratigraphic specialists in oil exploration is an evidence of this situation. Certain iron ores, phosphates, salts, potash, and other minerals, as well as many of the common rocks used for economic purposes, are found in sedimentary deposits, and require for their successful exploration and development the application of stratigraphic and paleontologic knowledge.

Closely related to stratigraphy (as well as to physiography, see pp. 6–10) is the study of sedimentation—i.e., the study of the physical, chemical, climatic, and topographic conditions of the deposition of sediments. This is coming to play an increasingly large part in geologic work, and is essential to the interpretation of many mineral deposits, particularly those in which stratigraphic and physiographic questions are involved.

Still another aspect of the problem of stratigraphy and sedimentation is covered by the study of paleogeography, or the areal distribution of the faunas and sediments of geologic periods caused by the alternating submergence and emergence of land areas. In the search for the treasures of sedimentary deposits, a knowledge of ancient geographies and of ancient faunas makes it possible to eliminate certain regions from consideration. From a study of the faunas of eastern Kansas and Missouri, and of those along the eastern part of the Rocky Mountains, it has been inferred that a ridge must have extended across eastern Kansas during early Pennsylvanian time—a conclusion which is of considerable economic importance in relation to oil exploration.