Stratigraphy is the branch of geologic science that has to do with the definition and description of major and minor natural divisions of rocks, mainly sedimentary, and interpretation of their significance in geologic history. It involves determination of the sequence of rocks, both locally and in the general time scale, tracing their areal distribution, observation of lateral and vertical variations in their characters, correlation of equivalent but possibly widely dissimilar units, and, finally, study of conditions or geologic events that are involved in their genesis. There are no other branches of geology to which stratigraphy is not more or less intimately related, both depending on them and serving them. It is not well to assert that stratigraphy, rather than any other member of the geologic body, represents the heart, but it is evident to everyone that the subject of geologic history, which is the fundamental objective of stratigraphic research, is vital to all divisions of earth science.
Emphasis should be given to the fact that stratigraphy is by no means a mere compendium of multitudinous data, interesting or not, on local thicknesses, lithologies, structural relations, and fossil contents, burdened as a whole by myriads of terms for rock units and by long lists of fossil names that are mostly or entirely unfamiliar. Unfortunately, such a notion exists in the minds of many whose special work lies in other fields. It is true that these things appertain to stratigraphic study. Conclusions must be soundly based on local details. The forbidding magnitude of this aspect of Stratigraphy comes from its encyclopedic scope in embracing the entire geologic column of the whole globe. No one can be well acquainted with more than a relatively small segment of this vast field. He should have thorough understanding of principles, general knowledge of important observations and conclusions, and a special acquaintance with data bearing on his own particular studies.
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Published in celebration of the Geological Society of America’s 50th anniversary, this 578-page volume presents the progress in geology from 1888 to 1938. Written to serve as a comprehensive summary, both for the generalist and the specialist, it explores the fundamental fields of geology, including physiography, glacial geology, oceanography, invertebrate paleontology, vertebrate paleontology, prehistoric archeology, paleobotany, stratigraphy, sedimentation, structural geology, pre-Cambrian, mineralogy, petrology, volcanology, geochemistry, general geophysics, seismology, ore deposits, petroleum geology, exploratory geophysics, and engineering geology.