Ecological Interpretations of Pliocene and Pleistocene Stratigraphy in the Great Plains Region

Reprinted from American Journal of Science, v. 255, no. 1, 1957. From the Abstract: In the Great Plains the succession of gross ecological conditions through Neogene and Quaternary time may be interpreted from the stratigraphy, geomorphological history, buried soils, and fossil mollusks and plants. A mild humid climate prevailed over a late-mature erosional topography in earliest Neogene. Progressive reduction of topographic relief and lowering of the regional water table, accompanied by an almost uniform drying of the climate, followed. Semiarid, rigorous conditions existed on the constructional plain, temporarily at erosional equilibrium, at the end of the Tertiary. A sharp reversal of climatic trend accompanied by stream incision and minor alluviation marked the beginning of the Pleistocene.