Ecological Conditions Accompanying Loess Deposition in the Great Plains Region of the United States

There has been lack of agreement concerning the ecological conditions of loess deposition in the central Great Plains region. Data from the molluscan faunas and the physical nature and distribution of the deposits are reviewed. They indicate that the surface of deposition was well vegetated with forest conditions along the eastern Missouri Valley and a grass cover on the western plains; the climate was somewhat more moist, and the temperature (although slightly cooler, on the average) had less severe extremes than at the present; and the primary source of the silt was in the outwash-carrying valleys during an episode of continental glaciation.