Document Type



The fossils of representative sections of Peorian loess in Iowa have been examined in detail for the purpose of determining the conditions under which the loess was deposited. In most cases samples were collected at six inch intervals. The shells, pulmonate gastropods, were washed, identified, and charted in order of their vertical occurrence. The majority of species have equivalent modern forms whose habitats are known. Assuming that their mode of living was approximately the same as in the period of loess deposition, ecological conclusions may be drawn. Each section gives a history of local change of moist and dry conditions to which the flora and fauna adapted themselves as the loess accumulated. Taken collectively the group of fossils indicates that the loess was deposited upon a rising succession of forest and prairie floors whose characters were not essentially different from those in the state today, and that they lived in a climate which could have a mean average of ten degrees lower than the present. Apparently the temperature which caused the melting of the Iowan ice sheet and provided the material from which the loess is derived was favorable from the beginning for the development of plant and animal life at not a great distance from its retreating border.

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Journal Title

Proceedings of the Iowa Academy of Science





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©1939 Iowa Academy of Science, Inc.



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