Development of the Platte River Bottomland in South Central Nebraska
| Autor: | G. E. Condra |
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| Rok vydání: | 1931 |
| Předmět: | |
| Zdroj: | Annals of the Association of American Geographers. 21:101-105 |
| ISSN: | 1467-8306 0004-5608 |
| DOI: | 10.1080/00045603109356934 |
| Popis: | G. E. CONDRA The Platte, in its course in south central Nebraska, is widely known as an overloaded river, and it is generally held that its broad valley-floor is an alluvial plain developed in a former deep valley by the river. Also, the lowering of the river in this area, to a dry bed in late summer, is supposed to be caused by excessive evaporation and diversion for irrigation. Investigations made by the Nebraska Geological Survey and the Nebraska Water Survey disprove most of the generally accepted views of the environing features of the Platte. It would seem, therefore, that as Geographers you may be interested in the results of this investigation. This paper is only a review of the main points brought out in the study of the Platte River and the Platte Valley. A more complete statement is found in Bulletins 3 and 4 of the Conservation Department of the Conservation and Survey Division of the University of Nebraska, which bulletins are free upon request. Also, there is further treatment of the subject in the 1930 Report of the Nebraska Irrigation Association, and in forthcoming bulletins of the State Geological Survey of the Conservation and Survey Division of the University of Nebraska. The first point raised here is in regard to the nature and origin of the river bottom land. That this was not aggraded by the Platte, to the depth generally supposed, is evidenced by the following: 1. The so-called alluvium of the valley floor consists of two thick gravel sheets separated by a fairly persistent sheet of silt and clay, all of which extend through this stretch of the valley and out under the broadening uplands. They have a combined thickness of 100' to 200', resting on bedrock. 2. The gravel sheets are of Pleistocene age as shown by mammalian fossils brought up from water wells and by pumping and dredging at sand pits. It is certain, therefore, that the sand and gravel deposits under this area of the Platte Valley, up to near the surface, are of Pleistocene age and not recent alluvium. To Dr. A. L. Lugn belongs much of the credit for this discovery. |
| Databáze: | OpenAIRE |
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