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Accueil du site → Master → Etats Unis → 1965 → A geologic study of Little Gobi Desert, Pottawatomie County, Kansas

Kansas State University (1965)

A geologic study of Little Gobi Desert, Pottawatomie County, Kansas

Ardell, Robert James

Titre : A geologic study of Little Gobi Desert, Pottawatomie County, Kansas

Auteur : Ardell, Robert James

Université de soutenance : Kansas State University

Grade : Master of Science (MS) 1965

The "Little Gobi Desert" of Pottawatomie County, in northeastern Kansas, has long been considered a Pleistocene dune deposit, although it has received only cursory attention with no attempt at a detailed study being made. The primary object of the study was to postulate the origin of the sand, mode and time of deposition. A detailed topographic map was constructed by use of a plane table and alidade and diagrammatic cross sections were assembled from data collected through augering. Field observations of the area proved most valuable. A concentration of erratic gravel was found at the base of the sand immediately above a residual chert gravel formed on the Florence Limestone Member of the Barnseton Formation, Chase Group, Gearyan Series, Permian System. No cross bedding was observed in the sand, but a peculiar lamination of iron-enriched bands was observed occurring at intervals of two to four inches. The deposit, where dissected by erosion, exhibited layers of clay and silt with the characteristic blocky structure common to loess. Samples collected were studied for fossils, grain size distribution, mineralogy, grain roundness, and surface textures. Roundness varied from rounded to well rounded for the median grain size of all samples. All sand of median grain size was well frosted to frosted. All samples studied were barren of fossils. The mineralogical composition was determined by standard mineral separation techniques and microscopic examination. The heavy mineral assemblage of four selected samples averaged .81^ of the total sample weight. A pronounced enrichment of opaques (magnetite and ilraenite), 30^, and garnets, 12.5/^. was found in the heavy mineral fractipn. The light fraction of the samples studied displayed a Ioxit concentration, 3.75^. 0- chert. The opaque and garnet enrichment and chert deficiency are characteristic of knovjn glacially derived sediments in the area. It can be concluded from the combination of field observations and laboratory study that the "Little Gobi Desert" is late Kansas or early Yarmouth in age and an eolian deposit derived for the outwash plain of the Big Blue River.

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