John C. Frye

PETROGRAPHY OF THE PEORIA LOESS IN KANSAS

The surficial material throughout one-third of Kansas is the Peoria silt (loess) member of the Pleistocene Sanborn formation. Samples of this loess from an area 400 miles east-west by more than 200 miles north-south, which have been analyzed for particle size, chemical composition, and mineral constituents, show that major constituents of the silt-size fraction are quartz, feldspars, volcanic-ash shards, carbonates, and micas; quartz constitutes more than half the volume. A large suite of secondary minerals is present. The clay fraction consists of montmorillonite, illite, calcite, quartz, and feldspar, with a trace of a kaolinite mineral. Evidence used to determine source areas includes (1) progressive linear change in texture; (2) geographic variations in thickness; and (3) minor geographic differences in composition. The Platte River Valley is identified as the primary source for the Kansas region, and the Arikaree, Arkansas, and Republican valleys as important supplementary sources. The Missouri is the predominant source in the northeastern corner of Kansas. Other principal valleys, which lacked glacial outwash, were not source areas of Peoria loess in Kansas.

Correlation of Pleistocene Deposits of the Central Great Plains with the Glacial Section

Integration of Pleistocene chronologies of the central Great Plains and the glaciated area is a major problem of late Cenozoic stratigraphy in North America. Lenticular deposits of volcanic ash associated with fossil mollusks occur in both regions and furnish a widespread datum for interregional correlations. The ash lentils, collectively called Pearlette, can be differentiated petrographically from other late Cenozoic ash deposits of the Plains region and have been studied at localities extending from southeastern South Dakota to northwestern Texas. The associated molluscan fauna possesses an unforeseen degree of uniformity and stratigraphic significance. The Pearlette ash and faunal zone occurs above Kansas till and below Loveland loess and Iowa till in the Missouri Valley region and is judged to be early Yarmouthian in age. A modification of stratigraphic names for Kansas contributes to uniformity of terminology in the Plains region.

Stratigraphy of the Late Pleistocene Loesses of Kansas

The post-Yarmouthian Pleistocene of Kansas is characterized by extensive loess sheets which contain buried soils. The loesses and associated fluvial deposits are classed in Kansas as Crete, Loveland, Peoria, and Bignell members of the Sanborn formation. Based on lithologic characteristics, sequence, content of fossil mollusks, and stratigraphic continuity of buried soils, the members are identified throughout their extent in Kansas. Also trustworthy correlations with late Pleistocene deposits in Nebraska and Iowa, including the type Bignell and Loveland loesses, can be made. The Peoria loess of Kansas is shown by faunal evidence to be equivalent to the Peoria (Iowa and Tazewell) loess of central Illinois.

Petrographic comparison of some loess samples from western Europe with Kansas loess

ABSTRACT Fifteen samples of loess collected in 1952 in Italy, France, Germany, and Belgium were studied by mechanical and chemical analysis, X-ray diffraction, and light and electron microscopy. These data are compared and contrasted with similar data from 47 samples from Kansas and Nebraska. It is shown that in spite of the similarities of the loess of the two regions in field appearance, relationship, buried soil profiles, texture, and stratigraphy, the mineralogy of the European samples contrasts strongly with that of the Kansas samples. Abundant montmorillonite and volcanic ash shards in the Kansas samples are the most striking points of difference, but strong variations are also noted in other minerals of the coarse fraction as well as in other of the clay minerals.

Pleistocene succession of the central interior United States

Abstract The Quaternary of the continental interior of the United States is characterized by deposits from glacial ice, with associated outwash and eolian deposits, and by alluvial deposits produced by the same climatic pulses. Erosional incision of valleys occurred early in the glacial pulse, outwash deposition during the waning phase of the pulse, and soil formation during times of relative stability between the glacial pulses. These features of deposition, erosion, and soil formation are presented in a series of curves. One way the marine record could be correlated with that of the continental interior is to compare and match the physical records of both environments.

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.

Petrography of the late Tertiary volcanic ash falls in the central Great Plains [Kansas-Nebraska]

ABSTRACT Lenticular deposits of volcanic ash in the Miocene and Pliocene strata of western Kansas and western Nebraska are described petrographically. These include 14 ash falls of known stratigraphic position. All the ash studied is classed as vitric tuff and most of the falls are rhyolitic in composition. A regular or progressive change through time in the character of the ash does not occur. Ash falls are particularly common in the lower half of the Ash Hollow member of the Ogallala formation where it is estimated that volcanic material constitutes more than three percent of the volume of the sediments.

The High Plains Surface in Kansas

The High Plains extend in a north-south belt for nearly a thousand miles (Fenneman, 1931, map) from south Texas to southern South Dakota and comprise the most extensive section of the Great Plains physiographic province. Western Kansas lies within the central High Plains (Fig. 1). This area, and the Llano Estacado of northwestern Texas and east-central New Mexico are probably most representative of the topography generally considered typical of this section (P1. I). In these areas the High Plains are actually a partly dissected high plateau, sloping generally toward the east and southeast, the region as a whole being characterized by broad reaches of flat, undissected and in many places undrained uplands between the valleys. The major valleys that cross this plateau are broad and have gentle side slopes that extend downward to relatively narrow flats. Minor valleys in many places are steep-sided narrow canyons. The Texas and New Mexico portion of the High Plains is terminated abruptly on the east and west by sharp escarpments capped by the Ogallala formation (Pls. 2B and 3B). In southern Kansas, Fennemans (1931) eastern boundary of the High Plains is drawn at a minor topographic break located some 20 to 25 miles west of a prominent dissected escarpment in his Plains Border section. Northward, along the Arkansas Valley no perceptible topographic feature is found to mark the eastern limit of Fennemans High Plains. Still farther north, in central and northern Kansas as far as the Nebraska line, the eastern margin is gradational across the belt of country called by Fenneman the Plains Border section (P1. 2C). This section contains two irregular east-facing escarpments produced by the eastern outcrop of the Fort Hays limestone (P1. 3A) and the Greenhorn limestone, but the eastern limit of the Ogallala formation produces an escarpment at only a few places. EARLY CONCEPTS OF HIGH PLAINS SURFACE

The late Woodfordian Jules soil and associated Molluscan faunas

The Jules Soil formed during the late Woodfordian episode of maximum glacial retreat in the Lake Michigan Glacial Lobe during the interval between 15,500 and 16,500 radiocarbon years B.P. The soil is directly radiocarbon dated and stratigraphically framed by a group of dates. The molluscan faunas above and below the soil indicate a cool, moist climate. The significantly higher content of expandable clay minerals (montmorillonite) in the Jules Soil than in the loess above and below indicates that there was a decrease in Lake Michigan outwash discharged to the Illinois Valley during the episode of soil formation.

Note 27--Morphostratigraphic Units in Pleistocene Stratigraphy: STRATIGRAPHIC COMMISSION

A morphostratigraphic unit is a body of rock that is identified primarily from the surface form it displays; it may or may not be distinctive lithologically from contiguous units; and it may or may not transgress time throughout its extent. It may or may not represent a climatic episode that can be traced widely, as for a geologic-climate unit. Morphostratigraphic units in glaciated areas are moraines, outwash aprons, and associated forms, whereas the term also can be applied to alluvial terrace deposits, alluvial fans, lake plains, beach ridges, pediment veneers, and other such deposits. These units serve a need long apparent to those working in the bordering fields of geomorphology and stratigraphy, and furnish a formal category that permits many surficial deposits to be treated as legitimate stratigraphic entities while allowing the full use of geomorphic criteria.