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Kansas River Valley

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Geomorphic Development

Pre-Kansan Time

Little evidence of a pre-Pleistocene surface remains in Kansas River valley. Chert and limestone gravels in a clay matrix high on the divide areas are the only known deposits of possible Tertiary. or Nebraskan age. Topographic position, stratigraphic succession, and absence of glacial material were the criteria used in classifying the gravels.

The gravels are exposed in the divide areas about 125 to 150 feet above the present bedrock floor of the valley; they were deposited by streams in Tertiary or early Pleistocene time. Chert gravels are exposed in a pit in the NW NE sec. 31, T. 10 S., R. 14 E., in, a road ditch in the SE SE sec. 26, T. 10 S., R. 13 E., in the SE SW sec. 29, T. 10 S., R. 12 E., and in the NE sec. 5, T. 10 S., R. 10 E. (Pl. 1). They also are exposed in a pit in the SE SW sec.. 7, T. 10 S., R. 13 E., and in the NE sec. 5, T. 10 S., R. 12 E., but the exposures are too small to map. Till overlies the chert gravels in nearly all these exposures. The gravels are not extensive, enough to permit reconstruction of a pre-Kansan surface.

Kansan Stage

The advance of the Kansan glacial ice front into this area from a center in Canada was the principal event of Kansan time. The present Kansas River had its beginning during this glacial advance (Lohman and Frye, 1940) and was an ice-marginal river.

Considerable erosion must have taken place prior to the invasion by the ice. The bedrock surface on which pro-Kansan sediments were deposited is 50 to 75 feet below the surface underlying the pre-Kansan gravels. Pro-Kansan sands and gravels occur locally below the Kansas Till in this section of the valley. Because of the proximity of this area to the glacial margin, the bedrock surface probably was not scoured by the glacier. Test holes shown on the north end of the cross sections (Pl. 3) penetrated 5 feet (10-14-32bb) to 26 feet (10-14-32cc) of sand and gravel beneath the till. The pro-Kansan gravels were deposited on a bedrock surface 15 to 25 feet above the present Newman Terrace surface.

The ice front continued to advance and extended beyond the present valley as indicated by the presence of pro-Kansan gravels in the valleys of some of the larger tributaries south of Kansas River, and the overriding of the pro-Kansan gravels by the ice covered them with thin sheets of till. Kansas River and many of its tributaries were dammed by the ice during its maximum advance in Kansan time. Ice damming caused accumulation of meltwater from the ice and also of water from the west, forming many lakes in the area. A concentration' of gravel and till along Turkey Creek valley in Wabaunsee County indicates that Turkey Creek was a major tributary to Kansas River in early Kansan time. Turkey Creek may have been the main tributary to Kansas River and the outlet from Mill Creek into Kansas River, but the width of the present Mill Creek valley and the high bedrock divide between+Turkey Creek and Mill Creek are evidence against this hypothesis.

Smyth (1898) and Todd (1911) recognized the evidence of a Kaw Lake, which drained to the south along the glacial ice margin into Mill Creek, thence into Mission Creek through Dry Creek south of Maple Hill, and into the headwaters of Shunganunga Creek. This drainage approximately paralleled the till deposits south of the river. The largest concentration of till boulders is southeast of Wamego in Wabaunsee County. The till is very thin on the south side of the river; most of the finer material has been removed by erosion, leaving the concentration of boulders.

The thickest till is north of the river. Cuttings from test holes indicate that the till mantle may be as much as 84 feet thick northwest of Silver Lake. The till is composed principally of clay interbedded with sand and gravel but containing sparse large boulders.

Kansas River valley was filled with glacial outwash as the glacier retreated. The Menoken Terrace deposits are the remnants of these deposits. The Menoken Terrace is about 60 feet above the Newman Terrace. Menoken Terrace deposits contain considerably more fragments of granitic and metamorphic rock than do the pre-Kansan gravels. The distinctive lithology of some of the pebbles indicates that they were derived from sources in the Rocky Mountains and deposited by streams flowing across the Great Plains, the Flint Hills divide having been breached during Kansan time. As the glacier retreated, progressively finer grained material was deposited. The silt and clay in the upper part of the Menoken Terrace deposits may be in part eolian in origin, but they are so deeply weathered that they cannot be distinguished as such. During the subsequent Yarmouthian Stage, soil formation was the principal geologic process (Frye, 1951).

Illinoian Stage

Erosion was renewed near the beginning of Illinoian time after a long period of geologic stability. The Kansas Till and outwash were deeply dissected and in places removed by Kansas River and its tributaries. No deposits directly associated with ice of the Illinoian Stage are present in Kansas River valley. The bedrock surface on which Illinoian sediments were deposited is 25 to 50 feet below the surface on which Kansan sediments were deposited (Pl. 3, Fig. 4).

In the waning phase of Illinoian time, Kansas River and its main tributaries were heavily laden with sediment, and the valley again was alluviated to a level about 30 feet above the Newman Terrace. The remnants of these deposits are the Buck Creek Terrace deposits. The Buck Creek Terrace is prominent on the west side of the junction of Mill Creek and Kansas River, in Cross Creek valley, and on the south side of Kansas River south of Belvue and Wamego. Many of the smaller tributary valleys were choked by sediments of local origin. The upper part of the fill is reddish-brown silt and clay upon which the Sangamon soil developed.

Some of the finer material in the upper part of the Buck Creek Terrace deposits may be of eolian origin. The extensive cover of Loveland loess northeast of Rossville and Silver Lake was derived from Soldier Creek to the northeast. Loess derived from Kansas River valley is very thin on the upland south of the river.

After Illinoian glaciation, Kansas River valley again was stable geologically, and the Sangamon soil developed during the Sangamonian intervaL The profile of this soil generally exhibits a thick A zone, a moderately thick B zone, and a thoroughly oxidized C zone.

Paleontological evidence for dating the Illinoian deposits is very meager, but the physical criteria are almost conclusive. Fossil mollusks reported from similar deposits in other parts of Kansas River valley are comparable to the Illinoian fauna of Leonard (1951).

Wisconsinan and Recent Stages

During the early Wisconsinan Stage, the alluvium forming the Newman Terrace deposits was laid down in Kansas River valley, and eolian loess was distributed on the upland. During the late Wisconsinan Stage, renewed entrenchment of Kansas River formed the Newman Terrace.

The surface of the Newman Terrace, which may be as much as 15 feet above the Hood plain, is undissected except by minor gullying at the scarp. The nearly Hat surface resulted from vertical accretion more than from lateral point-bar accretion. The bedrock surface on which the Newman Terrace deposits accumulated lies 50 to 80 feet below the terrace surface (Pl. 3). Deposits on the surface of the Newman Terrace are predominantly silt and silty clay.

During early Wisconsinan time the wind transported fine silt and clay from the Hood plain of Kansas River to the upland. This loess is classed as the Peoria Formation; it differs from the Illinoian loess of the Loveland Formation in color and in degree of soil development. The Peoria Formation is light gray to gray tan and is less clayey than the Loveland Formation. Also, the degree of oxidation is greater in the Loveland Formation than in the Peoria Formation.

In parts of Kansas Valley the early Wisconsinan deposits have been eroded and late Wisconsinan and Recent sediments deposited (Pl. 3) as the Hood plain of modern Kansas River. The Hood plain is extensively scarred by old meanders of Kansas River, and in places minor terraces or pseudoterraces have formed by point-bar accretion. Soils on older parts of the Hood plain have a weakly developed profile, whereas the younger parts have little or no soil. Deposits on the surface of the Hood plain are predominantly fine sand and sandy silt, but some meander scars have clayey fillings. The channel of Kansas River is cut into the Hood plain, and the normal water level of the stream is about 8 to 10 feet below the top of the channel.

Sand dunes are active in several localities in the valley, but only one area is extensive enough to map. Sand dunes generally are associated with recent channel changes; the wind moves sand before vegetation can become established to protect the unconsolidated material from deflation.

Small alluvial fans have been deposited along the north bluff of Kansas River valley by intermittent tributary streams. Reduction in gradient of these streams as they emerge on the Newman Terrace results in deposition of a part of the stream load.

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Kansas Geological Survey, Geology
Placed on web June 16, 2014; originally published March 1959.
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