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Riley and Geary County Geology

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Stratigraphy, continued

Permian System

Paleozoic strata above the base of the Indian Cave sandstone, which is locally present in the lower part of the Towle shale, are classified by the Kansas Geological Survey as constituting the Permian system. Moore and Moss (1933, p. 100) have discovered a local disconformity below the Indian Cave member, and that, as they have pointed out, seems to be a logical boundary for the separation of the Pennsylvanian from the Permian. A comprehensive discussion of the Pennsylvanian-Permian boundary in the midcontinent region and other parts of North America has been published recently by Moore (1940). According to Moore and Moss the disconformity has been recognized at Indian Cave and Peru, Neb., and at Dover and Cedarvale, Kan. I have recognized the disconformity in northeastern Riley County, where the Indian Cave sandstone overlies various upper Pennsylvanian beds, the lowest of which is the Dover limestone. In one exposure the Indian Cave overlies the Brownville (?) limestone, and in another, a limestone that has been tentatively classified as Jim Creek limestone. In most of the very small area of outcrop of the Indian Cave sandstone, the base is concealed by Pleistocene and Recent alluvium.

The base of the Indian Cave sandstone and hence the base of the Permian System is shown on the areal geologic map of the counties.

Wolfcampian Series

The Kansas Geological Survey has adopted the term Wolfcampian as the name of the lowest series in the Permian system, in accordance with the recently established standard classification of the Permian section of North America. (Adams, J. E., 1939, pp. 1673-1681.) This supplants the term Big Blue, which has heretofore been used as the name of the lowermost series in the Permian system in the northern midcontinent area. The "Big Blue" series included some higher beds, which now are assigned to the Leonardian Series above the Wolfcampian. In Kansas the Wolfcampian Series is divided into Admire, Council Grove, and Chase groups. Although in Kansas no evidence has been discovered of a disconformity corresponding to the disconformity at the top of the Wolfcamp series in the Glass Mountains in Texas, the boundary between the Wolfcamp and Leonard series in Kansas is drawn at the top of the Nolans formation.

Admire Group

The boundaries of this unit have been changed several times by different geologists, but now the Kansas Geological Survey applies the name, as it was first used by Adams (Adams, Girty, and White, 1903, p. 53), to strata between the base of the Towle shale formation and the top of the Hamlin shale formation. The name Admire is obtained from the village of Admire, in Lyon County, Kansas. Included formations, in ascending order, are: Towle shale, Aspinwall limestone, Hawxby shale, Falls City limestone, West Branch shale, Five Point limestone, and Hamlin shale.

Towle-Hawxby Shale

The Towle shale was named by Moore and Condra (1932). The type exposure is the Towle farm near Falls City, Neb. The Towle shale is divided into the Indian Cave sandstone member in the lower part, and an overlying unnamed shale member.

The formation reaches the surface and is partly exposed along each side of the lower part of Deep Creek valley in southeastern Riley County, but throughout most of its extent it is hidden below a cover of sod and its position is shown only by the sandy residual soil derived from the Indian Cave member. The Indian Cave member is partly exposed in a few places and well exposed near the middle of sec. 30, T. 10 S., R. 9 E., where part of the overlying unnamed shale also is exposed.

Indian Cave Sandstone Member

The Indian Cave sandstone member was named by Moore and Moss (1933, p. 100), from exposures near Indian Cave, Neb. They discovered its disconformable relationship with underlying Pennsylvanian beds, and recognized the sandstone as the filling in a series of channels that had cut downward as low as the Dover limestone. I have seen the Indian Cave member as far south as Cedarvale, Kan.

In northeastern Riley County the base of the member rests upon the Brownville(?) limestone, the lower part of the French Creek(?) shale, and the Dover limestone at exposures only a few miles apart in the anticline in Deep Creek valley. It is very probable that this represents the approximate maximum erosion in the Kansas area at the close of Pennsylvanian time in Kansas.

Lithologic Character and Thickness--Where best exposed, in sec. 30, T. 10 S., R. 9 E., the Indian Cave member is found to be composed of very fine quartz and mica sand cemented with iron oxide. but it is probable that unweathered samples would contain calcareous cement. The somewhat weathered outcrop includes firmly and very poorly cemented zones. The quartz grains are extremely angular and range from approximately 0.025 mm. to 0.175 mm. in size. The mica flakes are larger and make up about 0.25 of 1 percent of the whole. The quartz grains are deeply stained with iron oxide. Near the top of the member there are many limonite concretions. Some interbedded layers of sandy shale contain much very fine carbonaceous matter interspersed with mica flakes. The thickness of the member at this exposure is approximately 75 feet.

Distribution--The base of the Indian Cave sandstone member is mapped as the base of the Permian system on the areal geology map. The member reaches the surface on each side of Deep Creek valley not far south of Kansas River near Zeandale.

Detailed sections--For detailed, measured sections in which the Indian Cave sandstone member occurs see numbers 51, 53, and 64 at the end of this report.

Undifferentiated Towle-Hawxby Beds

According to the present usage of the Kansas Geological Survey, strata above the Indian Cave sandstone include: upper part of Towle shale formation, Aspinwall limestone formation, Hawxby shale formation, and Falls City limestone. Along the outcrop in Kansas and southern Nebraska, these beds below the base of the Falls City limestone formation have a total thickness of about 35 feet. The Aspinwall limestone, which is approximately 4 feet thick, lies about 15 feet above the top of the Indian Cave sandstone, where it is present.

In the area under discussion these beds are present, but are everywhere concealed in a soil- or grass-covered slope, the Aspinwall(?) limestone forming a bench and a line of limestone boulders along the hillsides. Locally a few feet of the shale is exposed but hardly well enough to warrant an attempt at description.

In sec. 30, T. 10 S., R. 9 E., the upper part of the Towle shale comprises 20 feet of limonitic clay shale, which is sandy in its lower part and grades into sandy shale in the upper part of the Indian Cave sandstone member. The Aspinwall(?) limestone is composed principally of fragments of fossil pelecypods and hence resembles the Falls City limestone, which lies approximately 30 feet higher. A thin coal seam in the Hawxby shale was observed here and at a few other places.

The Aspinwall limestone was named by Condra and Bengston (1915, p. 9) for the town of Aspinwall, Neb., and the overlying Hawxby shale was named by Moore and Condra (1932) from a farm near Nemaha, Neb.

Falls City limestone

Condra and Bengston (1915, p. 30) named the Falls City limestone from exposures near Falls City, Richardson county, Nebraska. The type exposure is 2.5 miles south and 1.5 miles west from the town.

The Falls City limestone forms a bold outcrop in a small area in eastern Riley County but when traced laterally it loses its outcrop-making characteristics and is believed to become thin or to grade into shaly beds within a short distance.

Lithologic Character and Thickness--The Falls City limestone in the small exposures in Riley County is brownish-gray and consists principally of shell fragments, which are not very firmly cemented. It is identified by its coquina-like, brecciated texture, to, which the term "oatmeal" rock is appropriate. The exact thickness is perhaps not determinable, but great blocks 3 feet thick, which commonly are 6 to 8 feet across, probably represent almost the entire thickness of the bed, but in sec. 36, T. 10 S., R. 8 E., a thin bed of limestone 10 feet below the main ledge is probably a part of the formation. Along hillsides the blocks are conspicuous and are generally found slumped down the slope below the bench formed by the layer in its true position. Such blocks and good exposure of the unit can be seen in sec. 25, T. 10 S., R. 8 E., and sec. 30, T. 10 S., R. 9 E. Farther southward the limestone becomes much thinner and in sec. 9, T. 11 S., R. 9 E., the Falls City formation is believed to be represented by only a few inches of coquina-like limestone.

In general the Falls City limestone contains many pelecypods, small bellerophontids, bryozoa, and Chonetes granulifer.

Distribution--As indicated in the preceding paragraphs, the Falls City limestone can be traced with a considerable degree of accuracy on each side of Deep Creek for a few miles, east and south of Zeandale in southeastern Riley County.

Detailed sections--For sections of the Falls City limestone see numbers 51 and 53 at the end of this report.

West Branch-Hamlin shale

In the area of this report there are almost no exposures of the strata lying between the Falls City limestone and the base of the Foraker limestone, i.e., the Americus limestone member. Because the exposures are poor, the entire interval was measured wherever possible and was found to range from 35 to 40 feet. In a few places several feet of strata below the Americus limestone was studied and was found to comprise yellow and gray shale containing a large amount of sand.

Table 2 in this report shows the subdivisions of this part of the section as they are known in other parts of Kansas. They are: (3) Hamlin shale formation, which comprises Oaks shale, Houchen Creek limestone, and Stein shale members; (2) Five Point limestone formation, and (1) West Branch shale formation.

Section--Section 51, at the end of this report, includes the West Branch-Hamlin shale.

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Kansas Geological Survey, Geology of Riley and Geary Counties
Web version Nov. 2000. Original publication date Dec. 1941.
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