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Red Eagle Formation

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1. Rocks of the Red Eagle cyclothem can be traced through several facies changes from Bennet, Nebraska, to Burbank, Oklahoma. Most of the limestone in the northern Oklahoma Red Eagle type area is equivalent to the Bennett Shale Member of the Red Eagle Limestone formation in Kansas and Nebraska.

2. Rocks of the Red Eagle cyclothem accumulated in very shallow marine waters, upon an unusually flat shelf-basin. The floor of the basin was flattest at the end of Glenrock limestone deposition.

3. Red Eagle cyclothem rocks contain the following fundamental faunal-lithologic facies types, recognizable both in the field and in the laboratory: red shale facies, green shale facies, black shale facies, fusuline limestone facies, bioclastic limestone facies, conglomeratic-bioclastic limestone facies, shelly facies, algal limestone facies, osagite limestone facies, and aphanitic limestone facies. These facies types, as well as others first recognized and interpreted by Imbrie and others (1959) and by Laporte (1962), are represented in most cyclothems of the Kansas Wolfcampian.

4. Depositional environments of the various faunal-lithologic cyclothemic phases were controlled principally by water depth (see Table 7). Regional climate, which modified the supply rate of silicate clastics and the chemistry and movements of the sea water, significantly modified and sometimes subordinated the effects of depth.

5. Uniform depositional environments prevailed contemporaneously over wide areas of the shelf-basin during Red Eagle cyclothem deposition. The remarkably level basin floor permitted transmittal of even slight changes of depth, and attendant environmental conditions, across the entire shelf within very short (geologically instantaneous) time intervals. Such events caused knife-sharp lithologic boundaries such as the Glenrock-Bennett contact, which is essentially a time plane within the Red Eagle cyclothem. Slight depth changes sometimes gave rise to major changes in circulation and depositional conditions by barrier breaching.

6. The Red Eagle cyclothem records a cycle of water depth changes (summarized in Figure 5C) ranging from intertidal depths to not more than 60 feet. Tidal, wave-induced, and other currents were gently active within the shallow Red Eagle cyclothem waters, and they served to spread the sediments uniformly over broad areas.

7. Accumulation rates were broadly uniform during deposition of individual sedimentary units or phases of the Red Eagle cyclothem in Kansas and Nebraska.

8. The silicate clastic sediments in the Red Eagle cyclothem came from the north, east, and south of the present outcrop belt. Tectonism to the south (southeastern Oklahoma) periodically controlled the influx of clay clastics to the area. Changes of sea level (ultimate base level) and climatic changes also may have governed the supply of clastics.

9. Redbeds were deposited in the shallowest, most saline waters; they define the upper and lower boundaries of the cyclothem. Comparatively greater thickness of redbeds in Oklahoma indicates relative nearness to the southern source of red clastics. The red materials are believed to have been washed or blown into the area of study from red soil sources.

10. Regional climate during deposition of Red Eagle cyclothem sediments ranged from moist and cool (temperate), to warm and periodically dry.

11. Most of the limestone in the Red Eagle Limestone formation was formed from shell detritus and calcareous algal particles. Inorganically precipitated carbonates are negligible.

12. Formation of the Howe limestone osagite required clear, gently agitated water probably less than 10 feet deep, with current velocities greater than 10 centimeters per second.

13. Stratigraphic marker fossils within the Red Eagle cyclothem are:

Howe limestone Osagia
Bennett limestone Lophophyllidium?
(horn coral)
Bennett black shale Lingula, Orbiculoidea
(inarticulate brachiopods)
Glenrock limestone Triticites
(fusulinid foraminifer)
Upper Johnson shale Trochiliscus

14. Environmental index fossils within the Red Eagle cyclothem are:
Osagia: clear, shallow (0-10 feet), warm, gently agitated water.
Lingula, Orbiculoidea: shallow (0-10 feet), euxinic, somewhat turbid conditions; restricted circulation.
Triticites: clear, shallow (10-40+ feet), warm, normal marine water; gentle, free circulation.
Trochiliscus: shallow (0-10 feet), mildly brackish water rich in CaCO3

15. The gymnosperm? spores in the lower Bennett Shale resemble those of later Permian rocks elsewhere. In the Wolfcampian, mid-America may have been the cradle of development of a flora which did not reach other parts of the world until medial or later Permian time.

16. Faint crustal upwarps produced shoals in the Nemaha Anticline and Bourbon Arch areas of east-central Kansas, which exercised minor control over sedimentation in Glenrock and Bennett time but not during Howe time. Because of such upwarp, Glenrock Limestone is locally absent in east-central Kansas. A unique Glenrock facies near Manhattan, Kansas, may have been partly derived from upwarps near Alma, Kansas.

17. Chert and clear calcite pore fillings in Bennett limestone record diagenetic changes. The fine grain size of bioclastics, random particle orientation, light color, and lack of lamination in massive Bennett limestone are attributed to the activities of burrowing and mud-eating organisms.

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Kansas Geological Survey, Geology
Placed on web Jan. 4, 2007; originally published Dec. 1963.
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