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Kansas Geological Survey, Open-File Rept. 91-1a
Pre-Graneros Paleogeography--Page 3 of 16

Regional Sequence Stratigraphy

Pre-Graneros strata consisting of the Cheyenne Sandstone, Kiowa Formation, and Dakota Formation (Albian and early Cenomanian, approximately 94-108 m.y.) in age crop out in a northeast-soutwest band across central Kansas and in an east-west band across southern Kansas (Figure 1). To the north and west of the outcrop these units underlie younger Cretaceous strata.

Cheyenne Sandstone

In outcrop the Cheyenne Sandstone consists predominantly of light-colored fine- to medium-grained, friable crossbedded sandstone. Lenses of conglomerate and sandy to silty carbonaceous shale containing lignite and plant fossils are also common in the upper part of the formation (Latta, 1946). Exposures of the Cheyenne Sandstone occur only in southern Kansas in areas near the type section. In the central Kansas subsurface the Cheyenne is commonly described as a white fine- to medium-grained sandstone composed of subrounded, frosted quartz grains that are unconsolidated or cemented with pyrite or calcium carbonate (Swineford and Williams, 1945).

Kiowa Formation

The Kiowa Formation is exposed throughout most of the outcrop belt and is present in the subsurface. The Kiowa Formation rests unconformably on the Cheyenne Sandstone or on Permian units. The contact with the Permian is an angular unconformity with commonly 50-100 ft (15-30 m.), of relief, but the contact with the Cheyenne Sandstone is a transgressive disconformity. The lithologies of the Kiowa Formation include shale, thin sandstone, and fossiliferous limestone. Depositional environments of the Kiowa Formation have been interpreted as sublittoral to open marine (Scott, 1970), reflecting the variability in lithologies. Sandstones within the formation were deposited near the margin of the Kiowa sea as delta-front sands, barrier bars, offshore bars, and tidal current bars (Franks, 1966, 1975). The age of the formation is upper Albian. The Kiowa Formation is subdivided into an upper unnamed marine shale facies and a lower member, the Longford.

Franks (1966) separated white siltstones, lenticular sandstones and red-mottled siltstones and mudstones at the base of the Kiowa Formation into the Longford Member. Later he determined that the Longford Member rests with transgressive disconformity ont he Permian and is conformably overlain by and is laterally equivalent to the Kiowa Formation (Franks, 1980).

The Longford Member outcrops in a north-south-trending band at the base of the Kiowa Formation along the eastern edge of the outcrop belt in central Kansas (Franks, 1979). It is not present in southern Kansas outcrops but has been reported in the subsurface of Barton County (Latta, 1950). Franks (1980) interpreted the Longford Member as a variety of nonmarine and paralic deposits including fluvial, estuarine, lagoonal, and barrier bar sediments.

Dakota Formation

The Dakota Formation is defined as nonmarine and littoral clay and sandstone above the Kiowa Formation and below the Graneros Shale. The Dakota Formation is Albian to Cenomanian in age (Franks, 1975), and the upper part is restricted to the Cenomanian (Hattin, 1965; Franks, 1966). The lower two-thirds of the Dakota Formation consists of gray claystone and red-mottled massive claystone, siltstone, and sandstone. the fine-grained facies of this member were deposited in flood plains adjacent to streams (Franks, 1975). The upper part of the formation consists of lignite and dominantly kaolinitic gray to dark-gray massive claystone, siltstone, and some shale. From outcrop studies Franks (1966), Siemers (1971), and Hamilton (1989) interpreted the depositional environments to be predominantly transitional from nonmarine to marine up through the section. The lower section of the Graneros Shale to the west is laterally equivalent to the upper Dakota Formation of eastern and southern Kansas. The contact between the Dakota Formation and the underlying Kiowa Formation is disconformable. The contact with the overlying Graneros Shale is marked by a transgressive lag overlying a transgressive disconformity.

Regional Sequence Stratigraphy

Sequences divide the stratigraphic record into genetically related, time bounded stratigraphic units. By placing facies within this time-space framework, it is possible to determine how depositional environments shifted through space and time. Figure 2 shows the pre-Graneros unconformity-bounded sequences of Weimer (1984) that have been described in Kansas by Hamilton (1989).

Figure 2. Sequence stratigraphic framework of pre-Graneros Cretaceous strata in central Kansas.

Regional Geologic Structures

Figure 3 shows the extent of the major structural features in the vicinity of the test holes in central Kansas. The Braun #1, #1 Brungardt and Haberer test holes were drilled on the Central Kansas uplift. The KGS #1 Jones, the Kenyon #1, and the Gaydusek WII test holes were drilled in the Salina basin.

Figure 3. Major structural features in the central Kansas area.

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Kansas Geological Survey, Dakota Aquifer Program
Original report available from the Kansas Geological Survey.
Electronic version placed online Oct. 1998
Scientific comments to P. Allen Macfarlane
Web comments to webadmin@kgs.ku.edu