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Revised Stratigraphic Interpretation and Implications for Pre-Graneros Paleogeography from Test-Hole Drilling in Central Kansas

by P. Allen Macfarlane, Alan Wade, and John H. Doveton
Kansas Geological Survey
Lawrence, Kansas
and
V.J. Hamilton
Shell Western Exploration and Production
Houston, Texas
Kansas Geological Survey Open-file Report 91-1A

Abstract

Core and borehole geophysical logging data were obtained from test-hole drilling during FY90 by the Kansas Geological Survey to assist in the definition of hydrostratigraphic units of the Dakota aquifer in central Kansas. Combined with the results from earlier test-hole drilling, these data are used to revise earlier outcrop-based interpretations of the stratigraphy and depositional environments of the Dakota Formation, Kiowa Formation, and Cheyenne Sandstone in central Kansas. These revisions have provided new information on Albian-Cenomanian paleogeography, a key element in the prediction of sandstone body trend and distribution and thus hydraulic continuity. The Cheyenne-Kiowa sequence records the advance of the Kiowa sea into the central Kansas area during the Albian and suggests that the character of sediments deposited on the eroded Permian surface was controlled by their position in the early Cretaceous landscape. Fluvial channel, overbank, and estuarine deposits filled paleovalleys and finer grained marine muds were deposited over them and over the inundated instream areas. The distribution of the resulting marine black shales at the base of the Kiowa in central Kansas shows that much of central Kansas was an upland area before inundation. In one test hole a progradational sequence of subaerial and subaqueous tidally influenced deltaic strata indicates a constructional phase of development during Longford time. Subaerial exposure may also indicate that the rate of sea-level rise slowed or stagnated in central Kansas during this time. The test hole in Washington County demonstrates that the Longford Member, Kiowa Formation, extends to at least the Kansas-Nebraska state line. The maximum extent of the Kiowa transgression is unknown because of truncation of younger Kiowa strata by the J unconformity, an erosional surface with over 100 ft (3 m) of local relief. The J unconformity formed after the retreat of the Kiowa sea and subaerial erosion of the upper part of the Kiowa during the late Albian. During Dakota time (late Albian-early Cenomanian), the J and D sequences record two periods of sea-level rise separated by a period of erosion. Westward-flowing streams became aggradational and filled paleovalleys with fluvial channel sandstones and fine-grained flood-plain sediments during each period of sea-level rise. Central Kansas was probably not inundated during the transgression associated with deposition of the J sequence. The primary effect of the subsequent fall of sea level that created the D unconformity was rejuvenation and entrenchment of the existing paleodrainage system in that area. The aggradational phase at the top of the Dakota culminated in the deposition of lobes of river-dominated deltaic sediments during eastward landward stepping by the Graneros sea in the central Kansas area. The Dakota-Graneros formational boundary, where not transitional, is locally abrupt as a result of deltaic lobe switching and erosion associated with transgression of the Graneros sea.

Recent coring and geophysical logging of test holes penetrating pre-Graneros Cretaceous strata in north-central Kansas were undertaken to assist ongoing research directed at updating our understanding of the stratigraphy of these units. These strata were deposited in environments that shifted laterally great distances in relatively short intervals of geologic time because of the low depositional slopes of the ramplike eastern margin of the Western Interior seaway (Hamilton, 1989). The results of this response to transgression and regression are sedimentary rocks deposited over wide areas that are of similar lithologies but of different age. Traditional description of these strata as lithostratigraphic formations, complicated by a sparsity of outcrops, the complex mosaic of lithofacies exhibited vertically and laterally, and the lack of stratigraphic markers has promoted correlation of strata of different age. The work reported here is directed toward developing a more consistent stratigraphic framework for these units. This research effort is being conducted as part of the Kansas Geological Survey's research program to evaluate the long-term water resources potential of the Dakota aquifer in Kansas.

The Dakota aquifer consists of strata from the Dakota Formation, Kiowa Formation and Cheyenne Sandstone. An integral part of the Dakota aquifer program is the definition of hydrostratigraphic units within this aquifer. A hydrostratigraphic unit is defined as a formation, portion of a formation, or group of formation that possess similar hydrologic properties and that can be grouped into aquifers, aquitards, or aquicludes (Maxey, 1964). Hydrostratigraphic units are used to understand regional ground-water flow patterns, which are an important constraint on the quantity and quality of ground water available to wells. Discussion is not limited here to the three formations that make up the Dakota aquifer but also includes the Graneros Shale, which is, in part, laterally equivalent to the uppermost part of the Dakota Formation.

Our purpose is to present and interpret the data collected from three test holes that were drilled by the Kansas Geological Survey in FY90 in Lincoln, Republic, and Washington counties and to include a stratigraphic interpretation of each core. Detailed descriptions of each core can be found in Appendix 1, Appendix 2, and Appendix 3. This FY90 data and other test-hole data from earlier test-hole drilling of the Haberer, Braun #1, and #1 Brungardt test holes, Russell and Ellis counties, are used to describe the stratigraphy of the units that make up the Dakota aquifer and to make comparisons between the subsurface sections. These earlier test holes are discussed by Macfarlane et al. (1990), Hamilton (1989), and Macfarlane and Hamilton (1990). Comparisons are also made with surface sections reported by Hamilton (1989) and others. Appendix 4 contains the geophysical logging data from the Braun #1 and #1 Brungardt test holes. Appendix 5 contains a description of the Haberer core.

Last, from these comparisons we make inferences concerning the paleogeography of Kansas at the time that these units were being deposited. Paleogeographic reconstruction is important because the major fluvial and deltaic systems controlled the deposition of sandstones, which are the principal water-producing porous media in the Dakota aquifer (Leblanc, 1972). Information on the location of stream valleys and delta systems at the time of deposition is a key element in the prediction of sandstone body trend and distribution and thus of hydraulic continuity. Locally, the more permeable aquifer units consist of sandstones that were deposited in stream valleys and in deltas. River and delta distributary channel sandstones differ hydrostratigraphically from other types of deltaic sandstones in their sandstone body geometry and in their permeability (Weber, 1982). River and delta distributary channel sandstones tend to be highly permeable, discontinuous, and ribbonlike in contrast to deltaic sands, which tend to be less permeable, continuous, and sheetlike. These sandstone aquifer units are embedded in finer grained shaly sediments, which are much less permeable and act as an aquitard.

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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
URL=http://www.kgs.ku.edu/Dakota/vol3/ofr91_1a/index.htm