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Kansas Geological Survey, Open-File Rept. 91-1a
Pre-Graneros Paleogeography--Appendix 2

Appendix 2--Stratigraphy of the Gaydusek WII Core

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The Gaydusek WII test hole was drilled during November, 1989 in NW, SW, NW Sec. 10, T. 1 S., R. 2 E., Washington County, Kansas, on land owned by Frank Gaydusek. The test hole began in the lower part of the Greenhorn Limestone [upper 62 ft (19 m)] at the top and ended in the Permian Wellington Formation at a total depth of 534 ft (163 m). Figures 2.1 through 2.4 show the geophysical logging traces from the borehole. A detailed description of the core retreived and its interpretation is given in what follows.

Figure 2.1. Gamma-ray and caliper logs of KGS Gaydusek WII NW-SW-NW 10-1S-2E indexed with stratigraphic subdivisions.

Figure 2.2. Gamma-ray and lithodensity-neutron logs of KGS Gaydusek WII NW-SW-NW 10-1S-2E, Washington Co., Kansas.

Figure 2.3. Spectral gamma-ray logs of KGS Gaydusek WII NW-SW-NW 10-1S-2E, Washington Co., Kansas.

Figure 2.4. Gamma-ray and resistivity logs of KGS Gaydusek WII NW-SW-NW 10-1S-2E, Washington Co., Kansas.

62-90 ft (19-27 m) (Graneros Shale interval)

This interval consists of predominantly fossiliferous gray shale containing a moderate abundance of bivalves. Included in this interval is 8 ft (2.4 m) of interlaminated calcareous sandstone and slightly calcareous shale near the middle of the Graneros Shale with wavy and hummocky cross-laminations. Above this sandy zone the shale is slightly calcareous; below it the shale is not calcareous. There are also several beds of bentonite; in particular, two beds one at 62 ft (19 m) and the other at 81 ft (25 m) can be recognized from the increased levels of activity on the gamma-ray log. The base of this interval is marked by a hard, calcite-cemented siltstone containing cone-in-cone structures.

This sequence was deposited in a generally quiet shallow sea below fair weather wave base but above storm wave base. The sandy, hummocky cross-laminated interval was deposited by storm action. The decrease in sand content and cross stratification and the increase in calcium carbonate content upward are due to decreasing influx of terrigenous material as the shoreline moved eastward from this site. As a result, the environment of deposition changed from shoreface to offshore marine with less restricted circulation patterns (Hattin, 1975).

90-100 ft (27-30.5 m) (Upper Dakota Formation)

This section of the core consists of interlaminated sandstone and mudstone with increasing sand content and calcite cement upward from the base. Near the top of this interval wood and shell fragments are both present.

This facies was deposited in the distal bar portion of a delta front. The combination of shell and wood fragments reflects the marginal marine setting of the depositional environment, with detritus derived from both marine and terrestrial sources.

100-112 ft (30.5-34.1 m)

This interval consists of fine-grained horizontal and ripple-laminated micaceous, glauconitic sandstone. It includes mud clasts near the scoured base. Mud drapes up to 0.1 ft (0.03 m) thick and carbon flecks occur throughout along with heavily pyritized wood fragments near the top.

The small-scale sedimentary structures, grain size, and organic content are typical of a distributary mouth bar (Coleman and Prior, 1988).

112-124 ft (34.1-37.8 m)

This part of the core consists primarily of dark-gray mudstone with occasional thin, parallel, wavy and lenticular very fine grained sand and silt laminations with a 2-ft-thick (0.6-m.-thick) bed of very fine grained sandstone that was not well recovered from the core. Occasional horizontal sand-filled burrows are present in this interval.

This interval is interpreted to have been deposited in the distal bar portion of a river dominated delta front. The mudstone was deposited from suspension with occasional current action, either tide or river related, being responsible for the sandy laminations and lenses.

124-157 ft (37.8-47.9 m)

The predominant lithology in this interval consists of a coarsening-upward sequence of horizontal and wavy laminated, very fine grained micaceous, generally poorly sorted sandstone interbedded with siltstone. Individual coarsening-upward sequences rich in plant fragments and several feet thick can be distinguished below 140 ft (42.7 m). Vertical and horizontal burrows are present below 150 ft (45.7 m) where the sequence lies conformably on top of the swamp deposits described earlier. Core recovery was poor in this interval, particularly above 137 ft (41.8 m).

This interval is interpreted an an interdistributary bay fill sequence consisting of splays from the local distributary. Bay fill deposits are characterized by an overall coarsening-upward sequence incorporating graded beds of laminated sand, silty sand, and silt, with burrowing more common lower in the sequence (Coleman and Prior, 1988). Subsidence or a rise in sea level resulted in submergence of the swamp deposits, creating space for sediment to accumulate beneath water level. Sea-level rise relative to the delta was sufficient to prevent the bay from filling up completely, in which case the sequence would have been capped with a lignite.

157-208 ft (47.9-63.4 m)

This interval is dominated by the red- (and minor green-) mottled gray mudstone with root marks. However, this grades up, above 186 ft (56.7 m), into structureless light-gray siltstone containing plant fragments, carbon flecks, and in situ roots. The organic content increases and the grain size decreases as this mudstone grades up into a waxy, black, organic mudstone at 157 ft (47.9 m) and is interbedded with rooted light-gray silty sandstone.

This part of the core was deposited on a flood plain under conditions that changed from oxidizing to reducing throughout the interval. Near the top of this section the sediments were being deposited in a marshy flood basin under reducing conditions which promoted the preservation of plant material and in which the black organic mudstone was deposited. Deposition of this mudstone in a marsh was interrupted by a splay of silty, very fine grained sandstone introduced by a flood event from a nearby river.

208-218 ft (63.4-66.4 m)

This part of the core consists of laminated, very fine grained sandstone and siltstone with ripple marks, scour and fill structures, slumping, sandstone dikes, inclined laminations, and general soft sediment deformation. This facies is interpreted as a levee deposit capping a channel fill sequence.

218-235 ft (66.4-71.6 m)

In this section the core consists of poorly indurated, trough crossbedded fine grained sandstone with occasional mud drapes grading up through rippled, fine-grained sandstone into laminated, sandy siltstone. This section is interpreted as a channel fill sequence. Upward changes in sedimentary structures and grain size reflect the change from high to low flow regime conditions.

235-272 ft (71.6-82.9 m)

The predominant lithology in this section consists of poorly indurated sandstone that fines upward from medium-grained sand to silty, very fine grained sand. Carbon flakes and fragments are common throughout this interval. Core recovery was poor in this section. However, large-scale crossbedding is visible in the few pieces of medium-grained sandstone recovered from the lower half of this interval. Parallel, ripple, and wavy laminations and soft sediment deformation are common in the fine-grained, very fine grained and silty sandstone near the top of this interval.

This fining-upward sequence is a classic river channel fill with high flow regimes reflected in the lower channel fill sediments (relatively coarse grain size and large-scale crossbedding) and lower flow conditions dominating higher up (very fine grain size with small-scale bedforms).

272-340 ft (82.9-104 m)

This interval is dominated by gray mudstone with red mottles and no sedimentary structures but also includes some laminated, very fine grained sandstone. Many of the mottles in the mudstone are root and rootlet shaped, that is, branching vertical tubes and fibers,which is a remnant of the plant bioturbation that removed all sedimentary structures from this facies.

This facies is interpreted as an overbank flood-plain sediment. It accumulated only during flooding of a nearby river and was thoroughly reworked by plant roots in between these flooding events. Beds of finely laminated, very fine grained sandstone within the mottled mudstone were deposited closer to the sediment source (i.e., the river) in a levee environment.

340-349 ft (104-106 m)

The strata in this section consist of light-gray poorly indurated, very fine to fine-grained sandstone with some wavy laminations. Core recovery was poor in this interval. The strata in this interval are interpreted to have been deposited in a levee adjacent to a river channel.

349-378 ft (106-115 m)

There is an overall coarsening upward of the strata in this interval. The lower 10 ft (2.8 m) consists of clean medium-gray, slickensided mudstone with occasional silty lenses and carbon flecks. Poorly sorted, gray, micaceous, sandy siltstone with abundant plant fragments and carbon flecks are present above. No sedimentary structures were observed in this interval.

This interval is interpreted as the fill of an abandoned river channel. The lack of red mottles and very fine grain size of the mudstone is indicative of a sheltered, reducing environment that may have been below the water table. The upward increase in grain size is due to closer proximity to a sediment source, such as an active river channel. The poor sorting of this coarser sediment shows it was dumped in a relatively quiet environment as a result of a sudden significant drop in current velocities, which is consistent with an abandoned channel.

378-400 ft (115-122 m)

The lithology in this interval is dominated by very poorly indurated, crossbedded, medium-grained sandstone containing rip-up clasts of siltstone and occasional plant fragments and carbon flecks. Embedded within the sandstone are large blocks up to 4 ft (1.2 m) thick of relatively well-lithified distal bar sediments consisting mainly of silty mudstone with thin, very fine grained sand laminations but also including a bed of ripple laminated fine-grained sandstone with abundant intraclasts [see description above of the interval 400-431 ft (122-131 m)].

The laminations within the distal bar sediments are inclined at an angle of 50(-60(. They could not have been deposited on a stable surface at such an angle. This high angle shows that the blocks of distal bar sediments suffered rotational slumping after lithification. Thus the base of the medium-grained sandstone is an unconformity representing a significant period of erosion. The crossbedding and relatively coarse grain size is evidence of a high flow regime typical of an active river channel. This interval was therefore deposited in a river channel cut into the underlying lithified sediments, large blocks of which collapsed into the channel and were preserved. The disconformity marks the boundary between the Dakota and Kiowa Formations.

The uppermost foot of this interval consists of conglomerate beds up to 0.5 ft (0.2 m) thick interbedded with clean gray mudstone beds 0.1-0.2 ft thick (0.03-0.06 m. thick). The conglomerate contains clasts of white, gray, and red mudstone and siltstone up to 0.5 in. (1.3 cm) across. This represents large variations in current intensity resulting from partial abandonment of the river channel. The intraclasts are probably reworked overbank sediments from a nearby cutbank.

400-431 ft (122-131 m) (Longford Member, Kiowa Formation)

Two main facies are interbedded with each other: (1) a yellow, micaceous, rippled, fine-grained sandstone facies in beds from 0.1 ft-3 ft thick (0.03-0.09 m. thick) and (2) a laminated, very fine grained sandstone and silty mudstone that makes up most of the interval. The rippled sandstone facies contains occasional to abundant plant fragments up to at least 0.2 ft (0.06 m) in length and carbon flecks. Ripples are unidirectional current ripples. This facies commonly contains small intraclasts (medium to very coarse sand size) of gray silty mudstone. Most beds of this facies have sharp tops and bases, but some of the beds grade down into silty mudstone. The interlaminated silty mudstone and very fine grained sandstone facies contain laminations of sandstone that are subhorizontal, thin, wispy, and sometimes lenticular. There is little evidence of bioturbation except for some horizontal traces at 415 ft (126 m).

This interval is interpreted as having been deposited in the distal bar portion of a river-dominated delta front. The finer grained facies was mainly deposited from suspension with occasional current action, probably tidal or river related, being responsible for the sandy laminations and lenses. The fine-grained sandstone beds were deposited by longer lasting and greater currents. The moderately high organic content and small-scale crossbedding is good evidence of current action associated with floods in a nearby distributary touching bottom, each bed of fine sandstone representing an individual flood which even brought in the yellow sand and organic material and locally ripped up clasts of silty mudstone (Coleman and Prior, 1988).

431-443 ft (131-135 m)

In this interval beds of conglomerate 0.1-3 ft thick (0.03-0.09 m. thick) are interbedded with laminated gray siltstone and silty mudstone and underlain by a poorly indurated, sugary, medium-grained sandstone, most of which was not recovered in core. The conglomerate consists of angular to subangular clasts of white, gray, and pale red siltstone or silty mudstone and gray fine-grained sandstone and plant fragments supported in a matrix of fine to medium sand with carbon flecks. There are no graded beds, and there is no evidence of imbrication. Boundaries between the beds are sharp with no gradation. The gray siltstone contains occasional thin laminations of very fine grained sand that are lenticular in places. The interlamninated siltstone and sandstone is draped directly over the uneven tops of the intraclastic conglomerates.

The poor sorting and lack of structures in the conglomerate beds are indicative of plastic flow, that is a debris flow. These debris flows may have been triggered by fracturing and subsidence of the underlying Permian sediments as a result of evaporite dissolution during transgression of the early Cretaceous sea. The gray siltstone was deposited mainly from suspension in between debris flow events. It represents the generally quiet water conditions of a lower shoreface or distal bar environment when sedimentation rates were much slower than during the debris flows. Laminations and lenses of sandstone are evidence of current action, which was probably tidal.

443-534 ft (135-163 m) (Wellington Formation)

This part of the core consists of finely interlaminated, silty, very fine grained calcite-cemented sand and silty mud. The laminations are generally flat and parallel, although some wavy laminations are present, indicating current or wave processes. This facies is well indurated but heavily brecciated. The core contains pieces of broken rock from fractions of an inch to several inches across. Broken laminations are common. This brecciated facies overlies a hard bluish-gray, burrowed silty shale. The contact is an irregular surface inclined at 70° to the horizontal, that is a fault plane.

These sediments are interpreted as shallow marine deposits of the Permian Wellington Formation. Much of the Wellington Formation typically consists of evaporites, although they were not observed in this core. The brecciation may be due to dissolution of evaporites by ground water that penetrated the Permian surface. Debris flow deposits within the overlying Cretaceous sediments may be related to this subsidence in the Permian deposits.

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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
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