Prev Page--Petrography || Next Page--Economic Geology
Structure
At their outcrop in Kansas, the post-Wolfcampian Permian rocks are nearly flat-lying, with regional dips of 10 to 15 feet per mile to the southwest. In the subsurface, the deposits thicken toward western Kansas, and are upturned at the Front Range and Wet Mountains in Colorado. Kay (1951, p. 24, pl. 9) refers to the areas in Colorado east and west of the Front Range, where the Permian and Pennsylvanian sediments are fairly thick, as zeugogeosynclines which grade into an autogeosyncline toward the Kansas line. Kay (1951, p. 107) defines a zeugogeosyncline as an intracratonal elliptical basin or trough which contains sediment from eroded complementing highlands within the craton. Autogeosynclines are similar, but without associated highlands.
The following description of the structural history of the Permian rocks in Kansas is condensed from Lee (1953). In Pennsylvanian and early Permian (Wolfcampian) time, thick deposits were laid down in the Ouachita basin, and the rocks in Kansas thicken toward the southeast. The Central Kansas uplift was also active during that time. By Leonardian time, however, there was no further change in the Central Kansas uplift, and the region tilted toward the Hugoton embayment of the Anadarko basin. The salt beds were deposited as a result of gentle downwarping, somewhat to the east of the Hugoton embayment.
Before Cretaceous time the Permian redbeds were all tilted up toward the northeast and eroded, producing a low angular unconformity at the Permian-Cretaceous contact.
Small pronounced dips are common in present exposures of the Leonardian and Guadalupian? rocks. Most of these local structures are attributed to collapse caused by solution of underlying evaporites.
Climate, Sedimentation, and Paleogeography
General Classification
The presence in the detrital fraction of the sandstones and siltstones of 10 to more than 30 percent feldspars (chiefly potassium feldspar and minor sodic plagioclase) indicates that these rocks are primarily related to Krynine's (1943) arkose series. If the mineral compositions of the detrital fraction of the sandstones and nonargillaceous siltstones are plotted on the sedimentary series diagram of Krynine (1948, p. 137), they all fall within the arkose field and the orthoquartzite field (Fig. 13). (Many of the clayey siltstones fall in the low-rank graywacke field. A probable reason for this will be described later.)
Figure 13--Mineral composition of detrital fraction of some Leonardian and Guadalupian? sandstones and siltstones. (t, Taloga; whus, upper shale member, Whitehorse; wheb, even-bedded member, Whitehorse; whrc, Relay Creek; whm, Marlow; dc, Dog Creek; fp, Flowerpot; ch, Cedar Hills; sp, Salt Plain.) Triangular diagram from Krynine (1948, p. 137).
Even those sandstones which are within the arkose area cannot be called arkoses. Krynine (1940, p. 50) has defined an arkose as a "highly feldspathic (30 per cent of feldspar or more) sediment derived from a granite and having the appearance of a granite." They are more properly called feldspafhic sandstones, which Krynine describes as sandstones moderately rich in feldspar and not similar to granite in appearance.
In general, the post-Wolfcampian Permian deposits of Kansas are genetically more closely related to the arkose series than to any other series. The task remains to pigeonhole these rocks more exactly within the tectonic scheme. Krynine (1943) subdivides arkoses into tectonic arkoses, typified by the Triassic redbeds of Connecticut, and residual arkoses, which are commonly weathered and have not moved far from their source. Normal tectonic arkoses, which are of necessity thick and associated with postgeosynclinal pronounced uplift and usually block faulting, are not to be expected on relatively stable continental platforms such as the Kansas area.
The Kansas deposits are obviously not residual on feldspathic igneous rock. On the other hand they are said (Maher, 195,91) to be correlated stratigraphically with quartzose sediments in Colorado which overlie true tectonic arkoses (Krynine, 1943). It is here proposed to refer to these Kansas blanket deposits as ab-arkosic in nature in the sense that they are "away from" tectonic arkose geographically, mineralogically, and texturally, but yet have their origin in the tectonic arkose framework. Such deposits are not necessarily post-tectonic, but they tend to be late tectonic.
The trend, then, from normal tectonic arkose to ab-arkose is in the direction of Krynine's first-cycle secondary orthoquartzite, as suggested in Figure 13.
Genetic Significance and Interpretation of Deposits
Color
A large proportion of the red shales, siltstones, and sandstones in the section all have the same reddish yellow-red hue (Munsell notation 2.5YR) and differ from each other only in value and chroma. The color of the average post-Wellington red Permian shale has a value of 4 and chroma of 4. The common red siltstones have a value of 5 and chroma of 6. The normal red sandstones have a value of 6 and chroma of 6. Although these colors seem rather brown in the color chart, the impression of redness is enhanced by a foreground of green grass and background of blue sky.
The value, which indicates degree of lightness, seems to be a function of the proportion of quartz and feldspar present in the sediment and not entirely coated. Thus sandstones show the highest value number. The causes for variations in the chroma notation (strength, or departure from neutral) are harder to interpret. Possibly the presence of large quantities of a neutral-colored clay mineral (illite) in the shales produces a chroma of 4 in the shales as opposed to 6 in the siltstones and sandstones. This is not probable, however, because the clay flakes are normally completely coated with opaque iron oxide.
The 2.5YR hue (reddish yellow-red) is attributed primarily, but not entirely, to the presence of hematite. The color of typical hematite streak (or fine powder) is about 7.5R3/4 or yellowish-red (Munsell Color Co., 1942). The pure hematite hue has less yellow in it than does that of the redbeds. The increment of yellow may be attributed to small quantities of hydrated ferric oxide or maghemite (γFE2O3) which are not detectable by the x-ray diffraction techniques used. Furthermore, according to Van Houten (1948, p. 2098), hematite having a low degree of agglomeration and small crystal size may impart a yellow color to sands. The unimportance of coloration from chlorite seems to be due to iron oxide coatings on the smaller chlorite flakes. Thus purple color (owing to mixing of red from iron oxide and green from chlorite) is extremely rare.
The uniform orange-red color of the mid-continent Permian may be attributed to thorough redistribution of ferric oxide from complex colloids in contact with the highly alkaline Permian sea water at the same time that the authigenic layer lattice silicates (particularly chlorite) were being formed. Excess iron may have been expelled from the developing crystal lattice and hence thoroughly coated the surfaces of the flakes with iron oxide. Actual production of "new" hematite under conditions of high pH and high Eh helps to account for the remarkable uniformity of red coloration. Not all of the red hematite, however, was formed as such at the time of deposition; some of it was obviously transported into the basin of deposition as coatings on sand and silt grains, and some doubtless was associated with true detrital clay minerals. Some feldspars contain red iron oxide along cleavage planes.
Possible sources of the older iron oxide coatings are twofold: (1) in the upland primary source areas; and (2) in the more local regions of gentle warping and erosion of nearly contemporaneously deposited redbeds.
The extensive literature on the origin of redbeds and on the causes for their color has been carefully reviewed by Van Houten (1948), and a fourfold classification of redbeds has been made by Krynine (1949). Krynine's classification is herein summarized as follows.
- Redbeds produced from red soils (primary redbeds). Pigment developed by weathering of iron-bearing minerals at source area. Pigment incorporated into resulting sediment
- after erosion and transport (primary detrital redbeds);
- by local reworking of regolith (primary reworked redbeds);
- by lithification of regolith with little or no reworking (primary residual redbeds).
- Redbeds produced from nonred detritus by oxidation within the sediment.
- immediately after deposition (post-depositional redbeds);
- after burial, emergence, and deep subsurface oxidation (postdiagenetic redbeds).
- Redbeds produced by reworking of older redbeds (second cycle or secondary redbeds).
- Redbeds produced chemically by precipitation from solution within basin of sedimentation
- under marine conditions;
- under freshwater conditions;
- authigenically and intrastratally by infiltration.
The Permian redbeds of Kansas seem to belong in the first group: primary detrital redbeds. That is, they were produced from red soils, and their pigment was developed by weathering of iron-bearing minerals at the source areas, and incorporated into the resulting sediment after erosion and transport.
Other possibilities may be eliminated as follows. The deposits are obviously not primary residual or primary reworked redbeds, because there is no feldspathic regolith in the area. Field evidence from nonred areas within the redbeds indicates that their original color was red and that the iron was reduced shortly after deposition rather than being oxidized after deposition. Thus postdepositional and postdiagenetic redbeds are eliminated.
There is no evidence for extensive reworking of older redbeds to produce the Kansas Permian sediments. That a slight amount of such reworking may have taken place, however, is shown by occasional quartz and feldspar grains having red clay coatings which are covered by seemingly worn overgrowths. Such grains, however, are not common. Any significant reworking of older redbeds is considered to be the result of gentle warping which may have subjected only slightly older material to erosion. This does not involve more than one major cycle.
The Kansas redbeds are not considered to have been produced chemically by precipitation from solution, because such precipitation should have formed at least a few layers or lentils of comparatively pure iron oxide rather than just coatings on other grains. The proposed reorganization of the colloidal hydroxides and oxides at the site of deposition is a chemical process, but the hematite was not produced by precipitation from ionic solution, and the resulting redbeds are not related to the true chemical redbeds which form important ore deposits.
The primary detrital nature of the Kansas redbeds and their differences from primary detrital continental redbeds (as typified by the Triassic of Connecticut) will be discussed in the remainder of this section.
Significance of Evaporites and Salt Casts
The traditional textbook association of gypsum and halite with conditions of aridity is well known. Although the association of redbeds with aridity is no longer considered valid (Krynine, 1950), there is good reason for attributing the presence of evaporites to a dry climate. The only statement, however, that can be made with reasonable certainty concerning the climatic significance of Kansas evaporites is that they indicate an excess of evaporation over precipitation plus runoff from land areas. Arid conditions are therefore suggested but not proved.
The more important significance of the thin, wide-spread evaporites is twofold: (1) they indicate relative tectonic stability of the area with only gentle warping, and at least a partial barrier to the open sea1; (2) they suggest the chemical nature of the water in which the sediments were deposited. [1Note: In a recent paper Rutten (1954) postulates that the world's large salt deposits, such as the Zechstein, formed in inland basins fed by fresh-water springs and had no connection with the sea.] The presence of thin beds of chemically precipitated dolomite, anhydrite-gypsum, and salt, and the common salt casts (Pl. 14B) at many horizons throughout the redbed section shows that a high concentration of dissolved salts must have been available and important in modification of the deposits.
Absence of Fossils
The only fossils associated with the redbed section in Kansas (aside from two teeth and an unidentified bone in the Ninnescah shale) are the brine shrimp, Cyzicus (Pl. 22A). These animals, which are also common in the Wellington shale, are restricted to nonred bedding units. They are not found stratigraphically higher than the mid-Ninnescah shale. According to Zittel (1937, p. 734) this genus (Estheria) occurs mostly in brackish and shore deposits. Moore, Lalicker, and Fischer (1952, p. 544) state that the brine shrimp is able to live in excessively saline lakes and lagoons.
Plate 22--Sedimentary structures, Leonardian rocks. A, Cyzicus, Wellington shale; NW NW sec. 15, T. 24 S., R. 1 E., Harvey County. x1.3. B, Cross-bedding in buff-colored very fine-grained calcareous feldspathic sandstone, Ninnescah formation; W2 sec. 14, T. 35 S., R. 3 W., Sumner County. x1. [Note: web versions are enlarged to show more detail.]
Problematical worm borings are present in a few calcareous and dolomitic siltstones of the Ninnescah shale.
No vertebrate fossils or tracks have been observed in the post-Wellington redbeds of Kansas, and no plant remains are known. If animals and plants were present, their remains must have been completely destroyed by oxidation. Absence of tracks may possibly be ascribed to general nonterrestrial conditions of deposition. On the other hand, conditions of high salinity may have made most forms of life impossible.
The Verden channel sandstone in the lower part of the Whitehorse formation in northern Oklahoma contains a molluscan fauna which has been shown to be marine (Newell, 1940). Although there is no general agreement as to the origin of the Verden and similar channels, the marine character of the fauna is significant. One of the later studies of the Verden sandstone (Evans, 1949) suggests that the sand body was formed by salinity or tidal currents flowing through a strait or pass, connecting the restricted basin with the more open and fossiliferous Whitehorse sea to the south.
Tomlinson (1916, p. 172) notes that in general the distribution of gray and green colors in the redbeds of western United States coincides closely with distribution of organic remains in so far as such remains are present. He believes that organic remains now obliterated explain at least the greater part of the remaining gray and green areas. He (p. 169) attributes the green spots, which are so common in the red sandstones and shales, to the former presence of minute specks of organic matter (such as vegetable fiber or minute organisms of any kind), which reduced the ferric iron in their immediate vicinity. He notes the actual presence of such organic specks in green-spotted redbeds elsewhere. The remarkably evenly spaced distribution of the green spots in some of the Kansas redbeds suggests that the reducing agent responsible for them may in some way have been organic colloids present in the water which brought in the other colloidal sediments.
Some of the green spots are obviously associated with carbonates. Plate 23B shows extreme development of such spots in the Ninnescah shale (specimen from E. line W2 sec. 14, T. 35 S., R. 3 W., Sumner County). In this particular specimen many of the spots are hollow and are lined with calcite crystals. The association of calcite with decaying organic matter has been described recently by Weeks (1953) who attributes it to an inrease in pH caused by evolution of ammonia as the organic matter begins to decompose. The association of brownish specks of organic matter with certain thin carbonate layers, as in the Dog Creek shale, may perhaps be ascribed to the same process.
Plate 23--Sedimentary structures, Leonardian rocks. A, Ripple marks and mud cracks in light greenish-gray dolomitic feldspathic siltstone, Ninnescah shale, Bed 2; NE sec. 4, T. 27 S., R. 4 W., Sedgwick County. x0.3. B, Extreme development of green spots in red Ninnescah shale; W2 sec. 14, T. 35 S., R. 3 W., Sumner County. x1.1. [Note: web versions are enlarged to show more detail.]
The only other features noted by me which are suggestive of the former presence of organic matter are rare particles of pyrite (some of them associated with glauconite) in certain white sandstones, such as that in the Relay Creek? dolomite and sandstone member of the Whitehorse sandstone.
Ripples, Rain Prints, Mud Cracks, Cross Bedding
Ripple marks and mud cracks are common at many horizons in the redbed section. Some distinctive beds of calcareous or dolomitic siltstone which can be traced over distances of many miles are characterized by oscillation ripples on their upper surfaces. A slab from one such bed, which also displays mud cracks, is shown in Plate 23A.
Ripples and mud cracks are of course characteristic of shallow-water deposition. The presence of mud cracks, suggests, but does not prove, temporary emergence. These features are most common in the lower part of the section (Ninnescah through Salt Plain) and in the Dog Creek shale, but are also present in other formations. Problematical rain prints are observed in only one locality, in gray Wellington shale. Rain prints are more characteristic of actual terrestrial deposits than of subaqueous deposits.
Cross bedding and oolites, which are common, are other characteristic features of shallow-water deposition. Some of the cross bedding, particularly in the Whitehorse sandstone, is rather large scale, and some is microscopic. No eolian cross bedding is observed. Plate 22B shows moderately small-scale cross bedding in a very fine-grained calcareous feldspathic sandstone from the Ninnescah shale. The compass direction of the cross bedding is variable.
Mineralogy
Certain features of the mineralogy have particular genetic significance in the interpretation of the deposits. These features have been described in the section on petrography and will be only summarized here.
Condition of Feldspars
The presence in the feldspars of all stages of weathering (within a single specimen) suggests an erosional history similar to that of Krynine's tectonic arkoses; that is, rapid erosion in V-shaped canyons under humid tropical conditions. The preservation of the feldspars under conditions of long transport is probably in part a function of their relatively small particle size, and in part a function of the chemical composition of the water in which they were transported and deposited. The direction was in the production of overgrowths rather than in the destruction of the mineral.
Coarse (Detrital) Micas
The presence of chlorite flakes in large quantities is not typical of arkosic material derived from granite rocks. Most of these flakes are judged to have been altered from biotite by the magnesium-bearing water in which they were deposited. Various stages of alteration from biotite to chlorite are observed. Some chlorite could have been derived from schists intruded by granitic stocks, as in Connecticut, or from metamorphosed sediments of the Ouachita region.
The well-rounded character of the micas (chiefly muscovite) in the Salt Plain formation is worthy of note. Krynine (1950, p. 83) describes similar muscovite flakes having almost perfectly rounded coinlike shapes from lacustrine beds of the Triassic of Connecticut and also from Pleistocene glacial lake deposits of Connecticut. Wear of the mica flakes by gentle bottom currents rather than by fluviatile currents is thus indicated. This picture agrees well with the evidence from the size-sorting data from the Salt Plain samples which indicate much reworking of the material.
Clay Minerals
Little or no kaolinite is observed in the redbeds, and there is no evidence for gibbsite. Although these minerals should have been contributed from humid tropical source areas, they were probably completely altered after deposition. The large quantities of chlorite and illite seem to have developed authigenically within the sediments, and they were probably produced in part at the expense of kaolinite and gibbsite. Millot (1949) has shown that the clay minerals observed in a sediment are in large part a function of the cations present, and that kaolinite is not likely to grow in the presence of calcium ion. Magnesium ion, on the other hand, leads to the growth of chlorite minerals. Millot (1953) notes that illite and chlorite (but not kaolinite) are typical of the deposits of large supersaline lakes more or less linked with the sea. According to him, the mechanism of inheritance would appear inadequate to explain such a general phenomenon, and he considers it necessary to postulate the building up of the micaceous network in a basic milieu. Rivière (1953), on the other hand, believes that most clay minerals are transported and deposited without alteration. He writes that the lagoonal milieu of evaporation corresponds to a relatively dry climate in which the evolution of the soils of the watersheds scarcely passes the illitic stage. The presence of deeply weathered feldspars and the abundance of hematite, together with the paucity of unstable minerals in the Kansas Permian redbeds do not support Rivière's hypothesis.
The abundance of chlorite and illite, rather than kaolinite, is the factor which places the argillaceous siltstones in the low-rank graywacke field of Krynine's (1948) diagram (Fig. 10). This is seemingly a matter of diagenesis and therefore does not have the implied tectonic significance, except in so far as the Kansas area can be called part of a mild autogeosyncline.
Van Houten (1948, p. 2100) reports illite as the predominant clay mineral in various western redbeds, including the Chugwater, Spearfish, and Chinle formations, and does not find even subordinant kaolinite in these redbeds. In a study of clay minerals in sedimentary rocks and derived soils, Van Houten (1953) reported illite and some montmorillonite as the predominant clay mineral groups in Permian "Cimarron" (term discarded by Kansas Geological Survey) red sandstones and siltstones from Sumner, Harper, and Barber counties, Kansas. The fact that chlorite is not mentioned by Van Houten does not necessarily indicate that it is not present. The importance of chlorite in the fine fractions of sediments has only recently been recognized by clay mineralogists, and it is quite possible that this mineral was not recognized as such at the time the work was done. Preliminary treatment of Van Houten's (1953, p. 70) samples with HCl may also have destroyed any chlorite present. Van Houten (1953, pp. 72-73) suspected the presence of a colloidal magnesium silicate mineral in two of his Kansas redbed sediments because he found high MgO content coupled with low CO2. He suggested indirectly that this colloid might be related to attapulgite or sepiolite.
The point to be stressed is that illite rather than kaolinite is the predominant clay mineral in the redbeds. This is in direct opposition to the observation of kaolinite and gibbsite in the Triassic of Connecticut by Krynine (1950). In my opinion this merely points out the environmental difference between terrestrial redbeds and those deposited under water in a broad saline basin.
The presence of large quantities of montmorillonite in the Whitehorse and Taloga formations may be related to volcanic activity in Mexico during Guadalupian? time. Bentonites are common in the Guadalupian rocks of west Texas. Adams and Frenzel (1950, p. 296) report that bentonite is common in the Grayburg (upper Guadalupian) formation, and they suggest that it is derived from a volcanic area in Mexico. Adams and Frenzel (1950, p. 304) also state that bentonite "was probably widely distributed over the southern Permian Basin, but it is seldom recognized in the anhydrite and salt sections."
Present-day soils developed on the Kansas redbeds have approximately the same clay mineralogy as do the redbeds themselves (Van Houten, 1953). During the interval between the close of Permian deposition and the beginning of Cretaceous deposition in the area, however, kaolinite developed in the now-buried zone of alteration formed on the Permian redbeds.
Texture
The fine particle size of most of the grains in the Kansas redbeds suggests low energy levels of transportation, an only moderate supply of clastics, and great distance from source areas. The large rounded quartz and chert grains which are scattered among the finer sediments in the upper part of the section obviously had a different source or sources and are believed to have been derived from isolated mountain uplifts to the south within the basin; their coarseness increases markedly into Oklahoma. The large quartz and chert grains are typical of second-cycle orthoquartzites, and they seem to have been derived from erosion of Cambro-Ordovician rocks. Adams and Frenzel (1950, pp. 299, 304) describe similar large quartz grains from the upper Guadalupian Yates, Seven Rivers, and Queen formations of the Capitan barrier reef area, Texas and New Mexico. According to Adams (personal communication), soattered rounded quartz grains are present in the upper Permian rocks throughout the Permian basin. Honess (1923, p. 59) describes similar well-rounded, strained quartz grains from Ordovician sandstones of the Ouachita mountains of Oklahoma. The Ouachita complex may have been the chief source of these large grains and may also have provided much detrital chlorite to the redbeds.
Sedimentary Processes, Source Areas, Diastrophic Background, and Landscapes
By way of summarizing the conclusions drawn from a petrographic study of the Permian redbeds of Kansas, it may be enlightening to compare, point by point, the general characteristics of the Kansas redbeds with the Triassic redbeds of Connecticut as described by Krynine (1950). The comparison is shown in Table 8.
Table 8--Comparison of post-Wellington Permian of Kansas with Triassic of Connecticut
| Feature | Triassic of Connecticut* | Post-Wellington Permian of Kansas |
|---|---|---|
| Sedimentary series |
Tectonic arkose | Tectonic arkose, plus second-cycle orthoquartzite |
| External morphology |
Prism | Thin blankets |
| Distance from source |
Adjacent | Several hundred miles |
| Thickness | More than 15,000 feet | About 2,000 feet |
| Lithologic types |
Coarse arkosic sandstones and conglomerates; siltstones, red and black shales, very subordinate ilmestones | Very fine feldspathic sandstones, siltstones, and shales (chiefly red); many thin, persistent dolomites, limestones, gypsum beds |
| End members |
Coarse-grained arkosic detritus | Fine-grained feldspathic sand and silt (chiefly red) |
| Fine-grained detrital clayey matrix (red or black) | Clayey matrix, largely authigenic, chiefly red | |
| Carbonate cement (chiefly calcite) | Carbonates and sulfates (chiefly dolomite and gypsum) Salt in subsurface |
|
| Types of deposits |
Channel, lacustrine, floodplain; limited extent. Continental piedmont |
No obvious channels. Very extensive thin beds; some problematical floodplain. Chiefly restricted marine |
| Source of carbonates, etc. | Post-diagenetic circulating solutions due to structural activity Waters of lakes and swamps |
Water in which sediments were deposited |
| Accessory minerals |
Abundant and varied: up to 7.7 percent heavy minerals | Sparse; less than 1 percent heavy minerals |
| Evaporites | Infrequent casts of soluble salts | Abundant salt casts; dolomite, gypsum, anhydrite, and halite beds |
| Fossils | Wood throughout entire section; other plant remains common. Abundant reptilian tracks; fish in black shales | Brine shrimp in lower part of section. No tracks reported in Kansas |
| Clay minerals |
Kaolinite, gibbsite, sericite-illite | Illite, chlorite, some montmorillonite |
| Distribution of iron oxide |
Variegated. Grain coatings, and also concretions similar to those of soils (indicating subaerial weathering); 52 percent red rocks | Uniformly distributed as coatings, except where re-duced; 87 percent red rocks |
| Desiccation marks and other structures | Mud cracks, rain prints, tracks; very common | Mud cracks common in some parts of section. Ripple marks and noneolian cross bedding common. No post-Wellington rain prints observed |
| Climate | Hot and humid at source and probably also at site of deposition | Hot and humid at source; probably dry at site of deposition |
| *Krynine, 1950. | ||
The general picture of the area in post-Wolfcampian Permian time is one of a broad, shallow, fairly stable basin, bounded on the west by the Front Range and Wet Mountains, which supplied most of the feldspathic debris. The orogenic movement, which started to produce arkose in Pennsylvanian time and continued into the Permian, is not a typical post-geosynclinal orogenic stage but was more limited in extent and was probably characterized more by folding than by block faulting.
On the north and east the Permian basin was probably bounded by low-lying land areas which supplied little or no debris. To the south of the Anadarko basin was a restricted connection with the open sea, and several local uplifts which formed islands of mountain ranges, such as the Arbuckles, the Wichitas, and possibly intermediate mountains. Other possible land areas are the Ozark uplift and the Ouachita system.
It is thought that the source of the large rounded quartz and chert grains was in the Cambro-Ordovician orthoquartzitic sediments that underlay the entire area and were exposed to erosion locally in the isolated uplifted areas. Such a wide-spread source would account for the ubiquitous distribution of these grains.
Almost no clastics coarser than silts reached the Kansas outcrop area before Cedar Hills time, when numerous wide-spread very fine sandstones were deposited. Cedar Hills deposition was followed by another period of extremely fine elastic supply, and the Flowerpot shale was deposited in quiet water rich in calcium and sulfate ions. This episode culminated in deposition of widespread evaporite deposits (Blaine gypsum-anhydrite). An influx of fine feldspathic sand, perhaps both from the west and south, produced the Whitehorse formation. The supply of medium-grained clastic material gradually diminished during Whitehorse time, and montmorillonitic (bentonitic?) clays were deposited, as was also a thin persistent dolomite (Day Creek), The poorly sorted sands and silts of the Taloga formation suggest the incidence of slight instability and perhaps the deposition of poorly reworked flood-plain materials before the Permian seas withdrew entirely from the area.
Prev Page--Petrography || Next Page--Economic Geology
Kansas Geological Survey, Geology
Placed on web Aug. 25, 2006; originally published May. 1955.
Comments to webadmin@kgs.ku.edu
The URL for this page is http://www.kgs.ku.edu/Publications/Bulletins/111/06_struc.html