USA > Iowa > Adair County > History of Adair County, Iowa, and its people, Volume I > Part 21
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The third exposure is at the west end of the dam at the Port Union mill. The section is as follows:
5. Black alluvium 10 feet
4. Yellow till, somewhat gravelly 5 feet
3. Hard, light buff limestone, varying to white or light gray, richly fossiliferous 2 feet
2. Very soft, homogeneous, blue-black shale, richly fossiliferous 4 feet
1. Hard, light-colored, fossiliferous limestone. 2 feet
Total 23 feet
Below the dam the stream flows over a rock bottom consisting of limestone No. 1 of the section just given. At high water No. 2 is covered. Strata Nos. 1 and 3 bear the following fossils:
Spirifer cameratus.
Productus (fragments) .
Crinoid stems in great abundance.
Rhombopora lepidodendroides.
Athyris subtilita. Fenestalla -sp.
Derbya crassa.
Myalina subquadrata.
Number 2 of this section (which will hereafter be spoken of as the "Port Union shale") bears the following:
Nucula (ventricosa [?]) .
Aviculapecten occidentalis.
Vol. 1-15
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HISTORY OF ADAIR COUNTY
Monotis (gregaria [?]) . Nuculana bellistriata. Unidentified gasteropods. Numerous molluscs.
A complete list of the Port Union fauna must be reserved for a future report. It is essentially molluscan in its character, and is char- acterized by the absence of Productids, Spirifers, and crinoid stems, all of which are present in the limestones both above and below, and by the absence of Chonetes verneuilanus, a fossil that is characteristic of the shales farther down the river.
Exposure No. 4 is on the south bank of the river, in section 21 of Harrison Township. Twenty-two feet of limestone are here exposed.
6. Kansan till, blue below, yellow at surface, slightly gravelly in places 5 feet
5. Light-colored massive limestone 1 foot
4. Fragmental limestone, fairly compact below, then with frequent partings of soft clay, finally shad- ing up into a soft purple clay in which but few hard limestone fragments occur 14 feet 6 inches
3. Hard, light-colored fossiliferous limestone 1 foot
2. Soft blue-black shale 2 feet 6 inches
1. Light buff limestone, fossiliferous, largely con- cealed by talus 3 feet
Total 27 feet
Stratum No. 1 of this exposure bears Athyris subtilita and frag- ments of an unidentified spirifer. The only fossil found in No. 2 is Chonetes verneuilanus, but the search was not long continued at this point. No molluscs were observed. In color and texture the shale is precisely similar to that found at Port Union. The limestone frag- ments of No. 4 are light in color, of variable hardness, and inclined to be angular. The clay is of about the consistency of the harder Kan- san till, or "hard-pan," breaks in the same way, checks on drying, and loses color on exposure to the weather. The original color is not the blue-black of the shale, but a blue-purple which approximates the color of the deeper Kansan drift. On leaching it passes through the various shades of purple-brown, dark brown, light brown and yellow- brown. It is non-fossiliferous, and contains no rock fragments other
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HISTORY OF ADAIR COUNTY
than the nodular masses of limestone already mentioned. It seldom shows distinct marks of stratification. Strata Nos. 4 and 5 are again exposed in a ravine which comes down parallel with the course of the Middle River and enters the latter a few rods below the exposure just described. The characteristics differ in no way from those already given, except that stratum 5 is two feet or more in thickness. On a small tributary in section 22 three feet of buff limestone is exposed, the underlying rock being hidden. In this exposure were found speci- mens of Productus nebrascensis.
The next exposure is in a narrow ravine on the Pemberton farm in section 27, Harrison Township. A second section is exposed some- what farther down the ravine, and the two in combination give the following:
10. Kansan till, with small boulders. 3 feet
9. Blue clay, similar to that found in stratum No. 4 of the fourth exposure 2 feet
8. Buff limestone 1 foot
7. Fragmental limestone, with much purple clay .. 6 feet 6 inches
6. Buff limestone 1 foot
5. Fragmental limestone 3 feet
4. Limestone, buff to dark brown. 2 feet
3. Hidden by sand, clay and boulders accumulated in stream bed 3 feet
2. Limestone, buff to dark brown 1 foot
1. Dark blue-black shale 2 feet
Total 24 feet 6 inches
Near the top of No. 9 is a band of very brittle black shale about half an inch in thickness. No. 10 is unconformable upon No. 9, the difference in color and texture being readily distinguishable at a dis- tance of twelve or fifteen feet. The Kansan here is leached to a light yellow, and bears a few pebbles and small boulders. The blue clay is non-fossiliferous. The blue shale (No. 1) contains specimens of Chonetes verneuilanus. This shale is almost black in color and similar in texture to that found at Port Union. Limestone No. 4 contains an abundance of Rhombopora lepidodendroides. Many crinoid stems are also present.
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HISTORY OF ADAIR COUNTY
In section 26 of Harrison Township the following exposure is found in the valley of a small brook putting into Middle River from the south:
11. Gravelly, dark-colored Kansan till 3 feet
10. Hard brown-buff limestone 8 inches
9. Purple clay, weathered brown to yellow 1 foot 6 inches
8. Black, laminated shale, very soft. 1 inch
7. Fragmental limestone, grading upward into clay. 10 feet
6. Buff limestone with two shale bands 5 feet
5. Fragmental limestone 5 feet
4. Very fossiliferous blue-black shale. 2 feet
3. Hard bluish limestone 5 feet
2. Very soft blue-black shale. 2 feet
1. Brittle black slate 6 inches
Total
34 feet 9 inches
Stratum 6 of this exposure contains quantities of Fusulina seca- licus. No. 10 is entirely non-fossiliferous. No. 3 contains Spirifer cameratus, Productus punctatus, P. costatus, P. longispinus, Derbya crassa, Rhombopora lepidodendroides, many crinoid stems and other fossils. No. 4 contains Chonetes verneuilanus. The last of the Mid- dle River exposures in Adair County is near the east line of section 36, Harrison Township . Several feet of blue-black shale occur capped by massive limestone.
On Bush's Branch, in section 13, Grand River Township, occurs the following exposure:
2. Alluvium . 3 feet
1. Soft black shale 5 feet
The black shale is extremely rich in specimens of Chonetes ver- neuilanus which, when the spot was last visited, had weathered out clean and formed a small talus at the foot of the bank. This is the last of the carboniferous exposures in Adair County. Near the old mill at the Village of Webster, in Madison County, something over a mile east of the exposure found in section 36 of Harrison Township, several feet of rusty-colored Fusulina limestone is exposed, but its relations to the beds above and below have not been traced by the writer. Probably this represents about the upper limit of the frag-
1
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HISTORY OF ADAIR COUNTY
mental limestones and their associated clays, shales and massive lime- stones, and the beginning of the Earlham and Winterset limestones. As the name would indicate, the latter occur near Winterset, together with the fragmental limestones. The relation between the three at that point has been described by Tilton in the report on the geology of Madison County, in the publications of the Iowa State Geological Survey.
Except for the anomalous Port Union shales and Keating breccia, the relations of the Missourian strata exposed in the eastern half of Adair County are quite clear. In Grove Township occur the Earlham limestones, resting on a foundation of fragmental limestone. (The clay and shale described by White evidently belong to the horizon of the fragmental, though he does not describe the actual fragmental materials. Their associated clays are characteristic.) How large a territory is covered by the Earlham in Adair County is impossible to say. Except at the points indicated it is completely masked by the Kansan drift sheet. All that we know with certainty is that east of Port Union it was eroded away previous to the deposition of the drift; the surface rock in all exposures from Port Union to the county line belonging to the fragmental limestone, and closely resembling the fragmental as described by Bain in Decatur County and by Tilton in Madison. The exposures of Earlham limestone at Earlham, Win- terset, Perry's Quarry and other localities, are probably isolated out- liers. In a region so completely covered by drift, the relations of the underlying indurated rocks cannot be worked out with anything like completeness.
In describing the type section of fragmental limestone at Beth- any, Mo., Bain ("Iowa Geological Survey," volume VIII) mentions that the lowermost portions of the deposit consist of a hard breccia. This may be identical with the breccia found on the Keating farm, but the elevation of the latter indicates that it corresponds with the upper and not the lower portion of the fragmental. If it is to be regarded as corresponding to the breccia as found at Bethany, the relations of the deposits in Adair County would suggest a north-and- south antieline whose axis would pass somewhere near Port Union. On the other hand, the Keating breccia may be younger than the Earlham, and may have been deposited after the erosion of the latter, in which case the angular fragments of which it consists are frag- ments of Earlham limestone weathered from the eroding surface and the cementing material belongs to some later formation. If the former view be adopted, one may well question the nature of the
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HISTORY OF ADAIR COUNTY
process that led at one point to the formation of a breccia (for such the fragmental limestone is) whose cementing material is a soft clay, while at the same time and only a mile or two away similar breccia was being formed with a hard calcareous cement. The Port Union shale. also, with its distinctive fauna, suggests an interval of time between its deposition and that of the other shales here described, which occur at about the same level. But the limited exposure both of the breccia and the Port Union shale forbids the solution of this problem at the present time.
The general dip of the Earlham limestone and the fragmental limestone in Adair County is toward the south. Middle River, cutting in a southeasterly direction through these southerly dipping strata, gives them an apparent dip to the southeast. The apparent southeast dip is of course less than the actual southerly dip. The former amounts to about ten feet to the mile, or about the same as the gradient of the bed of Middle River.
SECTIONS OF INDURATED ROCK WEST OF THE DIVIDE
The west half of the county is covered by a thick mantle of drift, and no streams cut to bedrock. Consequently the only obtainable evidence as to the nature of the indurated rocks is to be obtained from deep borings, and the number of the latter records which have been preserved is all too small. The results indicate that the surface of the Missourian is at places covered by a veneer of Cretaceous sand- stone belonging to the Dakota stage. The following shafts have been investigated :
On the farm of J. A. Hulbert, in Washington Township, 41/2 miles southeast of Bridgewater, rock was encountered at a depth of 275 feet. After penetrating through twelve feet of soft sandstone, further drilling was abandoned.
At the residence of J. G. Hendry, one mile south of Bridgewater, a well was sunk some fifteen years ago, and the record, carefully preserved by Mr. Hendry, reads as follows:
Blue clay 65 feet
White clay 40 feet
Gravel 1 foot
Dark, soft sandstone 12 feet
Hard clay, dark in color 2 feet Sandstone 18 feet
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HISTORY OF ADAIR COUNTY
Slate 2 feet
Coal 22 inches
Limestone .18 feet
Quicksand and water
Total 158 feet 22 inches
The gravel occurring just below the white clay is described as con- sisting of pebbles which were much water worn and very hard, and of rather uniform size. The white clay was of such a character as to color the water milky when it was first drawn from the well. Both it and the blue clay above contained few pebbles. Eighty feet lower down the hillside and half a mile or less from the site of the first well another shaft was put down with the following result:
Blue clay 177 feet
Red clay with many pebbles 3 feet
Blue-black carboniferous shale 40 feet
Total 220 feet
The black shale contained two or three narrow bands of coal, but was otherwise homogeneous in its nature and of a smooth, even con- sistency. The "red clay with many pebbles" is probably a phase of the Dakota sandstone. In the first section the line of separation between the Missourian and the Dakotan is the two feet of black slate lying immediately above the stratum of coal.
On the farm of E. Stacey, one mile northwest of Bridgewater, in the digging of a well shaft a forest bed was struck at a depth of forty feet. After taking out a section of a good-sized log, probably of cedar, digging was resumed. Ten feet lower the auger entered black shale. The water was dark in color and had a bad taste. No indica- tion of the presence of cretaceous materials appeared in this well, the drift lying in immediate contact with the Missourian shale.
On the farm of W. W. Witham, in Summerset Township, a short distance west of Greenfield, a well was sunk to a depth of 275 feet. At about two hundred forty feet the drill passed into limestone with bands of black and blue shale. No Dakotan gravels or sandstones were present. The Missourian limestone was covered by 240 feet of blue clay, with some small pebbles and boulders.
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HISTORY OF ADAIR COUNTY
A shaft sunk by the City of Greenfield for the purpose of securing a water supply for the municipal electric lighting plant passed through 208 feet of Kansan clay and thirteen feet of Missourian lime- stone and shale. No gravels were encountered. A few small peb- bles were found in the clay, and at one point a thin bed of sandy clay was encountered. As usual, the complete record was not preserved.
A shaft sunk on the farm of F. H. Seers, five miles north of Fon- tanelle, is reported as passing into soft sandstone at a depth of 260 feet. About twenty feet of the standstone was penetrated without noting any change in the nature of the materials.
On the farm of Henry Rose, two miles north of Bridgewater, Missourian limestone was struck at a depth of 270 feet, while a shaft on the farm of Al Bowers, a mile or two north of the Rose farm, passed into Dakota standstone at a depth of 260 feet. Forty feet of fine-grained sandstone is also reported from a well bored by William Turner near Adair.
The only record of Dakota sandstone east of the divide is given by Simpson in Norton's report on the underground waters of Iowa. This is a well bored on the Whittum farm in section 19 of Lincoln Township.
Enough has been said to indicate that the surface of the Missourian rock in Adair County is dotted with scattered outliers of Dakota sand- stone. Probably no part of the county is covered with a solid and continuous mass of cretaceous rock. The variation in the depth at which rock is encountered indicates two things: the depth of the ero- sion to which the Kansan drift has been subjected, and the depth of the erosion to which the underlying rocks were subjected before the coming of the ice sheet.
The abandoned Eureka coal shaft, six miles south of Adair, passes entirely through drift and Missourian rock. The shaft is now par- tially filled, and is not in condition for examination, but was described by Keyes ("Iowa Report," Volume II) as follows in the year 1894:
"The shaft is 262 feet in depth, the coal varying from 20 to 32 inches in thickness. The roof is bituminous shale. The bottom of the shaft shows:
Clay shale (exposed) 2 feet
Coal 2 feet
Fire clay 8 inches
Shale, dark (exposed) 1 foot 4 inches
Total 6 feet
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HISTORY OF ADAIR COUNTY
"The mine is worked on the long wall plan. There are a few unimportant clay seams, but no other breaks in the continuity of the bed. This is a new mine. The coal has been taken out only from about one hundred fifty to two hundred feet to the east and west of the bottom of the shaft. It is reported that there are two other seams below the one now worked, one at a depth of about forty-five feet and the other at a depth of about fifty-five feet from the bottom of the shaft."
In June, 1892, a correspondent of the Greenfield Transcript wrote as follows:
"The size of the shaft is 6 by 16 feet and is divided into three apartments. At the depth of over a hundred feet they found a cedar post. The dirt passed through was very hard and had to be dug with a pick. Thence through different kinds of clay and into soapstone. The caprock is four feet and nine inches thick. After passing that, came into two feet of black looking substance which contained coal blossom; passing on into slate, thence into a three-foot vein of good coal. The shaft is 228 feet deep, and the coal is deposited 268 feet from the top of the ground."
The evidence of a forest bed, in the shape of a cedar log, is signifi- cant. The soapstone is probably a smooth, homogeneous shale, such as is characteristic of the Missourian rocks of this part of the state. No cretaceous rocks appear at this point. The coal and associated strata here and in the shaft near Bridgewater are probably to be referred to the horizon of the Nodaway coal as described by Smith for the counties south and southwest of Adair, but the formation is so scanty that no definite correlation is yet possible. If this supposi- tion is correct, the Nodaway coal lies at a considerably greater depth below the Nodaway Valley in Adair County than in Page and Mont- gomery counties.
THE DRIFT SHEETS
The Nebraskan drift sheet probably underlies the Kansan drift in parts of Adair County, but it is impossible from existing evidence to say anything definite with regard to its extent. Probably, how- ever, the greater part of the Nebraskan material was eroded away by the advancing Kansan glacier and incorporated in the Kansan drift. The same may be said of the Aftonian gravels lying on top of the Nebraskan. The summits of the carboniferous hills were denuded of these materials by the advancing Kansan ice sheet, and they are
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HISTORY OF ADAIR COUNTY
found today only in those places where the carboniferous rock lies at a low level. There can be no doubt as to the identity of the Aftonian gravels when found; but it must be borne in mind that the Aftonian did not cover the entire surface of the Nebraskan, but was laid down in the beds of the numerous streams by which the Nebraskan drift plain was dissected during the gradual retreat of the ice sheet. Con- sequently there may be many places where the Kansan drift rests directly upon the Nebraskan. The only way to demonstrate such a relation between the two is to find them exposed in section and dem- onstrate the existence of an unconformity; and as the only evidence upon the subject is that obtained from the record of well shafts, such a demonstration is of course out of the question. Immediately above the Nebraskan and Aftonian comes the Kansan drift. Through the removal of the earlier deposits the Kansan frequently rests directly upon the bed rock. Whatever the underlying material, whether Aftonian gravels, Nebraskan drift, Dakota sandstone, or Missourian limestone, there is always of course absolute unconformity between it and the Kansan. The thickness of the Kansan, and the nature of the materials composing it, may best be indicated by the sections of a number of well shafts investigated by the writer:
1. On the Conway farm, west of Macksburg in Madison County, but not far from the Adair County line, a well shaft was dug which passed through fifty feet of alluvium and Kansan drift. For the most part the latter consisted of a stiff, blue clay, unstratified, and without boulders, though containing a few small pebbles. Below this a bed of sandy clay was struck in which was imbedded a log of hard wood, probably walnut, four feet in diameter.
2. On the same farm, at about the same depth, the auger entered the bed of rather soft, ill preserved peat. The peat seemed to consist principally of compacted grass and grass roots, and was roughly but not inaptly described by the well digger as a "fossil haystack." Above it lay a nodule of brown haematite the size of a goose egg.
3. On the farm of J. M. Wilson, in section 12, Union Township, a well was dug with the following result :
3. Black surface soil with much humus. 1 foot
2. Stiff joint clay, yellow near surface, blue beneath 49 feet
1. Black silt, with many small wood chips. 3 feet
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HISTORY OF ADAIR COUNTY
The yellow and blue clay was entirely unstratified, contained a very few pebbles and small boulders, and in places numerous lime concretions.
4. On what is known as the Ed Baker farm, northwest of Macks- burg. a well was dug, the auger passing through twenty feet of stiff joint clay, varying in color from yellow to blue-black. An impedi- ment was then encountered in the shape of a mass of twigs and sticks lying criss-cross and very slightly compacted. Associated with these were pebbles and bog-iron nodules. The larger sticks were as large as a man's arm, or larger, and were much broken and apparently gnawed at the ends, but not decayed.
5. On the Funk farm, northwest of Greenfield, section 2, Sum- merset Township, the well digger reports that at a depth of twenty- three feet he was obliged to chop through a willow log six inches in diameter.
6. Some years since the writer watched the boring of a well on lot 3, block 36, original Town of Greenfield. The auger passed through two feet of black surface soil, then entering yellow-brown joint clay, the upper three inches of which had a slightly reddish cast. It passed through fifty feet of stiff joint clay, varying in color from yellow-brown to dark blue-brown, absolutely unstratified, and con- taining no sand, gravel or boulders.
7. A second well on the same lot passed through thirty feet of stiff blue joint clay without pebbles, sand or boulders. The lower part of this was the so-called "stinking clay." The two wells were about a hundred yards apart.
8. In the northwest corner of section 7, Jefferson Township, a well was sunk to the depth of about thirty feet. The first twenty feet passed through fine-grained black sand with an admixture of barely enough clay to bind it somewhat. The auger then entered stiff blue Kansan clay. The sand is doubtless post-Kansan, and was laid down as part of the old flood plain of Middle River.
9. In digging a well on the Sears farm, in Jackson Township, a number of logs were encountered at a depth of thirty or forty feet. The overlying material is unstratified blue and yellow clay with many pebbles and small angular fragments of quartzite.
10. In a well on the farm of E. Stacey the auger penetrated to . the depth of forty feet through stiff blue clay. At that depth a section of a good sized log of some coniferous wood was removed from the shaft. After digging an additional ten feet through gravelly clay,
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HISTORY OF ADAIR COUNTY
black carboniferous shale was encountered. The water was reported unfit for use.
11. The city well at Greenfield is bored through 208 feet of stiff blue joint clay, very slightly sandy in places, unstratified, and con- taining a few small angular pebbles. This is four blocks distant from the Greenfield well already mentioned. The Kansan rests directly on Missourian limestone.
12. In the well on the Witham farm, already mentioned. the elay is reported as having a thickness of 240 feet and resting directly on Missourian limestone. The clay is blue, unstratified, showing typical joint structure, and containing a very few small angular pebbles and boulders.
13. In section 31, Jefferson Township, the writer watched the boring of a well some fifteen years ago. The well was sunk to the depth of about thirty-five feet, the material consisting of a stiff blue clay, unstratified, and without pebbles below the first four feet. very few being present there. The material from this well was piled near the shaft and left there permanently. In 1911 it was examined by the writer. The clay still showed the joint texture, but as a result of leaching it crumbled somewhat more readily than it had when first taken out, and the color had changed from dark blue to light brown- yellow. In fact, as last seen, it was precisely the same soil that many observers have mistakenly supposed to be loess, and that has occa- sionally been described as loess when reported from Southwestern Iowa. All that is necessary to the artificial manufacture of loess of this sort is that typical blue joint clay be dug up from the lower por- tion of the Kansan drift sheet and exposed to the action of the weather for several years. The surface soil in many parts of Adair County (i. e., wherever it is not covered by alluvium or blackened by plant humus) consists of this leached Kansan clay. Sometimes it contains pebbles or boulders, more frequently not. Rarely it is decid- edly gravelly. Lime concretions are not infrequent. The well just mentioned showed many of them.
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