McDonough County, Illinois - Chapter with an unread heading (no. 9 of those read), 1878

Geological

AVe make no apology for copying bodily from the report of Hon. A. H. Worthen, State Geologist, bis remarks with reference to the geology of this county. To scholars this chapter will be especially valuable.

The geological formations appearing at the surface in this county comprise the Quaternary, including the loess and drift ; the lower portions of the coal measure, including the three lowest seams of coal ; and the St. Louis and Keokuk divisions of the Lower Carboniferous limestones.

The entire area ot this county, except the valleys of the streams, is covered with beds of Quaternary age, ranging from thirty to a hundred feet or more in thickness, and presenting the same general features that have been given as characteristics of this formation in the reports on the adjoining counties. Good natural exposures of these are but rarely found here, and the observer is compelled to rely mainly on such information as can be obtained from the well diggers, or others engaged in surface excavations, as to their thickness and general character. In the railroad cut on the north bank of Crooked creek, just below Colmar, the following section of Quaternary beds was seen :

This exposure is considerably below the general level of the prairie, and the beds seem to have been subjected to some shiftingprocess since its original deposition, giving to it the general characteristics of "modified drift." In the shafts of Colchester the drift clays generally range from thirty-five to forty feet in thick- ness, and consists of buff or brown clays, with gravel and boulders, passing downward at some points into blue clays, or "hard pan." Boulders of metamorphic rocks, of various kinds, and of all sizes up to a diameter of two or three feet, are scattered in considerable numbers in all the gulches and streams that cut through the drift beds, and are most abundant in the lower part of the drift deposits. Ko indi'jation of the presence ot an ancient soil underneath either the loess or drift was seen at any of the points visited in this county ; nor did we learn that it had been observed by any one else. The wells are seldom sunk to the bottom of the drift, and hence afford no indications of what may underlie the boulder clays. At Bushnell a boring for coal passed through 112 feet of these Quaternary deposits before reaching the bed rocks, in the following order :

This is probably twice as much as the average thickness of the deposits in this county - the drill having evidently penetrated an old valley, where from sixty to seventy feet of Coal Measure strata had been removed by erosion, and the valley thus formed subsequently filled with the transported material. The average thickness of the drift deposits probably does not exceed fifty feet.

Coal Measures. - All the uplands in the county are underlaid by the Coal Measures except a limited area on Crooked creek, in the southwestern corner of the county, embracing nearly the whole of township 4 north, range 4 west, (Lamoine) and the south-western portion of township 5 north, range 4 west, (Tennessee). The beds composing the lower portions of the Coal Measures, as they are developed in this county, give the followiug sections :

These beds have a maximum thickness of about 150 feet, and consequently a boring anywhere in the county, carried down to a depth of two hundred feet from the surface, would pass entirely through the coal measures, and determine the amount of coal that could be found at that point. Xo coal seam is worked at the present time, except No. 2, or the Colchester coal; and it seemed to us quite probable that neither 1 nor 3 is developed in the county so as to be of any value to the industrial interests of its people. In the vicinity of Colchester the limestone and calcareous shale usually found above coal ISo. 3 out-crops in the brakes of the ravines west of the town, but no indications of the presence of coal was seen. The concretionary or lenticular masses of dark blue limestone were found quite abundant here, and they afforded Cardiomorpha, Missouriensis in great numbers, associated with Discina nitida, Productus muricatus, P. Prattenianus, Pleurotomaria sphaerulata, Aviculopecten rectalaterarea, two or three species of small Goniatites, fossil wood, and the spine of a fish Listracanchus hystrix. We also obtained from one of these limestone concretions, associated with the fossil wood above mentioned, a fossil fruit, shaped somewhat like an elongated pecan nut, the relations of which have not yet been determined. These limestone concretions have been found in Fulton and Schuyler counties overlaying coal ISTo. 3, and affording most of the species of fossil shells obtained from it here; so that there seems scarcely a doubt but that it here represents the horizon of that coal. It is quite probable that in the eastern, and especially in the southeastern portion of the county, coal No. 3 may be found sufficiently developed to be worked to advantage. The shale and sandstone above this coal, Xo. 1 of the foregoing section, we only saw in the vicinity of Colchester, where about ten feet in thickness of sandy, ferruginous shales overlay the limestone concretion above mentioned. Xo. 4 of the foregoing section is well exposed on the ravines leading into the east fork of Crooked Creek, west of Colchester, but it is everywhere a sandy shale, with some thin layers of sandstone, but affords no material of any economical value. The calcareous shale associated with the limestone in Xo. 2 of the above section is, at some points near Colchester, quite full of small fossil shells, among which the Spirifer plano-convexus was the most abundant, associated with S. lineatus, Chonetes mesoloba, Productus muricatus, Pleurotomaria, Grayvillensis, a small Macrochcilus, and fragments of a Xautilus.

No. 5 of the above section torms the roof of the Colchester coal, and is a true clay shale at the bottom, and locally quite bituminous, becoming sandy higher up, and gradually passes into the sandy shales of ISTo. 4. It contains ironstone concretions similar to those at Mazou creek and Murphysboro, though usually not so perfectly formed, and they contain fossil ferns of the same species found at those localities. The shales also are filled with beautiful ferns, in a remarkably fine state of preservation; and this locality may be reckoned as one among the best in the State for collecting these beautiful relics of an ancient vegetable world. Two specimens of fossil insects and two or three species of shells have been found associated with the fossil ferns at this locality. The following list comprises all the species of fossil plants that have been identified at Colchester to the present time : I^europteris hirsuta, 'N. tenuifolia, N. rarinervis, Alethopteris aquilina, Callipteris Sullivantii, Pecopteris squamosa, P. villosa, P. unita, P. plumosa, P. chrerophylloides, Sphenopteris irregularis, S. trifoliata, Hymenophyllites alatus, H. Spinosus, H. splendens, H. Gutbierianus, H. thallyformis, Cordaites borassifolia, C. angustifolia, Spenophyllum Schlotheimii, S. emarginatum, S. cornutum, Annularia longifolia, A. sphenophylloides, Asterophyllites equisetiformus, Calamites ramosus, C. approximatus, C. undulatus, Selaginites uncinnatus, S. carifolius, Lepidodendron diplotegioides, L. simplex, L. obovatum, L. gracile, Ulodendron majus, U. ellipticum, Lepidophloios obcordatum, Lepidostrobus princeps, Lepidophyllum auriculatum, Sigillaria monostigma, Stigmaria ficoides, S. umbonata, Pinnularia capillacea, Caulopteris obtecta, C acantophora, Carpolithes multistriatus. Owing to the thinness of the coal, the roof shales are removed in driving the entries to the mines, thus affording a fine opportunity for collecting the many beautiful fossil plants that they contain. The thickness of the coal at this locality varies from twenty-four to thirty inches, and at the level of the prairie it lies from seventy-five to ninety feet below the surface. On all the branches west of Colchester the coal out-crops, and is worked by tunneling into the hillsides. The city of Quincy, as well as most of the small towns along the Chicago, Burlington and Quincy railroad south of Bushnell, have for many years derived their supplies of coal mainly from the Colchester mines.

In the vicinity of Macomb the Colchester coal seam has not yet been found of sufKcient thickness to be worked. About a mile and a half southwest of the town a thin coal out-crops above the sandstone quarries of Mr. Stewart, which I am inclined to regard as the Colchester seam, though it is here only about one foot in thickness. This may, however, be an out-crop of the lower seam number one, but from the appearance of the sandstone I believe it to be number two, thinned out here to about one-half its usual thickness.

In the vicinity of Colchester a very good sandstone is found below the coal, and from ten to fifteen feet in thickness. It is number eleven of the foregoing section. This I believe to be the equivalent of the sandstone at Stewart's, and the old McLean quarries near Macomb. A section of the beds exposed in the vicinity of these quarries show the following succession of strata :

The horizon of coal Xo. 1 is here occupied by Bituminous shales and a six inch band of carbonate of iron. In the vicinity of Colchester, at most of the out-crops we examined, the same horizon was represented by dark blue shades (Xo. 12 of the section previously given) containing nodules of iron ore inclosing crystals of zinc blende. On the southwest quarter of section 24, town 5 north, rangs 4 west, (Tennessee) the following beds were found exposed in connection with coal No. 1 :

Although we did not find this lower coal developed at any of the exposures examined in the vicinity of Colchester, yet it was found by Mr. Ilorrocks at his tile and fire-brick kiln, not more than a mile from the town, and was struck in one ot the pits sunk for fireclay. It was found to be about a foot in thickness only, and was associated with an excellent fire-clay, and was here about fortyfive feet below coal No. 2. Below Horrock's brick and tile kilns on the same stream a band of ferruginous sandstone, or rather a sandy iron ore, was found, about six inches in thickness, filled with fossil shells, among which a large Disciua was the most abundant, associated with Hemiprouites crenistria, Athjris subtilita, Spirifer opimus, S. Kentuckensis, and some other undetermined species. This was no doubt a local deposit, and probably represents the band of iron ore occurring in Schuyler and Fulton counties, associated with coal Xo. 1. Tliis band of iron ore occurs just at the junction of beds numbered 13 and 14 of the general section of the coal-bearing strata, on a preceding page.

On section 24, town 5 north, range 4 west [Tennessee], southwest quarter of the section, a coal seam was opened as early as 1853, when we first visited this county, on land then owned by Mr. Lowry. The coal was from eighteen inches to two feet in thickness, overlaid by a few feet of shaly sandstone. Below the bed of coal there was about sixteen feet of sandstone exposed, and a short distance up the creek the concretionary limestone is exposed, underlying the sandstone. This I have no doubt is the lower coal (Xo. l),and it will no doubt be found at many points in the county ranging from one to three feet in thickness.

At this time coal was also dug on Mr. Thompson's place, on the northeast quarter of section 16, town 4 north, range 3 west [Bethel]. The seam at this point was thirty inches thick, butwas only exposed in the bed of the creek, with no out-crop of the associated beds. This is also, without doubt, the lower seam, as the concretionary member of the St. Louis limestone was found outcropping on the creek a short distance below where the coal was found. On the northwest quarter of section 33, town 4 north, range 3 west [Bethel], a coal seam was opened and worked in 1858 on land then owned by Mr. J. Stoneking. The coal was worked by "stripping" in the bed of a small creek, and the coal ranged from eighteen to twenty inches in thickness, and was overaid by about two feet of gray shale.

These two lower seams also out-crop on Job's creek, near Blaudinsville, and have been worked from the first settlement of the count}'. They out-crop also on nearly all the tributaries on the east fork of Crooked creek, and probably underlie at least seven-eighths of the entire area of the county. They seldom attain a thickness of three feet, however, in this portion of the State, but thev are nowhere more than one hundred to one hundred and seventy-five feet below the surface of the general level of the prairie. Xo. 3, if developed anywhere in the county, will prob- H - 10

The beds numbered 1 to 5 inclusive belong to the drift, and show an aggregate thickness of one hundred and twelve feet, indicating the existence of an old valley here, in which the Coal Measures have been cut away down to a point below the horizon of the Colchester coal, and which was subsequently filled with drift deposits, and consequently that coal which should have been found at a depth of fifty to seventy feet below the surface at this point, was not met with at all. The limestone ISTo. 10 of the above sections is probably the bed overlaying the Seaville coal. The extent and direction of this old valley we have no data for determining at the present time, but it is probably a lateral arm of the Spoon river valley, and most probably trends southeastwardly into the valley of that stream. At Prairie City a boring was carried down to the depth of 222 feet, passing through the following beds, as reported by Mr. T. L. Magee :

In the foreo-oino: sections the beds numbered from 2 to 18 inclusive belong to the Coal Measures, and include the two lower -coals. 1^0. 19 is undoubtedly the St. Louis limestone which outcrops on Spoon river just below Seaville, about eight miles east ot Prairie City. At Lawrence's mound, at an elevation considerably above the surface where the above boring was made, a coal seam three feet in thickness was found in digging a well, which was probably No. 3, occurring here as an outlier left by tlie denuding forces which swept it away from the surrounding region. It lay immediately below the drift, with no roof but gravel, and covered but a limited area of ground.

At Macomb, a boring, carried to the depth of about IGO feet, failed to find any coal of sufficient thickness to be of any economical value. From these experiments, it would seem that the lower coals in this county are not very uniform in their development, and probably neither ISTo. 1 nor lN"o. 3 will be found over any considerable area thick enough to be worked to advantage, while Xo. 2 is also too thin to be worked at some points, though it may be considered the most persistent and reliable seam to be found in this county.

St. Louis Limestone. - This division of the Lower Carboniferous series is probably nowhere in this county more than fifty feet in thickness, and consists, first, of a bed of light-gray concretionary or brecciated limestone, laying immediately below the lower sandstone of the Coal Measures ; and secondly, of a magnesian limestone and some blue shales or calcareous sandstones, constituting what is sometimes called the " Warsaw limestone. " On the east fork of Crooked creek, a little north of west from Colchester, the following sections of these limestones may be seen :

The magnesian bed, which usually forms the base of this group, is below the surface here and generally ranges from eight to ten feet in thickness. The brecciated limestone is very unevenly developed, and often varies in thickness in a short distance from five to twenty feet or more. It rarely affords any fossils except the common corals Lithostrotion, canadcnse and L. proliferum, silicious specimens of which are often found weathered out along the creeks where this limestone out-crops. Ko fossils were seen in the calcareous sandstone, but the magnesian lime- stone that out-crops lower down on the creek, and underlies the blue shale in the above section, usually contains a variety of Bryozoans, among which are the Archimides AVortheni, Polypora Varsoeiense, Semicosciuium, Keyserlingi, etc.

Keokuk Limestone - This is the lowest rock exposed in the county, and is only found along the bluffs of Crooked creek, in townships- 4 and 5 range 4 west (Lamoin and Tennessee). The upper part of this iormation is usually a bluish calcareo argillaceous shale, containing silicious geodes either filled with a mass of crystaline quartz, or hollow and lined within quartz crystals, mammillary chalcedony, calcite and dolomite. Below this geode bed there isusually from thirty to torty feet of cherty gray limestone, the layers varying in thickness from a few inches to two feet or more^ and separated by partings of shale. The limestone beds consist mainly of the remains of organic beings, the corals, the crinoids, and moUusca that swarmed in countless numbers in the primeval ocean; and the old quarries of limestone afford a rich field for the student wbo desires to become fully acquainted with the varied and pecviliar organic forms of this period. South of Colmar the grade of the C, B. & Q. railroad cuts into the upper part of this limestone to the depth of several feet, and from the material thrown out from this cut we obtained many specimens of the characteristic fossils of this limestone in an excellent state of preservation. The upper layers of the limestone had been freely exposed to the erosive action of the water during the drift period, and many of the silicious fossils were found completely weathered out from the shaly limestones, and in a most perfect state of preservation. Among the fossils found at this locality were many specimens of Laphrentis dalii, Spirifer Keokuk, S. lineatus, S. 8ub-orbicularis, Agaricocrinus, Americanus, Actinocrinus bi-turbinatus, Cyathocrinus stellatus, Archimides, Owenana, Ilemipronites crenistria, Phillipsia, Portlockii, several species offish teeth, etc. The lower portion of this limestone is usually below the level of the creek bottoms, but the upper portion is well exposed on the main creekin township 4 north, range 4 west (Lamoine), and on the east fork in township 5 north, range 4 west (Tennessee). In the region south of Colmar the geodiferous shales and the St. Louis limestone have all been removed by denudation before the depost of the drift, and the boulder clays now rest directly upon the upper part of the Keokuk limestone. A complete section of

Economical Geology

Coal. - As may be seen from a perusal of the foregoing pages, a large portion of this county is underlaid with coal, and although the seams that are found here are much thinner than some of those that outcrop in Schuyler and Fulton counties, yet they have not only furnished an abundant supply of coal for home consumption, but for many years have furnished many thousands of tons annually for shipment south and west to the adjoining counties. The shipment from Colchester alone for the years 1866 and '67 was about 500,000 tons per annum, and the product of the mines have .been constantly on the increase. The coal obtained here is of an -excellent quality, if taken out at some distance from the outcrop, where it has not been exposed to atmospheric influences. The -coal is tolerably hard, bright, and comparatively free from pyrite, and breaks freely into cubic blocks when mined.

Analysis

This analysis shows this to be one of the best coals in the State, and its freedom from pyrite has always made it a favorite coal with blacksmiths of this and the adjoining counties. The coal from the lower seam is usually harder than that from the Colchester seam, and less uniform in quality. Its thickness is also more variable and frequently the coal is wanting altogether, and its place occupied by bituminous shales. Xevertheless, it sometimes attains a thickness of three feet, as at Seaville, in Fulton county, and the coal obtained there is of a fair quality. It is quite probable that this seam may be found in some of the eastern townships in this county as thick as it is at Seaville, and if so, it might be worked to advantage, as its depth below the surface would probably nowhere exceed two hundred feet.

No. 3, if found at all in this county, would be met with in the uppermost layers of the bed rock, and immediately underneath the boulder clays, except at a few points, where it might be overlaid by a few feet of sandstone or sandy shale. It is less persistent in its development, however, than either of those below it^ but its proper horizon may be readily recognized by the dark blue limestone and bituminous shales that are nearly always present^ even when there is no development of the coal itself.

A boring carried down to the depth of two hundred feet would probably pass entirely through the Coal Measures in any portion of the county, and in the western part the subordinate limestone would be reached at a depth of one hundred atd fifty feet or less, when the light gray brecciated limestone of the St. Louis group is reached, it is useless to bore further in search of coal, and this limestone is so decidedly different in its appearance from any of the limestones in the lower part of the Coal Measures, that an expert would find no difficulty in identifying it, even by the smallest fragments taken up by the sand pump. Hence it forms a reliable guide, both where it out-crops and where it may be reached by the drill, and determines the point below which no coal can be found.

Fire-Clay: - The fire-clay under the Colchester coal has been used by Mr. Horrocks, at his kiln west of the town, for the manufacture of drain tile, fire-brick, etc., but recently he has obtained a better quality of fire-clay by sinking a shallow shaft down to the lower or No. 1 coal, which, at his kiln, is about forty-five feet below the Colchester seam. The horizon of this lower coal furnishes an excellent article of tire and potter's clay in various portions of the State, and it may, no doubt, be found at many points in this county, besides the one where it is at present worked.

Iron Ore. - There is a band of iron ore, very generally developed in connection with coal No. 1, and indications of its presence were observed at several points in this county, though not in suf- ficient quantity to justify an attempt to work it at the present time. On the creek below Ilorrock's brick kiln it is about six inches thick, but too sandy to be of much value, even if the quantity was greater. On the creek west of Macomb, a band of very pure iron ore occurs, about six inches thick, and it is quite probable it may be found somewhere in the county of sufficient thickness to be of some economical importance. In Schuyler county, there are two or three bands of ore associated with the same coal, attaining there an aggregate thickness of about two feet, and yielding on analysis about 52 per cent, of protoxide of iron. The ore is an argillaceous carbonate of iron, and compares favorably in quality with the best Pennsylvania ores.

On Mr. D. C. Flint's place in Mound township, a deposit of bog iron ore of good quality is found, which is reported to be several feet in thickness, but the area covered by it has not been ascertained. Should it prove sufficiently extensive and pure as the sample sent to my office, it is a valuable deposit.

Building Stone. - The central and the western portions of the county have an abundant supply of free stone from the sandstone bed intervening between coals Ko. 1 and 2. This is usually from ten to twelve feet in thickness, the upper part thin-bedded and quarrying out in thin, even slabs, suitable for flags, while the lower part is quite massive, and splits evenly. At Stewart's quarries, two miles west of Macomb, there is about twelve feet in thickne&s exposed in the face of the quarry. The rock is a rather coarse grained sandstone, nearly white in color, and furnishes a very durable material for foundation walls, and is also easily cut and may be advantageously used for all ordinary architectural purposes.

At these quarries the rock is very massive, but at the old Mc- Lean quarries, about a half a mile to the westward of Stewart's, the sandstone is more regularly bedded, the layers varying from four to twelve inches or more in thickness. This sandstone is equivalent of that on the T., P. and W. Kailroad west of Seaville, in Fulton county, and is very similar in quality. Some of the beds seem to be sufficiently even-textured for grindstones. The magnesian and arenaceous beds of the St. Louis group will afford the best material for culverts and bridge abutments that can be found in the State, as they are scarcely at all aflected by the action of frost and moisture. The gray limestones of the Keokuk series make a durable building stone if protected from water, but split to fragments on exposure to ordinary atmospheric agencies. The brecciated limestone will make an excellent macadamizing material for the construction of turnpike roads, or for ballasting our railroads.

Limestone for Lime. - Good limestone for burning into quicklime may be obtained from the lower division of the Keokuk, and from the brecciated bed of the St. Louis group. "Where the former is used, it should be selected with some care, as a portion of the beds contain too large a per cent, of argillaceous or silicious matter to slack readily when burned, and would yield only au inferior quality of lime. The light gray semi-crystalline layers are the best for this purpose, and will make a quicklime of good quality. The brecciated limestone is, however, in many respects the best rock in the county for this purpose, as it is usually a nearly pure carbonate of lime in its composition and can be burned at less expense, and makes a quicklime of superior quality. This limestone may be found on most of the tributaries of Crooked creek, and on the east fork as far north as the vicinitj- of Colchester.

Sand and Clay for Brick. - The sub-soil, where it is predicated upon the marly beds of the loess, supplies these materials in nearly the right proportion for the brick yard ; and when deficient in sand, this may be easily supplied either from the creek bottoms or sandy beds interstratified with the drift clays. These materials are so universally distributed that there is scarcely a neighborhood in the county where they may not be readily found at hand.

Soil and Agriculture. - There is not much variety in the general character of the soils in this county, and there is no considerable portion of its surface that will not bring good crops of the various cereals usually cultivated in this latitude, without other stimulants than those contained in the soil itself. The prairie soil is a dark, chocolate-colored loam, appearing nearly black when wet, and produces excellent crops of corn, wheat, oats, barley and grass, and where a proper rotation of crops has been the rule, no perceptible decrease in the annual product has been observed, even on lands that have been under constant cultivation for the last twenty-five or thirty years. The timbered lands are generally confined to the creek valleys, and broken ridges adjacent thereto.

The soil on these timbered ridges is usually thin, but they are excellent fruit lands, and will produce fair crops of wheat, oats and clever, but they require manuring if subjected to long continued cultivation. These thin soils are predicated upon the boulder clays, and the timber growth is mainly black and white oak and hickory ; and their uneven surface does not retain the vegetable and animal matters that are annually deposited upon them, but on the contrary, these are swept away by the annual rains into the adjacent valleys, while on the level prairies they are retained, and add from year to year their fertilizing properties to the soil. The bottomlands on Crooked creek are verv limited in extent, and are mostly subject to overflow. They afford some fine timber, the varieties of which have been enumerated on a preceding page.