Lee County, Illinois - Chapter 6: The Geology of Lee County, 1914

Chapter 6: The Geology of Lee County

In attempting to give the rock formation of counties, the historian, generally speaking, is compelled to gather his information from sources not at all reliable, and naturally that portion of his book is unsatisfactory to himself and misleading to the reader. How fortunate therefore it was that 1 was enabled to secure a reliable as well as learned and exhaustive treatment of the subject. Ira W. Lewis, one of the associate editors, discovered the document and referred me to it. I have cojDied and embodied it in this work and I may say with truthfulness that no more valuable information will be found between these covers than the essay of Doctor Everett.

Dr. Oliver Everett, who came to Dixon in the year 1836, beyond an}' doubt was the most learned man who ever lived in Lee county. In the fifty odd years of active practice, he came to be beloved by every person who ever met him. and that acquaintance extended to the four corners of the count,y.

Night and day, for over half a century he rode the country administering to the sick. Nights and days he traveled, first the trackless prairies, then the muddy roads. Many times he had driven for forty-eight hours at a stretch liefore seeking his pillow. To the rich and the poor he ministered alike. If the patient was poor his name never found its way into Doctor Everett's account book and thus a fortune was scattered over the coimty of Lee as his contribution towards building up this c(5mmunity.

In that long and busy practice, he assisted something like five thousand children into this world, and it is with pride that I place my name in the long, long list of children who so early greeted the good old doctor, whose presence and assistance at such a period was so important.

Duriug such a busy life it scarcely seems possible that he should find, time to delve iuto the subject of geology aud natural history. But he did and at the second county fair ever held in Dixon - in 1858, his great collection of natural history specimens attracted state wide attention. He also collected a large number of excessively rare American coins. Where could all of them have drifted ? To deposit them to his memory would have been the appropriate thing to do, but they were neglected after his death, and now all of his specimens have perished. But so long as there is any Dixon, the memory of Doctor Everett will be cherished.

He was an histoiian of I'are merit and nine-tenths of the old items of our history were snatched from oblivion and collected by Doctor Everett. The little book of events, arranged chronologically, and published in 1880, by the Dixon Telegraph, is a priceless thing. And for it we may thank Doctor Everett. He and John Moore, long with the Telegraph, cooperated together in bringing the little book into the world. He gathered the data and John Moore arranged them. That little book contains an account of every important event which goes to make up our history.

Full of years, he passed away beloved by all aud more especially by every member of that great family of "his children" which he assisted into this world of so many uncertainties.

My object, in this paper, is to give some of the results of observations made by me upon the geolog\' of the Rock river valley, in Lee county, and a part of Ogle and Whiteside counties, or from about Oregon, in Ogle county, to Sterling, in Whiteside coimty. The surface in this part of the country is much more rolling, or undulating, than in most parts of the state. This is particularly the case in the upper portion of the section alluded to in Ogle county and part of Lee county, where it is frequently cut up into deep ravines, on the sides of which the underlying rocks are often exposed to view ; and the banks of Rock river and its tributaries frequently present bold, perpendicular bluffs of rock, from fifty to two hundred feet high, thus giving a tolerably good opportunity for geological investigations. These features are most prominent in the region of one member of the geological series of which I shall hereafter speak, viz., the Upper or St. Peter's sandstone. In another section, where the Trenton lime rock underlies the drift, there are frequently found deep pits in the ground. These pits are generally more or less circular, and are from one to two or three rods in diameter, at the surface of the ground, and run to a point below. They are from ten to twenty and sometimes thirty feet deep, and have, evidently, been produced by the earth, in these places, falling into and being carried away by subterranean streams of water in the loose rock below.

Below Dixon, although the surface is considerably undulating, it is not so abruptly broken by deep ravines, and the prairies generally slope gradually to the banks of the river, seldom exposing the rocks at all. Below Dixon there is very little woodland along the banks of the river, while above, between Dixon and Oregon, a considerable portion of the country along the river is covered with timber. The timber is not generally of very heavy growth, although, in some places, on the bottom lands, it is quite large. It consists of the various species of oak and hickory common to the state, the black and white walnut, the sugar and silver-leaved maple, box-elder (Negundo accrifoliiun), sycamore, the red and white elm, hackberry, ash, linden, eottonwood, etc. The red cedar, the white pine, the ground hemlock (Taxus Americana), the black and the paper or canoe birch (Betula lenta and Betula papyracea), are found on the extreme verge of the rocks overhanging the river and creeks, beyond the reach of the pi'airie lii'es. All these last mentioned species, except the red cedar, are found, as far as I have observed, only upon the bluffs formed by the St. Peter's sandstone.

We should naturally expect to find on a soil produced from the disintegration of this sandstone, some plants which are not common to the rich alluvial and clayey soils of a large portion of the state. Accordingly I have found several species not included in Doctor Lapham's catalogue, and some of them not in the additional lists subsequently made by Doctors Brendell and Bebb, and which I presimie are not often found in other parts of the state. Among which I might name two species of vaccinium, the Aretostaphylos urauisi, Lupenu perrennis. Campanula rotTuidifolia, Talinum teretifolium. Lobelia kalmii, Cerastium oblongifoliimi, Linaria canadensis, Fragaria vesca, and the Viola lanceolate,

The drift formation, through this section, is probably not so thick nor so uniform in depth as in most parts of the state. There are many things in relati(ui to it Avhich have peculiar interest, but my object in this paper is to speak of the rock iDeneath it.

There is in this section of about thirty miles of the Rock river valley, a pretty good opportunity to study several important members of the lower Silurian system and some of the lowest strata of the upper Silurian series.

Commencing at Oregon, with the St. Peter's sandstone, and ascending the geological scale, as we go down the river, we find the Buff: limestone (of Owen), the Trenton limestone, the Galena limestone, and the shales, etc., representing the Hudson river group of the lower Silurian system, and the Niagara limestone of the ui^per Silurian series.

The lowest rock which we find in the section under consideration, is the Upper or St. Peter's sandstone. It is the i^revailing rock along the river, from a mile above Oregon to about three miles below Grand Detour, a distance of thirteen or fourteen miles. On the northwest side of the river, I think that in no place does this rock appear on the surface more than two or three miles from the river. On the southwest side it extends several miles back from the river. I should think that the thickness of tins rock could not be less than two Inmdred feet, and probably more. The country where this rock prevails is characterized by great unevenness. It is frequcntl.y cut up into deep and sharp ravines, and, in many ]daccs, there are bold, precipitous liluffs, fi'om oue to two hundred feet high. I have not often found these bluffs capped with the Trenton limestone, as spoken of by Professor Hall as being the case in Iowa. In ui;iiiy places this sandstone is interspersed with munerous hoiizoutal l)ands or la^^ers of iron, or sandstone so impregnated and ('emcuted with the oxide of iron, as to be very firm and resisting. These layers are from less than half an incli to two inches in tliicl'Cncss, and occui', oue above another, in some places but a few inches, and in others several feet apart. These layers resist the action of the atmosphere for a great length of time, and only give away from the disintegration and weai'ing awav of the rock beneath, when thev break off and fall from their

It appears as if, during the deposition of this rock, that occaisonally, in these localities, the surface was in some way covei'ed with a sediment of the oxide of iron, which acting as a cement, rendered this portion of the rock much harder and tirmer than other parts of it. If you will examine one of these layers with a magnifying glass, you will see that they are made up principally of the same minute peculiarly formed grains of quartz, of which other portions (if the rock is composed, stained and partially covered with the oxide of iron. We frerpumtly find very beautiful ripple marks on these ferruginous layers. On some of them the impress of the eddies and ripples of the old Silurian ocean a})pear as fresh and palpable as if i:)roduced l)ut xcstcrday. Tlu'se markings are sometimes very singular and curious, mimicking the forms of organized life. Here is a specimen which I have been at a loss to determine whether it has Itecn jn'oduced Iiy the action of the water or is an impression of some oi'ganized being. This rock is composed of small rounded gi'ains of pure limpid quartz, which have a singular uniformity in their size and shape, in some places cohering so slightly as to cnunlile in the hand, and in other localities so fi]'ndy cemented as to make a good I)uildiug .stone. This rock is in some places of almost chalky whiteness, liut more commonly it has a grayish aspect, while in other localities it has a reddish appearance, being stained with the oxide of iron.

As to the economical uses of this rock. There are several quarries in the Franklin creek, in Lee county, and in Ogle county, where it has been pretty extensively used for building, and cut into window and door sills and caps. There was a beautiful arched bridge of cut stone, from one of these ([Uarries, built over Franklin creek, for the Chicago and Fulton railroad, when it was first constructed. Professor Hall says that this rock would make an excellent material for making glass.

It will be perceived that this rock, as it is found in the valley of Rock river, vaiics considerably from the description of it given by Professor Hall as it occurs in Iowa. Instead of its being uniformly the loose, friable rock, spoken of by ^Nfr. Hall, with scarcely cohesion enough to enable him to obtain calnnet specimens of it, we frequently find it forming liold, perpendicular, and sometimes overhanging cliffs, with strength and tenacity enough to make a good building stone. There are places where the rock is flinty and

Buff Limestone

Next to the St. Peter's sandstone, and separated from it in some places by two or three feet of shale and bluish clay, comes the Buff limestone of Owen, classed by Hall with the Trenton limestone. This is a thick bedded, comi^act, semi-crystalline magnesian limestone, in layers of from one to two feet in thickness. It crops out in many places above the St. Peter's sandstone.

Between these thick ledges there are thin shaly layers, an inch or two in thickness, abomiding in fossils. Although those layers are full of fossils, there appears to be but a very few species. They are very imperfect - most of them are casts, and appear to be such as are common to the Trenton limestone proper. This rock is often quite fine grained and compact, and makes an excellent building stone. Prom an analysis <»f specimens of this rock in Iowa, Professor Hall thinks that it may be very useful for the manufactiu'e of hydraulic cement, as its composition was found to more nearly resemble than any of our other magnesian limestones, that of the best rocks used for that purpose in other places. These thick bedded lavers ai'e from twehe to eighteen feet in thickness.

Trenton Limestone

The blue limestone of the western geologists, or the Trenton limestone of the New York survey, succeeds these magnesian beds. This rock is quite variable in its appearance. In some places it has a bluish color, ])articularly on a recent fracture, but more frequently it is of a dull buff color. It is not so thick bedded as the preceding rock, and is in sonic ]tlaces <|uite shaly, and breaks up into small fragments when quarried. In other places the layers are compact and thick enough to make a good building stone.

There are vertical crevices frequently found in this rock, which are fi'om two to fifteen inches in width. Sometimes they are filled with debris, and in other places are open and serve as channels for subtei'ranean streams of water from the pits in the elevated ground back from the bluffs, which I have spoken of above. At the base of the bluff, after a heavy shower, or at the breaking up of the winter, swollen streams of tui'bid water may be seen rushing from them.

The Trenton limestone abounds in fossils. It is the oldest rock in this country in which we hnd a great profusion of the remains of organized beings, showing be}'uud doubt that the ocean of the lower Silurian era was tilled with a multitude of the lower forms of animal life. Here is a sijecinien not much more than twice as large as a man's hand, that has representatives from three of the grand divisions of the animal kingdom. This central figure is a fine large trilobite, a beautiful specunen of the Articulata; and here are several fragments of coral and the stem of an Encrinite from the Radiata, while the Moiusca is represented by several of the Acephala and a Gasterapod. There are great numbers of Arthocerata found in this rock. Some of them are of very great size. I have seen sections of them that were eight inches in diameter. I have a part of one in ni}^ collection which is not more than six inches in diameter at its largest part, that is eight feet in length. Ammonites of considerable size are found in this rock. Among the Acephala are several species of Septaena. Strophomena, Orthis, etc., are common in some of the layers of this rock.

This rock is somewhat extensively used for building material, although for that purpose it is not equal in value to the magnesian beds below it. It makes ex;cellent lime, and is extensively used for that purpose. Some of the layers of this rock, in this locality, are made up almost exclusively of fossil shells and corals, and are very compact and fine grained, and receive an excellent polish, making a very beautiful figured marble. The Trenton limestone is found principall}^ in the bend of the river, in the upper part of Lee county, extending about four miles south, and is also f(jund in a narrow belt on the northwest side of the river, extending from Pine creek, in Ogle county, to within a mile of Dixon.

Galena Limestone

The Galena limestone succeeds and rests upon the Trenton limestone. The line of demarkation between this and the Trenton limestone i'^ not always easily ascertained. Layers, partaking sometimes more of the characteristics of one of these formations and then the other, are often foimd intermingled for some distance, although the charactei'i sties of the mass of the two formations are very distinct. It appears to be the prevailing rock, underlying the surface of the elevated prairie, over a considerable portion of the northwestern part of the state - the streams having in many places cut down through it into the strata beneath. The

Galena limestone is a rock peculiar to the West, and is a very important member of the lower tSilurian series. It is important not only from its thickness and the extent of country which it covers, and the many economical uses made of the rock itseli^, but from the rich minerals it contains, it being peculiarly the leadbearing rock of the Northwest, as is indicated by its name.

The Galena limestone is a coarse-grained, porous, and sometimes friable rock. It has a dull grayish and sometimes yellowish color and, from its jjorous character, weathers out very rough and irregularly. It is everywhere characterized by its j^eculiar fossil, the simflower coral, the Coscinapora sulcata or recepticalites of Hall. In the lower beds of this rock there is a very beautiful species of Favosite quite common. Its pentagonal columns oi' rather tubes, tilled with transverse lamina of a pure sileceous material, radiating from a point, present a very beautiful appearance, particularly on a recent fracture. This coral is often found in large masses where it has weathered out of the rock, sometimes entire, but more frequently broken into fragments. Among the Gasteropods found in this rock are the ^Marehisonia. Pleurotomaria, etc. The Orthoceras, Crytoceras, Anunouite, and some of the bivalves connnou to the Trenton limestone, are often found in the lower beds of this rock. This limestone is the prevailing rock along the liver, fi'om a mile al)Ove Dixon, to near Sterling, where it disappears beneath the Hudson river group and the Niagara limestone. This rock, as may be seen by the map, spreads out over a much greater extent of country as we go back from the river, on either side.

On the inmiediate l)anks of the liver, along the rapids at Sterling, and at the base of the bluffs a mile above town, on the north side of the river, may be seen the various rocks, shales, clayey and bituminous deposits described l)y Professor Hall as the Hudson river group. The rapids in Rock river at Sterling seem to have ])0('n ])rodueed liy the weaiing away of the shales of this formation. 1 have l)een unable to ascertain what the exact thiclaiess of this grou]) may be, ))ut think that it is probably not more than twenty-live or iliiiiy feet. On the map accompam'ing this paper T have re])resent('d this formation in a narrow belt, surrounding the Niagara limestone, on the east and north side.

Niagara Limestone

The Niagara limestone is found on the north side of the river, above Sterling, extending through the northeastern part of Wliiteside county. This rock is also a magxiesian limestone, and resembles, in its composition and appearance, the Galena limestone. There is a good opportunity to examine this formation at the quarries, a mile above Sterling. Thei'c it may be seen resting on a green compact rock of the Hudson river group. The lines of charts common to this rock are found there in abundance, sometimes forming layers six inches thick. The characteristic fossil of this rock, the Catenapora Escharoides, and a beautifid species of Favosite are common there. I also noticed a species of Marchisonia and two or three bivalves. The rock from these quarries makes an excellent building stone, and is extensively used for that purpose.

[It may be added that in Ashton, Lee Center, Reynolds and Amboy, there are small quarries, removed from the river and the creeks tributary to it, the Ashton quai'ry in particular furnishing a beautiful building stone. St. Luke's Episcopal church is built of it. It is a hard sandstone, and doubtless of the character men-'* tioned by Doctor Everett. - Editor.]