THE STORY OF THE ROCKS.
(Two Pictures are included with this chapter: Refectory in Central Park and Lake in Central Park.)
FROM CREATION DAYS-PREPARATION OF THE EARTH FOR THE ABODE OF MAN BY GLACIATION AND INUNDATION-THE PRE-GLACIAL TOPOGRAPHY-THE MISSISSIPPI OF AGES GONE-THE AGE OF THE GREAT ICE-SCOTT COUNTY'S PERFECT DRAINAGE-A WEALTH OF BUILDING STONE-THE CARBONIFEROUS STRATA WHICH HAVE BROUGHT WEALTH-GEOLOGICAL SECTION OF SCOTT COUNTY.
When the six great creative days were fully ended and the heavens and the earth were finished, and all the host of them, when the evening of the sixth day brought the achievement of the marvelous work, the Book records that the Creator of the universe rested from his labors, saw everything that he had made, and behold, it was very good. From chaos, formless and void, had come through omniscient plan and omnipotent will a beautiful planet, fitted for the home of man, a sphere which swung in either in perfect poise with jarless revolution and with certain and flawless procesion. Upon this world which seemed good to its Creator appeared continents, seas, islands and straits. Had there been a spectator upon a neighboring planet when this earth fresh from the creative process took its place in the firmament, to him the western continent would have appeared but an island circled by the sea, the belt of land which was to be in after years the United States but a patch of greens and grays, the magnificent Mississippi valley a blur of color and the state of Iowa an indistinguished item in the harmonious whole. Surely the abiding place of our love and pride is but a speck in the wide-unfolding map of creation, but to us who live in Iowa there is nothing more sure than this, that no fairer spot exists the world around than this small portion of the splendid work that received the commendation of the great Architect, and to those who live in Scott county there is also the surety that nowhere in Iowa has the Creator more kindly planned for his children or scattered in greater measure the blessings of his good will.
For the story of the preparation of the world to be the abode of man from fire mist to finished planet we must go to the geologists and learn of the ages of evolution and gradual change which stretched through time and into a seeming eternity measured only by the stupendous span of the great creative days of the Almightly. To them it is given to read the book of creation in the everlasting hills, to glean history from eroded valleys and learn in stratifications of the living things which enjoyed life in this region when it was under seas. Under Iowa prairies and by the banks of Iowa streams have been found most illuminating records of the ages when the rocky foundations of Iowa were being laid and of the later ages when this substructure was being covered by glacial drift and leveled in prairied sweep from great river to great river. Prof. Samuel Calvin says: "In no part of the world are certain chapters of the Pleistocene record clearer, or fraught with greater interest than in our fair Iowa." This geological eminence Scott county shares with the remainder of the commonwealth, but there is also an especial distinction all our own. Prof. W. H. Norton writes in the report of the Iowa geological survey: "In the diversity and interest of its deposits of glacial drift, Scott county is hardly surpassed by any area of equal size in the United States. Lost pages of Pleistocene history are here recoverable, and evidence is at hand which may hekp to solve questions of long dispute in glacial geology."
In its long preparation for human habitation, its endowment with a climate of pleasing and healthful variety, soil of unexcelled richness and water in abundance, this favored corner of the earth has passed through a most remarkable experience. It has been under the ice not once but four times. It has been under the sea no one knows how many times. It has been traversed by great rivers. It has been covered by strange tropical forests and through its savannas have roamed animals of strange form and uncouth appearance. As a possible human habitat it is very old.
STRANGE CLIMATIC CHANGES
Wise as are the geologists and much as they can read in the rocks and running brooks they cannot tell us what changed the climate of Iowa from the warmth and grateful fruitfulness of the Carboniferous period to the frigidity of glacial days which chilled and killed all life, the stricken land with its vernal crown of grass and woods finding burial under ice of such thickness that material brought from the north by the slowly creeping ice sheet was deposited as soil many yards in depth upon the rocks beneath. What disarrangement of ocean currents, of polar winds or aberration of axis inclination or orbit was responsible we do not know, but there is told in the rocks and soil of Scott county the story of fearful storms of ice and snow lasting thousands of years which piled the ice in mountain semblance in a grinding glacier sheet that made soil in tremendous fashion from the material frozen in the stream of ice and the material that lay beneath. And this cycle of growth and destruction was repeated time and again. The creative plan seems to have contemplated the devastating forces of storm, glaciation and inundation in the preparation of the richiest soils and most beautiful arrangement of land and water forms in this region most fit for the abode of man.
Scott county long ago attracted the attention of scientific men through the interest and importance of its geologic phenomena. Within its narrow borders outcrop the stratifications of three great geological series-the Silurian, the Devonian and the Carboniferous. These formations have contributed greatly to the county's wealth and population through the economic value of the industries arising therefrom, mines of coal and clay, quarries of stone for lime, for building, for road making and for concrete construction. Even as here within the county appear these three great geological systems, there are also here the borders of the drift of three of the continental glaciers which invaded Iowa. Here are plains of alluvium and glacial drift untouched by crumbling erosion. Here are other plains scored and roughened by the action of water, rocky gorges chiseled by rivers in their geologic youth with much rough work ahead, rolling stretches of frontal loess moraines,-all contours which lend variety to the landscape and interest to the searcher after the story of the rocks. Here in our county the great Mississippi and its tributary, the Wapsipinicon, aided by the smaller streams which flow to them have dissected the covering of the underlying rocks making easy the examination of the indurated formations thus exposed and also affording opportunity to study the Pleistocene deposits. The opportunities which nature has furnished in gorge and scarp and hillside ledge have been added to by mines and wells and quarries, by railway cuts and the grading of city streets.
In 1852 David Dale Owen told of the geologic richness of this county in publishing the results of his surveys of the Mississippi valley, paying especial attention to the fossils of Davenport and Buffalo. A few years later Hall and Whitney gave great space to the peculiar features of Scott county in the published account of their survey. Out of thirty-three species of Devonian fossils listed in their search eighteen were credited to Scott county and six to contiguous Illinois territory. The Academy of Sciences at Davenport has a great collection of the fossils of the county, notable contributors being A. S. Tiffany and Rev. Dr. W. H. Barris. The rich fauna of the submerged era has been described by Barris, Worthen, Meek and Lindahl. Much has been written of the glacial deposits of the county by McGee, McWhorter, Pratt, Calvin, Bain, Leverett and Udden, and of the older formations by Barris, Tiffany, Calvin, Norton, Udden and Keyes.
CONSTRUCTIVE AND EROSIVE FORCES.
The variation in the topography of Scott county, even as elsewhere, is the result of two differing forces, the constructive and erosive. To the former belong aggraded stream valleys, the uneroded remnants of drift plains and the hills of the Iowan frontier or border, of one of the great glaciers which reached no farther south than the northern boundary of Scott county. All other relief forms are due to the action of running water, to rain wash or the composite action known as weathering. The Iowan frontier separates two essentially different topographies. To the north the surface is modeled, to the south it is carved. It has been decided by geologists that the pre-glacial surface of the county was not dissimilar to its present condition in this respect, that most of the valleys of the streams were cut before the soft yellow loam which everywhere covers the surface was laid down, as it descends the hill-sides like a mantle well down to the creek bottoms. In this degree the topography is constructive only, modified by erosive influence where the loess has been dissected by a water course of minor importance. Where this loess is of sufficient thickness the dissection is most intricate.
There have been discriminated in Scott county three topogtaphic areas of different ages, the Iowan area, the Illinoian plain and Kansan upland. The Iowan area is one of extreme geological youth. The Illinoian plain is but slightly older, the original plain persisting even to the master streams, its edge being merely nibbled by erosion. From an inland view-point, the channel of the Mississippi disappears from vision and the eye sweeps a level range that takes in the corresponding plain in Illinois as a part of an undivided whole. According to the map of the United States geological survey one may travel from the Green Tree tavern north and west fourteen miles to Walcott and not have changed his elevation above sea level more than twenty feet in traversing the distance. The Kansan upland is of greater age and shows more deeply the effects of erosion, the streams having wider valleys and the hills the rounded summits which tell of age and the wear of the elements.
The fourth glacial invasion, which was called the Iowan, reached the northern boundary of Scott county and the topography of the northern portion of the county was caused by this glaciation, the southern extension of the Iowan drift plain and its frontier in the northern row of townships being marked by the characteristic formation known to geologists as paha. These are boat shaped hills composed of water-laid sand and silt and in part of glacial deposit, the whole molded into characteristic shape by the ice, the longer axis trending northwest-southeast. Sometimes the paha assume the form of long, low swells; sometimes they are individuated into separate hills several of which may be strung along a common axis. As the composition changes from loess to sand and from changes to the irregular hills of Butler township, and the long sandy ridge of the Wapsipinicon plain in Princeton township. Below this region of the paha the county may be considered as at one time covered by an approximately level plain of glacial deposit which was deeply eroded in places and still later covered by the fairly uniform mantle of yellow loess or loam of which mention has already been made.
The report of the Iowa geological survey for this county, written by Prof. W. H. Horton, has a paragraph telling of the appearance of things in the far-distant days before the coming of the first glacier: "A very slight investigation suffices to show that the pre-glacial topography was widely different from that which meets the eye today. Rivers ran hundreds of feet below the present surface. Hills relatively high stood where the level prairie now stretches to the horizon. Were the cover of drift removed from the underlying rocks, their surface would be found rugged and hilly, deeply scored with manifold ravines, and trenched by river valleys deeper than that of the Mississippi, and as wide. But it is scarcely practicable to draw the details of that ancient surface. For the most part we must rely on the records of the wells which have been sunk in the past few years. It is a familiar fact that the well driller finds the distance to rock far from equal even from the same level. In one section the drill grinds on the native rock within fifty feet from the surface; a mile or so away, rock is only found within 300 feet from about an equal elevation. These deep depressions, now plastered over with glacial mud, were cut by running water. They are not local discontinuous pits. They join and form continuous valleys cut out by ancient rivers. Accordingly the deepest drift wells are not found in clusters but in lines."
AN ANCIENT PRE-GLACIAL RIVER.
Perhaps the most interesting statement in Professor Norton's paragraph has to do with the ancient, pre-glacial river bed larger than that of the Mississippi as we know it. The credit of the discovery of this long choked water way has been given to two scientists who approached it from different quarters and traced it with comparative corroboration - Udden and Leverett. This stream seems to have left the present bed of the Mississippi at the mouth of the Maquoketa river, to have come past Goose lake and Brophy's creek to the valley of the Wapsipinicon, thence across Scott county in broad and generous fashion by Druant and Wilton, on through Muscatine county and to the Mississippi channel again near the present location of Fort Madison. The magnificent valley of this noble preglacial stream is occupied by an unambitious affluent of the Wapsipinicon called Mud creek, a stream of a few rods width at its mouth and having a depth of a few feet. This broad and spacious valley, is bordered by hills with the gentle slope, indicating age. They are loess covered, as it the flood plain. Near Durant the ancient watercourse occupied a valley from two to three miles in width and the town is located on an island where the river divided. Three miles from Durant is found the almost imperceptible divide which separates the territory now drained by Mud creek from the valley of Elkhorn creek a tributary of the Cedar river. To the observer who follows the course of this ancient river it becomes easily certain that the two creeks which occupy this river valley never created it.
Some have surmised that in this channel there once flowed the river which in bygone ages was the forerunner of the Mississippi. At one time the Illinoian glacier encroached upon the present soil of Iowa and this river may have been pushed over from its former bed which at that time lay to the eastward of the Mississippi channel as we know it. Later the Iowan glacier crowded the stream back to the eastward and the Cleona channel, as geologists call it, was filled by glacial deposits from this later invasion. This supposition lacks entire confirmation, as the records of deep wells which have been sunk in that region furnish proof that the ancient river bed antedates the Illinoian glacier by a great length of time. It is to this deep channel of this ancient river that Scott county owes its richness in Pleistocene history, for it is in such deep valleys where glaciers must deposit and where they can least erode that the record of glacial days has been laid down. Perhaps it will be well to take from scientific sources the sequence of events in Iowa during the age of the Great Ice.
WHEN THE GLACIERS CAME.
First.-An invasion by glacial ice from the north, perhaps an extension of the Kewatin ice sheet whose center of dispersion lay west of Hudson bay. Little is known of the till deposited by this invasion, and it is termed for the persent the Pre-Kansan drift sheet.
Second.-A stage of deglaciation, the Aftonian, during which the glaciers retreated, probably beyond the limits of the state.
Third.-A second and more formidable invasion by the Kewatin glacier which pushed the ice front south to the Missouri river. This stage and the drift sheet then deposited are known as the Kansan.
Fourth.-A second stage of deglaciation, the Yarmouth, during which the land left bare by the retreat of the ice far to the south weathered into rich soils of prairie and forest.
Fifth.-A third ice invasion, the Illinoian, entering Iowa from the east and occupying a narrow strip of country along the Mississippi extending from the Wapsipinicon south nearly to the Des Moines.
Sixth.-A third stage of deglaciation, the Sanagmon, during which the drift sheet left by the retreat of the Illinoian ice weathered into soil and was covered with peat swamps, savannas and forests.
Seventh.-A fourth ice invasion, the Iowan, coming from the north and extending on its eastern margin as far south as Scott county. Southward from the front of the Iowan ice was laid down in some manner, at present undetermined, a silt called the Iowan loess.
Eighth.-A fourth stage of deglaciation and soil formation, the Peorian.
Ninth.-A fifth ice invasion, the Wisconsin, confined in Iowa to the central portions of the state, and extending as far south as Des Moines.
Of the nine stages just enumerated records of all are believed to exist in Scott county with the exception of the last two, the Wisconsin and the Peorian.
From the deep wells which have been sunk in the Cleona channel came the dense, flaky bluish-black till which is characteristic of the pre-Kansan. Overlying this and under the drift of the Kansan are heavy layers of sand and gravel. The Kansan till which overlies the gravel in these wells comes to the surface as the Kansan upland in the northeastern part of the county. It is a mixture of boulders, cobbles, pebbles, sand, rockmeal and clay, the grist of the glacial mill. This dumping of glacial freight is a thorough mixture. In a cut on the line of the Burlington, Cedar Rapids and Northern road west of Davenport, Professor Norton counted these "erratics," and found fifty-one per cent granitoids, thirty-seven per cent carboniferous sandstone and limestone, ten per cent greenstones and two per cent quartzites. In Liberty township nuggets of native copper have been discovered in this glacial drift. Inasmuch as the rate of progress of modern glaciers confined to narrow channels is but a few inches a year the time it must have taken the diffused Kansan ice sheet to bring this consignment of copper from its Lake Superior home to Scott county is a matter to wonder upon.
When this great Kewatin ice sheet retreated from Iowa, Scott county was neglected in the distribution of its largess of gravel. For the making of Scott county roads it has been necessary to go over county lines and import the Kansan gravels in which other portions of the state are rich. The Kansan glacier left to Scott county its fine-ground grist of blue clay which in time bore savannas of grass and forests of trees. These buried soils with their vegetation have been noted by glaciologists at various localities in the county, overlying the blue clay of the Kansan drift and under the yellow clay of the Illinoian.
It was only a narrow stip of Iowa which was complimented by a visit from the Illinoian glacier. This narrow belt stretches along the Mississippi from the Wapsipinicon to Fort Madison. This invasion from the east left its record in peculiar and characteristic till which has been brought to light by excavations at Sixth and Harrison streets, at Eighth and Marquette streets in Davenport and in ravines two miles south of Blue Grass.
The latest glacier to visit Scott county hesitated upon the northern threshold, giving to the northern tier of townships their peculiar topography and to the whole county the inexhaustible mantle of fine silico-argillaceous silt known as the Iowan loess. Near the Iowan margin it attains a depth of forty or fifty feet. Along the Mississippi its thickness is perhaps twenty-five to thirty feet and in the interior of the county fifteen to twenty feet. This is the soil which has ranked to fertility with the alluvium of the bottom lands and has constantly produced wealth for its owners. It was laid down in glacial waters in a manner not yet understood.
The drainage of Scott county may be considered perfect, as no portion within county borders is more than eleven miles from one of the master streams, the Mississippi and its tributary the Wapsipinicon. Something more than one-half of the territory is drained by the affluents of the Wapsie, as this river is locally known. Geologists have found much to interest them in tracing the channels of the mighty Mississippi. The one known as the Cleona channel has already been mentioned. Nearly cotemporary with this channel they place the present channel from Sabula to Clinton. The channel now known as the Marais D-Ogee, or Meredosia and the Rock river valley is so recent in occupation that the great river still sends a portion of its water by that route at time of highest flood. A slight disturbance of present conditions would be sufficient to send the great stream back to the bed which it so lately deserted, speaking in geologiccal phrase.
THE ROCKY SUBSTRUCTURE.
Students of geology have found no trace of the rocks of the Azoic age in Scott county. The deepest wells that have been drilled have ended in the strata of sandstone which formed the bed of the ocean at some bygone time. The only speciments of the igneous formations are the boulders and cobbles brought in as freight by some predatory glacier. None of the stratification of the Lower Silurian has here been found and only the Niagara limestone of the Upper Silurian system of the Palaeozoic group. The Devonian system is represented by the Dielasma beds, the Spirifer Parryanus beds, the Upper Davenport, Lower Davenport, Independence and Otis. The Carboniferous outcrops in the upper coal measures. The Pleistocene system of the Cenozoic group is in evidence in the glacial drift of the recurring ice invasions.
The great wealth of building stone in the county belongs to the upper or Gower stage of the Niagara limestones, the lower or Delaware stage not having been found locally. In Scott ocunty there are two distinct types of the Gower stone, the pure, hard crystalline dolomite, known as LeClaire stone, which is free from chert and admirably adapted to the manufacture of lime and the light buff granular dolomite, evenly bedded in a stratified formation lending itself readily to building purposes, the latter known as Anamosa stone. The LeClaire limestone is chemically a double carbonate of lime and magnesia, a pure dolomite, free from the ordinary argillaceous, ferrous and silicious impurities. Its normal color is a light bluish-gray, varying to almost white and also to darker shades. While not well adapted for building, it is unsurpassed in the whole geologic category for the manufacture of lime. This formation nowhere in Scott county reaches the thickness of the Linn county beds where it has been observed ninety feet thick.
Very valuable to the resident of the county have been the deposits of the soft granular Anamosa stone. It lies in even, horizontal layers and is ready for laying into wall with a minimum of work in quarrying. This formation is at its best in this county in the region about LeClaire where the stone differs little from the typical quarries near Anamosa except in less frequent lamination and a deeper shade of buff.
The Otis limestone, the rarest of the Devonian system, non-magnesian, dense, of the finest grain, and yielding a fair quality of lithographic material, is found in Scott county, but not in great quantities. The Independence shale, a rough brown iron stained limestone, crops out in Pleasant Valley township in layers from two to four inches thick and carrying nodules of flint.
It is in the Lower Davenport beds of the Devonian that the quarries at Bettendorf and near Camp McClellan have been operating. It is through the Lower Davenport beds that Duck creek cut the romantic gorge at Devil's Glen. This same formation is also found at the West Davenport quarries where it is overlaid by the upper Davenport beds. The workmen can tell by the ring of the steel when they have reached the end of one formation and are beginning upon the other. The beds of the upper Davenport are rich in coral fossils while the other beds are non-fossil-bearing. The upper Davenport is highly fossiliferous, certain layers being a coquina of brachiopod shells so firmly cemented that fossils are disengaged with difficulty and rarely in good condition. The entire thickness of the beds is perhaps fifteen feet. The fossil fauna of these beds have been collected with great pains and have been studied for many years by members of the Davenport Academy of Sciences. In its publications appear lists of species with descriptions of those characteristic of this locality. There have been more than thirty species, Molluscan, Crustacean and Crinoidean noted and classified by the scientists of the academy.
ROCKS CROWDED WITH FOSSILS.
Along the river road near Buffalo may be found culverts built of rock which is fairly crowded with fossils. This rock comes from the Cedar Valley limestone strata which has made the region about Buffalo classic ground for the paleontologist. Large collections have been made from these beds including the type specimens of a number of species. There is a fairly well defined basal bed some thirty feet in thickness consisting of lime stones more or less argilaceous, and calcareous shales normally blue in color, but deeply weathered to buff and brown. The layers which have attracted the most attention are largely made up of fragments of crinoid stems. This stone is capable of high polish and slabs so dinished have been called Buffalo marble by those not over particular in geologic niceties.
The carboniferous strata of Scott ocunty are separated from the great coal fields of Illinois of which they really form a part by the narrow trench of the Mississippi river which is a late corner into these regions in comparison with the coal measures which were laid down by the sea in a long gone ages of creation. The richest deposits lie in Buffalo township, although there are valuable outliers in other portions of the county, largely undeveloped and only awaiting the necessity through the failure of other sources of supply for being worked. Carboniferous deposits have been found in so many wells and quarries that it is not difficult to theorize that practically the whole county once lay beneath the Carboniferous sea and was covered with a continuous veneer of its offshore silts. In his report Prof. Norton tells of the uneven surface upon which the carboniferous muds and sands were laid, of channels and caverns cut by running water in the Niagara limestone more than 200 feet deep. "Since the coal measure outliers in the northern part of the county rest immediately and unconformably on Silurian strata, we may infer that the rocks of that area had formed a land area during Devonian times and had been sculptured by running water with a maximum relief of about 200 feet. With the coming in of the Des Moines stage of the Carboniferous a progressive depression of the land from the south northward brought in the Carboniferous era, at least into the deeper valleys, if not over the entire surface." Evidently when nature writes her book, she is in no hurry to turn a page. Here is the record of one incident, the preparation of the surface for the carboniferous transformation which included the gathering together of soil, the growth of tremendous forests, their inundation and burial beneath immense weight of sand, clay and gravel, where pressure and heat brought forth coal. This one incident comprises the carving out of a channel by running water in limestone strata 200 feet deep. This is an unimportant incident to the geologist. Varily the creations of the imagination are as nothing to the eternal verities of the student of earth structure.
The carboniferous deposits of the county consist chiefly of shales with some sandstone, fire clay and iron stone, argillaceous, bituminous limestones and discontinuous steams of coal.
SOME DEEP WELLS.
Davenport has been for years the artesian city of the state, through the number of deep wells which have been bored. These range in depth from the most shallow, the well at Witt's bottling works, 780 feet, to those of more than 2,100 feet at the plant of the Corn Products company. These deep borings have given great opportunity to study the portion of the earth's crust upon which we live. Prof. J. A. Udden, of Augustana college, Rock Island, has collected and collated a vast amount of information from the records of fourteen wells dug in the three cities of Davenport, Rock Island and Moline, and has constructed from the data a geological section which must so nearly approximate the truth that there is no room for doubt.
Numbers 1-5 are referred by Professor Udden to the Potsdam, and numbers 7-9 are included in the St. Peter.
The sinking of so many deep wells in Davenport has seemed a curious feature of municipal growth to strangers, inasmuch as there flows before the doors of the city an inexhaustible supply of pure, sweet, soft water, which is furnished to Davenport citizens by a pumping plant of great excellence and in a condition of sparkling limpidity after being treated in a filter of such quality and completeness that it is known the world around. It is simply that large consumers have found it economical to sink the wells rather than to pay the water rates made necessary by the expense of transforming the river water into the product marketed.
At Linwood near Buffalo one of the features of a beautiful picnic park upon the shore of the Mississippi is an artesian well, one of the pioneers of the state. It has been running forty years from a depth of 800 feet. The water is strongly sulphurated and in the past attracted to a sanitarium there located many health seekers. The vein of water was struck while drilling for oil.