Hamilton County, Ohio - Geology and Topography, 1881

Geology and Topography

THERE was life in the valley of the Ohio untold ages before man came to gaze upon its beautiful hills and waters. Away back in the stately march of the geologic epochs, the Silurian seas here swarmed with animate existence, many of its forms so small that the aid of the microscope is needed to trace them; and some so numerous that great and valuable layers of rock are composed almost wholly of their remains. The history of the countless varieties of sentient life that so abounded here zons on zons ago may be read for us only in the rocks of the valley and the hills. It is otherwise unwritten, except in the books of their Creator. Industrious inquirers, working slowly and carefully through many years, have traced the forms of them, have given them names, and catalogued them. It does not fall within the province of this work to present a list of these. It may suffice for our purposes to say that the paleontological catalogue published within two or three years by Professor Mickleborough, of the Cincinnati normal school, and Professor Wetherby, of the University of Cincinnati, represents no vertebrate, and their presence in the rocks of Hamilton county is exceedingly rare; but from. the sub-kingdoms are presented fifty-seven species of annulosa (besides seventy-eight undetermined), one hundred and forty-five of mollusca, one hundred and thirty-nine of molluscoida, sixty-three of coelenterata, and nine of protojoa, besides sixteen species representing, in a very small way, the vegetable kingdom.

The duty of the historian, in this, one of the opening chapters of this work, is to present something of the topography and geology of the county. In accordance with our custom in this series of local histories, we rely almost exclusively for these upon the authorized Report of the Geological Survey of Ohio, for which the section relating to Hamilton county was prepared by Professor Edward Orton, now of the State university at Columbus. What follows is taken almost verbatim from his report, with the addition of two or three foot-notes, and some slight changes in and arrangement of the text.

I, Topography

The first division embraces all the higher table-lands of the county, which have a general elevation of two to five hundred feet above low-water at Cincinnati. All of these areas, though often covered with superficial drift deposits, are underlain with bedded rock, which is everywhere easily accessible, and which impresses peculiar features upon the face of the districts that contain it.

To the second division are referred the valleys of the' county, and not only those which hold the present rivers, but also-those in which no streams of considerable size are now found, but which are due to the eroding agencies of an earlier day. Both of the classes of valleys are often filled with heavy accumulations of drift, but they agree in being destitute of bedded rock - except at the levels of the streams they contain, or, as is often the case, at considerably lower levels.

The thickness of the drift beds does not generally exceed one hundred feet, and thus it will be seen that in the Ohio valley the lowlands have a maximum elevation of one hundred feet above low-water at Cincinnati; but as we follow back the Miamis and the lesser streams, we find these beds assuming higher elevations, as the floor of the country that sustains them is gradually elevated, so that they sometimes attain, in the northern and eastern portions of the county, a height of one hundred and fifty or even two hundred feet above the same base.

In other words, the highlands of the county are the areas in which the bedded rocks remain, to an elevation of three hundred feet and more above the Ohio river, while the lowlands are those areas from which the rdcks

The slopes that connect these two kinds of areas are commonly precipitous, asin the river-hills of Cincinnatt; but sometimes the descent is broken by the interposition of drift deposits.

The valley of the Ohio, which here runs in an east and west direction, makes the southern boundary of the county, and, though deep, is comparatively narrow. Several of the north and south valleys that traverse the county are absolutely wider than the Ohio valley; and when the volumes of the streams that they contain are taken into the account, the disproportion between them and the first-named valley is very great. A sitnilar state of facts obtains through southwestern Ohio - the valleys that trend to, the west of north especially having been excavated on an ampler scale than the rest, other things being equal. These. facts seem to point to glacial erosion as a prominent cause in the production of the surface features of the country, as the glaciers are known by the striae they have left to have advanced from the northwest.

An examination of the map of the county, * in the light of the facts already known, will serve to show, what an acquaintance with it abundantly confirms, that its surface has suffered a vast amount of erosion. The most interesting facts in this connection are not the valleys which are occupied by the greater streams of to-day, but those deep and wide valleys that are at present either entirely deserted by water-courses or traversed by. insignificant strenms, wholly inadequate to account for the erosion of which they have availed themselves. Attention will be called to one or two instances of this sort.

The broad valley now occupied in part by Mill creek, and in part left entirely unoccupied, extends continuously from the present valley of the Great Miami at Hamilton to the Clifton hills, just north of Cincinnati, where it divides into two branches - one passing to the north and east of the city, and entering the valley of the Little Miami between Red Bank station and Plainville - while the other branch, the present valley of Mill creek, passes directly to the Ohio through the site of the city of Cincinnati.

No rocky barriers - nothing, in fact, but the same drift terraces that make the walls of its present course - shut out the Great Miami from entering the Ohio valley at the same points where the Little Miami and Mill creek now enter. Indeed, there is the best of reasons for believing that it has followed, in the past mutations of its history, those very courses to the great valley. Mill creek has taken possession of the middle portions of this valley, but has never occupied more than one of its lower branches, that one the narrower.

The most striking examples of this erosion of an earlier day are to be found, however, on the western side of the county, and are, for the most part, to be referred to the same river whose agency has already been invoked.

northeastern part of Crosby township, which bears due westward from the present course of the Great Miami. Near the west line of the township this old channel_is deflected to the southward, and is thenceforward occu. pied by the Dry fork of Whitewater, until it is merged in the valley of this last-named river. That the streams which hide themselvas in this great valley to-day have had next to nothing to do with its excavation, is evident from the fact that there is not one of them whose course agrees with the direction of the valley, but all cut across it transversely. More than half of the townships of Crosby, Harrison, and Whitewater have been thus worn away and made to give bed to the rivers in the successive stages of their history. The channel above named can be confidently set down as another of the earlier courses of the Great Miami.

Still a third of these old channels, more interesting in some respects than either of the two just named, is found near Cleves, Miami township. By reference to the map, it will be observed that the river here approaches within a mile of the Ohio; but, instead of entering the great valley at this point, it makes an abrupt detour to the west and south, and only reaches its destination after a circuit: of ten miles. Its approach to the Ohio at Cleves is blocked by a ridge that is interposed, one hundred and fifty to two hundred and seventy-five feet in height. A tunnel that was carried through this ridge, in the construction of the Whitewater Valley canal, and which is at present used by the Indianapolis & Cincinnati railroad, shows it to be composed of glacial drift. The direction of this channetis in the line in which the glaciers advanced, so that its existence can be quite plausibly

"ascribed to the great agents of denudation. Whether or not the origin of this channel can be referred to the glacial period, its closure was certainly effected there.

It tasks the imagination to account for the excavation of these broad and deep valeys by existing erosive agencies, even when they are reinforced by the important additions of glacial ice; but to agencies identical with these the work must be referred. There is no evidence, as has already been shown, of minor flexures or axes of disturbance in the Blue Limestone region, by which the strata could have been thrown into hills and valleys; but, on the contrary, the beds are found to occur in unbroken regularity, being affected only by the slight general dip, of which account has: been previously given. It is scarcely necessary to say that opposite sides of valleys give every possible proof of having been originally continuous, the sections which adjacent exposures furnish being absolutely identical in their leading features.

The Cincinnati group has been found to demand for its original formation long-continued cycles of peaceful growth and deposition, and in likes manner the fashioning of its bed into the present topographical features of the country must have been in progress through such protracted ages that the historic period in comparison shrinks into insignificance.

[The correctness or necessity of the appellation, "Cincinnati group," which often occurs in the geological reports, is gravely doubted by the local geologists. In January, reported to the Cincinnati Society of Natural History "that the fossils found in the strata for twenty feet or more, above low-water mark of the Ohio river, in the first ward of the city of Cincinnati, and on Crawfish creek, in the eastern part of the city, and in Taylor's creek, east of Newport, Kentucky, at an elevation of more than fifty feet above low-water mark in the Ohio river, indicate the age of the Utica Slate group of New York. A fauna is represented in these rocks that-is not found above or below them. Moreover, brown shales and greenish blue shales and concretionary nodules give a lithological character to the strata which distinguishes them from the strata both above and below." All strata containing "7tarthrus becki, the committee hold, are to be referred to the age of the Utica Slate group of New York. Above its range is the Hudson River group. The Trenton group is not exposed at Cincinnati nor in the Ohio valley anywhere west of the city, but is probably represented in the rocks of Ohio a few miles east of that point. The Utica group is not represented elsewhere in Ohio. All the lower Silurian rocks jn southwestern Ohio belong to the Hudson River group, except the small exposure of the Utica slate in the banks of the Ohio and east of the city in the immediate vicinity of the river. , The committee therefore report that the name '"'Cincinnati group" should be dropped, "not only because it is a synonym, but because its retention can subserve no useful purpose in the science, and because it will in the future, as in the past, lead to erroneous views and fruitless discussions." Investigation, so far, they add, has not Ied to any other or further sub-divisions than those formerly adopted. ]

Strictly speaking, there are no hills in Hamilton county, the surface being all referable to the table-lands and to the valleys worn in them. What are called the Cincinnati hills, for example, are merely the isolated remnants of the old plateau, which have so far escaped the long-continued denudation. Indeed, the highlands of the county are all of them outliers or insulated masses, surrounded on every side by the valleys of existing rivers, along the deep excavations wrought out by these streams at an earlier date and under somewhat different geographical conditions. These islands of the higher ground vary in area between quite wide limits,- some of them containing a few scores of acres, and others as many square miles.

The high ground immediately appertaining to Cincinnati furnishes a good example of these outliers. By reference to the map, the insulation of this high ground will be seen to be perfectly effected by the Little Miami vailey, the Ohio valley, the Mill Creek valley, and the abandoned channel of the Great Miami, already deéscribed, on the northern and eastern sides. Very important consequences result to the city from this insulation. It follows, for instance, that there are but two natural ways of ingress to the city by lowland, or, in other words, that there are but two railroad routes possible - one by the Ohio valley and the other by the Mill Creek valley.

vorable, especially as ways of approach from the east. These difficulties have led to the project of reaching the business center of the city by a tunnel from the northern valley. -

The Dayton Short Line railroad encounters, near West Chester, one of these outliers in its route, which necessitates a grade of forty-five feet to the mile at this point - the highest grade, in fact, on this line (New York Central) between tidewater and the Ohio river.

Another very noticeable outlier is found a mile west of North Bend. The Ohio & Mississippi railroad skirts it on the Ohio valley side, while the Indianapolis & Cincinnati road passes to the north of it, through the old glacial channel, which has already been described.

The upper division of the Blue Limestone or the | Lebanon beds has never been found in Hamilton county. The lower boundary of the Cincinnati group has not yet been definitely fixed, but enough is known to make it certain that it is not found among the surface rocks of Ohio. The approximate place in the general geological scale of the strata exposed in the hills of Cincinnati has long been known. For the last forty years, at least, they have been referred to the later divisions of Lower Silurian time and recognized as belonging to the Hudson or Hudson River group of the New York geologists and of the general geological scale of the country.

The Cincinnati beds proper come next in order after the Point Pleasant beds, in Clermont county, which are the lowest rocks of the series in the State. They have fo¥ their inferior limit low-water in the Ohio and for an upper boundary the highest stratum found in the Cincinnati hills. The greatest elevation above low-water in the immediate vicinity of Cincinnati is given by the city engineer as four hundred and sixty-five feet. Abating fifteen feet for the drift covering of the surface, we can certainly find forty-five feet of bedded rock in this division, almost every foot of which lies open to study within the city limits. The only stratum, however, that admits of easy identificatidn, lies at an elevation of four hundred and twenty-five feet above the river; and this is accordingly assumed as the upper limit of this division.

Upon differences in lithological character, with which also changes in fossil contents ally themselves, a subdivision of the Cincinnati beds is possible into three groups, which may be named respectively, in ascending order, the River Quarry beds, the Middle Shales, and the Hill Quarry beds. The first of these subdivisions has a thickness of fifty feet, the second of two hundred and fifty feet, and the third of one hundred and fifty feet.

Above the highest stratum of the Cincinnati hills and the lowermost beds of the Upper Silurian age, three hundred feet of rock intervene, that belong unmistakably to the same formation, being connected with it by identity in lithological character and by a large numter of common fossils. These upper beds are nowhere found within twenty miles of Cincinnati, and yet there has never been the slightest hesitation in referring them to the same series to which the rocks there exhibited belong.

No explanation is necessary of the first and the last of these names. To the intervening division a name can properly be assigned, derived from the name of the park on the eastern side of the city, in the grading of which so great a display of this division is made. This division can, therefore, be styled the Eden shales, from the Eden park.

The whole series of the Cincinnati group is composed of alternating beds of limestone and shale. The 'shale is more commonly known under the name of blue clay; and this designation.is not inappropriate. It is sometimes styled marl or marlite, and the use of the latter designation is also justified by its composition. The most objectionable term by which it is characterized, is soapstone, as this name is pre-occupied by a metamorphic magnesian silicate.

The limestone of the series may; in general terms, be described as an even-bedded, firm, durable, semi-crystalline limestone, crowded for the most part with fossils through its whole extent and often bearing upon its surface the impressions of these fossils. Its color is not uniform, as the designation by which: the whole series is familiarly known, "blue limestone," would seem to imply. The prevailing color, however, may be said to be a grayish blue, chiefly due to the presence of protoxide of iron, which, upon exposure, is converted into a higher oxide. The weathered surfaces generally show yellowish or light gray shades, that are in marked contrast with the fresh fracture. Drab-colored courses occasionally alternate with the blue.

The limestone varies in all these respects somewhat, however, in its different divisions. The Point Pleasant beds, and the lower courses of the Cincinnati division, deviate most widely from the description already given. They are lighter in color than the upper courses and in some instances are slaty in structure, while in others they havea tendency to assume lenticular forms of concretionary origin, sometimes to such an extent as to destroy their value as building-rock. The layers are also exceptionally heavy, attaining a thickness of sixteen or eighteen inches, and are often so free from fossils as to afford no indication of the kinds of life from which they were derived.

A few feet above low-water at Cincinnati, a very fine and compact stone comes in, that is found in occasional courses for fifty to seventy-five feet. It is composed, as its weathered surfaces show, almost entirely of crinoidal columns, mostly of small size, and mainly referable to species of heterocrinus. The courses vary in thickness from aninch toa foot. The lighter layers ring like potmetal under the blows of a hammer.

Ascending in the series, the limestone layers are very generally fossiliferous and are rarely homogeneous in structure, being disfigured, to a greater or less degree, by chambers of shale or limestone mud, from some of which cavities, certainly, fossils have been dissolved. The thickness of the courses varies generally between the limits indicated above, but a large proportion of the stone ranges between four and eight inches. Now and then, however, a layer attains a thickness of twenty inches, or even two feet. Near the upper limits of the formation the layers are thinner and less even than below, affording what quarrymen call "shelly" stone.

The composition of the limestones from the upper half.of the group is quite nearly uniform, averaging about ninety per cent. of carbonate of lime; but as we descend in the series the limestones grow more silicious.

The shales, clays, or marlites, which with the limestones make up the Cincinnati group, must next be characterized. They constitute a large part of the system, certainly four-fifths of it in the two lower divisions, and probably not less than three-fifths of its whole extent. The proportions of limestone and shale do not appear altogether constant, it is to be observed, at the same horizon, a larger amount of stone being found at one point than at others.

The shales, as implied in one of the names by which they are known, "blue clay," are generally blue in color, but the shade is lighter than in the limestone. In addition to the blue shales, however, drab-colored clays appear in the series at various points. As the blue shales weather into drab by the higher oxidation of the iron they contain, the conclusion is frequently drawn that the last-named variety marks merely a weathered stage of the former. But, aside from the impossibility of explaining the facts as they occur on this hypothesis, analysis disproves it, and shows that the differences in color are connected with essential differences in the composition of the belts to which they belong:

Most of the shales slake promptly on exposure to the air, and furnish the materials of a fertile soil; but there are other portions included under this general division which harden as the quarry-water escapes, and become

The shales are sometimes quite heavily charged with fossils, which generally have a firmer structure than the material that encloses them, so that the fossils, often in an admirable state of preservation, 'Yemain behind after the shales have melted away. All of the groups of animals that are represented in the limestones are found also in the shales; but from the unequal numbers that are represented here to-day, it seems evident that some sorts were able to adapt themselves to the conditions which shaly deposits imply much more easily than others.

The proportions of limestone and shale in the series we have already spoken of in a general way; but it will be profitable to give additional statements on this point. In the River Quarry beds, the lowermost portion of the Cincinnati beds proper, there are about four feet of shale to one foot of limestone, but the shales increase in force as we ascend in the series, until at about one hundred feet above low-water the proportion was more than twice as great. For the two hundred feet next succeeding, that have been styled the Eden shales or Middle shales, there is seldom more than one foot of stone in ten feet of as- cent. The amount of waste is so large, therefore, that quarries cannot be profitably worked in this whole division. The third portion of the series, the Hill quarries, 'have often lower limits - the beds in which the solid rock has risen again to as high a proportion as one foot in five or six feet of ascent. From this point upward to the completion of the group, there is no such predominance of shales as is found below, though in the lower parts of the Lebanon beds shales still constitute more than onehalf of the whole thickness.

It is seen from analyses made that a notable quantity of alkalies and phosphates, sometimes at least, occurs in the composition of the shales. . It is upon these substances that the fertility of soils in great measure depends; and as they are in this case properly distributed through the sand and clay that make the bulk of the shale, it is in no way surprising to find very fruitiful soils forming from the weathering of these beds. The most noteworthy fact in this connection is the rapidity with which they are converted into soils. Most of the rocky shales of the State require a long course of progressive improvement before they can be justly termed soils. Their elements are slowly oxydized and disintegrated, and vegetable matters slowly added. The exposure of a single season, however, suffices to cover the Cincinnati shales with a varied vegetation. All of our ordinary forest trees, when opportunity is furnished for the distribution of their seeds, establish themselves promptly upon the shales. The black locust seems especially well adapted to such situations, There is no other use to which the steep slopes of the Cincinnati hills can be turned that would subserve as many interests as planting them with black locust would do.

Dr. Locke called attention to a peculiar feature of the Blue Limestone beds, viz., a waved structure of the solid limestone, somewhat analogous in form to the wave-lines and ripple-marks of the higher series of the State. This peculiar structure was noticed by him in the upper beds of the formation, but it is even a more striking characteristic of the rock in its lower beds, as shown in the river quarries of Cincinnati, or in the lowermost hundred feet that are there exposed.

The rocks exhibiting this structure at the point named are the most compact beds of the fossiliferous limestone. The bottom of the waved layer is generally even, and beneath it is always found an even bed of shale. The upper surface is diversified, as its name suggests, with ridges and furrows. The interval between the ridges varies, but in many instances it is about four feet, The greatest thickness of the ridge is six or seven inches, while the stone is reduced to one or two inches at the bottom of the furrow, and sometimes it entirely disappears. The waved layers are overlain by shale in every instance. They are often continuous for a considerable extent, and in such cases the axes of the ridges and furrows have a uniform direction. This direction is a little south of east in the vicinity of Cincinnati, but in traversing the series these axes are found to bear in various directions.

The only other explanation thus far proffered is that suggested by the name, viz., that the floor of the Cincinnati sea was acted on from time to time by waves or similar movements.of the ocean waters. In opposition to this view it may be said: First, that there are many reasons for believing that the Cincinnati rocks grew upon the floor of a deep sea, far below the action of the surface waves; and, second, that the fact of the limestone layers alone being thus shaped is sufficient to set aside the explanation. If these inequalities of surface are due to wave-action of any sort, it is impossible to see why the action should be limited to the firmest limestone beds 'of the series, while the soft shales, which could easily register any movement of the waters, never exhibit the slightest indications of such agencies.

While both of these modes of accounting for the facts are rejected as entirely unsatisfactory, nothing in the way of explanation will be offered here, save the suggestion that the facts seem to point to concretionary action as the force to which we must look.

The Economical Products

of the Cincinnati group are limited to building stone, lime, brick and pottery clays, and cement; and of these none but the first two have, at present, any great importance. The series yields everywhere abundant supplies of stone, suitable in every respect for building purposes. The advantages that the city of Cincinnati reaps from the quarries that surround it, are immense. While blue limestone has been used as a building stone from the first settlement of the country, it has hitherto enjoyed the reputation of being serviceable rather than beautiful; but within the past few years it has been so treated by combination with other building stones as to produce very fine architectural effects. Numerous exhibitions of this skilful use of the blue limestone can be seen in the recent buildings of the city and suburbs of Cincinnati. The analysis of the stone shows it to contain ninety or more per cent. of carbonate of lime. From this it 'will be concluded that it can be burned into a lime of a good degree of purity and strength. When water-washed pebbles from gravel 'banks or river beds are used, the product so much of the interstratified shale as to darken the lime and so reduce its value for plastering. For this last use the mild and white magnesian- limes derived from the

Upper Silurian formations that surround. Cincinnati, arethe only varieties that are at present approved. The native supply can, however, be furnished much cheaper at but little more than half the cost, indeed, of Springfield lime; and as it makes a strong cement, the shales that adhere to the stone possibly adding an hydraulic quality, it is generally used in laying foundations of all sorts.

The shales are sometimes resorted to for the manufacture of brick, tile, and pottery ware. The instances are, however, rare, and are confined to the uppermost beds of the system. The products were, in the few instances noted, unusually fine, the clay working very smoothly and burning into cream-colored ware of great strength and excellence.

The occurrence of concretions in the shales of the Point Pleasant beds and in the lowest strata of the division found at Cincinnati, has already been noticed. The analysis of specimens from the river quarries suggests hydraulic cement, and they are in fact found to possess a high degree of hydraulic energy. The supply of these concretions depends upon the extent of the quarrying, but at the present rate several hundred tons are thrown out each year, and as the concretions prove nearly enough uniform in composition, they can certainly be turned to good, economical account in the manufacture of a fine quality of cement. The famous Roman cement of England is obtained from similar concretions, which are generally gathered on the shore after. storms and high tides, though sometimes obtained by digging. All of the river quarries from Point Pleasant to Lawrenceburgh, Indiana, yield these concretions - the lowermost beds of all most abundantly. It may be added that the limestones enclosing the concretions are silicious enough in composition to transfer them to the best of cements.

The Cincinnati section exhausts the scale of the county, the upper division of the blue limestone, as before stated, having never been found within its limits. The River Quarry beds do not constitute a marked feature, in any respect, of the geology of the county. There are but comparatively few points where these strata are exposed. A moderate amount of building stone of superior quality is taken from the Covington quarries, opposite Cincinnati. But little of the stone in this portion of the series can be burned into lime, but the concretions so abundant in many of the beds, as just hinted, constitute an hydraulic lime of great energy.

The second element of the Cincinnati section - the Middle or Eden: shales - is as much more prominent than the first in the county as its greater extent in the -vertical scale would lead us to infer. It is, however, mainly found in the slopes of the hills, as it is not firm enough in structure to resist denuding agencies, when unprotected by the higher series. Very few products of economical value, as we have seen, are derived from this part of the scale. Indeed, its relations to economical interests are mainly in the way of disadvantages to be overcome. These disadvantages result directly from the nature of the materials of which these beds are composed. It will be remembered that in the two hundred and fifty feet now under consideration, not more than one foot in ten is limestone; the remainder being soft shales, or soapstones, as they are variously designated. These shales have scarcely tenacity enough to hold their place in steep descents when acted on by water and ice; still less, when they have been removed from their original beds, can they be made to cohere; and they thus form treacherous foundations for buildings erected on them or for roadways constructed in them.

streets, and approaches, encounters these disadvantages, which can only be overcome by increased outlay in the way of foundations. These facts are most clearly shown in the approaches to the city from the east by the Ohio valley, frequent slides occurring along the steep slopes of shale in which streets and dwellings are involved. Gilbert avenue, in process of construction through Eden park, especially suffered from its geological formation, and required a large expenditure to give it stability along this line.

Nearly all the smaller streams that are bedded in these shales show contortions and flexures of their strata that have resulted from the slipping of the higher beds into the valleys.

The third division, viz., of the Hill Quarry series, which makes the upland of the county, is by far the most important of the three, in the area it covers and the products it furnishes. The summits of the insulated masses already named belong to this division, and constitute about three-fourths of the surface of the county. Most of the quarry stone of the county is also derived from this source. The Cincinnati quarries have thus far been vastly more important than those of any other district; but as the hills within and adjoining the city limits are being occupied for building sites, it will result that railroad transportation will be invoked; and when it comes to this, the more desirable building stone of the different formations from adjoining counties will come into competition and be more largely used.

Drift Deposits, Or Surface Geology

the classic ground in the way of fossils that it now is. The numerous and ample exposures gave to the earlier collectors unexampled opportunities - opportunities which are not likely to be repeated. Many of the most interesting localities of twenty to twenty-five years ago are now covered by permanent buildings, and every year diminishes the available areas. The waste of the hill quarries furnishes, however, by far the larger proportion of the admirable fossils in the vicinity of Cincinnati. Scarcely any exposure of it in the county has failed to yield choice forms of the various and rarer groups. DRIFT DEPOSITS, OR SURFACE GEOLOGY.

The drift formations of the county are mainly divided into two groups, corresponding to the main topographical features of the county already indicated, viz. :

I. - Drift deposits cover the highlands of Hamilton county, with but very limited exceptions. Towards the southern boundary these beds are light, measuring but a few feet (four to ten) in thickness; and, as already intimated, areas are occasionally found from which these deposits are altogether absent, the shallow coating of soil found in such areas being native or referable to the decomposition of the limestone that has been bedded here.

-high level drifts, and the distinction between them and the native soils, indeed, is not always very manifest. The presence of rounded pebbles of blue limestone and of northern rocks, the drift beds, tlough often but very sparingly distributed, is the best means of distinguishing these beds from the native soils. The drift clays are certainly derived in large part from the waste of blue limestone, effected in their case by glacial attrition; while the native soils have the same origin, except that the work of disintegration has been done in their case by the slow action of the atmosphere. The agreement between the drift soils of these southern counties and the native soils which are met here, is closer than is found between native and foreign soils in most sections of the State. This seems to be accounted for by the fact that a large area of the same formation lies north of them, which the glacial sheet was obliged to traverse and denude before striking upon this region. The blue limestone of these counties is thus largely covered with blue limestone waste.

The average thickness of these upland drift beds falls below twenty feet, but occasionally heavier sections are found. In the northern part of Sycamore township, in the vicinity of White Oak school-house, a high drift ridge occurs in which twenty feet of surface clays are underlain with a deposit 'of fine yellow moulding sand. This stratum, when filled with water, is a quicksand, and renders wells impossible, or at least very difficult to secure. the county, and boulders also are infrequent.

The yellow surface clays sometimes overlie a few feet of tough blue boulder clay, filled with scratched and striated pebbles, apparently the product of the melting glacial sheet. This is not, however, by any means a constant element in the section.

In short, the upland drift of this county is not as varied and interesting as that of the regions immediately to the northward, or even to the eastward. The slopes show the same characters in their drift beds that have already been described, except that the deposits are generally heavier.

IIl. - The second division, or the lowland driftbeds of the county are in their characteristic formations of much later date than the deposits already discussed. These deposits can be classified in their superficial aspects, under the principal divisions, viz: (a) The bottom lands; (b) the terraces or second bottoms.

These divisions are distinguished from each other, not only by their different elevations but also. by the different materials of which they are composed, the terraces being largely composed of gravel, with occasional beds of sand and clay, while the 'bottom lands contain, in all cases, a greater proportion of fine materials,

Of the upland drift no general or typical section was given, for the reason that, aside from the monotonous deposits of yellow clay, there is no uniformity in the order in which the different formations occur; but in the case of the division now under consideration, it is possible to represent in a single section the more important facts that are to be observed. The deposits of the Ohio valley, it

A section is here appended, taken at Lawrenceburgh, Indiana, which gives the general structure of the Ohio bottom lands more clearly than any exposure met. with, strictly within the limits of the county. Beginning at low-water, we find the deposits that make up the river bank arranged in the following order (ascending):

FEET 6. Brick clay, covered with one to two feet of soil.............- 6 5.) Land, pravel) anddoam.. tiie. stalet Oe tae gece ater 30 As HOCHWSOUS Say 4 da. beheld', «ted. cea Pa lace erate eon eerie 1% 3. Carbonaceous clay, an ancient soil or forest bed....,...,.... 7 PAN O)S oy 0) GME Ans bakes AN ABE pions casiiades ata JA Geno roses ere es De OVC," SRAVEL eines conchae eles Sie «ee arn ote RYOTE eters te = seactie San 6 Ot ad Wie wt hose Wys shane a rite, ey etree rae aaa Men cee etee te Sz The elements of this section will be noted in their order. The first of them, six feet of gravel, is perhaps the least constant of the series, being sometimes substituted by some of the clays of the drift. The gravel of the Ohio differs from that of the Miamis in being largely composed of sandstone pebbles instead of limestone. It is, consequently, less durable than the river or bank gravel of the Miami districts, and this fact, taken in con nection with the difficulty of access, withholds it generally from applications to road-making.

The second, third, and fourth elements need to be taken together, as they are closely connected in their history. The point to be noted in regard to them is the constant occurrence of carbonaceous clay between the seams of ochreous gravel. The clay is quite heavily charged with vegetable matter, much of it in such a state of preservation that it can be readily identified, and often portions again intermingled in a fine state of subdivision with the substance of the clay... The minutest roots of trees - some of the latter still in place - twigs and branehes, layers of leaves, ripened fruits, grapes, and sedges, are all clearly distinguishable. Several of the species of trees can be determined, some by their wood, others by their leaves and fruits. Among them may be named the sycamore, the beech, the shellbark hickory, the buckeye, and the red cedar. A cucurbitaceous plant, probably the wild balsam apple, is also shown to have been abundant by its seeds, which are preserved in the clay. : The leaves frequently occur in layers several inches thick, and are very like the accumulations that are now left in eddies of the river by freshets or floods. The deposits of the river at present always have an elevation of at least twenty feet and sometimes even of forty feet _ above the bed now under review.

The constant occurrence of vivianite or phosphate of iron in this deposit is to be noticed. Its presence, indeed, is 'an invariable characteristic. The mineral is - usually found in small grains, but sometimes it replaces twigs and leaves and other vegetable growths. The quantity in some portions of the beds is considerable, amounting, sometimes, to two or three per cent. of the whole deposit. In such cases it imparts its color to the mass, and this justifies the name by which it is known, "blue earth."

Several apparently trustworthy accounts have been received of the discovery of the bones and teeth of the mastodon and mammoth in this deposit; but these and all other mammalian remains are of very rare occurrence. It is possible that the "chips" and "axe-marked" stumps reported at various points in excavations in the drift beds, attest the former presence here of the gigantic beaver now extinct - castoroides Ohioensis. It was certainly a tenant of the State during the general period to which this old forest bed must:be referred. That its work upon trees might easily be mistaken for axe marks, will need no proof to any one acquainted with the work of the existing species of beaver.

In a few instances, land and fresh water shells have been found in the clay, sometimes in quantity enough to convert the clay into a shell marl.

This stratum is shown at all points along the valley in which bottom lands occur. Its elevation above lowwater varies from five to twenty feet. It is generally covered superficially with the waste of the overlying banks; but even in such cases it reveals its presence by the long lines of willows and other vegetable growths that establish themselves upon its outcrop. Two things conspire to adapt it especially to the growth of vegetation. In the first place, it is an impervious stratum, and turns out the water that descends through the "overlying loams and sandy clays, thus giving to willows and other plants of like requirements a constant supply of moisture; and secondly, this stratum, as has been already intimated,, is in reality an ancient soil, having been carried at an earlier day through the processes of amelioration by which beds of sand and clay are fitted to support vegetable growths.

There are, however, many places where the force of the current in high water uncovers these beds, and where consequently good sections are always offered. Excellent disclosures of them are found at New Richmond, Clermont county, and also at Point Pleasant, on the Kentucky shore. The spring flood of 1872 furnished an unsurpassed exhibition of this formation at the mouth of the Little Miami river. Rafts of tree trunks are shown at all of these points, though the wood generally perishes very quickly when éxposed to the air.

be referred to the agencies that are now at work in thevalley. When the trunks of trees and layers of leaves belonging to it have been noticed in the banks of the river, it has naturally enough been supposed that they are the deposits of earlier floods, agreeing as they do with the materials transported by the floods of ourown time. But in describing the Lawrenceburgh section, now under consideration, as the general section of the Ohio valley deposits, it has already been shown, at least by implication, that this explanation is inadmissible. The extension of this sheet of carbonaceous clay under all the various drift deposits of the valley, as is shown by very numerous natural and artificial sections, proves that it is of earlier date than these overlying deposits, and the character of this stratum shows that it has a very different history from that which these higher deposits record.

It is, perhaps, still too early to write out this history in its minuter features, but the facts already given show us that we have in this sheet of blackened clay the bottom lands of the Ohio at an earlier day, and, indeed, under very different conditions from those that now prevail. The river then ran in a channel lower by forty feet, at least, than that which it now holds, and the great valley was then empty of the immense accumulations of sand, clay, loam, and gravel, which constitute its bottom lands and terraces to-day.

The various vegetable growths with which this stratum is filled, are to be regarded as largely the production of the soil on which they are now found. There is no other satisfactory mode of accounting for the particular kinds and enormous amount of vegetable matter traced here.

The ochre seams above and below this ancient soil seem to point to marshy conditions that were brought in with the changing levels of the valley. Of the two, the upper seam is the more constant.

In the Lawrenceburgh section we find thirty-five feet (thirty to fifty in the general section) of sands, gravels, clays and loams, which constitute the Ohio bottoms, as the term is generally used. There is no fixed order in the alternation of these materials, except that the surface portions have, for a few feet in depth, a tolerably uniform character. The soil of the bottom lands is quite homogeneous in constitution, and has obviously been formed by the subjection to atmospheric agencies of just such material as it now covers. Beneath the soil, and extending to a depth of about fifteen feet, beds of yellow clay occur. The proportions of sand mixed with the ckty--vary somewhat, increasing towards the lower limit named, and below this the beds consist rather of sand than clay. The beds of clay above named furnish an excellent material for brickmaking. The supply of the Cincinnati market is almost entirely derived from this horizon. The great depth of these brick clays, and their entire freedom from pebbles, render a very economical manufacture of brick possible.

Below this limit, sand and gravel and streaks of loam are met, without regularity of arrangement. 'Of the fifteen to twenty feet intervening between the bottom of the brick clays and the summit of the buried soil, the larger part consists of gravel. The gravel of this horizon is seldom clean, like that described at the level of lowwater, but consists of large-sized sandstone pebbles, four to six inches in diameter, mingled with finer materials. _

An equivalent of these beds, but of local occurrence, is the fine-grained clay described in the geological reports as "Springfield clay." It never occurs in extensive sheets, but is quite limited in vertical and horizontal extent. The heaviest accumulation of it observed in Hamilton county is in the city of Cincinnati, on East Pearl street, above Pike. It has a thickness there of more than thirty feet, as has been ascertained in the excayations for the foundations of buildings. It has been turned to account in its different exposures for different purposes - at Miamisburgh, for the manufacture of paint; at Springfield, forthe manufacture of '' Milwaukee brick," the clay being rich in lime and poor in oxide, and thus burning white, while a new use has'been found for it in Cincinnati. It was successfully employed in preparing the floor of the new reservoir, its fineness of 'grain and consequent toughness fitting it admirably for this purpose. It must have been accumulated in eddies or protected areas, during the later ages of the period of submergence.

The gravel terraces occupy a higher level than the formations already described. The terrace on which Cincinnati stands, may be taken as a fair example of them all. Its altitude above low-water varies from one hundred to one hundred and twenty feet, the average \elevation being one hundred and eight feet. It is composed of distinctly stratified gravel and sand of varying degrees of fineness and purity. The gravel stones are all water-worn. In weight they seldom reach ten pounds. The upper tributaries of the Ohio supply the materials in part, but a much larger proportion in the vicinity of Cincinnati is derived from the limestone rocks of western Ohio and the crystalline beds of Canada. The proportion here to be noted among the smaller-sized pebbles is, of ten feet, five of Upper Silurian and Devonian limestones, three of Lower Silurian, least worn, one foot of granitic, and one of sandstones, etc., of the Upper Ohio.

Occasional seams of clay loam occur, but seldom of extent or tenacity enough to constitute reliable waterbearers. Less frequently~ met, but still constituting a noteworthy feature of the gravel terraces, are seams of bituminous coal, in small water-worn fragments.

The terraces overlie, as will be seen, the formation previously described. Few sections are carried deep enough to reveal the lower beds, but the leaves and wood of the buried soil are occasionally met at considerable depth, and usually, on this account, they attract attention. The following general order of materials will be observed in passing from the surface of the terrace to low-water.

The leading facts in the structure of the terraces show that their history is not to be explained by the present conditions of the continent. They must have been formed under water at a time when the face of the country held a lower level than it now does, by one hundred or more feet. They thus bear direct testimony to two of the most surprising conclusions which the study of the Drift period has furnished to us, viz: That the continent sank, during the latter stages of this period, considerably below its present level, and that it was afterwards re-elevated.

There is one other line of facts in connection with the drift beds of the county that must not be omitted here. It is the great depth which some of these deposits have been found to hold below the present drainage of the country. The series of facts obtained by Timothy Kirby, esq., in boring a deep well in Mill Creek valley, at Cumminsville, now within the corporate limits of Cincinnati, proves very interesting in this as well.as in other respects.

Beginning at an elevation of ninety feet above low-water of the Ohio, a succession of drift deposits was penetrated until a depth of sixty feet below low-water was reached, the bedded rock being first struck at a depth of one hundred and fifty-one feet below the point of beginning. The deposits included, in descending order, twelve feet of soil and brick clay, four of sand, thirty-four of blue clay with gravel, nineteen of gravel, three of coarse sand, eleven of sand with fragments of bituminous coal, nine of blue clay with gravel (at the bottom of this the level of low-water in the Ohio was reached), sixteen of blue clay and fine sand and sprinkled with coal, and forty-three of sand, water-worn gravel, and blue clay, with occasional fragments of bituminous coal, below which, at the depth of one hundred and fifty-one feet from the surface, were the shales of the Blue Limestone group. Several remarkable facts are to be observed in this section, the most striking of which is the great depth to which the excavation of Mill Creek valley was formerly carried. The bed of the stream that occupies the valley to-day is at a higher level by one hundred and twenty feet than that of the ancient channel. It is easy to see that this erosion could not have been effected under existing conditions. It can only be explained by a higher altitude of the continent, and is thus referred to the opening division of the glacial period. It has not been demonstrated that continuous channels exist at this great depth; but the rocky barriers that fringe the streams do not at best 'disprove this theory, as there is always room for a deeper channel on one side or the other of the great valleys.

Another interesting fact is the occurrence of waterworn fragments of bituminous coal, quite similar to those found in the terraces already noticed. They occur at various depths, the lowest at one hundred and fifty feet below the surface and the highest at.eighty feet below. These facts, so far as known, stand by themselves, and no explanation is proposed. It is hard to see how the waste of Ohio coal-fields should find its way in quantity into Mill Creek valley, and there is certainly no other obvious source of supply.

The well from which these facts were obtained was carried to a depth of five hundred and forty-one feet below the surface. Analysis of the chips and _ borings strata underlying Ohio to a depth greater by about four hundred feet than any other rocks exposed within the limits of the State. The shales of the blue limestone series appear to continue to a depth of four hundred feet from the point of beginning.

Carburetted hydrogen gas escaped from the well in considerable quantity from a depth of two hundred and eighty feet downwards, but no large accumulations of petroleum compounds were indicated.