USA > Iowa > Chickasaw County > History of Chickasaw and Howard counties, Iowa, Volume I > Part 5
USA > Iowa > Howard County > History of Chickasaw and Howard counties, Iowa, Volume I > Part 5
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Another region of unusual topography embraced in the Iowan area, occurs north of the road leading through the middle of sections 22, 23 and 24, Forest City Township. This locality is within a short distance of the Iowan margin. Both drifts here are thin, and numerous stony knobs or low tors project above the general surface. The land is hilly as compared with the ordinary Iowan plain, and furnishes another example of topography controlled by preglacial erosion of the indurated rocks.
DRAINAGE
The drainage of Howard County follows courses which were determined to a large extent in preglacial time. In places the ancient valleys were only partially filled with drift. In other places they may have been completely filled, but the settling of the loose detritus gave rise to depressions along which the later streams established themselves. The Upper Iowa, or Oneota River, is the most important stream in the county; it has its rise in the Iowan drift plain of Mower County, Minn., enters Howard near the northeast corner of Oak Dale Town- ship, takes an unusual course for Iowa streams, nearly due east, and follows a valley characterized by entrenched meanders which are best developed east of the Iowan boundary at Foreston. All the northern townships of Howard County are drained by the Upper Iowa. The tributaries of this stream are, however, few and unimportant. In Albion Township, where the valley is cut deeply into the rocks, the river is fed by numerous springs which represent rather shallow under- ground drainage. The sources of the Turkey River are found in the ill drained depressions of the Iowan plain in Howard Center and Paris townships. There are no well defined drainage channels about the headwaters of the several branches of this stream. The run-off simply follows the broad, shallow sags which were left in the surface by the melting ice of the lowan glaciers. Below Vernon Springs the valley of the Turkey takes on preglacial characteristics similar to those seen in the Upper Iowa Valley in Albion Township. The more typical Iowan area which occupies the southwestern half of the county, is drained by Crane Creek and the branches of the Wapsipinicon. Nearly all of the streams of this area have their origin within the limits of the county, and they are practically branchless, so far as development of definite tributary channels is concerned. Broad "sloughs," in place of eroded creek beds, serve to collect the waters from the adjacent slopes. While the drainage courses seem to have been determined by position of preglacial valleys, the streams of the southwestern part of Howard County have accomplished very little in the way of erosion. They have neither valleys nor flooded plains in the ordinary sense. They run in simple shallow trenches cut only a few feet below the level of the surface on which they began to flow after the withdrawal of the Iowan ice.
STRATIGRAPHY
GENERAL DESCRIPTION
The geological formations exposed in Howard County are not very numerous. The Ordovician and Devonian systems are represented in the indurated rocks,
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CHICKASAW AND HOWARD COUNTIES
and two divisions of the Glacial series-the Kansan and the Iowan-are recogniz- able in the surficial or Pleistocene deposits. The country rock is completely hidden from view by deep accumulations of glacial drift, over approximately nine-tenths of the area of the county. There are a few points, principally in the northeastern townships, where the rock comes to the surface in the general uplands, but it is along stream courses that exposures chiefly occur. The best natural sections are seen in the valley of the Upper lowa or Oneota, in the Loess-Kansan area east of Foreston. Sections of seventy-five or eighty feet in height occur in sheer cliffs at a few points along the river, and others of less range are not uncommon. There are also some satisfactory sections along the Turkey River, east of Vernon Springs. In other parts of the county rock exposures are few in number, of very limited range, and usually far apart, and so the correlation of the outcrops and the ar- rangement of them in a definite section are matters of great difficulty. This difficulty, so far as concerns the Devonian, is heightened by the fact that the beds have been altered by dolomitization. In the process of alteration the fossils were reduced to imperfect casts or were entirely obliterated, and so the aid that paleon- tology might render in correlating outcrops is not always available.
The overlap of the Devonian on the Maquoketa is one of the remarkable features of the stratigraphy of this part of Iowa. The Niagara limestone, which elsewhere intervenes between the formations named, is here absent, and both the Devonian and the Maquoketa of the region differ lithologically from outcrops of corresponding age at the localities where the formations are typically developed and have been most carefully studied. The Devonian is so largely dolomitic that some portions of it resemble certain phases of the Niagara. The Maquoketa is more calcareous than at the well known outcrops in Dubuque County ; some of it is even dolomitic and might be mistaken for the Galena limestone, while other parts are more like the non-dolomitized Trenton. The phase of the Devonian which rests on the Maquoketa is not the lowest Devonian of other parts of Iowa, but it is made up of beds carrying Productella Subalata Hall, and Spirifer pennatus Owen, fossils which indicate a horizon near the top of the Wapsipinicon stage. The relations of the strata suggest that, on account of local subsidence after the beginning of the Devonian, the shore line was slowly carried eastward during the time represented by the Coggan, Otis, Independence and Lower Davenport beds, as these are described by Norton in the reports on Linn and Scott counties. The greatest eastward extension of the Devonian sea occurred during the Upper Davenport age, when beds containing the fauna represented by Productella subalata and Spirifer pennatus were laid directly upon Maquoketa or Hudson River deposits containing Leptaena unicostata, Plectambonites sericea, Orthis tes- tudinaria and Orthis kankakensis.
The study of the Niagara limestone in counties southeast of the area we are considering-in Fayette, Delaware and Buchanan-shows a decided tendency on the part of this formation to become thinner toward the northwest. It may be possible, therefore, that no Niagara was ever deposited as far north as Howard County. On the other hand there is a possibility that the Niagara is present in its proper position underneath the later deposits, some distance west of the over- lapping edge of the Devonian. Owing to the dolomitization of both formations the Devonian and the Niagara. in the northern part of the state, cannot be differenti- ated in the ordinary borings from wells; but the combined thickness of the beds
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CHICKASAW AND HOWARD COUNTIES
above the Maquoketa in wells begun in Devonian limestones at Waverly, Sumner, Frederika and Osage, is so small as to indicate the actual thinning and practical disappearance of the Niagara in this direction.
The following table shows the stratigraphic relations of the geological forma- tions recognized in Howard County :
GROUP
SYSTEM
SERIES
STAGE
Recent.
Alluvial.
Cenozoic.
Pleistocene.
Iowan.
Glacial.
Kansan.
Devonian.
Middle Devonian.
Wapsipinicon.
Paleozoic.
Maquoketa.
Ordovician.
Trenton.
Galena-Trenton.
ORDOVICIAN SYSTEM
GALENA-TRENTON
The Galena-Trenton is the lowest of the geological formations exposed in Howard County. It is seen in various exposures along the river valley in Albion Township, from Florenceville eastward. A short distance above Florenceville the Trenton disappears beneath the level of the bottom of the valley, passing under thin-bedded, calcareous shales and shaly limestones belonging to the stage of the Lower Maquoketa. There is a general discussion of the Galena-Trenton in the chapter on the Geology of Dubuque County, in volume X of the series of State reports. In that discussion it is shown that the dolomitic phase of the formation, which has been called the Galena limestone, is a local characteristic which is best developed in Dubuque County and' becomes less and less marked toward the north, and that non-dolomitized beds in the northern counties, which are the exact equivalent of dolomitized Galena, have usually been referred to as Trenton limestone. Certain persistent life zones were recognized in the Dubuque County report, among which the zone of Receptaculites oweni, and a zone con- taining a number of species of large gastropods are among the most prominent.6 The place of the Receptaculites zone is about sixty feet below the top of the formation, and the gastropod zone lies a few feet lower.
In Howard County it is the upper part of the Galena-Trenton, beginning a short distance below the gastropod zone, that is represented in the cliffs along the Upper Iowa River. Rising vertically from the water at a number of points on the stream in the east half of section 12. Albion Township. are sheer precipices of Trenton limestone, sixty to eighty feet in height ; and from twelve to fifteen feet above the base of the scarps the characteristic species of the gastropod zone occur.
" Iowa Geol. Surv., Vol. X. p. 409, and Nos. 8 and 9, Plate 4, opposite p. 410. Des Moines, 1900.
Cedar Valley.
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CHICKASAW AND HOWARD COUNTIES
The rock is gray or drab in color. rather fine-grained, somewhat magnesian but not dolomitic. It lies mostly in thin beds, though some layers near the foot of the exposed sections are eighteen inches in thickness. The fine cliffs in the northeast quarter of the southeast quarter of section 12, show at their base the lowest beds of the formation to be seen within the county. There are somewhat similar cliffs in the northeast quarter of the southeast quarter of section II. The gastropod zone is here at the foot of the precipice, and Receptaculites occurs about twenty feet above the level of the water. The face of the cliff is seventy feet in height, and the height above low water in the stream is about eighty feet. To the right of the cliff is the mouth of a small, steep ravine in which the successive beds may be studied more successfully than in the cliff itself. The stone is rather fine grained and grayish toward the base, but about the middle of the section it occurs in heavier, coarser layers which are more magnesian, and in their general character- istics show a closer approximation to the Galena type of the formation. Judging from the position of the Receptaculites zone, the top of the cliff should correspond very nearly with the top of the Galena-Trenton, and this view is supported by facts observed on the receding hill side a little higher up. For some distance back from the brow of the cliff the ground rises in a gentle slope which is covered with glacial material of Kansan age, but at an altitude of twenty feet above the base of the slope there are some beds of fine-grained, calcareous shales belonging to the Maquoketa. Fifteen feet higher there are beds of more typical Maquoketa with Leptaena unicostata and Plectambonites sericca.
The upper portion of the Galena-Trenton is exposed at the mill at Florence- ville. Just below the mill the stone has been quarried to some extent. It shows the following section : .
Feet
2. Irregularly bedded, fine-grained, fossiliferous limestone with shaly partings ; some of the layers represented by detached nodules and irregular lenticular slabs of limestone embed- ded in shale IO
I. Regularly bedded stone in layers a foot or more in thickness, without shaly partings, rather coarse-grained, beds cut by definite joints, joint faces pitted and roughened by weath- ering 8
No. I of this section furnishes a durable building stone well suited for use in the rough, substantial grades of masonry. The rock is quite magnesian, semi- crystalline, but is not a true dolomite. This member is the equivalent of the coarser beds observed above the middle of the cliff in section II. Excepting some stem segments of crinoids, no fossils were seen in it at this point. A short distance above Florenceville, a few rods north of the old mill in Granger, Minn., there is an exposure of beds equivalent to No. 2 of the foregoing section ; while less than one hundred yards farther north, the heavy quarry beds of No. I are seen in place. A large Orthoceras, the Cameroceras proteiforme Hall, occurs in the quarry beds. The shaly partings of the overlying beds-the equivalents of No. 2-furnish quite a number of fossil species, among which were noted a small species of Prasopora, Lingula philomela, Plectambonites sericca represented
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CHICKASAW AND HOWARD COUNTIES
by a number of very small individuals, Leptaena charlottae and Orthis testudinaria. The upper part of the Granger exposure is not represented at Florenceville. It is more shaly than the lower, and some of the thin beds of limestone furnish small specimens of Rafinesquina alternata Conrad, and Isotelus iowensis Owen. The great amount of shale alternating with thin, sometimes nodular, beds of limestone indicates that the conditions at the close of the Galena- Trenton in this locality were similar in one respect at least to those which marked the close of the same stage in Dubuque County. The diminished thickness of the calcareous layers and the increased thickness of the shaly partings near the top of the Galena-Trenton are noted at page 430 and elsewhere in volume X of the State reports.
The Galena-Trenton was not seen in Howard County at any points outside of the immediate valley of the Upper Iowa, or Oneota River. There is, however, a very interesting outcrop a rod or two east of the county line, opposite the southeast corner of section 13, Albion Township. The point in question is in the valley of Nichols Creek and the river is in fact less than one-fourth mile away. The interest attaching to this exposure arises from the fact that the beds exhibit perfectly the characteristics of the Galena limestone. They are buff, granular, vesicular, crystalline, dolomitic, massive, ranging up to six feet in thickness. The characteristics are unusual in this part of the state and help to emphasize the fact that dolomitization has no formational significance but may be a purely local phenomenon of very limited extent.
MAQUOKETA OR HUDSON RIVER
The transition from the Galena-Trenton to the Maquoketa in Howard County is not as abrupt as it is in Dubuque. There are here shales alternating with thin beds of limestone in the upper part of the Galena-Trenton, and soft clay shales alternate with thin indurated layers of calcareo-magnesian shale, at the base of the Maquoketa. Some of the beds of harder shale in the Maquoketa would rank as argillaceous limestone. The lithological differences between the top of the Trenton and the base of the Maquoketa are simply differences in the characteristics of the more indurated beds. In the Maquoketa the stony layers are lighter colored, softer, more granular, much more earthy and argillaceous than those of the upper part of the Galena-Trenton. The calcareo-magnesian beds of the Maquoketa, however, are counted of sufficient value to be quarried for building stone, one of the quarries so operated being located on the north side of the river in the southwest quarter of section 8, Albion Township. The river flows north through the western part of the northeast quarter of section 9. less than half a mile west of Florenceville, and on the east side of the stream rises a vertical cliff of more or less indurated shales of the Maquoketa stage. sixty to seventy feet in height. This is the best single section of the formation in the county. Cliffs showing beds of the same type, but diminishing in height as the formation is traced up the stream, occur at intervals almost to Foreston. In the western part of section 7. Albion Township, and the eastern part of 12. Forest City Township, the river flows between bluffs in which the Maquoketa beds rise in vertical exposures to a height of forty feet above the water. The upper parts of the bluffs in this locality are everywhere composed of Devonian
Vol. 1-4
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CHICKASAW AND HOWARD COUNTIES
dolomite. The Maquoketa finally disappears beneath Devonian, in the bottom of the river valley, one-half mile east of Foreston.
The general characteristics of the Maquoketa or Hudson River formation, as seen in the valley above Florenceville, are well illustrated at the quarry in the north bank of the stream in the northeast quarter of section 8. The beds that are sought for building stone rarely exceed four inches in thickness. The intervening seams of shale are equally as thick. All the beds yield readily to the weather, and the cliff face breaks down rapidly. All the surfaces which have been exposed to the air for any length of time are bleached to a light gray. Fossils are not very common. It is true that some of the beds are crowded with the comminuted stipes of graptolites in such condition that neither genera nor species can be recognized. Occasionally, however, there are perfect indi- viduals which indicate the presence of such common Hudson River types as Diplograptus pristis, Diplograptus putillus and Diplograptus quadrimucronatus. The second species is included on the authority of the "Geology of Minnesota," volume III, Part 1, page 82. Other fossil forms occurring sparingly are Plectam- bonites sericea, small forms of Rafinesquina alternata, Orthis testudinaria, Iso- telus gigas and the rather short and broad trilobite with rounded cephalon and pygidium which Clarke has described in the "Geology of Minnesota," volume III, Part II, as Isotelus susae.7
Distribution. The distribution of the Maquoketa or Hudson River deposits is not limited, as is the case with the Galena-Trenton, to the walls of the imme- diate valley of the Upper Iowa River. A broad tongue of Maquoketa crosses the county line from Winneshiek, in sections 13, 24 and 25, and extends up the valley of Nichols Creek and its tributaries to near the west line of section 22. There is another tongue of Maquoketa, but smaller than the preceding, projecting into sections 12 and 13, Vernon Springs Township. The Maquoketa comes very near the county, if it does not quite enter it, in the valley of the Turkey River. At the bridge over this stream on the county line there are exposures of the Productella beds of the Devonian, and the Devonian is continued down to the level of the water; but less than one-half mile east of the county line the Maquokęta rises fifteen or twenty feet above the bottom of the river channel, and so it is fairly probable that the formation would be found beneath the water in the
7 The Isotelus susac Whitfield species, Geology of Wisconsin, Vol. IV, p. 236, is a very different form from the one referred by Clarke to this species. It is a smaller, more convex, thicker in front than posteriorly, with the anterior part of the head deflected so that near the front margin the surface of the glabella stands nearly at right angles to the general plane of the body-characteristics correctly shown in Whitfield's Figure 8, Plate 10. The eyes are more prominent, the visual surface is larger than in the species figured and described by Clarke, and the posterior limb of the glabella is much narrower in proportion to its length. In the collections of the University at Iowa City, there are three specimens of Whitfield's and Calvin's Asaphus (Isotelus) susac, from the Florenceville region, but they are all from the upper part of the Galena-Trenton. So far the species has not been found in. the Maquoketa or Hudson River shales. In the same collections there are three specimens of the very different form referred to Isotelus susae in Volume III of the Minnesota Survey, which are from outcrops of the Maquoketa shales on the river above Florenceville. If this broad, short, flat species of trilobite, so well figured and described by Clarke in the Geology of Minnesota, Vol. III, Part II, p. 708, requires a distinctive name, it may be called Isotelus florencevillensis in honor of the small village near which it is found.
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CHICKASAW AND HOWARD COUNTIES
stream and the soils in the bottom of the valley, in sections 1 and 12, New Oregon Township.
Typical Exposures. The lower part of the Maquoketa in Howard County, for a thickness of about sixty feet, is composed of the thin, indurated, calcareo- magnesian beds with alternating shaly partings, illustrated at the quarry in section 8, Albion Township. Near the top the formation varies greatly, and the char- acteristics of the same horizon are quite different in different localities. The details of the upper part of the formation are best studied outside the limits of Howard, in Winneshiek County, for the reason that the greater number of exposures found here afford better opportunities for observation. For example, a section embracing the upper forty feet of the formation is seen along the south line of section 16, Lincoln Township, in Winneshiek. In part the rock of this section is a magnesian shale, and in part it is a crystalline dolomite resembling the Galena limestone at Dubuque. The fossils recognized here are Lingula, a fragment too imperfect to be identified specifically, Leptacna unicostata, Plectam- bonites sericea, Orthis testudinaria and Orthis kankakensis. The locality is especially interesting for the reason that the ground rises gradually toward the east, and near the southeast corner of the section named there are dolomitized beds containing Devonian types of Stropheodonta, Productella, Atrypa and Spir- ifer. The locality is especially interesting as showing very clearly the absence of the Niagara limestone and the superposition of the Devonian on the Maquoketa.
Along the county line road, on the east side of section 13, Vernon Springs Township, the hill slope leading from the south into the valley of Silver Creek shows, at the top, the Productella beds of the Devonian, beneath which there are light yellow magnesian shales and harder layers of granular dolomite belong- ing to the Maquoketa. The shaly magnesian beds begin, in descending the hill, between twenty-five and thirty feet above the level of the small valley. Diligent search failed to reveal any fossils in them, but their relations to other recogniz- able horizons in the Maquoketa leave little doubt that they represent the transition beds at the top of the formation, described in the reports on the counties of Delaware and Dubuque. On the north side of Silver Creek the Devonian, with its usual Productellas and Spirifers, begins not more than ten feet above the floor of the valley, and there is no trace of the light colored magnesian Maquo- keta. Here are indications of an unconformity. The creek valley widens rapidly in Winneshiek County, and in its floor and sides are many interesting exposures of Maquoketa, some of which are within a few feet of overlying Devonian. A short distance east of the southwest corner of section 16, New Oregon Town- ship, there is an outcrop of non-dolomitized limestone crowded with Plectambo- nites sericea and other Ordovician species. This outcrop recalls the crowded fossiliferous slabs of limestone so common everywhere in the upper part of the Maquoketa, a few feet below the transition beds, in Dubuque County. Thin layers of limestone similarly charged with the common Plectambonites occur at various points in sections 13, 14. 23, 24 and 25. Albion Township. An outcrop of upper Maquoketa along the north line of the northeast quarter of section 8 has numerous individuals of Streptelasma corniculum associated with the Plectambonites. The most interesting assemblage of fossils occurs in what are practically the very uppermost beds of the Maquoketa, on the east line of the southeast quarter of section 25. At this point there are the magnesian transition
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CHICKASAW AND HOWARD COUNTIES
beds noted in section 13, Vernon Springs Township, but associated with them are some non-dolomitic layers rich in well preserved fossils which are identical in form, size and general expression with corresponding species from the Cin- cinnati shales of Ohio and Indiana. The Cincinnati types here include robust forms of Rhynchotrema capar, Rafinesquina alternata and the varietal form, R. nasuta. There are other species, such as Orthis testudinaria and Pleciambo- nites sericea, which do not vary in many other exposures in Iowa from the forms occurring in the Cincinnati shales. The fossil bearing layers are pure limestone, some of them being completely crinoidal.
Correlation and Thickness. The Maquoketa formation is much thinner in Howard County than it is in Dubuque. The lower indurated beds with numerous graptolites, exposed in the river valley above Florenceville, may be correlated with the hard, slaty, graptolite-bearing shales which make up the Lower Maquoketa in Dubuque County. The heavy body of plastic shales which compose the greater part of the Upper Maquoketa in the Dubuque County report, seems to be absent from Howard County, the upper member of the formation being represented only by the calcareous, fossiliferous layers and the magnesian transition beds which lie above the plastic clays farther south. The whole thickness of the Maquoketa does not here exceed 100 feet, while in Dubuque County the thickness is fully twice as great.
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