USA > Iowa > Chickasaw County > History of Chickasaw and Howard counties, Iowa, Volume I > Part 2
USA > Iowa > Howard County > History of Chickasaw and Howard counties, Iowa, Volume I > Part 2
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southeast corner of section 9, Fredericksburg Township, the contrast between the low plain and the billowy upland is very strikingly illustrated. A score or more of similar examples might be given. There are, for instance, a few sections of rolling Iowan in the northeastern part of Bradford Township and contiguous parts of Chickasaw. The northwestern and western parts of Rich- land Township are comparatively level, but the surface breaks into rolling swells along Calamus Creek, while a third phase of the Iowan topography is illustrated in the broad, flat bottom land, partly undrained, which borders the Wapsipinicon River a little farther east in the same township. The rather feebly developed hilly characteristics of the rolling Iowan are still further exem- plified in the southeastern corner of Jacksonville Township and the adjacent parts of New Hampton. But these may suffice for concrete illustrations of a type of topography easily recognized and quite widely distributed. The hills in such areas are not high, the surface slopes are comparatively gentle, the topog- raphy has not been developed by erosion since the Iowan drift was deposited, neither can it be claimed that it is simply a modification of a pre-Iowan surface. Like the more level plains into which this type merges, it is a product of con- structive agencies, of ice moulding.
In some parts of the county the pre-Iowan topography is but imperfectly concealed by the later drift. An area of this kind makes up the long slope between Devon and the Little Wapsipinicon River at North Washington. There was here deposited only a very meager amount of Iowan drift; the rain-cut gullies by the roadside reveal the leached and oxidized Kansan till and the ferrugi- nous Kansan gravels within a few inches of the grass roots; the undulations of the surface are much stronger than in typical Iowan areas; the hills and trenches of the old eroded Kansan are clearly expressed in the modern topog- raphy. Another interesting bit of erosional pre-Iowan topography is seen along the line which separates sections 20 and 29 in Bradford Township, on the east side of the Cedar River, opposite Nashua. A rather deep ravine with short lateral gulches, preglacial as to age, is cut in the Devonian limestones. Over part of this area all drift is absent, the rock coming practically to the surface. On both sides of the Cedar River, from the point where this stream enters Bradford Township to where it leaves the county near Pearl Rock, there is a general absence of drift of any age, the Devonian limestones crop out on the slopes and hill tops in numerous places, the hills and ravines, with reliefs of fully eighty feet, are a product of preglacial erosion working on the indurated rocks. In the angle between the Cedar River and the Little Cedar, near Brad- ford. there is a high steep-sided promontory not drift-covered, a conspicuous illustration of some of the characteristics of the preglacial topography. On the west side of the Little Cedar River, between Bradford and Bassett, there is very little Iowan drift; there are places where there is practically no drift of any kind: the topography is of the older erosional type. A region of sandy and partially loess-covered hills sixty to eighty feet in height, well carved by surface drainage, occurs in sections 16, 17, 20 and 21. Chickasaw Township. There are deep trenches of recent erosion along the roadsides, and there are some rain-cut scars and gulches in the fields : but in general the topography is old, older than the Iowan stage of glaciation. In the northeastern part of the Town of Bassett there is a prominent knob-like hill which is the south end of
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a narrow ridge jutting out from the upland Iowan plain and encroaching upon the low, broad valley of the Little Cedar River. The bluffs bordering the river valley rise to the same general level. The whole surface of the region-bottom lands, bluff slopes and upland plains-is sprinkled with Iowan bowlders. The Iowan ice was here, but the amount of detritus it carried was insufficient to affect in any notable degree the relative altitudes of the pre-Iowan bluffs and low lands.
In a region as level and monotonous as is Chickasaw County in general, the shallow stream valleys become marked features of the topography. Over most of the county these valleys are simply broad concave sags in the general surface ; but the valley of the Cedar throughout its short course in Chickasaw, and the valley of the Little Cedar from above Bassett to its confluence with the larger stream, are evidently old, rock-cut preglacial trenches bounded by bluffs and hills rising to heights of eighty feet or more. Very little of the material from any of the drift sheets covering the adjacent parts of the country found per- manent lodgment in these valleys. Between the Town of Chickasaw and Nashua the broad bottom lands through which the Little Cedar flows are underlain by a heavy body of the valley phase of the Buchanan gravels, showing that the valley was as wide and deep as it is today at the time of the melting of the Kansan ice. There has been no filling and re-excavation of these valleys since pre-Kansan time. Some ox-bow lakes or abandoned meanders in sections 4 and 9. Bradford Township, practically at the present level of the river, indicate that there has been no deepening of the valley in very recent periods. Above and below Jerico, in sections 28, 31 and 33 in the northern part of Jacksonville Township (township 97 north, range 12 west). Crane Creek flows in a broad, ill-drained bottom land which is set off from the drier upland by an imperfectly defined terrace slope. The terrace is composed of valley gravels of the Buchanan stage. In this region there has been some erosion of the gravels in the long inter- vals since their deposition, deepening the valley in which the stream meanders, probably to the extent of eight or ten feet. There is a small amount of rock cutting in the valley of the Little Turkey River, beginning one-half mile above Little Turkey Postoffice and continuing at intervals to where the stream leaves the county. . This feature is most marked a short distance east of the center of section 25 in the southern part of Utica Township.
In other parts of the county, as already indicated, the streams flow in broad, shallow sags in the drift and do not differ from the ordinary valleys of the Iowan plain. A number of branches of the Wapsipinicon converge in the southern part of Dayton Township, and hence there is here an unusually large area of low, flat land, some of it showing ponds, and all of it imperfect surface drainage. There are here, however, as usual along all the streams, extensive valley trains of Buchanan gravel, and these afford perfect underdrainage to quite a large part of the area, and render its cultivation possible even in the wettest of seasons.
DRAINAGE
The great number of streams traversing the county from northwest to south- east and dividing the surface into a correspondingly large number of long, nar-
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row inter-stream areas, has been previously noticed. The Cedar and the Little Cedar drain the southwestern part of the county; the wide central belt extend- ing from the northwest to southeast is effectively drained by the numerous branches of the Wapsipinicon; while Crane Creek and the Little Turkey River carry off the surplus waters from the northeastern area. All the main drainage courses, as is clearly indicated by the general presence of accompanying valley trains of Buchanan gravel, were outlined as early as the melting stage of the Kansan ice; while the deep, rock-cut valleys of the Cedar and the Little Cedar were partially or wholly developed in preglacial time
Altitudes .- The following table, showing the relations of a number of the more important points in the county to sea level, is compiled from Gannett's "Dictionary of Altitudes":
Feet
Alta Vista
1,155
Devon
1,194
New Hampton
1,155
Fredericksburg
1,075
Nashua
981
Lawler
1,078
Bassett
1,017
An examination of the table reveals the interesting fact that though the direction of the streams is toward the southeast, the general slope of the county is toward the southwest. Fredericksburg, located in the valley of a branch of the Wapsipinicon, is ninety-four feet higher than Nashua, almost directly west of it in the valley of the Cedar; and Lawler, in the valley of Crane Creek, is sixty-one feet higher than Bassett, which is in the same latitude in the valley of the Little Cedar. The high points, Devon and New Hampton, are located on one of the long, narrow dividing ridges.
This general slope of the surface toward the southwest is not peculiar to Chickasaw County, it is characteristic of the major part of all Northeastern Iowa. The country rises toward the northeast until the high points within a few miles of the Mississippi River, such as Iron Hill, near Waukon, attain an altitude of 1,300 feet above the sea. This anomalous behavior of the streams in flowing, not with the slope, but at right angles to it, was years ago pointed out by McGee in his "Pleistocene History of Northern Iowa." 5
STRATIGRAPHY
SYNOPSIS
The geological formations exposed in Chickasaw County are few in number. They are limited to two systems, the Devonian and the Pleistocene. The indu- rated rocks may all be referred to the Cedar Valley stage of the Middle Devonian series ; the surficial clays and soils accessible to observation belong almost exclu-
5 Eleventh Ann. Rept., U. S. Geol. Surv., pp. 363-365.
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sively to the Kansan and Iowan stages of the Glacial series. The pre-Kansan drift exists, without much doubt, in its proper place at the base of the Pleistocene deposits, but its presence is not positively known. It is justly inferred, however, from the fact that a forest bed is encountered, interstratified with glacial deposits, in drilling deep farm wells in various parts of the county.
The stratigraphic relations of the formations which are open to direct investi- gation in Chickasaw County may be conveniently indicated in tabular form as follows :
GROUP
SYSTEM
SERIES
STAGE
Iowan.
Cenozoic.
Pleistocene.
Glacial.
Kansan.
Paleozoic.
Devonian.
Middle Devonian.
Cedar Valley.
DEVONIAN SYSTEM
General Discussion. So far as known, the Devonian limestones underlie the Pleistocene deposits over the entire region now under consideration. Chickasaw County, however, is so generally and so completely covered with glacial drift that rock exposures, are very few in number and very widely scattered. There is one very obscure outcrop of Devonian limestone on Crane Creek, and two or three, somewhat more satisfactory, occur on the Little Turkey River in the southeastern part of Utica Township. All the other outcrops are in the western part of the county, and the most important of these are confined to the valleys of the Cedar and Little Cedar rivers. In seven townships out of the twelve there is not a single exposure of native rocks in place, and over almost the whole area of the remaining five, the surface is fertile prairie with the native Devonian beds concealed by deep deposits of drift.
The strata exposed in the county range from the horizon of Gypidula comis and Spirifer pennatus, the equivalent of the quarry beds at Independence, to the horizon of the yellow, magnesian limestones which lie above the Acervularia and Stromatopora zones and form the uppermost members of the Devonian sections in Buchanan and Howard counties. The beds are more or less mag- nesian throughout the entire section, and some parts of the section are so com- pletely dolomitized as to resemble certain phases of the Niagara limestone in the counties of Delaware and Dubuque. The resemblance to the Niagara is heightened when, as occurs in a quarry nearly opposite the mill at the Town of Chickasaw, the heavy, dolomitized beds include great numbers of chert nodules and are separated one from the other by thick bands of chert. In nearly all the exposures of the Devonian in this county the limestone is soft, carthy, granular and non-crystalline, and vug-like cavities lined with calcite are common. In quarrying some of the beds, the lining of calcite becomes detached from the wall
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of the cavity in which it was deposited and furnishes an example for a thin-walled, calcareous geode.
Typical Exposures. Gypidula comis Beds, the lowest beds recognized in the county, are seen in the east bluff of the stream, a few rods above the wagon bridge at Chickasaw. There is a section of twenty-five feet here exposed. The rock is a heavy bedded dolomite which is much broken up toward the surface on account of weathering. Lower down the beds are intersected by numerous joints. A large amount of chert in streaks and bands-the chert sometimes included in the layers, in some cases occurring as partings between them-is a striking feature of this section, and one very unusual in the Devonian. Litho- logically and otherwise the rocks resemble very closely many exposures of the Niagara in Delaware. Jones and Dubuque counties. At first sight it seemed scarcely possible that such rocks could belong anywhere except in the Niagara ; but, while fossils are absent from most of the beds and are scarce in all of them, it was found that the lower edge, about three feet in thickness, contained many perfect casts of Gypidula comis Owen, and Spirifer pennatus Owen. These species establish the Devonian age of the beds beyond question and make it possible to correlate them with the beds in the City quarry and the lower part of the O'Toole quarry at Independence. The differences, however, in the char- acter of the stone and in the firmness and thickness of the individual layers at the two points, Chickasaw and Independence, are surprisingly great. The beds described above crop out at intervals for some distance along the bluff, above and below the quarry, and they have been cut through by a deep ravine which traverses the southeast quarter of section 16, a short distance north of the quarry.
On the west side of the river, about a mile above the bridge at Chickasaw, beds of about the same horizon as those in the Chickasaw quarry are exposed in a ravine, near the level of the water in the stream, not far from the middle of the north line of the southwest quarter of section 16. Quite an amount of building stone has been taken out at this point and the locality is known as the Huffman quarry. The stone is magnesian, but is not so perfectly dolomitized as at Chickasaw. The layers are thinner and the fossils, instead of occurring as mere casts, have the shells preserved. The finely striated Independence type of Atrypa reticularis is common, and there are some specimens of Spirifer pennatus, a form always associated with the preceding at the typical outcrops in Buchanan County.
Atrypa occidentalis Beds. Beds a little higher in the geologic column than those described in the preceding paragraphs are seen in the old Bishop quarry in the northeast quarter of section 16, Chickasaw Township. The stone, as usual in this part of Iowa, is highly magnesian and lies in thin, even layers which may be quarried in flagstone-like pieces two to six inches in thickness. There are numerous cavities lined with calcite, and some very perfect and sym- metrical calcareous geodes may be obtained as a result of the separation of the calcite lining from the walls of the cavities. The fossils are of the types found toward the upper part of the quarries at Independence, and include along with Atrypa reticularis and Spirifer pennatus, such forms as Orthis iowensis and Hall's occidental variety of Atrypa aspera. The beds are cut by oblique, parallel
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CHICKASAW AND HOWARD COUNTIES
joints, and along the joints the fossils are often well exposed by solution and removal of the matrix.
Acervularia profunda Beds. This zone occurs at the top of the Bishop quarry, as it does in most of the quarries at Independence, overlying the Atrypa and Spirifer pennatus zones. Besides the typical species, Acervularia profunda, this zone contains Cystiphyllum americanum, Favosites alpenensis, Cladopora prolifera and a number of the coarse stromatoporoids which are associated . with these species at the same geological horizon at Littleton in Buchanan County. Here, as at Littleton, the A. profunda shows a conspicuous tendency to inde- pendent growth of the corallites. The quarry exposes a section twenty feet in thickness. The upper 21/2 feet are occupied by the Acervularia zone, which in places is crowded with the corals and stromatoporoids mentioned. Some of the stromatoporoids, weathered to show perfectly concentric, laminated structure, are more than a foot in diameter.
The beds immediately below the Acervularia and stromatoporoid horizon are quarried and burned for lime in the Town of Chickasaw, at a point thirty- five feet higher than the base of the quarry in the river bluff near the mill. The Acervularia zone is included in the stripping. The corals are large and coarse. Stromatoporoids are most common : but Acervularia, Cystiphyllum, Zaphrentis, Cyanthophyllum, and a form that is probably Craspedophyllum are also present. The corals are all more or less silicified, and the entire zone is useless for lime burning.
The Acervularia horizon, noted above, is indicated in the pits made for the foundations of the new railway bridge at Nashua. Among other species rec- ognized in the loose materials thrown out in making the excavations were Acervularia profunda, Stropheodonta demissa and Orthis jowensis. Below the Greenwood mill, one mile northeast of Nashua, loose fragments of rock evidently washed out of the river bed by the plunge of water over the dam, contained a number of stromatoporoids besides Acervularia profunda, Craspedophyllum strictum, Atrypa reticularis, A. aspera, and other types belonging to the horizon of the quarries at Chickasaw. The beds which at Chickasaw are at least thirty- five feet above the river, are at Nashua and Greenwood mills below the level of the water. The slope of the valley, ascertained by comparing the altitude of Nashua with that of Bassett, is about 41/2 feet to the mile. From Chickasaw to Nashua the fall should be about twenty-seven feet. Between these two points the Acervularia zone has descended from at least thirty-five feet above, to five feet below the level of the water, making a total dip to the strata of about eleven feet to the mile.
Spirifer parryanus Beds. Above the mill dam at Nashua there are exposures in the right bank of the Cedar River showing a section twenty-five feet in thick- ness. The layers are not all well exposed, but so far as they could be observed they are soft, earthy dolomite. The lower part of the section is quite barren of fossils, but twenty feet above the level of the water there are a few layers rich in casts of Spirifer parryanus Hall. At Littleton, Iowa, the S. parryanus horizon is not more than five or six feet above the Acervularia profunda beds ; at Nashua the two horizons are separated by more than twenty feet of compara- tively barren strata. While in the river bluff at Nashua the fossils appear only as casts, there is evidence that non-dolomitized beds of this horizon must outerop
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somewhere in the neighborhood. In making a small culvert in one of the streets of the city, slabs of a comparatively pure limestone were used, in which the crowded shells of Spirifer parryanus are perfectly preserved. Information as to where the stone came from could not be obtained ; but great variations in the lithological characteristics of any given stratum, within very short distances, are by no means unusual. The S. parryanus beds descend to the level of the water at Pearl Rock, three miles south of Nashua, the dip south of the city being essentially the same as that from the north, eleven or twelve feet to the mile.
Idiostroma Beds. In a ravine a short distance north and west of the Thomas schoolhouse, in the southeast quarter of section 30, Bradford Township, there are two parallel ridges or reefs of the coarse-stemmed Idiostroma which occurs from ten to fifteen feet above the Spirifer parryanus horizon in Johnson County. These reefs are curiously local affairs. Each one is only thirty or forty feet in width, thickened in the middle and thinning out at the edges. They are about twenty yards apart, and their trend is northwest-southeast. They are underlain and overlain by soft, earthy dolomite, the overlying beds arching over the ridges, dipping in between them, and coming on each side in contact with the underlying beds. They seem to be simply elongated lenses of reef material with no very great extension in any direction. On the west side of the ravine, a little below the point where the reefs occur, there is a good section which includes both the underlying and the overlying beds, but it shows no trace whatever of the Idiostroma material." The whole body of the reefs has been altered more or less to a very hard, light-colored, siliceous dolomite, very different in texture, color and composition from the soft, granular beds prevailing in this vicinity. The surface of the tangled mass of Idiostroma stems is covered in places with a thin coating of quartz, and in the more compact portions of the mass, minute quartz crystals line the surface of cavities from which fossils have been dis- solved. In addition to the Idiostroma, which is the common and typical fossil, there are occasional specimens of Acervularia davidsoni. A Favosites, probably F. alpenensis, occurs more frequently. Eumophalus cyclostomus Hall, a form always associated with Idiostroma in Johnson County, and a slender Orthoceras six or eight inches long, are among the other observed fossils. The great altera- tions which the reef material has undergone, has made specific identification of the unsatisfactory casts by which fossils are mainly represented, in some cases practically impossible. While these local ridges of Idiostroma and associated fossils are in their proper stratigraphic relations to the other known life zones of the Devonian, it is quite evident that this particular area was never occupied by a living Idiostroma reef such as once covered the region now known as Johnson County. Such reef material does not appear anywhere else in Chicka- saw County, although there are many sections, some, as noted above. within even a few rods of the locality described, which embrace strata from geologic levels both above and below the reef horizon. At present there is no known point nearer than the northern part of Johnson County where this peculiar stromato- poroid on a reef-making scale flourished in place. The very limited extent of the Idiostroma lenses, their relations to the regular sediments of the region, and their lithological differences from the local strata, all suggest that the relatively small amount of material they represent was brought here from probably long distance by some marine agent of transportation.
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CHICKASAW AND HOWARD COUNTIES
Lithographic Beds. At Iowa City there are beds of fine-grained, light-gray lithographic limestone beginning a few feet above the Idiostroma horizon. Sim- ilar beds have been noted in this volume above the equivalent of the Acervularia davidsoni zone in Howard County. They occur in the same geological position at numerous other points in Iowa. They are present on the hill tops about Nashua in Chickasaw County. There are no sections in this county that show the lithographic beds well, but some weathered ledges in place and numerous loose fragments may be seen on the high points in the roads leading north and south from Nashua.
Intermediate Beds. To horizons somewhere between the Spirifer parryanus and the lithographic beds should be referred the exposures in the northern half of Deerfield Township. The entire absence of fossils here makes exact correla- tions difficult, but the lithological resemblance of the beds to the thin layers in the upper part of the Croft quarry at Elma, in Howard County, coupled with the fact that the Deerfield exposures are distant from Elma only a few miles, would justify the reference of these beds to the horizon of the upper part of the Elma quarries, or to one slightly higher. As a matter of fact, beds cor- responding to those in the upper part of the Elma quarries have been worked four miles southwest of Elma, within less than two miles of some of the expos- ures in Deerfield Township, Chickasaw County. By reference to the Howard County report it will be noted that the Spirifer parryanus zone is present in the bottom of the Croft quarry, and hence the beds in question lie between this zone and the horizon of the lithographic limestone.
In the southeast quarter of section 3, Deerfield Township (township 96 north, range 14 west), on land belonging to Edward Brown, stone has been quarried somewhat extensively to meet the local demands. The beds are thin, yellowish, argillaceous, and without fossils. Toward the bottom of the quarry the bedding is quite irregular, and below the bottom as it appears at present, from a pit now filled with mud, there were formerly quarried a few ledges of hard limestone, six to eight inches in thickness. There are here two openings a short distance apart. In both there is quite a strong dip toward the southwest. In the one farthest east the following section may be made out :
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