The history of Columbia County, Wisconsin, containing an account of its settlement, growth, development and resources; an extensive and minute sketch of its cities, towns and villages--their improvements, industries, manufactories, churches, schools and societies; its war record, biographical sketches, portraits of prominent men and early settlers; the whole preceded by a history of Wisconsin, statistics of the state, and an abstract of its laws and constitution and of the constitution of the United States
Chamberlin, T. C.
Topography and geology, pp. -120 PDF (5.3 MB)
TOPOGRAPHY AND GEOLOGY. there seem to have been extensive calcareous sand flats and areas over which fine calcareous mud settled, the former resulting in a pure granular dolomite, the latter in a compact close-textured stone. The rock of the reefs is of very irregular structure. Of other portions of the formation, some are coarse heavy beds, some fine, even-bedded, close-grained layers, and.some, again, irregu- lar, impure and cherty. All are highly magnesian, and some are among the purest dolomites known. The Niagara limestone occupies a broad belt lying adjacent to Lake Michigan. LOWER HELDERBERG LIMESTONE. On Mud creek, near Milwaukee, there is found a thin-bedded slaty limestone, that is believed to represent this period. It has neglected, howe.ver, to leave us an unequivocal record of its history, as fossils are extremely rare, and its stratigraphical relations and lithographical character are capable of more than one interpretation. Near the village of Waubeka in Ozaukee county, there is a similar formation, somewhat more fossiliferous, that seems to repre- sent the same period. The area which these occupy is very small and they play a most insignifi- cant part in the geology of the state. They close the record of the Silurian age in Wisconsin. During its progress the land had been gradually emerging from the ocean and increasing its amplitude by concentric belts of limestone, sandstone and shale. There had-been no general disturbance, only those slight oscillations which changed the nature of the forming rock and facilitated deposition. At its close the waters retired from the borders of the state, and an interval supervened, during which no additions are known to have been made to its substructure. DEVONIAN AGE. HAMILTON CEMENT ROCK. After a lapse of time, during which the uppermost Silurian and the lowest Devonian strata, as found elsewhere, were formed, the waters again advanced slightly upon the eastern margin of the state and deposited a magnesian limestone mingled with silicious and almuninous material, forming a combination of which a portion has recently been shown to possess hydraulic properties of a high degree of excellence. With this deposition there dawned a new era in the life-history of Wisconsin. While multitudes of protozoans, radiates, mollusks and articulates swarmed in the previous seas, no trace of a vertebrate has been found. The Hamil-ton period witnessed the introduction of the highest type of the animal kingdom into the Wisconsin series. But even then only the lowest class was represented-the fishes. The lower orders of life, as before, were present, but the species were of the less ancient Devonian type. Precisely how far the deposit originally extended is not now known, as it has undoubtedly been much reduced by the eroding agencies that have acted upon it. That portion which remains, occupies a limited area on the lake shore immediately north of Milwaukee, extending inland half a dozen miles. The cement rock proper is found on the Milwaukee river just above the city. At the close of the Hamilton period the oceanic waters retired, and, if they ever subsequently encroached upon our territory, they have left us no permanent record of their intrusion. The history of the formation of the substructure of the state was, it will be observed, in an unusual degree, simple and progressive. Starting with a firm core of most ancient crystalline rocks, leaf upon leaf of stony strata were piled around it, adding belt after belt to the margin of the growing island until it extended itself far beyond the limits of our state, and coalesced with the forming continent. --An ideal map of the state would show the Archoean nucleus surrounded by concentric bands of the later formations in the order of their deposition. But during all the 119
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