54:8 GEOLOGY OF CENTRAL WISCONSIN. 



Peters standstone, and Trenton limestone. On the southern side of 

 Dane county the Lower Magnesian sinks to the level of the Catfish 

 valley, spreading over a considerable area in the towns of Rutland, 

 Dunn, Pleasant Springs and Dunkirk. The numerous narrow steep- 

 sided valleys, tributary to the valley of Sugar river, in Primrose, 

 Springdale and Cross Plains, and the valley of Sugar river itself in 

 Verona and Montrose, cut down to the upper surface of the Lower 

 Magnesian, which thus forms narrow strips along their bottoms. 



Along the edge of the main area, in Columbia county, and north- 

 western Dane, and usually not more than two or three miles west or 

 north from it, though occasionally more than this, are many small 

 isolated bluffs crowned by the Lower Magnesian. These vary in area 

 from a few acres to three or four square miles. North of the Wis- 

 consin river and along the west side of Sank county, as far as the 

 southern side of the Baraboo valley, the Lower Magnesian, in areas 

 of varying size, occupies all the higher ground, the country being 

 characterized by numerous narrow ridges, with intervening narrow 

 valleys. North of the Baraboo, in northwestern Sauk county and 

 southwestern Juneau, the Lower Magnesian occurs only in rare and 

 very small cappings on the highest ground. 



The topographical characters of the regions occupied by the 

 Lower Magnesian differ much, according as they occur within or 

 without the drift-bearing area, and also according to whether the 



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formation exists on the higher grounds only, or has sunk down to the 

 lowest levels. All of these regions, however, are alike in possessing 

 a most excellent soil, the Lower Magnesian area including the best 

 agricultural land in the district. In Columbia county the formation 

 occupies a region which is for the most part very fertile, high, rolling 

 prairie, the prairie areas forming a nearly continuous belt from the 

 towns of .Scott and Randolph, in Columbia county, southwestward to 

 Middleton, in Dane county. This high belt breaks down suddenly to 

 the westward, but the escarpment, though quite bold, is without the 

 great cliff-like exposures so characteristic of the Lower Magnesian as 

 it appears along the lower Wisconsin and upper Mississippi rivers. 

 The same is true of the sides of the limestone ridges about the heads 

 of the Cattish river. Along the Wisconsin, however, below Sauk 

 City, the Lower Magnesian crowns the river bluffs often with bold 

 cliffs, the difference being chiefly due to the absence of drift materials. 

 Along the western side of Sauk county, the drift is also absent, and 

 the usual abrupt, ridgy topography of the driftless regions is every- 

 where apparent, the limestone capping to the ridges being often a mero 

 crest of rock, large fallen masses from which dot the side-hills below. 



