ST. PETERS SANDSTONE. 289 



local details. A feature occurs in the north part of the township of Magnolia, of this 

 c -unty, deserving notice. A small stream, known as Allen's creek, flows westward 

 along the line separating sections 4, 5, and 6, on the north, from sections 7, 8 and 9, on the 

 south. On each side there is a range of bluffs capped with Trenton limestone and under- 

 laid with St. Peters sandstone. The junction of the two formations on the south side 

 is, by aneroid measurement, 155 feet above the stream, and on the opposite side, in sec- 

 tion 6, 32 feet, showing a difference of 123 feet. This superior elevation of the south 

 bluft'is maintained as far'to the east as the two can be compared. In section 7, about 

 midway between the two bluff's, there is a very sharp east and west ridge of hard sand- 

 stone, intersected in every direction by a network of silicious seams that stand out prom- 

 inently on the weathered surface, as though the rock had been extensively fractured and 

 subsequently reunited by silicious cement. This ridge rises 50 feet above the junction 

 of St. Peters and Trenton on the north side of the stream. These fact* are illustrated 

 by the accompanying figure. 



FIG. 37. 



SHOWING THE RELATIONS OF THE ST. PETERS SANDSTONE AND TBENTON LIMESTONE, MAGNOLIA. 



In this quiet region of gentle southeastward dips, these phenomena are unusual, 

 though insignicant in general geology. They are equally explainable by supposing a 

 flexure of the strata or a fault. 



At the railroad cut near Magnolia station, the transition from the St. Peters sand- 

 stone to the Trenton limestone is well shown. The main cut consists of the limestone, 

 the lower 3 or 4 feet of which are more or less sandy. Below this lies 8 inches of sandstone 

 containing seams and nodules of iron oxide and sulphide, doubtless all originally pyrites. 

 This layer of sandstone rests upon 4 feet 4 inches of impure sandy conglomeritic linie- 

 rock, full of Scolithus(?) tubes. Below this, continuing to the base of the exposure, is 

 an incoherent sandstone, mottled and banded with yellow, orange and green colors, and 

 exhibiting oblique and horizontal lamination. A similar transition may be seen at nu- 

 merous other points in Rock county. From this county onward, the general course of 

 the formation is due north for about sixty miles, and then east of north for more than 

 one hundred miles. Its irregularity of thickness in tracing it northward first becomes 

 pronounced in the western part of Dodge county, and it is first known to be entirely 

 cut off by the contact of the limestones, below and above, in the southern part of Green 

 Lake county, notwithstanding which, and frequent subsequent interruptions, it main- 

 tains an existence for more than 120 miles to the northward. It was last observed within 

 about four miles of the Michigan line, where it had a thickness of 20 feet. Beyond that 

 point it is concealed by the drift. 



The formation is not recognized at all in the recent geological report of Michigan, 

 although the foregoing facts offer a strong presumption that it exists there. Under the 

 impression that has formerly prevailed concerning the uniformity of this deposit, the 

 finding of the Trenton limestone on the Escanaba river, resting directly upon the Lower 

 Magnesian, would justify the inference that the St. Peters sandstone 'was essentially 

 wanting in the Upper Peninsula of Michigan, but with the light now possessed, the fact 

 of contact at that point has little significance in relation to the question of the presence 

 or absence of the formation in question. 

 Wis. SUR. 19 



