NORTHWEST OF LAKE SUPERIOR. 



341 



SECTION II. 



LOCAL DETAILS OF THE SECTIONS MADE IN THE RANGES NORTH OF LAKE SUPERIOR. 



1. Mission Creek. — The sections already given of St. Louis and Black Rivers,* 

 show the junction of the sandstone series with the underlying argillaceous and sili- 

 ceous slates, upon which it rests unconformably. As these sections afford a key to 

 much of the geology of the country, it is thought best to give another section, of 

 the unaltered rocks near Fond du Lac, before proceeding to describe them in the 

 more disturbed portions of the District, where they are associated with, and their 

 relations obscured by, the numerous dikes and beds of trap found between Fond 

 du Lac and Pigeon River. 



Mission Creek is a small stream, which drains a portion of the country lying in 

 the southern bend of St. Louis River, between the west end of Lake Superior and 

 Grand Portage. It empties into the St. Louis at the village of Fond du Lac. The 

 valley through which it runs before reaching the plain on which the village is 

 situated, is deep and narrow, and bounded on the east side by the commencement 

 of the high greenstone ridges which trend to the northeast, and on the west by 

 deposits of drift, marl, and clay, such as overlie the sandstones, conglomerates, and 

 slates of St. Louis River. 



About three-fourths of a mile above the mouth of the creek, sandstone shows 

 itself in the east bank of the creek, on the flank of the greenstone ridge, overlaid 

 by marl and clay-beclsf (1), just as they occur on the St. Louis River. Between 

 forty and fifty feet above the water-level, the marl contains beds of pebbles, from 

 eighteen inches to two feet thick, and in the upper part and on the surface, nume- 

 rous large boulders occur. 



The first exposure of sandstone (2) is about thirty feet in thickness, and dips 

 southeast, at an angle of 10°. It is micaceous, and disposed to be shaly. Some of 

 the beds are reddish gray, and others red, with marks of cross lamination. About 

 two hundred yards further, red shale (3) comes up, eighteen feet thick, and con- 

 taining bands of hard sand-rock, from four to eight inches in thickness. The bands 

 are from eighteen inches to five feet apart. These shales are of a dark-red colour, 

 but become bluish red on the planes of stratification, when exposed to the weather. 

 In some places they look very much like indurated clay, but are gritty. The clip 

 here is 20° southeast. Three hundred yards higher up the creek, the shale is 

 underlaid by fifty-five feet of sandstone (4), in strata from six inches to four feet 

 thick ; and a short distance further on, the sandstone rests on twenty feet of thin, 

 shaly rock (5) . The upper part of the sandstone is reddish yellow, and resembles 

 the thicker strata of St. Louis River. The lower part of the shales are bluish- 

 coloured. They rest on a gray, pebbly, coarse grit (6), five or six feet thick, and 



* See section (PI. 2 N, Sect. 2), from the valley of St. Croix River, near the mouth of Upper Pinnette 

 River, northerly, to Rainy Lake. 



f See section on Mission Creek. (PI. 2 N, Sect. 1.) 



