GEOLOGICAL EXPLORATIONS AND LITERATURE— 1841. 9 



sandstone with similar relations to the granite all alon<^ the south coast 

 of the lake from this point as far west as the east side of Keweenaw Bay. 

 Like Schoolcraft, he regards it as probably the "Old Red." The granite 

 and certain greenstones associated with it are cut by "veins of hornblende," 

 which, however, never pass upward into the sandstone. 



1841. 



Houghton, Doitglass. Fourth annual report of the State Geologist, 

 Douglass Houghton. State of Michigan, House of Representatives, No. 27. 

 Reprinted in " IMemoirs of Douglass Houghton, first State Geologist of Michigan," 

 by Alvah Bradish. Detroit, 1SS9. 302 pages. 



The first general statements made with respect to the relations of the 

 Lake Superior rocks to one another are to be found in the reports of Dr. 

 Houghton, first State geologist of Michigan. The fourth report, j)ublished 

 in 1841, deals principally with the geology of the copper region, although 

 the general geological relations of the different portit)ns of the Lake Superior 

 region to one another are discussed, and the boundaries of the present 

 Marquette district are outlined. The presence of "Primary" and "Meta- 

 morphic" rocks in the vicinity of the present city of Marquette was known 

 to the author, though he refers to this locality only in a general way as 

 the region north of the Chocolate River. At Presque Isle, moreover, he 

 recognized the presence of a serpentinous trap rock, which lie thought had 

 been raised up through the sandstones now ly"^» ^H'^n it, for the oi-iginal 

 horizontal stratification of the sedimentary rock has been so disturbed that 

 its strata now dij) a, way from the trap in all directions. At the junction of 

 the two rocks the sandstone has been shattered and impregnated with 

 calcareous matter, and both rocks have lost their characteristic features 

 (j)p. 180-181).^ 



The main features of the geology of the Upper Peninsula of Michigan 

 are here for the first time a})proximately outlined. The primary rocks are 

 reported as extending northwestward from Little Presque Isle, a small point 

 jutting into Lake Superior, a little southeast from River des Morts, now 

 known as Dead River. Along the lake shore they are known as far west 



' All references by page number iu this review are to the report as reprinted in the Memoir of 

 Douglass Houghton. 



