232 THE MAEQUETTE lEON-BEARIXG DISTRICT. 



INTERESTING LOOAI-ITIES. 



Mud Lake. — Noith ()f Mud Lake, adjacent to the old road east and west 

 of N.-S. i line, sec. 29, T. 48 N., R. 25 W. (Atlas Sheet XXXVI), is a con- 

 glomerate, described by Irving^ as the "State Road conglomerate." This 

 conglomerate occurs at various points for a distance of a quarter of a mile 

 east and west, hanging upon the southern flank of the prominent ridge of 

 Mona schist running east and west througli this and adjacent sections. The 

 basal portion of the conglomerate is very coarse. Tlie fragments contained 

 in it comprise Ijoth granite and green schist. The granite fragments vary 

 from small pel)l)les to bowlders 2 feet or more in diameter. They are well 

 rounded, and in lithological character are similar to the granites which 

 occur as intrusives in the northern part of the ]Mona-schist belt. While 

 these granite fragments are abundant, green-schist fragments are still more 

 plentiful. In size they vary from small particles to large blocks. Some of 

 them are distinctly rounded, but many are angular, being in shape similar 

 to the irregular schistose blocks which at the present time are broken by 

 weathering agencies from the main mass of ]\Iona schist. Search was 

 made for jasper pebbles, such as occur in the conglomerate to the east, but 

 without success. All who have examined this conglomerate agree that it 

 is a basal one, being made up largely from the formations immediately 

 subjacent, but containing a sufficient amount of material somewhat remote 

 from the contact to show that it can not be a dynamic conglomerate. This 

 belt of conglomerate is only a few feet in width, and nearly all of the 

 localities are just north of the old State road. 



Immediately south of this road occur most interesting exposures of 

 interstratified slate and graywacke. The rock varies from a very fine 

 grained slate to a coarse graywacke, the denser phases of which are red 

 and felsitic-looking. Certain exposures are wholly of the graywacke, others 

 of the slate, and others are interstratifications of the two. The most altered 

 phases take on a schistose structure, and are difficult in hand specimen to 

 discriminate from a crystalline schist. This rock is found to have a cleavage 



' The greenstone-scliist areas of the Menominee and Marquette regions of Michigan, by G. H. 

 Williams, with an introduction l)y R. D. Irving: Bull. U. S. Geol. Survey No. 62, 1890, p. 21. 



