26o E. C. CASE AND W. I. ROBINSON 



occasional streaks of a very fine conglomerate or a very coarse 

 sandstone. On Big Limestone and Little Limestone the pebbles 

 of the conglomerate are of quartz and about the size of a pea; near 

 Sherman Hill the pebbles are larger and there is much chert and 

 greenstone. No fossils were found in this layer. It has been referred 

 by Lane to the Jacobsville Sandstone, probably of Potsdam age. 



The hills are broken in a very intricate manner by minor faults 

 of comparatively recent age. They are, in many cases at least, due 

 to under cutting of the dolomite and to slumping. There are 

 some major faults, notably the one between Big and Little Lime- 

 stone, which involve the sandstone below. Unfortunately the data 

 available do not serve to determine the age of the great Keween- 

 awan fault; the most that we can say is that there was serious dis- 

 turbance of the region at least as late as after mid-Devonian time. 



The most important point brought out by this study is the 

 demonstration that the paleozoic seas of the times mentioned above 

 extended well into, if not over, the Northern Peninsula of Michigan, 

 and our paleogeographic maps must be so far altered as to include 

 that region within the areas of deposition. Dr. Ulrich has called 

 attention to the similarity which exists between the Pentameroid 

 forms of Big Limestone and those of the Far West indicating a 

 broad extension of the Niagaran sea in that direction. 



In conclusion the senior author desires to state that most of the 

 field work and the determination of the fossils was done by the 

 junior author and that to him in a large measure is due the credit for 

 the recognition of the extension of the paleozoic sea over the 

 Northern Peninsula of Michigan. 



