394 A. C. LANE 



In the second place it has not been much disturbed. It is too much 

 to say not at all disturbed, for there is caught in the synclinal fold 

 of Limestone Mountain on Keweenaw Point the Niagaran, so that 

 we are led to infer that notable disturbance took place along the line 

 of the Great Keweenaw fault after the Niagara. There are in the 

 Lower Peninsula also signs of shght foldings at various times. But 

 on the whole the strata lie in one vast little-disturbed persistent basin, 

 Schuchert's Ontario Traverse Basin, in a gentle embayment of the 

 great pre-Cambrian boss or shield which curves around them from 

 Wisconsin on the west to Canada on the east. It is possible that at 

 the center of this basin Paleozoic deposition was continuous, perhaps 

 not always marine. 



A notable feature is the general fineness of the sediments and 

 absence of conglomerates. These latter are extremely rare. If one 

 overlooks some perhaps autoclastic limestone calcirudites, occasional 

 pebbles of quartz as big as peanuts and in the Marshall a few narrow 

 thin bands of conglomerate containing very little but quartz, he may 

 say there are none. The wide variety of crystalline and igneous 

 rocks which lie only a short distance northeast to northwest are 

 practically absent until, of course, we come to the glacial till, where 

 they are abundant. These facts seem strong grounds for believing 

 that during all the Paleozoic time this great area was neither glaciated 

 nor violently disturbed and uplifted. We ought to have therefore in 

 the Michigan section an ideal place, where the strata are well exposed, 

 to study those universal advances and retreats of the shore-line which 

 must have occurred as the ocean level was raised the world over 

 by filling-in of sediments, or lowered by falling-in of blocks of the 

 ocean floor. It is likely that we can recognize already the broad 

 outlines of Huntington's steady and more unsteady periods as follows: 



Relatively Steady Relatively Unsteady 



Jurassic and Cretaceous Tertiary and Quaternary 



Upper Mississippian Permo-Carboniferous and Triassic (New Red) 



Middle Devonian Upper Devonian (Old Red) 



Niagaran Lower Devonian and Late Silurian 



Trenton-Utica Upper Ordovician Lorraine to Clinton 



(Ozarkian ?) Calciferous ? St. Peter sandstone minor 



Early Cambrian and Keweenawan 



Animikie black slate Palms and Goodrich 



Kona dolomite and Possibly an oscillation below Keewatin 



Grenville limestone 



