98 LOWER PENINSULA. 



I have now given a description of the observations which I was 

 enabled to make on the surface distribution and structure of the 

 Waverly group, from an examination of the different natural out- 

 crops, and from the results communicated to me of different deep 

 borings made in all parts of the State, and will proceed to 

 briefly recapitulate the principal facts derived from such investiga- 

 tion. 



The Waverly group seems to be spread in a basin-like sheet over 

 all the peninsula, with exception of the country north of the river sys- 

 tems of Au Sable River, on the east side, and of Manistee River, on 

 the west side, besides a triangular area in the southeast corner of the 

 State, which is occupied by the Helderberg group and by the 

 black shales, as may be seen by a glance at the geological map 

 connected with this report. This basin-shaped rock series is, in 

 the centre of the peninsula, overlaid by the coal measures and by 

 the subcarboniferous limestone, but is everywhere there within 

 the reach of deep borings. 



The essential constituents of the formation are sand rock and 

 shales, with subordinate admixture of calcareous or ferruginous 

 layers or nodular concretions. It is a shore deposit. All shore 

 deposits are composed of coarse materials, carried there from 

 the neighboring continental surfaces ; their nature depends upon 

 the nature of the surface material of those continents, and the de- 

 position of the sediments under the changeable wave action on an 

 ocean shore is necessarily more irregular than that which takes 

 place in the deep water remote from the shore. 



The stratification often becomes discordant, and frequent 

 changes in the material are induced by local influences ; while in 

 one place a shale bed forms, in another near by a sand-rock 

 ledge may be accumulated. This fact is noticed in every shore 

 deposit, recent or old. A comparison of the strata in differ- 

 ent outcrops of the Waverly group will for these reasons rarely 

 allow of an identification of certain beds, and often not even of 

 their exact horizon in the series. Still greater must be the dis- 

 crepancy in the results of boring experiments, where direct obser- 

 vation of the rock beds is excluded, and we have to depend on the 

 examination of comminuted fragments ; and what makes the case 

 worse yet, is that these fragments can rarely be examined by the 

 scientific observer himself — he has to depend on the statements 



