46 



STRUCTURAL GEOLOGY OF NORTH AMERICA 



LAKE 



MICHIGAN 



^^ LLE OUTG$", 



MILES 



slightly folded over the anticline, it is possible that some movement 

 occurred after they were deposited as well as during the time of de- 

 position. 



At the beginning of the Pennsylvanian there was a regional southwest 

 slope furrowed by numerous subparallel valleys as deep as 200 feet. An 

 eastward slope prevailed along the western border of the basin with 



Fig. 5.9 Structure contour map of Eastern Interior basin. Contours on Illinois Coal No. 2, in 

 hundreds of feet. After Wanless, 1955. Oak. A., Oakland anticline; M-S Syn., Marshall-Sidell 

 syncline; D.M., Duquoin monocline; R.C.F., Roush Creek fault zone. 



Fig. 5.10. Cross section of the Illinois basin, after American Association of Petroleum Geologists 

 1954, Geo/ogic Cross Section of Paleozoic Rocks, central Mississippi to northern Michigan. The 

 Eau Claire and older beds of the Cambrian are sandstone and shaly sandstone; from the upper 

 part of the Eau Claire through the Ordovician, Silurian, Devonian, and the Mississippian to the 

 Upper Mississippian Chester series the sequence is dominantly limestone and dolomite with much 

 chert. The St. Peter is conspicuous sandstone in the Ordovician, and the Osage of the Mississippian 

 has considerable sandstone and shale toward the La Salle anticlinal belt. The Chester and Penn- 

 sylvanian strata are sandstone and shale with several thin limestone beds, and coal in the 

 Pennsylvania. 



