340 SYDNEY H. BALL 



filled partially by an in-washing of the surrounding soils, and par- 

 tially by the caving-in of walls of the sink-holes and caves due to 

 sapping by differential solution. 



The unconformity between the Mississippian and Pennsylvanian 

 is widespread throughout Missouri.^ On the north slope of the 

 Ozarks the unconformity is shown by (i) basal conglomerates, (2) 

 discordance of bedding, and (3) general field relations, the Saline 

 Creek cave-conglomerate being deposited on both the Burhngton 

 limestone and the Cambro-Silurian formations. 



Deposition oj the Coal-Measure shales. — The deposition of the 

 Saline Creek cave-conglomerate continued until the region subsided 

 practically to sea-level. Then began the deposition of the Coal- 

 Measure shales. Clay washed into those depressions not filled by 

 the Saline Creek cave-conglomerate. At times muck with a small 

 clastic content was deposited, later to consolidate into cannel coal. 

 The sink-holes clogged up with clay became fit sites for swamps. 

 Coal beds 30-40 feet thick resulted (McClure Prospect 32 feet, 

 Knowall 35 feet). Locally the sea encroached on the land, and 

 argillaceous, fossiliferous limestones were deposited. That the 

 basins of deposition were very local is shown by the dissimilarity of 

 the rocks of neighboring Coal-Measure basins and the impossibility 

 of correlating individual strata. 



At the Republic Mine the following is a section from the under- 

 lying Jefferson City (Cambro-Silurian) formation up: 



28 feet bituminous coal and shale interlaminated. 



I Prodiictus semireticulatus. 



10 feet argillaceous limestone, fossiliferous 



4 feet more or less calcareous shale. 

 4 feet variegated chert, fossiliferous. 



Productus cor a. 

 Spirifer earner atus. 

 [^Spirifer rockymontanus . 



At the William Shelton Prospect, three miles away, the succession 

 up from the same formation is: 



50 feet shale, grading into 

 40 feet cannel coal. 



Many equally striking cases might be cited. 



I Missouri Geological Survey, Vol. VII, p. 438. 



