THE BARITE DEPOSITS OF MISSOURI 45 



Joints 



Massive, bedded, sedimentary rocks, such as the dolomites 

 and Hmestones of this region, are well adapted to exhibiting 

 joints, but the limited exposures give little opportunity to ob- 

 serve them. 



There does not appear to be a definite direction along which 

 the majority of the joints strike. They range from north and 

 south to N. 70° W. Practically all the strikes of the major 

 joints that were determined were in this zone. Most of the 

 minor joints are at approximately right angles to the major 

 joints. In one locality triangular blocks were produced by three 

 sets of joints, one striking nearly east and west, and the other 

 two at about 45° to the first. 



The strike of the barite veins is only in small part con- 

 cordant with that of the joints. Very large veins were closely 

 associated with these prevalent directions of the joints, but the 

 barite veins were very irregular in direction. 



GEOLOGICAL HISTORY 



Since the base of the Elvins formation is not exposed in this 

 area it cannot be stated whether it is conformable with the for- 

 mation (Bonneterre) immediately below. The lower part of the 

 formation was deposited in a shallow sea at some distance from 

 the shore because it contains some intraformational conglomer- 

 ates and sandy dolomite. The sand grains in the sandy dolomites 

 are well rounded and rather uniformly scattered thru the 

 crystalline dolomite, showing that materials had not been per- 

 fectly sorted when deposited in the dolomite. The shale is inter- 

 bedded with the dolomite. Dolomite beds that are shaly are rare. 

 As carbonate rocks predominte, either the land which furnished 

 the materials must have been low or the Elvins formation of this 

 locality was deposited some distance off shore. That the last 

 may have been the case is indicated by the fact that the lower 

 part of the Elvins, 25 miles to the southeast, contains a large 

 amount of shale. It is probable that the land, Ozarkia, to the 

 south was also low-lying, for a great dolomite formation had 

 been deposited in that region in the preceding epoch. The pres- 

 ence of so many intraformational conglomerates in this part of 



