THE BARITE DEPOSITS OF MISSOURI 19 



tals are hosts to numerous crystals of dolomite. These beds do 

 not contain much glauconite or sand. 



The dolomites are in beds ranging from an inch up to sev- 

 eral feet in thickness. Some parts are very thin-bedded and 

 shaly, while others are massive and weather into large angular 

 and rounded blocks. The conglomerate layers are distinctly len- 

 ticular, as are also many of the dolomite and shale beds. Ripple 

 marks were found on all the beds comprising this lower, or 

 Davis, member. Most of them are two or three inches across. 

 Buckley** reports that some of the beds contain sun cracks. 



Fossils are not abundant, as a rule, but a bed was found in 

 which cystoid stems were numerous. Some distance above this 

 bed a thin platy dolomite contains an abundance of lingulas. 

 Buckley (ibid., p. 38) reports that trilobites are also found in 

 some of the beds, but none were seen in the rocks of this area. 

 The so-called fucoids are found rather abundantly in the dolo- 

 mites. They are frequently of large size ; several inches long and 

 nearly an inch across. 



The shales are little exposed, but those seen were blue to 

 bluish-gray and very thin-bedded. They are only slightly cal- 

 careous, except along certain layers which contain fucoids. All 

 the shales contain some magnesium carbonate. They are in beds 

 four to five feet thick interbedded with the dolomite. They were 

 not observed in association with the sandy dolomites. They 

 weather to thin plates of a yellow color. One bed broke down 

 to an ash-gray soil. 



The sandy dolomites are found in the lower part of the sec- 

 tion, except in the southeastern part of the area, where the upper 

 dolomite beds of the Elvins formation contain thin lenticular lay- 

 ers of sandy dolomite. The color varies from yellowish-red to 

 greenish-red. Texturally, they are medium to fine-grained, 

 the latter predominating. They consist essentially of dolomite, 

 glauconite, quartz and clay. There is an abundance of dark 

 green grains of glauconite in these beds. Under the microscope 

 the glauconite grains are seen to be round, while the associated 

 grains of sand (less than 15 per cent of the rock), are angular to 

 subangular. The glauconite in thin section is pale green. The 



'Buckley, E. R., Mo. Bur. of Geol. and Mines, vol. 9, Pt. 1, p. 38. 1908. 



