A. Winslow — Cambrian in Missouri. 221 



Art. XXVII. — Notes on the Cambrian in Missouri and the 

 Classification of the OzarJc Series ; by Abthur Winslow. 



Introductory Remarks. — The Magnesian or Ozark series of 

 rocks in Missouri covers nearly the entire southeastern quarter 

 of the State. The members consist chiefly of dolomitic lime- 

 stones and sandstones. They were assigned by the first Geo- 

 logical Survey of the State to the Lower Silurian and Calcifer- 

 ous age and were classified as follows, from the top downwards:* 



First Magnesian Limestone. 



Saccharoidal Sandstone. 



Second Magnesian Limestone. 



Second Sandstone. 



Third Magnesian Limestone. 



Third Sandstone. 



Fourth Magnesian Limestone. 



Fourth Sandstone. 



This assignment and classification were followed, with slight 

 modifications, by Shumard, Meek, Broadhead and others in 

 later works, though, in the first report *cited,f the discovery of 

 a trilobite is noted in the Third Magnesian limestone which 

 was considered identical with one in the Potsdam sandstone of 

 ISTew York, and in later reports and papers Broadhead refers to 

 the lower members of the series as of probable Potsdam age4 



Walcott, in recent writings, reasoning largely from the 

 published results above referred to, has included the lower 

 members of the Ozark series in the Cambrian§ and expresses 

 this conclusion in the following words : || " The Cambrian rocks 

 in Missouri occur in the southwestern^ portion of the State, 

 about the Ozark Uplift. As far as known they are of Upper 

 Cambrian age and consist of a sandstone that occurs beneath 

 the third magnesian limestone, or Calciferous, and the fourth 

 magnesian limestone of the Missouri survey, beneath which, 

 according to Prof. G. C. Broadhead, there are other arenace- 

 ous and calcareous beds." According to this the last three 

 numbers of the table given above would belong to the Cam- 

 brian. 



Recent work of the present Geological Survey of Missouri 

 has shown that a re-classification of the members of the Mag- 



* Swallow. 2nd Annual Report 1854, Part I, pp. 115 to 130. 

 ■f- Ibid., p. 124. 



% Report Missouri Geological Survey 1873-74, pp. 352, 257, 358. 

 § The North American Continent in Cambrian Time, and Bulletin No. 81, TJ. S. 

 Geological Survey, Correlation Papers — Cambrian. 

 J Bulletin 81, p. 339. 

 ^T Southeastern probably meant. 



