FIELD INVESTIGATIONS IN 1 92 1 831 



it is to be correlated with Zone III of the Missouri section; hence it 

 would be Upper Sainte Genevieve and, compared with sections in the 

 Ohio Valley, it should correspond to some part of the Shetlerville. 



Over this Talarocrinus-bearing zone is a 20-foot bed of sandstone, to 

 which the field designation Swan Creek sandstone was applied. It is 

 succeeded by at least 4 or 5 feet, perhaps 6 or 8 feet, of shale with two 

 layers of limestone, one of them containing on its upper surface numer- 

 ous large specimens of Pugnoides ottumwa. Some of these specimens are 

 quite typical of the species, but the largest have a somewhat strange ap- 

 pearance because of the increase in number of plications with age. How- 

 ever, a precisely similar form occurs in the upper- part of the Sainte 

 Genevieve near Fountain, Illinois, and a specimen from that place is 

 figured and referred to P. ottumwa by Weller. 16 



The Anna section thus gives us the information that was not found in 

 Missouri and proves that Pugnoides ottumwa really does range upward 

 from the Fredonia member of the Sainte Genevieve into beds that all 

 concede to be of Chester age. Incidentally it confirms the doubt ex- 

 pressed by me in 1917, 17 that P. ottumwa is confined to the Fredonia. 



Proceeding with the Union County section, we find the Pugnoides zone 

 followed by 16 feet or more of sandy shale and thin sandstone. The 

 sandstone becomes thicker bedded toward the top of the bed and one or 

 more of the upper layers contain fossils in abundance. Nothing par- 

 ticularly characteristic was observed in this fauna except that the asso- 

 ciation, of a dozen or so of species might occur in almost any part of 

 either the Sainte Genevieve or the Gasper. In other words, it is simply 

 a typical Lower Chester fauna. 



This is succeeded by about 10 feet of highly siliceous limestone or cal- 

 careous sandstone that closely resembles and certainly has all the essen- 

 tial characters of the bed of similar thickness in the Missouri section that 

 we referred to the Yankeetown sandstone. It is followed by a 60-foot 

 series of thin and rather thick ledges of limestone interbedded with layers 

 of calcareous shale, both kinds of rock often being full of fossils. Locally 

 the top 10 to 20 feet consists largely of red shale. Over it is a thin sand- 

 stone, in this region apparently not exceeding 5 feet in thickness, and 

 then about 25 feet of shale and thin layers of limestone, rarely well ex- 

 posed, that fill the space to the base of the Cypress sandstone. 



Difficulties in correlating the Union County section. — Now when we 

 try to correlate these Union County lower Chester beds with sections to 

 the northwest and southeast, some very serious difficulties are encoun- 



16 Stuart Weller: Monograph of Mississippian Brachiopoda. Illinois Geol. Survey, 

 1914. 



« Op. cit, p. 157. 



