PAPERS BY MEMBERS I 2 1 



The general characters of each of the formational units 

 designated above -will be outlined here. 



1. Brewerville Sandstone. 



General characters. In its original application by Engel- 

 niann. the name Cypress was used to designate a series of 

 "quartzose sandstones with some shaly portions, about 150 

 feet thick." which have a prominent development on Cypress 

 creek in Johnson county. The same formation was recog- 

 nized by \\'orthen in the ]^Iississippi river bluffs below 

 Prairie du Rocher. although he never used the name Cypress, 

 referring to it always as "the lower sandstone of the Chester 

 group.'' The thickness of the formation, as recognized by 

 \\'orthen. was "from 50 to 100 feet or more.'' Excellent ex- 

 posures of the formation in the Randolph- Monroe County 

 area, are to be seen in the Mississippi river bluff's immediately 

 above !Modoc. and in the ravines between Modoc and Prairie 

 du Rocher. also in the valleys of the north and south forks 

 of Horse Creek and their tributaries west of Red Bud, in the 

 valley of Rock House Creek southeast of Waterloo, and in 

 the valleys of Prairie du Long Creek and its tributaries east 

 and northeast of \\'aterloo. 



It was apparently the purpose of Englemann, and also of 

 W'orthen. to include in the Cypress formation all the essen- 

 tially arenaceous beds in the basal portion of the Chester 

 group, and Ulrich's interpretation also conforms with that of 

 these earlier writers, although he states that "in the most 

 complete development of the formation it is divisible into 

 three members or beds." (5) The upper member is said to 

 include thin-bedded and slightly argillaceous strata, the 

 lower member being apparently always massive. The mid- 

 dle bed of Ulrich. "a highly fossiliferous. cherty. blue, fine- 

 grained limestone, rarely more than four or five feet thick," 

 is said to lie 60 feet to 8o feet beneath the top of the forma- 

 tion. 



The field studies of the writer have shown that these 

 lower arenaceous strata of the Chester group are divisible 

 into two distinct formations, separated by an unconformity 

 and overlap. For the lower of these formations, which in- 

 cludes the more massive basal member of the Cypress as that 

 term was used by Engelmann and by Ulrich. the name Brew- 

 erville is proposed. 



The formation is a very massive, fine or medium grained 

 sandstone in thick beds, often more or less conspicuously 

 cross-bedded. Its color on freshly broken surfaces is a soft 

 brown tint, which in sonie localities becomes nearly white. 

 Xot infrequently it is mottled with small, darker brown 

 specks. On long exposed, weathered surfaces, the color in 



