164 W. A. Bell — Mississippian Formations of 



In addition to Estlieria dawsom Jones, which is common^ 

 there is a Leaia of rarer occurrence, a very significant 

 fact, as Leaia elsewhere in America is eminently charac- 

 teristic of the Pennsylvanian. 



Depositional environment. — The same features that 

 denoted a fluvial environment in the case of the Horton 

 are here repeated, some of them in accentuated forms. 

 Thus channeling, sun-cracking, fresh feldspars, little 

 altered biotite, oxidized iron content, etc., are dominant 

 properties of the Cheverie that give a unity to the deposit 

 and differentiate the formation as a whole from the un- 

 derlying one. As the material itself has been derived 

 from the same general land mass that supplied the Hor- 

 ton detritus, it is reasonable to attribute climatic influ- 

 ence as the main control of the chemical and textural 

 features of the sediments. Tumultuous current action at 

 recurrent intervals in the basal arkose mass, in conjunc- 

 tion with the presence of soil beds at like intervals, would 

 call for rhythmic pronounced accessions of water flow 

 and a sufficiently high level of the ground water in the 

 river flats during the intervals to favor a vegetable 

 growth. From a study of present-day climates, it would 

 seem necessary to postulate a warm temperate semi-arid 

 type to fulfill all the requirements. That extreme arid 

 conditions were wanting is evidenced by the absence of 

 pebbles. The presence of nodules of reddish calcium 

 carbonate in the red soil beds of the upper part of the 

 formation suggests homology mth the ^^kankar'' in the 

 alluvium of the Indo-Gangetic plain. 



Correlation. — The stratigraphical position of the 

 Cheverie formation between the Horton below of Kinder- 

 hookian age and the Windsor series above of Chesterian 

 age does not closely define its position in the Mississip- 

 pian. It is the addition of an eremopterid flora and the 

 distinct climatic break that have led to the inclusion of 

 the Cheverie in the lower Tennesseean rather than in the 

 Osagian. The break between the two terrestrial forma- 

 tions, the Horton and the Cheverie, is believed to be 

 greater than that between the terrestrial Cheverie and 

 the marine Windsor. 



Windsor Series. 



Description. — The Windsor series comprises a well de- 

 fined unit of marine deposits laid down under peculiar 



