Pebeuaky 25, 1921] 



SCIENCE 



191 



which I have been permitted to leturn to 

 Texas and renew the studies of these forma- 

 tions, have shown that the lithologic aspect 

 of each instead of representing definite and 

 fixed time positions in their horizontal extent, 

 moves upward through the geological column 

 as it is respectively traced east or west from 

 the locality of the standard section in Central 

 Texas, as is shown on the accompanying dia- 

 gram table. The position of the Austin 

 Chalk ascends to the eastward from Central 

 Texas towards northeast Texas and Arkansas, 

 where it is known as the Anona Chalk, and 

 Alabama, where it is called the Sebna. 



The Austin Chalk in the course of this 

 ascent practically continues from the Nio- 

 brara to the Ripley or near Fox Hills stage 

 of the time column, and is accompanied by 

 corresponding changes in its fauna. This 

 transgression of the Austin Chalk has re- 

 cently been noted by my associate Mr. J. E. 

 Brantly in a recent report on the oil fields of 

 Alabama, published by the State Geological 

 Survey of that state. 



Recently while studying the geology of the 

 Fort Stockton Country in Pecos County, 

 Texas, the writer observed a similar instance 

 of transgression by the Edwards limestone. 

 In this instance both the lithologic and 

 paleontologic facies of the Edwards limestone 

 formation, which occupies a fixed position in 

 the geologic column in Central Texas, is 

 found to have transgressed through time di- 

 agonally until it occupies a higher and alto- 

 gether different one in the vicinity of Fort 

 Stockton, as it is traced to the westward from 

 Austin towards the east front of the Cordil- 

 leran Ranges. This formation in both locali- 

 ties largely consists of cellular and semi- 

 chalky white limestones which weathers gray 

 and yellow, accompanied by a characteristic 

 fauna of fossil species (Rudistes, corals, 

 echinoderms, etc.). 



In the typical Central Texas section hereto- 

 fore described the Edwards limestone and its 

 fauna occur in a definite position below the 

 Kiamitia and Duck Creek formation. In 

 the vicinity of Fort Stockton where it occurs 

 as the cap rock of extensive areas, it was 



DIAGONAL TKAiJSGKESSION OP THE EDWAEDS LIME- 

 STONE AND AUSTIN CHALK 



found with the same lithologic aspects and 

 fauna as in Central Texas, but its strati- 

 graphic position was found to be above the 

 Georgetown Duck Creek and Kiamitia forma- 

 tions and faunas, instead of below them, as it 

 normally occurs in the Central Texas sections. 



The only hypothesis I have to offer for 

 these peculiar conditions is that during the 

 two epochs similar conditions of depth and 

 environment must have continued with shift- 

 ing location as time progressed, but at present 

 I can not explain why the fauna of the 

 Austin- Anona Chalk changed with this trans- 

 gression while that of the Edwards persisted. 



This fact may have important bearing 

 upon the correlation of the Texas Cretaceous 

 sections with those of Mexico, and assist in 

 the interpretation of the as yet but little 

 understood formations of the latter county. 

 Robert T. Hill 



Dallas, Texas 



THE AMERICAN MATHEMATICAL 

 SOCIETY 



The twenty-seventh annual meeting of the so- 

 ciety was held at Columbia University on Tuesday 

 and Wednesday, December 28-29, with the usual 



