652 INDEX TO THE STEATIGRAPHY OF NORTH AMERICA. 



clay marl, chalks, and glaucordtic sands. South of the Sulphur Fork of Red River to the Colo- 

 rado the beds consist almost exclusively of glauconitic sand and clay marls, there being only 

 a few local occurrences of secondary limestone or arenaceous flags. 



I 15. NORTHEASTERN TEXAS, ARKANSAS, AND LOUISIANA. 



According to Veatch ^^^ — 



The upper Cretaceous of Arkansas is composed of the following members, beginning with 

 the lowest : 



1. Sands with bituminous laminated clays containing leaf impressions and lignite beds — the Bingen 



formation. 



2. Blue calcareous clay with Exogyra ponderosa — the Brownstown formation. 



3. White chalk — the Annona chalk. 



4. Calcareous clay or clayey chalk, with considerable greensand — the Marlbrook formation. 



5. Indurated sand, with thin calcareous and quartzitic layers locally called "water rocks," glauconitic 



in part — the Nacatoch sand. 



6. Dark calcareous clays, fossiLiferous below, which pass upward without a sharp break into the 



sandy, lignitiferous lower Eocene beds — the Arkadelphia clay. 



The near-shore character of the Bingen sand is in such contrast to the overlying and under- 

 lying Cretaceous marls and in the outcrop is so similar to the overlying sandy surficial deposits 

 of the late Tertiary that in Arkansas it has heretofore, with the exception of a limited outcrop 

 near Morris Ferry, either been confused with the surficial deposits or been regarded as an outlier 

 of the Lower Eocene beds, which it closely resembles lithologically.'* 



This formation consists of white or brown sands and clays containing some greensand and 

 considerable lignite or lignitiferous matter, in which respect it differs from the overlying forma- 

 tions. 



********* 



To the west and south the beds below the Brownstown and Taylor marls thicken rapidly, 

 and the various sand beds encountered together in southern Sevier and Howard counties, Ark., 

 become greatly separated by layers of clay. * * * 



The Bingen sand, while the Hthological counterpart of the Woodbine formation, is appar- 

 ently the time equivalent of all the beds of the lower [upper] Cretaceous below the Browns- 

 town and Taylor formations. 



***** *** ^! 



The Brownstown formation, into which the Bingen sand gradually grades, is well developed 



in the southern part of Sevier County, Ark., about Brownstown, from which place it takes its 



name. It is a blue or gray calcareous clay containing many fossil oysters and is characterized 



by the presence of the large oyster Exogyra ponderosa, whence it has sometimes been called 



the Exogyra ponderosa marl. * * * It is limited above by the Annona chalk and has a 



total thickness of 150 feet in the eastern part of the area and 600 feet in the western. 

 ******** * 



The White Chffs chalk,* [so named] from the bluffs and village of that name on Little 

 River, in the northeastern part of Little River County, Ark., was renamed the Annona chalk'' 

 from the town of Annona, Red River County, Tex., because it was found that White CUfIs as a 

 formation name had been applied by Powell'* to certain Juratrias beds in Utah. It consists 

 of white chalk, which at White Chffs has a thickness of over 100 feet, but thins out rapidly 

 to the east, disappearing entirely before reaching Okolona, where Taff has found only the chalky 

 marl which, at the type locahty, underlies it. 



a Hill, R. T., Ann. Kept. Geol. Survey Arkansas for 1888, vol. 2, 1888, pp. 56-58; Bull. Geol. Soc. America, vol. 5, 

 1894, p. 309, PL XII; Twenty-first Ann. Kept. U. S. Geol. Survey, pt. 7, 1901, p. 195, fig. 21. 



b HUl, R. T., Ann. Kept. Geol. Survey Arkansas for 1888, vol. 2, 1888, pp. 87-89. 



c Hill, R. T., Bull. Geol. Soc. America, vol. 5, 1894, p. 308; Twenty-first Ann. Kept. U. S. Geol. Survey, pt. 7,. 

 1901, p. 340. Hill's spelling Anona has been changed to ^nnona, the spelling used in the Postal Guide and on Hill's- 

 map of the Black and Grand prairies of Texas, 1899 (Twenty-first Ann, Rept. U. S. Geol. Survey, pt. 7, 1901, PI. LXV).. 



<* Geology o£ the Uinta Mountains: U. S. Geol. and Geog. Survey Terr., 2d div., 1876, pp. 41, 51, 151. 



