48 THE PERMO-CARBONIFEROUS RED BEDS OF 



to have sufficient concentration may come from permanent water bodies, either 

 lakes or seas. The deposit, therefore, comes not from the direction of the land, 

 but from the direction of the sea. The cracking goes on between the extreme levels 

 of high and low water, and the slight shifting of level is not a tidal, but at least a 

 seasonal, phenomenon. Such mud-cracking of limestones is a playa phenomenon, 

 and, especially in certain earlier ages, when the lands were base-leveled and lay 

 awash with the sea, broad areas seem to have been at times marine playas. Marine 

 fossils, often of depauperated facies, occur sometimes in the mud-cracked limestones. 

 The nearest approach in the modern world is found, doubtless, in the Runn of 

 Cutch, an area of 10,000 square miles flooded by the sea for a part of the year, 

 during the period of onshore monsoon winds." 



This evident sequence of changes in climate and deposits, together with 

 the change in the vertebrate life found in the beds, seems to me to be suffi- 

 cient evidence upon which to establish the separation of the Wichita beds 

 from the Clear Fork at just about the line originally drawn by Cummins. 



Above the highest limestones, appearing at Seymour and on a line east 

 of north from that town to beyond the Big Wichita River, there is a con- 

 siderable thickness of red clays, sandstones, and conglomerate, including the 

 Wichita conglomerate. This means a return to the more stable and arid, 

 or semiarid, conditions characteristic of Wichita time. But the change in 

 climate was not a sudden one, for overlying the uppermost limestones there 

 are 25 to 30 feet of gray, blue-green, and purplish clays, most clearly seen 

 in their darker phases in the bluffs, where the Seymour- Vernon road crosses 

 the Big Wichita River. These beds give place horizontally to red clay in 

 places, and are overlain by red clay. 



Above the first series of red clays with sandstones and shales, which lies 

 over the highest limestone, is the Wichita conglomerate, a deposit of consider- 

 able extent in the valleys of Indian and Coffee Creeks (plate 8, fig. 2) on the 

 north side of the Big Wichita River, and traceable over a much larger area, 

 if, as is probable, it is the same layer which occurs at Haskell, in Haskell 

 County. It is a hard, pebbly conglomerate, 6 inches to a foot in thickness, 

 and varying in color from dark to light, but being through much of its extent 

 a deep purplish-red, varying to a light green color, which is very noticeable.^ 

 The lighter shade, a pale green, is the phase seen persistently southwest of 

 Seymour. 



The origin of this conglomerate layer is difficult to conceive, occurring 

 between two highly oxidized layers, but itself low in ferric iron. Relatively 

 thin but very persistent, it presents the appearance of a quickly covered 

 sheet of flood deposited material. The possible assimiption of its formation 

 by the compound deltas of flooded rivers is negatived by the thinness and 

 uniform thickness of the deposit. 



Above the Wichita conglomerate a heavy mass of sandstones forms the 

 capping layer on the .south of the Big Wichita River, but on the north side 

 the same sandstone is covered by a considerable thickness of clay and shaly 



» Case, Bull. Amer. Mus. Nat. Hist., vol. xxiii, p. 662, 1907. 



