210 ENVIRONMENT OF VERTEBRATE LIFE, ETC. 



"Several ledges of sandstone frequently occur in a single section, and where 

 one of these ledges is found thickened the others are apt to be thicker than normal. 

 Likewise they are all found to be thin over certain areas. The regions of thicken- 

 ing and thinning were found to be parallel belts lying north and south at right 

 angles to the major drainage-lines. Two of these belts, together with an inter- 

 vening region about 8 miles across, were studied. The sandstones thicken at the 

 expense of the shales, sometimes eliminating them. In one instance a thin lime- 

 stone was traced southwest into one of these zones. A sandstone 20 feet or more 

 beneath the limestone thickens and rises above the limestone and practically 

 unites with the sandstone some distance above it. The limestone seems to die 

 out a few feet from the sandstone, but farther west the latter shrinks to its 

 normal thickness and the limestone is present in its proper position with its usual 

 characteristics. 



"In these zones of thickening, which are frequently several miles wide, the 

 sandstones are very irregularly cross-bedded and frequently ripple-marked, while 

 the thickening is uneven. It would seem that these zones are opposite the mouths 

 of streams which brought sediment into the sea, where the coarser materials 

 were carried farther from the shore than opposite the interstream spaces. The 

 irregular thickening of the individual beds may be due to current work, wave- 

 action and heaping into local dunes by the wind, though the action of the last 

 factor is uncertain. The irregular bedding and ripple-marks indicate a sort of 

 littoral or very shoal condition for the deposition of the sandstones and shales. 



"As this interesting transition of sediments is traced still farther southward, 

 we find, before reaching the latitude of Shawnee, that the sandstones become 

 more abundant over the whole area, more lenticular, more irregularly cross- 

 bedded, and imperfectly lithified. In a single railroad cutting a thick lens of 

 sandstone may fade into a soft sandy clay shale with the same bedding and 

 structure as the stone itself and change back into a sandstone a few rods away. 

 Most of the sandstones are so incoherent when freshly quarried that pieces 2 or 

 3 inches in diameter crush readily under foot. In many of the wells of the region 

 the water is obtained in 'quicksand.' Most of the shales contain much fine 

 sand and offer little resistance to weathering. 



"At their southern limits these red sandstones and shales are found to dovetail 

 into the Permian conglomerates on the southern side of the Arbuckle Mountains, 

 while similar conditions obtain among the higher beds farther west, where similar 

 conglomerates occur on the flanks of the Wichita Mountains. These conglomer- 

 ates are largely composed of the fragments of the pre-Carboniferous limestones 

 aggregating 8,000 to 10,000 feet in thickness flanking the mountains and at one 

 time covering them. The solution of these limestones produces a red clay wher- 

 ever the insoluble residue happens to remain undisturbed below the vegetable 

 mold, and the disintegrating limestone conglomerates produce a more or less 

 sandy clay indistinguishable from some of the red sediments. Thus it seems 

 not improbable that much of the material of the red beds in the region studied 

 was derived from these thick limestones. 



"Considering all these phenomena, it is apparent that the transition of 

 deposits from the Arbuckle Mountains to the Kansas line is such as would be 

 expected in passing from the mountains out into a shallow epicontinental sea. 



"That the solution of limestone produces red residual clays is well known. 

 It is exhibited in the residual soils and clays of the limestone regions of the 

 unglaciated part of the Mississippi Valley, Cuba, southern Europe, and elsewhere. 



