370 DRAKE — THE GEOLOGY OF INDIAN TERRITORY. [Sept. 3, 



Stone is underlain by alternating strata of shaly sandstones and 

 arenaceous clay shale, which in turn is underlain by thirty feet of 

 gray fossiliferous limestone. 



Farther west, south of Wilburton, only one limestone bed was 

 seen, but others are probably covered by debris. A somewhat 

 generalized section at this point is shown in Sec. 12. Farther to 

 the west the limestone beds increase rapidly in thickness, until 

 south of Hartshorne the lowest one is about one hundred and fifty 

 feet thick. 



Strata of Black Fork, Rich and Windings tair Mountains. — Mas- 

 sive sandstones with regular texture and smooth bedding planes and 

 dark gray clay shales are the prevailing rocks of these moun- 

 tains. The sandstones in the southern part of Black Fork 

 mountain are about one thousand feet thick, principally massive, 

 and light in color; some flaggy and shaly beds occur near the 

 centre of the section. The sandstones of the south side of Rich 

 mountain appear to be about one thousand feet thick and closely 

 resemble those of Black Fork mountain, but are seemingly some- 

 what more flaggy and have a little more interbedded clay shale. 

 The strata in the valley between the two mountains and those in the 

 north side of both mountains are principally arenaceous clay shale 

 and thin beds of sandstone. Along Big creek on the north side of 

 Black Fork mountain, 'the sandstones and shales are distributed in 

 the proportion of about one of sandstone to five of shale. The sand- 

 stones are usually from four to eight feet thick and have irregular 

 bedding planes. About one mile east of Page a massive sandstone 

 about fifty feet thick is broken across by a fault and so impregnated 

 with bitumen that the rock has a very black color. There is a 

 small anticline immediately southwest of this point in Big creek. 



These irregularities seem to be only local breaks and crumplings 

 on the side of a very large fold. Windingstair mountains appear 

 to be the westward continuation structurally and stratigraphically 

 of Black Fork and Rich mountains. Sec. 9 shows in a general 

 way the stratigraphy of the Windingstair mountains south of Han- 

 son creek. The north side of the mountains at this point is steep 

 and rather free from ridges or canons running parallel to the range, 

 while the southern slope is broken by a number of ridges running 

 parallel to the main mountain and less elevated toward the south. 

 Deep erosion channels lie between some of these ridges and connect 

 with a cross channel leading into the Kiamichi valley to the south. 



