2(^0 ASHLEY — GEOLOGY OF ARKANSAS. [May 13, 



(a) The sandstone most commonly met with is a soft, olive green 

 sandstone, upon exposure decomposing rapidly into sand. Except 

 when freshly exposed this rock is seldom seen in its massive state ; 

 but its soft edges are constantly found in the roads and over the 

 more level territory. Probably this sandstone differs from the next 

 only in lacking iron. 



{d) The bulk of exposures of a massive character are of a fer- 

 ruginous sandstone, usually a dark red or brown. In this, expo- 

 sure to the air oxidizes the iron, which forms a cement and makes the 

 exterior much more impervious. Frequently the brown color pene- 

 trates only a short distance, and the interior is a steel gray or light 

 green in color. 



(c) In a few localities a very white sandstone was found. Sur- 

 face exposures are usually quite soft. Where fresh, as was found in 

 digging a well on the farm of Mr. Tom Hodges in 6 S., 19 W., 

 section 4, it is exceedingly tough, making digging very slow and 

 laborious. A few months' exposure of the rock is sufficient to ren- 

 der it very friable and mealy. In places it shows slight traces of 

 pyrite. 



(^) Of frequent occurrence are varieties of finely laminated sand- 

 stones verging into shaly sandstones or arenaceous shales. These 

 are usually dark colored or black, and, where the layers are not too 

 thin, are said to make good stones for chimneys and fireplaces. 

 They often occur in layers not more than a quarter of an inch thick, 

 and are frequently found interbedded with shale. There are many 

 intermediate forms, and varieties differing both in hardness and 

 color, but they are not worthy of special mention. 



Shales. — The presence of the shales is usually indicated only by 

 the topography or by their being struck in digging wells. Single 

 beds are seldom over fifty feet thick, though in a few places it has 

 a thickness of from one hundred to three hundred feet, and in one 

 place on the Cossatot, in 6 S., 30 W., section 19, it appears to 

 have a thickness of six hundred feet. In one place a thickness of 

 twenty feet was seen to thin out within two hundred to three hun- 

 dred yards. 



It varies in lithographic characters very like the shale of other 

 regions ; sometimes it breaks up upon exposure into long, slender, 

 needle-like fragments; sometimes it breaks up into thin laminae or 

 flakes ; at other times it is traversed by joints that cause it to break 

 into angular blocks, and these all weather rapidly into clay. In 

 color they are black, lead colored, cream colored, and reddish. 



