walcott.] SUMMARY TENNESSEE. 301 



and approach tine conglomerate. It may be mentioned, too, that not unfrequently 

 the strata have green grains (glanconite) disseminated through them. 



The sandstones of this group very often show the worm-holes, and the sandy rods 

 within them, belonging to Hall's species Scolithus linearis. It is the exception not tc 

 meet with them. In addition to these, the surfaces of the strata sometimes show im- 

 pressions of fucoids. No other fossils, that I know of, have been found in this horizon 

 of Tennessee. 



This formation is by no means as thick as the Ocoee series ; yet it has volume 

 enongh to form conspicuous mountain ridges. It is not easy to determine its thick- 

 ness; its maximum is not less, however, than 2,000 feet, and it may be considerably 

 more. 1 



This general description is followed by the detailed description of a 

 number of sections. The lithologic features of this formation are much 

 the same in all of its presentations, from Virginia to Georgia. 2 



Knox sandstone and shale. — In the table of geological formations the 

 Knox group is next in order above the Chilhowee sandstone, and its 

 basal member is formed by the Knox sandstone. 3 The principal rocks 

 of the Knox saudstone are hard shales and thin sandstones, heavier 

 sandstones being interstratified with these. The heavier sandstones 

 are tine or coarse grained, sometimes quartzose. They occasionally 

 abound in green grains. In the section of Webb's Ridge, near Kuox- 

 ville, the hard, dark, gray sandstone referred to occurs six times in 

 beds from three to ten feet thick, and weathers into a buff, softer ma- 

 terial. In general, the included layers vary much in appearance. As 

 before stated, beds of dolomite are met with in the division. 4 



The thickness of these rocks can not be much less than 800 or 1,000 feet. In Webb's 

 Ridge, where they are in less force than at many other points, the thickness is 540 

 feet. 



The strata are often ripple-marked, and sometimes covered with fucoidal impres- 

 sions and ridges. Aside from fucoids, I have not met with any fossils in these rocks. 

 # * * 



It may be mentioned as a prominent feature of this division and of the Knox shale 

 overlying it that they present shales and sandstones of many different colors. The 

 rocks are pale green, brown, and red, chestnut-colored, buff, gray, and other colors. 

 Brownish red, greenish, and buff are, perhaps, the prevailing tints. The colors are 

 often bright, and notably agfeeable. 



In reading the description of the Knox sandstone by Prof. Safford, I 

 •have failed to find any general or detailed section or description that 

 connects the Chilhowee saudstone and the Knox sandstone. Appar- 

 ently there is not any section known in which the two are seen in strat- 

 igraphic relation to each other. From the character of the section 

 and the sedimentation, it may be that the Knox sandstone is the repre. 

 sentative of a portion of the Chilhowee series, the former being the 

 off-shore deposit, while the Chilhowee sandstone accumulated near the 

 shore. 



The Knox shale is largely a variegated shale, with interstratified 

 beds of thin layers of blue limestone, which is often oolitic. 



*<* > — . — „ -...., , .. , , — . ■ .— _ . 



1 Geology of Tennessee, pp. 198, 199. 3 Op cit., p. 158. 



* Op. cit., 1869, p. 203. 4 Op. cit., p. 209. 



