24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 148 



PURCHASE RIDGE, SCOTT COUNTY, VIRGINIA 



Although the section here discussed is outside of Tennessee, it was 

 deemed worth mentioning because it is close to the State line, and 

 occurs in the northernmost Cambrian outcrop belt in this portion of 

 the Appalachians. 



Most of the Maryville and Nolichucky formations are exposed in 

 cuts on the road from Pattonsville to Clinchport, Scott County (Duf- 

 field quadrangle). The Nolichucky formation is mostly shale excepting 

 the upper (Maynardville) limestone unit. The contact with the Copper 

 Ridge dolomite is not well exposed. A partial section of the strata 

 of the Aphelaspis zone in descending order follows. 



Thickness 

 Feet Inches 

 11. Limestone: in thin, often nodular beds, mostly aphanitic, 



ribboned with shale or dolomite 75 + 



10. Limestone: similar to unit 11, but more readily weather- 

 ing to separate layers 13 



Collection cnv77, one foot below top : 

 Aphelaspis tarda c 



9. Shale, with some limestone lenses 3 



Collection cnv/7, 1 foot above base : 

 Aphelaspis tarda c 



8. Limestone : thin-bedded, alternating with shale 10 



7. Shale 1 4 



6. Limestone: crystalline, one bed filled with trilobite frag- 

 ments 5 



Collection cnu/7 : 

 Aphelaspis tarda cc 



Dunderbergia tennesseensis r 



5. Shale, with a few, thin limestone beds 6 



4. Limestone : thick-bedded 2 



3. Shale, with thin limestone beds 5 



2. Limestone : one bed 1 6 



1. Shale, with some siltstone and limestone beds. Seemingly 

 several hundred feet thick and extending to limestones 



of basal Nolichucky not measured 



Collection cnt/7 from thin limestone lens 10 feet 

 below top : 

 Aphelaspis tumifrons cc 



Pseudagnostus communis c 



The upper (Maynardville) limestone unit of the Nolichucky shows 

 the same lithology and faunal succession of the upper Aphelaspis zone 

 as in the Big Creek section. Fossils of the lower Aphelaspis zone could 

 not be found because of the unfavorable shaly lithology of the interval. 

 The massive lower limestone of the Nolichucky present in many other 

 sections is here lacking or greatly reduced. In most respects the lithol- 

 ogy of the Nolichucky is very similar to that described by Hall and 

 Amick (1934) for the Thorn Hill section. 



