NO. 3 UPPER CAMBRIAN TRILOBITE FAUNAS — RASETTI 5 



Strike. This section with its numerous fossil-bearing beds represents 

 a standard with which partial sections studied in other areas will be 

 correlated. The upper boundary of the Nolichucky formation is here 

 set at the first appearance of dolomite beds, which at Big Creek coin- 

 cides with the disappearance of limestone. However, Rodgers (1953) 

 assigned some of the lower, noncherty dolomite beds to the upper 

 portion of the Nolichucky (Maynardville limestone member) rather 

 than to the overlying Copper Ridge dolomite. The author, without 

 questioning the reasons that prompted this assignment, has provision- 

 ally placed all the dolomite in the Copper Ridge formation because this 

 boundary was more readily recognized in the field. In other sections 

 there is an interval where limestone and dolomite beds alternate, mak- 

 ing the definition of the formational boundary more uncertain than 

 at Big Creek. 



Big Creek section, measured 3 miles northeast of Rogersville, 

 Hawkins County, Tenn. : 



Nolichucky formation Thickness 



Feet 

 8. Limestone and shale ; aphanitic, dark-gray, gray-weathering limestone 

 in thin, often nodular beds, ribboned with tan-weathering shale 



or dolomite. Some crystalline lenses are fossiliferous 67 



Collection 66 feet above base (cnx/1) : 



Cheilocephalus brachyops r 



Dytremacephalus angulatus c 



Dytremacephalus sulcijrons rr 



Collection 42 feet above base (cnw/1) : 



Aphelaspis tarda r 



Dytremacephalus angulatus c 



Collection 3-4 feet above base (cnv/1) : 



Aphelaspis tarda c 



7. Limestone and shale : similar to preceding unit, with lesser percentage 



of limestone in more distinctly nodular layers 6 



Collection 0-1 feet above base (cnu/1) : 

 Aphelaspis tarda c 



6. Shale, lacking limestone beds 16 



5. Shale, with several limestone lenses and nodules 10 



Collection 1 foot below top (cnt/1) : 

 Aphelaspis arsoides r 

 Aphelaspis tumifrons c 

 Pseudagnostus communis r 

 Collection 4 feet below top of interval (cns/1) : 

 Aphelaspis arsoides c 

 Aphelaspis tumifrons c 

 4. Limestone : one bed, massive, crystalline and conglomeratic, well ex- 

 posed across stream bed 1 



The above portion of the section was measured on the slopes SE of a 

 dry creek bed at x = 182, y = 297 mm, Burem quadrangle. 



3. Shale : finely fissile, with a few siltstone beds near the top 40 



2. Limestone: mostly very thick-bedded, light-gray, aphanitic, in part 

 crystalline or oolitic, with some intervals of intraformational 



