46 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
14 miles south of Benbolt west of the Tazewell County Farm. At its type sec- 
tion the formation consists of two members both composed of limestone, the 
lower one called Shannondale limestone and the upper one known as the Burkes 
Garden member. These member names have not been used far outside the con- 
fines of the county. The Benbolt is separated from the overlying Wardell forma- 
tion by the Gratton formation. The Benbolt is characterized by numerous dis- 
tinctive fossils that are confined to this level as far as known. These fossils make 
it possible to identify the Benbolt interval in belts in which the lithology is quite 
different from that of the type section. The Benbolt, as indicated by its distinc- 
tive fossils, is widely distributed in southwestern Virginia and northeastern 
Tennessee. Traces of the fossils occur as far north as southern Pennsylvania and 
as far south as Georgia. 
Benbolt formation in Virginia.—In the Cumberland Front sequence in extreme 
southwest Virginia the Benbolt is not typically developed, but a probably partial 
equivalent is the Hurricane Bridge limestone. At the north end of the St. Clair 
fault block the Benbolt is typically developed and is composed chiefly of limestone 
as described for the type section. To the southwest the Benbolt becomes a soft 
shale and cobbly limestone abounding in exceptionally well preserved fossils. The 
Clinch Mountain belt contains an excellent sequence of this formation which 
here is a soft gray shale. In some of these belts the Gratton limestone is absent, 
with the result that it is usually difficult to draw a satisfactory boundary between 
the Benbolt and Wardell formations. The two combined formations are then 
called Dryden formation, but it is usually possible to recognize Wardell elements 
in the upper part and Benbolt species in the lower part. 
In the Saltville fault block the interval of the Benbolt plus part of the Ward 
Cove is represented by black limestone, here called Chatham Hill formation, but 
a sufficient number of Benbolt fossils is preserved in these dark limestones to 
distinguish the presence of the formation. In west-central and northern Vir- 
ginia the Middle Ordovician sequence is dominated by the Edinburg formation. 
At the base of this formation is a zone characterized by cobbly and black lime- 
stone containing Benbolt fossils intermingled with those characteristic of the 
Arline formation. For example, Dinorthis transversa is present in the Cyrtono- 
tella and Nidulites zones of the Edinburg formation and in the lower part of the 
Shippensburg formation (Pinesburg member) of Pennsylvania and Maryland, 
which is a partial equivalent of the Edinburg. The same Dinorthis together 
with characteristic fossils of the Arline fauna betray the presence of Benbolt 
equivalents in the dark limestones exposed in the Eagle Rock (15’) Quadrangle. 
Benbolt formation in Tennessee.—The extension of the Clinch Mountain belt 
into Tennessee exposes the Benbolt formation in its shaly facies for many miles. 
It is also well displayed as a shale, often with limy cobbles and thin layers of 
limestone in Beaver, Raccoon, and Hogskin Valleys. In the vicinity of Lone 
Mountain, shale at the interval of the Benbolt appears to contain a fauna with 
Wardell as well as Benbolt faunal elements intermingled to such an extent that 
the term Benbolt is inapplicable and Dryden is used as in Virginia. In the Clin- 
ton belt the formation has lost its individuality. 
