50 N. II. Darton — Fossils in tin- "Archcean" 



Art. V. — Fossils in the "Archaean" rocks of Central Pied- 

 mont Virginia; by X. H. Darton, U. S. Geological 

 Survey. 



It is my purpose in this paper to announce the discovery of 

 organic remains of Louver Silurian age in the roofing slate at 

 Arvon, Buckingham Count} 7 , Virginia. 



Piedmont Virginia received considerable study from W. 

 B. Rogers in the State Surveys of 1835 to 1810, but I know 

 of no subsequent investigations of its structure. The region 

 contains a great variety of rocks, comprising granites and 

 gneisses in large part, mica schists, chlorite schists, slates, mar- 

 bles, conglomerates and various basic intrusives. The elastics 

 are considerably metamorphosed and apparently their structure 

 is complicated. 



During a recent reconnaissance of the Piedmont plain west 

 of Richmond, in connection with studies of its geomorphology, 

 I found myself near the slate quarries at Arvon, and on visit- 

 ing them I discovered the organic remains. The locality is on 

 a small branch of Slate River four miles southwest of Bremo 

 Bluff Station on the James River, in the northeastern corner 

 of Buckingham County. The belt is one of several which 

 occur in Piedmont Virginia. The slate is hard and durable 

 and it is extensively quarried for the market. W. B. Rogers 

 refers to these slates in the part on Virginia in Macfarlane's 

 •Geological Railway Guide and classifies them as Huronian, but 

 on what grounds is not stated. I did not have time to study 

 the local geologic relations of the slates, but it was noticed that 

 they lie in a closely folded syncline in an altered sandstone 

 which is in turn underlain by a highly altered conglomerate. 

 This conglomerate increases in mass southward and finally gives 

 rise to Willis Mountain, an elevated knob which stands out 

 prominently above the Piedmont plains. The cleavage of the 

 slate dips S. 70° E. >85°. The slates are cut by dikes of dia- 

 base which have caused some local shattering, and they also 

 contain occasional knots of quartz in which Dr. G. II. Williams 

 recently discovered the mineral anatase.* 



The fossils occur in a narrow belt along which the bedding 

 and cleavage coincide. This portion of the quarry is now in 

 greater part buried under debris, but owing to the kindness of 

 Mr. Williams, the superintendent, I was able to secure several 

 slabs. ' The remains are solely of crinoids and the slabs bear 

 many fragments of various parts of these organisms. The 

 accompanying figures represent the more characteristic forms, 

 faithfully reproduced by Mr. Hunter of the Geological Survey. 



* This Journal, III, vol. xlii, pp. 431, 432. 



