SURATIGRAPHY (OF THE POTOMAC GROUP 485 
Many other occurrences of the Patuxent formation might be 
cited both to the north and south of Baltimore, but enough 
have already been given to show its character and relations. 
Fossils—Very few traces of organic remains have as yet 
been found in the Patuxent formation. Those which have been 
obtained consist of lignetized coniferous wood, and various 
indeterminable vegetable fragments, among which no traces 
of dicotyledonous forms have been observed. A silicified 
coniferous trunk has been found zm s¢tu at School House Hill. 
One cycad trunk is also reported to have been seen in place in 
these beds. No animal remains have yet been with certainty 
detected. 
THE ARUNDEL FORMATION. 
Name and areal distribution — The Arundel formation receives 
its name from Anne Arundel county where the deposits of this 
horizon are well developed. It has been traced as a broken 
belt all the way from Cecil county to the borders of the District 
of Columbia, and occurs as long narrow belts that extend ina 
general northwest-southeast direction forming a low angle with 
the border of the Piedmont Plateau. 
Leading features of the deposits—The deposits consist of a 
series of large and small lenses of iron ore-bearing clays which 
occupy ancient depressions in the surface of the Patuxent forma- 
tion. These clays as most typically developed (‘blue charcoal 
clays’’ of the miners) are drab colored, tough, and frequently highly 
carbonaceous, lignitized trunks of trees and limbs lying horizon- 
tally strongly compressed and frequently charged with or 
enclosed by carbonate and sulphide of iron. Sometimes these 
trunks are encountered in an upright position, with their larger 
roots still intact. Scattered through the dark clays are vast 
quantities of nodules of iron carbonate, at times reaching 
many tons in weight, and known to the miners as ‘white ore,” 
‘hone ore”’ or ‘‘steel ore.’’ Inthe upper portions of the for- 
mation which have been exposed to atmospheric influences the 
carbonate ores have sometimes to considerable depth changed 
