41 S The Upper Devoxiajc Deposits of Maryland 



is iisiially more arenaceous than tliat of the nnderlying members and 

 hence breaks more frequently into irregular pieces, while the sandstone 

 is not argillaceous and is rarely fissile. The beds are variously colored, 

 gray, olive-green, yellow, and brown being common tints. Upon weather- 

 ing many beds become yellowisli or brown and are often stained by iron. 

 Eed or brownish-red beds are of frequent occurrence, tlie percentage of 

 red strata increasing toward the top of the member. These Ijeds occur 

 at successively lower and lower horizons toward the east until in the sec- 

 tions east of Millstone, they appear near the base of the member. 



Conglomerates occur at many horizons in the Chemung clearly indi- 

 cating its littoral character. A comparison of the different sections shows 

 that there are two more persistent zones of conglomerates east of Wills 

 Mountain although it must be noted that other conglomerates are present, 

 and may readily be confused with them. These conglomerates are not 

 single beds but zones of massive sandstones some of which are usually 

 conglomeratic. They are recognizable topographically by the fact that the 

 upper zone tends to form the crest of a high ridge, when at a distance 

 from larger streams, while the lower zone tends to form a minor ridge 

 on the flanks of the larger. In the more easterly sections the Catskill 

 strata descend so close to the ujiper conglomerate as to obscure these re- 

 lations. Again, the lower conglomerate may be the stronger ridge-niaker 

 locally. 



The thickness of this member varies from 2000 to 2300 feet. 



Fauna. — 'The Chemung member contains a distinct fauna, the most 

 characteristic species of which is Spirifei- disjunctns. Associated with 

 the latter and scarcely less diagnostic, are various species of the genera 

 DalmaneUa and DowvilJina. The latter are, however, more restricted in 

 geographical distribution and vertical range. Many other species cited 

 in the table of distribution are also restricted to this member, but are 

 more limited in range and distributioji and hence less important for 

 purposes of correlation. 



Subdivisions. — Tlie upper and lower conglomerates divide the Che- 

 mung member into five parts, wliicli are hei'e termed the loM'er shale and 

 sandstone beds, the lower conglomerate, the middle shale and sandstone 



