Maryland Geological Survey 37 



Among other " Geological Notes " presented to the Boston Society 

 of ISTatural History in 1875 by W. B. Eogers is a paper " On the Gravel 

 and Cobblestone Deposits of Virginia and the Middle States," in which 

 he clearly distinguishes the surficial gravels of the Lafayette and Colum- 

 bia from those of the older Potomac. " In the belt partially occupied 

 by the surface deposit here referred to there is exposed another group 

 of strata with Avhich, at first view, the sandy and argillaceous layers of 

 this formation might readily be confounded. These are the silicious, 

 argillaceous, and pebbly beds, which, underlying the Tertiary in Virginia, 

 and the well-marked Cretaceous formation farther north, have, in the 

 latter region, been regarded as belonging to the base of the Cretaceous 

 series of the Atlantic States. In Virginia the formation consists typically 

 of a rather coarse and sometimes pebbly sandstone, in which the grains 

 of quartz and feldspar are feebly cemented by kaolin, derived from the 

 decomposition of the latter, and of argillaceous and silicious clays vari- 

 ously colored and more or less charged with vegetable remains, either 

 silicified or in the condition of lignite. These constitute the group of 

 beds designated in the Virginia geological reports as the Upper Second- 

 ary sandstone, and referred by me long since (184-2) to the upper part 

 of the Jurassic series, corresponding probably to the Purbeck beds of 

 British geologists. From the Potomac northward this group of deposits, 

 as exposed in the deep railroad cuts between Washington and Baltimore 

 and on to Wilmington, is made up of variegated, soft, argillaceous, and 

 silicious beds, which, from the preponderance of ferruginous coloring 

 toward the Delaware, has been called by Professor Booth the red clay 

 formation. At a few points only toward the bottom of the deposit it 

 brings to view a bed of the felspathie sand, or crumbling sandstone, above 

 referred to. Traced transversely, it is seen to dip beneath the Cretaceous 

 greensand at various points in IsTew Jersey, Delaware, and Maryland, 

 but in Virginia disappears in its eastward dip beneath the Eocene Ter- 

 tiary. 



"How far we may consider this group of sediments in Maryland, 

 Delaware, and New Jersey as merely a continuation of the Virginia for- 

 mation above described can be determined only by further investigation. 



