OF THE NEW RED SANDSTONE FORMATION OF PENNSYLVANIA. 191 



In the Report Prof. Rogers gives us his theory of the formation of this extensive 

 sedimentary deposit. He divides it, under the name of " Middle Secondary Rocks," 

 into two portions : 



" 1. Variegated calcareous conglomerate. Generally a very heterogenous rock, in 

 which a large portion of the pebbles are limestone, the cement consisting chiefly of 

 red argillaceous earth. 



" 2. Red argillaceous sandstones and red shales. Towards the lower part of the 

 formation, contains numerous beds of coarse gray arenaceous sandstone." (p. 10.) 



He considers that " all these rocks of the middle secondary dates, of which the 

 argillaceous red and brown sandstone is the prominent and characteristic variety, 

 appear from numerous geological indications, to have been produced at a period 

 subsequent to the elevation of the lower secondary strata, including the coal deposits. 

 They seem to have originated in a long narrow trough, which had its source as far 

 south at least as the eastern base of the Blue Ridge in Virginia and North Carolina, 

 and which probably opened into the ocean somewhere near the present position of 

 the Raritan and New York Bays. Their materials give evidence of having been 

 swept into this estuary, or great ancient river, from the south and south-east, by a 

 current producing an almost universal dip of the beds towards the north-west,* a 

 feature clearly not caused by any uplifting agency, but as.sumed originally at the 

 time of their deposition, in consequence of the current from the oppo.site or south- 

 eastern shore." After some observations on the igneous intruding rocks, Prof. Rogers 

 observes that " the organic remains hitherto discovered are extremely few, and the 

 evidence they afford is not sufficient to establish within near limits the area to which 

 the strata should be referred." " Later, therefore, than the carboniferous rocks and 

 earlier than the green-sand, the most appropriate title claimed by this group of strata 

 would seem to be that of the middle secondary series. Though they present an obvious 

 analogy in general aspect and composition to the new red sandstone rocks of Europe, 

 and may in fact have originated somewhere about the same epoch, yet I must prefer 

 the above designation in the present state of geological research, because the other 

 name involves the notion of an identity of age, which, from the singular paucity of 

 organic remains in the American group, may probably never be susceptible of 

 demonstration." (p. 117.) 



Prof. Rogers' opinion is, that the red coloring matter of this " Calcareous Conglome- 

 rate" is derived from the red rocks below it, and such no doubt is the case, as the 

 pasty cement is frequently composed of argilaceous matter. Near the village of 

 Pompton in New Jersey, it was detected in contact with the inferior sandstone 

 formation and the conformability of the rocks clearly ascertained. 



To sustain his theory of this being the deposit of an extensive ancient river, having 

 its source in the Southern States, and its estuary in the region of the Raritan and the 



* At angles varying from 15° to 25.° 



