1f48, 49 | DEPOSITION OF THE ORANGE SAND. 27 



waters of the Hatchie, Tuscumbia, Big Bear, and other southern 

 tributaries of the Tennessee River in Alabama. The Western 

 Highland Rim of Tenneesee (see map accompanying the Geological 

 Reconnoissance of Tennessee, by M. Safford, 1856) appears to 

 have prevented the irruption of this current, to any great extent, 

 into the Tennessee Valley and the Central Basin of Tennessee ; 

 the pebble beds as well as (in N. W. Alabama) heavy deposits of 

 Orange Sand extend along the western and southern border of the 

 Carboniferous region, between the Tombigbee and Warrior rivers, 

 and eastwards to the Coosa ; meeting, perhaps, still further east, 

 the deposits brought down on the E. side of the Alleghanies, on 

 which the cities of Baltimore, Washington, Richmond and Peters- 

 burg, Va., and Columbia, S. C, are situated.* 



48. While the pebbles were deposited chiefly in these channels, where the 

 velocit}' was great, the intervening space, cnt up into numerous minor channels 

 by denudation, retained the smaller gravel and sand, and also, where some 

 protecting ridge afforded a chance for quiet subsidence, received deposits of 

 clayey materials, which naturally would be as limited as was the area of the 

 " slack water" itself. It is easy to understand how under such circumstances, 

 when the currents which caused the first denudations began to slacken, the 

 materials of older formations might be removed and then re-deposited with 

 little change, at no great distance from their original place, and subsequently 

 covered over with fresh masses brought from a distance. At the end of the 

 period, the violent currents having subsided, the pebble deposits themselves 

 were in many cases covered over by sands similar to those which, in other 

 regions, compose the entire formation. Still later, the processes of oxidation, 

 lixiviation, silicification and ferrugination (all of which are probably still in 

 progress) commenced, and subsequently still (apparently even later than the 

 deposition of the Bluff formation), great denudations again ensued, partly 

 contemporaneous with, partly subsequent to, the deposition of the yellow 

 surface loam — one of the latest formations, apparently, preceding our present era. 



49. However different may be the geological detail of the Orange Sand 

 formation irom that of the Northern Drift deposits, the evident anology of their 

 lithological composition and general history would lead us to suppose the 

 two formations to be genetically related. In both cases, immense volumes of 

 water destitute, or nearly so, of organic life, rushed southward, bearing with 



*See Second Report on the Geology of A labama, by M. THomey, etl. J. W. Mallet. A few months 

 prior to the death of the lamented Tuomey, dnr'ng a visit at Tuscaloosa, I compared notes with him 

 on the subject of this formation, the extensive and c aracteristic deve'opment ofwhich in Mississippi 

 and N. W. Alabama, was unknown to him at the time of writine the portion of his Report relating to 

 the same. As far as com arable, the observations, and c nclusioi s arriv d at by each of us inde- 

 pendemly, t Hied perfectly, except with refereuce to the occurrence of Vast don bones in the 

 formation, as mentioi edby him (p. 147 of the lid Report). He a mit ed, however, that the bones in 

 questiori might well be referable to the Bluff formation, the existence of which on the l.o^er Tom- 

 bigbee, t e had but shortly before as. ertained. > is suggestion regarding the naturr a' d origin of the 

 waters whi< h deposited the Ora ge Sand formation, (Ibid p. 146,) appear to be confirmed by all the 

 additional observations subsequently made by myself. 



