30 Journal, of the Mitchell Society [^June 



time the location of the present site of Chapel Hill with respect 

 to the sea was somewhat like that of Annapolis, Md. This long, 

 narrow body of water extended northward into jSTew England 

 and is known as the Triassic sea. The rocks formed by disposi- 

 tion in it and near it are conglomerates, sandstone, quartzite, 

 arkose (contains orthoclase and muscovite). They occur on the 

 plain, also as outliers resting unconformably on the flank of the 

 eroded granite of the stock. 



The sea was a shallow one as it receded. This is shown by 

 the fossil deltas, sand dunes, mud cracks, etc., left above the 

 deeper water deposits. Arms of the sea were cut off as it with- 

 drew, and evaporation left among the sediments, its salts, which 

 give salinity to the water of the wells and springs of this part 

 of the area. The swamps of these low areas were the feeding 

 places of very large lizard-like animals whose tracks and fossil 

 remains are found in these beds. These rocks carry also the 

 petrified forest of North Carolina, part of which is about two 

 miles east of Chapel Hill. 



ISTear the end of the Triassic period, its rocks were folded*^ and 

 faulted and some intrusions of igneous dikes, sheets, etc., prob- 

 ably occurred. A very long interval of erosion took place before 

 the close of the era and the elevation again became low. 



CENOZOIC EEA 



Several changes in elevation occurred during this era as the 

 sea twice advanced from the east nearly as far as the present site 

 of Raleigh. The most striking thing in the geological history of 

 this vicinity is the fact that most of it has remained a land area 

 almost continuously since Pre-Cambrian times. As a result of 

 this very long interval of weathering and erosion the bedrock is 

 covered by a residual mantle rock described in the following : 



generalized SECTION" 



1. Soil, " Top soil," red to gray and black (humus), 1 to 2 ft. 



2. Subsoil, fine, red to yellow clay 3 to 10 ft. 



3. Clay, coarse, lumpy, some sand 5 to 20 ft. 



" ISIiss Florence Bascom, Historical Geology of tlie Piedmont Area. U. S. 

 Geol. Survey, Trenton, N. J. Folio No. 167, p. 19. 



