JV. H. Darton—Magothy Formation of Maryland. 411 



They lie loosely — a characteristic feature, in beds usually quite 

 thin and regular but locally cross-bedded, sometimes to an 

 extreme degree. The thickness varies from 10 to 30 feet but 

 about 15 feet is the usual amount. An admixture of carbo- 

 naceous materials is often present in the form of grains but 

 several thin beds and interbeddings of lignite have been ob- 

 served. A few thin streaks of pale gray clays occur interbed- 

 ded in the formation in the Bohemia River region. 



The unconformities between the Magothy and Potomac below 

 and with the Severn above are planes of erosion everywhere 

 distinct and participating in the general southeastward inclina- 

 tion of the Coastal plain deposits. 



East of Chesapeake Bay. — The northeasternmost exposures 

 of the Magothy formation, which I have observed, are in the 

 vicinity of Chesapeake City near the eastern terminus of the 

 Chesapeake and Delaware canal. The cuts of the canal begin 

 about two miles east of Chesapeake City and are in the marls 

 and black sands of the Severn formation of which they afford 

 a superb exposure. At the western end of these cuts and in 

 several small stream depressions in the vicinity there are 

 showings of the Magothy sands overlain by the black 

 Severn beds. The sands are white, gray, and buff, streaked 

 irregularly with light brown. The entire thickness of the 

 formation was not observed in this region but in one exposure 

 twenty feet of its sands were seen, capped by weathered, gray- 

 brown Severn beds along an undulating plane of unconformity. 



Between Chesapeake City and Bohemia Creek small expo- 

 sures of Magothy beds are frequent in the deeper stream cuts. 

 They are overlain directly by the Columbia gravels and loams 

 westward, and the feather-edge of the Severn sands eastward. 



On the south shore of Bohemia Creek near its mouth there 

 is a long, high bluff in which the Magothy and adjacent forma- 

 tions are finely exposed. The basal beds are typical Potomac 

 variegated clays, pink and red predominating, but in part buff 

 and dark lead color. These clays extend to an altitude of 

 about 30 feet at the western end of the bluff but this upper 

 surface dips gently eastward and finally sinks below the water 

 in about a mile. This upper surface is an undulating plane 

 presenting no marked irregularities of contour and it is clearly 

 a product of aqueous erosion. It is overlain by the Magothy 

 sands which have a thickness varying from fifteen to twenty- 

 five feet. These sands are mainly white or light gray 

 but in places they are stained with buff and pinkish stream- 

 ings. The materials are moderately coarse quartz grains 

 quite uniform in size, rounded or subangular in greater 

 part and lying loosely compacted in thin beds with but little 

 cross-bedding. Near their base they sometimes contain a 



Am. Jour. Sci.— Third Series, Vol. XLV, No. 269. — Mat, 1893. 

 29 



