1892] MARYLAND ACADEMY OF SCIENCES. 109 



out border of the crystalline rocks, and when complete 

 and uplifted constituted a higli ridge of sands, shaly 

 clays and iron ore clays which were capped by a thick 

 body of lead-colored and dark clay, which by being dis- 

 turbed, dislocated and mixed with ferrous solutions has 

 become the " Variegated Clay " of the present time. 

 Erosive energies from floods and overflows out of the 

 rocky ridges farther inland played sad havoc with the 

 surface of these clays and carved them into reliefs of 

 another order. The more prominent of these reliefs now 

 stand up all along their original belt of deposition as 

 mounds, ridges, terraces and undulations. 



Albirupean Formation — Fitting into and around the 

 reliefs of the above formation, and spreading over it in 

 a general northeast by southwest direction, the Albirupean 

 appears, and extends at least from the border of the Tri- 

 assic region, north of Raritan bay, across New Jersey, 

 Delaware and Maryland to below Fredericksburg, Virginia. 



This group of deposits is the most varied and peculiar 

 of all the sedimentary deposits of the Atlantic Coast 

 Region. It includes more diflerent kinds of coarse struc- 

 tures tlian either of the great adjoining formations. It 

 comprehends an unusual number of kinds of sand of the 

 most diverse orders of structure, and many types of clay 

 equally different in composition. It includes oue or two 

 ranges of cobble-stone structures, which seem to have been 

 derived from the innumerable pot-holes that formerly 

 existed at the foot of the thousands of cascades every- 

 where present in the beds of streams current through the 

 crystalline hills and mountains next inland. 



This formation is locally invaded by narrow areas of 

 cross-bedded sands, usually placed on the northern end of 

 a ridge of the argillaceous material. These cross-bedded 

 deposits occupy troughs of erosion, and have their wedge- 

 shaped end placed against the side of the hill next its 



