DAftTOfr.j 
PENNSYLVANIA — DELAWARE. 
117 
Feot. 
75-93 yellow clay. 
93-103 blue clay mixed with yellow clay. 
103 - 130 coarse sand and gravel, with some clay and a few large cobbles, 
containing plenty of water. 
130-136 yellow clay. 
136-165 soft mica rock, 
165-670 hard rock. 
Several wells in the southern part of the city draw water from the 
103-130-foot horizon. 
A well bored at the corner of Laurel and Beach streets is reported 
to have had the following record: ! 
Feet. 
0-58 coarse gravel and sand. 
58-74 red clay. 
74-78 gravel. 
78-80 rock clay (disintegrated rock). 
80-308 solid rock. 
DELAWARE. 
GEOLOGIC RELATIONS. 
This State lies almost entirely on the Coastal Plain, across which 
it extends diagonally to the Atlantic Ocean. The crystalline rocks 
emerge at the surface in the extreme northern portion of the State, 
but are deeply buried under the Coastal Plain deposits to the south- 
east. The genera] structure is shown in section 1, PI. VI. The topog- 
raphy of the State is relatively simple, consisting of a general terrace 
plain averaging about 50 feet in altitude and a small area of higher 
rolling hills north and west of Wilmington. The principal knowledge 
of the geology of the State is derived from the studies of Booth over 
a half century ago and the more recent observations by Prof. F. D. 
Chester. 2 The geologic formations are as follows: 
Formation. 
Characteristics. 
Age. 
Pamunkey 
Rancocas 
Red bank 
Do 
Navesink 
Do. 
Matawan 
Do. 
Raritan and Potomac 
Early Cretaceous. 
Crystalline rocks 
Granite, gneiss, gabbro, limestone, and quartzite. . 
'New Jersey report for 1894, p. 198. 
Preliminary notes on the geology of Delaware. Academy Nat. Sciences of Phil- 
adelphia, Proceedings for 1884, pp. 237-259, map. 
