GEOLOGICAL SECTION OF NEW JERSEY 267 
obliterated by erosion previous to the deposition of the Cretaceous 
sediments which overlap the beveled edges of the Triassic beds along 
their southeastern margin, and which formerly extended much farther 
northwestward than at present. 
THE CRETACEOUS SYSTEM 
The Cretaceous strata rest unconformably upon the beveled edges 
of the Triassic shales along their southeastern margin. ‘They com- 
prise unconsolidated sands and clays, which dip 50 to 25 feet per 
mile to the southeast, and which have an aggregate thickness of from 
500 to 1,000 feet, the greater thickness being formed in the northern 
portion. The lowermost beds are referred to the upper part of the 
Lower Cretaceous and are of non-marine origin. ‘The middle and 
upper portions, however, belong to the Upper Cretaceous and contain 
an abundant marine fauna. 
Raritan jormation.—The Raritan formation is extremely variable, 
consisting chiefly of light-colored sands and clays, some of the latter 
being highly refractory. There is on the whole a preponderance 
of clays in the lower and of sands in the upper half of the series. Since 
it was laid down on an irregular surface its thickness is variable, 
ranging from 150 to 250 feet at the outcrop, but increasing to the 
southeastward, as shown by well-borings, to over 500 feet. Northeast 
of Trenton it rests unconformably upon the beveled Triassic shales, 
but farther southward upon the ancient crystallines of early Paleozoic 
or pre-Paleozoic age, and perhaps at undetermined points still farther 
south on earlier Cretaceous beds. It dips 4o to 50 feet per mile to 
the southeast, the basal beds having the steeper inclination. The 
known fauna is very limited, consisting of a few pelecypods, some 
of which are brackish-water types while two are typically marine, 
a plesiosaurian bone, and possibly an insect. Its flora embraces 
a wide range.of genera and species, especially of dicotyledons, many 
of which are closely related to modern forms. It has been regarded 
by Ward as late Lower Cretaceous and, therefore, approximately 
equivalent to the Gault of England. 
Magothy formation—The lignitic sands and clays referred to 
the Magothy formation and regarded as the lowermost of the Upper 
Cretaceous formations were until recently included in the Raritan. 
