192 PHYSIOGRAPHY, GEOLOGY AND MINERAL RESOURCES

from its typical occurrence in the valley of the Patapsco river, forms
the lowest division of the Cretaceous deposits here described. It
extends entirely across the state from the Delaware border to the
Potomac river, and throughout this distance is one of the most im-
portant members of the Cretaceous series.

The deposits of this division consist chiefly of highly colored and
variegated clays which grade over into lighter colored sandy clays,
while sandy bands of coarser materials are at times interstratified.
The sands frequently contain much decomposed feldspar, and rounded
lumps of clay occur at times. The sands are often cross-bedded, and
all the deposits give evidence of shallow water origin. The formation
is estimated to reach a thickness of 200 feet. The deposits rest very
unconformably upon the Arundel below.

The fossils obtained from this formation consist entirely of plant
impressions and a few indeterminate molluscan shells. The flora is
very rich both in species and individuals. It has already been exten-
sively investigated by Professor Ward of the U. S. Geological Survey,
who finds a considerable representation of dicotyledonous types of
vegetable life among the forms examined. The general assemblage
of types is distinctly Cretaceous.

THE RARITAN FORMATION. —The Raritan formation, so called
from its typical development in the valley of the Raritan river in New
Jersey, extends across that state into Maryland. It is found in Cecil
and Kent counties and extends thence southeastward along the eastern
border of Harford and Baltimore counties into Anne Arundel county,
where it broadens out and occupies a large extent of country along
the Severn river. Beyond the Patuxent valley the area of outcrop
narrows, as the result of the transgression of the overlying upper
Cretaceous strata.

The deposits of the Raritan formation consist chiefly of thick-bedded
and light colored sands, which at times become gravels. Frequently
in the lower portion of the formation the sands grade over into clays,
which are generally light in color and highly silicious, although they
are sometimes deeply colored. The thickness of the Raritan forma-
tion reaches about 500 feet. The deposits overlie unconformably the
Patapsco sediments below.