to
the unwearying processes of weathering and renewal, was again
persistently worn down into more even and plane-like surfaces. Over
much of this undulating and perhaps monotonous lowland there was laid
in Mesozoic times (Jura-Triassic and Cretaceous) a widespread and quite
deeply bedded series of sediments, which entered New England up the
depressed basin of the Connecticut Valley, but which apparently were
absent from the moderately elevated islands or prominences formed by
the emergent terranes of the Appalachian highlands, New York Island,
the central elevations of Staten Island, and the crystalline ridges in
New England. The general tendency and potency of sedimentation were
coastwise and southerly. This great plane was slowly raised, and
instantly became a broad territory of drainage with a removal of its
topographical dissection by streams and rivers. This, it is assumed,
occurred in Tertiary times, or those geological ages immediately
precedent to the Ice Age, and to it is assigned the final and more
significant elevation of the Appalachian Mountains. This problematical
plane thus elevated has been called the Schooley plane, "because its
flat surface is well represented in the summit of Schooley Mountain, in
New Jersey." The softer mineral elements, the more easily transported
deposits, were carried away along developing river ways, and,
determined by slopes and the nature of their beds, the present river
system approached stability. Valleys were formed, and " the process of
adjustment and erosion had proceeded so far as to outline the present
heights and valleys in their broadest, features, when mountain growth
was renewed and there occurred the uplift which resulted in mountains
of the altitude of the Highlands."
Continuous
surficial excavation and differential changes of level brought into
topographic eminence the Highlands in New York and New Jersey, Schooley
Mountain, the Wat-chung Mountains, and the Palisades. This hypothetical
domelike plane sloped from the Highlands southeastward, and
