beds
were removed; the harder, more resistant, remained. These latter began
the establishment of a hill series through New Jersey (Perrineville,
Monmouth County), with an accompanying valley, the Hightstown Valley,
and extending northeasterly in Long Island in the Mannetto Hills, and
its reciprocal depression, Long Island Sound—or valley. The rivers
issuing from the higher inland country traversed the valleys and the
hills, through the transverse depressions, and reached the ocean almost
in a direct line (Fig. 36). Then followed a later pliocene (Lafayette)
submergence and the deposition of new sediments. The narrow transverse
depressions were filled up, the deeper valley northwest or west of the
lineal hill ridge was not, and with re-elevation the former outward
flowing rivers would be deflected into this trough, failing to recover
their ancient channels that crossed the coastal plain to the ocean. In
this way the littoral rivers would have been (and some southward
tilting of the drainage basin may be invoked) turned southwesterly down
the vale, behind the wall of hills, and "finally escaped seaward
through the partly filled depressions of lower transverse stream
valleys." And Fig. 37 shows this changed result, which probably
remained constant with deepening channels and more and more
accentuated drainage, the small streams forming on the eastern slopes
of the hill ranges being unable to capture again these swelling trunk
lines of flowage.
Thus,
the Connecticut and Housatonic Rivers turned westward into the Long
Island Sound depression, and regained the ocean by the Hudson River
canon; the Delaware River also turned sharply, and finally flowed into
Delaware Bay; the Susquehanna River turned southerly and became
confluent with the Potomac; and the Potomac, instead of crossing
Maryland, submitted to the lateral thrust and entered Chesapeake Bay.
Succeeding
the previous formations the great Ice Age dawned, and a varied series
of Quaternary deposits completed the outline and raised the
superficies of Long Island. Thei coarser, more obvious, and latest
features of this re-
