Thus the present flat plain was formed and the old valley floor, a local peneplain developed on the limestone, was hidden.
On the other hand, the northwest-southeast drainage lines across the strike of formations, coincide with the slope toward the sea of the uplifted peneplain whose dissected surface is represented by the crests of the uplands.
This plain, like all the others in this region, is a local peneplain developed on soluble limestone.
The horizon of the peneplain passes from the Tertiary and Cretaceous tableland to level masses of crystalline rock, the contour of which has been almost entirely effaced.
Like the deep decomposition-soils in moister regions, it indicates a peneplain on which erosion has ceased.
The topography of northern New Jersey may be briefly described as made up of valleys and lowlands that have been etched in the now elevated surface of what may be called the Schooley peneplain on the Cretaceous baselevel.
A few words may be allowed me concerning these terms, peneplain and pastplain.
Some shore-line cutting must have been done at the margin of the Highlands during Cretaceous time, but the generally rolling surface of the old peneplain leads me to ascribe its origin chiefly to subaërial wasting.
Triassic portion of the peneplain is submerged, and the shore-line of the transgressing ocean has reached the margin of the crystalline rocks.
The cover of Cretaceous sediments was laid on the southeastern part of the old peneplain during a moderate submergence of its seaward portion, before the elevation and tilting above mentioned (fig.
The Schooley peneplain is indicated by the crest and summit altitudes of Kittatinny Mountain, the Highland plateaus and the trap ridges.
Distant views suggest that the Tattoosh Mountains have been sculptured from a plateau, probably an upraised peneplain in which there existed a great mass of igneous rock rounded by less resistant Tertiary sediments.
This peneplain was later upraised into a plateau and its downward inclination towards the east increased.
Swamps and peat bogs are abundant on its undrained surface, and to this drift sheet belong the lake lands of our northern states and of the Laurentian peneplain of Canada.
Peneplain surrounded by Monadnocks, Piedmont Belt, Virginia From Davis' Elementary Physical Geography] =The cycle of erosion.
The end of this long era found here a wide peneplaincrossed by sluggish wandering rivers and overlooked by detached hills as yet unreduced to the general level.
Even surfaces developed on rocks of discordant structure, such as the Piedmont shows, are produced by long denudation, and we may consider the Piedmont as a peneplain formed by the wearing down of mountain ranges, and recently uplifted.
The age of the Mesozoic peneplain is determined from the fact that the lower Tertiary sediments were deposited on its even surface when at the close of the era the peneplain was depressed along its edges beneath the sea.
As an example of an ancient peneplain uplifted and dissected we may cite the Piedmont Belt, a broad upland lying between the Appalachian Mountains and the Atlantic coastal plain.
Manifestly this upwarp occurred since thepeneplain was formed; it is later than the Mesozoic, and the vast dissection which the peneplain has suffered since its uplift must belong to the successive cycles of Cenozoic time.
We have already studied a very ancient peneplain whose edge is exposed to view deep on the walls of the Colorado Canyon (nu', Fig.
On the eastern side of the continent, as we have seen, a broad peneplainhad been developed by the close of the Cretaceous.
This immense area, which we have already studied as the Laurentian peneplain (p.
This immense area may be regarded as an ancientpeneplain truncating the bases of long-vanished mountains and dissected after elevation.
Dissected Peneplain of Southern New England] The surface of the ancient Piedmont plain, as it may be restored from the remnants of it found on the divides, is not in accordance with the structures of the country rocks.
Should you expect the velocity of an earthquake to be greater in a peneplain or in a river delta?
In Pennsylvania and the states lying to the south the Mesozoic peneplain lies along the summits of the mountain ridges.
They appear to correspond with the level of the first peneplain recognized in the Devil's lake region.
Many of the isolated hills on the peneplain east of Camp Douglas are perhaps due to superior resistance, though the rock of which they are composed belongs to the same formation as that which has been removed.
Thus a new cycle of erosion was begun, and the uplifted peneplain was dissected by the quickened streams which sank their valleys promptly into the slightly resistant sandstone.
At the time of its development, this peneplainwas but little above sea level, for this is the only elevation at which running water can develop such a plain.
Slowly but surely, unless there be a renewal by an upbuilding power, the range is cut down until little or nothing of it remains well above sea level, or, in other words, until a peneplain is developed.
Then, too, some change of level between the land and the sea is very likely to take place before the peneplain stage is reached.
The normal cycle of erosion which, as outlined above, tends toward the peneplain condition may be interrupted at any stage by other processes.
This even sky line marks approximately the surface of what was a peneplain late in the Mesozoic era.
Early in the succeeding Cenozoic era, the broad peneplain was notably upraised to nearly the present altitudes of the ridge tops.
The amount of uplift (unaccompanied by folding) of the peneplain was commonly from a few hundred to a few thousand feet with the greatest amount in general along the main trend of the Appalachians.
The remarkably even sky lines of these regions mark the peneplain level before the uplift took place, and occasionally masses, called "monadnocks" from Mount Monadnock in southern New Hampshire, rise above the general level.
The fact should be emphasized that nearly all the principal topographic features of the great upraised region have been produced by dissection (erosion) of the uplifted peneplain surface.
The valleys in such an uplifted peneplain region have been carved out by streams since the uplift began.
How may a plain of marine abrasion be expected to differ from a peneplain in its mantle of waste?
Along the Atlantic coast the Mesozoic peneplain may be traced shoreward to where it disappears from view beneath an unconformable cover of early Tertiary marine strata.
The widened rock bench forms when uplifted a plain of marine abrasion, which like the peneplain bevels across strata regardless of their various inclinations and various degrees of hardness.
This upland is an uplifted peneplain of subaerial denudation,[2] now so far advanced in a "second" cycle of weathering and so thoroughly dissected that to an untrained eye it appears to be only a country of hills confusedly arranged.
In the great plains of North America two of the divisions, that is, the Atlantic coastal plain of the southeast and the peneplain of the northwest, owe their present form to the forces of erosion.
The Piedmont plateau, which lies at the eastern foot of the Blue Ridge, is not really a plateau but a peneplain or ancient lowland worn almost to a plain.
Wonderful as these gorges certainly are, the Piedmont plain or the northwestern peneplain is far more wonderful.
From South Dakota and Nebraska northward far into Canada and westward to the Rocky Mountains there extends an ancient peneplain worn down to gentle relief by the erosion of millions of years.
Yet in spite of these handicaps the northwestern peneplain with its vast open stretches, its cattle, its wheat, and its opportunities is a most attractive land.
