The Lambertville record. [volume] (Lambertville, N.J.) 1872-1968, 1874-07-22
MISCELLANY.
For THE RECORD.
THE PHYSICAL GEOGRAPHY OF THE
SOUTH ERN PORTION OF
HUNTERDON co.
NO. 2.
BY DR.. C. W. LARSON.

In our last article, we stated that the GEN.
trail part or core of the Sourland Mountain
consisted of hugo dyke of Basaltic trap, ex-
tending from the banks of the river Delaware
at Wells Falls to the culminus known as the
Overlook, in Somerset county.
The rock that TANKS this Trap on either
side is very hard, blush in color, and breaks
when struck with conchoidal fracture. 1t is
the ordinary red-shale hardened by the influ-
ence of heat
In order that this whole subject may be the
better understood. allow us to theorize for a
mdfnerit or so. The red-shale rock forming
the basis of this entire neighborhood-
much larger region of country, for it en-
tends in this State from a line drawn from
Staten Island sound to the Delaware, just
above Trenton, northward to q line drawn
from the northern limit of the Palisades on
the Hudson to the mouth of the Musconet-
cong creek on the banks of the Delaware-was
deposited at the bottom of lake or lagoon,
in layers for the most part very thin, and very
uniform throughout. This great lake or la
Coon which once occupied the region which is
now the red-shale formation, had sloping sides
from the South East towards the North West,
and from the North West towards the South
East. Upon the North West lay the elevated
ridges the most southerly of which rose up
perpendicularly, sloping to the North, but up
on the South East lay an area of land broad
and gently inclined towards the lake. The riv-
ers and streams of this region gently flowing
North. West poured their waters into this pool.
As season succeeded season, and storm sue
ceeded storm, through countless years the
freshets of these streams carried down from
hillside and valley a large quantity of the
mud, sand, gravel and powders of these re-
giohs, which more or less rapidly, according to
their specific gravity, settled to the bottom,
forming layer varying in thickness in pro-
portion to the amount of matter deposited
and the extent over which it was spread
Thus each successive freshet formed layer
upon the South East side of this lagoon, and
helped to fill it up. To be sure, the quantity
of sediment brought down by each freshet
was small as compared with the extent of
the pool.a was capable when spread out ov-
er the whole southern slope, of making layer
sometimes less than a quarter of an inch in
thickness, as may be seen almost anywhere by
examining the laminae of the rocks along the
roadside, yet this lamina, however thin, made
the area Of the pool just SO much less, until
lamina succeeded lamina in countless numbers
and the whole space was filed up. Thus all
the successive layers OF laminae forming our
red-shale or Triassic rocks slope or dip toward
the N. W., and the angle of the dip is very
uniform throughout its whole extent, as may
be seen by inspecting the Table Of Dips
found in the Geology Of N. j., pages 1876 to
100, as reported by Prof. George H. Cook.
Thus we may account for the circumstance
that all the layers of the red-shale of this re-
gion dip towards the N. W., that the S. East
edge of each comes to the surface of the
ground, while the N. W.. extremity dips down
beneath other layers to an untold extent. Had
the deposition taken place upon the bottom of
a lagoon that was exactly horizontal, the lay
ers would have been horizontal, and they
would have SO remained, unless disturbed by
some volcanic agency, of which there is not
sufficient evidence.
Now at some time, subsequent to the depo-
sition of this red-shale, at the time of some
crest CONFUSION of the earth, the rock imme-
diatcly underlying this formation has been
cracked, has been rent asunder, and the mol
ten material of the centre Of the earth inject
ed into the assure until it reached the laminae
Of ped-shale, when, pressing against this, it
found its way to the surface more easily by
following between the layers and pressing
them apart than it would have done by di-
rect vertical fracture. This injected molten
material cooled, solidifed, and became our