inherited from a Cretaceous cover, which formerly stretched over
Connecticut for a considerable distance, but of which no traces now
remain in the state. On parts of Long Island the Cretaceous deposits
are found, and it is not inherently impossible nor improbable that they
once stretched far over the main land. In New Jersey[46] several lines
of evidence seem to show that the Cretaceous beds formerly extended
across the Triassic, probably to the margin of the highland plateau.
The curious drainage of the Watchung Crescent is one evidence of this,
but the other proofs are along entirely different lines, so that
there is apparently good evidence that the Cretaceous beds extended
twenty-five miles or more farther inland. If, in the time which has
elapsed since the deposition of these beds, there has been erosion
sufficient to strip them off from such a broad area in New Jersey, may
they not, in Connecticut, under presumably similar conditions, have
been equally eroded?
There is much which makes this hypothesis attractive, and, as the
facts were first studied, it seemed the most likely one. It affords
a good explanation, not only for the courses of the Housatonic and
Connecticut, but also for other rivers along the sound. It seems, also,
at first thought, to be well supported by analogy from New Jersey.
But a closer study of the situation in that state reveals marked
differences in the attendant circumstances. There the soft Triassic
sandstone must have been worn down to a lowland early in the Cretaceous
cycle, perhaps by the close of Jurassic time or thereabouts, while the
harder crystallines retained a strong relief. The slight subsidence,
which marked the beginning of marine Cretaceous in New Jersey, allowed
the Cretaceous sea to transgress rapidly the baseleveled sandstones to
the foot of the crystalline hills, but not to cover them to any extent.
It is not probable that the crystallines in Connecticut had been
brought nearer to baselevel than those in New Jersey at the time of the
Cretaceous deposits. There is no evidence to show that the subsidence
was greater in Connecticut than in New Jersey, and, therefore, from _a
priori_ considerations, the conclusion would seem to follow that the
subsidence, which permitted the Cretaceous sea to cover the Triassic
sandstone area of New Jersey, was not sufficient to permit the sea to
cover the then unsubdued crystalline hills of Connecticut. Although
this hypothesis is not to be hastily thrown aside, for theoretical
reasons, yet it would seem necessary to hold it very lightly, at
least until some positive proof is found of the former existence of
the Cretaceous or some later formation in that region. The first
suggestion, that the lower Connecticut was a consequent river in the
Cretaceous cycle and was revived by the post-Cretaceous uplift, is, at
the present state of knowledge, the most probable.
_The Farmington._ The roundabout course of this river presents another
interesting problem, which is not free from difficulties. From its
source in Massachusetts it flows southeast across the crystallines
to the village from which it takes its name, where it turns abruptly
north along the Triassic sandstones for ten or twelve miles, when with
another wide sweep it crosses the trap ridges at Tariffville by a deep
gorge, and resumes its southeasterly course to the Connecticut. Of this
latter part I will speak later, but now arise the questions, “what
has been the history of this river,” and “why does it turn north at
Farmington?”
_The Farmington in the Tertiary cycle._ A course more accordant with
the structure would seem to be south along the Quinnipiac and Mill
river valleys to the sound at New Haven. As has been said before
(page 376), Prof. Dana has expressed the opinion that the gorge at
Tariffville was occupied by the Farmington in Tertiary times, and that
the Westfield river gap further north and the gorge of the Quinnipiac
southwest of Meriden are also of earlier date than the glacial epoch.
One reason has also been given why I differ from him in regard to
the Quinnipiac and Tariffville gorges--they are narrower and steeper
than those made in similar rocks during the Tertiary cycle. But more
than this, the constructional topography, resulting from the tilting
and faulting of the region, could not, it would seem, have caused
the Farmington to take its present course. Even if it had taken
this roundabout course during the baseleveling of the country, it
must, since it would have had to cross three trap sheets, have been
captured and led to the sea by the shorter and easier way along the
sandstone area. The fact that the Connecticut probably persisted in
its consequent course is no argument for similar conditions for the
Farmington, because the latter is much the smaller stream, and so more
easily captured. Nor could the river have been forced into this course
during or after the post-Cretaceous uplift, for the land was then
raised more at the north than at the south, and any changes from this
cause would have been to confirm the river in its southward course. It
is very probable, therefore, that in at least the latter part of the
Tertiary cycle, the Farmington did not have its present course, but
followed the open sandstone valley, along the course of the Quinnipiac
and Mill rivers of to-day. The earlier history of this river is purely
conjectural; one fact may shed a little light upon it, a fact which may
indicate that this course was an adjusted one taken during Tertiary
times.
_In pre-Tertiary times. Origin of Cook’s Gap._ A few miles southeast
of where the river emerges from the crystallines, the trap ridge is
cut by a deep wind notch--Cook’s Gap--through which the New York and
New England Railroad passes west from New Britain. As was pointed out
some time ago by Prof. Davis,[47] this is not a fault gap, because the
alignment of the ridge is not broken, but it is probably an abandoned
water gap, the head-waters of the stream which formerly occupied it
having been abstracted by a rival, which did not have to cross a
hard trap ridge. Perhaps this river was the ancestor of the present
Farmington, and in that case its history would seem to have been
as follows. A stream consequent upon the constructional topography
after the faulting and tilting at the close of the Triassic, it had
its upper course on the crystallines, its lower on the sandstones
and buried trap sheets. In its old age it crossed by a shallow gap
the trap sheet, which had been uncovered by erosion. In the second
or Tertiary cycle it was simply a revived stream quickened to a new
life by the post-Cretaceous uplift of the peneplain. This uplift gave
opportunity to a rival stream, which did not have to cross the hard
trap beds to intercept the waters of the old Farmington, and lead them
out by a shorter, easier path, probably down the sandstone valley west
of the trap ridge. The path across the trap was abandoned, and the
notch became a wind gap; the river following its new course, until the
incursion of the ice-sheet interrupted its normal development. This is
of course almost entirely speculative. Cook’s Gap is best explained as
an abandoned river gap; the Farmington is the nearest river of a size
proportional to the size of the gap, and the hypothesis is a rational
one. There is, however, no direct evidence that the Farmington once
occupied Cook’s Gap.
_The Tariffville cut._ Before attempting to answer the second question,
“why the river flows north at Farmington?” let us consider for a moment
the history of the Tariffville cut. The river occupies a gorge whose
sides are steep and talus covered, but which is not at all clogged with
drift. There is naturally no room at or near the water level, even for
the wagon road, place for which has been blasted near the top of the
gorge. The profile of the gap shows a gentle ascent from the top of the
gorge, up to the nearly level crest line of the ridge. That is to say,
the recent gorge has been cut in the bottom of a sag in the ridge. We
have already given our reasons for believing that the gorge here is
much younger than the Westfield river gap; that it is a part of the
work of the next cycle; that it is post-Tertiary. The sag, however, in
the bottom of which the gorge is cut, is clearly of the earlier cycle.
The bottom of the sag is much above the level to which the rivers had
cut their valleys in the late Tertiary, and, therefore, it is certain
that a river could not have occupied it at the close of that cycle.
It was probably an abandoned water-gap whose stream had been captured
in the same way and in the same cycle as the river, which formerly
occupied Cook’s Gap.
The fact that the sag and gorge, although located very near a fault
line, do not correspond to it, but are transverse and independent of
it, is instructive and needs a moment’s attention. It seems probable
that the stream consequent upon the faulted blocks would have flowed
down the slope of the tilted block and then along the fault line at
the foot of the fault cliff and would have held this course during
the baseleveling of the country. When the area was baseleveled
the stream must have swung from side to side in its broad flood
plain, and thus departed from the fault line. When it was revived
by the post-Cretaceous uplift, it was confined to the course it had
unwittingly taken on the sandstones just above the hard ridge, and
it was forced to cut down through the trap. Subsequently a rival,
which did not have to work against this obstacle, abstracted its head
waters and the gap was abandoned. The accompanying diagrams may make
this easier to understand. Figure 3 is a cross-section of the faulted
monocline, R showing the position of the river along the foot of the
fault cliff. The line B L represents the surface of the country after
baseleveling, the trap outcrops forming _low_ hills (much exaggerated
in the diagram). Figure 4 shows the dislocated trap sheets, the fault
line and the winding course of the river, which has abandoned the
fault line except where it passes between the low trap hills. Here
the country is at baselevel. Figure 5 represents the region after the
elevation and resulting erosion. The trap ridges have become more
pronounced, and have migrated eastward in the direction of the dip. The
river has been slowly let down upon the northern one from the sandstone
at point G and has there cut into the solid trap.
[Illustration: FIGURES 3–5.]
The transverse notch of Cook’s Gap, already described, was probably
located in a somewhat similar manner, but the case is not so clear as
at Tariffville.
_Gravel terraces of the Farmington._ A consideration of some facts
concerning the height and slope of the terraces along this part of the
river may give a clue to the answer to our question. One-half a mile
east of Tariffville and east of the trap ridge, the highest terrace is
210 to 215 feet. Half a mile south of the same place but west of the
ridge the height is 275 feet.[48] The top of the gorge at Tariffville
is about 190 feet above the sea-level. It does not seem probable that
these highest terraces were ever continuous over all the Farmington
valley. But if they represent the level reached by the maximum flood
accompanying the melting of the glacier, the great difference in their
height on the two sides of the trap ridge, in connection with the
other evidence already noted, gives strong reason for believing that
the gorge as it exists to-day had not then been cut. A mile and a half
east of Tariffville there is a lower terrace which is wide-spread. Its
general height is about 190 feet, in places a little more. In this
terrace the lower part of the Farmington has cut a trench 90 to 100
feet deep. The shape of the valley makes clear the fact that before
this trench was cut the river flowed at about the 190 foot level, which
is the height of the bottom of the sag at Tariffville. On the west side
of the trap ridge there is also a more or less wide-spread terrace
at about the same height. It seems very probable therefore that the
river was raised to the level of the old sag in the trap ridge by the
building of these terraces.
The present average southward slope of the highest terraces west of the
trap ridge from Northampton, Mass., to Farmington, Conn., forty-four
miles, is seven inches per mile,[49] and Professor Dana is inclined to
believe that this is approximately the slope at the time the terraces
were built. The character of the deposits shows that the current
which formed these deposits flowed south. The present river, flowing
north, falls twenty feet between Farmington and Tariffville, or 1⅔
feet per mile. The reversal of the river was probably determined by
two factors. Near the village of Farmington, the waters of 200 square
miles of territory are poured into the valley by the upper Farmington
and its tributary, the Pequabuck. During the terrace building stage
the great mass of débris contributed by these streams was deposited
where the steep gradient of the highlands was exchanged for the gentle
slope of the lowland. The main north and south valley was thus choked
by the débris of its tributaries and a long stretch of comparatively
still water extended north from Farmington, in which nearly horizontal
deposits were made. South of Farmington the terrace deposits are
much coarser than to the north, and the face of the terraces is much
greater. It is not impossible that, as the deposits between Farmington
and the Massachusetts state line approached nearer and nearer to
horizontality, the waters of the upper Farmington began to divide, part
flowing north and part south, the northward flowing portion finding an
outlet at the sag at Tariffville. If this was the case, the terraces
between Farmington and Tariffville must have had a slight slope to the
north. Their present southward slope could readily be accounted for by
the re-elevation of the land after the disappearance of the ice. This
explanation rests upon the ability of the upper Farmington and the
Pequabuck to have completely dammed the southward flowing current and
turned it northward by the great mass of their deposits. If this was
not the case, and there may be some doubt on the matter, the subsidence
which accompanied the later stages of the ice-retreat is the other
factor in the problem. It is estimated that an average depression of
1.25 feet[50] through the Connecticut valley would restore it to an
altitude approximating that at the close of glaciation. It seems highly
probable that these terrace-deposits were built before the maximum
depression was reached. If this was the case, the depression would be
efficient in reversing the Farmington, and this factor would supplement
the first. It is impossible at present to say to what extent these two
factors enter into the problem. That they are not mutually exclusive
is evident, and that they are together quantitatively competent seems
certain. Among the several hypotheses which have been considered, this
seems the most probable, and in the light of the present evidence the
most rational.
At first thought it might seem that if the Farmington was reversed by
the differential subsidence of the land, the Connecticut ought to have
suffered a similar fate, and since it did not, the explanation cannot
apply to the Farmington. But the terraces of the Connecticut have a
much greater southward slope than those on the smaller river, and the
depression was not sufficient to reverse the stream. The conditions on
the two sides of the trap ridge were not the same.
To sum up, then, the history of the Farmington seems to have been
as follows: Its original consequent course was southeast on the
crystallines and perhaps across the trap ridge at Cook’s Gap, from
which course it was turned in the Tertiary cycle by a stream whose
course was approximately that of the Mill river of to-day. The damming
of the valley by the deposits of the Upper Farmington, and the
depression in the north accompanying the ice retreat, reversed the
river at Farmington, and it took a new course on the terrace deposits,
escaping by the sag in the trap at Tariffville into the Connecticut
valley.
_The Quinnipiac._ The gorge of the Quinnipiac, already mentioned
several times, seems closely comparable to the gorge of the Farmington.
It is not of the Tertiary cycle, and is best referred to the
inter-glacial or post-glacial epochs. We should expect the Quinnipiac,
instead of turning eastward, to cut through this sandstone ridge, to
continue southward along the Mill river valley. Dana[51] finds from
the heights of the terraces that the drainage of the terrace-building
period was not along the Quinnipiac, but along the Mill river, and
concludes that the Quinnipiac gorge was obstructed by an ice-dam. I
have not as yet studied it enough in detail to do more than express the
opinion here reiterated, that this gorge is later than the cycle in
which the open sandstone lowland on either side of it was excavated.
Its topographic form would put it in the cycle which has been called
post-Tertiary.
_The Scantic._ In the Scantic we have a typical example of a river
whose lower course is manifestly of a later date than the upper. In
this it is similar to several of our Atlantic rivers, notably those of
North Carolina, whose upper courses are on the Piedmont crystallines,
being probably established previous to the Cretaceous baseleveling, and
whose lower courses stretch seaward over the unconsolidated Tertiary
deposits of the coastal plain. As the plain of these recent deposits
emerged from the sea, the rivers were forced to extend their courses
eastward over the freshly raised surface to the retreating shore
line. The Scantic river has a similar history. Its upper course in
southern Massachusetts on the crystalline plateau is a remnant of the
drainage established before Cretaceous baseleveling and revived by the
subsequent uplift. How much that revived drainage has been modified by
drift can only be determined by long field study, but the topography,
as read from the topographical atlas would seem to indicate, that it
has not been much. The valleys were undoubtedly clogged with drift, and
the drainage area may be somewhat modified, but the drainage seems to
be substantially along the same lines.
Just below the village of Hampden, the Scantic leaves the plateau
and enters the Triassic lowland. From this point to its mouth at the
Connecticut, opposite Windsor, a distance of twenty miles, it flows
nearly all the way through the gravel, sand and clay deposits of the
period of ice-retreat. The topography of the lower course of the river
is entirely characteristic of a stream which has recently attacked a
level, easily eroded district. The inter-stream surfaces are broad and
flat; the descent to the stream bed which is sunk seventy or eighty
feet below the general surface is exceedingly steep. These two lines,
that of the inter-stream surface and that of the valley side, meet at
a sharp angle. The side streams are as yet very short, and have cut
narrow gorges down to the main river. Tributary to them are deep side
ravines, whose bottoms ascend rapidly to the inter-stream surface, the
whole making a dendritic system of drainage in its earlier stages. The
Scantic, having reached base level in its lower course, has developed a
narrow flood-plain.
Manifestly this part of the river valley is of much later date than
the upper part. If, during the period of ice-retreat, the lower
Connecticut valley was an estuary, the Scantic was a much shorter river
than at present. Its mouth could not have been far from the point
where now it leave the crystallines, but as the land was elevated and
estuarine conditions gave place to fluviatile, the Scantic lengthened
“mouthward,” consequent upon the minor inequalities of the newly made
beds. The effect would be substantially the same if the terraces
were built by great valley floods, as Dana supposes. In pre-glacial
times this river, in common with several other rivers rising on the
crystallines and flowing into the Connecticut, had courses of various
lengths over the Triassic sandstones, but these old valleys are lost
entirely, the later trenches in the terrace deposits being altogether
independent of them.
_Other examples._ The lower Hockanum, Farmington, Park, and the entire
length of many short streams are similar to the lower Scantic, and
originated under similar conditions. Stony Brook, a little stream
north of Windsor Locks, presents the same features, but with this
variation: It is superimposed through a thin layer of drift upon
the sandstone, into which it has cut a deep, picturesque gorge. The
Hockanum and Farmington are also “locally superimposed” in a few
places. The Connecticut, also, north of Middletown, although following
its pre-glacial valley, has departed in numerous places from its former
bed, and has cut down through the valley-filling onto ledges of rock
beneath. The water-power at Enfield, Conn., and at Turner’s Falls and
Bellows Falls, Mass., is the result of this superimposed position.
_Abandoned gaps._ Many abandoned water-gaps must exist among the hills
of the state. Cook’s Gap, through which the New York and New England
Railroad crosses the trap ridge, three miles west of New Britain, has
already been discussed. It must not be confounded with the majority
of the other gaps in the trap ridge, which are oblique, break the
alignment of the ridge, and are due to faults.
The New York and New England Railroad in ascending to the eastern
plateau passes through Bolton Notch, a few miles east of Manchester.
This notch, also, is an abandoned river bed but, as it seems, abandoned
at a later date and for another reason than that assigned for Cook’s
Gap. The drift is very heavy in this region, and the most probable
explanation is that the post-glacial streams do not altogether follow
pre-glacial valleys. This gap, used by turnpike and railroad, testifies
of another and older drainage system.
That in this brief article all the problems connected with the
Connecticut rivers have been solved, or even noted, is not to be
expected. It is hoped, however, that the work done may prove a help to
further study of the same regions, and that the tentative conclusions
advanced may be substantiated by further investigation.
HENRY B. KUMMEL.
FOOTNOTES
[33] The author desires to express his obligation to Professor
W. M. Davis for aid in the preparation of this article. It
was first written under his direction and with the help of
his suggestions when the author was in the graduate school of
Harvard University. Prof. Davis is not responsible, however,
for the statement of the views herein advanced, although in
general it is believed that he is in accord with them.
[34] Amer. Jour. Sci. 3d ser., vol. xxxvii, 1889, p. 423. Bull.
Geol. Soc. Amer., vol. ii, p. 545.
[35] The rough diagrams accompanying this paper may aid the
reader who is unacquainted with the details of the region
under discussion. The abbreviations on the above figure are
as follows: C. The Connecticut. Cr. Pl. Crystalline plateau
(the shaded area). F. The Farmington. H. Hartford. Ho. The
Housatonic. Lm. Limestone area. M. Meriden. Mi. Mill River. Mt.
Middletown. N. The Naugatuck. N. H. New Haven. No. The Norwalk.
Q. The Quinnipiac. Qg. The Quinnebaug. S. The Scantic. Sa. The
Saugatuck. T. Tariffville. Th. The Thames. The unshaded area
is the Triassic sandstone lowland, and the blackened areas
represent the ridges of the faulted trap sheets.
[36] Am. Jour. of Sci., 3d ser., vol. xxxvii, p. 430.
[37] Bulletin of Geol. Soc. of Amer., vol. ii, p. 554.
[38] It is not desired to affirm that these periods of erosion and
elevation began and ended promptly with the beginning or end
of a period. The time statements must be considered as only
approximate.
[39] An exaggerated idea must not be had of the steepness and
narrowness of these crystalline valleys. The valley of the
Farmington, five miles up from where it opens into the Triassic
sandstone, is 400 to 500 feet deep, and a mile and a half wide
at the top. The Connecticut valley, just below Middletown, is
about 400 feet deep and two miles wide at the top. These are
fair representatives of the valleys in the crystalline rocks in
the central part of the state.
[40] Amer. Jour. of Sci., vol. x, 3d ser., 1875, p. 506.
[41] McGee. Amer. Jour. Sci., 3d ser., vol. xxxv, p. 376.
[42] Davis and Wood, Geographic Development of Northern New Jersey,
pp. 413, 414.
[43] “Rivers and Valleys of Pennsylvania,” Davis, W. M., published
in The National Geographic Magazine, in 1889.
[44] Davis, W. M., “Geographic Development of Northern New Jersey,”
p. 397–8.
[45] Davis, W. M., Amer. Jour. of Sci., 3d ser. vol. xxxvii., 1889,
p. 432.
[46] Geog. Devel. of Northern New Jersey, p. 404 et seq. Proc. Bos.
Soc. Nat. Hist. Also Rivers of Northern New Jersey, p. 11 et
seq. National Geographic Magazine, vol. ii, p. 93.