the Connecticut River Valley
By Prof. Richard D.
410 miles from near the Canadian border to Long Island Sound, the
Connecticut River, New England's longest and widest river, runs
to the sea. Along the way it marks the boundary between New Hampshire
and Vermont and slices prominently across Massachusetts and its
namesake, Connecticut. It is truly a river that "connects".
It is a very diverse river that sometimes flows quietly, meandering
over a broad, fertile floodplain, and at others rushes over prominent
waterfalls and rapids (important waterpower locales) or through
beauty of this river has long been noted. Former Yale President
Timothy Dwight wrote the following in the early 19th century: "This
stream may, with more propriety than any other in the world, be
named THE BEAUTIFUL RIVER. ...The purity, salubrity and sweetness
of its waters; the frequency and elegance of its meanders; its absolute
freedom from aquatic vegetables; the uncommon and universal beauty
of its banks, here a smooth and winding beach, there covered with
rich verdure, now fringed with bushes, now covered with lofty trees,
and now formed the intruding hill, the rude bluff and the shaggy
mountain, are objects which no traveler can thoroughly describe
and no reader can adequately imagine." (Quoted in Delaney,
rocks and landscape of the Connecticut Valley region record events
of ancient times from colliding and splitting continents (Paleozoic
and Mesozoic Eras, respectively) to glacial processes (which ended
about 10,000 years ago) in a particularly clear and dramatic fashion.
(Bain & Meyerhoff, 1976; Bell, 1985; Little, 1986, 1994; Raymo
& Raymo, 1989)
(570 - 225 million years ago)
some rocks in the Connecticut Valley drainage are older, dating
back over 1 billion years (Precambrian Era), most of the early geologic
history is involved with the creation of the supercontinent of Pangea
during the Paleozoic. Tectonic plates of the Earth's crust drift
together during the Paleozoic eventually leading to the merging
of North America with Africa and Europe. The collision of these
plates not only closed an early version of the Atlantic Ocean, known
as Iapetus (the father of Atlas in Greek mythology) or the Proto-atlantic,
but also created one of the greatest mountain chains in the world,
Paleozoic rocks of New England record their origins as deposits
in the Iapetus Ocean, either as sedimentary rocks perhaps washed
in by rivers or formed from shells or reefs (we were south of the
equator during much of the Paleozoic), or igneous types from volcanic
eruptions or deep magma chambers where slow cooling produced the
easily seen minerals of granite rock. The heat and pressure of the
collision process transformed these rocks into metamorphic types.
(225 - 65 million years ago)
The Connecticut Valley originated in the Mesozoic. Pangea began
to split, forming the present Atlantic Ocean. Besides the big split
of the Atlantic, many smaller faults cracked the land due to the
stretching stresses. These "rift valleys," similar to
today's Death Valley and others of the Basin and Range, formed the
initial drainage of the ancestral Connecticut Valley.
fault that dominated the Mesozoic rift was located on the eastern
side of the valley, and is known as the Eastern Border Fault that
can be traced from New Haven, CT. to Keene, NH. Rivers rushed into
the rift valley and deposited sedimentary materials, gravel, sand,
and mud. Gravely alluvial fans were major deposits along the mountainous
eastern margin of the old valley, while sandy-muddy floodplain,
shoreline and lake deposits dominated the lower valley elevations.
of the unique aspects of the Connecticut Valley of today is that
sedimentary rock from the processes just described, is easily seen
along the rocky river bends and roadsides in the MA and CT portions
of the valley. Since almost all of New England is composed of metamorphic
rock (due to the Paleozoic collision), these rusty sedimentary layers
from alluvial fans and lake beds provide important geological examples
and evidence of our Mesozoic history, including some world-class
evidence of or remains of ancient life, are abundant in the shales
and sandstones representing deposits in old shoreline and lakebed
environments. Most common are fossils that represent the tracks,
trails, and burrows of insects or other invertebrates. Rarer and
more important are fossils of dinosaurs and fish. "By the middle
of the nineteenth century, the Connecticut Valley had achieved worldwide
acclaim for its paleontology, particularly its reptile footprints
and fishes." (McDonald, 1991, p.91)
are mainly preserved as footprints preserved in the Mesozoic sedimentary
rocks of the Connecticut Valley in MA and CT. Very few bones have
been discovered since bones decay, while each animal can leave countless
footprints along the muddy shores of rivers and lakes. The first
scientific study of dinosaur footprints in the world began in 1835
as paving stones, quarried from along the river in the Turners Falls,
MA area, were being laid in Greenfield, MA. Professor Edward Hitchcock,
geologist, theologian, and president of Amherst College, became
world renown for his three-decade detailed study of the region's
prints (Hitchcock, 1858, 1865). Hitchcock's famous and important
collection of dinosaur prints is now preserved at the Pratt Museum
of Amherst College.
more recent footprint discovery of world importance occurred in
1966 at a construction site about a mile from the river in Rocky
Hill, CT. Dinosaur State Park is now located at this site and under
its broad domed building can be seen an exposed shale bedding plane
with about 500 large (12" - 18") prints. Over 1500 other
prints have also been studied, but are now reburied for preservation.
Dinosaur expert Dr. John Ostrom of Yale states that "The Rocky
Hill site is remarkable in that it is perhaps the largest (more
than 35,000 square feet) known exposure with abundant fossil footprints
preserved on a single bedding plane." "Aside from the
impressive spectacle of so many footprints and such a large expanse,
this site contains an unusual record of a 'single moment' in ..
time." "Rocky Hill can provide us with new information
on animal associations, habits, and movement that cannot be obtained
from other ... sites." (Ostrom, 1968) In fact, Dr. Walter Coombs
determined that some of these carnivorous trackmakers were able
to swim, based on foot and claw impressions in the old lake bottom
another site bordering the river in Holyoke, MA, Ostrom has described
19 trackways that indicate, because of their parallel orientation,
herding behavior. (Ostrom, 1972)
Connecticut River Valley is also the site of a few excellent fossil
fish localities. About 20 productive sites are presently known,
preserved in black shales of old lake beds, and commonly yield whole
specimens (McDonald, 1975), undisturbed by scavengers or wave action
in Mesozoic lakes.
sedimentary feature that is unique to the Connecticut Valley is
the armored mud balls found in Turners Falls, MA and vicinity. Armored
mud balls formed in the Mesozoic sedimentary layers as streams rolled
balls of hard mud downstream. The mud became round as well as soft
and sticky on the outer margin, allowing sand and pebbles to become
attached (the armor). The balls were quickly buried by other stream
deposits and eventually lithified. Lithified armored mud balls have
only been found in about 10 other localities in the world, in old
beach deposits. The Turners Falls area armored mud balls are the
only stream-formed armored mud balls in the world. (Little, 1982)
Excellent examples of these forms are preserved in boulders placed
along the river at Unity Park, Turners Falls, and in the Greenfield
Community College "Rock Park".
flows are dramatic and important Mesozoic events in the Connecticut
Valley and profoundly influence the landscape today. The dark basalt
lavas, called "traprock", flowed out over the Mesozoic
lowlands, commonly reaching over 100 feet in thickness. Today these
flows, tilted by movements along the ancient Eastern Border Fault
and then exposed by erosion, form spectacular ridges that stretch
tens of miles, creating interesting, dramatic vista points and important
upland ecosystems in the middle of the wide valley (Fig. 5). Examples
include the Pocumtuck Range (Greenfield - Deerfield, MA) and the
Holyoke Range that trends east-west about 10 miles from Amherst
to Easthampton, and then southerly for about 60 miles (known as
the Metacomet Ridge) to the outskirts of New Haven.
basalt flows exhibit interesting geologic features such as pillows,
formed by flow underwater, and columns, created by contraction cracks
during cooling. The basalt is an important geologic resource, quarried
for crushed stone and rip-rap.
the end of the Mesozoic Era, 65 million years ago, the Eastern Border
Fault had been inactive for about 70 million years allowing the
valley to become completely filled with sedimentary deposits. Surrounding
areas were smoothed by erosion and all became part of a peneplain,
an erosional plain of regional extent. Several high places resisted
the forces of erosion, and are known as monadnocks, named for a
prominent example of this feature, Mt. Monadnock of southwestern
(65 million years ago - present day)
During the Cenozoic uplift raised the peneplain hundreds of feet,
resulting in prominent down cutting by streams to create the basic
valley forms of seen today. Erosion proceeded faster in the weak
sedimentary rock areas leaving the more resistant rocks higher on
the landscape, thus creating the prominent ridges of basalt lava
mentioned above as well as the highlands (metamorphic rock) on either
side of the Connecticut Valley.
the uplift of the peneplain the Connecticut River's course gradually
developed in a north-south direction, following geologic trends.
However, a prominent divergence occurs at Portland, CT. The river
flows southeast, leaving wide lowlands developed in soft rock of
the Mesozoic rift valley to erode a narrow valley across 30 miles
of hard metamorphic rocks of the eastern highlands to finally end
at Long Island Sound. Since this exit to the sea corresponds with
the trend of the Farmington River, it seems that the Connecticut
appropriated this pathway.
remainder of the Mesozoic rift valley with sedimentary rocks and
lavas continues southerly to New Haven with no river of any consequence.
profoundly affected the region as continental glaciers moved southward
from Canadian source areas. While the Earth has been in the grip
of the Ice Age for about 2 million years, it is the last ice advance,
known as Wisconsinan, that is most important. The Wisconsinan ice
was at its maximum only 20,000 years ago, only "yesterday"
in geologic time. The ice sheet completely covered the Connecticut
River drainage and surrounding areas, ending at the terminal moraine
deposits of Long Island, NY, Marthas Vineyard, and Nantucket, MA.
ice retreat, glacial meltwater deposits filled the Connecticut Valley
in the New Britain - Rocky Hill area to create a dam. As the ice
continued to melt back to the north, water backed up behind this
dam, forming Lake Hitchcock, which, over the course of about 4,000
years, gradually extended up the Connecticut River drainage as far
north as West Burke, VT, a distance of about 250 miles. Approximately
12 or 14,000 years ago Lake Hitchcock drained, allowing the Connecticut
River to once again flow across its valley.
deposits filled Lake Hitchcock. Deltas were built into the lake
by both tributary streams glacial meltwater. (Meltwater deltas are
known as kame deltas.) These deposits are important sand and gravel
deposits as well as aquifer zones. Lake bottom areas accumulated
mud in annual layers called "varves". The varves can be
counted and correlated like tree rings and help to trace the timing
and events that shaped the lake. They also were the source of the
valley's former brick industry, and are mined today for landfill
lining and capping.
climate remained cold enough to create permafrost in the soil after
Lake Hitchcock drained. One of the permafrost features of significance
is the pingo. Pingos are volcano-like ice blisters, perhaps 50 feet
high. When the ice melted, shallow lakes remained on the landscape
and some are even seen today, over 12,000 years later.
draining, the Connecticut River and tributaries cut through the
Hitchcock deposits, creating terraces and floodplains that are prominent
features of today's landscape. Remnants of Lake Hitchcock's shoreline
and lake bottom are also preserved as terrace levels high above
the river. The stone-free, productive bottomlands that makes the
Connecticut River Valley an agricultural paradise is due to this
combination of old lake bottom clay capped by fluvial flood deposits,
supplemented by the groundwater resources of nearby aquifers.
places the Connecticut River was not able to find its preglacial
course after Hitchcock's drainage, and instead of a wide, floodplained
valley, the river found itself flowing over bedrock creating waterfalls
and rapids, or coursing through a narrow valley. At its mouth, the
river has been flooded by the sea, a consequence of glacial melting
and worldwide sea level rise. In fact the lower river is an estuary,
with tidal effects as far as Hartford. Extensive marshland dominates
the river's end -- the only major American river not having a city
at its mouth (Stekl & Hill, 1972), and beaches built at least
in part from the river's flow, form final deposits as land and sea
connect (Patton & Kent, 1991).
unique combination of geology and landforms gives the Connecticut
River Valley an outstanding landscape diversity. Its an excellent
natural laboratory for exploration and recreation.
G. and Meyerhoff, H., 1976, The Flow of Time in the Connecticut
Valley: Geologic Imprints, CT Valley Historical Museum, Springfield,
MA, 168 p.
Michael, 1985, The Face of Connecticut, Bull. 110, State Geol. and
Nat. Hist. Surv., Hartford, 196 p.
Walter P., 1980, Swimming ability of carnivorous dinosaurs, Science,
v. 207, p. 1198-1200.
Edmund, 1983, The Connecticut River, New England's Historic Waterway,
Globe-Pequot, 182 p.
J. and Colton, R., 1967, Geology of the southern part of glacial
Lake Hitchcock and associated deposits, in Robinson, P., ed, Guidebook
to field trips, New England Intercollegiate Geological Conf., Amherst,
MA, p. 73-88.
E., 1858, Ichnology of Massachusetts, W. White State Printer, Boston,
1865, Supplement to the Ichnology of New England, Wright and Potter,
State Printers, 96 p.
J., 1978, Paleosol caliche in the New Haven Arkose, Newark Group,
CT, Palaeogeog. Palaeoclim. Palaeoecol., v. 24, p. 151-168.
C., 1985, West Rock to the Barndoor Hills: The Traprock Ridges of
CT, State Geol. and Nat. Hist. Surv., Vegetation of CT Natural Areas
no. 4, Hartford, CT., 60 p.
Richard D., 1982, Lithified armored mud balls of the lower Jurassic
Turners Falls Sandstone, north-central MA, Jour.Geology, v. 90,
1986, Dinosaurs, Dunes, and Drifting Continents: The Geohistory
of the Connecticut Valley, Valley Geology Publications, 107 p.***(This
book is being significantly revised and will be available (tentatively)
1994, The Flow of Time: 500 million years of Geohistory in the Connecticut
River Valley, 35 min. videorecording, Pioneer Valley Institute,
Greenfield Community College, Greenfield, MA
Nicholas, 1975, Fossil fishes from the Neward Group of the Connecticut
Valley, MA Thesis, Wesleyan Univ., Middletown, CT, 230 p.
1991, Paleontology of the Early Mesozoic (Newark Supergroup) Rocks
of the Connecticut Valley, in Mattson, L., ed., Geology of Western
New England -- Field Trip Guidebook and Proceedings, Nat. Assoc.
Geol. Teachers, Eastern & New England Section Ann. Mtg., Greenfield
Comm. Coll., Greenfield, MA, 131 p.
P., 1986, A 40-million-year lake record of early Mesozoic orbital
forcing, Science, v. 234, p. 842 - 848.
P., McCune, A, Thomson, K., 1982, Correlation of the early Mesozoic
Newark Supergroup by vertebrates, principally fishes, Am. Jour.
Sci, v. 282, p. 1-44.
J, 1968, Geology of Dinosaur Park, Rocky Hill, CT, in Orville, P.,
ed., New England Intercollegiate Geological Conference Guidebook,
Guidebook No. 2, CT Geol. and Nat. Hist. Surv., Hartford, CT, p.
1972, Were some dinosaurs gregarious?, Palaeogeog. Palaeoclim. Palaeoecol.,
v. 11, p. 287-301.
P. and Kent, J., 1991, A Moveable Shore: the face of the CT coast,
Duke Univ. Press, 159 p.
C. and Raymo, M., 1989, Written in Stone: A Geological History of
the Northeastern United States, Globe-Pequot, 163 p.
W. F., & Hill, E., 1972, The Connecticut River, Wesleyan Univ.
Press, 143 p.
J. and Ashley, G., Ice-wedge casts, pingo scars, and the drainage
of Lake Hitchcock, p. 305-331, in Robinson, P. and Brady, J., eds,
Guidebook for field trips in the Connecticut Valley Region of MA
and adjacent states, 84th Annual Meeting, New England Intercollegiate
Geological Conf., 1992, Contrib. 66, Univ. of MA Dept. of Geol.
and Geog., Amherst, MA, 535 p.
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