Brief Geological History of
the Connecticut River Valley
Prof. Richard D. Little
[Please see the
edition of Dinosaurs,
Dunes, and Drifting Continents
and/or the DVDs Flow
of Time and
and Fall of Lake Hitchcock for more in-depth content. They are
available at your local library or order from “publications” on
the home page of this web site.]
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, p. 9)
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 &
- 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. A number of tectonic plates of the Earth's
crust drifted 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, the Appalachians. The 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.
- 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. The Mesozoic rift valley rivers flowed to the
southwest, toward New York and New Jersey.
fault that dominated the Mesozoic rift was located on the eastern
side of the valley, and is known as the Eastern Border Fault. It 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 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 collisions), these rusty
sedimentary layers from alluvial fans and lake beds provide important
geological examples and evidence of our Mesozoic history, including
some world-class fossils.
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
Beneski 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 shale.
another site bordering the river in Holyoke, MA, Ostrom has described
19 trackways that indicate, because of their parallel orientation,
herding behavior. (Ostrom, 1972) More recent study (Getty et al,
2012) has identified many more prints. They seem to be walking
parallel to the shoreline. Therefore herding behavior may not be
indicated, especially since these are mainly carnivorous animals.
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 well 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
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 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
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
remainder of the Mesozoic rift valley with sedimentary rocks and
lavas continues southerly to New Haven with no river of any
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 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 4,000 years,
gradually extended up the Connecticut River drainage as far north as
West Burke, VT, a distance of about 250 miles. Approximately 14,000
years ago Lake Hitchcock drained, slowly, not in a huge flood,
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 extensive brick industry. Today the clay is
occasionally mined 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.
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.
The waterfalls provided important hydropower for historic industrial
development along the river. Dams and canals were built to
capitalize on this geological gift of power to the 16th
Century pre-electric world. Today, hydropower is harnessed for
electricity to run machines and warm homes.
its mouth, the river has been flooded by the sea, a consequence of
glacial melting and worldwide sea level rise. The lower river valley
is an estuary, with tidal effects as far as Hartford. Extensive
marshland and shifting sandbars dominate the river's end -- the only
major American river not having a city at its mouth (Stekl &
Hill, 1972). Beaches built at least in part from the river's flow of
sand, form important recreational deposits as land and sea connect
(Patton & Kent, 1991).
unique combination of geology and landforms gives the Connecticut
River Valley an outstanding landscape diversity. It’s an excellent
natural laboratory for learning, 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.
P.R., A. JUDGE, J. CSONKA AND A.M. BUSH. 2012. Were
Jurassic dinosaurs gregarious? Reexamining the evidence
Dinosaur Footprint Reservation in Holyoke,
In: M. Thomas, ed. Guidebook for Fieldtrips
Connecticut and Massachusetts: Northeast Section Geological
of America Meeting 2012. State Geological
Natural History Survey
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, p.
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) Fall, 2000)
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 Newark 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. 1-12
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.
Geology Education Products and Services
Richard D. Little
6 Grand View Lane
Phone / Fax (413)