Champlain thrust
Encyclopedia
The Champlain Thrust is a fault extending southward from southern Quebec
Quebec
Quebec or is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking population and the only one whose sole official language is French at the provincial level....

, though western Vermont
Vermont
Vermont is a state in the New England region of the northeastern United States of America. The state ranks 43rd in land area, , and 45th in total area. Its population according to the 2010 census, 630,337, is the second smallest in the country, larger only than Wyoming. It is the only New England...

 in the Champlain Valley
Champlain Valley
The Champlain Valley is a region of the United States around Lake Champlain in Vermont and New York extending slightly into Quebec, Canada as part of the St. Lawrence River drainage basin drained northward by the Richelieu River into the St...

, and into eastern New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...

 in the Hudson Valley
Hudson Valley
The Hudson Valley comprises the valley of the Hudson River and its adjacent communities in New York State, United States, from northern Westchester County northward to the cities of Albany and Troy.-History:...

. This east dipping thrust fault
Thrust fault
A thrust fault is a type of fault, or break in the Earth's crust across which there has been relative movement, in which rocks of lower stratigraphic position are pushed up and over higher strata. They are often recognized because they place older rocks above younger...

 transports Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...

-Ordovician
Ordovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

 passive margin shelf rocks westerward by about 30–50 mi (48.3–80.5 ) and places them on top of Middle Ordovician rocks. The Middle Ordivician accretion of the one or more island arcs terranes drove the initial thrusting during the Taconic Orogeny
Taconic orogeny
The Taconic orogeny was a mountain building period that ended 440 million years ago and affected most of modern-day New England. A great mountain chain formed from eastern Canada down through what is now the Piedmont of the East coast of the United States...

, though reactivation of the fault may have occurred during the middle Devonian Acadian Orogeny
Acadian orogeny
The Taconic, Acadian and Alleghenian orogenies are the three tectonic phases responsible for the formation of the present Appalachian Mountains. The Acadian orogeny is a middle Paleozoic mountain building episode dating back 325-400 million years which should not be regarded as a single event but...

.

The thrust fault is exposed to the north of the city of Burlington, Vermont
Burlington, Vermont
Burlington is the largest city in the U.S. state of Vermont and the shire town of Chittenden County. Burlington lies south of the U.S.-Canadian border and some south of Montreal....

 on the shores of Lake Champlain
Lake Champlain
Lake Champlain is a natural, freshwater lake in North America, located mainly within the borders of the United States but partially situated across the Canada—United States border in the Canadian province of Quebec.The New York portion of the Champlain Valley includes the eastern portions of...

 at Lone Rock Point. Here the Lower Cambrian Dunham dolostone
Dolostone
Dolostone or dolomite rock is a sedimentary carbonate rock that contains a high percentage of the mineral dolomite. In old U.S.G.S. publications it was referred to as magnesian limestone. Most dolostone formed as a magnesium replacement of limestone or lime mud prior to lithification. It is...

can be seen thrust on top of the Middle Ordovician Iberville shales.

The Champlain Thrust marks the most westerly thrust of the Taconic Orogeny.

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