Onondaga (geological formation)
Encyclopedia
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
s and 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...
s of Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
age that form an important geographic feature in some areas in which it outcrop
Outcrop
An outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. -Features:Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial deposits are covered by a mantle of soil and vegetation and cannot be...
s, in others; especially its Southern Ontario
Southern Ontario
Southern Ontario is a region of the province of Ontario, Canada that lies south of the French River and Algonquin Park. Depending on the inclusion of the Parry Sound and Muskoka districts, its surface area would cover between 14 to 15% of the province. It is the southernmost region of...
portion, the formation can be less prominent as a local surface feature.
In upstate 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...
and southern Ontario
Ontario
Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....
the sedimentary rocks tend to slope slightly to the southward, and the Onondaga outcrops in a line that usually forms an escarpment
Escarpment
An escarpment is a steep slope or long cliff that occurs from erosion or faulting and separates two relatively level areas of differing elevations.-Description and variants:...
(the steep face of a cuesta
Cuesta
In structural geology and geomorphology, a cuesta is a ridge formed by gently tilted sedimentary rock strata in a homoclinal structure. Cuestas have a steep slope, where the rock layers are exposed on their edges, called an escarpment or, if more steep, a cliff...
), because of its resistance to erosion. The outcrop can be traced from the Hudson River
Hudson River
The Hudson is a river that flows from north to south through eastern New York. The highest official source is at Lake Tear of the Clouds, on the slopes of Mount Marcy in the Adirondack Mountains. The river itself officially begins in Henderson Lake in Newcomb, New York...
valley westward along the southern rim of the Mohawk River
Mohawk River
The Mohawk River is a river in the U.S. state of New York. It is the largest tributary of the Hudson River. The Mohawk flows into the Hudson in the Capital District, a few miles north of the city of Albany. The river is named for the Mohawk Nation of the Iroquois Confederacy...
valley, passing just south of Syracuse
Syracuse, New York
Syracuse is a city in and the county seat of Onondaga County, New York, United States, the largest U.S. city with the name "Syracuse", and the fifth most populous city in the state. At the 2010 census, the city population was 145,170, and its metropolitan area had a population of 742,603...
, and along the northern heads of the major Finger Lakes
Finger Lakes
The Finger Lakes are a pattern of lakes in the west-central section of Upstate New York in the United States. They are a popular tourist destination. The lakes are long and thin , each oriented roughly on a north-south axis. The two longest, Cayuga Lake and Seneca Lake, are among the deepest in...
to Buffalo, New York
Buffalo, New York
Buffalo is the second most populous city in the state of New York, after New York City. Located in Western New York on the eastern shores of Lake Erie and at the head of the Niagara River across from Fort Erie, Ontario, Buffalo is the seat of Erie County and the principal city of the...
. From Fort Erie, Ontario
Fort Erie, Ontario
Fort Erie is a town on the Niagara River in the Niagara Region, Ontario, Canada. It is located directly across the river from Buffalo, New York....
it runs to Windsor
Windsor, Ontario
Windsor is the southernmost city in Canada and is located in Southwestern Ontario at the western end of the heavily populated Quebec City – Windsor Corridor. It is within Essex County, Ontario, although administratively separated from the county government. Separated by the Detroit River, Windsor...
just north of the Lake Erie
Lake Erie
Lake Erie is the fourth largest lake of the five Great Lakes in North America, and the tenth largest globally. It is the southernmost, shallowest, and smallest by volume of the Great Lakes and therefore also has the shortest average water residence time. It is bounded on the north by the...
shoreline, becoming less prominent as one travels westward. It is not distinct west of Windsor, but begins to become noticeable as a steep hill just northwest of Leamington
Leamington, Ontario
Leamington is a municipality in Essex County, southern Ontario, Canada, and has a population of 31,113. It includes Point Pelee, the southernmost point of mainland Canada. It has a large H. J. Heinz Company factory and is known as the "Tomato Capital of Canada", with 4 km² of this crop in the...
, as it forms a low ridge/escarpment along much of the Lake Erie
Lake Erie
Lake Erie is the fourth largest lake of the five Great Lakes in North America, and the tenth largest globally. It is the southernmost, shallowest, and smallest by volume of the Great Lakes and therefore also has the shortest average water residence time. It is bounded on the north by the...
shoreline.
In several spots it is breached by geologically young stream
Stream
A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...
s and spectacular waterfalls are formed, such as at Chittenango Falls
Chittenango Falls State Park
Chittenango Falls State Park is located in Madison County, New York east of Cazenovia Lake. The 167 foot waterfall cascades over roughly 400 million year old bedrock, flowing beneath a wooden bridge spanning the meandering Chittenango Creek. The park offers a variety of activities:The park offers...
just east of Syracuse, Buttermilk Falls at Le Roy, New York
Le Roy (village), New York
Le Roy is a village in Genesee County, New York, United States. The population was 4,462 at the 2000 census.The Village of Le Roy lies in the center of the Town of Le Roy at the intersection of Routes 5 and 19.- History :...
and Indian Falls
Tonawanda Creek
Tonawanda Creek is a small river in Western New York, in the United States. William Bright says the best that can be said of the name is that it is "probably from an Iroquoian source, but of unclear derivation".-Description:...
west of Batavia.
A few other breaches occur in older valleys, which likely once had waterfalls, but erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
eventually obliterated them. Such breaches occur at the Tully
Tully, New York
Tully, New York may refer to:* Tully , New York* Tully , New York...
valley, the Genesee River
Genesee River
The Genesee River is a North American river flowing northward through the Twin Tiers of Pennsylvania and New York. The river provided the original power for the Rochester area's 19th century mills and still provides hydroelectric power for downtown Rochester....
valley near Avon, New York
Avon, New York
Avon, New York is the name of two places located in Livingston County in the State of New York in the United States of America.*Avon , New York*Avon , New York...
, and at Port Colborne, Ontario
Port Colborne, Ontario
Port Colborne is a city on Lake Erie, at the southern end of the Welland Canal, in the Niagara Region of southern Ontario, Canada...
, where the old valley forms a harbor on Lake Erie.
The formation is broken by the only major fault line in western New York, the Linden Fault just east of Batavia, where the eastern side of the fault has dropped down and the ledge moved southward relative to the western side. On the western side of the fault in Genesee County
Genesee County, New York
Genesee County is a county located in Western New York, United States. As of the 2010 census, the population was 60,079. Its name is from the Seneca Indian word Gen-nis'-hee-yo meaning "The Beautiful Valley." Its county seat is Batavia.- History :...
the escarpment achieves its greatest prominence. The New York State Thruway
New York State Thruway
The New York State Thruway is a system of limited-access highways located within the state of New York in the United States. The system, known officially as the Governor Thomas E. Dewey Thruway for former New York Governor Thomas E. Dewey, is operated by the New York State Thruway Authority and...
has a rock cut at Batavia which clearly shows the fault and is a popular point for geology class field trips. The fault
Geologic fault
In geology, a fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement along the fractures as a result of earth movement. Large faults within the Earth's crust result from the action of tectonic forces...
, which runs from Attica, New York
Attica, New York
Attica is the name of some places in the U.S. state of New York:*Attica , New York, in Wyoming County*Attica , New York, in Wyoming and Genesee Counties...
northward to Lake Ontario, is still active and periodically causes minor earthquakes in the area.
The Onondaga Formation also can be found in other areas where rocks of the same age outcrop, such as in western Pennsylvania
Pennsylvania
The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...
and Michigan
Michigan
Michigan is a U.S. state located in the Great Lakes Region of the United States of America. The name Michigan is the French form of the Ojibwa word mishigamaa, meaning "large water" or "large lake"....
but they do not form prominent geographic features.
A similar and more prominent outcrop known as the Niagara Escarpment
Niagara Escarpment
The Niagara Escarpment is a long escarpment, or cuesta, in the United States and Canada that runs westward from New York State, through Ontario, Michigan, Wisconsin and Illinois...
runs parallel and about 25 miles (40 kilometers) to the north through upstate New York, but curves northwestward in southern Ontario toward Lake Huron
Lake Huron
Lake Huron is one of the five Great Lakes of North America. Hydrologically, it comprises the larger portion of Lake Michigan-Huron. It is bounded on the east by the Canadian province of Ontario and on the west by the state of Michigan in the United States...
and eventually into Michigan's Upper Peninsula and Wisconsin's Door Peninsula
Door Peninsula
The Door Peninsula is a peninsula in eastern Wisconsin, separating the southern part of the Green Bay from Lake Michigan. The peninsula begins in northern Brown and Kewaunee counties and proceeds northeast to include all of Door County. It is the western portion of the Niagara Escarpment. Well...
.
Another smaller outcrop known as the Portage Escarpment lies about 35 miles to the south, running along the southern ends of the Finger Lakes
Finger Lakes
The Finger Lakes are a pattern of lakes in the west-central section of Upstate New York in the United States. They are a popular tourist destination. The lakes are long and thin , each oriented roughly on a north-south axis. The two longest, Cayuga Lake and Seneca Lake, are among the deepest in...
and forming Cascadilla, Ithaca and Buttermilk Falls in Ithaca
Ithaca, New York
The city of Ithaca, is a city in upstate New York and the county seat of Tompkins County, as well as the largest community in the Ithaca-Tompkins County metropolitan area...
.
The Onondaga Escarpment contains significant outcrops of flint
Flint
Flint is a hard, sedimentary cryptocrystalline form of the mineral quartz, categorized as a variety of chert. It occurs chiefly as nodules and masses in sedimentary rocks, such as chalks and limestones. Inside the nodule, flint is usually dark grey, black, green, white, or brown in colour, and...
(a type of chert
Chert
Chert is a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils. It varies greatly in color , but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements...
) which bears the escarpment's name. This variety of chert was of great importance to First Nations
First Nations
First Nations is a term that collectively refers to various Aboriginal peoples in Canada who are neither Inuit nor Métis. There are currently over 630 recognised First Nations governments or bands spread across Canada, roughly half of which are in the provinces of Ontario and British Columbia. The...
peoples throughout Southern Ontario
Southern Ontario
Southern Ontario is a region of the province of Ontario, Canada that lies south of the French River and Algonquin Park. Depending on the inclusion of the Parry Sound and Muskoka districts, its surface area would cover between 14 to 15% of the province. It is the southernmost region of...
, who used it to make stone tools (lithics
Stone tool
A stone tool is, in the most general sense, any tool made either partially or entirely out of stone. Although stone tool-dependent societies and cultures still exist today, most stone tools are associated with prehistoric, particularly Stone Age cultures that have become extinct...
) such as projectile point
Projectile point
In archaeological terms, a projectile point is an object that was hafted to a projectile, such as a spear, dart, or arrow, or perhaps used as a knife....
s and hide scrapers. This variety of chert, which is of reasonably high-quality and which was highly-valued by First Nations peoples, is often a common variety of chert recovered archaeologically from sites relatively adjacent to outcrops; for example, Onondaga-variety chert comprises 95% of all of the flint material from some sites in Milton, Ontario
Milton, Ontario
Milton is a town in Southern Ontario, Canada, and part of the Halton Region in the Greater Toronto Area. Milton received a tremendous amount of awareness following the release of the results of the 2006 Census, which indicated that Milton is the fastest growing municipality in the Greater Golden...
. The material has also been found as well at some distance from its original source; Onondaga chert has been recovered at the late archaic Duck Lake archaeological site in northern Michigan, circa 400 kilometers from the nearest outcropping of the material. This wide distribution implies either a very large seasonal migration of ancient peoples or long-distance trade routes, with both likely being the case at different times throughout the prehistory of the Great Lakes
Great Lakes
The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...
region.
Age
Relative age dating of the Onondoga places its formation in the Eifelian to Givetian stageFaunal stage
In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.Rock...
of the Middle Devonian period, or 391.9 to 383.7 Ma. Radiometric dating of a sample from the bentonite at the top of the Onondoga placed it at 390 ± 0.5 Ma.