Potsdam Sandstone
Encyclopedia
The Potsdam Sandstone is a geologic formation
of late Cambrian
to early Ordovician
age found in upstate New York
and northern Vermont
. A well-cemented sandstone
of nearly pure quartz
, in the 19th century it was widely used in construction and in refractory
linings for iron furnace
s.
in Potsdam, New York
, where in 1838 Ebenezer Emmons
described it in outcrop
s along the Raquette River
.
on a surface of Precambrian metamorphic rock
. It is the earliest unit in the marine-transgressive sedimentary rock
sequence deposited during the early Paleozoic
as sea level rose to gradually inundate the craton
of the paleocontinent of Laurentia
. The rock, which is formed from sediment
s eroded off unvegetated terrestrial landscapes and deposited in near-shore coastal environments, consists almost entirely of sand
-size quartz grains held together by quartz cement
. It ranges in color from gray to tan, yellow, and red, with the colors imparted by small amounts of the red iron oxide
mineral hematite
, Fe2O3, and the yellow iron oxide mineral goethite
, FeO(OH).
As sea level rose in the depositional environment, increasing amounts of carbonate minerals were deposited in the sediment, with the result that the unit grades upward into dolomitic sandstone in the upper Potsdam and then to sandy dolostone
at the base of the overlying Theresa Formation.
s. Trace fossils in the unit include both vertical burrows, such as Diplocraterion
and Skolithos
and horizontal trackways, such as Diplichnites
, Protichnites
, and Climactichnites
. In 1903, a 20-ton (18-tonne) slab of Potsdam Sandstone from Clinton County, New York
, displaying tracks attributed to trilobite
s, was placed in the New York State Museum
. Fossil impressions of the whole bodies of jellyfish
have also been found in the Potsdam.
. Outcrop exposures of the Potsdam Sandstone occur throughout the Saint Lawrence lowlands
, western Lake Champlain
Valley, and northern Mohawk Valley
. Ausable Chasm
, near Plattsburgh, has a continuous exposure of a section more than 160 metres (524.9 ft) thick. The formation reaches its maximum thickness of about 450 metres (1,476.4 ft) in the northern Champlain lowland.
, attractive reddish coloring, and resistance to weathering. The rock also was said to be "soft and easy to carve" when freshly quarried but "extremely hard" and "weather-resistant" after exposure to the air, but modern geologists suggest that this is a misconception. Potsdam Sandstone resists spalling when exposed to fire, making it highly suitable for use as a refractory for lining iron furnaces.
Local sandstone was used for many buildings in Potsdam, as well as for purposes such as gravestones and sidewalk
s. Buildings in other cities constructed with this rock include Canada's House of Parliament
in Ottawa
, and the Cathedral of All Saints in Albany, New York
. Potsdam Sandstone and its stratigraphic equivalents also have been quarried for use as building stone at several sites in Quebec.
, although stratigraphic boundaries and nomenclature can differ. In Ontario
, the Nepean Sandstone is regarded as a stratigraphic equivalent to the Potsdam Sandstone. In Quebec
, the Potsdam Group is recognized, consisting of the Covey Hill Formation and the Cairnside Formation, both of which are sandstones.
Historically the name "Potsdam sandstone" was also applied to various other North American sandstone bodies that directly overlie Precambrian
crystalline rocks, including sandstones in Canada, Pennsylvania
, Virginia
, Iowa
, Wisconsin
, Minnesota
, Michigan
, and Indiana
, and attempts were made to identify or correlate various rocks with the Potsdam formation. The basal Cambrian sandstone formation in much of the upper Mississippi Valley and southern Great Lakes
region is now designated the Mount Simon Sandstone and is, in turn, assigned to the Potsdam Supergroup, which takes its name from the Potsdam Sandstone. Similar quartz arenite sandstone found in Wyoming
was also identified historically as the "Potsdam sandstone."
Geologic formation
A formation or geological formation is the fundamental unit of lithostratigraphy. A formation consists of a certain number of rock strata that have a comparable lithology, facies or other similar properties...
of late 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...
to early 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...
age found 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 northern 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...
. A well-cemented sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
of nearly pure quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
, in the 19th century it was widely used in construction and in refractory
Refractory
A refractory material is one that retains its strength at high temperatures. ASTM C71 defines refractories as "non-metallic materials having those chemical and physical properties that make them applicable for structures, or as components of systems, that are exposed to environments above...
linings for iron furnace
Smelting
Smelting is a form of extractive metallurgy; its main use is to produce a metal from its ore. This includes iron extraction from iron ore, and copper extraction and other base metals from their ores...
s.
Name and type locality
It is named for its type localityType locality (geology)
Type locality , also called type area or type locale, is the where a particular rock type, stratigraphic unit, fossil or mineral species is first identified....
in Potsdam, New York
Potsdam, New York
Potsdam, New York relates to two locations in Saint Lawrence County, New York:*Potsdam , New York*Potsdam , New York, in the town of Potsdam; site of the State University of New York at Potsdam...
, where in 1838 Ebenezer Emmons
Ebenezer Emmons
Ebenezer Emmons , was a pioneering American geologist.Emmons was born at Middlefield, Massachusetts, on May 16, 1799, son of Ebenezer and Mary Emmons....
described it in 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 along the Raquette River
Raquette River
The Raquette River, sometimes spelled Racquette, originates at Raquette Lake in the Adirondack Mountains in New York. long, it is the third longest river entirely in the state of New York....
.
Stratigraphic setting and lithology
The Potsdam Sandstone lies unconformablyUnconformity
An unconformity is a buried erosion surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger, but the term is used to describe...
on a surface of Precambrian metamorphic rock
Metamorphic rock
Metamorphic rock is the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat and pressure causing profound physical and/or chemical change...
. It is the earliest unit in the marine-transgressive sedimentary rock
Sedimentary rock
Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....
sequence deposited during the early Paleozoic
Paleozoic
The Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...
as sea level rose to gradually inundate the craton
Craton
A craton is an old and stable part of the continental lithosphere. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates. They are characteristically composed of ancient crystalline basement rock, which may be covered by...
of the paleocontinent of Laurentia
Laurentia
Laurentia is a large area of continental craton, which forms the ancient geological core of the North American continent...
. The rock, which is formed from sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
s eroded off unvegetated terrestrial landscapes and deposited in near-shore coastal environments, consists almost entirely of sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
-size quartz grains held together by quartz cement
Cement (geology)
The term cement in geology means the fine-grained minerals which bind the coarser-grained matrix in sedimentary rocks.Such cements are typically composed of calcite, quartz or clay minerals....
. It ranges in color from gray to tan, yellow, and red, with the colors imparted by small amounts of the red iron oxide
Iron oxide
Iron oxides are chemical compounds composed of iron and oxygen. All together, there are sixteen known iron oxides and oxyhydroxides.Iron oxides and oxide-hydroxides are widespread in nature, play an important role in many geological and biological processes, and are widely utilized by humans, e.g.,...
mineral hematite
Hematite
Hematite, also spelled as haematite, is the mineral form of iron oxide , one of several iron oxides. Hematite crystallizes in the rhombohedral system, and it has the same crystal structure as ilmenite and corundum...
, Fe2O3, and the yellow iron oxide mineral goethite
Goethite
Goethite , named after the German polymath Johann Wolfgang von Goethe, is an iron bearing oxide mineral found in soil and other low-temperature environments. Goethite has been well known since prehistoric times for its use as a pigment. Evidence has been found of its use in paint pigment samples...
, FeO(OH).
As sea level rose in the depositional environment, increasing amounts of carbonate minerals were deposited in the sediment, with the result that the unit grades upward into dolomitic sandstone in the upper Potsdam and then to sandy 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...
at the base of the overlying Theresa Formation.
Paleontology
Fossil remains of whole animals are rare in the Potsdam Sandstone, but there are some significant occurrences of trace fossilTrace fossil
Trace fossils, also called ichnofossils , are geological records of biological activity. Trace fossils may be impressions made on the substrate by an organism: for example, burrows, borings , urolites , footprints and feeding marks, and root cavities...
s. Trace fossils in the unit include both vertical burrows, such as Diplocraterion
Diplocraterion
Diplocraterion is an ichnogenus describing vertical U-shaped burrows having a spreite between the two limbs of the U. The spreite of fainter U-shaped traces appears above and below the final tunnel, made as the organism moved up and down through the sediment.- Further reading :* Šimo V. &...
and Skolithos
Skolithos
Skolithos is a common trace fossil ichnogenus whose original form consisted of approximately vertical cylinders. One well-known occurrence of Cambrian trace fossils is the famous 'Pipe Rock' of northwest Scotland...
and horizontal trackways, such as Diplichnites
Diplichnites
Diplichnites is an ichnogenus thought to be made by members of the Phylum Arthropoda. It is a fossil trackway showing two parallel lines of feet impressions. The famous terrestrial arthropod genus Arthropleura produces the trace fossil D. cuithensis...
, Protichnites
Protichnites
Protichnites is a genus of trace fossil consisting of the imprints made by the walking activity of arthropods. It is likely that more than one type of arthropod was responsible for these tracks. Euthycarcinoids, aglaspidids and eurypterids are possible contributors. Protichnites consists of two...
, and Climactichnites
Climactichnites
Climactichnites is an enigmatic, late Cambrian fossil formed on or within sandy tidal flats around .It has been interpreted in many different ways in the past, but is now known to be a trace fossil of a slug-like organism, thought to have moved by crawling on near-shore or on-shore surfaces or...
. In 1903, a 20-ton (18-tonne) slab of Potsdam Sandstone from Clinton County, New York
Clinton County, New York
Clinton County is a county located in the U.S. state of New York. As of the 2010 census, the population was 82,128. Its name is in honor of the first Governor of New York as a state, George Clinton. Its county seat is Plattsburgh.-History:...
, displaying tracks attributed to trilobite
Trilobite
Trilobites are a well-known fossil group of extinct marine arthropods that form the class Trilobita. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period , and they flourished throughout the lower Paleozoic era before...
s, was placed in the New York State Museum
New York State Museum
The New York State Museum is a research-backed institution in Albany, New York, United States. It is located on Madison Avenue, attached to the south side of the Empire State Plaza, facing onto the plaza and towards the New York State Capitol...
. Fossil impressions of the whole bodies of jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...
have also been found in the Potsdam.
Geographic occurrence
In New York state, the Potsdam formation is found primarily north and west of the Adirondack MountainsAdirondack Mountains
The Adirondack Mountains are a mountain range located in the northeastern part of New York, that runs through Clinton, Essex, Franklin, Fulton, Hamilton, Herkimer, Lewis, Saint Lawrence, Saratoga, Warren, and Washington counties....
. Outcrop exposures of the Potsdam Sandstone occur throughout the Saint Lawrence lowlands
Saint Lawrence Lowlands
The St. Lawrence Lowlands is an ecoregion of Mixedwood Plains and a physiographic region of Canada and the United States. It is sometimes named the "Great Lakes/St. Lawrence Lowlands", but that name improperly includes the Great Lakes Basin which, while it might drain to the Atlantic Ocean by way...
, western 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...
Valley, and northern Mohawk Valley
Mohawk Valley
The Mohawk Valley region of the U.S. state of New York is the area surrounding the Mohawk River, sandwiched between the Adirondack Mountains and Catskill Mountains....
. Ausable Chasm
Ausable Chasm
Ausable Chasm is a sandstone gorge tourist attraction located near Keeseville, New York. The Ausable River runs through it, which then empties into Lake Champlain....
, near Plattsburgh, has a continuous exposure of a section more than 160 metres (524.9 ft) thick. The formation reaches its maximum thickness of about 450 metres (1,476.4 ft) in the northern Champlain lowland.
Uses in construction and industry
In the 19th century, Potsdam Sandstone was highly regarded as a building material. There was extensive quarrying for Potsdam Sandstone in the Potsdam area, beginning in 1809. Properties of the rock that give it value as a building material include high compressive strengthCompressive strength
Compressive strength is the capacity of a material or structure to withstand axially directed pushing forces. When the limit of compressive strength is reached, materials are crushed. Concrete can be made to have high compressive strength, e.g...
, attractive reddish coloring, and resistance to weathering. The rock also was said to be "soft and easy to carve" when freshly quarried but "extremely hard" and "weather-resistant" after exposure to the air, but modern geologists suggest that this is a misconception. Potsdam Sandstone resists spalling when exposed to fire, making it highly suitable for use as a refractory for lining iron furnaces.
Local sandstone was used for many buildings in Potsdam, as well as for purposes such as gravestones and sidewalk
Sidewalk
A sidewalk, or pavement, footpath, footway, and sometimes platform, is a path along the side of a road. A sidewalk may accommodate moderate changes in grade and is normally separated from the vehicular section by a curb...
s. Buildings in other cities constructed with this rock include Canada's House of Parliament
Centre Block
The Centre Block is the main building of the Canadian parliamentary complex on Parliament Hill, in Ottawa, Ontario, containing the Commons and Senate chambers, as well as the offices of a number of Members of Parliament and Senators, as well as senior administration for both legislative houses...
in Ottawa
Ottawa
Ottawa is the capital of Canada, the second largest city in the Province of Ontario, and the fourth largest city in the country. The city is located on the south bank of the Ottawa River in the eastern portion of Southern Ontario...
, and the Cathedral of All Saints in Albany, New York
Albany, New York
Albany is the capital city of the U.S. state of New York, the seat of Albany County, and the central city of New York's Capital District. Roughly north of New York City, Albany sits on the west bank of the Hudson River, about south of its confluence with the Mohawk River...
. Potsdam Sandstone and its stratigraphic equivalents also have been quarried for use as building stone at several sites in Quebec.
Stratigraphic equivalents and related units
Stratigraphically equivalent and lithologically similar sandstone extends across the international border into CanadaCanada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, although stratigraphic boundaries and nomenclature can differ. In 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 Nepean Sandstone is regarded as a stratigraphic equivalent to the Potsdam Sandstone. In 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....
, the Potsdam Group is recognized, consisting of the Covey Hill Formation and the Cairnside Formation, both of which are sandstones.
Historically the name "Potsdam sandstone" was also applied to various other North American sandstone bodies that directly overlie Precambrian
Precambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
crystalline rocks, including sandstones in Canada, 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...
, Virginia
Virginia
The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...
, Iowa
Iowa
Iowa is a state located in the Midwestern United States, an area often referred to as the "American Heartland". It derives its name from the Ioway people, one of the many American Indian tribes that occupied the state at the time of European exploration. Iowa was a part of the French colony of New...
, Wisconsin
Wisconsin
Wisconsin is a U.S. state located in the north-central United States and is part of the Midwest. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michigan to the northeast, and Lake Superior to the north. Wisconsin's capital is...
, Minnesota
Minnesota
Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...
, 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"....
, and Indiana
Indiana
Indiana is a US state, admitted to the United States as the 19th on December 11, 1816. It is located in the Midwestern United States and Great Lakes Region. With 6,483,802 residents, the state is ranked 15th in population and 16th in population density. Indiana is ranked 38th in land area and is...
, and attempts were made to identify or correlate various rocks with the Potsdam formation. The basal Cambrian sandstone formation in much of the upper Mississippi Valley and southern 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 is now designated the Mount Simon Sandstone and is, in turn, assigned to the Potsdam Supergroup, which takes its name from the Potsdam Sandstone. Similar quartz arenite sandstone found in Wyoming
Wyoming
Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...
was also identified historically as the "Potsdam sandstone."