The Vernon Formation is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

in the

Appalachian Basin The geology of the Appalachians dates back more than 1.2 billion years to the Mesoproterozoic era when two continental cratons collided to form the supercontinent Rodinia, 500 million years prior to the development of the range during the form ...

. It is the lowest unit of the Salina Group. It is made up of red and green

shales Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g., kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...

, dolomite,

anhydrite Anhydrite, or anhydrous calcium sulfate, is a mineral with the chemical formula CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the ...

and

halite Halite ( ), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride ( Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, pi ...

. It is made up of three distinct units starting at the bottom (oldest) A, B and C units. These units correspond to units of the same name in its parent

group A group is a number of persons or things that are located, gathered, or classed together. Groups of people * Cultural group, a group whose members share the same cultural identity * Ethnic group, a group whose members share the same ethnic iden ...

the Salina.

Description

The Vernon Formation mostly is within the Salina Group. However, in Central

Pennsylvania Pennsylvania, officially the Commonwealth of Pennsylvania, is a U.S. state, state spanning the Mid-Atlantic (United States), Mid-Atlantic, Northeastern United States, Northeastern, Appalachian, and Great Lakes region, Great Lakes regions o ...

and Central

New York New York most commonly refers to: * New York (state), a state in the northeastern United States * New York City, the most populous city in the United States, located in the state of New York New York may also refer to: Places United Kingdom * ...

onward East the Vernon is part of both the Wills Creek and Bloomsburg due to erosional deposits migrating from the east.

Stratigraphy

Lower Vernon (or Unit A) is the base of both the Vernon and Salina in western Pennsylvania and New York, continuing into Ohio and Michigan. In north central Pennsylvania and central New York it is a part of the Bloomsburg. The Bloomsburg is an ancient delta system carrying sediment westward from the Taconic Highlands slowly filling the basin. In the west the basin was filled with carbonates and shales. The Base of the Vernon is marked in the west typically by a sharp drop in gamma logs. This is due to the disappearance of shale and moving into a crystalline near pure carbonite unit. The would be either the Lockport or the Guelph dolomites, depending on location. Within the Michigan Basin and Ohio the Lower Vernon is further into two units the A1 and A2. Each unit has a lower division of

evaporite An evaporite () is a water- soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as oce ...

(salt or anhydrite) and the upper section is a carbonate, typically dolomite. In the east the Lower Vernon contains predominantly red shale. Moving west this is gradually replaced with green shale, then grey shale. Finally dolomite, anhydrite and halite in the western extent. The Middle Vernon (Unit B) is within the Salina from western Pennsylvania and New York on west. In the central part of theses states on east in is the lowest member of the Wills Creak. This difference again is due to erosional clastic material moving westward from the Taconic Highlands. In the East or Wills Creak area, the Middle Vernon has occasional red shales, particularly in the southeast. Generally, however it is predominantly green shale, with interbedded dolomite and siltstone. Moving west dolomite replaces shale and anhydrite becomes prevalent. Within the Salina parts of the formation there may be up to seven distinct salt beds. The base of the Middle Vernon is marked in the Salina by the last salt bed, and a slight overall rise in gamma. With in the Wills Creek area, it is marked by a general overall rise in gamma. The Upper Vernon, is composed of shale and siltstone. Red and green shale to the east with grey and green to the west. In western Pennsylvania dolomite and anhydrite appear. Generally evaporites are not common in this section. The base is marked by a sharp drop in gamma, due to a salt bed in the west and dolomite to the east.

References

{{reflist Geologic formations of New York (state) Silurian New York Silurian United States Silurian Canada Silurian Ontario