| Middlesex Formation | |
|---|---|
| Stratigraphic range: Frasnian | |
| Type | Formation |
| Unit of | Sonyea Group |
| Underlies | Cashaqua Shale or Pulteney shale |
| Overlies | Genesee Group |
| Thickness | 6–75 feet (23 m) |
| Lithology | |
| Primary | Black Shale |
| Location | |
| Region | |
| Country | United States |
| Type section | |
| Named for | Town of Middlesex, NY |
The Middlesex Formation is a carbon rich black shale geologic formation found in the Appalachian Basin. It represents one of several transgressive events (rising sea levels) during the Late Devonian. [1]
The Middlesex is a laminated dark grey to black mudstones and siltstone. It developed in an Anoxic environment. Further evidence of this is the lack of bioturbation. There are also sparse sand and silt layers suggesting that they were single event deposits. [2]
Sedimentology encompasses the study of modern sediments such as sand, silt, and clay, and the processes that result in their formation, transport, deposition and diagenesis. Sedimentologists apply their understanding of modern processes to interpret geologic history through observations of sedimentary rocks and sedimentary structures.
The Old Red Sandstone is an assemblage of rocks in the North Atlantic region largely of Devonian age. It extends in the east across Great Britain, Ireland and Norway, and in the west along the eastern seaboard of North America. It also extends northwards into Greenland and Svalbard. These areas were a part of the ancient continent of Euramerica/Laurussia. In Britain it is a lithostratigraphic unit to which stratigraphers accord supergroup status and which is of considerable importance to early paleontology. For convenience the short version of the term, ORS is often used in literature on the subject. The term was coined to distinguish the sequence from the younger New Red Sandstone which also occurs widely throughout Britain.
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.
A turbidite is the geologic deposit of a turbidity current, which is a type of amalgamation of fluidal and sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean.
Argillite is a fine-grained sedimentary rock composed predominantly of indurated clay particles. Argillaceous rocks are basically lithified muds and oozes. They contain variable amounts of silt-sized particles. The argillites grade into shale when the fissile layering typical of shale is developed. Another name for poorly lithified argillites is mudstone. These rocks, although variable in composition, are typically high in aluminium and silica with variable alkali and alkaline earth cations. The term pelitic or pelite is often applied to these sediments and rocks. Metamorphism of argillites produces slate, phyllite, and pelitic schist.
The Ecca Group is the second of the main subdivisions of the Karoo Supergroup of geological strata in southern Africa. It mainly follows conformably after the Dwyka Group in some sections, but in some localities overlying unconformably over much older basement rocks. It underlies the Beaufort Group in all known outcrops and exposures. Based on stratigraphic position, lithostratigraphic correlation, palynological analyses, and other means of geological dating, the Ecca Group ranges between Early to earliest Middle Permian in age.
The Dakota is a sedimentary geologic unit name of formation and group rank in Midwestern North America. The Dakota units are generally composed of sandstones, mudstones, clays, and shales deposited in the Mid-Cretaceous opening of the Western Interior Seaway. The usage of the name Dakota for this particular Albian-Cenomanian strata is exceptionally widespread; from British Columbia and Alberta to Montana and Wisconsin to Colorado and Kansas to Utah and Arizona. It is famous for producing massive colorful rock formations in the Rocky Mountains and the Great Plains of the United States, and for preserving both dinosaur footprints and early deciduous tree leaves.
The Williston Basin is a large intracratonic sedimentary basin in eastern Montana, western North Dakota, South Dakota, southern Saskatchewan, and south-western Manitoba that is known for its rich deposits of petroleum and potash. The basin is a geologic structural basin but not a topographic depression; it is transected by the Missouri River. The oval-shaped depression extends approximately 475 miles (764 km) north-south and 300 miles (480 km) east-west.
The Hamilton Group is a Devonian-age geological group which is located in the Appalachian region of the United States. It is present in New York, Pennsylvania, Maryland, Ohio, West Virginia, northwestern Virginia and Ontario, Canada, and is mainly composed of marine shale with some sandstone.
The Marcellus Formation or the Marcellus Shale is a Middle Devonian age unit of sedimentary rock found in eastern North America. Named for a distinctive outcrop near the village of Marcellus, New York, in the United States, it extends throughout much of the Appalachian Basin.
The Triassic Lockatong Formation is a mapped bedrock unit in Pennsylvania, New Jersey, and New York. It is named after the Lockatong Creek in Hunterdon County, New Jersey.
The Great Estuarine Group is a sequence of Middle Jurassic sedimentary rocks deposited in the Inner Hebrides of Scotland. The sedimentary sequence was originally named the 'Great Estuarine Series' by geologist John Wesley Judd in 1878. Sedimentary outcrops occur on Skye, Raasay, Eigg and Muck. It comprises a series of shales, clays, silts, mudstones, and sandstones deposited in two drainage basins: the Inner Hebrides basin and the Sea of the Hebrides basin. The sediments are equivalent in age to the Inferior and Great Oolite Groups found in southern England.
The Sonyea Group is a geologic group in the northern part of the Appalachian Basin. It preserves fossils dating back to the Devonian period.
The Cashaqua Shale is a geologic formation in New York. It preserves fossils dating back to the Devonian period.
The Rock Stream Formation is a geologic formation in New York. It preserves fossils dating back to the Devonian period.
The Kettle Point Formation, also known as the Kettle Point (black) Shale, is a geologic formation that consists of thinly laminated, siliciclastic, organic-rich black shale with thin to thick interbeds of organic-poor mudstone. It is largely restricted to the subsurface of southwestern Ontario.
The Dent Group is a group of Upper Ordovician sedimentary and volcanic rocks in north-west England. It is the lowermost part of the Windermere Supergroup, which was deposited in the foreland basin formed during the collision between Laurentia and Avalonia. It lies unconformably on the Borrowdale Volcanic Group. This unit was previously known as the Coniston Limestone Group or Coniston Limestone Formation and should not be confused with the significantly younger Coniston Group.
The Pulteney Shale is a geologic formation in New York. It preserves fossils dating back to the Devonian period.
The Bokkeveld Group is the second of the three main subdivisions of the Cape Supergroup in South Africa. It overlies the Table Mountain Group and underlies the Witteberg Group. The Bokkeveld Group rocks are considered to range between Lower Devonian (Lochkovian) to Middle Devonian (Givetian) in age.
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