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Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has two related subfields: lithostratigraphy and biostratigraphy.
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 northeastern 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.
The Lambeth Group is a stratigraphic group, a set of geological rock strata in the London and Hampshire Basins of southern England. It comprises a complex of vertically and laterally varying gravels, sands, silts and clays deposited between 56-55 million years before present during the Ypresian age. It is found throughout the London Basin with a thickness between 10m and 30m and the Hampshire Basin with a thickness between 50m and less than 25m. Although this sequence only crops out on the edges of these basins, the fact that the Lambeth Group underlies some 25% of London at a depth of less than 30m means the formation is of engineering interest for tunnelling and foundations.
The geology of the Falkland Islands is described in several publications. The Falkland Islands are located on a projection of the Patagonian continental shelf. In ancient geological time this shelf was part of Gondwana, which around 400 million years ago broke from what is now Africa and drifted westwards relative to Africa. Studies of the seabed surrounding the islands indicated the possibility of oil. Intensive exploration began in 1996, although there had been some earlier seismic surveys in the region.
The Zechstein is a unit of sedimentary rock layers of Middle to Late Permian age located in the European Permian Basin which stretches from the east coast of England to northern Poland. The name Zechstein was formerly also used as a unit of time in the geologic timescale, but nowadays it is only used for the corresponding sedimentary deposits in Europe.
The Wealden Group, occasionally also referred to as the Wealden Supergroup, is a group in the lithostratigraphy of southern England. The Wealden group consists of paralic to continental (freshwater) facies sedimentary rocks of Berriasian to Aptian age and thus forms part of the English Lower Cretaceous. It is composed of alternating sands and clays. The sandy units were deposited in a flood plain of braided rivers, the clays mostly in a lagoonal coastal plain.
The London Basin is an elongated, roughly triangular sedimentary basin approximately 250 kilometres (160 mi) long which underlies London and a large area of south east England, south eastern East Anglia and the adjacent North Sea. The basin formed as a result of compressional tectonics related to the Alpine orogeny during the Palaeogene period and was mainly active between 40 and 60 million years ago.
The Devonian Mahantango Formation is a mapped bedrock unit in Pennsylvania, West Virginia, and Maryland. It is named for the North branch of the Mahantango Creek in Perry and Juniata counties in Pennsylvania. It is a member of the Hamilton Group, along with the underlying the Marcellus Formation Shale. South of Tuscarora Mountain in south central Pennsylvania, the lower members of this unit were also mapped as the Montebello Formation. Details of the type section and of stratigraphic nomenclature for this unit as used by the U.S. Geological Survey are available on-line at the National Geologic Map Database.
The Lias Group or Lias is a lithostratigraphic unit found in a large area of western Europe, including the British Isles, the North Sea, the Low Countries and the north of Germany. It consists of marine limestones, shales, marls and clays.
The Lower Greensand Group is a geological unit, part of the quite widely remaining underlying geological structure of southeast England. South of London in the counties of West Sussex, East Sussex, Surrey and Kent, which together form the wider Weald, the Lower Greensand can usually be subdivided to formational levels with varying properties into the Atherfield Clay Formation, the Hythe Formation, the Sandgate Formation, and the Folkestone Formation. North and west of London – including Cambridgeshire, Bedfordshire and Buckinghamshire – it is referred to as the Woburn Sands Formation. In Oxfordshire it is known as the Faringdon Sand. In North Wiltshire as the Calne Sands Formation and in parts of Wiltshire, Oxfordshire and Buckinghamshire as the Seend Ironstone Formation.
The Northampton Sand Formation, sometimes called the Northamptonshire Sand, is a Middle Jurassic geological formation which is placed within the Inferior Oolite Group. It was formerly worked extensively in Northamptonshire for its ironstone.
The Lossiemouth Sandstone is a Middle to Late Triassic age geological formation. It is exposed on the south side of the Moray Firth near Lossiemouth and near Golspie in Sutherland. Dinosaur remains are among the fossils that have been recovered from the formation.
The Mancos Shale or Mancos Group is a Late Cretaceous geologic formation of the Western United States.
Geologically the Australian state of New South Wales consists of seven main regions: Lachlan Fold Belt, the Hunter-Bowen Orogeny or New England Orogen (NEO), the Delamerian Orogeny, the Clarence Moreton Basin, the Great Artesian Basin, the Sydney Basin, and the Murray Basin.
The Murray Basin is a Cenozoic sedimentary basin in south eastern Australia. The basin is only shallow, but extends into New South Wales, Victoria and South Australia. It takes its name from the Murray River which traverses the Basin from east to west.
The coal measures is a lithostratigraphical term for the coal-bearing part of the Upper Carboniferous System. In the United Kingdom, the Coal Measures Group consists of the Upper Coal Measures Formation, the Middle Coal Measures Formation and the Lower Coal Measures Formation. The group records the deposition of fluvio-deltaic sediments which consists mainly of clastic rocks interstratified with the beds of coal. In most places, the coal measures are underlain by coarser clastic sequences known as Millstone Grit, of Namurian age. The top of the coal measures may be marked by an unconformity, the overlying rocks being Permian or later in age. In some parts of Britain, however, the Coal Measures grade up into mainly coal-barren red beds of late Westphalian and possibly Stephanian age. Within the Pennine Basin these barren measures are now referred to as the Warwickshire Group, from the district where they achieve their thickest development.
The Papa Group are a Triassic lithostratigraphic group beneath the seas northwest of Britain, and which originated as alluvial deposits. It is the lateral equivalent of the combined Mercia Mudstone and Sherwood Sandstone Groups in the Irish Sea and onshore Britain. It contains the Otter Bank Formation and the Foula Formation.
The Thanet Formation is a geological formation found in the London Basin of southeastern England. It is of early to mid-Thanetian age and gave its name to that stratigraphic interval. It was previously known as the Thanet Beds, the Thanet Sands and the Thanet Sand Formation. It was named after the Isle of Thanet. The type sections are Herne Bay in Kent for the upper part of the formation and Pegwell Bay for the lower part. It lies unconformably on the Late Cretaceous Chalk Group. It unconformably underlies the Lambeth Group, generally the Upnor Formation but in Essex it is the Reading Formation.
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 Moray Group is a stratigraphic group, a set of geological rock strata of Paleocene to Eocene age, found beneath the North Sea and in the Faroe-Shetland Basin. Two sequences are recognised, a shelf succession consisting of sandstones and siltstones of the Dornoch Formation and a thicker basinal succession consisting of mainly mudstones of the Sele Formation and the Balder Formation.
References
- ↑ British Geological Survey. "Montrose Group". The BGS Lexicon of Named Rock Units.
- ↑ Aldiss D.T. (2014). "The stratigraphical framework for the Palaeogene successions of the London Basin, UK". Open Report OR/14/008. British Geological Survey. pp. 9–14. Retrieved 22 January 2018.