The Maastrichtian ( /mɑːˈstrɪktiən/) is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned the interval from . The Maastrichtian was preceded by the Campanian and succeeded by the Danian (part of the Paleogene and Paleocene).
At the end of this period, there was a mass extinction known as the Cretaceous–Paleogene extinction event, (formerly known as the Cretaceous–Tertiary extinction event).[a] At this extinction event, many commonly recognized groups such as non-avian dinosaurs, plesiosaurs and mosasaurs, as well as many other lesser-known groups, died out. The cause of the extinction is most commonly linked to an asteroid about 10 to 15 kilometres (6.2 to 9.3 mi) wide colliding with Earth at the end of the Cretaceous.
|Subdivision of the Cretaceous system|
according to the ICS, as of 2017.
The Maastrichtian was introduced into scientific literature by Belgian geologist André Hubert Dumont in 1849, after studying rock strata of the Chalk Group close to the Dutch city of Maastricht. These strata are now classified as the Maastricht Formation - both formation and stage derive their names from the city. The Maastricht Formation is known for its fossils from this age, most notably those of the giant sea reptile Mosasaurus, which in turn also derives its name from the Dutch city (mosa being Latin for the river Maas).
The base of the Maastrichtian stage is at the first appearance of ammonite species Pachydiscus neubergicus. At the original type locality near Maastricht, the stratigraphic record was later found to be incomplete. A reference profile for the base was then appointed in a section along the Ardour river called Grande Carrière, close to the village of Tercis-les-Bains in southwestern France. The top of the Maastrichtian stage is defined to be at the iridium anomaly at the Cretaceous–Paleogene boundary (K–Pg boundary), which is also characterised by the extinction of many groups of life, such as certain foraminifers and calcareous nanoplankton, all ammonites and belemnites, etc.
The Maastrichtian is commonly subdivided into two substages (Upper and Lower) and three ammonite biozones. The biozones are (from young to old):
The following are summaries of the characteristics of specific Maastrichtian aged formations.
The Bearpaw Formation, also called the Bearpaw Shale, is a sedimentary rock formation found in northwestern North America. It is exposed in the U.S. state of Montana, as well as the Canadian provinces of Alberta and Saskatchewan, east of the Rocky Mountains. It overlies the older Two Medicine, Judith River and Dinosaur Park Formations, and is in turn overlain by the Horseshoe Canyon Formation in Canada and the Fox Hills Sandstone in Montana. To the east and south it blends into the Pierre Shale.
A marine formation composed mostly of shale, it represents the last major expansion of the Western Interior Seaway before it completely receded from northwestern North America by the end of the Cretaceous Period. It includes well-preserved ammonite fossils. Other fossils found in this formation include many types of shellfish, bony fish, sharks, rays, birds, and marine reptiles like mosasaurs, plesiosaurs and sea turtles. The occasional dinosaur remains have also been discovered, presumably from carcasses washed out to sea.
The Hell Creek Formation is an intensely studied division of Upper Cretaceous to lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana. The Hell Creek Formation occurs in badlands of eastern Montana and portions of North Dakota, South Dakota, and Wyoming. In Montana, the Hell Creek Formation overlies the Fox Hills Formation and is the uppermost formation of the Cretaceous period.
It is a series of fresh and brackish-water clays, mudstones, and sandstones deposited during the Maastrichtian, the last part of the Cretaceous period, by fluvial activity in fluctuating river channels and deltas and very occasional peaty swamp deposits along the low-lying eastern continental margin fronting the late Cretaceous Western Interior Seaway. The climate was mild. The iridium-enriched Cretaceous–Paleogene boundary, which separates the Cretaceous from the Cenozoic, occurs as a discontinuous but distinct thin marker bedding within the Formation, near its uppermost strata.
The Horseshoe Canyon Formation is part of the Edmonton Group and is up to 230 m in depth. It is Late Campanian to Early Maastrichtian in age (Edmontonian Land Mammal Age) and is composed of mudstone, sandstone, and carbonaceous shales. There are a variety of environments, which have yielded a diversity of fossil material. The Horseshoe Canyon Formation outcrops extensively in the area of Drumheller, Alberta, as well as further north along the Red Deer River near Trochu, and also in the city of Edmonton.
The Sarir field was discovered in southern Cyrenaica during 1961 and is considered to be the largest oil field in Libya, with estimated oil reserves of 12 Gbbl (1.9 km3). Sarir is operated by the Arabian Gulf Oil Company (AGOCO), a subsidiary of the state-owned National Oil Corporation (NOC).
The Sarir stratigraphic column generally resembles succession patterns throughout the Sirte Basin, with some variations. In the early regressive phase, basal sandstones were deposited on a Precambrian basement of igneous and metamorphic rocks. Sandstones are dated on angiosperm pollen as younger than Albian, probably from the Late Cretaceous. After a lengthy hiatus, represented by unconformity and sandstone erosion, a transgressive sequence of red, green, and purple Anhydrite shales was laid. Variegated bed remnants occur in crestal sections of many northern structures, such as in wells B-1-65 and C-1-80.
Above the transgressive sequence are Late Cretaceous shales with tight, micritic carbonate, marking the top of the Mesozoic. These shales thicken into troughs, providing the field's sole source rock. The youngest fauna are Maastrichtian, with an apparent disconformity between the Late Cretaceous and Paleocene, marked by high levels of gamma radiation on logs.
The Maevarano Formation is an Upper Cretaceous sedimentary rock formation found in the Mahajanga Province of northwestern Madagascar. It is most likely Maastrichtian in age, and records a seasonal, semiarid environment with rivers that had greatly varying discharges. Notable animal fossils recovered include the theropod dinosaur Majungasaurus and the early birds Rahonavis and Vorona, and the titanosaurian sauropod Rapetosaurus.
The Lameta Formation is a sedimentary rock formation found in Madhya Pradesh, Gujarat, and Maharashtra, India. It is of Maastrichtian age (Upper Cretaceous), and is notable for its dinosaur fossils. Many dubious names have been created for isolated bones, but several genera of dinosaurs from these rocks are well-supported, including the titanosaur sauropod Isisaurus, the abelisaurs Indosaurus, Indosuchus, Laevisuchus, and Rajasaurus and possible stegosaurs.
It was previously known as the "Lower Nemegt Beds", occurring beneath the Nemegt Formation and above the Djadokhta Formation. It is approximately 4 inches (100 mm) in thickness and was laid down roughly 80-71 mya, making it uncertain whether it should be classed as Campanian or Maastrichtian, although the latter is less likely. The Barun Goyot Formation preserves an environment of sand dunes, created from wind-eroded rocks (aeolian dunes).
The Nemegt Formation is a Late Cretaceous sedimentary formation in the Gobi Desert of Mongolia. It overlies, and in some places interdigitates with, the Barun Goyot Formation. It consists of river channel sediments and contains fossils of fish, turtles, crocodilians, birds and a diverse fauna of dinosaurs. The climate was wetter than when the preceding formations were deposited; there seems to have existed at least some degree of forest cover.
The absolute age of the Nemegt Formation is unknown but it is thought to be Maastrichtian or maybe late Campanian in age, very roughly some 76-65 million years old. The presence of Saurolophus, a taxon also known from the Horseshoe Canyon Formation of Alberta, may indicate an Early Maastrichtian age, about 70 million years old.
Several lineages of modern birds existed, though many were of lineages that differed profoundly from their relatives of today and thus are not their ancestors, but became extinct in the Cenozoic. For example, Vegavis iaai indicates that at least four lineages of Anseriformes were distinct: Anhimidae, Anatidae, Anseranatidae and Presbyornithidae (and possibly Dromornithidae), and that there was at least one Galliformes lineage too, and apparently the Gastornithiformes were also distinct. It is also highly likely that there was at least one, and probably several, lineages of Charadriiformes, that penguins were about to split from their closest relatives or had already done so, and that if the Metaves are a valid group they would presumably have been distinct too. Also, paleognaths were of course long distinct from neognaths.
Traditionally, pterosaur faunas of the Maastrichtian were assumed to be dominated by azhdarchids, with other pterosaur groups having become extinct earlier on. However, more recent findings suggest a fairly composite pterosaur diversity: at least six ("Nyctosaurus" lamegoi, a Mexican humerus, a Jordan humerus and several taxa from Morocco) nyctosaurs date to this period, as do a few pteranodontids, and Navajodactylus, tentatively assigned to Azhdarchidae, lacks any synapomorphies of the group. This seems to underscore a higher diversity of terminal Cretaceous pterosaurs than previously thought.
Ammonitida is an order of more highly evolved ammonoid cephalopods that lived from the Jurassic through Cretaceous time periods, commonly with intricate ammonitic sutures.
Ammonitida is divided into four suborders, the Phylloceratina, Lytoceratina, Ancyloceratina, and Ammonitina.
The Phylloceratina is the ancestral stock, derived from the Ceratitida near the end of the Triassic. The Phylloceratina gave rise to the Lytoceratina near the beginning of the Jurassic which in turn gave rise to the highly specialized Ancyloceratina near the end of the Jurassic. Both the Phylloceratina and Lytoceratina gave rise to various stocks combined in the Ammonitina.
These four suborders are further divided into different stocks, comprising various families combined into superfamilies. Some like the Hildoceratoidea and Stephanoceratoidea are restricted to the Jurassic. Others like the Hoplitoidea and Acanthoceratoidea are known only from the Cretaceous. Still others like the Perisphinctoidea are found in both.Bonatitan
Bonatitan is a genus of titanosaurian dinosaur from the Late Cretaceous Allen Formation of Argentina.Cerapoda
Cerapoda ("ceratopsians and ornithopods") is a clade of the dinosaur order Ornithischia.Chelydridae
The Chelydridae are a family of turtles that has seven extinct and two extant genera. The extant genera are the snapping turtles Chelydra and Macrochelys. Both are endemic to the Western Hemisphere. The extinct genera are Acherontemys, Chelydrops, Chelydropsis, Emarginachelys, Macrocephalochelys, Planiplastron, and Protochelydra.Elasmaria
Elasmaria is a clade of iguanodont ornithopods known from Cretaceous deposits in South America, Antarctica, and Australia.Harrana
Harrana, named after Qasr Kharana, an archeological Umayyad desert palace in the area, is part of the Jordan eastern plateau some 60 kilometers southeast of Amman city.
The area is largely uninhabited except for seasonal bedouin sheep and camel herders who bring their livestock to the area during December through April.
Harrana's climate, much like the other parts of the country, is influenced by the moderate Mediterranean climate from the west, the very hot Sahara's climate from the east, and the cold European climate from the north.
Though arid, the area is rich in animal life. Birds, owls, rodents, rabbits, foxes, occasional wolves and hyenas, snakes, and lizards are some of the animals that take refuge in Harrana. A variety of flowering plants bloom during late winter–early spring months including mustard plants, oriental popies, and wild irisis. Cistanche tubulosa, or the desert broomrape, is also another beautiful resident in Harrana blooming towards the end of spring and beginning of summer.
Harrana is significant for its fossil deposits preserved in gigantic limestone concretions that date back to the latest Maastrichtian some 66–67 million years ago, a period notably close to the end-Cretaceous extinction events when many groups of animals such as dinosaurs and as much as 65–70% of all marine animal species became extinct. Mosasaur specimens along with their remarkably well preserved scale imprints have been discovered from late Maastrichtian deposits of the Muwaqqar Chalk Marl Formation of Harrana
The best preserved and complete specimens of the extinct teleostean fish genus Saurocephalus and the most complete mosasaur Carinodens remains come from the latest Maastrichtian of Harrana.Magyarosaurus
Magyarosaurus ("Magyar lizard") is a genus of dwarf sauropod dinosaur from late Cretaceous Period (early to late Maastrichtian) in Romania. It is one of the smallest-known adult sauropods, measuring only six meters in length. The type and only certain species is Magyarosaurus dacus. It has been found to be a close relative of Rapetosaurus in the family Saltasauridae in the sauropod clade Titanosauria in a 2005 study.Nodosauridae
Nodosauridae is a family of ankylosaurian dinosaurs, from the Late Jurassic to the Late Cretaceous Period of what are now North America, Europe, Asia, Africa, and Antarctica.Novialoidea
Novialoidea (meaning "new wings") is an extinct clade of macronychopteran pterosaurs that lived from the latest Early Jurassic to the latest Late Cretaceous (early Toarcian to late Maastrichtian age), their fossils having been found on all continents except Antarctica. It was named by Alexander Wilhelm Armin Kellner in 2003 as a node-based taxon consisting of the last common ancestor of Campylognathoides, Quetzalcoatlus and all its descendants. This name was derived from Latin novus "new", and ala, "wing", in reference to the wing synapomorphies that the members of the clade possess. Unwin (2003) named Lonchognatha in the same issue of the journal that published Novialoidea (Geological Society of London, Special Publications 217) and defined it as Eudimorphodon ranzii, Rhamphorhynchus muensteri, their most recent common ancestor and all its descendants (as a node-based taxon). Under Unwin's and Kellner's phylogenetic analyses (where Eudimorphodon and Campylognathoides form a family that basal to both Rhamphorhynchus and Quetzalcoatlus), and because Novialoidea was named first (in pages 105-137, while Lonchognatha was named in pages 139-190), Lonchognatha is an objective junior synonym of the former. However, other analyses find Lonchognatha to be valid (Andres et al., 2010) or synonymous with the Pterosauria (Andres, 2010 and Andres, in press).Olorotitan
Olorotitan was a genus of lambeosaurine duckbilled dinosaur from the middle or latest Maastrichtian-age Late Cretaceous, whose remains were found in the Udurchukan Formation beds of Kundur, Amur Region, Far Eastern Russia. The type, and only species is Olorotitan arharensis.Ornithopod
Ornithopods () or members of the clade Ornithopoda ( or ) are a group of ornithischian dinosaurs that started out as small, bipedal running grazers, and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world, and dominated the North American landscape. Their major evolutionary advantage was the progressive development of a chewing apparatus that became the most sophisticated ever developed by a non-avian dinosaur, rivaling that of modern mammals such as the domestic cow. They reached their apex in the duck-bills (hadrosaurs), before they were wiped out by the Cretaceous–Paleogene extinction event along with all other non-avian dinosaurs. Members are known from all seven continents, though they are generally rare in the Southern Hemisphere.Paludititan
Paludititan is a genus of herbivorous titanosaurian dinosaur which lived in the area of present Romania during the Late Cretaceous. It existed in the island ecosystem known as Hațeg Island.Parksosaurus
Parksosaurus (meaning "William Parks's lizard") is a genus of hypsilophodont ornithopod dinosaur from the early Maastrichtian-age Upper Cretaceous Horseshoe Canyon Formation of Alberta, Canada. It is based on most of a partially articulated skeleton and partial skull, showing it to have been a small, bipedal, herbivorous dinosaur. It is one of the few described non-hadrosaurid ornithopods from the end of the Cretaceous in North America, existing around 70 million years ago.Poales
The Poales are a large order of flowering plants in the monocotyledons, and includes families of plants such as the grasses, bromeliads, and sedges. Sixteen plant families are currently recognized by botanists to be part of Poales.Rhabdodon
Rhabdodon (meaning "fluted tooth") is a genus of ornithopod dinosaur that lived in Europe approximately 70–66 million years ago in the Late Cretaceous. It is similar in build to a very robust "hypsilophodont" (non-iguanodont ornithopod), though all modern phylogenetic analyses find this ("Hypsilophodontia/tidae") to be an unnatural grouping, and Rhabdodon to be a basal member of Iguanodontia.Rocasaurus
Rocasaurus (meaning "Roca lizard") is a genus of titanosaurian sauropod that lived in South America. Rocasaurus was discovered in Argentina in 2000, within the Allen Formation which is dated to be middle Campanian to early Maastrichtian in age (75 to 70 million years ago in the Late Cretaceous). This genus grew up to 8 metres (26 ft) long, making it one of the smaller sauropods. It seems to be closely related to saltasaurid dinosaurs, like Saltasaurus and Neuquensaurus.
The type species, Rocasaurus muniozi, was formally described by Salgado and Azpilicueta in 2000.Sauropterygia
Sauropterygia ("lizard flippers") is an extinct, diverse taxon of aquatic reptiles that developed from terrestrial ancestors soon after the end-Permian extinction and flourished during the Triassic before all except for the Plesiosauria became extinct at the end of that era. The plesiosaurs would continue to diversify till the end of the Mesozoic. Sauropterygians are united by a radical adaptation of their pectoral girdle, adapted to support powerful flipper strokes. Some later sauropterygians, such as the pliosaurs, developed a similar mechanism in their pelvis.Sphaerium beckmani
Sphaerium beckmani is an extinct species of fossil freshwater pea clams from the Late Cretaceous deposits of North America. This species was first described by the American paleontologist Loris Shano Russell in 1976. The specimens were collected by the American paleontologist Karl M. Waage from 1961 to 1962 from the Hell Creek Formation of eastern Montana. The locality is dated to the late Maastrichtian Age (around 66.0 to 72.1 million years ago).Telmatosaurus
Telmatosaurus (meaning "marsh lizard") is a genus of basal hadrosaurid dinosaur from the Late Cretaceous. It was a relatively small hadrosaur, approximately five meters (16 ft) long, found in what is now Romania.