The Cenomanian is, in the ICS' geological timescale the oldest or earliest age of the Late Cretaceous epoch or the lowest stage of the Upper Cretaceous series. An age is a unit of geochronology: it is a unit of time; the stage is a unit in the stratigraphic column deposited during the corresponding age. Both age and stage bear the same name.
As a unit of geologic time measure, the Cenomanian age spans the time between 100.5 ± 0.9 Ma and 93.9 ± 0.8 Ma (million years ago). In the geologic timescale it is preceded by the Albian and is followed by the Turonian. The Upper Cenomanian starts approximately at 95 M.a.
|Subdivision of the Cretaceous system|
according to the ICS, as of 2017.
The Cenomanian was introduced in scientific literature by French palaeontologist Alcide d'Orbigny in 1847. Its name comes from the New Latin name of the French city of Le Mans (département Sarthe), Cenomanum.
The base of the Cenomanian stage (which is also the base of the Upper Cretaceous series) is placed at the first appearance of foram species Rotalipora globotruncanoides in the stratigraphic record. An official reference profile for the base of the Cenomanian (a GSSP) is located in an outcrop at the western flank of Mont Risou, near the village of Rosans in the French Alps (département Hautes-Alpes, coordinates: 44°23'33"N, 5°30'43"E). The base is, in the reference profile, located 36 meters below the top of the Marnes Bleues Formation.
The late Cenomanian represents the highest mean sea-level observed in the Phanerozoic eon, the past six hundred million years (approximately one hundred and fifty meters above present day sea-levels). A corollary is that the highlands were at all time lows, so the landscape on Earth was one of warm broad shallow seas inundating low-lying land areas on the precursors to today's continents. What few lands rose above the waves were made of old mountains and hills, upland plateaus, all much weathered. Tectonic mountain building was minimal and most continents were isolated by large stretches of water. Without highlands to brake winds, the climate would have been windy and waves large, adding to the weathering and fast rate of sediment deposition.
The crown-group Crocodylia, the true-crocodiles, first appear during the Cenomanian.
|Belemnites of the Cenomanian|
Aegyptosaurus meaning 'Egypt’s lizard', for the country in which it was discovered (Greek sauros meaning 'lizard') is a genus of sauropod dinosaur believed to have lived in what is now Africa, around 95 million years ago, during the mid- and late-Cretaceous Period (Albian to Cenomanian stages). Like most sauropods, it had a long neck and a small skull. The animal's long tail probably acted as a counterweight to its body mass. Aegyptosaurus was a close relative of Argentinosaurus, a much larger dinosaur found in South America.
Aegyptosaurus was described by German paleontologist Ernst Stromer in 1932. Its fossils have been found in Egypt, Niger (Farak Formation), and in several different locations in the Sahara Desert. All known examples were discovered before 1939. The fossils were stored together in Munich, but were obliterated when an Allied bombing raid destroyed the museum where they were kept in 1944, during World War II.Albian
The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous epoch/series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± 0.9 Ma (million years ago). The Albian is preceded by the Aptian and followed by the Cenomanian.Carcharodontosaurus
Carcharodontosaurus is a genus of carnivorous carcharodontosaurid dinosaurs that existed during the Cenomanian stage of the mid-Cretaceous Period. It is currently known to include two species: C. saharicus and C. iguidensis, which were among the larger theropods, nearly as large as or even larger than Tyrannosaurus, Giganotosaurus and Spinosaurus.
The genus Carcharodontosaurus is named after the shark genus Carcharodon, itself composed of the Greek karchar[os] (κάρχαρος, meaning "jagged" or "sharp") and odōn (ὀδών, "teeth"), and the suffix -saurus ("lizard").Cathartesaura
Cathartesaura is a genus of rebbachisaurid sauropod dinosaur hailing from the Late Cretaceous strata of the Huincul Formation, at the "La Buitrera" locality, in the Neuquén Basin of Río Negro Province, Argentina. The fossil remains, described by Gallina and Apesteguía in 2005, consist of a partial skeleton including vertebrae and limb bones. These were found at the base of the formation, which spans the Cenomanian and Coniacian epochs, in mudstone and sandstone levels.Cenomanian-Turonian boundary event
The Cenomanian-Turonian boundary event, or the Cenomanian-Turonian extinction event, the Cenomanian-Turonian anoxic event (OAE 2), and referred also as the Bonarelli Event, was one of two anoxic extinction events in the Cretaceous period. (The other being the earlier Selli Event, or OAE 1a, in the Aptian.) The OAE 2 occurred approximately 91.5 ± 8.6 Ma, though other estimates are given as 93–94 Ma. The Cenomanian-Turonian boundary has recently been refined to 93.9 ± 0.15 Ma There was a large carbon disturbance during this time period. However, apart from the carbon cycle disturbance, there were also large disturbances in the oxygen and sulfur cycles of the ocean.
The event brought about the extinction of the Pliosauridae, and most Ichthyosauria. Coracoids of Maastrichtian age were once interpreted by some authors as belonging to ichthyosaurs, but these have since been interpreted as plesiosaur elements instead. Although the cause is still uncertain, the result starved the Earth's oceans of oxygen for nearly half a million years, causing the extinction of approximately 27 percent of marine invertebrates, including certain planktic and benthic foraminifera, mollusks, bivalves, dinoflagellates and calcareous nannofossils. The global environmental disturbance that resulted in these conditions increased atmospheric and oceanic temperatures. Boundary sediments show an enrichment of trace elements, and contain elevated δ13C values.The Cenomanian and Turonian stages were first noted by D'Orbigny between 1843 and 1852. The global type section for this boundary is located in the Bridge Creek Limestone Member of the Greenhorn formation near Pueblo, Colorado, which are bedded with the Milankovitch orbital signature. Here, a positive carbon-isotope event is clearly shown, although none of the characteristic, organic-rich black shale is present. It has been estimated that the isotope shift lasted approximately 850 kyrs longer than the black shale event, which may be the cause of this anomaly in the Colorado type-section. A significantly expanded OAE2 interval from southern Tibet documents a complete, more detailed, and finer-scale structures of the positive carbon isotope excursion that contains multiple shorter-term carbon isotope stages amounting to a total duration of 820±25 kyrs.The boundary is also known as the Bonarelli event because of 1- to 2-meter layer of thick black shale that marks the boundary and was first studied by Guido Bonarelli in 1891. It is characterized by interbedded black shale, chert and radiolarian sands is estimated to span a 400,000-year interval. Planktic foraminifera do not exist in this Bonarelli level, and the presence of radiolarians in this section indicates relatively high productivity and an availability of nutrients.
One possible cause of this event is sub-oceanic volcanism, possibly the Caribbean large igneous province, with increased activity approximately 500,000 years earlier. During that period, the rate of crustal production reached its highest level for 100 million years. This was largely caused by the widespread melting of hot mantle plumes under the oceans at the base of the lithosphere. This resulted in the thickening of the oceanic crust in the Pacific and Indian Oceans. This volcanism would have sent large quantities of carbon dioxide into the atmosphere, leading to global warming. Within the oceans, the emission of SO2, H2S, CO2, and halogens would have increased the acidity of the water, causing the dissolution of carbonate, and a further release of carbon dioxide. When the volcanic activity declined, this run-away greenhouse effect would have likely been put into reverse. The increased CO2 content of the oceans could have increased organic productivity in the ocean surface waters. The consumption of this newly abundant organic life by aerobic bacteria would produce anoxia and mass extinction. The resulting elevated levels of carbon burial would account for the black shale deposition in the ocean basins.Elaltitan
Elaltitan is an extinct genus of large lithostrotian titanosaur sauropod known from the Late Cretaceous (mid Cenomanian to Turonian stage) of Chubut Province, southern Argentina. It contains a single species, Elaltitan lilloi.Emydidae
Emydidae is a family of testudines (turtles) which includes close to 50 species in 10 genera. Members of this family are commonly called terrapins, pond turtles, or marsh turtles. Several species of Asian box turtle were formerly classified in the family; however, revised taxonomy has separated them to a different family (Geoemydidae). As currently defined, Emydidae is entirely a Western Hemisphere family, with the exception of two species of pond turtle.Ichthyornithes
Ichthyornithes is an extinct group of toothed avialans very closely related to the common ancestor of all modern birds. They are known from fossil remains found throughout the late Cretaceous period of North America, though only one species, Ichthyornis dispar, is represented by complete enough fossils to have been named. Ichthyornitheans became extinct at the Cretaceous–Paleogene boundary, along with enantiornitheans, all other non-avian dinosaurs, and many other animal and plant groups.Itapeuasaurus
Itapeuasaurus (meaning "Itapeua lizard") is a genus of rebbachisaurid sauropod dinosaur from the Alcântara Formation from Maranhão in Brazil. The type and only species is Itapeuasaurus cajapioensis. It would have been around 10 metres (33 ft) to 15 metres (49 ft) when fully grown.Limaysaurus
Limaysaurus (“Limay lizard”) is a genus represented by a single species of rebbachisaurid sauropod dinosaurs, which lived during the mid-Cretaceous period, about 99.6 and 97 million years ago, in the Cenomanian, in what is now South America (northwestern Patagonia).Majoidea
The Majoidea are a superfamily of crabs which includes the various spider crabs.Megalosauroidea
Megalosauroidea (meaning 'great/big lizard forms') is a superfamily (or clade) of tetanuran theropod dinosaurs that lived from the Middle Jurassic to the Late Cretaceous period. The group is defined as Megalosaurus bucklandii and all taxa sharing a more recent common ancestor with it than with Allosaurus fragilis or Passer domesticus. Members of the group include Spinosaurus, Megalosaurus, and Torvosaurus.Mesoparapylocheles
Mesoparapylocheles is an extinct hermit crab genus which existed during the Mesozoic in what is now Europe. It was described by René H.B. Fraaije, Adiël A. Klompmaker and Pedro Artal in 2012. The type species is Mesoparapylocheles michaeljacksoni from the Albian or Cenomanian of Spain; it was named after the singer Michael Jackson. Genus also includes two species (M. jaegeri and M. schweigerti) from the Late Jurassic (Kimmeridgian) of Germany and additional two species (M. strouhali and M. zapfei) from the Late Jurassic (Tithonian) of Austria.Mnyamawamtuka
Mnyamawamtuka (pronounced Mm-nya-ma-wah-mm-too-ka; meaning "beast of the Mtuka river drainage" in Kiswahili) is a genus of lithostrotian titanosaur dinosaur from the Late Cretaceous Galula Formation in Tanzania. The type and only species is M. moyowamkia.Oryctodromeus
Oryctodromeus (meaning "digging runner") was a genus of small parksosaurid dinosaur. Fossils are known from the middle Cretaceous Blackleaf Formation of southwestern Montana and the Wayan Formation of southeastern Idaho, USA, both of the Cenomanian stage, roughly 95 million years ago. A member of the small, presumably fast-running herbivorous family Parksosauridae, Oryctodromeus is the first dinosaur published that shows evidence of burrowing behavior.Polycotylidae
Polycotylidae is a family of plesiosaurs from the Cretaceous, a sister group to Leptocleididae.
With their short necks and large elongated heads, they resemble the pliosaurs, but closer phylogenetic studies indicate that they share many common features with the Plesiosauridae and Elasmosauridae. They have been found worldwide, with specimens reported from New Zealand, Australia, Japan, Morocco, the US, Canada, Eastern Europe, and South America.Rayososaurus
Rayososaurus is a genus of plant-eating sauropod dinosaur of the superfamily Diplodocoidea. It was found in the Candeleros Formation, but was named Rayososaurus after the Rayoso Member, which later has been elevated to the older Rayoso Formation. The formations are located in the Neuquén Basin of northern Patagonia, Argentina. Rayososaurus lived during the Cenomanian epoch of the Late Cretaceous, about 99 to 96 million years ago. The type species is R. agrioensis, named by Argentinian paleontologist José Bonaparte in 1996. The species epithet agrioensis refers to the Agrio del Medio locality.Turonian
The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous epoch, or a stage in the Upper Cretaceous series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded by the Cenomanian stage and underlies the Coniacian stage.At the beginning of the Turonian an anoxic event took place which is called the Cenomanian-Turonian boundary event or the "Bonarelli Event".Weewarrasaurus
Weewarrasaurus is a genus of ornithopod dinosaur from the Late Cretaceous of the Griman Creek Formation near Lightning Ridge, in New South Wales, Australia. The type and only species is W. pobeni, known from the holotype, an isolated dentary preserved in opal, as well as a secondary referred dentary. It is thought to have co-existed with multiple other ornithopods of different sizes and lineages.
(541.0 Mya–2.5 Gya)
|Archean eon (2.5–4 Gya)|
|Hadean eon (4–4.6 Gya)|