| Danian | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 66.0 – 61.6Ma | |||||||||||||
| Chronology | |||||||||||||
| |||||||||||||
| Formerly part of | TertiaryPeriod/System | ||||||||||||
| Etymology | |||||||||||||
| Name formality | Formal | ||||||||||||
| Usage information | |||||||||||||
| Celestial body | Earth | ||||||||||||
| Regional usage | Global (ICS) | ||||||||||||
| Time scale(s) used | ICS Time Scale | ||||||||||||
| Definition | |||||||||||||
| Chronological unit | Age | ||||||||||||
| Stratigraphic unit | Stage | ||||||||||||
| Time span formality | Formal | ||||||||||||
| Lower boundary definition | Iridium enriched layer associated with a major meteorite impact and subsequentK–Pg extinction event[3] | ||||||||||||
| Lower boundary GSSP | El Kef Section,El Kef,Tunisia 36°09′13″N8°38′55″E / 36.1537°N 8.6486°E /36.1537; 8.6486[3] | ||||||||||||
| Lower GSSP ratified | 1991[3] | ||||||||||||
| Upper boundary definition | Onset of sea-level drop and carbon isotope shift | ||||||||||||
| Upper boundary GSSP | Zumaia Section,Basque Country,Spain 43°17′57″N2°15′40″W / 43.2992°N 2.2610°W /43.2992; -2.2610 | ||||||||||||
| Upper GSSP ratified | 2008[4] | ||||||||||||
TheDanian is the oldestage or loweststage of thePaleocene Epoch orSeries, of thePaleogene Period orSystem, and of theCenozoic Era orErathem. The beginning of the Danian (and the end of the precedingMaastrichtian) is at theCretaceous–Paleogene extinction event66 Ma. The age ended61.66 Ma, being followed by theSelandian.[5]
The Danian was introduced in scientific literature byGerman-Swiss geologistPierre Jean Édouard Desor in 1847 following a study of fossils found in France and Denmark.[6] He identified this stage in deposits fromFaxe andMøns Klint and named it after theLatin name forDenmark.[6] TheMontian Stage fromBelgian stratigraphy (named after the city ofMons) is now known to be roughly equivalent to the Upper Danian and is considered ajunior synonym and is no longer in use.[7]
The base of the Danian is defined at theiridium anomaly which characterized theCretaceous–Paleogene boundary (K–T boundary) in stratigraphic sections worldwide. A section inEl Kef,Tunisia was appointed as a reference profile (GSSP) for this important boundary.[8] The Danian is the oldest age of the Paleocene, defined at its base by the K-Pg boundary. It is very important because the readily recognized iridium anomaly and primitive Danian planktonic foraminifers define the base of the Danian. Danianforaminiferans repopulated the Paleocene seas after the Cretaceous mass extinction (Olsson et al., 1996). The first replacement foraminiferan of the Paleogene is theGlobigerina eugubina, which is used to define the base of the Danian Age (Stainforth et al., 1975). This foraminiferan replaced the Cretaceous genusGlobotruncana.
The top of the Danian Stage (the base of the Selandian) is close to the boundary betweenbiozones NP4 and NP5 from marinebiostratigraphy. It is slightly after the first appearances of many new species of the calcareousnanoplankton genusFasciculithus (F. ulii,F. billii,F. janii,F. involutus,F. tympaniformis andF. pileatus) and close to the first appearance of calcareousnanoplankton speciesNeochiastozygus perfectus.
The Danian Stage overlaps thePuercan andTorrejonianNorth American land mammal ages and the Shanghuan and lowest part of the NongshanianAsian land mammal ages. It includes the oldestMammal Paleogene zones, all included in the 1 - 5 group.[9]
Though the non-aviandinosaurs were gone, the mammals and other land animals remained small, most not even bigger than a sheep; however; a few (likeAnkalagon saurognathus) reached the size of a medium-sized bear. Numerous lineages ofmodern birds also survived, particularly in the area aroundAustralia but also elsewhere, e.g.Scaniornis of theNorth Sea region. The oceans remained much the same as theLate Cretaceous seas, only that there was less life, few remaining marinereptiles (mostlyturtles,choristodera andcrocodiles), and other lesser-known animals.
There arecontroversial reports ofammonites (mainly of theScaphitidae class inTurkmenistan)[10] still being around at this time, although they did not survive the Danian age.[11]
Close to the end of the Danian, around 62.2 Ma, occurred a hyperthermal, similar to but smaller in magnitude compared to the more famousPalaeocene-Eocene Thermal Maximum (PETM),[12] known as the Latest Danian Event (LDE).[13] The event, which took place over a 170-230 kyr time interval,[14] is evidenced in the geologic record by two negative carbon isotope excursions and is believed to have led to a 2–3 °C (3.6–5.4 °F) warming of both deep and surface seawater.[15] This hyperthermal also led to a shallowing of the oceaniclysocline, as evidenced by the significant decrease in calcium carbonate preservation.[13]
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