| Serpukhovian | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 330.9 ± 0.2 – 323.2 ± 0.4Ma | |||||||||||||||
 Paleogeography of the mid Serpukhovian, 325 Ma | |||||||||||||||
| Chronology | |||||||||||||||
| |||||||||||||||
| 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 | Not formally defined | ||||||||||||||
| Lower boundary definition candidates | FAD of theconodontLochriea ziegleri | ||||||||||||||
| Lower boundary GSSP candidate section(s) | |||||||||||||||
| Upper boundary definition | FAD of theconodontDeclinognathodus nodiliferus | ||||||||||||||
| Upper boundary GSSP | Arrow Canyon,Nevada,USA 36°44′00″N114°46′40″W / 36.7333°N 114.7778°W /36.7333; -114.7778 | ||||||||||||||
| Upper GSSP ratified | 1996[2] | ||||||||||||||
TheSerpukhovian is in theICSgeologic timescale the uppermoststage or youngestage of theMississippian, the lowersubsystem of theCarboniferous. The Serpukhovian age lasted from 330.3 Ma to 323.4Ma.[3] It is preceded by theVisean and is followed by theBashkirian. The Serpukhovian correlates with the lower part of theNamurian Stage of European stratigraphy and the middle and upper parts of theChesterian Stage of North American stratigraphy.[4]
The Serpukhovian Stage was proposed in 1890 by Russian stratigrapherSergei Nikitin and was introduced in the official stratigraphy of European Russia in 1974.[5][6] It was named after the city ofSerpukhov, nearMoscow. The ICS later used the upper Russian subdivisions of the Carboniferous in its international geologic time scale.
The base of the Serpukhovian is informally defined by the first appearance of theconodontLochriea ziegleri, though the utility and systematic stability of this species is not yet certain. No lowerGSSP has been assigned to the Serpukhovian Stage yet. Two candidate GSSPs have been proposed: the Verkhnyaya Kardailovka section in the SouthUrals ofRussia, and the Naqing (Nashui) section inGuizhou,China.[4]
The top of the stage (the base of thePennsylvanian subsystem and Bashkirian stage) is at the first appearance of the conodontDeclinognathodus nodiliferus in the lowerBird Spring Formation, which overlies theBattleship Formation in Nevada.[7] It is also slightly above the first appearance of theforamGlobivalvulina bulloides, genozone of theammonoidgenusHomoceras and the ammonoidbiozone ofIsohomoceras subglobosum.[8]
In Europe, the Serpukhovian Stage includes three conodont biozones: theGnathodus postbilineatus Zone (youngest),Gnathodus bollandensis Zone, andLochriea ziegleri Zone (in part, oldest).There are threeforaminifera biozones: theMonotaxinoides transitorius Zone (youngest),Eostaffellina protvae Zone, andNeoarchaediscus postrugosus Zone (oldest).
In North America, the stage encompassed four conodont biozones: theRhachistognathus muricatus Zone (youngest),Adetognathus unicornis Zone,Cavusgnathus naviculus Zone, andGnathodus bilineatus Zone (in part, oldest).
In the regional stratigraphy of Russia (and Eastern Europe as a whole), the Serpukhovian is subdivided into four substages, from oldest to youngest: the Tarusian, Steshevian, Protvian, and Zapaltyubian. The former three are found in theMoscow Basin and are named after places near Serpukhov (Tarusa andProtva). Strata belonging to the Zapaltyubian are not exposed in the Moscow Basin, though they are found in theDonets Basin and theUrals.[4]
In the regional stratigraphy of the United Kingdom (and Western Europe as a whole), the Serpukhovian corresponds to the lower half of theNamurian regional stage. This portion of the Namurian includes three substages, from oldest to youngest: the Pendleian, Arnsbergian and Chokierian. Only the lowermost Chokierian falls in the Serpukhovian, the upper part of the substage corresponds to the earliestBashkirian.[9][4]
In North America, the Serpukhovian corresponds to the upper part of theChesterian regional stage, while inChina the Serpukhovian is roughly equivalent to the Dewuan regional stage.[4]
The largest extinction event of the Carboniferous Period occurred in the early Serpukhovian. This extinction came in the form of ecological turnovers, with the demise of diverse Mississippian assemblages ofcrinoids andrugose corals. After the extinction, they were replaced by species-poor cosmopolitan ecosystems. The extinction selectively targeted species with a narrow range of temperature preferences, as cooling seawater led to habitat loss for tropical specialists.[10] Ammonoids appear to have not been impacted by this event, as they reached a zenith in diversity at this time.[11] The long-term ecological impact of the Serpukhovian extinction may have exceeded that of theOrdovician-Silurian extinction, where taxonomic diversity was abruptly devastated but quickly recovered to pre-extinction levels.[12][13][14]
Sepkoski (1996) plotted an extinction rate of around 23-24% for the Serpukhovian as a whole, based on marinegenera which persist through multiple stages.[15] Bambach (2006) found an early Serpukhovian extinction rate of 31% among all marine genera.[16] Using anextinction probability procedure generated from thePaleobiology Database, McGheeet al. (2013) estimated an extinction rate as high as 39% for marine genera.[13] On the other hand, Stanley (2016) estimated that the extinction was much smaller, at a loss of only 13-14 % of marine genera.[17]
Relative to other biological crises, the Serpukhovian extinction was much more selective in its effects on different evolutionary faunas. Stanley (2007) estimated that the early Serpukhovian saw the loss of 37.5% of marine genera in thePaleozoic evolutionary fauna. Only 15.4% of marine genera in themodern evolutionary fauna would have been lost along the same time interval.[18] This disconnect, and the severity of the extinction as a whole, is reminiscent of theLate Devonian extinction events. Another similarity is how the Serpukhovian extinction was seemingly driven by low rates of speciation, rather than particularly high rates of extinction.[19][12]
It is disputed whether the aftermath of the extinction saw a relative stagnation of biodiversity or a major increase. Some studies have found that in the followingLate Paleozoic Ice Age (LPIA) of theLate Carboniferous andEarly Permian, both speciation and extinction rates were low,[19][20] with this stagnation in biological diversity driven by a reduction of carbonate platforms, which otherwise would have helped to maintain high biodiversity.[21] More recent studies have instead shown that biodiversity surged during the LPIA in what is known as theCarboniferous-Earliest Permian Biodiversification Event (CPBE).[22][23] Foraminifera especially saw extremely rapid diversification.[24] The CPBE's cause may have been the dramatically increased marine provincialism caused by sea level fall during the LPIA combined with the assembly of Pangaea, which limited the spread of taxa from one region of the world ocean to another.[22]
