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The '''Epoch of Extreme Inundations''' (EEI) is a hypothetical [[Epoch (geology)|epoch]] during which four [[landform]]s in the [[Pontic–Caspian steppe]]—marine lowlands (marine transgressions), river valleys ([[outburst flood]]s), [[marine transgression]]s (thermocarst lakes) and slopes ([[solifluction]] flows)—were widely inundated.<ref>The dynamics of landscape components and inner marine basins of Northern Eurasia over the past 130,000 years. Edited by A.A. Svitoch. GEOS. Moscow. Russia. 2002. ISBN 5-89118-268-8</ref> Catastrophic events during the epoch are theorized to have influenced prehistoric human life.

=={{anchor|History of investigation}}Research history==
In 2002, Russian geographer Andrey L. Chepalyga of the Institute of Geography at the [[Russian Academy of Sciences]] formulated the theory<ref name="Epoch of Extremal Inundations">[http://www.avalon-institute.org/IGCP/doc/ProgramIGCP2009.pdf Chepalyga A.L., H. Arslanov, T. Yanina. Detailed age control of Khvalynean basin history. Collection papers of Intern. geosciens programme conference, project 521 "Black Sea -Mediterranean corridor" Izmir 2009 p.p. 71-75]</ref><ref name="Extremal Inundations">[http://www.avalon-institute.org/IGCP/doc/OdessaAbstract.pdf Chepalyga A.L. Epoch of Extremal Floodings and human adaptation in the North Black Sea basin. Second Plenary Meeting and Field Trip of Project IGCP 521 "Black Sea-Mediterranean Corridor during last 30 ky: Sea level change and human adaptation", Odessa, Ukraine, August 20-28, 2006]</ref> to explain natural events, with field investigation and laboratory work supporting the theory. Archaeological data indicated that the period impacted human life. During the first stage of research, sources were examined for extreme hydro-climatic events between 16000 and 18000 BCE in the [[Caspian Sea|Caspian drainage basin]]. Research focused on sources of water for these events, such as [[megaflood]]s in river valleys and melting permafrost augmenting watersheds. The investigation's second stage included chronological correlation of the events using [[Stratigraphy (archaeology)|stratigraphy]], [[geomorphology]] and [[radiocarbon dating]]. This was followed by paleohydrologic reconstruction of the basins, including their level, area, volume and water exchange between basins. Based on archeological data, the influence of the events on prehistoric human life was studied. The investigation aimed to comprehensively describe the period.

==Time and place==
During the [[deglaciation]] following the [[Last Glacial Maximum]], northwestern [[Eurasia]] experienced widespread flooding from the [[Atlantic Ocean]] to the [[Yenisei River]],  including the [[subarctic]] and [[Himalayas]]: over {{convert|10000000|km2|sqmi}}. Flooding occurred in four [[landform]]s: marine lowlands, river valleys, watersheds and slopes, and peaked 17,000 to 15,000 years ago.

==Geology==
The basins' bottom and [[Littoral zone|littoral]] sediments and their [[fossil]]s contain geological evidence of the EEI. In the [[Caspian Sea|Caspian basin]], bottom sediments attributable to the epoch differ from the under- and overlying layers in a number of ways<ref>Badyukova E.N. (2000). Genesis of the Khvalynian (Pleistocene) chocolate clays of Northern Caspian region. Buil. Moscow Soc. Naturalists. Sect. geol. V.75, 5. pp. 25–31</ref><ref>Chistyakova I.A. (2001) Material composition of the early Khvalynian sediments. Buil. Com. Quat Res. 64. pp. 61–69. (In Russian)</ref><ref>Leontyev O.K., Maev E.G., Rychagov G.I. 1977. Geomorphology of coasts and floor of the Caspian Sea. . Moscow: Moscow University Press. (In Russian</ref> and are called "chocolate clays" because of their reddish-brown color. The chocolate clays and related Khvalynean sediments are usually {{convert|3|–|5|m}}, occasionally exceeding {{convert|20|–|25|m}}. They are primarily limited to the [[Caspian Depression]], from the modern Caspian coast to the foothills of the surrounding mountains.

===Stratigraphy===
In the marine sequence of the Caspian basin, the Khvalynean layers are above the Late Khazarian ones (which date to the last interglacial period) and below the New Caspian (Holocene) deposits. They are separated from the Lower Khazarian series by continental Atelian layers synchronous to marine sediments from the Atelian basin. The level of the latter was {{convert|110|–|120|m}} below the present Caspian level—in other words, {{convert|140|-|150|m}} below sea level.<ref>Lokhin M.Yu., Maev E.G. (1990) The late Pleistocene deltas on the northern shelf of the Northern Caspian Sea. Vestnik MGU, Ser. Geogr. 3, 34–40. (In Russian)</ref><ref>Maev E.G. (1994) Caspian regressions: their place in the Quaternary history of the Caspian Sea and impact on the sea floor relief formation. Geomorphologiya. 2, 94–101. (In Russian)</ref> In the Caspian Depression, the Khvalynean sediments occur primarily near the surface; younger still (and higher in the sequence) are the [[Holocene]] floodplain [[Lacustrine deposits|lacustrine]] and marine (New Caspian) sediments.

EEI deposits in the [[Black Sea]] basin occur in the New Euxinian series. On the continental slope and in the deep-sea basin, they are a light reddish-brown and a pale yellow mud {{convert|.5|–|1|m|in}} thick.<ref>Ryan W.B.F., Pitman W.C.I., Major C.O., Shimkus K., Moskalenko V., et al. 1997. An abrupt drowning of the Black Sea shelf. Mar. Geol. 138: 119–26</ref> In color they resemble the chocolate clays of the Caspian basin, and their age is near that of the latter (15,000 BP).

===Fossils===
Indicators of an EEI are brackish-water mollusk species close to modern North Caspian ones. Among these are Caspian [[Endemism|endemic]] species of the ''Limnocardiidae'' family, such as the Didacna Eichwald genus.<ref>Nevesskaya L.A. (1965) Late Quaternary bivalve mollusks of the Black Sea: their systematics and ecology. Acad. nauk SSSR Paleont. Inst. Trudy 105: 1–390 (In Russian)</ref> Although the latter is not presently found outside the Caspian Sea, it occurred widely in the Azov—Black Sea basin during the Pleistocene until the Karangatian era.{{cn|date=January 2016}}

[[Gastropoda|Gastropods]] are represented by the Caspian endemic genera ''[[Caspia]]'' and ''[[Hydrobiidae|Micromelania]]''. Shells of the Early Khvalynean complex are distinguished by their small size (two to three times smaller than present ones) and thin walls. The complex is usually considered as a product of cold climate and low salinity. New Black Sea sediments contain mollusks of the Caspian type.<ref>Algan O., Cagatay N., Tchepalyga A., Ongan D., Eastoe C., Gokasan E. (2001) Stratigraphy of the sediment fill in Bosphorus Strait: water exchange between the Black and Mediterranean Seas during the last glacial – Holocene. Geo.-Mar.Lett. 20:209-18</ref>

=={{anchor|Cascade of Eurasians basins}}Eurasian basins==
===Marine basins and spillways===
Marine transgressions in the Black and Caspian Sea basins formed a number of sea-lakes (the [[Aral Sea|Aral]], Caspian and Black Seas and the [[Sea of Marmara]]) connected by spillways:<ref>Popov G.I. Pleistocene of the Black Sea–Caspian straits. Moscow: Nauka Press. 215 pp. 1983.</ref> the [[Uzboy River]], the [[Kuma–Manych Depression]], the [[Bosphorus]] and the [[Dardanelles]]. The large basin covered about {{convert|1500000|km2|sqmi}} and held up to 700,000&nbsp;km<sup>3</sup> of water and 5000&nbsp;km<sup>3</sup> (10 billion tons) of salt. Discharging more than 60,000&nbsp;m<sup>3</sup> per second, it ran 3,000&nbsp;km west to east (from the [[Mediterranean]] to Central [[Asia]]) and 2,500&nbsp;km (from 57 to 35°N) north to south. Its [[drainage basin]] covered more than three million km<sup>3</sup>.{{cn|date=January 2016}}

The Eurasian cascade system of seas and lakes is unparalleled in water area. The largest intra-continental lake system of today (the [[Great Lakes]] of [[North America]]) is six times smaller (245,000&nbsp;km<sup>2</sup>), with a water volume 30 times smaller (22,700&nbsp;km<sup>3</sup>), a discharge four times smaller (14,000&nbsp;m<sup>3</sup>/s) and a drainage basin three times smaller.{{cn|date=January 2016}}

The peak inundation apparently centered on the Khvalynean basin (the recent [[Caspian Sea]]). Its level rose and its area increased six times, to one million square kilometers. Its water volume doubled (to 130,000&nbsp;km<sup>3</sup>), with a [[salinity]] of 10-12[[Per mille|‰]]. Its waters overflowed the Caspian depression down the Manych-Kerch spillway.<ref>{{Citation|url=http://paleogeo.org/manych_en.html|title=Paleohydrological Reconstruction of Manych-Kerch Spillway|accessdate=27 January 2016|archiveurl=https://web.archive.org/web/20110405202240/http://paleogeo.org/manych_en.html|archivedate=5 April 2011}}</ref><ref>Chepalyga A.L., Pirogov A.N. Extreme sedimentation in the Manych valley during Khvalynean transgression. Proceedings of the tenth international symposium on river sedimentation. August 1–4,. 2007. MSU. Moscow</ref><ref>Pirogov A.N. Paleogeographic reconstruction of the Manych-Kerch spillway. In: Geology and geochemistry. MPSU. Moscow. 2004. pp. 34-35</ref>

===Sources of water===
Additional water sources would have been necessary for the EEI. To fill the Caspian basin to a level of more than {{convert|50|m}} would require as much as 70,000&nbsp;km<sup>3</sup> of water, equivalent to 200 years of river discharge into the Caspian Sea. Water flowed through the Manych Spillway (250 to 1,000&nbsp;km<sup>3</sup> per year) and some (more than 100&nbsp;km<sup>3</sup> per year) was lost through evaporation. Water may have come from:
* Outburst floods in river valleys
* Melting of [[permafrost]]
* Increased runoff due to permafrost
* Greater drainage basin (including Central Asia, now closed)
* Decreased evaporation due to winter ice
Outburst floods have been inferred from studies of macro[[meander]]s in river valleys.<ref>[http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VF0-42D8164-V&_user=10&_coverDate=02%2F28%2F2001&_rdoc=1&_fmt=high&_orig=gateway&_origin=gateway&_sort=d&_docanchor=&view=c&_searchStrId=1747377154&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=47e55d6b3d255d5e3b920ca30a29fe80&searchtype=a Sidorchuk A., Borisova O., Panin A. (2001) Fluvial response to the Late Valdai/Holocene environmental change on the East European Plain. Global and Planetary Change, 28: 303–318]</ref><ref>Sidorchuk A., Panin A., Borisova O., Kovalyukh N. (2001b). Lateglacial and Holocene palaeohydrology of the lower Vychegda river, western Russia. In: River basin sediment systems: Archives of environmental change. D.Maddy, M.G.Macklin & J.C.Woodward, eds. A.A.Balkema Publishers. Pp. 265–295</ref> Macromeanders dated to the EEI exceed modern ones in size. Their width tends to increase from north to south; they are similar to modern meanders on the [[tundra]], two to three times wider at the [[Tree line#Arctic|tree line]], three to five times wider in the [[taiga]], five to eight times wider in the [[Forest#Temperate needleleaf|mixed-forest zone]], 10 times wider in the [[Forest#Temperate broadleaf and mixed|broadleaf zone]] and 13 times in the [[forest steppe]] and the [[steppe]].<ref>Sidorchuk A., Panin A., Borisova O. 2003. The Lateglacial and Holocene palaeohydrology of Northern Eurasia. In: Palaeohydrology: Understanding Global Change. K.J.Gegory and G. Benito, eds. John Wiley & Sons, Ltd. pp. 61-75</ref>

==Catastrophe==
{{unreferenced section|date=January 2016}}
The rate of water-level rise during the EEI may be inferred from the duration of the epoch, estimated at five to six hundred years. Assuming an equal length of the phases of rising, high water and subsiding (150 to 200 years each), the sea level would rise by {{convert|180|–|190|m}} at a rate of at least one meter per year.

The Caspian Sea has risen {{convert|2.5|m}} since 1978, as much as {{convert|10|cm}} per year, with an adverse impact on human activity. The Khvalynean transgression was more catastrophic, especially the rate of coastline shift in the plains of the North Caspian region. The coastline moved from the Atelian coast (near the [[Mangystau Region|Mangyshlak sill]]) {{convert|1000|km}} north, {{convert|5|to|10|km}} a year. Even greater was the northward migration of the mouth of the [[Volga River]], which moved more than {{convert|2000|km}} upstream in 150 to 200 years—more than {{convert|10|km}} annually, or about {{convert|30|m}} per day.

=={{anchor|Great Flood|Influence on the early man}}Influence on humans==
[[Floodplain]]s and natural spillways influenced human migration. P. M. Dolukhanov of the School of Historical Studies at [[Newcastle University]] has concluded that the Caspian-Black Sea spillway across the Kumo-Manych valley isolated the Caucasus and Central Asia. The spread of [[Upper Paleolithic]] technology in the region became possible only after the crest of the Upper Khvalynian transgression from 12,500 to 12,000 BP.<ref>[http://www.benthamscience.com/open/togeogj/articles/V002/1TOGEOGJ.pdf P.M. Dolukhanov at all. Late Quaternary Caspian: Sea-Levels, Environments and Human Settlement. The open geography journal. 2. 2009. pp.1-15]</ref><ref>Arslanov KA, Dolukhanov PM, Gei NA. Climate, Black Sea levels and human settlements in Caucasus Littoral 50,000 - 9,000 BP. Quaternary International 2007; 167-168: 121-7.</ref>
At Kamennaya Balka,<ref>Leonova N. The Caucasus and Russian Plain in the Late Pleistocene (cultural contacts and migrations) // Annual meeting Society American Archaeologists, Seattle, 2002.</ref><ref>[http://www.lomonosov-fund.ru/enc/ru/library:0134940 Leonova N.B, Minkov E.V.  Spatial Analysis of Faunal Remains from Kamennaya Balka II.]</ref> an Upper Paleolithic site in [[Russia]], of three layers the lower and upper ones contain small stone tools of [[Near East]]ern origin.<ref>[http://www.geoenv.ru/izdat/books/book21-eng.htm N.B. Leonova, S.A. Nesmeyanov, E.A. Vinogradova, O.A. Voeikova, M.D. Gvozdover, E. V. Min'kov, E.A. Spiridonova, S.A. Sycheva. The Paleoecology Of The Plains Paleolithic (The Kamennaja Balka Upper Paleolithic Sites North Of Sea Of Azov).Institute of Environment Geoscience RAS. Moscow. 2006.]</ref> This indicates cultural connections in the southern regions (the [[Caucasus]] and [[Iraq]]). The middle layer indicates an indigenous Kamennaya Balka culture, without small stone tools. Its age (17,000 to 15,000 BP) coincides with Manych-Kerch spillway activity, which may have been a barrier to cultural connections with the Near East.<ref>[http://www.avalon-institute.org/IGCP/doc/AbstractIGCPIstambul.pdf A.L. Chepalyga, T.A. Sadchikova, A.N. Pirogov. Influence of the Late Glacial Eurasian Water Flow on the Black Sea-Mediterranear Corridor (BSMS). In: UNESCO-IGCP-IUGC 1st Plenary meeting and field trip of project IGCP – 521 Black Sea-Mediterranean corridor during the last 30 ky: sea level change and human adaptation (2005-2009), 8-15 October 2005, Istanbul.]</ref> 
The EEI affected human activity; there is no archaeological evidence that it destroyed civilizations, although A. L. Chepalyga suggests that it may have been the basis for [[flood myth]]s.<ref>[http://www.springerlink.com/content/q02720/#section=335929&page=20&locus=17 Chepalyga A.L. The late glacial Great Flood in the Ponto-Caspian basin. In: The Black Sea Flood question: changes in coastline, climate and human settlement. Springer. 2006. pp.119-148]</ref><ref>Chepalyga A.L. Vsemirnyj potop kak real'noe paleogidrologicheskoe sobytie. (Всемирный потоп как реальное палеогидрологическое событие) Jekstremal'nye gidrologicheskie situacii (Экстремальные гидрологические ситуации). Moscow, Media-PRESS, 2010. Pp. 180-214</ref><ref>http://paleogeo.org/flood_en.html</ref><ref>[http://gsa.confex.com/gsa/2003AM/finalprogram/abstract_63243.htm Late glacial great flood in the Black Sea and Caspian Sea (abstract)  2003-11-04. Conference: The Geological Society of America 2003 Seattle Annual Meeting, Seattle, Washington, Abstracts with Programs, v.35-6, p.460]</ref>

== See also ==
*[[Black Sea deluge hypothesis]]
*[[West Siberian Glacial Lake]]

== References ==
{{Reflist}}

== External links ==
* [http://paleogeo.org/epoch_en.html Epoch of Extremal Inundations]

{{DEFAULTSORT:Epoch Of Extremal Inundations}}
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