Investigations / Great Flood

THE LATE GLACIAL GREAT FLOOD IN THE PONTO-CASPIAN BASIN


The work has been aimed at the search for events which are not unlike in dimensions and age to the Noah’s Deluge retained in human memory. Long-term field investigations and laboratory works in the Black Sea — Caspian region and its drainage basin within Eastern Europe provided a factual basis for the work.

At the first stage, we searched for extreme hydro-climatic events through the last 18-20 thousand years, first of all, for most striking ones, such as marine transgressions in the Pontian and Caspian basins; our attention was focussed on possible sources of water for those events, such as overfloods in river valleys and relict permafrost thawing on watersheds.

The second stage included chronocorrelation of the events using stratigraphic and geomorphologic facts, and available radiocarbon dates. That was followed by paleohydrological reconstructions of the basins, including their level, areas, water mass volumes and water exchange between the basins. Particular emphasis has been placed on calculations of the Flood dynamics: rates of water level rise, coastal lowland flooding and coastline shifts, as well as related hydrographic changes at that time which resulted in people migrations from flooded territories or, vice versa, in barriers preventing interaction between archeological cultures.

Finally, on the basis of archeological data, an influence of those events on the ancient human life has been studied, and on the old civilizations in particular. The final aim of the investigation was to develop a comprehensive concept of the Flood and to link it with the events engraved in human memory. Under "Flood" we understand the epoch of the Late Glacial inundation within the Ponto-Caspian basin at ~17 to 10 ka BP (with the maximum at 17-14 ka BP).

Ponto-Caspian basin (reconstructed by Chepalyga, Pirogov 2005)

Material, method and area description.

In case the Flood was a real fact of the history, then besides tales and myths, it had to leave certain traces in bottom sediments of the sea, in fossils, landforms, old coastlines, etc. Our investigations revealed traces of a great flooding in the Ponto-Caspian region and its drainage basin at the time of the last (Valdai) ice sheet melting, about 17 to 10 ka BP.

That flooding imposed its imprint on various landscapes: on coastal plains, river valleys, interfluvial surfaces and even on slopes.

Landscapes of EEI

Flood geology

Bottom and littoral sediments of the basins, together with fossils they contain, may be considered as geological evidence of the Flood. Detailed analysis of their lithology, mineralogy and geochemistry, as well as isotopic composition of the sediments and fossils, make possible the reconstruction of sedimentation environments, composition of flood water, and sequence of events related to the Flood.

Flood sediments.

In the epicenter of the Flood, that is within the Caspian basin, bottom sediments attributable to this event are dated to the Khvalynean basin (or to the Early Khvalynean, if we mean the maximum phase of the Flood). They differ from under- and overlying layers in many characteristics (Badyukova, 2000; Chistyakova, 2001; Leonov et al., 2002). Typically, they are so called "chocolate clays" (because of their specific reddish brown color). Locally the clays are interlayered with greenish-gray and dark gray clays, thinly laminated (1—2 cm). Chocolate clays may also interlayer with and pass laterally into silts, sandy loams, occasionally into sands distinct for high proportion of clayey matter and the presence of marine mollusks of the Caspian type. Thickness of the chocolate clays and related Khvalynean sediments does not usually exceed a few meters (3—5 m), occasionally reaching 20—25 m and more. They are mostly confined to the Caspian Lowland, from the modern Caspian coast to the feet of bordering elevations (Ergeni, Obshchiy Syrt, Privolzhskaya, Stavropol); they are also found in the Volga and Ural estuaries.

Chocolate clays. Enotaevka section (Volga river) Chocolate clays. San-Manych section (Manych valley)

Area of the Khvalynean sediments exposed on the surface amounts to 0.5 million km², while their total area is 1 million km². Dominant in the clastic sediments are poorly rounded quartz grains, with less common micas, carbonate clasts, glauconite, feldspars, coal, and occasional epidote, hornblende, zoisite, tourmaline, zircon. Authigenic minerals, such as iron hydroxide (up to 65%), gypsum (single crystals and aggregates), occasional glauconite, are less frequent (Chistyakova, 2001). Clay minerals are represented by smectite, kaolinite, montmorillonite, chlorite, and hydromica. In the sections on the Lower Volga (Middle Akhtuba), chlorite is typical of the lowermost Khvalynean sediments and almost disappears upwards (Chistyakova, 2001); that may indicate changes in sources of clay material. Characteristic reddish-brown color of the "chocolate clays" cannot be attributed to free iron oxides, it is most probably related to iron-containing clay minerals. Low content of carbonates in the clays or their complete absence suggest a cold climate, as solubility of carbonates increases at low temperatures, so that they may stay in the solution. On the other hand, abundance of chemogenic dispersed carbonates with no secondary changes recorded in the terrigenous pelitomorphic clays suggests under conditions of arid climate.

The beginning and peak of the transgression correspond to arid environments marked by increased evaporation. Judging from the sediment geochemistry and composition of authigenic minerals, the Khvalynean transgression is more likely to develop in a rather arid climate, than in wetter one. That conflicts with the existing climatic hypothesis of the Khvalynean transgression, attributing the latter to wetter climate. Recently, the Khvalynyan sediments (and the chocolate clays in particular) are considered as "cryo-suspensites" resulting from rapid melting of permafrost and activation of solifluction processes at warmer phases during the Valdai deglaciation (Chystyakova and Lavrushin, 2004).

Stratigraphy.

In the marine sequence of the Caspian basin the Khvalynean layers occur above the Late Khazarian ones (dated to the last interglacial) and below the New Caspian (Holocene) deposits. They are separated from the Lower Khazarian series by continental Atelian layers synchronous to marine sediments of the Atelian regressive basin. The level of the latter was 110—120 m below the present-day Caspian level, that is -140 to -150 m. (Lokhin and Maev, 1990; Maev, 1994; Maev and Chepalyga, 2002). On the Caspian Lowland the Khvalynean sediments occur mostly close to the surface. Younger (and higher in the sequence) are only the Holocene floodplain lacustrine and marine (New Caspian) sediments.

The Khvalynean sediments are divided into three parts: Lower, Middle and Upper Khvalynean. The Lower Khvalynean occur at the base of the marine series on the Atelian loams and are overlain by Elton continental sediments. On the Caspian Lowland they are exposed at the surface in the range of +48 to +25 m.

Stratigraphy

Middle Khvalynean sediments are confined between regressive series of the Eltonian and Enotaevka regressions and outcrop between isohypses 25 and 0 m in the Caspian Lowland. Finally, the Upper Khvalynean crowns the marine sequence and outcrops below the zero isohypse, though above the New Caspian transgression limit (-22 to -25 m).

In the Manych depression, reddish-brown clays and silts of the Abeskun layers (Popov, 1983) may be considered as an analog of the chocolate clays. They are exposed at the day surface and contain fossil mollusks of the Khvalynean basin including Didacna, Monodacna, Adacna, Hypanis, Dreissena, Micromelania. The sediments compose constructional landforms (ridges) in the Manych-Kerch Spillway and may be correlated only to the early Khvalynean sediments and to the main flood event 17—14 ka BP. The absence of younger deposits with Caspian fauna suggests the spill flow from the Caspian Sea stopped already.

The flood deposits in the Black Sea basin occur within the New Euxinian series. On the continental slope and within the deep-sea basin they are light reddish-brown and pale yellow mud about 0.5—1.0 m thick (Ryan et al., 2003). In color they are not unlike the chocolate clays of the Caspian basin, their age is also close to the latter (15 ka). They had been identified (by the A. Chepalyga, together with W. Ryan) in the core 1 (section 3) of the DSDP hole 380 (drilled north of the Bosphorus Strait) within 384—450 cm depth interval.

Flood fossils

The main indicators of the marine Flood are specific brackish-water mollusk species close to modern North Caspian ones. Among those, there are Caspian endemic species belonging to Limnocardiidae family, such as Didacna Eichwald genus (Nevesskaya, 1965). The latter is not found at present anywhere outside the Caspian Sea, while it occurred widely in the Azov—Black Sea basin during the Pleistocene, up to the Karangatian time. The genus is represented by Didacna praetrigonoides (dominant), D. parallela, D. delenda, D. subcatillus, D. ebersini, D. pallasi, as well as relatively deep-water (>25 m) D. protracta. Other endemic limnocardiides characteristic of the region are Monodacna caspia, M. laeviscula, Adacna vitrea, Hypanis plicata. Of Early Khvalynean elements, mollusks of Pontodreissena subgenus are most common outside the Caspian Sea (Pontodreissena rostriformis and Dreissena polymorpha in semi-freshwater basins).

Mollusks

Gastropods are usually represented by Caspian endemic genera Caspia and Micromelania. Shells of the Early Khvalynean complex are distinct for small size (2—3 times smaller than those of today) and thin walls. The complex is usually considered as a product of cold climate and low salinity. It is known, however, that a cold climate fosters development of larger individuals. As for salinity, it is unlikely to be much lower than in the North Caspian at present (10 and more), as is indicated by rich species composition. It seems more likely that the mentioned feature results from a considerable turbidity of water and lack of oxygen at the bottom of the basin. The higher turbidity, in turn, could be a consequence of intensified solifluction on slopes under conditions of permafrost decay.

New Euxinian sediments contain mollusk fauna of the Caspian type. Dominant are Dreissena rostriformis, more rare — D. polymorpha, limnocardiides Monodacna caspia, M. colorata, Adacna, Hypanis, and gastropods Caspia and Micromelania. Didacna genus is entirely absent from the Black Sea, though they are traced along the Manych valley as far as the Western Manych river mouth (Manych-Balabinka village). That may indicate a lower salinity in the New Euxinian basin (5 to 6 ‰ ). Fauna of the Caspian type, close to the described above in composition, was found in the Bosphorus bottom sediments in hole 14 at depths of 800 to 100 m, and dated to 26—10 ka BP (Algan et al., 2001). It is dominated by Caspian mollusc Pontodreissena rostriformis.

The Khvalynean and New Euxinian marine sediments contain also microfossils, such as foraminifers, ostracodes and diatom algae.

Flood geomorphology

The Flood water left distinct traces in the morphology of landforms, such as marine terraces, specific coastlines, flattened surface of sea floor, as well as sculptured and constructional landforms within the former spillways (of excess water) — the Manych-Kerch spillway, the Bosphorus and the Dardanelles.

Spillways.

The Manych-Kerch Spillway is a large trough deeply eroded into solid rocks which connected the Caspian and Black seas. It was inherited from an older strait between the two seas, which existed (with interruptions) since the late Pliocene (the Akchagylian basin) (Popov, 1983). It follows a tectonic depression skirting southern periphery of the Karpinsky Swell (an elevated Mesozoic structure confined between the Donbass and Mangyshlak).

Manych-Kerch Spillway

The total length of the spillway amounted to 950—1000 km (depending on the sea level), with maximum width of 50-55 km and minimum width of 10 km. Its depth reached 30—50 m. The spillway bottom gradient was 0.0001 m, and drop in water level from the Caspian Sea (+50 m) to the Black Sea (-80 to -100 m ) was up to 150 m at the beginning of the excess water flow to 100 m at its termination.

The spillway began at the Khvalynean coastline from the head of the Chograi Bay between the Ergeni and Stavropol uplands. The bay is 60 km long and 30 km wide at its entrance, its depth reaches 40 to 50 m. The most narrow section of the spillway about 10 km long was near the Zunda-Tolga village, where the water flowed over a sill at a 20 m above sea level. When the Khvalynean transgression was at its maximum (50 m a.s.l.), the spillway depth was up to 30 m, (on the average, 20—25 m). The spillway bed is covered with silt and clay 5 to 10 m thick. The cited data enable us to estimate the flow velocity at ~0.2 m/s and maximum discharge through the Manych S pillway at 40 to 50 thousand m³/s, with total runoff of more than 1000 km³ per year. That is 6 times greater than the Volga River runoff and 3 times that of the Mississippi R. (It should be kept in mind that in the calculations the sill depth was assumed to be constant at 20 m a.s.l.). At the stream depth as great as 30 m the flow velocity must have been much greater; however, it does not agree with fine composition of the sediments. The contradiction may be explained by assuming a higher initial level of the sill — about 40 m a.s.l. or even higher. At that case, the flow discharge would be several times reduced and be close to the modern Volga discharge ( 8-10 000 m³/c).

A short distance downstream, at the Kalaus R. mouth, a plug was formed by merged fans of the Kalaus and Zapadny Manych rivers (Badyukova, 2001). It blocked the spillway and formed a divide between the Caspian and Black seas at 25 m a.s.l. Further westwards, there is the widest part of the spillway (up to 50—55 km wide and 180 km long), now occupied by the Manych-Gudilo Lake. The channel was braided, as is indicated by alluvial landforms. Among the latter, there are several (up to 5—7) parallel ridges 10 to 15 km long, 20—30 m high; their width ranges from a few hundsreds of meters to 1—2 km. The ridges are composed of clays and silts, less frequently of sands with Khvalynean marine fauna (analogous to that recovered from the chocolate clays). At present the interridge hollows are occupied by water bodies. Near the Salsky Swell the spillway narrowed to 15—20 km at the tectonic uplift, and the stream flowed within a single stream, without braiding. At the Manych River mouth, the spillway occupied the whole valley of the Don R., its surface level lowered to +0 m, and the bed was at -15 to -20 m. Within the limits of the modern Azov Sea, the spillway occupied an overdeepened valley, with the bed at -40 to -50 m and 10—20 km wide.

In the Kerch Strait the stream narrowed to 6—8 km and again enlarged on the Black Sea shelf, forming delta within depth interval of -80…-100 m to -40—…-50 m.

Coastlines.

The coastline of the early Khvalynean basin was fundamentally different from that of the present days. That may be attributed to the fact that at the high sea level it went directly to the slopes of surrounding uplands (Ergeni, Obshchiy Syrt, Privolzhskaya). Instead of depositional coasts with shallow and flat-bottomed bays of intricate shape typical of the Caspian Lowland (so called Caspian type (Leontyev et al., 1977) and large deltas of the Volga and Ural rivers, there appeared abrasion-embayed coasts, with deep embayment of liman type, where the sea ingressed into valleys dissecting uplands.

As an example, we refer to a bay in the Yashkul valley penetrating the Ergeni Upland for 50 km and filled with chocolate clays with marine khvalynian fauna.

The coastline of the Early Khvalynean basin

The most spectacular coastline feature dated to the Flood time is the Volga estuary filled with chocolate clays upstreams to the Zhiguli Ridge, and even farther. The estuary was about 800 km long, 50—80 km wide (locally narrowing to a few kilometres) and up to 20—30 m deep, and the backwater reached up to Cheboksary in the Kama valley.

Volga estuary

Other estuaries (of the Ural, Terek, Emba rivers) were smaller in size, but still differed markedly from modern river mouths which are mostly of deltaic type.

Marine terraces indicate sea level and coastline position at every individual oscillation during regression of the Khvalynean Sea. Because the Flood basin level was unusually high, its sediments mantle much older terraces; in tectonically stable regions (Dagestan) they form as many as 9 marine terraces at altitudes of 48 m, 35 m, 22 m, 16 m, 6 m, -5 m, 0 m, -6 m, -16 m (Leontyev et al., 1977; Rychagov, 1997). Those terraces show episodes of temporary stability of the sea level during the general reduction of the basin. Those episodes were separated by regressive phases with sea level dropping by tens of meters. The most considerable regressions (within the Khvalynean stage) were Eltonian (to —50 m) and Enotaevka (to —100 m). The presence of the terrace flight suggests a series of the Khvalynean basin fluctuations at its late (regressive) phase. Their levels are marked by submarine fans at the Mangyshlak sill (Lokhin and Maev, 1990; Maev, 1994).

Chronology of the Flood

It is not easy to date the Flood and to determine its duration and characteristics. Recently, however, new materials have been obtained, including radiocarbon and other dates, which permit to define the age of the Flood and even to reconstruct its dynamics (Svitoch et al., 2000; Leonov et al., 2002). Historical age of the Flood, as defined by various authors, varies from 4.5 to more than 10 ka. In Mesopotamia it is dated to 4500—6000 years BP (Rohl, 2003); this flood, however was not "the Noah’s Flood", its looks more like a local, though extensive, inundation. As for the Noah’s Deluge, numerous recent researches place it at 12th to 9th millennia BC (Balandin, 2003), that is more than 13 to 12 ka BP. Therefore, the Flood falls on the Late Glacial time, and not on the very end of the latter. The Flood duration also varies from a fortnight to a few months. Theological sources even give a precise date of the Flood — 9545 years BC (Leonov et al., 2002), that is 11949 years ago.

Dates close to the above have been obtained for flood deposits in the Caspian (Khvalynean) basin, New Euxinian sediments of the Black Sea, and fluvial deposits filling macro-meanders in river valleys. The Khvalynean transgression of the Caspian is the most extensively studied (Rychagov, 1997; Maev, Chepalyga, 2002; Leonov et al., 2002; Varushchenko et al., 1987). More than 50 14C dates have been obtained, part of them (except for extreme ones, admittedly false) are shown in table:

Lab N C14
MGU - 1039 10770±330
MGU - 1037 11280±700
LU - 841 11490±380
MGU-IOAN -38 12150±200
MGU - 19 12600±240
LU — 490 A 12520±140
LG - 93 14080±100
MGU - 18 15600±300
MGU - 97 16000±330

The bulk of the dates is clustered in the range of 17 to 9 ka BP, the flood duration is estimated at 5—6 ka. The Early Khvalynean sediments are dated to 17—14 ka BP, the Late Khvalynean — 9 to 11 ka BP, and middle Khvalynean layers are placed between, at 11 to 13 ka BP. Of them, only beginning of the Early Khvalynean time may be considered belonging to properly "Flood" epoch. During this interval, the Caspian level rose by 180—190 m (Maev, 1994). To determine the time of the Flood and its position among other "Flood-like" events, it should be considered as a part o the whole sequence of events. The system of the Khvalynean terraces of the Caspian Sea may be used as a chronological scale. The terraces indicate high stands of the Caspian water against the background of its intermittent lowering. There are as many as 8 Caspian terraces, with one relatively lower level (Yashkulian transgression, 35 to 40 m) preceding the highest stand at 50 m. During the Khvalynean time (estimated at 5—6 thousand years) about 10 cycles of level fluctuations occurred, at a period of 500—600 years. They can be grouped in 3 series 2 thousand years long each, as follows: Early Khvalynean levels (40, 50 and 35 m); Middle Khvalynean levels (22, 16, 5 m); and Late Khvalynean ones (-6, 0, -6, -18 m). They are separated by two regressive phases, namely Eltonian and Enotaevka regressions.

Khvalynean terraces of the Caspian Sea

Fluctuations of the Khvalynean basin level, the coastline migrations by hundreds and thousands of kilometers, as well as large-scale flooding and drying of sea bottom, may be considered as waves of the Flood, extended for 5—6 thousand years.

The first wave, the Early Khvalynean one, began 15.5 ka BP and lasted about 2 ka; it was complicated by three superimposed oscillations, with the sea level rising to 40 m, 50 m, and 35 m. The sill in the Manych Spillway is at about 20 m a.s.l., so all the three basins overflowed into the Black Sea (through the Manych-Kerch Spillway. It is this first wave, and its rising phase in particular, that may be considered as the Flood in the Ponto-Caspian region.

The second wave, the middle Khvalynean one, did not exceed 22, 16 and 6 m even at the peaks of oscillations; the Caspian water did not flow into the Black Sea, and the spillway, in all probability, did not function.

The third wave of the flood, the late Khvalynean, did not surpass the modern ocean level (0 m), all its oscillations (-5 m, 0 m, -5, and —12 m) were below it, though above Caspian level during the Holocene. When considering the Caspian level fluctuations, a distinct trend may be traced within two periods. The first period (16 to 9 ka BP) is marked by a progressive lowering of the sea level at peaks of oscillations (from +50 m to —12 m, that is 62 m during 6 ky. This period marks the time of the Great Flood. The second period is that of relative stability during the Holocene, with 6 m difference in peak height (—20 and —26 m) over 10 thousand years. Therefore, the Flood phase itself (that is, an active rise of sea level) occurred somewhere between 16 and 15 ka BP.

The Caspian level rose by 180—190 m over 100—150 years. The last value is inferred from a cycle duration (500—600 years) assuming that the sea level rise, the high stand and subsequent lowering laster for approximately the same time each. As for the rising level, it could take even less time, because it could result from a sudden warming during the glacial Heinrich event N 1 (14.3—15 ka BP).

That event was of global character, and the warming was accompanied by arctic glaciers surging (Groswald, 1999), high rate of glaciers decay and eustatic rise of the ocean level.

The Flood hydrology: marine basins

The most sizeable events comparable with the ancient floods recorded in myths and legends occurred in the inner seas and lakes of Eurasia known as Ponto-Caspian.

The Khvalynean sea basin appeared to be epicenter of the Flood and the most sensitive indicator of the related events (sea level rise, coastline shift and coastal lowland flooding). This basin concentrated the bulk of the Flood water, altered the water composition and marine environment, while excess water escaped into the Black Sea.

Khvalynean sea

In the process of the Flood , the Khvalynean Sea expanded over an area of about one million km², up to 1.1 km² together with the Aral-Sarykamysh basin, that is three times the area of the present Caspian Sea. The volume of water accumulated was twice that of today’s (130,000 km³). As far as the Flood is concerned, the water reached up to 48—50 m a.s.l. The type of the basin itself changed: an isolated closed lake of the Atelian basin was transformed into a gigantic through-flow lake-sea, with one-way discharge into an adjacent basin. In spite of the basin being repeatedly washed with fresh water, changes in the chemical composition and water mineralization were not very significant (within 10 to 12‰). That is indicated by the lack of essential changes in the mollusk fauna and composition of other groups. It seems probable that the through-flow basin was short-lived. Yet the Khvalynian water was colder than that of the Caspian Sea (4°C in the north and 14&grd;C in the south); as indicated by a low 18O (10‰). It may be also suggested that the Khvalynian water was turbid; that had an effect on sediment composition and resulted in a smaller size of mollusk shells. The high turbidity could be due to heavy impact of solifluction and increased solid runoff from the drainage basin (Leonov et al., 2002).

New Euxinian Sea. At the time of the Flood, the Black Sea depression was occupied by the New Euxinian lake-sea, with a very low level at early stages (not higher than 80 to 100 m below sea level). Due to floodwater discharge from the Caspian basin, the lever rose rapidly to -50…-40 m, with corresponding increase in area from 350,000 to 400,000 km². The flooded shelf area did not exceed 20—30,000 km². Water volume at that time was as much as 545,000 km³, that is a little less than the Black Sea of today, but the origin of the water was quite different Paleontological data on mollusks and foraminifers suggest it to be Khvalynean fauna, though without Didacna, which indicates a lower salinity (6 to 8‰). That type of through-flow basin with slightly mineralized water is known under the name of semifreshwater (Chepalyga, 1984, 2002a,b). Oxygen isotope composition (-10 to -11‰) suggests a low temperature of water (Nikolaev, 1995). Lithological characteristics of the sediments (reddish-brown and pale yellow clays) indicate a high degree of oxygen saturation (which probably resulted from mixing by turbidity currents).

Propontida basin. A semifreshwater basin of the Caspian type existed in the Marmara Sea basin at that time. It received excess water from the New Euxinian basin, together with mollusk fauna of Dreisssena rostriformis, Dr. polymorpha. Its salinity did not exceed 6 to 8‰, and the water flowed from it through the Dardanelles into the Mediterranean.

Cascade of Eurasian basins. The Great Flood resulted in appearance of a system of interrelated basins in inner Eurasia. They have been studied using various tracers, including lithology (reddish-brown interlayers of the chocolate clay type), paleontology (Caspian endemic mollusks, foraminifers, ostracodes) and isotopes (of oxygen and other elements). Those the enabled to trace the system from the Caspian to Marmara Sea and to reconstruct a Cascade of Eurasian basins beginning from the Aral-Sarykamysh basin, Uzboi, the Khvalynian Sea, Manych-Kerch spillway, New Euxinian Sea, the Bosphorus, the ancient Sea of Marmara, and further, through the Dardanelles into the Mediterranean Sea.

Cascade of Eurasian basins

Parameters of this superbasin were as follows: area — about 1.5 million km²; water volume — up to 700 thousand km³; salt resource —5000 km³, or 10 billion tons; water discharge — more than 60 thousand m³ per second; extension of the system from west to east — 3000 km (from the Mediterranean to Central Asia), extension of the system from north to south — 2500 km (from 57 to 35°N); drainage basin area — more than 3 million km³.

The Eurasian cascade system of seas and lakes is unparalleled in water area. The largest intracontinental lake system of today — the Great Lakes of North America — ranks below it in all the parameters: its area is 6 times smaller (245,000 km²), water volume — 30 times smaller (22,700 km³), discharge — more than 4 times less (14 thousand m³/s), and drainage basin area — about 3 times less.

The Eurasian Cascade would impress the early man and could be reflected in old epic poems and mythology. In particular, a similar basin was described in "Avesta" (the Zoroastrian Holy Scriptures) under the name of Vorukashah Sea.

Sources of water for Flood

To provide water for the Flood events, there must have been some additional sources. To fill the Caspian basin to a level of +50 m, it would take as much as 70,000 km³ of water, that is equal to 200 year river discharge to the Caspian. Besides, some water flowed through the Manych Spillway 250 to 1000 km³ per year, and some was lost through evaporation from the water surface (>100 km³ per year). The water for all the processes could be supplied from various sources, namely:

  • superfloods in river valleys;
  • permafrost melting;
  • higher runoff coefficient under conditions of permafrost;
  • increased catchment area (including Central Asia area, closed at present);
  • lower evaporation from the water surface (due to ice cover in winter).

    The superflood phenomenon has been first inferred from studies of macromeanders in river valleys (Sidorchuk et al., 2003). The macromeanders dated to the Flood epoch exceeded considerably the modern ones in dimensions; their width tends to increase from north to south: they are similar to the modern meanders in tundra zone, 2 or 3 times greater in forest-tundra, 3 to 5 times in taiga, 5 to 8 times in mixed forests zone, 10 times in broadleaf zone, and 13 times in the forest-steppe and steppe (Sidorchuk et al., 2003). No superflood effect has been noted within the recent permafrost area. Accordingly, annual runoff values calculated from the macromeander dimensions is also above the modern runoff (twice the modern value for the Volga R., thrice for the Kama R., and almost 4 times for the Don R.

    Archeology of the Flood

    The Flood could exert a considerable effect on the human life through the rise of sea level and flooding of vast areas, including fertile lands, river deltas and floodplains. That could stimulate a mass exodus from the flooded areas, ethnos migration, and appearance of new ethnic communities. Within river valleys settlements tend to move upslope. Thus, in the Seim R. valley the pre-Flood Late Paleolithic site Avdeevo dated to 20–18 ka BP was at the very edge of water, while younger sites are located much higher, which may be attributed to superfloods (Leonova, 2002).

    On the other hand, sea basins of the Vorukasha system formed water barriers several thousands of kilometers long and a few hundreds of kilometers wide, which hampered contacts between peoples and exchanges between archeological cultures. Even relatively narrow Manych-Kerch spillway prevented the cultural exchange. That had an effect on development of Paleolithic cultures presented in three cultural layers of the Kamennaya Balka site on the northern coast of the spillway (Leonova, 2002). The upper and the lower layers dated to 20–17 and 13–12 ka BP respectively contain typical implements of the Caucasian (Imeretian culture) and near Eastern (Shanidar) types, with prevalence of microlites. That suggests close connections with southern regions. The middle layer synchronous to the Flood’s peak (17–14 Ka BP) yielded mostly autochthonous tools of local type, without microlites. Such a difference may be attributed to the fact that the site was isolated from the Caucasus by the Manych-Kerch Spillway.

    Manych-Kerch spillway — water barrier

    The dramatic reduction in fertile land area together with highly dynamic environments on the river banks and the Vorukasha Sea coasts could give impetus to development of producing economy and appearance of ancient civilizations. In fact, the oldest boat images dated to 8-9 Ka BP were found in Gobustan, on the Caspian coast, south of the Kura River delta (Dzhafar-zade, 1973). Those are rock paintings showing not only flat-bottomed boats and keel-built vessels suitable for marine navigation, some with as many as 37 oarsmen. The earliest ships appeared in the Caspian region immediately after the Flood, which may be interpreted as a result of this event. Another evidence for productive economy appearance as a result of the Flood is that horse was domesticated there earlier than anywhere else in the World (Matyushin, 1976).

    Rock paintings in Gobustan

    Was the Flood a catastrophe?

    That may be estimated from its scale, rate of the flooding, and impact on the man. The rate of water level rise may be inferred from duration of the whole cycle estimated at 500–600 years. Assuming an equal duration of the phases of rising, high stand and lowering to be of (about 150–200 years each), the sea level would rise by 180–190 m at a rate of at least 1 m per year. That is 1000 times faster than modern rise of the ocean (about 1 mm per year).

    As for the recent rise of the Caspian Sea, it amounted to 2,5 m since 1978, the rate thus being as high as 10 cm per year. Yet it had a considerable adverse effect on the human activities. Therefore, the Khvalynean transgression (as the main event of the Flood) was all the more catastrophic, especially when considering the rate of the coastline shifts over the plains of the North Caspian region. The coastline migrated from the Atelian coast (near the Mangyshlak sill) northwards by 1000 km, that is about 5 to 10 km yearly. That would be quite appreciable for the coast dwellers. Even greater was the rate of the northward migration of the Volga River mouth. It shifted upstream by more than 2000 km within 150–200 years, that is at a rate more than 10 km per year (about 30 m per day). Such a rate was not only inconvenient, but presented a certain danger for the people. And there is something else. The coastline not only shifted, but suffered some qualitative changes. First, deltas of large rivers, such as Volga, Ural, Terek, Kura, and others, completely disappeared. With the rise of sea level, the river mouths shifted far upstream, into deep estuaries, where there was no place for deltas; so the deltaic ecosystems were wiped out. It should be hold in mind, that those ecosystems were most fertile and most hospitable for men, so their removal seriously shook the very foundations of the economy. The marine transgression flooded the most fertile lands and reduced considerably the usable land resources. This loss was aggravated by superfloods in river valleys and inundation of interfluves by growing thermokarst lakes.

    The Ponto-Caspian Flood is not the Noah’s Flood as described in the Bible. The relation may be only indirect. The collective memory of the mankind retained the events for thousands of years; later it was written in ancient Aryan scriptures, such as Rigweda and Avesta, and only later the concept of the Flood was adopted by ancient inhabitants of Mesopotamia and came from them to the Bible.

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    Publications

    1. 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
    2. Chepalyga A. Caspian and Black Sea Level Fluctuations as a Basis of High-Resolution Stratigraphy of the Quaternary // INQUA-501 “Caspian-Black Sea-Mediterranean Corridor: Sea level change and human adaptive strategies”. Abstract volume. 27 sept – 5 oct/ 2010. Rhodes, Greece. Pp. 45-46.
    3. Chepalyga A.L., Arslanov H., Yanina T. 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.
    4. Chepalyga A.L., Dolukhanov P.M., Shkatova V.K., Lavrentiev N.V. Late Quaternary Caspian: Sea-Levels, Environments and Human Settlement. The Open Geography Journal, 2009, 2, pp. 1-15.
    5. Chepalyga A.L., P.M. Dolukhanov, Lavrentiev N.V. Late Quaternary environments of the North Caspian Lowland. In: . G.R. Sarson & A.M. Shukurov, editors. The East European Plain on the Eve of Agriculture. British Archaeological Reports, International series, vol. 1964, Oxford, 2009 , pp. 65-70.
    6. Chepalyga A.L. Dynamics of the Khvalynian Transgressions and Early Human Settlement in the Caspian Basin. IGCP 521-481 Plenary Meeting and Field Trip, 2007.
    7. Chepalyga A.L. The Great Flood in the Ponto-Caspian region: theory and influence on the black sea-mediterranean corridor. Annual Meeting (28-31 October 2007). Geological Society of America Abstracts with Programs. 2007.
    8. Chepalyga A.L. Noah’s Flood in Ponto-Caspian region: theory, influence on the Black Sea-Mediterranean Corridor, Noah’s voyage reconstruction. IGCP 521-481 Plenary Meeting and Field Trip, 2007.
    9. A.L. Chepalyga. Extraordinary rate of Khvalun transgressions: huge flooding, sea level oscillations, coastlane migrations, influence to civilizations. In 4 th International Conference or UNESCO programme 481 Dating “ Caspian Sea Level Change, 2006.
    10. A.L. Chepalyga, A.N. Pirogov, T.A. Sadchikova. Manych Valley - the most eastward link of Black Sea - Mediterranean Sea Corridor. In 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
    11. A.L. Chepalyga, A.N. Pirogov, T.A. Sadchikova. Influence of the Late Glacial Eurasian Water Flow (Great Flood) 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, Istambul,
    12. A.L. Chepalyga. Great Flood in the Ponto-Caspian basin. 5th International Symposium on Eastern Mediterranean Geology. Thessaloniki, Greece. 2005.
    13. Chepalyga A.L. (2002a) Paleoenvironmental reconstructions of ancient sea basins. The Black Sea. In: Dynamics of terrestrial landscape components and inner marine basins of Northern Eurasia during the last 130,000 years, A.A.Velichko, ed. Moscow: GEOS. Pp. 170-182.