Popov 2010 Sea Level Fluctuation

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ISSN 08695938, Stratigraphy and Geological Correlation, 2010, Vol. 18, No. 2, pp. 200224. Pleiades Publishing, Ltd., 2010.Original Russian Text S.V. Popov, M.P. Antipov, A.S. Zastrozhnov, E.E. Kurina, T.N. Pinchuk, 2010, published in Stratigrafiya. Geologicheskaya Korrelyatsiya, 2010, Vol. 18,No. 2, pp. 99124.

200

INTRODUCTION

By the terminal Paleogene, Paratethys had com

prised two major marginal seasAlpineCarpathian

and CaucasusKopetDag, each having a deep axial

part and the northern and southern shelves (Shcherba,

1993; Popov et al., 2004). In the OligoceneMiocene,

the flysch basins of the Carpathians and Caucasus

closed and formed the Pannonian and EuxinicCas

pian intracontinental semiclosed or closed basins.The latter was named as Eastern Paratethys. Its south

ern shelf had a complicated and yet unclear paleogeo

graphic history as it was constantly affected by Alpine

tectonic movements and underwent orogenic pro

cesses in large measures. Therefore, the history of sea

level fluctuations is easy to trace by the data of sedi

mentation on the northern and eastern shelves that

occurred on a more stable platform basement.

MATERIALS AND METHOD

Shallowwater and coastal sediments of smallthickness, as well as relatively deepwater facies (up toa depth of 1000 m) that had accumulated in majordepressions, such as the West Kuban and TerekCaspian, covered the vast shelf of the East European Platform, and the Scythian and Turan plates. Sediments ofthe inner shelf were intensely rewashed by coastal currents and cut down in the valleys of large rivers. It is

there that the stages of sealevel fluctuations can bemost clearly observed. During the transgressions, thecoastline of the basins retreated far northward andeastward, and the sea rushed into river valleys andoverlapped continental sediments. Such stages are welldated by sediments ingressed far into the platform.The tracing of coastal facies and coastlines, and theinterpretation of lithological and faunal data, allowedreconstructing in detail the paleogeography of the

basins for nearly each of the regional stages of the Oli

Sealevel Fluctuations on the Northern Shelf

of the Eastern Paratethys in the OligoceneNeogene

S. V. Popova, M. P. Antipovb, A. S. Zastrozhnovc, E. E. Kurinab, and T. N. PinchukdaPaleontological Institute, Russian Academy of Sciences, Profsoyuznaya ul. 123, Moscow, 117997 Russia

email: [email protected] Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017 Russia

cAllRussia Research Institute of Geology, Srednii pr. 74, St. Petersburg, 199026 RussiadKuban State University, Krasnodar, Russia

Received January 26, 2009

AbstractSealevel fluctuations in the terminal Eocene, Oligocene, and Neogene of the Eastern Paratethysare quantitatively assessed on the basis of facies and old coastlines traced on the northern platform shelf, levelsof river valley incisions, and the study of seismic profiles. The first data massif allows the characterization andcorrelation of transgression stages in the history of the Eastern Paratethys. The greatest transgressions fallwithin the first half of the Late Eocene, midEarly Oligocene, initial Late Oligocene, initial Early Miocene,

the initial Tchokrakian, Karaganian and Sarmatian in the Middle Miocene, the middle and late Sarmatianand early Pontian in the Late Miocene, and the Akchagylian in the Caspian basin of the Pliocene. In contrast,the greatest incisions of northern rivers running from the platform allow us to establish the time and extent ofthe main declines in the base levels of the erosion. Maximal incisions date back to the terminal Eoceneinitial Oligocene, terminal Solenovian time in the terminal Rupelian, the terminal Maikop in the EarlyMiocene, the terminal Sarmatian and middle Pontian in the Late Miocene, and the Early Pliocene in theCaspian basin. Large regressions also formed unconformity surfaces, traced on seismic profiles as erosionboundaries of several orders. The surfaces are confined to the Eocene/Oligocene boundary, middle and lateMaikop, Sarmatian/Meotian boundary, middle Pontian, and terminal Mioceneinitial Pliocene, as well asbeing traced even in the most deepwater basins. The synthesis of these data suggests a preliminary version forthe curve of transgressionregression cyclicity. Its correlation with the eustatic curve shows their similarityonly in the lower partprior to the initial Middle Miocene, when Paratethys became a semiclosed basin.

Key words: transgressions, regressions, coastlines, incisions, seismic profiles, eustatics, Scythian and Turanplates, Paleogene, Miocene.

DOI: 10.1134/S0869593810020073


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STRATIGRAPHY AND GEOLOGICAL CORRELATION Vol. 18 No. 2 2010

SEALEVEL FLUCTUATIONS ON THE NORTHERN SHELF 201

gocene and Neogene in the period of the basins maximal fillup (Fig. 1; Popov et al., 2004).

To establish quantitatively the amplitude of sealevel fluctuations, the facies assessment of the paleobasin depth, as well as the absolute heights, at whichsediments of the transgression series occur, are of greatimportance. Although the depth and heights wereundoubtedly changed in some structures by successive

tectonic processes, the relationship of absolute heightsinside the structures remains constant, and averageddata without regard for extreme values allow for comparing the transgression levels of a different age.

The dimensions and the nature of a basin duringregression stages are more difficult to trace. Sedimentsof such stages are confined to depressions and oftencut only by deep boreholes. Therefore, data on suchsediments are fragmentary, and coastlines are impossi

ble to reconstruct. Seismic materials provide important information on regression stages in the evolutionof basins. The time and the range of a decline in the

base level of erosion during regressions can be established by the depth of the incision of large rivers, whichdate the drops of the base level of erosion. However,the complexities of dating the incisions, especially incontinental facies, make the use of this source of information difficult. A.S. Zastrozhnov examined the Neogene history of the paleoDon Rivers lower reachesmore fully.

The main features of sedimentation, relationshipsbetween sediments and underlying and overlyingsequences, incisions in deltaic facies, and the mode ofsediment superposition controlled by sealevel fluctuations are traced in seismic profiles (Kunin et al.,1989, 1990; Gillet et al., 2005; Antipov et al., 2005;Kurina et al., 2007, and others). Profiles compiled on

the basis of drilling and seismic data suggest that allmajor depressions had the structure referred to astopodepressions (Shlezinger, 1998): their deepwaterparts were bordered by clear submarine slopes. Sedimentation on the slopes proceeded by way of lateralaccretion, and sediments made up prograding clinoforms, well traced in the seismic profiles. To interpretthese data, the reflecting horizons should be exactlydated and seismic information should be correlated

with the results of borehole drilling. T.N. Pinchuk carried out such dating along the profile IIII* throughthe West Kuban depression. Interpretation along theprofile was previously carried out by differentresearchers (400 Million , 2005; Afanasenkov et al.,

2007, and others). The seismostratigraphic analysis ofthe available geologicalgeophysical material, which

we have carried out, allowed us to construct a verifiedmodel for the formation of the West Kuban depressionin the Cenozoic. Since the Paleocene, the depressionexhibited an inherited evolution at the site of theJurassicCretaceous sedimentary basin of the marginalsea type.

Based on all these data, we try in this work to assessthe range of sealevel fluctuations on the northern

shelf of Eastern Paratethys in the terminal Paleogeneand in the Neogene.

THE TRACING OF FACIES AND COASTLINES

In the western part of the shelf, the vast BelayaGlina (Kharkov) basin preceding the Oligocene onehad a common shelf with the AlpineCarpathian

basin and in places overlapped the Ukrainian Shieldand interfered far into the Volga and Transcaspianregions since the midLate Eocene (zones NP19initial NP20, beds with Globigerapsis index, the time ofdeposition of Mandrikov beds) (Popov et al., 2004,map 1). Sediments of the basin occur in many placesat a height of up to +150 m (Fig. 2a). A sharp regression and a change in the tectonic pattern of the whole

AlpineCaucasian belt took place in the terminal LateEocene (beds with Bolivina), which was determined bya fast postrift subsidence with a formation of a deepsedimentary basin (400 Million , 2005).

The further presentation of the material was subdi

vided chronologically into a description of transgressionregression cycles of the Maikop (OligoceneEarly Miocene) time, the history of basins of the terminal Early and Middle Miocene (Tarkhanian andTchokrakian) and basins of the terminal MiddleMiocenePliocene.

The Maikop Basin

The northern BlackSea region.Maikop sedimentsoccur on Beloglinian (Kharkov) sediments in thenorthern part with a hiatus, the range of whichincreases towards margins of the BlackSea depres

sion. Deposits of the Rubanov Formation (NP21Zone, beds with Cibicides almensis) are known onlyfrom boreholes and correspond to the initial transgression of the Oligocene, when the sea extended only eastof the EvpatoriaSkadov Fault (Chekunov et al.,1976). The maximum of the Early Oligocene transgression falls within the Nikopol time, when shallow

water facies with rich benthonic fauna reached theCity of Nikopol, where they were stripped by quarriesat an absolute height of +20 m. By the end of thattime, the sea had regressed, and the subsequentMolochan Formation (Ostracoda beds of the Solenovian Horizon) exhibits a transgressive overlapping inplaces, though, it does not reach the boundaries of theNikopol basin. The deposits do not expose on the surface and pinch out at a depth of about 10 m in marginal parts and, probably, are cut off in the course ofthe subsequent regression (data of Veselov in (Chekunov et al., 1976, Fig. 24)). The sediments of the overlying Serogozy Formation reflect conditions of a gradual regression: clay and silt are replaced upward bysand with coastal fauna. The overlying ferruginized

weathering crust and fossil plants suggest the continental regime of sedimentation.


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Fig. 2.Correlation of shorelines of transgression phases in the Eastern Paratethys. (a) (1) Late Eocene, (2) Early Oligocene,(3) Late Oligocene, (4) Early Miocene; (b) (1) early Tchokrakian, (2) early Konkian, (3) middle Sarmatian.

Fig. 1.The paleogeographic map of the Eastern Paratethys in the midLate Miocene (Meotian) (after Ilina et al. in (Popov et al.,2004)).

(1) Conglomerate; (2) sand; (3) clay; (4) limestone; (5) mountains and uplands; (6) lakes; (7) shallow shelf; (8) deep shelf;(9) bathyal; (10) direction of terrigenous material drift; (11) deltas; (12) overthrusts; (13) volcanics; (14) landsea boundary inthe early Meotian; (15) landsea boundary in the early Pontian; (16) volcanoes.


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wellexposed in sections of chinks (border scarps).That is why the distribution of coastal and lagoonalfacies, the replacement of them by continental sediments, and migration in time were reconstructed indetail on a considerable area (results of geological sur

veys of the trust Aerogeologiya, Voznesenskii, 1978).The middle Priabonian transgression and the latestEocene regression were revealed there as well. The sea

basin began retreating from the territory of WesternSiberia and the Turgai depression in the middle of theLate Eocene (Cheganian). The Aral region gotdrained nearly completely by the terminal Eocene,and the sea remained only within the axial part of theNorth Ustyurt depression by the initial Oligocene(Ashcheairykian).

The subsequent vast transgression in the early Ashcheairykian proceeded via Turgai and reached the

West Siberian Lowland (Kurgan beds). Then, a shortterm regression set in during the middle Ashcheairykian and a new transgression, in the secondhalf of the Ashcheairykian (Voznesenskii, 1978,Fig. 28). Deposits became coarser and areas of the sea

basin and coastal plain reduced in the terminal Ashcheairykian.

Regression still persisted in initial Solenovian timefollowed by a new transgression phase, when the seaflooded the coastal plain in the form of large ingression

bays. The grade of particles in terrigenous materialscontinued to increase, which indicated intensificationof denudation and river runoff. Intense accumulationof olitic iron ores of commercial importance was stillin progress in deltaic areas. In the terminal Early Oligocene, regression set in, and rocks of the SolenovianFormation, as well as the Ashcheairykian Formationon the Chagrai Plateau, were eroded. Hence, a decline

in the base level of erosion made up dozens of metersat that time.

In the Late Oligocene (Karatomacian), the searegained its dimensions, clayeysilty deposits bordered by a narrow strip of sandysilty grounds ofshoals predominated. Valley of large rivers, whose deltas gradually encroached upon the northern territories, passed along the axial zone of the Chelkar troughand the eastern slope of the Kulanda Syncline (Voznesenskii, 1978, Fig. 30). The transgression reached itsmaximum in the first half of the Baigubekian time,

when marine sandy sediments with Cerastoderma prigorovskii, Corbula helmersenioccupied vast areas in thenorthern Aral region (Voznesenskii, 1978, Fig. 31),southern Aral region, and Kyzyl Kum territory. Thesea had retreated and sediments had been substitutedfor coastallagoonal deposits with freshwater fauna bythe terminal Baigubekian. A new small transgressionphase took place in the initial Miocene (Kintykchinian time, often regarded as part of the Baigubekian),

which was followed by a considerable regression. Having given way to a coastal plain with lagoonal andlacustrine sedimentation of the Aralian time, sea conditions were retained probably only in the most warped

part of the North Ustyurt trough (Voznesenskii, 1978,Fig. 33).

Basins of the Terminal EarlyMiddle Miocene(TarkhanianKonkian)

Northern BlackSea region.In the western coastalpart of the shelf, Tarkhanian sediments were mainly

wiped out by the subsequent Neogene erosion. Onlytwo exposures of the lowermost Tarkhanian thin (0.32.5 m) shellylimy sediments (near the Village ofTomakovka and the Settlement of Kamenka) withshallowwater assemblages of diverse sea mollusks,and the benthonic foraminifers and ostracodes (absolute heights +100 and +50 m), were retained. Thesame rocks were found in the Tchokrakian basal conglomerate (Nosovskii and Semenenko in (Neogene ,1986)).

The Tchokrakian deposits represented by sandyclayey and calcareous sediments with the benthonicfauna were penetrated only by boreholes in theDanube and Dniester interfluve, the Ingulets River

basin, near Kakhovka, and in the Nikopol region(Nosovskii and Semenenko in (Neogene , 1986)).Even in deepwater parts of the BlackSea depression,the sediments occur with the hiatus and conglomerateat the base. It is only in the most warped parts of thedepression that Maikopiantype clay accumulation

was still in progress at that time (Chekunov et al.,1976).

Karaganian sediments are widely developed, uninterruptedly continue the Tchokrakian transgressioncycle and occur on Miocene, Paleogene, and Precam

brian rocks. The sediments are represented by sandyclays replaced eastwards by limestones 12m thick in

the peripheral part. Near Nikopol, Karaganian greenclays are stripped by deep quarries at a height of+25+30 m. Beds with Spaniodontella, Ervilia andFoladaare of similar distribution, but beds with Erviliarepresent a regressive series.

The Konkian beds are widely developed in the eastern part of the BlackSea region, where they occur onthe Karaganian deposits, and only in the northernmost part they overlap transgressively the Paleogene

beds. The Sartaganian beds of the Konkian regionalstage, which are composed of sandyclayey facies(0.51.5 m) with a rich polyhaline fauna, occur with ahiatus on beds with Barnea (Nosovskii and Semenenko in (Neogene , 1986)). The Veselyanian beds

are of a wider development and exhibit a greater thickness compared to the Sartaganian beds. The Veselyanian beds are exposed on the Konka River at a heightof about +80 m. Regression, a continental nondeposition, during which erosion annihilated a major part ofthe sediments is confined to the terminal Konkian.

VolgaDon Interfluve and Ciscaucasia.The northern boundary of Tarkhanian marine sediments passesthrough the southern part of the presentday Timashevskaya bench at depths ranging from from 1100 to


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2500 m and in the northern slope of the Kuban depression at depths ranging from 350 to 700 m. Near the

basin slopes, clay conglomerate is found at the base ofthe Tarkhanian interval, which indicates the transgressive overlapping of Maikop deposits by Tarkhanian

beds. Northerly, in sections of some boreholes, redclays of continental genesis (the North Ladozhskaya,Uspenskaya and other areas) with thin interlayers of

microconglomerates and breccias at the base, whichare conventionally assigned to Tarkhanian deposits,underlie the Tchokrakian deposits. In the terminalupper Tarkhanian, a regional hiatus (Bogdanovich andBuryak in (Neogene , 1986)) and erosion of sediments on uplifted areas (the Yuzhnaya Andreevskayaarea) were established even on the territory of westernCiscaucasia.

In the central and eastern Manych region,Tchokrakian deposits occur with a hiatus on clays ofthe Maikop Group at a height of +50 m. The depositsare represented at the base by inequigranular sands

with quartz pebbles and limestone interlayers with theearly Tchokrakian fauna and pass up the section into

silty clays with jarosite and horizons of obliquely laminated coarse sands (Rodzyanko in (Neogene ,1986)). Mollusks Lutetia intermedia(Andr.), characteristic of the upper Tchokrakian (data of A.S. Zastrozhnyi), were found in sands of the upper beds.

In the western part of the West Kuban trough, onnumerous areas (Pribrezhnaya, Generalskaya,Novaya, Chumakovskaya, etc), there were strippedsandysilty members with inclusions of breccias andpoorly rounded conglomerates, indicating the migration of sediments into depression areas along under

water paleoincisions, during periods of shorttermfalls in the sea level in the Tchokrakian basin.

The fall of the sea level was substantial at theTchokrakianKaraganian boundary, which is evidenced by the appearance of coarse terrigenous faciesand freshwater mollusks in basin facies (on the BelayaRiver). Cobble beds (25 m thick), indicating tracesof a paleoriverbed were penetrated by borehole 8 onthe Sladkovskaya area at the base of the Karaganiandeposits, in the northern slope of the West Kubandepression, at the boundary with the Timashevskaya

bench. Coarse clastic deposits at the top of theTchokrakian sequence were encountered also on theGrivenskaya area (BH 59). A sandysilty member(productive member I according to the nomenclatureof the Pribrezhnyi deposit) was fragmentarily traced

even in the deepwater part of the West Kuban depression at the KaraganianTchokrakian boundary.

Karaganian deposits are more widely developedcompared to Tchokrakian ones. Their northern

boundary reaches the DonSal interfluve, comes tothe western Ergeni and Manych region, and has beentraced on the southern slope of the Karpinskii Ridge inthe Caspian region. Karaganian deposits are exposedon the day surface in the Miotsenovaya Ridge at anabsolute height of about +70 m. The sequence com

prises pebble, gravel, and shell detritus, indicating theproximity of the older shoreline. In the northern partof the western Ciscaucasia, the Karaganian depositsare composed of sandstones with minor clay and conglomerate interlayers and coquina beds with Spaniodontella pulchella Baily and Barnea ustjurtensis

Andrus (the Kushchevskaya area).

The boundary of the Konkian marine deposits

passes along the Miotsenovaya Ridge in the Manychregion, along the Sal River toward Novocherkassk.Konkian deposits are missing on the Kamennaya BalkaUplift and the Sal Rampart, and the lower Sarmatiandeposits transgessively overlap the Karaganian deposits.In the Miotsenovaya Ridge, the Konkian deposits occuron the eroded surface of the Karaganian deposits at aheight of 0+10 m, and the base of the deposits sharplyplunges down to a depth of 100 m in the Manychdepression. A basal horizon made of coarsegrainedsands with pebbles, indicating the proximity of the basinshoreline is traced at the base of the sections.

West of the Miotsenovaya Ridge, near the villagesof Divnoe and Priyutnoe, Kartvelian and Konkiandeposits were established in borehole sections at anabsolute depth of +30+40 m. The deposits are represented by clays and sands with a total thickness notexceeding 10 m and comprising the characteristicmollusk fauna: Barnea ustjurtensisEichw., B. ujratamica

Andr. (Kartvelian), Ervilia trigonula Sok., CorbulagibbaOlivi., Dentalium sp., Spiratella sp. and others(Konkian).

Mangyshlak Peninsula, and Ustyurt Plateau,Northern Aral Region.Tarkhanian deposits are missing on the Mangyshlak Peninsula but occur with a hiatus on the Paleogene or Lower Miocene deposits insections of the Ustyurt chink and are represented there

by a thin marl or coastal facies: pebblebed and sandwith Crassostrea gryphoides(Schl.), and others.

Tchokrakian deposits also occur with a sharpunconformity on the Cretaceous to Lower Miocenerocks. Coastal coarsegrained calcareous sandstones

with the early Tchokrakian fauna are known on theTyubKaragan Plateau and in other sections of northern Mangyshlak (Khondkarian et al., in (Neogene ,1986)). On the Ustyurt Plateau, the Tchokrakiandeposits are represented by coastalcontinental red

beds and gray clays as thick as tens of meters, whichaccumulated under conditions of a sea basin.

The Karaganian deposits are developed on theMangyshlak Peninsula more extensively than theTchokrakian deposits and also occur with a sharptransgressive overlapping on the Cretaceous, Paleogene, Maikopian, and Middle Miocene deposits. TheKaraganian deposits are represented by sandymarlyclayey deposits of small thickness. Varna(Ervilia) beds are developed in the facies of detritalgypsum limestone but only sporadically (Khondkarianet al., in (Neogene , 1986)). Kartvelian (Folada) bedsare more widely developed than the underlying bedsand in places occur with transgressive overlapping on


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Cretaceous, Eocene, or Oligocene deposits. They arecomposed of limestones and sandstones (16 m). Thelower Karaganian (Arkhasheni) beds are less dispersedin northern Ustyurt compared to the Tchokrakiandeposits and are represented by alternating clays,sandstones, marls, and limestones. The thickness ofthe deposits from the Karaganian horizon in the eastern Caspian region varies from 70 to 100 m.

The Konkian deposits are still less developed thanKartvelian and are represented by marls with limestone and sandstone interlayers tens of meters thick(Khondkarian et al., in (Neogene , 1986)).

Basins of the Terminal MiddleLate Mioceneand Pliocene (Sarmatian, Meotian, Pontian,

Kimmerian, Akchagylian)

Northern BlackSea Region. Sarmatian depositsare widespread throughout the whole of southernUkraine and occur with a transgressive overlapping onMiddle Eocene sediments, as well as Paleogene and

Precambrian rocks and the weathering crust along theslope of the Ukrainian Shield. The deposits are widelydeveloped in the western parts of the region and markthe freest contacts with the Carpathian basin in theearly Sarmatian.

The lower Sarmatian beds are represented in marginal facies mainly by sandyclayey sediments 12 mthick. In places, the beds, like the middle Sarmatiandeposits, occur with a transgressive overlapping on theUkrainian Shield and enter into the southern part ofthe DnieperDonets depression. In the quarry nearthe Village of Gubinikha, 50 km northnortheast ofDnepropetrovsk, the lower and middle Sarmatiansandylimy sediments occur at an absolute height of+125+135 m (Ivanova et al., 2007).

Middle Sarmatian deposits are less extensivelywidespread in the Valash trough in Moldavia, but further eastward the deposits occur with a transgressiveoverlapping on most of the territory and pass throughthe Ukrainian Shield. It is likely that the most shallow

water facies are eroded along the slope of the Ukrainian Shield. However, the presence of thin interlayers

with fossil plants and terrestrial gastropods indicatesthe proximity of the shoreline.

The distribution of upper Sarmatian depositsroughly coincides with that of the middle Sarmatianrocks but does not extend to the northernmost boundaries of their occurrence. Khersonian deposits oftenexhibit an unconformable mode of occurrence with ahiatus (Chekunov et al., 1976). In the DanubeDniester interfluve, Khersonian beds are represented byantedelta and freshwater sediments, and easterly, theyare composed of limestones with Maktra, hydrobiides,and freshwater fauna. In the basin of the Yuzhnyi BugRiver and further eastward, the deposits give way tofreshwater sands of the Balta Formation, corresponding to the Khersonian Substage of the Sarmatian,

Meotian, and Pontian (Nosovskii and Semenenko in(Neogene , 1986)).

Meotian sediments occur with a hiatus throughoutthe whole region and are less common there (Figs. 1,2b). In the DanubeDniester interfluve, the lowerMeotian deposits are represented by clays, siltstones,and sands with sea fauna, which alternate with brackishwater and freshwater facies and beds with terres

trial mollusks (Roshka in (Neogene , 1986)). Lumpy,greenishgray clays with rare freshwater fauna correspond to the upper Meotian. East of the DniesterRiver, terrigenous deposits 23 m thick, giving way toorganic limestones further eastward, are also predominant in the marginal facies.

Pontian deposits represented by the lowerNovorossian Substage occur mainly on the Meotiansediments. The deposits overlie the Precambrian rocksand their weathering crust only in the Krivoi Rogregion (Nosovskii and Semenenko in (Neogene ,1986)). Marginal facies are represented by olitic andcoquina limestone. According to data acquired by

A.L. Chepalyga and T.A. Sadchikova (1982) on theshelf of the DanubeDniester interfluve, sealevelfluctuations in the early Pontian proceeded every 4050 ka and reached 2530 m. The sea level rose fourtimes, and the second transgression was the maximal

when mollusks of the sea genesis Parvivenus widhalmiandAbra tellinoidesappeared. The sea left the northern Black Sea region in Portaferian time and thenremained within the current boundaries.

Kimmerian deposits were established in tworegionson the Dnieper left bank in its lower reachesand in the northern Azov region (Nosovskii and Semenenko in (Neogene , 1986)). The deposits occur

below the base level of erosion and are known only in

boreholes. They are represented by ferruginous sandstones with oilitic ore lenses and clays occurring withtransgressive overlapping on Pontian, Meotian rocks,as well as rocks of the basement in places (in the Azovregion). The absolute height of the roof of the Kimmerian rocks makes up 12 m in the Melitopol region.

Kuyalnik beds in the Odessa region fillinPliocene incisions, representing at present theKhadzhibei and Kuyalnik lagoons, in which theytransgressively overlap the Pontian and Meotian sediments. The beds are also known on shores of theTiligul lagoon. They were penetrated by boreholes at adepth of 7090 m, where they overlie the Kimmeriansediments without a visible hiatus (Nosovskii and

Semenenko (Neogene , 1986)). In the northern Azovregion, the Kuyalnik deposits also occur on the Kimmerian sediments and underlie a thick cover of continental sediments (60 m).

VolgaDon Interfluve and Ciscaucasia.Sarmatiandeposits mainly overlie Konkian deposits but in placesoccur with transgressive overlapping on continentalanalogs of the Konkian, Karaganian, and Paleogenerocks. The deposits are developed along the southernframing of the Donets Basin, in central Ergeni, and in


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the zone of the Karpinskii Ridge in the Caspian region(Rodzyanko in (Neogene , 1986)). In more shallow

water facies, the lower Sarmatian deposits are represented by micaceous sands, occur on Konkian rocks,and are overlain by middle Sarmatian deposits. In theGashun depression, the lower Sarmatian depositsoverlie the Karaganian deposits with a clear erosionalhiatus and angular unconformity.

The middle Sarmatian deposits are more widelydistributed as compared to the lower Sarmatian and allthe successive rocks (Fig. 2b). Deposits are found up toabsolute heights of +100+120 m in the DonetskBasin and up to +140+150 m in the Kagalnik River

basin. On the Don Rivers right bank, the middleupper Sarmatian deposits are developed within theDonKumshats interfluve and exposed along thescarp of the Tsimlyansk Reservoir, where they occuron the Paleogene Kiev Formation and underlie thePontian, and more often Scythian, rock complexes.The deposits are represented by gray, graygreen car

bonate clays (up to 40 m), grayishyellow quartzglauconitic sands (2.535 m) with interlayers of light

gray, pinkish limestones with the total thickness varying from 8 to 42 m (data of A.S. Zastrozhnov).

Southerly, orogeny in the Greater Caucasus, whichtook place in the second half of the middle Sarmatian,

was accompanied by the formation of a band of shallowwater sediments around itsandstonecoquina

with conglomerate interlayers. Incisions and thickbeds (up to 10 m) of sands, pebbles and conglomeratesare found along the mouths and deltas of paleorivers(Pshekha, Ubin, etc).

In the late Sarmatian, the fall of the sea level anddeposition of sandycarbonaceous sediments wasestablished on the whole territory of the Western

Ciscaucasia. The irregular thickness of the sedimentsand abundant small incisions filled with sand andcoquina are characteristic of the northern platformpart. At the boundary with the Rostov salient, part ofthe Sarmatian deposits is represented by boggy facies

with lignite and charcoal (>7 m), which were strippedin the Zelenaya area. At the same time, in places,upper Sarmatian calcareous sediments are observed,even north of the middle Sarmatian deposits andfound in the region of the City of Morozovsk at anabsolute height of +140 m (Olkhovaya ravine,

V.G. Pronins data).

At the SarmatianMeotian boundary, on theTimashevskaya bench, incisions, paleochannels, andantedeltas of the paleoDonets River were formed,

which are traced from the Svobodnenskaya area (southof PrimorskAkhtarsk) to the northern slope of the

West Kuban depression. Sandycoquina deposits withinclusions of Eocene white marl cobbles were penetrated there in borehole sections. Above the top of theSarmatian deposits, boreholes Rogovskaya andDneprovskaya (on profile IIII* between boreholesKazachya 1 and Timashevskaya 5) penetrated Meotian sands of different thickness, dated by foraminifers

and comprising interlayers of pebble and breccia (up to35 cm in diameter). Based on the geological profileand thickness variations, the data are interpreted as anincision into the upper Sarmatian deposits and its filling with Meotian sands (Fig. 3). The incisions amplitude made up some tens of meters. Up the section, inthe same boreholes, several pebble interlayers also

within the sand sequence at the PontianMeotian

boundary were traced. The sands were dated to thePontian by ostracodes. Genetically, the deposits arelikely to represent an underwater antedelta with seamicrofauna.

The deepest incisions confined to the SarmatianMeotian boundary were traced by drilling and seismicdata on the Beisug area (data of L.P. Avtonomova andT.N. Pinchuk). The incision depth makes up 200250 m, The Sarmatian sediments and in places the

whole Miocene up to the Maikop sequence are cut.

In the Meotian, the sea substantially regressed southward as compared to the Sarmatian, and its boundarypassed north of Rostov. In the Donets Basin, Meotian

sediments rose to an absolute height of +80 m. UpperMeotian sediments are known on the Don Rivers leftbank near Bataisk. No Meotian beds, characterizedpaleontologically, have been found in southern Ergeni.South of the Manych River, the beds were penetrated in

boreholes near the Village of Divnoe and in the Salskregion at an absolute height of +20+30 m.

The early Pontian basin again advanced far northward and flooded vast areas north of Taganrog Bay, theDon River right bank, and Ergeni. Sediments are represented by limestonescoquina and sands, in places

with clay interlayers. They again reach a height of+100 m in the Donbas Basin and in the KagalnikRiver basin. The northernmost exposure of the Pontian deposits known in the Ergeni is located on theright slope of the Yashkul ravine at heights rangingfrom +35 to +75 m.

Deep incisions are traced within the Pontiandeposits on the Timashevskaya bench. They are proved

by boreholes in the Bryukhovetskaya (Cheredeev et al.,1972) and Lebyazhya areas and clearly seen in the profilein Fig. 3 (between boreholes Timashevskaya 5 and Chel

basskaya 40) as well as in the seismic profile (Fig. 6d).According to the correlation with the nearest datedboreholes, the incision corresponds to the middlePontian, though, a direct paleontological confirmation of the age is unavailable. The amplitude of inci

sion consists of 100120 m in these boreholes. Paleoincisions in the Kushchevskaya area were traced rightup the Karaganian; they are filled with Pontian sediments from 20 to 102m thick (BHs K27 and K29),composed of clays with sand and coquina interlayers.

A sharp shortterm facies rearrangement, a stratigraphic hiatus, and the appearance of terrestrial gastropods at the base of the upper Pontian Portaferian

beds were revealed in relatively deepwater sections ofthe Taman Peninsula.


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Timashevskaya5

Bryukhovetskayaarea

LebyazhyaChelbasskaya2

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Fig.

3.Thegeologicalsection

ofMiocenePliocenedeposits(bydrillingdata)alongprofileIIII*withintheTimashevskayabench,demonstratingthedistributio

nofsandysiltymem

bersintheplatformpartoftheNorthernCiscaucasia(afterT.N.Pinchuk).


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Northern Caspian Region and ForeUrals. Sediments of the whole Neogene are known in the CaspianLowland, though, they are fragmental and overlain byQuaternary deposits; therefore, coastlines there arenot traced to the Sarmatian. The middle and upperSarmatian coastal deposits were described in the UilRivers middle course; they extend toward the UralRivers middle coarse (BertelsUspenskaya et al., in

(Neogene , 1986)) and trace the far northwardextending shallowwater bay along the eastern part ofthe Caspian region to the ForeUrals Plateau. The bayof the Pontian sea basin also advanced there during themaximal transgression (data of S.O. Khondkarian in(Popov et al., 2004)).

In preAkchagylian time, a longterm hiatus with adeep fall in the sea level existed in the Caspian part ofthe basin, when a contrast erosion relief was formedand continental variegated sediments accumulated(see below for details). In Akchagylian time, basin

waters advanced far northward into the paleoVolgaand paleoUral river valleys and flooded vast regions ofthe Caspian depression. North of the Obshchii Szyrt,

the basin abruptly narrowed and formed the Volga bay,which was filled with deltaic sandyclayey sediments(Staroverov, 2005). During the maximal transgressionin the middle Akchagylian, the basin extended still farther northward and flooded river valleys of the middlecourse of the Volga, Kama, and Belaya rivers.

Mangyshlak, Northern Ustyurt.Lower Sarmatiandeposits occur with transgressive overlapping and ahiatus on older, from Cretaceous to Konkian deposits.They are represented throughout the region by basinfaciesshell limestone, marl, and clay; the shallowestfacies have not been preserved. The middle Sarmatiandeposits are of less widely distributed as they were sub

jected to more intense erosion. The deposits are alsorepresented by basin facies and occur either conformably on the lower Sarmatian sediments or with a hiatuson older deposits (Khondkarian et al., in (Neogene ,1986)). By the late Sarmatian, the sea left the UstyurtPlateau, and its sediments are known only in the Caspian part of the regionon the TyubKargan Peninsula and in the South Mangyshlak trough.

The lower Meotian deposits represented by limestones are developed only in the western part of theregion along the Caspian coast (Fig. 1). The upperMeotian deposits are more widely distributed, extendto Western Ustyurt, and are represented by marls withshell limestone interlayers.

The lower Pontian deposits are widely developedand extend to Eastern Ustyurt. The lower, Evpatorian

beds are developed on Mangyshlak, mainly in theSouth Mangyshlak trough, and in Western Ustyurt.Odessan beds overlap them with transgression or overlie the upper Meotian and Sarmatian sediments; the

beds are represented by limestone, marl, and clay(Khondkarian et al., in (Neogene , 1986)).

Akchagylian deposits are of limited distributionand make up small erosion remnants in cliffs of the

Caspian Sea. These are thin (0.510 m) marls andcoquina with small pebbles probably of middle

Akchagylian age.

INCISIONS OF NORTHERN RIVER VALLEYS

Erosion valleys of Maikop time are unknown onthe Scythian Plate and East European Platform; it is

likely that they were annihilated by the subsequenterosion in the Neogene. Incised river valleys retainedin the northern Aral region, where they were covered

with drilling and studied, due to the rich iron oredeposits that accumulated in deltaic conditions. Thedeepest incisions are dated to the terminal Eoceneinitial Oligocene and have an amplitude varying from20 to 7080 m, relative to the Eocene surface (Voznesenskii, 1978). The next stage of the deltaic ore deposition was related to the regression of terminal Ashcheairykianinitial Solenovian time; however, erosionincisions of that time are unknown as sedimentationproceeded under conditions of a coastal plain.

Valleys of large rivers also formed in the terminal

Baigubekian on the north of the Chelkar trough andwithin the Chokusin syncline (Voznesenskii, 1978)and went on functioning in the Tchokrakian. However,only their southern underwaterdeltaic parts haveremained, where the sediment thickness makes up1520 m. The depth of valley incisions is hard to assesson the basis of these data.

Data on the paleoDon River incision, which wereacquired by A.S. Zastrozhnov, allow us to assess thefall in the sea level during the preTchokrakian regression. The valley corresponding to the Zagista Formation is deepened by 150200 m relative to the preMiocene surface (Fig. 4). The absolute heights of the

riverbed vary from 150 m in the lower reaches to 160 m in the mouth. In the paleoriver delta, the bottom of the sediments that filled in the incision abruptlyfell down to 170 to 220 m.

The top of the formation also dips southward, butto a lesser extent than its bottom. For instance, the topoccurs at an absolute height of 75 to 80 m in themain valley, and only by 10 m lower than this height inthe delta. This is accounted for by an increase in the

base level of erosion during the subsequent transgression, as the result of which the formations thicknesssubstantially increases downstream of the paleoDonRiver.

According to paleontological data, accumulation

of the upper part (mainly clayey) of the Zagista Formation occurs in Karaganian time. The observedreversed magnetization of clays is characteristic of theupper half of the Karaganian (Molostovskii and Khramov, 1997). It is likely that the underlying thick basalhorizon formed in the early KaraganianTchokrakian.

The next incision preceded the accumulation ofthe Balka Formation, traced on the same paleovalleysegment as the Zagista Formation. The width of the


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ost

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Fig.

4.Thefacialprofilefor

sedimentsofthepaleoDonRiveralonglineVIIVII*(afterA.S.Zastrozhnov).In

dexesdenote:(sk)ScythianFormation,(er)ErgeniFormation,

(ov)OvataFormation,(blk)BalkaFormation,(zg)ZagistaFormation,(ap)Apsheronian,(ak)Akchagylian,(p)Pontian,(mk)MaikopGroup,(

ost)lowerMaikopOstra

codabeds.

mk12

N2

sk+Q

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v3


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Balka valley varies from 10 to 17 km, increasing up to5060 km in the delta zone. The absolute heights ofthe formation bottom make up 80 to 90 m, rising to20 m towards the slopes. An abrupt subsidence of theformation bottom down to 150 to 160 m is observedin the Yashkul basin (a segment of the delta). The formation top occurs at the same absolute height (about0 m) throughout the whole valley, which is related to a

considerable increase in its thickness in delta sections.According to palynological data, the Balka Formationis assigned to the Konkian regional stage.

The preSarmatian fall in the sea level resulted in theoverdeepening of paleoDon and paleoDonets valleys,

which were filled with river sands in the Sarmatian. Thewidth of the early Sarmatian Ovata valley reached 1220 km increasing up to 60 km in the delta. The incisionfloor occurs at an absolute height of 10 to 20 m in themain valley and plunges to 80 to 90 m in the delta.The hypsometric position of the Ovata Formationsroof is noted for its great stability: the roof was traced atabsolute heights of +35+45 m. Judging from palynological and paleomagnetic data, the valley was filledin

in the early Sarmatian.In the terminal Sarmatian, the sea level fell by 200

300 m, and the partially dried shelf was cut by deepvalleys, which were filled with alluvial sediments in theMeotian. A buried system of paleoDon riverbeds(Burukshun canyon), which was traced over 150 kmfrom the Ergeni Upland to the Egorlyk River valley,

was retained (Proshlyakov, 1999). The incisions continued functioning in underwater conditions in theearly Meotian as well and let the sandy material passinto the IndolKuban trough (Fig. 1). It is evidentfrom the structure of the sandy sequences that thesandy material drifted from three sides (from the

paleoDon valley on the east, from the Rostov protrusion, and from the Caucasus; data of T.N. Pinchuk).Lagoonalalluvial, sandyclayey deposits of theBurukshun Formation with rare Congeria accumulated in the paleoDon mouth region. Alluvial sands ofthe Yanovskaya Formation (up to 30m thick) correspond to the Meotian in the paleoDonets valley. Rivers on the territory of Moldova and southern Ukrainedeposited at that time vast trains of sandy deposits ofthe uppermost Kagul and Balta formations.

The next incision of the paleoDon River tookplace in the postearly Pontian time, which is confirmed by the superposition of rocks filling it (Ergenisands) on lower Pontian marine sediments. The width

of the Ergeni valley varied from 15 to 100 km. According to A.S. Zastrozhnovs data, the absolute heights ofits bottom vary greatly from 20 to 40 m in theGashunskaya, Zimovnikovskaya, and Yashkulskayadepressions, as well as to +100 to +160 m on the Volgaand Ergeni uplands and in the VolgaKhoper interfluves, which was controlled by the general pattern oftectonic structures.

According to data of seismic profiling, the depth ofthe paleoVolga incision made up 700800 m in the

initial Pliocene and the incision is traced below sediments of the recent central Caspian area (Leonov etal., 005). The depths of the incision of the paleoAmuDarya and paleoKuma rivers were similar. The sea

was retained only in the southern Caspian depressionwith a small Kura bay.

The central and western parts of the East EuropeanPlatform were cut by a not very deep but, ramified,

river system, whose position was similar to the recentone. The rivers carried voluminous material, whose

way was traced by seismic sounding and boreholes inantedeltas. The paleoDonets antedelta was locatedon the northern slope of the West Kuban depression.

A trough valley traced on the left banks of theKhoper and Don rivers up to the Tsimlyansk Reservoir

was developed in the paleoDon valley in the EarlyPliocene. The valleys depth makes up 1245 km.

Absolute heights of the main valley bottom make up+20+30 m on the north and decrease up to3040 m on the south. Judging from the complexof paleontological and paleomagnetic data, it began

forming in the middle Akchagylian and terminated inthe Apsheronian. A.S. Zastrozhnov distinguished theNagavskaya, Krivskaya, Khoper, and Kumylzhen formations within the Andreev Group. The first, second,and third formations make up a downwardpointingladder of terraces of Akchagylian age and the Eopleistocene Kumylzhen Formation overlies them.

It is likely that the preKumylzhen incision corresponds to the base level of erosion in the terminal

Akchagylian. The width of the Kumylzhen valleymakes up 1235 km, the absolute height of the valleys

bottom position is +70 m in the north of the regionand +10+20 m in the south.

DATA OF SEISMIC PROFILING

The seismic material available allows the subdivision of the section into several seismostratigraphiccomplexes, differing in the pattern of the wave record,and correlation with geological and paleontologicaldata permits the dating of the complexes. The waverecord pattern bears information about sedimentationenvironments. The intracontinental Upper Paleogeneand Neogene sections more often exhibit the parallel

banded structure, but a clinoform, obliquely laminated structure was also registered in some complexes.Obliquely laminated sequences were revealed withinthe Paleocene, Eocene, Maikopian, Sarmatian, Kimmerian, and Quaternary complexes. These forms of

wave recording clearly fix areas of transition from theshelf to abyssal parts of the basin, as well as indicate themain directions of the sedimentary material transportation. The results of sealevel fluctuations arereflected in seismic profiles as erosion boundaries ofseveral orders, buried paleoincisions, and specific clinoform peculiarities of superposition in slopes nearthe shelf edge.


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The correlation and interpretation of geologicaland geophysical data makes it possible to reconstructthe geological history of the region and show the environmental conditions, as well as the drifting of the sedimentary material in two paleogeographic schemes ofNorthern Peritethys for PaleoceneEocene and OligoceneEarly Miocene time (Fig. 5), as well as in aseries of paleogeological profiles, compiled along the

line of the seismic section (Figs. 6, 7).We have traced the evolution of the sedimentary

basin since the Paleocene. The seismostratigraphicanalysis of deep parts of the section, preceding the OligoceneMiocene time interval in the evolution of theCiscaucasian depressions, shows that in the Paleocenesedimentation history, we can distinguish at least threemajor cycles of relative sealevel variation, with a subsequent shelf edge motion southward. Sequences ofthe shelf and abyssal basin separated by a clear paleoslope are distinguished in the Eocene seismostratigraphic complex. The basins depth at that time was1000 m. A vast shelf zone with a depth of up to 200 moccupied the northern and northwestern periphery of

the basin, where gently sloping clinoform sedimentarybodies, fixing the relative sealevel fluctuations accumulated. The amplitude of the fluctuations in theEocene is hard to assess. The East European Platform,the Urals orogen, and the area of the recent Caucasusserved as provenances of the terrigenous material. Thedeposition center of the depression was locateddirectly on the site of the northern slope and foot of theCaucasus, where the thickness of CretaceousPaleogene deposits exceeds 3 km.

In initial Maikop time, at the place of the WestKuban depression, sedimentation in the abyssal basin

was in progress, gravitational sedimentary bodies rap

idly covered by thick abyssal sequences accumulated atthe foot of the continental slope. The Lower Maikopdeposits incline towards the continental slope insidethe abyssal basin, and the shelf sequences make upgently sloping clinoforms, thinning out toward theabyssal basin. Areas of the Rostov salient of the EastEuropean Platform, other parts of it, and the territoryof the South Urals continued to be provenances. It ismost likely that Caucasian sources of the terrigenousmaterial also supplied the basin with the material, butit is not observed on the seismic time sections, due tothe complicated wave pattern of these sections andrecent deformations in this part of the section. Thedepth of the depressions axial part was about 1000 m;

the depression opened into a vast eastern BlackSeabasin and probably was separated from it by a system oflocal seamounts (Popov et al., 2004).

Profile IIII* from the shallowwater shelf nearthe Rostov salient via the West Kuban depression(Figs. 6, 7) demonstrates the most extensive changesin sedimentation at the base and top of the Maikopdeposits, in the top of the Sarmatian deposits, and atthe base of the Pliocene deposits. The erosion boundary at the Maikop base is traced right up to the deepest

part of the depression. A major erosional unconformity and a pinching out of a considerable part of thesequence in the depressions northern slope areobserved within the Maikopian as well. Clinoformsequences inside the Maikop deposits, which probably

begin from the boundary between the middle andupper (Miocene) Maikop, correspond most likely todistal parts of submarine fans, which accumulated at

the base of the abyssal basin slope. The depth of thebasin exceeded 1000 m. The amplitude of pinchingout was assessed by the time section at 200250 m,

with a maximum of 500 m. The terrigenous materialwas derived at that time from the north.

From the terminal Maikop to the initial Sarmatian,the depth of the sedimentary basin declined and didnot exceed 500 m. A series of unconformities was registered in the Miocene, the oldest of which corresponds to the base of the Tarkhanian or Tchokrakianand correlates with the preTchokrakian erosionalhiatus and incision into Maikop deposits in marginalparts, which are traced on the seismic profile in theManych region and have an amplitude of about 200 m.

Unfortunately, the very marginal parts of the basinare not represented on the available profiles. Therefore, overlying members of Middle MioceneSarmatian deposits seem to be conformable.

An unconformity and erosional hiatus are observedin the Karpinskii Ridge region at the base of the Sarmatian deposits. It is likely that no substantial falls inthe sea level took place during the early and middleSarmatian. Lower Sarmatian deposits are conformable in the depressions axial part. In the northern partof the West Kuban depression, a synsedimentary onlapof Sarmatian deposits to the top of the MiddleMiocene deposits is established (Fig. 6c).The south

ern slope was characterized by relatively deepsea conditions of sedimentation. Traced on the south arepoorly expressed clinoform sequences, indicating atopodepression, which existed at that time and, which

was compensated later by the upper Sarmatiansequences.

The next unconformity and incisions are traced onthe northern slope of the West Kuban depression at the

base of the upper Sarmatian deposits, where incisionshad an amplitude of 200 m and in places cut the wholeSarmatian sequence. The filling of incisions was multistage, which suggests longterm continental conditions with a meandering riverbed.

Meotian deposits occur with unconformity and anerosional hiatus on the Sarmatian sequences in thenorthern slope of the West Kuban depression. It islikely that the sedimentary basin deepened at the SarmatianMeotian boundary, which caused a relativefall in the sea level: a shelf edge with a typical clinoform structure is registered 20 km north of borehole

Yuzhnaya Andreevskaya3. No unconformity isobserved in the depressions southern slope (Fig. 6b);most likely, a deeply submerged part of the basin waslocated there. As the result of subsequent sedimenta


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Fig. 5.Schemes of paleogeographic environments in the EuxinianCaspian area for (a) PaleoceneEocene and (b) OligoceneEarly Miocene (Maikop), compiled on the basis of seismic profiling. (1) Areas free of sediments, (2) area of Alpine deformations,(3) areas of subsequent sediment erosion, (4) area of slope erosion, (5) area of clinoform facies, (6) continental and littoral facies,(7) inner shelf zone; (8) outer shelf zone, (9) zone of shelf basins, (10) deepsea facies, (11) direction of clastic material drift inabyssal basins, (12) erosion and erosiontectonic benches, (13) boundaries of facies areas, (14) position of seismic profile and itsfragments.

tion, the sedimentary basin was completely compen

sated.

The next sharp, relative fall in the sea level resultedin the formation of deep incisions on the flat surface ofthe Timashevskaya bench, which were filledin withcontinental and lagoonal deposits, probably of late Pontian age. Deep valleys cut Miocene up to the Karaganiandeposits and reached a depth of 400500 m. Hence, thefall in the sea level during the Pontian could exceed500 m, which resulted in a complete draining of the vastspaces on the Timashevskaya bench and the development of a deep erosional pattern on it. A Pontian seismostratigraphic complex occurs with unconformity onthe underlying deposits and becomes thinner in the

depressions slopes. The sea level varied throughout thePontian and Meotian as well, which caused a floodingof the incisions and accumulation of lagoonal deposits.

A relatively calm synsedimentary downwarping and afilling of the epicontinental basin with marine shallow

water sediments took place in the early Pontian. On theTimashevskaya bench, previously formed incisions werenot only filled with sediments but continued deepeningin the periods of a low sealevel stand. It is likely thatnew incisions were confined to the terminal early Pontian. The amplitude of falls in the sea level made up50 m. By the middle Pontian, owing to a new rise in thesea level, the sediments had completely leveled the ero

sion topography on the Timashevskaya bench, and theupper sequences of the section exhibit a gentle dip there.

In the terminal Pontian, the downwarping in thecenter of the West Kuban depression strengthened,and the amount of sediments brought from the EastEuropean Platform became insufficient to compensate it. Therefore, by the initial Kimmerian, a shelfdepression more than 100m deep had been formedthere, in which sediments derived from the north andsouth, Western Caucasus began accumulating. This isconfirmed by a system of clinoforms on both slopes ofthe depression. The relationship among the systemtracts of shelf bodies suggests several cycles of sealevel

fluctuations in the evolution of the depressionfroma low to a higher sea level. Traces of at least four cyclesof relative changes in the sea level can be seen in theseismic profile. The amplitude of relative falls in thesea level might reach 150 m.

In preAkchagylian time, (preKuyalnik), a breakin sedimentation and erosion of sediments took place,

which were related to orogenic processes in theGreater Caucasus (East Caucasian folding phase).The processes were accompanied by a sharp fall in the

sea level, after which the West Kuban depression began

subsiding and hence was filled with sediments.Kuyalnik deposits occur with a sharp unconfor

mity on the underlying Lower Pliocene sequences andin places cut them off substantially. Judging from thedata of the seismic profile, the truncation made up100200 m. This indicated an abrupt fall in the sealevel and tectonic movements. A subsequent sealevelrise and transgression leveled the relief of the surface,and synsedimentary downwarping led to the accumulation of a thick (up to 700 m) epicontinentalsequence.

The sea left the West Kuban depression in theQuaternary. Several major cycles of sealevel fluctua

tions, independent of the Euxinian basin wererevealed in the eastern part of the Ciscaucasiainthe Manych and TerekCaspian depressions, as wellas in the Caspian Sea.

The structure of the Cenozoic section of the Eastern Ciscaucasia is comprehensively described in the

works of N.Ya. Kunin, S.S. Kosova, andG.Yu. Blokhina (1989, 1990). A thick clinoformsequence accumulated in the TerekCaspian depression. S.S. Kosova (1994) distinguished 12 clinoformsin its structure, which indicate reiterative sealevelfluctuations.

We have analyzed seismic sections within the north

ern and central Caspian Sea (Leonov et al., 2005;Kurina, 2007). In contrast to profiles of the Euxinianbasin, the sections are distinguished for the erosionalstructural unconformity available between Pliocene andthe underlying Miocene and Maikop Group deposits(reference horizon A). The Akchagylianlower Quaternary deposits occur with unconformity on theMaikop deposits in the western part, and they overlie theCretaceousEocene sediments in the eastern part.Miocene rocks were found only in the form of erosionremnants in the northern part of the studied territory andin the central Caspian Sea, where they are buried under

younger deposits and rose to a height of 150200 mabove the level of the preAkchagylian relief. The pre

Akchagylian base level of erosion equals 400500 mthere.

As the result of the fall in the sea level, a dense pattern of deep submarine and terrestrial canyons wasformed, along which a great quantity of terrigenousmaterial was transported into the inner parts of theCaspian sedimentary basin. Thick clinoformsequences of fans, accumulated within the continentalslope base and composed underwater parts of the pra

Volga delta north of the Apsheron Peninsula, as well as


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(a)

(b)

1 2 3 4 5 6 7

8 9 10 11 12 13 14

Sea ofAral

C

asp

ianSea

B l a c k S e a

12 250 km

Azov

Sea

Sea of

Aral

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asp

ianSea

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3N11

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Azov

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N11


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0 1 2

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N2Q

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rkn

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Levkinskaya30Fedorovskaya3KubanskayaSG1

Grishkovskaya3G

rishkovskaya2

Medvedovskaya3Kazachya1

Timashevskaya5

Chelbasskaya8

KuyalnikAnthropogene

Kimmerian

Pontian

Meotian

Sarmatian

KaraganianKonkian

Tchokrakian

middleupperMaikopian

lowerMaikopian

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Timashevskaya5

F

edorovskaya3

middleupper

Maikopian

lowerMaikopian

Paleoce

ne

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retaceous

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Kimmeridgian

Oxfordian

Callovian

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Yu.Andreevskaya3

Triassic

Middle

Jurassic

Chelbasskaya8

km

t,s

t,s

6km

Levkinskaya30

(d)

()

(c)

(b)

Fig.

6.Seismostratigraphic

sectionalonglineIIII*oftheregionalprofileacross(a)theWestKubandepressionand(bd)fragmentsofseismictimesectionsKrasnodarnefte

geofizikaTrustdata.

t,s


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0

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Lovlinskaya 30Fedorovskaya 3

Kubanskaya SG1Grishkovskaya 3

Grishkovskaya 2Medvedovskaya 3

Kazachya 1 Timashevskaya 5 Chelbasskaya 8

KyalnikAnthropogene

KimmerianPontian

Meotian

Sarmatian

KaraganianKonkianTchokrakian

middleupper Maikopian

lower Maikopian

Paleocene


lowerMaikopian

Paleocene

LowerEocene

UpperMaikopian

UpperCretac

eous

LowerCretac

eous

Kimmer

idgian

Oxfordi

anCall

ovian

MiddleJu

rassic

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Recent geologic section

0

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SarmatianKaraganianKonkian

Tchokrakian


lower Maikopian

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ian

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Paleocene

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oceneUpperEo

cene

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perEocene

Second half of the Pontian (Bosporian)

0

1

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lower Maikopian

Eocene

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lowerMaikopian

PaleoceneLowerEoce

neUpperEoc

ene

Middle Pontian (Portaferian)

km

km

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Fig. 7.A series of paleogeologic profiles illustrating the Western Ciscaucasia evolution in the terminal PaleogeneNeogene.


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0

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Paleocene

Lower Eocene

By middle Eocene

km

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Fig. 7.(Contd.)


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the praAmu Darya delta on the eastern periphery ofthe South Caspian basin. The Lower Pliocene basindeposits are developed only within the South and Central Caspian basins and the Nizhnyaya Kura depression. Their thickness exceeds 5000 m. The wave fieldpattern on seismic sections for these deposits is characterized by a thinly lamellar structure, dynamically

well expressed. The inner boundaries are conformable

relative to each other and with respect to the upperboundary. Up the section, there occurs a sequence ofAkchagylian age. It is separated from the underlyingproductive sequence by an unconformity passingthrough the reflecting horizon2. The wave field patternon seismic sections is obliquely laminated, clinoform.

Lower Pliocene deposits are missing from theNorthern Caspian basin, and the MiddleUpperPliocene (Akchagylian) deposits rest on Miocene, Sarmatian, Maikop, Paleogene, and even Upper Cretaceous deposits. Their thickness amounts to 50200 m.

Akchagylian deposits are developed throughout thewhole Central Caspian. They overlie mainly rocks ofthe productive sequence, but in places occur on Sarma

tian and Maikop deposits. The thickness of theAkchagylian deposits varies from 100 m in the abyssalpart to 500600 m in the coastal zone of the CaspianSea. Several phases of the rise and fall of the sea levelduring the Akchagylian sequence formation were established, which are marked by benches and complexes ofa low sealevel stand that appeared on the seismic sections. The horizon3boundary, which fixes the maximal fall in the sea level, represents the upper boundaryof the Akchagylian sequence. The sea level in the

Akchagylian basin varied from 0 to 150 m (Antipovet al., 2005).

DISCUSSION

The data presented are still too fragmentary andinsufficient for a correct qualitative assessment of thesealevel fluctuations in the Eastern Paratethys. Nevertheless, the approach, when the relative position andabsolute heights, at which sediments of transgressiveseries occur, are considered, the amplitudes of riverincisions on the platform side are taken into account,and structural features of sequences visible in seismicprofiles are analyzed, seems be the most adequate tothe posed problem. All the data discussed above allowus to suggest only a rough assessment of the extent oftransgressions and the amplitude of sealevel fluctua

tions in the Late EoceneNeogene basins of theParatethys (Fig. 8).

Two transgression phases of the Late Eocene(BelayaGlina) basin are registered when marinefacies are wedged into continental facies (Krasheninnikov and Akhmetiev, 1998, p. 197). Based on nannoplankton, the first phase is dated at the NP18 Zone,and the second, at the NP1920 Zone. At the boundary between the phases, there was a shortterm fall inthe sea level (by 50 m and more), accompanied by

cooling and anoxic events marked by bursts of Uvigerinaabundance (Marzuk, 1992). The second sealevelstand was higher; sediments of this phase occur withtransgressive overlapping on older deposits (the Mandrik beds on the Ukrainian Shield, the Balyklei beds inthe Volga region, and the Sumsar beds in the Ferganaregion and Tajikistan) and overlie the major part of thetectonically stable Ukrainian Shield with presentday

heights of 150190 m above sea level, pass far into theVolgaDon interfluve, the Volga region, and WesternSiberia. The height of the Late Eocene sealevel standduring the maximum transgression can be assessed atnot less than +150 to +160 m. These transgressionsand the following regression are undoubtedly associated with eustacy as the basin was still rather openprior to the initial Rupelian.

Regression in the terminal PriabonianinitialRupelian can be correlated with the base of the thirdorder cycle TA 4.4.4of the eustatic curve with the fallin the sea level of about 50 m (Haq et al., 1987). However, this event was much more extensive in the Eastern Paratethys. Based on the shoreline retreat and

incisions in the northern Aral region, the fall in the sealevel in the Paratethys may be assessed at 80100 m.The thickness of the layer removed in the course ofdenudation made up 100150 m (Krasheninnikov and

Akhmetiev, 1996, 1998). The regression and a changein paleogeographic relations were accompanied byradical alterations in sedimentation, which showed upeven in the deepest basins (Tugolesov et al., 1985;Robinson, 1995; Gillet et al., 2005), which was relatedto the tectonic reconstruction, variations in seawatercirculation, submarine erosion, and sediment redistri

bution.

The subsequent eustatic transgression in the initial

Rupelian also clearly showed up when the sea againflooded the DnieperDonets depression, the WestSiberian Lowland (Kurgan beds), invaded the Volgaregion, and reached the Tajik depression (Fig. 2a;Popov et al., 2004, map 2). We may judge by the absolute heights, at which the deposits occur, that thetransgression height exceeded +100 m, relative to thecurrent sea level. Though, in contrast to the global, theRupelian transgression in the Eastern Paratethysessentially ranked below the preceding transgressionin the Priabonian.

Deposits of the maximum Solenovian transgression with characteristic brackishwater fauna areexposed near the VolgaDon Canal at an absoluteheight of +80+90 m. The first, Solenovian, freshening of the Paratethys, the shoaling of the basin, and asubsequent regression are likely to be correlated intime with the beginning of the next cycle TA 4.4.5.Though, the next, most intense global regression inthe initial Chattian in Ciscaucasia (beginning of theTB 1 supercycle), which was dated at 30 Ma ago,poorly showed up in the Paratethys history. Accordingto nannoplankton and dinocyst dates, the boundary ofthe Chattian base in Ciscaucasia passes within the


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Fig. 8.The curve of quantitative assessments of main sealevel fluctuations for the EuxinianCaspian basin in the OligoceneNeogene and its correlation with the eustatic curve.

Broken line: in Eastern Paratethys column, the curve of sealevel fluctuations in the Caspian basin after its separation; in Eustacy curve column, fall in the sea level in the Mediterranean region during the Messinian crisis. The amplitude of the fall in thesea level exceeded 1500 m at 5.6 Ma ago. Numbers along the curve represent absolute heights of sealevel stand.

Morozkina Balka Formation (data of Ya. Krkhovskiiand N.I. Zaporozhets on the section of the BelayaRiver in (Akhmetiev et al., 1995)) and is not clearlystratigraphically expressed. In terms of paleogeography, the terminal Solenovian regression falls on thattime; however, its amplitude can be assessed at severaltens of meters, whereas in platform conditions, onlyMaikop Group deposits underlying the Pshekhiansediments were subjected to erosion.

The initial Chattian dated in the shallowwaterzone of the northern coast by the presence of Chlamysbifidathe zonal form of the Chattian horizon A, istransgressive in the Eastern Paratethys. Judging fromthe distribution of the sediments, the rise in the sealevel may be assessed at 6070 m, and higher and

lower values are considered to be distorted by successive tectonic processes. On the Turan Plate, the transgression reached its maximum in the second half of theChattianinitial Baigubekian, when marine sandysediments with Cerastoderma prigorovskii, Corbulahelmersenioccupied vast spaces in the northern Aralregion, eastern Aral region, as well as Kyzyl Kum andagain penetrated into the DnieperDonets Basin. Thesea had retreated by the terminal Baigubekian, sediments in marginal parts gave way to coastallagoonal

with freshwater fauna.

The terminal Chattian regression is hard to assessquantitatively. Judging from the shoreline retreat but

the lacking of incisions, we assume that heights may beclose to zero.

A new shortterm transgression took place in the initial Miocene (the late Sivashian, Karadzhalgan, andKintykchinian) when the sea flooded the southern partof the DnieperDonets basin, and invaded the easternpart of the Kopet Dag foredeep and the Alai trough.

After a short and intense transgression pulse in the veryinitial Miocene, the next Early Miocene basin wassharply regressive, though, remained normal marine interms of hydrology and corresponded in time to theBurdigalian transgressive basin. Based on the correlation of absolute heights for sediments, by theSakaraulian time, the sea level has fallen by 5060 m

relative to the Chattian transgression and continuedfalling in the Kozachurian. As these sediments are notexposed on the day surface beyond the depression zoneselevated at present, the absolute heights, at which thesediments were deposited should be considered as negative (below sea level).

The fall in the sea level in terminal Maikop timecan be assessed using data about the incision of thepaleoDon River, whose valley was overdeepened by150200 m, relative to the preMiocene surface, the

absolute heights being up to 160 m in its mouth area.Although A.S. Zastrozhnov dated sediments of theZagista Formation, which filledin the valley to theTchokrakian, the incision itself is likely to correspondto a more substantial unconformity in the terminalMaikop. In the Tarkhanian, the incision probablycontinued functioning as an erosion structure. It is notimprobable that the fall in the sea level in the terminalMaikop can be correlated with the eustatic regressionin the terminal Burdigalian (TB 2.2.3), and the subsequent Langhian transgression, with the Tarkhanian orTchokrakian transgression. However, exact dates ofthese events in the Paratethys raise heated debates:

whether or not the lowermost Tarkhanian is correlatedwith the Burdigalian or dated at the initial Langhian.

Data on the height of the rise in the sea level duringthe Tarkhanian transgression are lacking, except forthe overestimated heights of the occurrence of Tomakov beds. Judging from the fact that the deposits areextremely rare on the northern shelf, the absoluteheights of this transgression were hardly likely to have

been positive, with a subsequent decrease in them bythe terminal Tarkhanian, whose absolute heights havealso not been determined. The Lower Tchokrakiandeposits occur in the Manych region at an absoluteheight of about +50 m, which can very likely beaccepted as a rise in the level of these waters in the lateTchokrakian.

It is evident from the distribution of the sedimentsthat the Karaganian transgression was slightly lessextensive compared to the Sarmatian one and had twopeaks: in the Karaganian s. s. (Arkhashenian) and in theKartvelian separated by a fall in the sea level in Varneantime. The available data on absolute heights, which thesediments were found to occur at (about +70 m in the

VolgaDon interfluve), seem to be quite real.

The Karaganian transgression corresponds in timeto a high sealevel stand TB 2.2.3. But it was accompanied by a sharp change in hydrology and, probably,represented a barrier transgression, determined byregional tectonics. It is most likely that the appearanceof the marine fauna in the middle Karaganian (Var

nean or Turkmenian beds) was related to the eustaticrise in the sea level, when the whole basin from Bulgaria to Kopet Dag and the Ustyurt foothills was populated by few marine species, absolutely alien to theKaraganian endemic fauna.

The presence of the preKonkian (Balka) incisionof the paleoDon River suggests a fall in the sea leveldown to 80 to 90 m and its further rise up to 0 to+30 m (the level of the Balka Formation top). It isunclear whether this regression took place in Varnean


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200 150 100 50 0 m 50 100 150 200 250 300

+150

40

0 700100

200

150

+80

+40+30

+70

+50

160

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+70

+60

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0

5

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Berggren

Time(Ma)

Medi

stages

Stages of

Eastern Para

tethys

Eastern

Paratethys

Eustacy curve

(Haq et al., 1987)

PontianCalabrian

Gelasian

Piacenzian

Zanclean

Messinian

Tortonian

Serravallian

Langhian

Burdigalian

Aquitanian

Chattian

Rupelian

Priabonian

Akcha

Kuyalnik

Kimmerian

Pontian

Meotian

upper(Khersonian)

middle(Bessarabian)

terranean

et al., 1995 200 150 100 50 0 m 50 100

5.6 Ma5,9 Ma

TB3.3.4

TB3

TB 2.2.6

TB 2.2.4

TB 2.2.3

TB 1

A 4.4.5

A 4.4.4

lower(Volhynian)

KonkianKaraganian

Tchokrakian

Tarkhanian

Kozachurian

Sarakaulian

Karadzhalgan

Kalmykian

Solenovian

Pshekhian

Beloglinian

Sarmatian

Upper

Oligocene

LowerMiocene

MiddleMiocene

UpperMiocene

Pliocene

Eocene

Series

Caspian

?

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time or at the boundary between the Kartvelian andSartaganian. The first alternative seems to be the mostplausible as Varnean beds are known on the platformonly in boreholes and in the Kopet Dags warped partof the Turan Plate.

The Konkian transgression was not intensive andreached its maximum in the second half of the Konkianin Veselyanian time. The data available on the

occurrence of the sediments at the absolute heights of+30 to +40 m west of the Miotsenovaya Range seem to

be quite real.

The preSarmatian fall in the sea level was responsible for the appearance of paleoDon and paleoDonets valleys, whose bottom is located at the absolute heights of 10 to 20 m in the main valley andabruptly plunges in the delta down to absolute heightsof 80 to 90 m. The hypsometric position of the topof the fillin material (Ovata Formation) is distinguished by its great stability: it is fixed at absoluteheights of +35+45 m, which can be assumed as theheight of the initial stage of the early Sarmatian transgression. On the basis of a wide distribution of the sediments of this age, the middle Sarmatian rise in the sealevel can be assessed at +60+80 m, making higherabsolute heights of the occurrence of sediments to bedistorted by a subsequent tectonic uplifting.

According to seismic and drilling data, the unconformity and incisions with amplitudes of up to 200250 m are confined to the middleupper Sarmatian

boundary. In the late Sarmatian (Khersonian), the sealevel resumed but remained unstable; incisions wenton forming on the shelf. The basin became closed,freshened to a great extent, and its dimensionsremained extensive but in most cases did not reach themiddle Sarmatian sea boundaries.

Our colleagues from Central Europe correlate theSarmatian high transgression with cycle TB 2.2.6.Then, a deep eustatic regression set in (the initial cycleTB 3), which showed up in the terminal Sarmatian s.s. (according to E. Suess) or in the midmiddle Sarmatian s. l. (according to BarbotdeMarni, (Neogene ,1986)), when the sea left the Pannonian and Carpathian depressions. However, corresponding to thattime (10 Ma ago), in the Eastern Paratethys there arecoarser facies against the background of the still persisting middle Sarmatian transgression, and a substantialfall in the sea level (by 200250 m in the northern slopeof the West Kuban depression) took place later, at the

boundary between the middle and late Sarmati

Popov 2010 Sea Level Fluctuation

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