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Rise and fall of the Paratethys Sea during the Messinian Salinity Crisis
Earth and Planetary Science Letters 290 (2010) 183–191
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Earth and Planetary Science Letters j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / e p s l
Rise and fall of the Paratethys Sea during the Messinian Salinity Crisis W. Krijgsman a,⁎, M. Stoica b, I. Vasiliev a, V.V. Popov c a b c
Paleomagnetic Laboratory ‘Fort Hoofddijk’, Utrecht University, Budapestlaan 17, 3584 CD, Utrecht, The Netherlands Department of Palaeontology, Faculty of Geology and Geophysics, University of Bucharest, Bălcescu Bd. 1, 010041, Romania VNIGRI, All-Russia Petroleum Research Exploration Institute, St. Petersburg, Russia
a r t i c l e
i n f o
Article history: Received 9 July 2009 Received in revised form 16 November 2009 Accepted 8 December 2009 Available online 3 January 2010 Editor: P. DeMenocal Keywords: Paratethys Mediterranean Messinian Salinity Crisis magnetostratigraphy flooding sea level change
a b s t r a c t Extremely thick evaporite units were deposited during the so-called Messinian Salinity Crisis (MSC: 5.96– 5.33 Ma) in a deep Mediterranean basin that was progressively disconnected from the Atlantic Ocean. A crucial, but still poorly understood component in Messinian evaporite models is the connectivity between Mediterranean and Paratethys, i.e. the former Black Sea domain. Inadequate stratigraphic correlations and insufficient age control for Paratethys sediments have so far hampered a thorough understanding of hydrological fluxes and paleoenvironmental changes. Here, we present a new chronology for the Eastern Paratethys by integrating biostratigraphic and paleomagnetic data from Mio–Pliocene sedimentary successions of Romania and Russia. We show that a major flooding event from the Mediterranean surged the Paratethys basins at the Maeotian–Pontian boundary, 6.04 million years ago. This indicates that sea level in both Mediterranean and Paratethys was high at the beginning of the MSC. We argue in favor of changes in Paratethys–Mediterranean connectivity to initiate the MSC in combination with elusive tectonic processes in the Gibraltar arc. A subsequent fall of Paratethyan water level closely coincides to the Mediterranean isolation-event, corresponding in age to the glacial cycles TG12–14 (5.60–5.50 Myr). In the latest Messinian, a major climate change towards more humid conditions produced a positive hydrological balance and likely a transgression in the Paratethys, although our stratigraphic resolution cannot exclude a possible relation to the Pliocene flooding of the Mediterranean here. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Major sea level fluctuations, causing dramatic paleoenvironmental changes and related mass-extinctions, form an intricate part of Earth history (Hallam and Wignall, 1997). Renowned examples are the biblical flood of Noah and the Messinian Salinity Crisis (MSC) of the Mediterranean. Geological investigations indicated that a great deluge surged the Black Sea basin roughly 8000 years ago, rapidly raising the lake level by some 100 m (Ryan et al., 1997, 2003) so that civilizations and populations inhabiting the Black Sea shores may have suddenly drowned (Ryan and Pitman, 1998). The sudden influx hypothesis is highly debated between geologists and archeologists (Aksu et al., 2002), but may also have occurred in late Messinian times (Hsü and Giovanoli, 1979) when the Black Sea domain was part of the Eastern Paratethys (Fig. 1). During the Messinian (7.24–5.33 Ma), the Mediterranean became progressively isolated from the Atlantic Ocean, triggering widespread precipitation of gypsum (5.96–5.6 Ma), massive salt deposition (5.6–5.5 Ma), and a dramatic sea level lowering followed by brackish water environments of “Lago-Mare” (Lake Sea) facies (e.g. Hilgen et al., 2007; Krijgsman and Meijer, 2008; Roveri et al., 2008). A catastrophic re-flooding from the Atlantic at the beginning of the
⁎ Corresponding author. Tel.: +31 30 2531672. E-mail address: [email protected] (W. Krijgsman). 0012-821X/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.epsl.2009.12.020
Pliocene (5.33 Ma) abruptly ended the salinity crisis by re-establishing open marine conditions in the Mediterranean (Hsü et al., 1973). The hydrological flux from Paratethys to Mediterranean is a crucial component in quantitative studies on paleocirculation patterns and precipitation models of evaporites (Meijer and Krijgsman, 2005; Flecker and Ellam, 2006), but connectivity between the two basins is controversial (Çagatay et al., 2006). Overspilling of Paratethys waters into the Mediterranean has been argued to explain the presence of brackish water fauna in the Lago-Mare sediments (Cita et al., 1978), but a lowering of Paratethys levels during the Messinian event is also suggested (Hsü and Giovanoli, 1979). Seismic profiles of the Black Sea basin show evidence of deep canyon cutting, but the exact stratigraphic position differs; at the base of the Pontian Stage (Dinu et al., 2005) or intra-Pontian (Gillet et al., 2007). Sequence stratigraphic interpretations on a seismic transect from the western Dacian Basin also reveal significant sea level changes within the Pontian Stage (Leever et al., 2009). Seismic and borehole data from the Pannonian Basin show unconformities as well, but these are interpreted to have a regional tectonic origin and no relation to Messinian drawdown (Magyar and Sztanó, 2008). A concurrent base level drop has been proposed for the Caspian Sea (Reynolds et al., 1998; Popov et al., 2006), although numerical ages are poorly defined. Paratethys time scales comprise regional stages (e.g. Maeotian– Pontian–Dacian or Kimmerian within the Mio–Pliocene interval) and substages (e.g. Odessian–Portaferrian–Bosphorian within the Pontian)
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Fig. 1. Paleogeographic map of the Mediterranean and Paratethys during the Messinian Salinity Crisis interval. Stars indicate locations of the sections and research areas. In the Dacian Basin, RS and PU = Râmnicu Sarat and Putna sections are located in the east Carpathian foredeep and TP = Topolog region is in the south Carpathian foredeep. In the Black Sea basin, ZR = Zheleznyi Rog section is located on the Taman Peninsula of the Russian Black Sea margin; SC = South Caspian Basin — Azerbaijan. Triangles locate astronomically dated Mediterranean MSC sections (see Hilgen et al. (2007) and Krijgsman and Meijer (2008) for details).
based on endemic ostracod and mollusc species. At present, correlations to the marine record are mainly tentatively based on rare incursions of nannofossils (e.g. Marunteanu and Papaianopol, 1998) and chronostratigraphic resolution is generally inadequate to determine causal relationships with the Mediterranean MSC events. Here, we construct a robust biochronologic framework for the Paratethys domain by integrating paleomagnetic data with detailed paleontologic analyses of endemic Paratethys faunal (molluscs and ostracods) assemblages from sections of the Dacian and the Black Sea basin (Fig. 1). The integrated stratigraphic results of these individual domains will unfold the intrinsic paleoenvironmental evolution of the Eastern Paratethys during the Messinian Salinity Crisis with revised chronologic constraints.
successions covering the MSC interval, and integrate the results with the magnetostratigraphic data (Vasiliev et al., 2004, 2007). The target section in the Black Sea Basin is on Taman Peninsula (Russia); the classic Zheleznyi Rog (Iron Cape) section is 500 m long and covers ∼ 5 Myr of sediments (Fig. 1). The section has been extensively studied by several Russian research teams (Semenenko, 1979; Trubikhin, 1986; Filippova, 2002), but despite the presence of paleontological, paleomagnetic and (K–Ar) isotopic data, correlations to the GTS are still highly debated (Chumakov et al., 1992; Pevzner et al., 2003; Popov et al., 2006). We have focused here on the Mio– Pliocene interval of the Zheleznyi Rog section and resampled the uppermost Maeotian, Pontian and the lower Kimmerian for paleomagnetic and biostratigraphic purposes to establish direct correlations to the integrated stratigraphic record in the Dacian Basin.
2. Sections and setting
3. Paleomagnetic results
Paleomagnetic studies recently showed that excellent biochronological control for the Paratethys can be obtained from continuous sedimentary sequences (Vasiliev et al., 2004, 2005). The Dacian Basin in particular comprises several complete and well-exposed sedimentary successions from the Pontian Stage, consisting of fossiliferous silts and sands indicative of lacustrine and fluvio-deltaic environment (Panaiotu et al., 2007). These sediments accumulated rapidly in a foredeep setting, providing a thick continuous exposure of the MSC interval (Vasiliev et al., 2004). The Râmnicu Sărat and Putna sections (Fig. 1) were shown to carry a primary magnetic signal produced by greigite magnetofossils, providing reliable records of ancient geomagnetic field variations (Vasiliev et al., 2008) thus allowing excellent correlations to the standard Geological Time Scale (GTS) and to magnetostratigraphically dated sections in the south Carpathian foredeep (Fig. 1; Vasiliev et al., 2005). It showed that the major paleoenvironmental changes in the late Miocene and Pliocene were synchronous within the Dacian Basin, although these magnetostratigraphic studies were lacking direct biostratigraphic control. Here we present a detailed ostracod biostratigraphy for the Râmnicu Sărat section in the east Carpathian foredeep, one of the most continuous
Standard paleomagnetic measurements have been performed to establish a new magnetostratigraphic record for the Zheleznyi Rog section (Fig. 2). Thermal (TH) demagnetization was applied with small temperature increments of 10–30 °C up to a maximum temperature of 580 °C in a magnetically shielded furnace. Alternating Field (AF) demagnetization was performed with small field increments, up to a maximum of 100 mT, using an in-house built robotized sample handler controller attached to a horizontal 2G Enterprises DC SQUID cryogenic magnetometer. Demagnetization results were analyzed using orthogonal plots and stereographic projections. The direction of the NRM components was calculated by principalcomponent analysis. Dual polarity components were isolated in most samples between the 270–420 °C (Fig. 2A–C) or 20–45 mT demagnetization steps (Fig. 2D,E). Several specimens were demagnetized up to 580 °C or 100 mT (Fig. 2F). We recognized three polarity intervals in the studied succession, normal polarities at the basal (upper Maeotian) part, reversed polarity in the middle (Pontian) part and normal polarity in the upper (lower Kimmerian) part. An alternating gradient magnetometer (Princeton Measurements Corporation, MicroMag Model 2900 with 2T magnet, noise
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Fig. 2. Demagnetization results from the Zheleznyi Rog section. In the Zijderveld plots (A–F), red numbers represent the temperature steps in °C for the TH demagnetization (A–C,F), and blue numbers indicate the field steps in mT for AF demagnetization (D–E). Down-right are the stratigraphic levels in meters. The diagrams are presented with tectonic tilt correction (th/tc or af/tc). The red (blue) lines indicate the ChRM direction from the TH (AF) demagnetization. The red circles and the blue diamonds are the symbols used in Fig. 4. Representative first order reversal curves diagrams (G, H) have contours closing around a single domain (SD) peak at Bc = 40–50 mT, indicative for greigite as magnetic carrier.
level 2 × 10− 9 Am2) was used to measure first order reversal curves (FORC) diagrams. The domain state, and particularly the amount of magnetic interaction emerges clearly from FORC diagrams. Contours closing around a single domain (SD) peak at Bc = 40–50 mT (Fig. 2G,H) are similar to those previously reported for greigite in the Dacian Basin (Vasiliev et al., 2007). 4. Rise in Paratethyan water level at the Maeotian/Pontian boundary The Paratethyan ostracod distribution in Mio–Pliocene times reflects evolutionary trends, but also the influence of paleoenvironmental changes. Changing the connectivity with the open ocean influences the bathymetry and salinity of Paratethyan basins, which is reflected in the marginal faunal assemblages of the Dacian Basin. We present here the results of a detailed micro-paleontological study, focussing mainly on ostracods and foraminifera of the Râmnicu Sărat section, which provides a high-resolution biochronology for the Eastern Paratethys (Fig. 3). Our biostratigraphic results show that the fossil ostracod assemblages from the upper Maeotian (Moldavian substage) comprise a low number of species, of which Cyprideis pannonica is common and Paracandona albicans and Leptocythere blanda are rare (Fig. 3). These fossil assemblages are indicative of sub-littoral fresh- to brackish water environment, suggesting that the upper Maeotian sediments in the east Carpathian foredeep are associated with temporary lakes on flood plain areas. The marginal areas of the Dacian Basin thus evolved in almost freshwater conditions, while the paleoenvironment was dominated by littoral and fluvial conditions. The Maeotian assemblages are rapidly replaced by lower Pontian (Odessian/Novorossian) associations (Fig. 3). The lower Pontian ostracod assemblages indicate relatively deep basinal environments, and a widespread rise of relative sea level. At this time, characteristic layers formed comprising monospecific Congeria novorossica molluscs (Stevanovic et al., 1989). Our detailed study of the Maeotian–Pontian transition interval, for the first time, reveals the presence of
agglutinated and calcareous benthic foraminifera and planktonic foraminifera (Streptochilus and Tenuitellina species) of marine origin in the Upper Miocene of the Eastern Paratethys (Fig. 4A–J). This indicates that a major marine deluge took place by re-establishing a connection through the Mediterranean to the Atlantic, or alternatively to the Indian Ocean. Magnetostratigraphic results show that this flooding interval occurred synchronously in the Dacian and Black Sea basins near the paleomagnetic reversal C3An.2n(y), and is dated at 6.04 Ma (Fig. 4). The marine environment in the Eastern Paratethys was only a short-lived feature of maximum 10 kyr, after which micropaleontological assemblages are again dominated by ostracods indicative of brackish water conditions. After this transgressive interval, the lower Pontian ostracod fauna reacted to the changes in bathymetry and salinity, while variations in interbasinal connectivity allowed migration of species. It generated a “bloom” of ostracod species in the Odessian at ∼5.95 Ma (Fig. 3), especially in the predominantly pelitic deposits that are well-developed in lower Pontian times. A transgression at the Maeotian/Pontian boundary has previously been documented from wells and seismics in the western Dacian Basin (Jipa, 1997; Leever, 2007; Leever et al., 2009) and is biostratigraphically marked by a migration of faunal elements from the Pannonian basin (Hungary–Austria) into the Eastern Paratethys and by migration of typical Aegean species into the Black Sea domain. This is supported by earlier observations of a short calcareous nannofossil influx at the Maeotian/Pontian boundary interval (Marunteanu and Papaianopol, 1998). Biostratigraphic data from the Caspian Basin in Azerbaijan reveal similar changes in faunal elements indicating that this event extended into western Asia (Stevanovic et al., 1989). 5. Fall in Paratethyan water level during the Portaferrian A marked paleoenvironmental change occurs at the middle Pontian (Portaferrian) of the Dacian Basin. The study region in Romania shows a transition to more sandy facies, with ample presence of wave rippled
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Fig. 3. Ostracod distribution of the Râmnicu Sărat section in the east Carpathian foredeep of the Dacian Basin. The magnetostratigraphic pattern is after Vasiliev et al. (2004) and correlates excellently to the GTS. It allows high-resolution dating of the ostracod assemblages and related stages and substages. The resulting new ages of the (sub)stage boundaries are indicated.
sediments indicating deposition in shallow water, probably on the lower shore face (Panaiotu et al., 2007). The Portaferrian thus represents a regressive event where the bathymetry of the Dacian
Basin decreased. In marginal settings, the rich Odessian ostracod fauna indicative of basinal conditions is replaced by littoral, fluvial and lacustrine Portaferrian species: Amplocypris dorsobrevis, C. pannonica,
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Fig. 4. Detailed integrated stratigraphic data of the Maeotian/Pontian interval. Pontian–Kimmerian are regional stages of the Black Sea Basin. Magnetostratigraphic data from Râmnicu Sărat are after Vasiliev et al. (2004), from Zheleznyi Rog of this paper. Red circles represent reliable directions from thermal demagnetization, whereby small circles denote greigite, large circles magnetite. The blue diamonds indicate directions from alternating field demagnetization .The Maeotian–Pontian boundary interval is marked by a short influx of marine calcareous benthic foraminifera (A–C) Porosononian ex. gr. subgranosus (Egger), (D) Ammonia ex. gr. beccarii (Linné), agglutinated foraminifera, (E,H) Ammotium sp. and planktonic foraminifera comprising Streptochilus sp. (I–J).
C. sp., Tyrrhenocythere ex. gr. motasi, Candoniella sp., and Zonocypris membranae (Fig. 3). The Portaferrian low-stand is determined magnetostratigraphically in the middle part of chron C3r, and precize ages can thus not be obtained here. Assuming constant sedimentation rates for the Râmnicu Sărat section results in interpolated ages of ∼5.8 and ∼5.5 Ma for the lower and upper Portaferrian boundary, respectively (Fig. 3). Seismic data from the western part of the Dacian Basin confirm a general regressive middle Pontian low-stand (Leever et al., 2009), while an erosional unconformity of regional significance has been observed between Maeotian and upper Pontian sediments at marginal regions (Stoica et al., 2007). The section at the Black Sea margin shows a conspicuous change at the top of this interval by deep lacustrine brackish marls with Pontian fauna indicative of the photic zone (b100 m deep) abruptly changing to condensed coastal sequences of reddish sands, with some minor sedimentary hiatuses, attributed to the base of the Kimmerian (Fig. 5). This red sequence comprises oolites/pisolites plus nodular marls that suggest high-energetic coastal environments (Fig. 5E). It furthermore contains molluscs that are characteristic of the Portaferrian (Fig. 5F–H) and minerals indicative of evaporitic conditions (selenite, gypsum and jarosite), which probably formed after deposition (Fig. 5I–L). This indicates that the Black Sea experienced a sea level drop of about 50– 100 m at the base of the Kimmerian (middle Portaferrian), which is
coeval to the intra-Pontian unconformities observed in seismic profiles of the Romanian Black Sea margin (Gillet et al., 2007). The Caspian Sea may have become isolated during this period, as suggested by the expansion of the deltaic systems of the ‘Productive Series’, which are Kimmerian in age. This is the main hydrocarbon reservoir unit of the South Caspian Basin, thought to represent the low-stand wedge of a dramatic sea level fall (Hinds et al., 2004). A tentative link has been made with the late Messinian eustatic sea level fall (Reynolds et al., 1998), but other studies have suggested a relation to large scale plate-tectonic processes (Allen et al., 2002). The base of the Productive Series is radiometrically dated at ∼ 5.5 Ma and is interpreted as the sudden southward expansion of the Miocene Volga delta resulting from a major regression (Dumont, 1998). Consequently, we conclude that all regions in the Eastern Paratethys show evidence for a marked sea level lowering of at least 50 m during the Messinian (5.6–5.5 Myr) time interval, corresponding to the Portaferrian of the Dacian Basin and the lowermost Kimmerian of the Black Sea and Caspian basins. 6. Paratethys transgression during the Bosphorian The upper Pontian (Bosphorian) corresponds to a second transgressive event in the Dacian Basin, showing a major faunal change in the
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Fig. 5. A) The reddish interval of the Zheleznyi Rog section. Portaferrian molluscs found in the marl interval below the red unit; B) Valenciennius sp., C) Paradacna abichi, D) Dreissena rostriformis. Characteristic mollusc species and the most relevant evaporitic minerals found in the reddish interval, marking the beginning of the Kimmerian: E) oolithic/pisolithic sandstone, F) Caladacna steindachneri, G) D. rostriformis, H) Pteradacna edentula, I) jarosite, J) prismatic gypsum crystals, K) jarosite, and L) radial gypsum. The corresponding levels are indicated right of the schematic lithological column.
ostracod assemblages (Fig. 3) and a lithological change to more basinal sequences (Jipa, 1997). The Portaferrian–Bosphorian transition is marked by a second bloom of ostracod fauna, and most Pontian species are well represented. Some species pass through the limit with lower Dacian (Getian substage). Interpolation assuming constant sedimentation rates, suggests that this upper Pontian transgression started at an age of 5.5 ± 0.1 Ma (Table 1). Detailed micropalaeontological studies have not revealed the presence of marine foraminifera here. In the western Dacian Basin, seismic profiles also show a transgressive system tract at the base of the Bosphorian (Leever et al., 2009). In the Topolog region of the south Carpathian foredeep, the Bosphorian is found transgressive on Maeotian deposits while the upper Maeotian and lower-middle Pontian are missing (Stoica et al., 2007). In addition, the bottom sets of a ‘Gilbert fan delta’ are correlated to this sea level rise (Clauzon et al., 2005), although stratigraphic data from Romanian geologists indicate that these fan deposits are of pre-Maeotian age (Savu and Ghenea, 1967; Nastaseanu and Bercia, 1968). In the Black Sea Basin, the Miocene–Pliocene boundary is commonly placed at the Pontian/Kimmerian boundary. This is in slight disagreement with our stratigraphic results, which shows that the red level of the lowermost Kimmerian corresponds to the Portaferrian of the Dacian
Basin and thus to the latest Miocene (Fig. 4). Faunal elements of Kimmerian marls, overlying the reddish interval at Zheleznyi Rog, are similar to the Bosphorian and can be largely attributed to the Pliocene. The “Productive Series” of the Caspian Basin are also biostratigraphically dated as Kimmerian in terms of Eastern Paratethyan chronostratigraphy (Nevesskaya et al., 2002). The numerical age is still a matter of debate, because of conflicting paleomagnetic evidence on which calibration to the global record is based, and because biostratigraphic control for interregional correlation is hindered by the presence of mostly local faunas and by massive reworking (Jones and Simmons, 1996). Our integrated stratigraphic results from the Dacian Basin show that the Pontian/Dacian boundary is younger than the Sidufjall normal chron (C3n.3n) and is magnetostratigraphically dated at ∼ 4.7 Ma (Fig. 3). This is significantly younger than presumed in other Paratethys time scales, where the Pontian–Dacian stage boundary is tentatively positioned at, or close to, the Miocene–Pliocene boundary (5.33 Ma) (Steininger et al., 1996; Clauzon et al., 2005; Snel et al., 2006). It is clear that different definitions have been used for the upper Pontian boundary in Romanian and Russian literature (Fig. 6; Table 1), which is especially problematic when working on the Mio– Pliocene sedimentary successions and seismic sequences of the Black Sea domain. A formal re-definition of the Paratethys regional stages according to international stratigraphic codes is urgently required.
Table 1 New magnetostratigraphic ages for the (sub)stage boundaries in the Dacian and Black Sea basins of the Eastern Paratethys.
7. Causes and consequences for the Messinian Salinity Crisis
Dacian Basin
Black Sea Basin
Boundary
Age (Ma)
Boundary
Age (Ma)
Pontian/Dacian Portaferrian/Bosphorian Odessian/Portaferrian Maeotian/Pontian
4.70 ± 0.05 5.5 ± 0.1 5.8 ± 0.1 6.04 ± 0.01
× Portaferrian/Kimmerian Novorossian/Portaferrian Maeotian/Pontian
× 5.6 ± 0.1 5.8 ± 0.1 6.04 ± 0.01
Our new chronological framework for the Eastern Paratethys allows high-resolution correlations with the oxygen isotope curves (Hodell et al., 2001; Hilgen et al., 2007) and the Messinian successions of the Mediterranean (Fig. 6). These are subdivided into three astronomically dated evaporite phases; M1) marine “Lower Gypsum” (5.96–5.6 Ma), M2) halite and resedimented evaporites (5.6–5.5 Ma), M3) Lago-Mare sediments with gypsum (5.5–5.3 Ma) (Krijgsman et al., 1999; Hilgen et al., 2007; Roveri et al., 2008).
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Fig. 6. A new chronology for the different local and regional stages of the Paratethys allows detailed correlations to the GTS, the Mediterranean event stratigraphy during the Messinian Salinity Crisis (M1–M3) (Krijgsman et al., 1999; Roveri et al., 2008) and to the oxygen isotope curves of the Atlantic margin of Morocco (Hilgen et al., 2007). Red star/ foraminifer indicates influx of marine nannofossils (Marunteanu and Papaianopol, 1998)/foraminifera (see Fig. 4). Schematic cross-sections show the changes in connectivity and the phases of basin isolation of the Paratethys and Mediterranean during the Messinian Salinity Crisis.
7.1. The onset of “Lower Gypsum” formation in the Mediterranean Our new data shows that the onset of the Messinian Salinity Crisis in the Mediterranean was directly preceded by the marine flooding of the Eastern Paratethys, confirming the hypothesis that the Lower Gypsum units formed during a relative high-stand of Mediterranean sea level (Flecker et al., 2002; Krijgsman and Meijer, 2008). A transgression at the onset of the Messinian evaporite formation is in serious contrast to hypotheses inferring glacio-eustatic sea level lowering (Hsü et al., 1973; Clauzon et al., 2005), but has earlier been suggested on the basis of strontium isotope models (Flecker et al., 2002; Flecker and Ellam, 2006). It is interesting to note that the bloom of Odessian ostracods (Fig. 3), indicating re-stabilization of paleoenvironmental conditions in the Paratethys, coincides with the onset of MSC evaporites at 5.96 Ma in the Mediterranean (Krijgsman et al., 1999). Consequently, the changes in Paratethys–Mediterranean connectivity at the Maeotian–Pontian transition interval probably generated a new hydrological equilibrium in both Paratethys and Mediterranean that allows gypsum to precipitate during astronomically-forced optimum (=dry) climate conditions on a precessional resolution in the Mediterranean Basin (Krijgsman et al., 2001). A flooding of the Paratethys basin could only have happened if its water level was significantly below global ocean and Mediterranean level. This indicates that the hydrological budget for the Paratethys region in Maeotian times was slightly negative. Establishing a Mediterranean–
Paratethys connection would result in an increased hydrological flux into the Paratethys and consequently an increase in water and salt flux from the Atlantic into the highly restricted evaporation-dominated Mediterranean. We speculate that creating a connection to the Paratethys will increase Mediterranean stratification and ultimately influence the hydrodynamics of the Gibraltar gateways, two crucial factors to explain the onset of widespread gypsum deposition during the MSC (Meijer and Krijgsman, 2005). 7.2. Location of Paratethys flooding Another intriguing question is: where did the Paratethys flooding actually come from? The Aegean region of the Mediterranean Sea is the most likely source area according to the paleogeographic reconstructions of the Paratethys domain (e.g. Popov et al., 2006), although we cannot exclude the Indian Ocean on the basis of our data. A flooding event is further expected to leave marked traces of significant erosion on land and offshore the Bosporus region (e.g. Loget et al. 2005). The Karadeniz-1 borehole in the European part of the Turkish Black Sea shelf indeed shows Messinian erosional surfaces (Gillet et al., 2007), which can possibly be traced to the Karacaköy region at the Black Sea margin northwest of Istanbul. We thus consider a Karacaköy–Karadeniz passage as potential candidate to account for the flooding event, but more detailed biostratigraphic data is necessary to confirm this hypothesis.
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7.3. Down drop of the sea level during the MSC The observed fall in Paratethyan water level at the base of the Portaferrian is estimated to have occurred at 5.8 Ma in the Dacian Basin (Fig. 3). This is remarkably close to glacial peaks TG22–20 (Fig. 6), which are suggested to have caused a significant drop in global sea level (Shackleton et al., 1995). In the Zheleznyi Rog succession this interval also shows evidence of sea level lowering, expressed by the occurrence of white shell beds of Portaferrian age (Po2: Popov et al., 2006). The climax of the Messinian Salinity Crisis occurred during glacial peaks TG12–14, when the water exchange with the Atlantic became restricted resulting in the formation of massive halite in the deepest parts of the Mediterranean and a dramatic fall in water level (Fig. 6). The potential connection to Paratethys thus also would have become lost, lowering the water level in the Black Sea Basin immediately to the level of the paleo-Bosphorus. Our data from Zheleznyi Rog suggest that this event is clearly reflected in the sharp transition to the reddish interval at the Russian Black Sea margin of the Taman Peninsula. The ultimate lake levels in the isolated Dacian, Black Sea and Caspian basins will obviously be influenced by astronomically induced changes of regional climate. Depending on the hydrological budget of the individual Paratethys basins desiccation (negative) or overflow (positive) will take place (Fig. 6). A marked change occurs in the oxygen isotope curves after TG12 at 5.5 Ma (Fig. 6), interpreted to result in much warmer and humid global climates (Hodell et al., 2001; Hilgen et al., 2007). This resulted in a positive hydrological change and caused widespread transgression of Lago-Mare/Upper Evaporite facies over the Messinian erosional surfaces (Lofi et al., 2005; Roveri et al., 2008). Transgressional sequences are especially clear in Northern Italy where they are attributed to an increased hydrological flux from the Alps (Willet et al., 2006). The timeequivalent transgression in the Paratethys can also be explained by these regional climatic changes. The alternative hypothesis for this transgression is the re-establishment of Paratethys–Mediterranean connectivity by the Zanclean deluge of the Mediterranean at the Miocene Pliocene boundary (5.33 Ma). This would better explain the sharp transition from littoral and fluvial Portaferrian facies to predominantly pelitic facies in the lower Bosphorian. The Bosphorian ostracod and mollusc fauna do not show evidence of significant freshening of the water conditions, although their strontium isotope ratios suggest isolation from the Mediterranean (Vasiliev, 2006). Mio–Pliocene connectivity at high sea level has earlier been suggested by Clauzon et al. (2005), but these authors based it on the nannofossil influxes in the Paratethys at the Pontian–Dacian boundary which are dated at 4.7 Ma and have thus no relation at all with the Pliocene flooding. We realize that a correlation to the Zanclean flooding cannot be excluded on the basis of our data. However, were the Paratethys transgression to be coeval with the Mediterranean flooding, substantial changes in sedimentation rate would be required, especially by a major (4×) increase in the lowermost part of the Bosphorian (below the Thvera). We have not seen any evidence for such an increase in the field, nor in the Râmnicu Sărat section (east Carpathian foredeep), nor in the Topolog region (south Carpathian foredeep). Future research should therefore aim at localizing marine influxes at the base of the Bosphorian and focus on geochemical proxies that may quantify Paratethys–Mediterranean connectivity. 8. Conclusions Our integrated stratigraphic data results in a robust chronological framework for the Dacian and Black Sea basins of the Eastern Paratethys (Table 1), allowing high-resolution stratigraphic correlations between the individual Paratethys subbasins and with the Messinian Salinity Crisis of the Mediterranean (Fig. 6). The Maeotian/Pontian boundary is dated at 6.04 Ma and corresponds to a major faunal change triggered by
a marine flooding of the Paratethys, as evidenced by the presence of planktonic foraminifera. The lowermost Pontian (Odessian/Novorossian) substage relates to a general high-stand in the Paratethys, possibly with interbasinal and Mediterranean connections. The onset of MSC evaporites closely coincides in age with the bloom of Odessian ostracods in the Paratethys at ∼5.95 Ma. The peak of the MSC at 5.6–5.5 Ma definitely ended Mediterranean–Paratethys connectivity in the Portaferrian, causing a sudden drawdown of Paratethys water levels of at least 50–100 m and isolating the Caspian Sea and the Dacian Basin from the Black Sea domain. From 5.5 Ma onward a major change in Eurasian climate, resulting in much warmer and humid conditions changed the hydrological balance and resulted in a widespread transgression in Mediterranean and Paratethys. The Miocene/Pliocene boundary may correspond to the Portaferrian/Bosphorian boundary in the Dacian Basin and to the top of the red layer in Zheleznyi Rog, i.e. within the lower Kimmerian of the Black Sea Basin, but certainly not to the Pontian/ Dacian boundary in the Dacian Basin, which is dated ∼600 kyr younger at 4.7 Ma. Our new stratigraphic framework has also serious consequences for the Mediterranean MSC. Ever since the discovery of widespread Messinian evaporites all over the Mediterranean seafloor, tectonic or glacio-eustatic processes restricting and closing the water exchange to the Atlantic in the west have been put forward and modeled to understand the causes of the Messinian Salinity Crisis (Hsü et al., 1973; Meijer and Krijgsman, 2005; Ryan, 2009), but conclusive answers are still lacking. Our data suggest that changing the connectivity to the Paratethys in the northeast could play an essential role in the onset of gypsum formation, which should give ample ammunition for new ideas and models concerning evaporite formation in semi-isolated basins. This will also have major implications for paleoceanographic circulation patterns, Mediterranean paleosalinity models and the internal stratification of its water column. Acknowledgements We thank Dan Jipa, Iulia Lazăr ar and Gheorghe Popescu for their help with sedimentological and biostratigraphical analyses of the Râmnicu Sărat data. Alexandr Iosifidi is acknowledged for skilful paleomagnetic sampling at Zheleznyi Rog. Cor Langereis, Frits Hilgen, Paul Meijer and Pasha Karami are thanked for discussions and useful comments on an earlier version of this manuscript. Rachel Flecker, Miguel Garcés and four anonymous EPSL reviewers are thanked for their constructive comments. Sergei Yudin and Vika Tomsha assisted with the paleomagnetic analyses. This study was performed under the inspiring leadership of Cor Langereis and Alexei Khramov, within the NWO program on Dutch–Russian cooperation. This work was financially supported by the Netherlands Research Centre for Integrated Solid Earth Sciences (ISES) and the Netherlands Geosciences Foundation (ALW) with support from the Netherlands Organization for Scientific Research (NWO). References Aksu, A.E., Hiscott, R.N., Yasar, D., Isler, F.I., Marsh, S., 2002. Seismic stratigraphy of Late Quaternary deposits from the southwestern Black Sea shelf: evidence for noncatastrophic variations in sea-level during the last 10000 yr. Mar. Geol. 190, 61–94. Allen, M.B., Jones, S., Ismail-Zadeh, A.D., Simmons, M.D., Anderson, L., 2002. Onset of subduction as the cause of rapid Pliocene/Quaternary subsidence in the South Caspian basin. Geology 30, 775–778. Çagatay, M.N., et al., 2006. Paratethyan–Mediterranean connectivity in the Sea of Marmara region (NW Turkey) during the Messinian. Sediment. Geol. 188–189, 171–187. Chumakov, L.S., et al., 1992. Interlaboratory fission track dating of volcanic ash levels from eastern Paratethys: a Mediterranean–Paratethys correlation. Palaeogeogr. Palaeoclimatol. Palaeoecol. 24, 287–295. Cita, M.B., Wright, R.C., Ryan, W.B.F., Longinelli, A., 1978. Messinian paleoenvironments. In: Hsü, K.J. (Ed.), Initial Reports of the Deep Sea Drilling Project, pp. 1003–1035. Clauzon, G., et al., 2005. Influence of Mediterranean sea-level changes on the Dacic Basin (Eastern Paratethys) during the late Neogene: the Mediterranean Lago Mare facies deciphered. Basin Res. 17, 437–462. Dinu, C., Wong, H.K., Tambrea, D., Matenco, L., 2005. Stratigraphic and structural characteristics of the Romanian Black Sea shelf. Tectonophysics 410, 417–435.
W. Krijgsman et al. / Earth and Planetary Science Letters 290 (2010) 183–191 Dumont, H.J., 1998. The Caspian Lake: history, biota, structure, and function. Limnol. Oceanogr. 43, 44–52. Filippova, N.Y., 2002. Spores, pollen, and organic-walled Phytoplankton from neogene deposits of the Zheleznyi Rog reference section (Taman Peninsula). Strat. Geol. Correlat. 10, 176–188. Flecker, R., Ellam, R.M., 2006. Identifying Late Miocene episodes of connection and isolation in the Mediterranean–Paratethyan realm using Sr isotopes. Sediment. Geol. 188–189, 189–203. Flecker, R., de Villiers, S., Ellam, R.M., 2002. Modelling the effect of evaporation on the salinity −87Sr/86Sr relationship in modern and ancient marginal-marine systems: the Mediterranean Messinian salinity crisis. Earth Planet. Sci. Lett. 203, 221–233. Gillet, H., Lericolais, G., Rehault, J.-P., 2007. Messinian event in the Black Sea: evidence of a Messinian erosional surface. Mar. Geol. 244, 142–165. Hallam, A., Wignall, P.B., 1997. Mass Extinctions and their Aftermath. Oxford University Press, Oxford. 320 pp. Hilgen, F.J., Kuiper, K.F., Krijgsman, W., Snel, E., Van der Laan, E., 2007. Astronomical tuning as the basis for high resolution chronostratigraphy: the intricate history of the Messinian salinity crisis. Stratigraphy 2007, 231–238. Hinds, D.J., et al., 2004. Sedimentation in a discharge dominated fluvial/lacustrine system: the Neogene Productive Series of the South Caspian Basin, Azerbaijan. Mar. Petrol. Geol. 21, 613–638. Hodell, D.A., Curtis, J.H., Sierro, F.J., Raymo, M.E., 2001. Correlation of late Miocene to early Pliocene sequences between the Mediterranean and North Atlantic. Paleoceanography 16, 164–178. Hsü, K.J., Giovanoli, F., 1979. Messinian event in the Black Sea. Palaeogeogr. Palaeoclimatol. Palaeoecol. 29, 75–93. Hsü, K.J., Ryan, W.B.F., Cita, M.B., 1973. Late Miocene desiccation of the Mediterranean. Nature 242, 240–244. Jipa, D., 1997. Late Neogene–Quaternary evolution of Dacian basin (Romanian). An analysis of sediment thickness pattern. Geo-Eco-Marina 2, 127–134. Jones, R.W., Simmons, M.D., 1996. A review of the stratigraphy of eastern Paratethys (Oligocene–Holocene). Bull. Nat. Hist. Museum (Geol. Suppl.) 52, 25–49. Krijgsman, W., Meijer, P.T., 2008. Depositional environments of the Mediterranean “Lower Evaporites” of the Messinian salinity crisis: constraints from quantitative analyses. Mar. Geol. 253, 73–81. doi:10.1016/j.margeo.2008.04.010. Krijgsman, W., Hilgen, F.J., Raffi, I., Sierro, F.J., Wilson, D.S., 1999. Chronology, causes and progression of the Messinian salinity crisis. Nature 400, 652–655. Krijgsman, W., Fortuin, A.R., Hilgen, F.J., Sierro, F.J., 2001. Astrochronology for the Messinian Sorbas Basin (SE Spain) and orbital (precessional) forcing for evaporite cyclicity. Sediment. Geol. 140, 43–60. Leever, K.A., 2007. Foreland of the Romanian Carpathians: controls on late orogenic sedimentary basin evolution and Paratethys paleogeography, PhD thesis, VU University Amsterdam, Amsterdam, 182 pp. Leever, K.A., et al., 2009. Messinian sea level fall in the Dacic Basin (Eastern Paratethys): palaeogeographical implications from seismic sequence stratigraphy. Terra Nova. doi:10.1111/j.1365-3121.2009.00910.x. Lofi, J., et al., 2005. Erosional processes and paleo-environmental changes in the Western Gulf of Lions (SW France) during the Messinian salinity crisis. Mar. Geol. 217, 1–30. Loget, N., Van Den Driessche, J., Davy, P., 2005. How did the Messinian salinity crisis end. Terra Nova 17, 414–419. Magyar, I., Sztanó, O., 2008. Is there a Messinian unconformity in the Central Paratethys? Stratigraphy 5, 245–255. Marunteanu, M., Papaianopol, I., 1998. Mediterranean nannoplankton in the Dacic basin. Rom. J. Stratigraphy 78, 115–121. Meijer, P.T., Krijgsman, W., 2005. A quantitative analysis of the desiccation and re-filling of the Mediterranean during the Messinian salinity crisis. Earth Planet. Sci. Lett. 240, 510–520. Nastaseanu, S., Bercia, I., 1968. Baia de Arama. : Carte géologique de Roumanie au 1/ 200.000, vol. 32. Institut géologique, Bucharest.
191
Nevesskaya, L.A., Goncharova, I.A., Ilyina, L.B., Paramonova, N.P., Khondkarian, S.O., 2002. The Neogene stratigraphic scale of the Eastern Paratethys. Strat. Geol. Correlat. 11, 105–127. Panaiotu, C.E., Vasiliev, I., Panaiotu, C.G., Krijgsman, W., Langereis, C.G., 2007. Provenance analysis as a key to orogenic exhumation: a case study from the East Carpathians (Romania). Terra Nova 19, 120–126. Pevzner, M.A., Semenenko, V.N., Vangengeim, E.A., 2003. Position of the Pontian of the Eastern Paratethys in the Magnetochronological Scale. Strat. Geol. Correlat. 11, 482–491. Popov, S.V., et al., 2006. Late Miocene to Pliocene papaeogeography of the Paratethys and its relation to the Mediterranean. Palaeogeogr. Palaeoclimatol. Palaeoecol. 238, 91–106. Reynolds, A.D., et al., 1998. Implications of outcrop geology for reservoirs in the Neogene Productive Series: Apsheron Peninsula, Azerbaijan. AAPG Bull. 82, 25–49. Roveri, M., Lugli, S., Manzi, V., Schreiber, B.C., 2008. The Messinian Sicilian stratigraphy revisited: new insights for the Messinian salinity crisis. Terra Nova 20, 483–488. Ryan, W.B.F., 2009. Decoding the Mediterranean Salinity Crisis. Sedimentology 56, 95–136. Ryan, W.B.F., Pitman, W.C., 1998. Noah's Flood: the New Scientific Discoveries About the Event that Changed History. Simon & Schuster, p. 319. Ryan, W.B.F., et al., 1997. An abrupt drowning of the Black Sea shelf. Mar. Geol. 138, 119–126. Ryan, W.B.F., Major, C.O., Lericolais, G., Goldstein, S.L., 2003. Catastrophic flooding of the Black Sea. Annu. Rev. Earth Planet. Sci. 31, 525–554. doi:10.1146/annurev. earth.31.100901.141249. Savu, H., Ghenea, C., 1967. Turnu Severin. : Carte géologique de Roumanie au 1/200.000, vol. 40. Institut géologique, Bucharest. Semenenko, V.N., 1979. Correlation of Mio–Pliocene of the Eastern Paratethys and Tethys. VII th International Congress on Mediterranean Neogene: Athens, pp. 1101–1111. Shackleton, N.J., Crowhurst, S., Hagelberg, T., Pisias, N.G., Schneider, D.A., 1995. A new Late Neogene time scale: application to leg 138 sites. Proc. ODP Sci. Results 138, 73–101. Snel, E., Marunteanu, M., Macalet, R., Meulenkamp, J.E., van Vugt, N., 2006. Late Miocene to Early Pliocene chronostratigraphic framework for the Dacic Basin, Romania. Palaeogeogr. Palaeoclimatol. Palaeoecol. 238 (1–4), 107–124. Steininger, F.F., et al., 1996. Circum-Mediterranean Neogene (Miocene and Pliocene) marine-continental chronologic correlations of European mammal units. In: Bernor, R.L., Fahlbusch, V., Mittmann, H.-W. (Eds.), The Evolution of Western Eurasian Neogene Mammal Faunas. Columbia Univ. Press, New York, pp. 7–46. Stevanovic, P., Nevesskaya, L.A., Marinescu, F., Sokac, A., Jámbor, A., 1989. Chronostratigraphie und Neostratotypen: Pliozän Pl1. Pontien. JAZU & SANU, Zagreb-Beograd. 952 pp. Stoica, M., Lazar, I., Vasiliev, I., Krijgsman, W., 2007. Mollusc assemblages of the Pontian and Dacian deposits from the Topolog-Arges area (southern Carpathian foredeep — Romania). Geobios 40, 391–405. Trubikhin, V.M., 1986. Neogene magnetostratigraphic scale of the Eastern Paratethys. III conference of Geomagnetism, Kiev, pp. 206–207. Vasiliev, I. 2006. A new chronology for the Dacian Basin (Romania). PhD Thesis Utrecht University, Geologica Ultraiectina, 267, pp 191. Vasiliev, I., et al., 2004. Towards an astrochronological framework for the eastern Paratethys Mio–Pliocene sedimentary sequences of the Focşani basin (Romania). Earth Planet. Sci. Lett. 227, 231–247. Vasiliev, I., Krijgsman, W., Stoica, M., Langereis, C.G., 2005. Mio–Pliocene magnetostratigraphy in the southern Carpathian foredeep and Mediterranean–Paratethys correlations. Terra Nova 17, 376–384. Vasiliev, I., et al., 2007. Early diagenetic greigite as a recorder of the palaeomagnetic signal in Miocene–Pliocene sedimentary rocks of the Carpathian foredeep (Romania). Geophys. J. Int. 171, 613–629. Vasiliev, I., et al., 2008. Putative greigite magnetofossils from the Pliocene epoch. Nat. Geosci. 1, 782–786. doi:10.1038/ngeo335. Willet, S.D., Schlunegger, F., Picotti, V., 2006. Messinian climate change and erosional destruction of the central European Alps. Geology 34 (8), 613–616. doi:10.1130/ G22280.1.
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Earth and Planetary Science Letters j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / e p s l
Rise and fall of the Paratethys Sea during the Messinian Salinity Crisis W. Krijgsman a,⁎, M. Stoica b, I. Vasiliev a, V.V. Popov c a b c
Paleomagnetic Laboratory ‘Fort Hoofddijk’, Utrecht University, Budapestlaan 17, 3584 CD, Utrecht, The Netherlands Department of Palaeontology, Faculty of Geology and Geophysics, University of Bucharest, Bălcescu Bd. 1, 010041, Romania VNIGRI, All-Russia Petroleum Research Exploration Institute, St. Petersburg, Russia
a r t i c l e
i n f o
Article history: Received 9 July 2009 Received in revised form 16 November 2009 Accepted 8 December 2009 Available online 3 January 2010 Editor: P. DeMenocal Keywords: Paratethys Mediterranean Messinian Salinity Crisis magnetostratigraphy flooding sea level change
a b s t r a c t Extremely thick evaporite units were deposited during the so-called Messinian Salinity Crisis (MSC: 5.96– 5.33 Ma) in a deep Mediterranean basin that was progressively disconnected from the Atlantic Ocean. A crucial, but still poorly understood component in Messinian evaporite models is the connectivity between Mediterranean and Paratethys, i.e. the former Black Sea domain. Inadequate stratigraphic correlations and insufficient age control for Paratethys sediments have so far hampered a thorough understanding of hydrological fluxes and paleoenvironmental changes. Here, we present a new chronology for the Eastern Paratethys by integrating biostratigraphic and paleomagnetic data from Mio–Pliocene sedimentary successions of Romania and Russia. We show that a major flooding event from the Mediterranean surged the Paratethys basins at the Maeotian–Pontian boundary, 6.04 million years ago. This indicates that sea level in both Mediterranean and Paratethys was high at the beginning of the MSC. We argue in favor of changes in Paratethys–Mediterranean connectivity to initiate the MSC in combination with elusive tectonic processes in the Gibraltar arc. A subsequent fall of Paratethyan water level closely coincides to the Mediterranean isolation-event, corresponding in age to the glacial cycles TG12–14 (5.60–5.50 Myr). In the latest Messinian, a major climate change towards more humid conditions produced a positive hydrological balance and likely a transgression in the Paratethys, although our stratigraphic resolution cannot exclude a possible relation to the Pliocene flooding of the Mediterranean here. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Major sea level fluctuations, causing dramatic paleoenvironmental changes and related mass-extinctions, form an intricate part of Earth history (Hallam and Wignall, 1997). Renowned examples are the biblical flood of Noah and the Messinian Salinity Crisis (MSC) of the Mediterranean. Geological investigations indicated that a great deluge surged the Black Sea basin roughly 8000 years ago, rapidly raising the lake level by some 100 m (Ryan et al., 1997, 2003) so that civilizations and populations inhabiting the Black Sea shores may have suddenly drowned (Ryan and Pitman, 1998). The sudden influx hypothesis is highly debated between geologists and archeologists (Aksu et al., 2002), but may also have occurred in late Messinian times (Hsü and Giovanoli, 1979) when the Black Sea domain was part of the Eastern Paratethys (Fig. 1). During the Messinian (7.24–5.33 Ma), the Mediterranean became progressively isolated from the Atlantic Ocean, triggering widespread precipitation of gypsum (5.96–5.6 Ma), massive salt deposition (5.6–5.5 Ma), and a dramatic sea level lowering followed by brackish water environments of “Lago-Mare” (Lake Sea) facies (e.g. Hilgen et al., 2007; Krijgsman and Meijer, 2008; Roveri et al., 2008). A catastrophic re-flooding from the Atlantic at the beginning of the
⁎ Corresponding author. Tel.: +31 30 2531672. E-mail address: [email protected] (W. Krijgsman). 0012-821X/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.epsl.2009.12.020
Pliocene (5.33 Ma) abruptly ended the salinity crisis by re-establishing open marine conditions in the Mediterranean (Hsü et al., 1973). The hydrological flux from Paratethys to Mediterranean is a crucial component in quantitative studies on paleocirculation patterns and precipitation models of evaporites (Meijer and Krijgsman, 2005; Flecker and Ellam, 2006), but connectivity between the two basins is controversial (Çagatay et al., 2006). Overspilling of Paratethys waters into the Mediterranean has been argued to explain the presence of brackish water fauna in the Lago-Mare sediments (Cita et al., 1978), but a lowering of Paratethys levels during the Messinian event is also suggested (Hsü and Giovanoli, 1979). Seismic profiles of the Black Sea basin show evidence of deep canyon cutting, but the exact stratigraphic position differs; at the base of the Pontian Stage (Dinu et al., 2005) or intra-Pontian (Gillet et al., 2007). Sequence stratigraphic interpretations on a seismic transect from the western Dacian Basin also reveal significant sea level changes within the Pontian Stage (Leever et al., 2009). Seismic and borehole data from the Pannonian Basin show unconformities as well, but these are interpreted to have a regional tectonic origin and no relation to Messinian drawdown (Magyar and Sztanó, 2008). A concurrent base level drop has been proposed for the Caspian Sea (Reynolds et al., 1998; Popov et al., 2006), although numerical ages are poorly defined. Paratethys time scales comprise regional stages (e.g. Maeotian– Pontian–Dacian or Kimmerian within the Mio–Pliocene interval) and substages (e.g. Odessian–Portaferrian–Bosphorian within the Pontian)
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Fig. 1. Paleogeographic map of the Mediterranean and Paratethys during the Messinian Salinity Crisis interval. Stars indicate locations of the sections and research areas. In the Dacian Basin, RS and PU = Râmnicu Sarat and Putna sections are located in the east Carpathian foredeep and TP = Topolog region is in the south Carpathian foredeep. In the Black Sea basin, ZR = Zheleznyi Rog section is located on the Taman Peninsula of the Russian Black Sea margin; SC = South Caspian Basin — Azerbaijan. Triangles locate astronomically dated Mediterranean MSC sections (see Hilgen et al. (2007) and Krijgsman and Meijer (2008) for details).
based on endemic ostracod and mollusc species. At present, correlations to the marine record are mainly tentatively based on rare incursions of nannofossils (e.g. Marunteanu and Papaianopol, 1998) and chronostratigraphic resolution is generally inadequate to determine causal relationships with the Mediterranean MSC events. Here, we construct a robust biochronologic framework for the Paratethys domain by integrating paleomagnetic data with detailed paleontologic analyses of endemic Paratethys faunal (molluscs and ostracods) assemblages from sections of the Dacian and the Black Sea basin (Fig. 1). The integrated stratigraphic results of these individual domains will unfold the intrinsic paleoenvironmental evolution of the Eastern Paratethys during the Messinian Salinity Crisis with revised chronologic constraints.
successions covering the MSC interval, and integrate the results with the magnetostratigraphic data (Vasiliev et al., 2004, 2007). The target section in the Black Sea Basin is on Taman Peninsula (Russia); the classic Zheleznyi Rog (Iron Cape) section is 500 m long and covers ∼ 5 Myr of sediments (Fig. 1). The section has been extensively studied by several Russian research teams (Semenenko, 1979; Trubikhin, 1986; Filippova, 2002), but despite the presence of paleontological, paleomagnetic and (K–Ar) isotopic data, correlations to the GTS are still highly debated (Chumakov et al., 1992; Pevzner et al., 2003; Popov et al., 2006). We have focused here on the Mio– Pliocene interval of the Zheleznyi Rog section and resampled the uppermost Maeotian, Pontian and the lower Kimmerian for paleomagnetic and biostratigraphic purposes to establish direct correlations to the integrated stratigraphic record in the Dacian Basin.
2. Sections and setting
3. Paleomagnetic results
Paleomagnetic studies recently showed that excellent biochronological control for the Paratethys can be obtained from continuous sedimentary sequences (Vasiliev et al., 2004, 2005). The Dacian Basin in particular comprises several complete and well-exposed sedimentary successions from the Pontian Stage, consisting of fossiliferous silts and sands indicative of lacustrine and fluvio-deltaic environment (Panaiotu et al., 2007). These sediments accumulated rapidly in a foredeep setting, providing a thick continuous exposure of the MSC interval (Vasiliev et al., 2004). The Râmnicu Sărat and Putna sections (Fig. 1) were shown to carry a primary magnetic signal produced by greigite magnetofossils, providing reliable records of ancient geomagnetic field variations (Vasiliev et al., 2008) thus allowing excellent correlations to the standard Geological Time Scale (GTS) and to magnetostratigraphically dated sections in the south Carpathian foredeep (Fig. 1; Vasiliev et al., 2005). It showed that the major paleoenvironmental changes in the late Miocene and Pliocene were synchronous within the Dacian Basin, although these magnetostratigraphic studies were lacking direct biostratigraphic control. Here we present a detailed ostracod biostratigraphy for the Râmnicu Sărat section in the east Carpathian foredeep, one of the most continuous
Standard paleomagnetic measurements have been performed to establish a new magnetostratigraphic record for the Zheleznyi Rog section (Fig. 2). Thermal (TH) demagnetization was applied with small temperature increments of 10–30 °C up to a maximum temperature of 580 °C in a magnetically shielded furnace. Alternating Field (AF) demagnetization was performed with small field increments, up to a maximum of 100 mT, using an in-house built robotized sample handler controller attached to a horizontal 2G Enterprises DC SQUID cryogenic magnetometer. Demagnetization results were analyzed using orthogonal plots and stereographic projections. The direction of the NRM components was calculated by principalcomponent analysis. Dual polarity components were isolated in most samples between the 270–420 °C (Fig. 2A–C) or 20–45 mT demagnetization steps (Fig. 2D,E). Several specimens were demagnetized up to 580 °C or 100 mT (Fig. 2F). We recognized three polarity intervals in the studied succession, normal polarities at the basal (upper Maeotian) part, reversed polarity in the middle (Pontian) part and normal polarity in the upper (lower Kimmerian) part. An alternating gradient magnetometer (Princeton Measurements Corporation, MicroMag Model 2900 with 2T magnet, noise
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Fig. 2. Demagnetization results from the Zheleznyi Rog section. In the Zijderveld plots (A–F), red numbers represent the temperature steps in °C for the TH demagnetization (A–C,F), and blue numbers indicate the field steps in mT for AF demagnetization (D–E). Down-right are the stratigraphic levels in meters. The diagrams are presented with tectonic tilt correction (th/tc or af/tc). The red (blue) lines indicate the ChRM direction from the TH (AF) demagnetization. The red circles and the blue diamonds are the symbols used in Fig. 4. Representative first order reversal curves diagrams (G, H) have contours closing around a single domain (SD) peak at Bc = 40–50 mT, indicative for greigite as magnetic carrier.
level 2 × 10− 9 Am2) was used to measure first order reversal curves (FORC) diagrams. The domain state, and particularly the amount of magnetic interaction emerges clearly from FORC diagrams. Contours closing around a single domain (SD) peak at Bc = 40–50 mT (Fig. 2G,H) are similar to those previously reported for greigite in the Dacian Basin (Vasiliev et al., 2007). 4. Rise in Paratethyan water level at the Maeotian/Pontian boundary The Paratethyan ostracod distribution in Mio–Pliocene times reflects evolutionary trends, but also the influence of paleoenvironmental changes. Changing the connectivity with the open ocean influences the bathymetry and salinity of Paratethyan basins, which is reflected in the marginal faunal assemblages of the Dacian Basin. We present here the results of a detailed micro-paleontological study, focussing mainly on ostracods and foraminifera of the Râmnicu Sărat section, which provides a high-resolution biochronology for the Eastern Paratethys (Fig. 3). Our biostratigraphic results show that the fossil ostracod assemblages from the upper Maeotian (Moldavian substage) comprise a low number of species, of which Cyprideis pannonica is common and Paracandona albicans and Leptocythere blanda are rare (Fig. 3). These fossil assemblages are indicative of sub-littoral fresh- to brackish water environment, suggesting that the upper Maeotian sediments in the east Carpathian foredeep are associated with temporary lakes on flood plain areas. The marginal areas of the Dacian Basin thus evolved in almost freshwater conditions, while the paleoenvironment was dominated by littoral and fluvial conditions. The Maeotian assemblages are rapidly replaced by lower Pontian (Odessian/Novorossian) associations (Fig. 3). The lower Pontian ostracod assemblages indicate relatively deep basinal environments, and a widespread rise of relative sea level. At this time, characteristic layers formed comprising monospecific Congeria novorossica molluscs (Stevanovic et al., 1989). Our detailed study of the Maeotian–Pontian transition interval, for the first time, reveals the presence of
agglutinated and calcareous benthic foraminifera and planktonic foraminifera (Streptochilus and Tenuitellina species) of marine origin in the Upper Miocene of the Eastern Paratethys (Fig. 4A–J). This indicates that a major marine deluge took place by re-establishing a connection through the Mediterranean to the Atlantic, or alternatively to the Indian Ocean. Magnetostratigraphic results show that this flooding interval occurred synchronously in the Dacian and Black Sea basins near the paleomagnetic reversal C3An.2n(y), and is dated at 6.04 Ma (Fig. 4). The marine environment in the Eastern Paratethys was only a short-lived feature of maximum 10 kyr, after which micropaleontological assemblages are again dominated by ostracods indicative of brackish water conditions. After this transgressive interval, the lower Pontian ostracod fauna reacted to the changes in bathymetry and salinity, while variations in interbasinal connectivity allowed migration of species. It generated a “bloom” of ostracod species in the Odessian at ∼5.95 Ma (Fig. 3), especially in the predominantly pelitic deposits that are well-developed in lower Pontian times. A transgression at the Maeotian/Pontian boundary has previously been documented from wells and seismics in the western Dacian Basin (Jipa, 1997; Leever, 2007; Leever et al., 2009) and is biostratigraphically marked by a migration of faunal elements from the Pannonian basin (Hungary–Austria) into the Eastern Paratethys and by migration of typical Aegean species into the Black Sea domain. This is supported by earlier observations of a short calcareous nannofossil influx at the Maeotian/Pontian boundary interval (Marunteanu and Papaianopol, 1998). Biostratigraphic data from the Caspian Basin in Azerbaijan reveal similar changes in faunal elements indicating that this event extended into western Asia (Stevanovic et al., 1989). 5. Fall in Paratethyan water level during the Portaferrian A marked paleoenvironmental change occurs at the middle Pontian (Portaferrian) of the Dacian Basin. The study region in Romania shows a transition to more sandy facies, with ample presence of wave rippled
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Fig. 3. Ostracod distribution of the Râmnicu Sărat section in the east Carpathian foredeep of the Dacian Basin. The magnetostratigraphic pattern is after Vasiliev et al. (2004) and correlates excellently to the GTS. It allows high-resolution dating of the ostracod assemblages and related stages and substages. The resulting new ages of the (sub)stage boundaries are indicated.
sediments indicating deposition in shallow water, probably on the lower shore face (Panaiotu et al., 2007). The Portaferrian thus represents a regressive event where the bathymetry of the Dacian
Basin decreased. In marginal settings, the rich Odessian ostracod fauna indicative of basinal conditions is replaced by littoral, fluvial and lacustrine Portaferrian species: Amplocypris dorsobrevis, C. pannonica,
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Fig. 4. Detailed integrated stratigraphic data of the Maeotian/Pontian interval. Pontian–Kimmerian are regional stages of the Black Sea Basin. Magnetostratigraphic data from Râmnicu Sărat are after Vasiliev et al. (2004), from Zheleznyi Rog of this paper. Red circles represent reliable directions from thermal demagnetization, whereby small circles denote greigite, large circles magnetite. The blue diamonds indicate directions from alternating field demagnetization .The Maeotian–Pontian boundary interval is marked by a short influx of marine calcareous benthic foraminifera (A–C) Porosononian ex. gr. subgranosus (Egger), (D) Ammonia ex. gr. beccarii (Linné), agglutinated foraminifera, (E,H) Ammotium sp. and planktonic foraminifera comprising Streptochilus sp. (I–J).
C. sp., Tyrrhenocythere ex. gr. motasi, Candoniella sp., and Zonocypris membranae (Fig. 3). The Portaferrian low-stand is determined magnetostratigraphically in the middle part of chron C3r, and precize ages can thus not be obtained here. Assuming constant sedimentation rates for the Râmnicu Sărat section results in interpolated ages of ∼5.8 and ∼5.5 Ma for the lower and upper Portaferrian boundary, respectively (Fig. 3). Seismic data from the western part of the Dacian Basin confirm a general regressive middle Pontian low-stand (Leever et al., 2009), while an erosional unconformity of regional significance has been observed between Maeotian and upper Pontian sediments at marginal regions (Stoica et al., 2007). The section at the Black Sea margin shows a conspicuous change at the top of this interval by deep lacustrine brackish marls with Pontian fauna indicative of the photic zone (b100 m deep) abruptly changing to condensed coastal sequences of reddish sands, with some minor sedimentary hiatuses, attributed to the base of the Kimmerian (Fig. 5). This red sequence comprises oolites/pisolites plus nodular marls that suggest high-energetic coastal environments (Fig. 5E). It furthermore contains molluscs that are characteristic of the Portaferrian (Fig. 5F–H) and minerals indicative of evaporitic conditions (selenite, gypsum and jarosite), which probably formed after deposition (Fig. 5I–L). This indicates that the Black Sea experienced a sea level drop of about 50– 100 m at the base of the Kimmerian (middle Portaferrian), which is
coeval to the intra-Pontian unconformities observed in seismic profiles of the Romanian Black Sea margin (Gillet et al., 2007). The Caspian Sea may have become isolated during this period, as suggested by the expansion of the deltaic systems of the ‘Productive Series’, which are Kimmerian in age. This is the main hydrocarbon reservoir unit of the South Caspian Basin, thought to represent the low-stand wedge of a dramatic sea level fall (Hinds et al., 2004). A tentative link has been made with the late Messinian eustatic sea level fall (Reynolds et al., 1998), but other studies have suggested a relation to large scale plate-tectonic processes (Allen et al., 2002). The base of the Productive Series is radiometrically dated at ∼ 5.5 Ma and is interpreted as the sudden southward expansion of the Miocene Volga delta resulting from a major regression (Dumont, 1998). Consequently, we conclude that all regions in the Eastern Paratethys show evidence for a marked sea level lowering of at least 50 m during the Messinian (5.6–5.5 Myr) time interval, corresponding to the Portaferrian of the Dacian Basin and the lowermost Kimmerian of the Black Sea and Caspian basins. 6. Paratethys transgression during the Bosphorian The upper Pontian (Bosphorian) corresponds to a second transgressive event in the Dacian Basin, showing a major faunal change in the
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Fig. 5. A) The reddish interval of the Zheleznyi Rog section. Portaferrian molluscs found in the marl interval below the red unit; B) Valenciennius sp., C) Paradacna abichi, D) Dreissena rostriformis. Characteristic mollusc species and the most relevant evaporitic minerals found in the reddish interval, marking the beginning of the Kimmerian: E) oolithic/pisolithic sandstone, F) Caladacna steindachneri, G) D. rostriformis, H) Pteradacna edentula, I) jarosite, J) prismatic gypsum crystals, K) jarosite, and L) radial gypsum. The corresponding levels are indicated right of the schematic lithological column.
ostracod assemblages (Fig. 3) and a lithological change to more basinal sequences (Jipa, 1997). The Portaferrian–Bosphorian transition is marked by a second bloom of ostracod fauna, and most Pontian species are well represented. Some species pass through the limit with lower Dacian (Getian substage). Interpolation assuming constant sedimentation rates, suggests that this upper Pontian transgression started at an age of 5.5 ± 0.1 Ma (Table 1). Detailed micropalaeontological studies have not revealed the presence of marine foraminifera here. In the western Dacian Basin, seismic profiles also show a transgressive system tract at the base of the Bosphorian (Leever et al., 2009). In the Topolog region of the south Carpathian foredeep, the Bosphorian is found transgressive on Maeotian deposits while the upper Maeotian and lower-middle Pontian are missing (Stoica et al., 2007). In addition, the bottom sets of a ‘Gilbert fan delta’ are correlated to this sea level rise (Clauzon et al., 2005), although stratigraphic data from Romanian geologists indicate that these fan deposits are of pre-Maeotian age (Savu and Ghenea, 1967; Nastaseanu and Bercia, 1968). In the Black Sea Basin, the Miocene–Pliocene boundary is commonly placed at the Pontian/Kimmerian boundary. This is in slight disagreement with our stratigraphic results, which shows that the red level of the lowermost Kimmerian corresponds to the Portaferrian of the Dacian
Basin and thus to the latest Miocene (Fig. 4). Faunal elements of Kimmerian marls, overlying the reddish interval at Zheleznyi Rog, are similar to the Bosphorian and can be largely attributed to the Pliocene. The “Productive Series” of the Caspian Basin are also biostratigraphically dated as Kimmerian in terms of Eastern Paratethyan chronostratigraphy (Nevesskaya et al., 2002). The numerical age is still a matter of debate, because of conflicting paleomagnetic evidence on which calibration to the global record is based, and because biostratigraphic control for interregional correlation is hindered by the presence of mostly local faunas and by massive reworking (Jones and Simmons, 1996). Our integrated stratigraphic results from the Dacian Basin show that the Pontian/Dacian boundary is younger than the Sidufjall normal chron (C3n.3n) and is magnetostratigraphically dated at ∼ 4.7 Ma (Fig. 3). This is significantly younger than presumed in other Paratethys time scales, where the Pontian–Dacian stage boundary is tentatively positioned at, or close to, the Miocene–Pliocene boundary (5.33 Ma) (Steininger et al., 1996; Clauzon et al., 2005; Snel et al., 2006). It is clear that different definitions have been used for the upper Pontian boundary in Romanian and Russian literature (Fig. 6; Table 1), which is especially problematic when working on the Mio– Pliocene sedimentary successions and seismic sequences of the Black Sea domain. A formal re-definition of the Paratethys regional stages according to international stratigraphic codes is urgently required.
Table 1 New magnetostratigraphic ages for the (sub)stage boundaries in the Dacian and Black Sea basins of the Eastern Paratethys.
7. Causes and consequences for the Messinian Salinity Crisis
Dacian Basin
Black Sea Basin
Boundary
Age (Ma)
Boundary
Age (Ma)
Pontian/Dacian Portaferrian/Bosphorian Odessian/Portaferrian Maeotian/Pontian
4.70 ± 0.05 5.5 ± 0.1 5.8 ± 0.1 6.04 ± 0.01
× Portaferrian/Kimmerian Novorossian/Portaferrian Maeotian/Pontian
× 5.6 ± 0.1 5.8 ± 0.1 6.04 ± 0.01
Our new chronological framework for the Eastern Paratethys allows high-resolution correlations with the oxygen isotope curves (Hodell et al., 2001; Hilgen et al., 2007) and the Messinian successions of the Mediterranean (Fig. 6). These are subdivided into three astronomically dated evaporite phases; M1) marine “Lower Gypsum” (5.96–5.6 Ma), M2) halite and resedimented evaporites (5.6–5.5 Ma), M3) Lago-Mare sediments with gypsum (5.5–5.3 Ma) (Krijgsman et al., 1999; Hilgen et al., 2007; Roveri et al., 2008).
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Fig. 6. A new chronology for the different local and regional stages of the Paratethys allows detailed correlations to the GTS, the Mediterranean event stratigraphy during the Messinian Salinity Crisis (M1–M3) (Krijgsman et al., 1999; Roveri et al., 2008) and to the oxygen isotope curves of the Atlantic margin of Morocco (Hilgen et al., 2007). Red star/ foraminifer indicates influx of marine nannofossils (Marunteanu and Papaianopol, 1998)/foraminifera (see Fig. 4). Schematic cross-sections show the changes in connectivity and the phases of basin isolation of the Paratethys and Mediterranean during the Messinian Salinity Crisis.
7.1. The onset of “Lower Gypsum” formation in the Mediterranean Our new data shows that the onset of the Messinian Salinity Crisis in the Mediterranean was directly preceded by the marine flooding of the Eastern Paratethys, confirming the hypothesis that the Lower Gypsum units formed during a relative high-stand of Mediterranean sea level (Flecker et al., 2002; Krijgsman and Meijer, 2008). A transgression at the onset of the Messinian evaporite formation is in serious contrast to hypotheses inferring glacio-eustatic sea level lowering (Hsü et al., 1973; Clauzon et al., 2005), but has earlier been suggested on the basis of strontium isotope models (Flecker et al., 2002; Flecker and Ellam, 2006). It is interesting to note that the bloom of Odessian ostracods (Fig. 3), indicating re-stabilization of paleoenvironmental conditions in the Paratethys, coincides with the onset of MSC evaporites at 5.96 Ma in the Mediterranean (Krijgsman et al., 1999). Consequently, the changes in Paratethys–Mediterranean connectivity at the Maeotian–Pontian transition interval probably generated a new hydrological equilibrium in both Paratethys and Mediterranean that allows gypsum to precipitate during astronomically-forced optimum (=dry) climate conditions on a precessional resolution in the Mediterranean Basin (Krijgsman et al., 2001). A flooding of the Paratethys basin could only have happened if its water level was significantly below global ocean and Mediterranean level. This indicates that the hydrological budget for the Paratethys region in Maeotian times was slightly negative. Establishing a Mediterranean–
Paratethys connection would result in an increased hydrological flux into the Paratethys and consequently an increase in water and salt flux from the Atlantic into the highly restricted evaporation-dominated Mediterranean. We speculate that creating a connection to the Paratethys will increase Mediterranean stratification and ultimately influence the hydrodynamics of the Gibraltar gateways, two crucial factors to explain the onset of widespread gypsum deposition during the MSC (Meijer and Krijgsman, 2005). 7.2. Location of Paratethys flooding Another intriguing question is: where did the Paratethys flooding actually come from? The Aegean region of the Mediterranean Sea is the most likely source area according to the paleogeographic reconstructions of the Paratethys domain (e.g. Popov et al., 2006), although we cannot exclude the Indian Ocean on the basis of our data. A flooding event is further expected to leave marked traces of significant erosion on land and offshore the Bosporus region (e.g. Loget et al. 2005). The Karadeniz-1 borehole in the European part of the Turkish Black Sea shelf indeed shows Messinian erosional surfaces (Gillet et al., 2007), which can possibly be traced to the Karacaköy region at the Black Sea margin northwest of Istanbul. We thus consider a Karacaköy–Karadeniz passage as potential candidate to account for the flooding event, but more detailed biostratigraphic data is necessary to confirm this hypothesis.
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7.3. Down drop of the sea level during the MSC The observed fall in Paratethyan water level at the base of the Portaferrian is estimated to have occurred at 5.8 Ma in the Dacian Basin (Fig. 3). This is remarkably close to glacial peaks TG22–20 (Fig. 6), which are suggested to have caused a significant drop in global sea level (Shackleton et al., 1995). In the Zheleznyi Rog succession this interval also shows evidence of sea level lowering, expressed by the occurrence of white shell beds of Portaferrian age (Po2: Popov et al., 2006). The climax of the Messinian Salinity Crisis occurred during glacial peaks TG12–14, when the water exchange with the Atlantic became restricted resulting in the formation of massive halite in the deepest parts of the Mediterranean and a dramatic fall in water level (Fig. 6). The potential connection to Paratethys thus also would have become lost, lowering the water level in the Black Sea Basin immediately to the level of the paleo-Bosphorus. Our data from Zheleznyi Rog suggest that this event is clearly reflected in the sharp transition to the reddish interval at the Russian Black Sea margin of the Taman Peninsula. The ultimate lake levels in the isolated Dacian, Black Sea and Caspian basins will obviously be influenced by astronomically induced changes of regional climate. Depending on the hydrological budget of the individual Paratethys basins desiccation (negative) or overflow (positive) will take place (Fig. 6). A marked change occurs in the oxygen isotope curves after TG12 at 5.5 Ma (Fig. 6), interpreted to result in much warmer and humid global climates (Hodell et al., 2001; Hilgen et al., 2007). This resulted in a positive hydrological change and caused widespread transgression of Lago-Mare/Upper Evaporite facies over the Messinian erosional surfaces (Lofi et al., 2005; Roveri et al., 2008). Transgressional sequences are especially clear in Northern Italy where they are attributed to an increased hydrological flux from the Alps (Willet et al., 2006). The timeequivalent transgression in the Paratethys can also be explained by these regional climatic changes. The alternative hypothesis for this transgression is the re-establishment of Paratethys–Mediterranean connectivity by the Zanclean deluge of the Mediterranean at the Miocene Pliocene boundary (5.33 Ma). This would better explain the sharp transition from littoral and fluvial Portaferrian facies to predominantly pelitic facies in the lower Bosphorian. The Bosphorian ostracod and mollusc fauna do not show evidence of significant freshening of the water conditions, although their strontium isotope ratios suggest isolation from the Mediterranean (Vasiliev, 2006). Mio–Pliocene connectivity at high sea level has earlier been suggested by Clauzon et al. (2005), but these authors based it on the nannofossil influxes in the Paratethys at the Pontian–Dacian boundary which are dated at 4.7 Ma and have thus no relation at all with the Pliocene flooding. We realize that a correlation to the Zanclean flooding cannot be excluded on the basis of our data. However, were the Paratethys transgression to be coeval with the Mediterranean flooding, substantial changes in sedimentation rate would be required, especially by a major (4×) increase in the lowermost part of the Bosphorian (below the Thvera). We have not seen any evidence for such an increase in the field, nor in the Râmnicu Sărat section (east Carpathian foredeep), nor in the Topolog region (south Carpathian foredeep). Future research should therefore aim at localizing marine influxes at the base of the Bosphorian and focus on geochemical proxies that may quantify Paratethys–Mediterranean connectivity. 8. Conclusions Our integrated stratigraphic data results in a robust chronological framework for the Dacian and Black Sea basins of the Eastern Paratethys (Table 1), allowing high-resolution stratigraphic correlations between the individual Paratethys subbasins and with the Messinian Salinity Crisis of the Mediterranean (Fig. 6). The Maeotian/Pontian boundary is dated at 6.04 Ma and corresponds to a major faunal change triggered by
a marine flooding of the Paratethys, as evidenced by the presence of planktonic foraminifera. The lowermost Pontian (Odessian/Novorossian) substage relates to a general high-stand in the Paratethys, possibly with interbasinal and Mediterranean connections. The onset of MSC evaporites closely coincides in age with the bloom of Odessian ostracods in the Paratethys at ∼5.95 Ma. The peak of the MSC at 5.6–5.5 Ma definitely ended Mediterranean–Paratethys connectivity in the Portaferrian, causing a sudden drawdown of Paratethys water levels of at least 50–100 m and isolating the Caspian Sea and the Dacian Basin from the Black Sea domain. From 5.5 Ma onward a major change in Eurasian climate, resulting in much warmer and humid conditions changed the hydrological balance and resulted in a widespread transgression in Mediterranean and Paratethys. The Miocene/Pliocene boundary may correspond to the Portaferrian/Bosphorian boundary in the Dacian Basin and to the top of the red layer in Zheleznyi Rog, i.e. within the lower Kimmerian of the Black Sea Basin, but certainly not to the Pontian/ Dacian boundary in the Dacian Basin, which is dated ∼600 kyr younger at 4.7 Ma. Our new stratigraphic framework has also serious consequences for the Mediterranean MSC. Ever since the discovery of widespread Messinian evaporites all over the Mediterranean seafloor, tectonic or glacio-eustatic processes restricting and closing the water exchange to the Atlantic in the west have been put forward and modeled to understand the causes of the Messinian Salinity Crisis (Hsü et al., 1973; Meijer and Krijgsman, 2005; Ryan, 2009), but conclusive answers are still lacking. Our data suggest that changing the connectivity to the Paratethys in the northeast could play an essential role in the onset of gypsum formation, which should give ample ammunition for new ideas and models concerning evaporite formation in semi-isolated basins. This will also have major implications for paleoceanographic circulation patterns, Mediterranean paleosalinity models and the internal stratification of its water column. Acknowledgements We thank Dan Jipa, Iulia Lazăr ar and Gheorghe Popescu for their help with sedimentological and biostratigraphical analyses of the Râmnicu Sărat data. Alexandr Iosifidi is acknowledged for skilful paleomagnetic sampling at Zheleznyi Rog. Cor Langereis, Frits Hilgen, Paul Meijer and Pasha Karami are thanked for discussions and useful comments on an earlier version of this manuscript. Rachel Flecker, Miguel Garcés and four anonymous EPSL reviewers are thanked for their constructive comments. Sergei Yudin and Vika Tomsha assisted with the paleomagnetic analyses. This study was performed under the inspiring leadership of Cor Langereis and Alexei Khramov, within the NWO program on Dutch–Russian cooperation. This work was financially supported by the Netherlands Research Centre for Integrated Solid Earth Sciences (ISES) and the Netherlands Geosciences Foundation (ALW) with support from the Netherlands Organization for Scientific Research (NWO). References Aksu, A.E., Hiscott, R.N., Yasar, D., Isler, F.I., Marsh, S., 2002. Seismic stratigraphy of Late Quaternary deposits from the southwestern Black Sea shelf: evidence for noncatastrophic variations in sea-level during the last 10000 yr. Mar. Geol. 190, 61–94. Allen, M.B., Jones, S., Ismail-Zadeh, A.D., Simmons, M.D., Anderson, L., 2002. Onset of subduction as the cause of rapid Pliocene/Quaternary subsidence in the South Caspian basin. Geology 30, 775–778. Çagatay, M.N., et al., 2006. Paratethyan–Mediterranean connectivity in the Sea of Marmara region (NW Turkey) during the Messinian. Sediment. Geol. 188–189, 171–187. Chumakov, L.S., et al., 1992. Interlaboratory fission track dating of volcanic ash levels from eastern Paratethys: a Mediterranean–Paratethys correlation. Palaeogeogr. Palaeoclimatol. Palaeoecol. 24, 287–295. Cita, M.B., Wright, R.C., Ryan, W.B.F., Longinelli, A., 1978. Messinian paleoenvironments. In: Hsü, K.J. (Ed.), Initial Reports of the Deep Sea Drilling Project, pp. 1003–1035. Clauzon, G., et al., 2005. Influence of Mediterranean sea-level changes on the Dacic Basin (Eastern Paratethys) during the late Neogene: the Mediterranean Lago Mare facies deciphered. Basin Res. 17, 437–462. Dinu, C., Wong, H.K., Tambrea, D., Matenco, L., 2005. Stratigraphic and structural characteristics of the Romanian Black Sea shelf. Tectonophysics 410, 417–435.
W. Krijgsman et al. / Earth and Planetary Science Letters 290 (2010) 183–191 Dumont, H.J., 1998. The Caspian Lake: history, biota, structure, and function. Limnol. Oceanogr. 43, 44–52. Filippova, N.Y., 2002. Spores, pollen, and organic-walled Phytoplankton from neogene deposits of the Zheleznyi Rog reference section (Taman Peninsula). Strat. Geol. Correlat. 10, 176–188. Flecker, R., Ellam, R.M., 2006. Identifying Late Miocene episodes of connection and isolation in the Mediterranean–Paratethyan realm using Sr isotopes. Sediment. Geol. 188–189, 189–203. Flecker, R., de Villiers, S., Ellam, R.M., 2002. Modelling the effect of evaporation on the salinity −87Sr/86Sr relationship in modern and ancient marginal-marine systems: the Mediterranean Messinian salinity crisis. Earth Planet. Sci. Lett. 203, 221–233. Gillet, H., Lericolais, G., Rehault, J.-P., 2007. Messinian event in the Black Sea: evidence of a Messinian erosional surface. Mar. Geol. 244, 142–165. Hallam, A., Wignall, P.B., 1997. Mass Extinctions and their Aftermath. Oxford University Press, Oxford. 320 pp. Hilgen, F.J., Kuiper, K.F., Krijgsman, W., Snel, E., Van der Laan, E., 2007. Astronomical tuning as the basis for high resolution chronostratigraphy: the intricate history of the Messinian salinity crisis. Stratigraphy 2007, 231–238. Hinds, D.J., et al., 2004. Sedimentation in a discharge dominated fluvial/lacustrine system: the Neogene Productive Series of the South Caspian Basin, Azerbaijan. Mar. Petrol. Geol. 21, 613–638. Hodell, D.A., Curtis, J.H., Sierro, F.J., Raymo, M.E., 2001. Correlation of late Miocene to early Pliocene sequences between the Mediterranean and North Atlantic. Paleoceanography 16, 164–178. Hsü, K.J., Giovanoli, F., 1979. Messinian event in the Black Sea. Palaeogeogr. Palaeoclimatol. Palaeoecol. 29, 75–93. Hsü, K.J., Ryan, W.B.F., Cita, M.B., 1973. Late Miocene desiccation of the Mediterranean. Nature 242, 240–244. Jipa, D., 1997. Late Neogene–Quaternary evolution of Dacian basin (Romanian). An analysis of sediment thickness pattern. Geo-Eco-Marina 2, 127–134. Jones, R.W., Simmons, M.D., 1996. A review of the stratigraphy of eastern Paratethys (Oligocene–Holocene). Bull. Nat. Hist. Museum (Geol. Suppl.) 52, 25–49. Krijgsman, W., Meijer, P.T., 2008. Depositional environments of the Mediterranean “Lower Evaporites” of the Messinian salinity crisis: constraints from quantitative analyses. Mar. Geol. 253, 73–81. doi:10.1016/j.margeo.2008.04.010. Krijgsman, W., Hilgen, F.J., Raffi, I., Sierro, F.J., Wilson, D.S., 1999. Chronology, causes and progression of the Messinian salinity crisis. Nature 400, 652–655. Krijgsman, W., Fortuin, A.R., Hilgen, F.J., Sierro, F.J., 2001. Astrochronology for the Messinian Sorbas Basin (SE Spain) and orbital (precessional) forcing for evaporite cyclicity. Sediment. Geol. 140, 43–60. Leever, K.A., 2007. Foreland of the Romanian Carpathians: controls on late orogenic sedimentary basin evolution and Paratethys paleogeography, PhD thesis, VU University Amsterdam, Amsterdam, 182 pp. Leever, K.A., et al., 2009. Messinian sea level fall in the Dacic Basin (Eastern Paratethys): palaeogeographical implications from seismic sequence stratigraphy. Terra Nova. doi:10.1111/j.1365-3121.2009.00910.x. Lofi, J., et al., 2005. Erosional processes and paleo-environmental changes in the Western Gulf of Lions (SW France) during the Messinian salinity crisis. Mar. Geol. 217, 1–30. Loget, N., Van Den Driessche, J., Davy, P., 2005. How did the Messinian salinity crisis end. Terra Nova 17, 414–419. Magyar, I., Sztanó, O., 2008. Is there a Messinian unconformity in the Central Paratethys? Stratigraphy 5, 245–255. Marunteanu, M., Papaianopol, I., 1998. Mediterranean nannoplankton in the Dacic basin. Rom. J. Stratigraphy 78, 115–121. Meijer, P.T., Krijgsman, W., 2005. A quantitative analysis of the desiccation and re-filling of the Mediterranean during the Messinian salinity crisis. Earth Planet. Sci. Lett. 240, 510–520. Nastaseanu, S., Bercia, I., 1968. Baia de Arama. : Carte géologique de Roumanie au 1/ 200.000, vol. 32. Institut géologique, Bucharest.
191
Nevesskaya, L.A., Goncharova, I.A., Ilyina, L.B., Paramonova, N.P., Khondkarian, S.O., 2002. The Neogene stratigraphic scale of the Eastern Paratethys. Strat. Geol. Correlat. 11, 105–127. Panaiotu, C.E., Vasiliev, I., Panaiotu, C.G., Krijgsman, W., Langereis, C.G., 2007. Provenance analysis as a key to orogenic exhumation: a case study from the East Carpathians (Romania). Terra Nova 19, 120–126. Pevzner, M.A., Semenenko, V.N., Vangengeim, E.A., 2003. Position of the Pontian of the Eastern Paratethys in the Magnetochronological Scale. Strat. Geol. Correlat. 11, 482–491. Popov, S.V., et al., 2006. Late Miocene to Pliocene papaeogeography of the Paratethys and its relation to the Mediterranean. Palaeogeogr. Palaeoclimatol. Palaeoecol. 238, 91–106. Reynolds, A.D., et al., 1998. Implications of outcrop geology for reservoirs in the Neogene Productive Series: Apsheron Peninsula, Azerbaijan. AAPG Bull. 82, 25–49. Roveri, M., Lugli, S., Manzi, V., Schreiber, B.C., 2008. The Messinian Sicilian stratigraphy revisited: new insights for the Messinian salinity crisis. Terra Nova 20, 483–488. Ryan, W.B.F., 2009. Decoding the Mediterranean Salinity Crisis. Sedimentology 56, 95–136. Ryan, W.B.F., Pitman, W.C., 1998. Noah's Flood: the New Scientific Discoveries About the Event that Changed History. Simon & Schuster, p. 319. Ryan, W.B.F., et al., 1997. An abrupt drowning of the Black Sea shelf. Mar. Geol. 138, 119–126. Ryan, W.B.F., Major, C.O., Lericolais, G., Goldstein, S.L., 2003. Catastrophic flooding of the Black Sea. Annu. Rev. Earth Planet. Sci. 31, 525–554. doi:10.1146/annurev. earth.31.100901.141249. Savu, H., Ghenea, C., 1967. Turnu Severin. : Carte géologique de Roumanie au 1/200.000, vol. 40. Institut géologique, Bucharest. Semenenko, V.N., 1979. Correlation of Mio–Pliocene of the Eastern Paratethys and Tethys. VII th International Congress on Mediterranean Neogene: Athens, pp. 1101–1111. Shackleton, N.J., Crowhurst, S., Hagelberg, T., Pisias, N.G., Schneider, D.A., 1995. A new Late Neogene time scale: application to leg 138 sites. Proc. ODP Sci. Results 138, 73–101. Snel, E., Marunteanu, M., Macalet, R., Meulenkamp, J.E., van Vugt, N., 2006. Late Miocene to Early Pliocene chronostratigraphic framework for the Dacic Basin, Romania. Palaeogeogr. Palaeoclimatol. Palaeoecol. 238 (1–4), 107–124. Steininger, F.F., et al., 1996. Circum-Mediterranean Neogene (Miocene and Pliocene) marine-continental chronologic correlations of European mammal units. In: Bernor, R.L., Fahlbusch, V., Mittmann, H.-W. (Eds.), The Evolution of Western Eurasian Neogene Mammal Faunas. Columbia Univ. Press, New York, pp. 7–46. Stevanovic, P., Nevesskaya, L.A., Marinescu, F., Sokac, A., Jámbor, A., 1989. Chronostratigraphie und Neostratotypen: Pliozän Pl1. Pontien. JAZU & SANU, Zagreb-Beograd. 952 pp. Stoica, M., Lazar, I., Vasiliev, I., Krijgsman, W., 2007. Mollusc assemblages of the Pontian and Dacian deposits from the Topolog-Arges area (southern Carpathian foredeep — Romania). Geobios 40, 391–405. Trubikhin, V.M., 1986. Neogene magnetostratigraphic scale of the Eastern Paratethys. III conference of Geomagnetism, Kiev, pp. 206–207. Vasiliev, I. 2006. A new chronology for the Dacian Basin (Romania). PhD Thesis Utrecht University, Geologica Ultraiectina, 267, pp 191. Vasiliev, I., et al., 2004. Towards an astrochronological framework for the eastern Paratethys Mio–Pliocene sedimentary sequences of the Focşani basin (Romania). Earth Planet. Sci. Lett. 227, 231–247. Vasiliev, I., Krijgsman, W., Stoica, M., Langereis, C.G., 2005. Mio–Pliocene magnetostratigraphy in the southern Carpathian foredeep and Mediterranean–Paratethys correlations. Terra Nova 17, 376–384. Vasiliev, I., et al., 2007. Early diagenetic greigite as a recorder of the palaeomagnetic signal in Miocene–Pliocene sedimentary rocks of the Carpathian foredeep (Romania). Geophys. J. Int. 171, 613–629. Vasiliev, I., et al., 2008. Putative greigite magnetofossils from the Pliocene epoch. Nat. Geosci. 1, 782–786. doi:10.1038/ngeo335. Willet, S.D., Schlunegger, F., Picotti, V., 2006. Messinian climate change and erosional destruction of the central European Alps. Geology 34 (8), 613–616. doi:10.1130/ G22280.1.