Different multidisciplinary data concerning the paleodynamics of sea-level variations in the Caspian and Black seas are controversial in some aspects. There are at least three paradoxes that are ...discussed in the paper. The Paradox No. 1 relates to the Early and Late Khvalynian transgressions that occurred in the CS during the second part of MIS 3 (∼35–25 ka BP) and the Late Glacial epoch (∼17–12 ka BP), respectively. It is unclear what the main source or sources of water were that caused them. Paradox No. 2 emerges from the comparison of climate events and transgressive-regressive cycles in the Caspian Sea and the Black Sea. It implies that large sea-level anomalies occurred in accordance with global climate changes (because they are influenced by climate variations). However, other (not so long-lived) sea-level fluctuations are poorly correlated with climate events. The question is why climatically-induced sea-level changes did not follow climatic variations. Paradox No. 3 concerns the contradiction between the massive water discharge from the Black Sea into the Sea of Marmara via the Bosphorus Strait and the Black Sea level fluctuations in the Latest Pleistocene-Holocene that could not exist simultaneously. It is shown that Paradox No. 2 has been solved, at least on conceptual level. Solutions to Paradoxes No. 1 and No. 3 are still lacking: further geological and geochronological evidence as well as climate simulation are required. Formulation of solutions for these paradoxes should make a major contribution not only to the problems of the Caspian and Black seas’ paleogeography, but also provide help in explaining the reasons for inadequate simulation of regional climate changes. This is important in the context of the development of models for future climate prediction.
For two decades, the timing and rate of Holocene marine transgression and the level of the Black Sea prior to the transgression has been the focus of many geological, palaeoecological and ...archaeological studies. The potential importance of confirming or rejecting the catastrophic flood hypothesis by refining the chronology of the marine transgression and determining the water level of the early Holocene Black Sea (Neoeuxinian) lake is the aim of many ongoing Black Sea palaeoecological studies.
In this report we review previous studies and present new data on the early Holocene marine transgression obtained from multidisciplinary studies of several cores from different parts of the Black Sea. Core 342 from the edge of the Dniester paleovalley on NW shelf is particularly important because it provides wood and leaf material from several peat and muddy peat beds, each up to ∼10 cm thick, inter-layered in a coastal succession with mud, clay, and shell coquina. AMS ages for wood fragments and sedge leaves in the peat layers provide critical new data for calibrating and “re-tuning” of previously published shell and bulk detrital peat ages.
Our multi-disciplinary study of geological material recovered from different shelf areas of the Black Sea refines the chronology of the marine transgression and clarifies conflicting interpretations of the water level and salinity of the Neoeuxinian lake prior to the initial Mediterranean inflow (IMI) and transgression of Mediterranean water in the Holocene, We find that: (1) The level of the Late Neoeuxinan lake prior to the early Holocene Mediterranean transgression stood around −40 m bsl but not −100 m or more as suggested by advocates of catastrophic/rapid/prominent flooding of the Black Sea by Mediterranean water. (2) At all times, the Neoeuxinan lake was brackish with salinity not less that 7 psu. (3) By 8.9 ka BP, the Black Sea shelf was already submerged by the Mediterranean transgression. An increase in salinity took place over 3600 years, with rate of the marine water incursion being estimated in the order of 0.05 cm–1.7 cm a−1. (4) The combined data set of sedimentological characteristics and microfossil data establish that the Holocene marine transgression was of a gradual, progressive nature in the early Holocene.
Most previous Black Sea palynology studies have used pollen-spore assemblages as proxies for climate and landscape changes, and dinocyst assemblages as proxies for surface water salinity. However, ...there are few data on within-region variations in these assemblages using large sets of surface samples and a full suite of palynomorphs, including terrigenous pollen + spores, freshwater algal spores, and organic remains of marine microplankton, micro- and meiobenthos. Here we fill this knowledge gap, using results from a palynological study of 43 surface samples from water depths of 71–905 mbsl on the Ukrainian Shelf and adjoining continental slope, NW Black Sea. The palynology samples were collected in conjunction with water and sediment chemistry data, grain-size, micropaleontological and meiobenthos data from the EU-FP6 project HERMES “Hotspot Ecosystems Research on the Margins of European Seas”. This dataset uniquely covers shelf and upper slope areas east and west of the Odessa-Sinop Fault Zone (OSFZ) that delimits areas of lower and higher hydrocarbon gas contents, respectively.
The new data show that on the wide shelf with a shallow (ca. 80 m) oxycline, pollen assemblages differ from classical models for marine pollen transport. On the Ukrainian Shelf, pollen concentrations are extraordinarily high far offshore and the grains are often pyrite-infilled. These features apparently reflect high pollen preservation potential in low oxygen sediments, probably enhanced by cross-shelf transport of land-derived particulate organic matter. The new data have important consequences for accurate modelling of carbon burial and storage in epicontinental seas, and they provide a baseline for evaluating marine pollen concentrations expected to reflect the early Neolithic farming on the Ukrainian shelf. Furthermore, although large concentrations of dinocysts comprise more than half of the total Non-Pollen Palynomorphs (NPP), the high pollen concentrations skew the P:D index (pollen:dinocyst ratio) commonly used to evaluate changes in paleo-shoreline (proxy sea-level) positions. Despite the discharge of several large rivers to the Ukrainian Shelf, there are negligible traces of freshwater algae in the HERMES samples except at Sta. 15 where Pediastrum is abundant. Overall, palynomorphs of terrestrial origin make up about half (52%) of the acid-resistant organic-walled particles on the outer NW Black Sea Shelf and adjacent slope.
The abundances of the major micro- and meiobenthic palynomorph groups show the same trends east and west of the OSFZ as the micropaleontological data reported for the HERMES samples taken at the same sites. The combined microzooplankton and zoobenthos surface assemblage data provide an important new baseline for evaluating historical and past changes in biodiversity and aquatic foodweb structure in the now polluted NW Black Sea. Comparison can also be made with foodweb reconstructions for Permian black shales.
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