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Upper Quaternary evolution of the Mamaia Lake area (Romanian Black Sea shore)

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Abstract

Late Quaternary climate changes triggered the succession of several sedimentary environments, especially in the areas close to the current Romanian Black Sea shoreline. These have resulted in the succession of continental and marine lithofacies. The Mamaia karst depression consists of a sedimentary fill, which contains two marine transgression sequences (Surozhian and Holocene) divided by a sedimentary break, corresponding to the MIS 2 regression. The samples from two cores from the Mamaia barrier beach were analysed for lithology, texture, mineralogy, and fauna (molluscs, foraminifera, and ostracods).

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... During this time the Strait of Dardanelles was breached, but sea level likely remained below the level of the floor of the Bosphorus valley (Aksu and Hiscott, this volume). Marine fauna dating from MIS 3 across the northwestern Black Sea shelf suggest that a saline watermass might have been advected into the Black Sea sometime during MIS 3 (Chepalyga, 2002a,b;Yanko-Hombach, 2007;Caraivan et al., 2012;87 Sr/ 86 Sr values of 0.7090 in fig. 13D of Yanchilina et al., 2017), but the survival of euryhaline organisms in local refugia persisting since MIS 5 is another possibility to explain these occurrences (Aksu and Hiscott, this volume). ...
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The Marmara Sea is a crucial gateway for water exchange with the inland Black Sea through the Strait of Bosphorus and with the Aegean and the Mediterranean Seas through the Strait of Dardanelles in the south. A wide-ranging literature review was made of the complex paleoceanographic history for the Marmara Sea Gateway, based on disparate geomorphological, geochemical, palynological and paleontological records from sediment cores on a millennial time-scale. In this manuscript, we review the characteristics of a wide variety of organisms that live in the Marmara Sea today and contribute to fossil floras and faunas that along with pollen and spores provide archives of past environmental and oceanographic changes. Macrobiota leave a patchy or incomplete record, and some calcareous and siliceous micro-organisms are absent in cold, low salinity water or high bottom water acidity. Hence, we focus on palynological studies for a wide range of organic-walled non-pollen palynomorphs (NPPs) from the Marmara Gateway, using re-calibrated age models for five cores based on 24 radiocarbon dates. Tgradient. We use two high-resolution piston cores (M02-88P and M02-89P) from the İmralı Basin to document vegetation and paleo-ceanographic changes on a scale of ~15–30 yr cm-1 from the end of MIS 3 to ~10 yr cm-1 for MIS 1 and recent times when human impacts clearly prevail over natural sea level and global climate events. The new data confirm that the MIS 3 to 17.5 cal ka interval was characterized by vegetation indicating local refugia with >600 mm annual rainfall, and enough warmth to support Castanea forest. The Marmara basin was occupied by the Propontis Lake, which was more saline and/or more oligotrophic than the contemporary Neoeuxine Lake in the Black Sea basin or the Caspian Sea. The sparse lake dinocyst assemblages are most similar to the MIS 2–5a dinocyst flora of Gulf of Corinth, Greece . There may have been sea-ice formation on the lake during winter months and we report for the first time, presence of ostracods, and the eggs or egg capsules of herring and trout fish parasites that may have marked a stressed fish population. The entire Propontis Lake interval is marked by a prevalence of parasitic chytrid and saprophytic biota (cf. Multiplicisphaeridium) that may reflect the low dinoflagellate population. After the Last Glacial Maximum at ~20 cal ka, the Propontis Lake remained low (~ –100 m) except during meltwater discharge event(s) but the flooding left little trace in the lake biota. Climate was cold and dry, and primary production remained low but new ostracod remains appear in the NPP fraction for the first time, and there are traces of Ammonia spp. benthic foraminifera. A major series of oceanographic changes began at ~13.8 cal ka when rising Aegean Sea waters entered the Marmara basin, affecting its full salinification in less than ~700 yr and triggering more eutrophic conditions, sapropel development, and immigration of calcareous marine phyto- and zoo-plankton. There was a decrease in freshwater Pediastrum coenobia, concurrent with the appearance of benthic foraminiferal linings and planktonic foraminiferal tests, increased dinoflagellate cyst concentrations including the Paratethyan relict Spiniferites cruciformis and other Pannonian Basin Spiniferites species, such as Spiniferites maisensis. From ~13.5–12.9 cal ka, there was a rapid increase in pollen concentration, but reduced arboreal pollen and greatly increased Artemisia sage brush pollen that clearly marks the Younger Dryas cold interval 12.9 to 11.7 cal ka region-wide. Increases of oak and other thermophilous tree taxa mark the early interglacial Greenlandian Age and the start of the Holocene thermal optimum that terminated around the time of the Meghalayan 4.2 cal ka drought event, recorded here for the first time. There is a succession of freshwater algae: the glacial stage chorophyte Pediastrum is followed by the desmid Staurastrum volans around 11 cal ka, ending with the more eurythermal, bloom-forming chlorophyte Botryococcus at ~10.5 cal ka, pointing to progressive eutrophication of the Marmara Sea surface waters. The thermal optimum is marked by higher amounts and greater diversity of dinoflagellate cysts that can generate harmful algal blooms, but their abundances decline abruptly at 3 cal ka for uncertain reasons that may include climate cooling before the industrial age and recent climate warming.
... The cyclic Upper Quaternary climate changes induced drastic remodeling of the Black Sea level and the corresponding shorelines [3,4] (Fig. 6). ...
... The lithological studies of cores from the Mamaia barrier beach (Caraivan 1982;Caraivan et al. 1986;2012), corroborated with geomorphological data from the Romanian Black Sea shelf (Panin & Popescu 2007;Strechie-Sliwinski 2007), allow the sequential reconstruction of paleogeographic and sedimentary environments during the Late Quaternary period. The first marine sequence is at the 38 m to 22 m level in the F6 core sequence (Mamaia North), with marine and brackish fauna (Fig. 18.9). ...
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The Black Sea level is dependent on global climate change and Global Ocean level, the water intake from the Danube, and the astronomical sea and wind regime. Bathymetric, seismic-acoustic and sedimentological studies made by GeoEcoMar on the Romanian Black Sea shelf permit the identification of three distinct units: the littoral zone, the inner shelf, and the outer shelf. The lithological studies of cores from the Mamaia barrier beach, corroborated with geomorphological data from the Romanian Black Sea shelf, allow the sequential reconstruction of paleogeographic and sedimentary environments during the Late Quaternary period. The main stages of the Danube Delta evolution during the Holocene were highlighted and dated using the corroboration of geomorphologic, structural, textural, geochemical, mineralogical, and faunal analyses, and radiocarbon dating. The absence of Mesolithic and Early Neolithic traces in Dobrogea is explained by environmental factors such as the flooding of paleorivers by waters from the western part of the Black Sea.
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Some Black Sea researchers still support the idea of no other connection to the Mediterranean Sea between LGM and Karangatian Stage (Riss-Wurm). We try to clarify the source of these disagreements. C14 AMS age data (HERAS Project) made on undisturbed samples from a new Mamaia drilling hole where compared with the classical Black Sea stratigraphic schemes. A first transgressive event (Zone D) is found between 38.00-20.20 m depth. Zone D4 shows a fairly rapid rise of sea level, about 10 m below the present one indicating an inner shelf marine polyhaline environment. AMS age data show 14C ages between 53690-47359 y (MIS 1), corresponding to the "Surozhian Beds" of Popov. The "beach rock" from Zone E marks the decrease of the sea level after the maximum reached in Zone D4. Zone E mollusc shells AMS data, indicate 14C ages of 48724-44604 y, suggesting a long-time reworked material from the previous D4 zone sediments, and represents the beginning of the "regressive Tarkankutian" sequence.The Last Glacial Maximum (LGM) led to the retreat of the sea level down to about 100 m below the current one (27-17 ky BP), followed by an retreat of the shoreline to the present position. At the beginning of the Holocene-MIS 1 (8408-8132 cal. y BP), Black Sea brackish water level grew rapidly, up to-14 m below the present one (Zone F: 22, 57-20, 20 m). Zone F deposits could be correlated with the Bugazian strata. Then, a continuous rising of the Black Sea level is recorded up to a maximum of-2 m under the present one, about 6789-7063 cal. y BP, when a transgressive spurt ("Neolithic transgression") may have taken place. After that, given a weak Danubian sedimentary input, coastal erosion intensified. The coarse sandy sediments were reworked and pushed over the previous peat deposits, and suggest a classical "sedimentary regression", not a sea-level decrease. During the last 1.5 ky, sea level has risen towards the current one. Previous C14 dates from "Karangatian stratotypes", show ages between 27390-42120 y BP. Our AMS C14 data on Surozhian mollusk indicate ages between 47359-53690 cal. y BP.
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HERAS is the acronym of the project entitled "Submarine Archaeological Heritage of the Western Black Sea Shelf".The purpose of this project was to explore the western Black Sea continental shelf and identify underwater archaeological sites in order to promote them in the "Scuba Diving" adventure tourist circuit.This project brought together institutions from Romania and Bulgaria – under the Cross-border Cooperation Programme Romania – Bulgaria 2007-2013. The adoption of the UNESCO Convention on 2 November 2001 as the international treaty to save the underwater cultural heritage facilitates joint exploration of the multimillenary history of the Black Sea western coast at Constanta and Kaliakra, as an important part of the European Union eastern border. The HERAS project aimed at promoting Scuba Diving adventure tourism in the Constanţa - Balchik area and increase the tourism potential of the western Black Sea, through the identification and promotion of common underwater archaeological heritage. The main objective of the "HERAS" project - the identification of the common underwater archaeological heritage on the west coast of the Black Sea at Constanţa and Kaliakra -, has not been explored so far. Since the creation of the first ancient Greek colony Histria, the Constanţa - Balchik area have witnessed the rise and fall of several empires, from the Romans to the Byzantines and Turks, and also passed through barbarian invasions, Genoese dominion, etc. Vestiges of this common history were studied onshore, where ancient cities and towns are known to archaeologists and transformed into tourism interest areas. Historical sites, both on land and underwater in particular, became attractive to tourists around the world. The HERAS project, classified in the Priority Axis 3 - Economic and Social Development of the Programme CBC Romania - Bulgaria aimed at: - discovering, identifying and promoting common submarine archaeological heritage in the western part of the Black Sea, near Constanţa - Kaliakra; - promoting "Scuba Diving" adventure tourism through a media campaign meant to increase awareness.
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This paper reviews the geological and foraminiferal evidence collected in course of extensive geological and palaeooceanograpic studies of the Black Sea since 1970 largely by the eastern scientists to examine the Noah’s Flood Hypothesis proposed by William Ryan and Walter Pitman. According to this hypothesis the Black Sea was a freshwater lake with a level ca 140 m below present during 14.7-10 ky bp. At 7.2 ky bp (initial hypothesis) or 8.4 ky bp (modified hypothesis), the lake was rapidly flooded by Mediterranean waters through the Bosphorus, forcing the dispersion of early Neolithic people into the interior of Europe, and forming the historical basis for the biblical legend of Noah’s Flood. In the context of the Noah’s Flood hypotheses, the time span 28-7 ky bp is emphasized and three crucial points are discussed: (1) level and salinity of the Neoeuxinian lake; (2) re-colonization of the Black Sea by Mediterranean immigrants, and, by implication, sea level and salinity changes due to connection/isolation between adjacent basins; (3) “an alternative” to the Bosphorus connection between adjacent basins. It is shown that prior the moderately warm Würm Paudorf (Middle Weichselian) Plenigalcial (prior to ca 27 ky bp), there was a brackish Tarkhankutian basin connected with the Sea of Marmara. At LGM, this connection was lost, and the level of the Tarkhankutian basin dropped to ca-100 m transforming this basin into closed Early Neoeuxinian lake. In a warming climate at ca 17 ky bp, a massive water discharge most likely from the Caspian Sea via Manych Outlet increased the level of the Late Neoeuxinian lake to ca-20 m. The latter must have spilled an excess of semi-fresh to brackish water into the Sea of Marmara and from there into the Mediterranean. During the short climate cooling episode occurring at Younger Dryas, the level of the lake dropped from -20 m to -43 m and than rose again to ca -20 m. After ca 10 ky bp, the level of the Black Sea never again dropped below ca 40 m iosobath, nor exhibited a maximum amplitude of fluctuation greater than ca 20 m. At ca 9.5 ky bp, it reached -20 m again, allowing Mediterranean waters and organisms to enter the Late Neoeuxinian lake. The re-colonization of the Black Sea occurred in an oscillating manner. It was slow at the beginning, becoming most prominent at ca 7.0 ky bp. The connection between adjacent basins was probably not through the Bosphorus Strait, but via an alternative route, e.g., Izmit Bay - Sapange Lake - Sakarya River. On average, the sea level rose gradually but in an oscillating manner to the present level, and perhaps slightly higher, averaging 3 cm per 100 years but certainly not 15 cm per day (almost 55 m per year) as postulated by the Noah’s Flood hypothesis. The increase of the sea level by 3 cm per 100 years would not be noticed by the inhabitants and would not have accelerated their dispersion into the interior of Europe, bringing us to the conclusion that “Noah’s Flood” in the Black Sea is a contemporary legend.
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The rapid intertidal lithification of beach deposits in the coral seas has received the attention of numerous investigators. Study of beachrock from the Dry Tortugas, Florida, shows that the aragonite cement is precipitated from the sea water remaining in the beach sands at low tide. High temperatures, rate of beach drainage, and the permanence of the beach, control the localization of beachrock. The recognition of beachrock in the fossil record is briefly discussed.
New proofs of the Black Sea rise during the Middle Würm interstadial Dari de Seama ale Sedintelor
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