The Marmara Sea Gateway since ~16 ky BP: non-catastrophic causes of paleoceanographic events in the Black Sea at 8.4 and 7.15 ky BP

The Late Quaternary history of connection of the Black Sea to the Eastern Mediterranean has been intensely debated. Ryan, Pitman and coworkers advocate two pulses of outflow from the Black Sea to the world ocean at ~16–14.7 ky BP and ~11–10 ky BP. From ~14.7–11 ky BP and from ~10–8.4 ky BP, they suggest that the level of the Black Sea fell to ~ -100 m. At 8.4 ky BP, they further claim that a catastrophic flood occurred in a geological instant, refilling the Black Sea with saline waters from the Mediterranean. In contrast, we continue to gather evidence from seismic profiles and dated cores in the Marmara Sea which demonstrate conclusively that the proposed flood did not occur. Instead, the Black Sea has been at or above the Bosphorus sill depth and flowing into the world ocean unabated since ~10.5 ky BP. This conclusion is based on continuous Holocene water-column stratification (leading to sapropel deposition in the Marmara Sea and the Aegean Sea), proxy indicators of sea-surface salinity, and migration of endemic species across the Bosphorus in both directions whenever appropriate hydrographic conditions existed in the strait. The two pulses of outflow documented by Ryan, Pitman and coworkers find support in our data, and we have modified our earlier interpretations so that these pulses now coincide with the development of mid-shelf deltas: \Delta 2 (16–14.7 ky BP) and \Delta 1 (10.5–9 ky BP) at the southern end of the Bosphorus Strait. However, continued Black Sea outflow after 9 ky BP prevented the northward advection of Mediterranean water and the entry of open-marine species into the Black Sea for more than 1000 years. Sufficient Mediterranean water to change the Sr-isotopic composition of slope and shelf water masses was not available until ~8.4 ky BP (along with the first arrival of many varieties of marine fauna and flora), whereas euryhaline molluscs did not successfully populate the Black Sea shelves until ~7.15 ky BP. Instead of relying on catastrophic events, we recognize a slow, progressive reconnection of the Black Sea to the world ocean, accompanied by significant time lags

Calcareous benthic foraminiferal biofacies along a depth transect on the southwestern Marmara shelf (Turkey)

A total of 200 calcareous benthic foraminiferal species were identified in 30 surface samples collected across a depth transect in the southwestern Marmara Sea. Q-mode cluster and canonical correspondence analyses performed on the foraminiferal species abundance data revealed three clusters. Environmental parameters collected at each sampling station allowed the correlation between foraminiferal clusters and watermass characteristics, such as water depth, temperature, salinity and dissolved oxygen concentrations. Cluster A (55-130 m) is characterized by species typical of muddy substrates in the circa-littoral zone and related to declining dissolved oxygen values. Cluster (140-350m) is characterized by deep-infaunal dysoxic and suboxic species indicative of circa-littoral and upper epibathyal environments and strongly related to low dissolved oxygen values and increased water depth. Cluster C (15-50m) is characterized by neritic species typical of the infra-littoral environment. This cluster is further subdivided into three subclusters that reflect brackish surface flow (influenced by low salinity, higher temperature), pycnocline (rising salinity, falling temperature) and infra-littoral to circa-littoral transitional environments (higher oxygen from the Mediterranean countercurrent and the subsurface chlorophyll maximum), respectively

Persistent Holocene outflow from the Black Sea to the eastern Mediterranean Sea still contradicts the Noah's Flood Hypothesis: A review of 1997–2021 evidence and a regional paleoceanographic synthesis for the latest Pleistocene–Holocene

This review and synthesis weaves various multiproxy data into a single coherent narrative for the latest Pleistocene–Holocene paleoclimatic and paleoceanographic evolution of the Black Sea, Marmara Sea and the Aegean Sea. This narrative, referred to as the “Outflow Hypothesis” rests on several key observations and interpretations which are incompatible with the suggestion that the post-LGM reconnection of the Black Sea basin to the global ocean occurred as a catastrophic flood. The widespread occurrence of sub-storm-wavebase uppermost Pleistocene to lower Holocene sediments across the southwestern Black Sea shelf at elevations as shallow as −78 m shows that the level of the Neoeuxine Lake (today's Black Sea) between 12.3 cal ka and 9.5 cal ka was high enough to spill outward into the Marmara Sea over the shallow sill in the southern Strait of Bosphorus (−37 m today). Southwest-prograded clinoforms immediately south of the strait in the northeastern Marmara Sea record the development of an early Holocene (11.1–10.2 cal ka) mid-shelf delta (Δ1) showing ~3.3 km of aggressive progradation while its topset-to-foreset break climbed 8–9 m into a rising Marmara Sea. A streamlined south-prograded barform in the throat of the strait and giant megaflutes along its thalweg confirm the vigorous outflow from the early Holocene Neoeuxine Lake required to explain the climbing Δ1 lobe. Multiproxy data from the northeastern Marmara Sea and southwestern Black Sea shelves indicate that the post-Last Glacial Maximum (LGM) reconnection of the Black Sea with the eastern Mediterranean occurred in a gradual fashion: first, at ~10.2 cal ka, a salt wedge lifted the brackish outflow off the floor of the Strait of Bosphorus terminating Δ1 progradation; second, a more persistent density underflow introduced enough seawater strontium into the Black Sea to be taken up in mollusc shells by ~9.5 cal ka, and finally a range of euryhaline marine organisms replaced lacustrine faunas when salinity levels became favourable by ~7.5 cal ka. The onset of sapropel M1 deposition across the Marmara Sea followed the breach of the Strait of Dardanelles at 13.8 cal ka when, as originally suggested by other researchers, nutrient-rich highly saline Mediterranean waters forced lower density relict lacustrine waters to the surface and then out through the Strait of Dardanelles, initiating water-column stratification. Once the low-salinity cap was expelled, the deep waters of the fully saline Marmara Sea remained stagnant and sapropel accumulation continued. The onset of outflow from the Neoeuxine Lake at 11.1 cal ka re-established water-column stratification, induced effective deep circulation across the Marmara Sea, and created a low salinity lid across the northern Aegean Sea, initiating sapropel S1 deposition in that area

Neogene and Quaternary Planktonic Foraminifer Biostratigraphy and Biochronology in Baffin Bay and the Labrador Sea

During Ocean Drilling Program Leg 105, 11 holes were drilled in the Labrador Sea and Baffin Bay. Site 645 in Baffin Bay was drilled to a depth of 1147 meters below seafloor (mbsf); planktonic foraminifers were recovered in the upper 110.3 m and in a short interval between 283.8 and 293.5 mbsf. Low species diversity and the lack of species with short stratigraphic ranges inhibited establishment of a planktonic foraminifer biostratigraphic framework at Site 645. Holes 646B and 647A in the Labrador Sea were drilled to depths of 766.7 and 716.6 mbsf, respectively. Although the observed assemblages in the Labrador Sea holes were of low diversity, the first and last occurrences of several age-diagnostic species, when integrated with paleomagnetic stratigraphy, allowed the establishment of a high-latitude Miocene to Holocene planktonic foraminifer biochronology. To determine the relative timing of planktonic foraminifer datum events in the eastern North Atlantic and the Labrador Sea, this biochronology is compared with the temperate-subpolar biozonation of Weaver and Clement (1986). The late Miocene dextral-to-sinistral coiling change in Neogloboquadrina atlantica was observed — 1.6 m.y. earlier at Site 646 than at any other site in the Atlantic. The first appearance datums (FAD) of Globorotalia margaritae, Globorotalia puncticulata, Globorotalia irtflata, and the last appearance datum (LAD) of N. atlantica are isochronous with their reported ages in the eastern North Atlantic, but the FADs of Globorotalia truncatulinoides and the modern, encrusted form of Neogloboquadrina pachyderma are diachronous

The uppermost Pleistocene–Holocene mud drape across the Marmara Sea: quantification of detrital supply from southern Marmara rivers

The Marmara Sea (area 11,350 km2; volume 3,378 km3; central basins >1100 m deep) straddles the North Anatolian Transform Fault separating the Eurasian and Aegean-Anatolian tectonic plates. Along with the shallow straits of Dardanelles and Bosphorus (depths ~63 m and ~40 m, respectively), the Marmara Sea forms the only marine connection between the Black Sea and the eastern Mediterranean. During Pleistocene glacial stages, the modern straits were subaerial valleys and the modern Marmara basin was occupied by the landlocked Propontis Lake. Previous researchers attributed major portions of a widely distributed uppermost Pleistocene–Holocene mud blanket (locally >10–25 m thick; volume 43–47 km3) to transport of suspended load through one or both of the straits, as either the Aegean Sea (at ~13.8 cal ka) or the Neoeuxine Lake (today's Black Sea, at ~11.1 cal ka) began to spill into the Marmara basin. To test these suggestions, the thicknesses and volume of the mud blanket were determined from >5000 line-km of airgun, sparker and boomer profiles and >100 cores, and compared with the contemporary supply from local rivers to decide, by difference, if the straits might have had a significant role. Volume calculations for the detrital supply from rivers rely on (1) decades of daily water- and sediment-discharge data from gauging stations, acquired before 20th century dam construction and, independently, (2) the BQART model which uses a variety of hydrological, geomorphic, geological and climate data. These calculations demonstrate that >85–90% of the detritus in the offshore mud blanket was supplied by steep rivers (Kocasu River and its tributaries) and mountainous streams draining the highlands of the southern Marmara region. Geochemistry of the <38 μm fraction supports this source. Any input through the Dardanelles has been sporadic and limited to perhaps ~5 Gt of suspended load (equivalent to ~5.2 km3 of porous mud when deposited) because of changing directions and rates of flow since the Last Glacial Maximum. Resedimentation through mass wasting and transgressive shoreface erosion appear to be minor compared with river supply. The isolated nature of the Marmara basin and its supply from mostly a single watershed afford an opportunity to verify the reliability of this type of hindcast analysis, based upon sediment-discharge data and catchment models – analysis which cannot be completed with a comparable level of certainty along open marine coastlines elsewhere

Giant slope scars and mass transport deposits across the Rhodes Basin, eastern Mediterranean: Depositional and tectonic processes

High-resolution multichannel seismic reflection profiles and multibeam mosaic maps of the seafloor are used to document the presence of two prominent regions representing major sediment failure(s) and the subsequent gravity-driven mass transport across the southwestern continental margin of Anatolia. These regions are characterized by very sugged morphology (referred to as Scars 1 and 2), where the upper slope regions include several concave, interconnected steep seafloor escarpments marked by semi-circular indentations that link with one another by cusp-like features creating a sharp and very narrow curvilinear zone. The slope face across the rugged region there are numerous sharply irregular pinnacles/protrusions on the seafloor, consisting of exposed older bedrock successions. Scars 1 and 2 occupy seafloor areas of 1947 km2 and 1350 km2, solid volumes of 214–257 km3 and 92–111 km3, and masses of 467–681 Gt and 245–294 Gt, respectively, with a total solid volume of 307–368 km3 and a mass of 812–975 Gt. Mass transport deposits are identified at various stratigraphic levels across the Rhodes Basin characterized by chaotic seismic reflector configurations with zones of contorted and convoluted reflector geometries. The base of this facies is characterized by erosional down-cutting. The thickest and the regionally most extensive such deposits are found at the base of Unit 1, immediately above the upper bounding surface of the Messinian evaporites (the Top Erosional Surface or the former M-reflector). The lower mass transport deposit (L–MTD) is calculated to have a volume 205–171 km3, or a solid mass of 543–452 Gt, assuming that porosities of 40–50% and average grain density of 2.67 t m−3. Comparisons between the total mass of the L–MTD and the estimated masses of sediments mobilized across Scars 1 and 2 (812–975 Gt) indicate that there is ~360–432 Gt deficit in the calculated mass of the L–MTD. The missing sediments represent 17.5–21.0% of the total mass contained within Unit 1 across the present-day Rhodes Basin. This mismatch is remarkably large: it may arise from the uncertainties involved in the estimations of the masses of sediments contained in Scars 1 and 2; however, it is also possible that some of the gravity driven mass transports transitioned into turbidity currents, thus travelled great distances across the Rhodes Basin, and that some of these turbidity currents crossed the basin longitudinally, and exited it at its southwestern deeper regions (i.e., the present-day Strabo Trench). This is particularly plausible because the physiography of the Rhodes Basin was dramatically different during the early Pliocene and the southern and southwestern portions of the basin provided a possible exit route

Distribution of modern agglutinated foraminifera along an inner neritic- to mid-bathyal transect in Saros Bay (northern Aegean Sea).

Agglutinated benthic foraminifera were investigated in the central Northern Aegean Sea. Eighteen samples were collected along a neritic to mid-bathyal transect in Saros Bay at water depths ranging from 15 to 500m in March 2003. This study documents for the first time in detail, agglutinated foraminiferal species and their bathymetric distribution in this area. A total of 96 species belonging to 51 genera were recognised. Statistical analyses (CA and PCA) allowed us to identify different assemblages that can be related to bathymetric depth and trophic level and, in turn, to different hydrological zones. The shallowest assemblage (15m) is characterised by the lowest species richness that might result from the influence of the Black Sea outflow into Saros Bay. The shallow assemblages stations (21-70m) are characterized by relatively low diversity and higher dominance values. On the other hand, assemblages from intermediate water (80-200m) are characterised by high diversity values and the dominance of elongate keeled forms associated with elongated tapered forms, providing evidence of mesotrophic conditions. The deepest assemblages, including stations ranging from water depths of 200 to 500m, are very well-diversified and mainly represented by epifaunal taxa. The dominance of tubular morphogroup might be due to the low food supply, which acts as a limiting factor for more eutrophic dependent taxa and meso-oligotrophic conditions might be inferred