Biogenic components of the Baltic Sea sediments

The contents of biogenic components in 1511 samples of the Baltic Sea sediments (depth range 0–5 cm) are studied, and maps of their distribution are compiled. The sediments contain < 13.03% C_org, < 1.33% N, < 9.0% SiO_2am, < 5.0% CaCO₃, and < 1.45% P. The maximum and elevated contents of components are found in the mud of the sea deeps. The more fraction < 0.01 mm the sediments contain, the higher are the contents of components. Four facies types of carbonaceous mud, precursors of shales, have been recognized: (1) shallow-water (lagoon) lime sapropel, (2) carbonaceous mud of the shallow-water Gulf of Finland, (3) carbonaceous mud of the middle-depth Baltic Sea, and (4) laminated carbonaceous metal-bearing mud. The latter type of mud is strongly enriched in manganese and ore-forming trace elements, which points to its formation in the stagnant environment. In composition the Baltic Sea mud is similar to petroliferous mudstones of the Bazhenov Formation in West Siberia and to ancient black shales.     

Early diagenesis of organic matter in recent Black Sea sediments: characterization and source assessment

The organic matter in 9 recent (not more than 250 years old) and ‘organic-rich’ sediments from the southern Black Sea shelf and upper slope have been characterized semi-quantitatively by Pyrolysis/Gas Chromatography/Mass Spectrometry (PY/GC/MS) and¹³C Cross Polarization Magic Angle Spinning Nuclear Magnetic Resonance (CPMAS-NMR) spectrometry. The organic matter of 7 of the studied sediments was found to be ligno-carbohydrate with a proteinaceous component, one sediment appeared to contain oxidized coal dust and one contained thiophenes in association with pyrite. The ligno component is derived from grasses and soft wood lignin. Material entrapped in an anoxic environment contained the highest proportions of carbohydrate and protein. All the samples had suffered diagenesis as is generally shown by the attachment of carboxyl groups and the removal of methoxyl groups. The evidence suggests that diagenesis occurred whilst the particles traversed the oxic water column.     

Sulfur speciation in the upper Black Sea sediments

We report solid phase sulfur speciation of six cores from sediments underlying oxic, suboxic and anoxic-sulfidic waters of the Black Sea. Our dataset includes the five sulfur species [pyrite-sulfur, acid volatile sulfides (AVS), zerovalent sulfur (S(0)), organic polysulfides (RS_x), humic sulfur] together with reactive iron and manganese, as quantified by dithionite extraction, and total organic carbon. Pyrite – sulfur was the major phase in all cores [200-400 µmol (g dry wt)^- 1] except for the suboxic core. However, zerovalent sulfur and humic sulfur also reached very significant levels: up to about 109 and 80 µmol (g dry wt)^- 1, respectively. Humic sulfur enrichment was observed in the surface fluff layers of the eastern central basin sediments where Unit-1 type depositional conditions prevail. Elemental sulfur accumulated as a result of porewater sulfide oxidation by reactive iron oxides in turbidities from the anoxic basin margin and western central basin sediments. The accumulation of elemental sulfur to a level close to that of pyrite-S in any part of central Black Sea sediments has never been reported before and our finding indicates deep basin turbidites prevent the build-up of dissolved sulfide in the sediment. This process also contributes to diagenetic pyrite formation whereas in the non-turbiditic parts of the deep basin water column formed (syngenetic) pyrite dominates the sulfur inventory. In slope sediments under suboxic waters, organic sulfur (humic sulfur + organic polysulfides) account for 33-42% of total solid phase S, indicating that the suboxic conditions favor organosulfur formation. Our study shows that the interactions between depositional patterns (Unit 1 vs. turbidite), redox state of overlying waters (oxic-suboxic-sulfidic) and organic matter content determine sulfur speciation and enable the accumulation of elemental sulfur and organic sulfur species close to a level of pyrite-S.     

Phosphorus recycling and burial in Baltic Sea sediments with contrasting redox conditions

In this study, redox-dependent phosphorus (P) recycling and burial at 6 sites in the Baltic Sea is investigated using a combination of porewater and sediment analyses and sediment age dating (²¹⁰Pb and ¹³⁷Cs). We focus on sites in the Kattegat, Danish Straits and Baltic Proper where present-day bottom water redox conditions range from fully oxygenated and seasonally hypoxic to almost permanently anoxic and sulfidic. Strong surface enrichments of Fe-oxide bound P are observed at oxic and seasonally hypoxic sites but not in the anoxic basins. Reductive dissolution of Fe-oxides and release of the associated P supports higher sediment-water exchange of PO₄ at hypoxic sites (up to ∼800 μmol P m⁻² d⁻¹) than in the anoxic basins. This confirms that Fe-bound P in surface sediments in the Baltic acts as a major internal source of P during seasonal hypoxia, as suggested previously from water column studies. Most burial of P takes place as organic P. We find no evidence for significant authigenic Ca-P formation or biogenic Ca-P burial. The lack of major inorganic P burial sinks makes the Baltic Sea very sensitive to the feedback loop between increased hypoxia, enhanced regeneration of P and increased primary productivity. Historical records of bottom water oxygen at two sites (Bornholm, Northern Gotland) show a decline over the past century and are accompanied by a rise in values for typical sediment proxies for anoxia (total sulfur, molybdenum and organic C/P ratios). While sediment reactive P concentrations in anoxic basins are equal to or higher than at oxic sites, burial rates of P at hypoxic and anoxic sites are up to 20 times lower because of lower sedimentation rates. Nevertheless, burial of reactive P in both hypoxic and anoxic areas is significant because of their large surface area and should be accounted for in budgets and models for the Baltic Sea.     

Provenance and diagenesis of organic matter in Late Cretaceous and Tertiary sediments from the southern Black Sea margin

The organic matter in the Late Cretaceous and Tertiary sediments from the southern Black Sea margin is assigned to the terrestrial-marine/terrestrial range of organic facies. Within this range, the stratigraphic section yields different organic facies types in response to different accumulation and preservation controlling processes. During the Late Companian-Maastrichtian, organic material from the shelf and slope was re-deposited in the deeper oxic parts of the basin. Rapid transport and sedimentation resulted in a higher degree of preservation of lipid-rich, terrestrial components (sporinite, cutinite, resinite) in comparison to the autochthonous sediments. The increase in organic carbon with increasing silt/clay content together with low carbon concentrations in the allochthonous sediments suggest that the accumulation of organic matter in the source areas was controlled by terrigenous influx and that the accumulation conditions were not favorable.In the Eocene (fore-arc basin), the higher content of marine organic matter can be explained by progressive shallowing of the environment and by reduced oxygen content in the bottom waters (reduced bioturbation).In the Miocene and Pliocene (back-arc basin), the organic fraction of the sediments from the basin margin is purely terrestrial and consists mostly of inertinite and reworked terrigenous liptinite indicating oxidative conditions. The dominance of inertodetrinite in the Miocene and of semifusinite in the Pliocene point to a change in the source area or to a higher energy transport or deposition conditions for the Miocene marginal sediments. In the basin interior, the higher content of marine organic matter is due to an oxygen deficiency or anoxic conditions in the bottom waters. Mineral associations indicate complete sulfate reduction and consequent methanogenesis. This is also implied in the hydrocarbon distributions. Periodic oxic conditions lead to a decrease in the marine liptinitic component. In the basin interior, however, the terrigenous fraction is still dominant, implying a continuous influx from the basin margins.The Late Cretaceous to Pliocene sediments are thermally immature (Rm<0.5%, T_max<435 °C).

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Zusammenfassung Die organische Substanz in den Sedimenten der Oberkreide und des Tertiärs der südlichen Schwarzmeerregion ist dem terrestrischen bis marin-terrestrischen Bereich organischer Fazies zuzuordnen. Innerhalb dieses Bereiches weisen die stratigraphischen Abschnitte unterschiedliche organische Faziestypen auf, die auf unterschiedliche, die Akkumulation und den Erhaltungsgrad der organischen Substanz kontrollierende Prozesse zurückzuführen sind.Während des Obercampan-Maastrichtiums und des Paläozäns (fore-arc Becken) wurde organisches Material des Schelf/-hanges in den tieferen oxischen Beckenbereichen resedimentiert. Die rasche Zufuhr und Ablagerung führte zu einem gegenüber den autochthonen Sedimenten höheren Erhaltungsgrad an lipidreichen, terrestrischen Komponenten (Sporinit, Cutinit, Resinit). Die Zunahme an organischem Kohlenstoff mit steigendem Silt-/Tonanteil bei insgesamt niedrigen Kohlenstoffkonzentrationen in den Resedimenten läßt vermuten, daß die Akkumulation organischer Substanz in den Liefergebieten durch terrigene Zufuhr bestimmt wurde und die Akkumulationsbedingungen ungünstig waren.Für das Eozän ist ein erhöhter Eintrag an marinem organischem Material zu verzeichnen, der mit der zunehmenden Verflachung des Ablagerungsraumes (fore-arc Becken) und einer Reduzierung im Sauerstoffgehalt des Bodenwassers (abnehmende Bioturbation) erklärt wird.Für das Miozän und Pliozän (back-arc Becken) ist die organische Fraktion der Ablagerungen des Beckenrandes rein terrestrisch und besteht zum größten Teil aus Inertinit und wieder aufgearbeitetem terrigenem Liptinit, die oxidative Verhältnisse anzeigen. Die Dominanz von Inertodetrinit im Miozän und Semifusinit im Pliozän indiziert eine Änderung im Liefergebiet oder ein höheres Energieniveau beim Transport bzw. im Ablagerungsraum der miozänen Randsedimente. Im Beckeninneren ist ein erhöhter Anteil an mariner organischer Substanz festzustellen, der auf Sauerstoffverarmung oder anoxische Verhältnisse im Bodenwasser zurückgeführt wird. Die Mineralassoziationen in den Sedimenten weisen auf vollständige Sulfatreduktion und nachfolgende Methanogenese hin, die sich auch mit den Kohlenwasserstoffverteilungen nachvollziehen läßt. Periodisch oxische Bedingungen führen zu einer Reduzierung der marin-liptinitischen Komponente. Im Beckeninneren dominiert jedoch auch die terrigene Fraktion (Huminit/Vitrinit, Inertinit), was auf kontinuierliche Zufuhr vom Beckenrand schließen läßt.Die Sedimente der Oberkreide bis Pliozän sind thermisch unreif (Rm<0.5%, T_max<435 °C).

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Résumé La matière organique contenue dans les sédiments du Crétacé supérieur et du Tertiaire de la partie sud de la Mer Noire est à rapporter au domaine de facies organique terrestre à marin-terrestre. La série stratigraphique présente, dans les limites de ce domaine, divers types de facies organiques qui traduisent les divers processus qui régissent l'accumulation et la préservation.Au cours du Campanian supérieur-Maastrichtien, des matériaux organiques provenant du shelf et du talus continental ont été redéposés dans les parties oxygénées plus profondes du bassin. La rapidité du transport et de la sédimentation a entraîné la préservation de composants terrestres riches en lipides (sporonite, cutinite, résinite), dans une mesure plus élevée que dans les sédiments autochtones. L'augmentation de la teneur en carbone organique corrélative à celle de la fraction fine (boue et silt), de même que la faible concentration en carbone des sédiments allochtones indique que, dans la région-source, l'accumulation de matières organiques était régie par un afflux terrigène et que les conditions d'accumulation n'étaient pas favorables.A l'Eocène (bassin d'avant-arc) le contenu en matière organique marine est plus élevé, ce qui s'explique par la diminution progressive de la profondeur et par la réduction de la teneur en oxygène des eaux du fond (bioturbation réduite).Au Miocène et au Pliocène (bassin d'arrière-arc), la fraction organique des sédiments de la bordure du bassin est purement terrestre et consiste principalement en inertinite et en liptinite terrigène remaniée, ce qui indique des conditions oxydantes. La prédominance d'inertodétrinite au Miocène et de semifusinite au Pliocène indique soit une source différente, soit un transport ou un dépôt dans les conditions de plus haute énergie des sédiments miocènes marginaux. Vers l'intérieur du bassin, le contenu plus élevé en matière organique marine est dû à une déficience en oxygène ou à des conditions anoxiques dans les eaux de fond. Les associations minérales indiquent une réduction complète des sulfates et en conséquence une méthanogenèse, ce qui ressort également de la distribution des hydrocarbures. Des conditions oxydantes périodiques provoquent une diminution du composant liptinitique marin. Dans l'intérieur du bassin, toutefois, la fraction terrigène reste dominante, ce qui implique un afflux continu depuis les marges du bassin.Les sédiments d'âge crétacé supérieur à pliocène sont thermiquement immatures (Rm<0,5%; Tmax<435 °C).

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, , - . , , . - , . , ( , , ), . , , . , (force-arc Basin) ( ). (back-arc Basin) , . , , . , , . , . . ( , ), . : (Rm<0,5 %; T_max<435° ).

     

Amber in sediments of the Baltic Sea and the Curonian and Kaliningrad bays

In the Kaliningrad region, sediments of the Upper Eocene Prussian Formation accommodates the world’s largest explored amber deposits (up to 90% of world reserves). They are also partly tracked on the shelf of the southeastern Baltic region and subjected to bottom erosion, which is particularly intense during storm activity in the sea. Recent alongshore currents transport amber fragments over great distances, resulting in the formation of new (secondary) amber-bearing deposits in Holocene sediments in some places. The paper addresses formation conditions of such deposits. Catastrophic events, such as hydrospheric floods provoked by the regional glaciation, meteorite falls, and earthquakes (tsunamis), are of great significance.     

Partitioning of heavy metals in surface Black Sea sediments

Bulk heavy metal (Fe, Mn, Co, Cr, Ni, Cu, Zn and Pb) distributions and their chemical partitioning, together with TOC and carbonate data, were studied in oxic to anoxic surface sediments (0–2 cm) obtained at 18 stations throughout the Black Sea. TOC and carbonate contents, and available hydrographic data, indicate biogenic organic matter produced in shallower waters is transported and buried in the deeper waters of the Black Sea. Bulk metal concentrations measured in the sediments can be related to their geochemical cycles and the geology of the surrounding Black Sea region. Somewhat high Cr and Ni contents in the sediments are interpreted to reflect, in part, the weathering of basic-ultrabasic rocks on the Turkish mainland. Maximum carbonate-free levels of Mn (4347 ppm), Ni (355 ppm) and Co (64 ppm) obtained for sediment from the shallow-water station (102 m) probably result from redox cycling at the socalled ‘Mn pump zone’ where scavenging-precipitation processes of Mn prevail. Chemical partitioning of the heavy metals revealed that Cu, Cr and Fe seem to be significantly bound to the detrital phases whereas carbonate phases tend to hold considerable amounts of Mn and Pb. The sequential extraction procedures used in this study also show that the metals Fe, Co, Ni, Cu, Zn and Pb associated with the ‘oxidizable phases’ are in far greater concentrations than the occurrences of these metals with detrital and carbonate phases. These results are in good agreement with the recent studies on suspended matter and thermodynamic calculations which have revealed that organic compounds and sulfides are the major metal carriers in the anoxic Black Sea basin, whereas Fe-Mn oxyhydroxides can also be important phases of other metals, especially at oxic sites. This study shows that, if used with a suitable combination of the various sequential extraction techniques, metal partitioning can provide important information on the varying geological sources and modes of occurrence and distribution of heavy metals in sediments, as well as, on the physical and chemical conditions prevailing in an anoxic marine environment.     

Industrialization affects heavy metal and carbon isotope concentrations in recent Baltic Sea sediments

Recent sediment cores of the western Baltic Sea were analyzed for heavy metal and carbon isotope contents. The sedimentation rate was determined from radiocarbon dates to be 1.4 mm/yr. The ‘recent age’ of the sediment was about 850 yr. Within the upper 20 cm of sediment, certain heavy metals became increasingly enriched towards the surface; Cd, Pb, Zn and Cu increased 7-, 4-, 3- and 2-fold, respectively, whereas Fe, Mn, Ni and Co remained unchanged. Simultaneously, the radiocarbon content decreased by about 14 per cent. The enrichment in heavy metals as well as the decrease in the ¹⁴C-concentration during the last 130 ± 30yr parallels industrial growth as reflected in European fossil fuel consumption within that same period of time. The near-surface sediments are affected by residues released from fossil fuels at the rate of about 30 g/m² yr for the past two decades. The residues have a pronounced effect on the heavy metal and carbon isotope composition of the most Recent sediments allowing estimates to be made for sedimentation, erosion and heavy metal pollution.     

The West Bornholm basin in the Baltic Sea: geological structure and Quaternary sediments

KÖgler, F.-C. & Larsen, B. 1979 03 01: The West Bornholm basin in the Baltic Sea: geological structure and Quaternary sediments. Boreas . Vol. 8, pp. 1–22. Oslo. ISSN 0300–9483.
The West Bornholm basin is an approx. 1000 km² subbasin of the Bornholm basin just north of Bornholm. The basin has been mapped by acoustic profiling and sampling of the sea floor. The basin is eroded down into Mesozoic sediments which are downfaulted between basement horsts in the Fennoscandian Border Zone. The development of the Quaternary morphology is illustrated by maps of the surface of the bedrock, the glacial landscape beneath the varved clays, the recent topography combined with isopach maps of late Glacial and Holocene formations. Quaternary formations are defined and described. The brown, very fine grained varved clay is deposited as a conformable cover on the substratum. It is probably deposited from suspensions carried in the whole water body, while turbidity currents were of minor importance. The recent sedimentary environment is an example of a restricted, but not totally anoxic basin. The recent sediment is chiefly mud rich in organic matter (ca. 4% C_org). According to a rough estimate, the long-term mean sedimentation rate of organic carbon is 6 g/m²/year.     

Black shales and other sediments with high organic matter contents in Phanerozoic climatic cycles: Communication 2. Black shales during the Pangea existence

According to recent concepts, the Earth surface was permanently transformed during its geological history. Some stages of its evolution were marked by the convergence of separate continental blocks to result in the formation of supercontinents, which resisted successfully centrifugal processes. Other stages were characterized by the opposite tendency: after their long existence, the supercontinents became disintegrated into several large and small blacks, the motion of which was accompanied by opening of new sea basins and closure of former basins with the oceanic crust. The second half of the Paleozoic was marked by amalgamation of large continental blocks. In the Devonian, collision between Laurentia and Baltica culminated in the formation of the Euroamerica continent. After the closure of the Ural paleocean in the terminal Carboniferous–initial Permian, it was united with the Siberian and Kazakhstan continental blocks. These events provided the prerequisites for the formation of a new supercontinent (Pangea), which acquired its final configuration at the end of the Permian. One of its segments located mainly south of the equator included Gondwana. Another segment located northward included Euroamerica, Kazakhstan, Siberian, and two China continental blocks. During its geological history, Pangea suffered many dramatic events including several extinctions of organisms. The most significant event took place in the terminal Permian–initial Triassic and at the transition between the Triassic and Jurassic periods.     

MIS 3 marine and lacustrine sediments at Kriegers Flak,southwestern Baltic Sea

Anjar, J., Larsen, N. K., Björck, S., Adrielsson, L. & Filipsson, H. L. 2010: MIS 3 marine and lacustrine sediments at Kriegers Flak, southwestern Baltic Sea. Boreas, 10.1111/j.1502‐3885.2010.00139.x. ISSN 0300‐9483. Sediment cores from the Kriegers Flak area in the southwestern Baltic Sea show a distinct lithological succession, starting with a lower diamict that is overlain by a c. 10 m thick clay unit that contains peat, gyttja and other organic remains. On top follows an upper diamict that is inter‐layered with sorted sediments and overlain by an upward‐coarsening sequence with molluscs. In this paper we focus on the clay unit, which has been subdivided into three subunits: (A) lower clay with benthic foraminifera and with diamict beds in the lower part; (B) thin beds of gyttja and peat, which have been radiocarbon‐dated to 31–35 ¹⁴C kyr BP (c. 36–41 cal. kyr BP); and (C) upper clay unit. Based on the preliminary results we suggest the following depositional model: fine‐grained sediments interbedded with diamict in the lower part (subunit A) were deposited in a brackish basin during a retreat of the Scandinavian Ice Sheet, probably during the Middle Weichselian. Around 40 kyr BP the area turned into a wetland with small ponds (subunit B). A transgression, possibly caused by the damming of the Baltic Basin during the Kattegat advance at 29 kyr BP, led to the deposition of massive clay (subunit C). The data presented here provide new information about the paleoenvironmental changes occurring in the Baltic Basin following the Middle Weichselian glaciation.     

Iron isotope variations in Holocene sediments of the Gotland Deep, Baltic Sea

Holocene sediments from the Gotland Deep basin in the Baltic Sea were investigated for their Fe isotopic composition in order to assess the impact of changes in redox conditions and a transition from freshwater to brackish water on the isotope signature of iron. The sediments display variations in δ⁵⁶Fe (differences in the ⁵⁶Fe/⁵⁴Fe ratio relative to the IRMM-14 standard) from −0.27 ± 0.09‰ to +0.21 ± 0.08‰. Samples deposited in a mainly limnic environment with oxygenated bottom water have a mean δ⁵⁶Fe of +0.08 ± 0.13‰, which is identical to the mean Fe isotopic composition of igneous rocks and oxic marine sediments. In contrast, sediments that formed in brackish water under periodically euxinic conditions display significantly lighter Fe isotope signatures with a mean δ⁵⁶Fe of −0.14 ± 0.19‰. Negative correlations of the δ⁵⁶Fe values with the Fe/Al ratio and S content of the samples suggest that the isotopically light Fe in the periodically euxinic samples is associated with reactive Fe enrichments and sulfides. This is supported by analyses of pyrite separates from this unit that have a mean Fe isotopic composition of −1.06 ± 0.20‰ for δ⁵⁶Fe. The supply of additional Fe with a light Fe isotopic signature can be explained with the shelf to basin Fe shuttle model. According to the Fe shuttle model, oxides and benthic ferrous Fe that is derived from dissimilatory iron reduction from shelves is transported and accumulated in euxinic basins. The data furthermore suggest that the euxinic water has a negative dissolved δ⁵⁶Fe value of about −1.4‰ to −0.9‰. If negative Fe isotopic signatures are characteristic for euxinic sediment formation, widespread euxinia in the past might have shifted the Fe isotopic composition of dissolved Fe in the ocean towards more positive δ⁵⁶Fe values.     

Origin and formation pathways of kerogen-like organic matter in recent sediments off the Danube delta (northwestern Black Sea)

The chemical structure, source(s), and formation pathway(s) of kerogen-like organic matter (KL) were investigated in recent sediments from the northwestern Black Sea, off the Danube delta. Three sections from a sediment core collected at the mouth of the Sulina branch of the delta, under an oxic water column, were examined: S₀ (0–0.5 cm bsf), S₁₀ (10–13 cm bsf), and S₂₀ (20–25 cm bsf). The bulk geochemical features of these sediments (total organic carbon, organic C/N atomic ratio, δ¹³C_org) were determined. Thereafter, KL was isolated from the samples, as the insoluble residue obtained after HF/HCl treatment. KL chemical composition was investigated via spectroscopic (FTIR, solid state ¹³C and ¹⁵N NMR) and pyrolytic (Curie point pyrolysis–gas chromatography–mass spectrometry) methods, and the morphological features were examined by scanning and transmission electron microscopy. Similar morphological features and chemical composition were observed for the three KLs and they suggested that the selective preservation of land-plant derived material as well as of resistant aliphatic biomacromolecules (probably derived from cell walls of freshwater microalgae) was the main process involved in KL formation. Besides, some melanoidin-type macromolecules (formed via the degradation-recondensation of products mainly derived from proteinaceous material) and/or some encapsulated proteins also contributed to the KL chemical structure.     

Free,esterified and residual bound sterols in Black Sea Unit I sediments

Detailed compositional data for the sterols isolated from a surface, Unit I, sediment from the Black Sea are reported. A procedure based on digitonin precipitation has been used to separate the more abundant free sterols from those occurring in esterified forms. Saponification of the solvent extracted sediment residue liberated only a small quantity of residual bound sterols in contrast to studies of other sediments. 4-Methylsterols are much more abundant than 4-desmethylsterols in both the free and esterified sterol fractions which we attribute to a major dinoflagellate input, as in deeper Unit II sediment. The desmethylsterol fraction appears to derive from a variety of sources including dinoflagellates, coccolithophores, diatoms, terrigenous detritus and perhaps invertebrates. 5α(H)-Stanols are particularly abundant in the free sterol fraction. An analysis of the stanol/stenol ratios suggests that the 4-desmethyl-5α(H)-stanols are the result of specific microbial reductions of Δ⁵-sterols and/or the reflection of a contribution of stanol containing source organisms.     

Adsorption of short-chain organic acids onto nearshore marine sediments

The adsorption of acetate, butyrate, lactate, and stearate was measured using a clastic mud from Cape Lookout Bight N.C. (CLB), a lateritic muddy sand from Kahana Stream, Oahu, Hawaii (KS), and a fine carbonate sand from Waimanalo Beach, Oahu, (WB). Partition coefficients (K_d, moles adsorbed per g of solid phase/moles dissolved per ml of porewater) ranged from 10^2.3 to ≤10^−3.0, and displayed the following trends: CLB > KS > WB, and stearate > acetate ∼- butyrate > lactate. The percent adsorption of the sediment organic acid pools showed similar trends: stearate, 99%; acetate, 9–23%; butyrate, 5–23%; lactate, ≤0.2–7%. These results reflected the relatively nonpolar nature of the sand surfaces in WB and KS sediments, and the polarities of the organic acids. K_d was approximately constant for each organic acid-sediment combination over a dissolved organic acid concentration range of 10⁷, using concentrations between 1M and 10⁻¹⁴ M. This constancy over a wide porewater concentration range suggested that adsorption was not limited by the availability of surface adsorption sites.     

New finds of older quaternary mollusks in sediments of the Black Sea

Doklady Earth Sciences -     

Controls on the age of vascular plant biomarkers in Black Sea sediments

Transfer of organic carbon (OC) from the terrestrial to the oceanic carbon pool is largely driven by riverine and aeolian transport. Before transport, however, terrigenous organic matter can be retained in intermediate terrestrial reservoirs such as soils. Using compound-specific radiocarbon analysis of terrigenous biomarkers their average terrestrial residence time can be evaluated.Here we show compound-specific radiocarbon (¹⁴C) ages of terrigenous biomarkers and bulk ¹⁴C ages accompanied by geochemical proxy data from core top samples collected along transects in front of several river mouths in the Black Sea. ¹⁴C ages of long chain n-alkanes, long chain n-fatty acids and total organic carbon (TOC) are highest in front of the river mouths, correlating well with BIT (branched and isoprenoid tetraether) indices, which indicates contribution of pre-aged, soil-derived terrigenous organic matter. The radiocarbon ages decrease further offshore towards locations where organic matter is dominated by marine production and aeolian input potentially contributes terrigenous organic matter. Average terrestrial residence times of vascular plant biomarkers deduced from n-C₂₉₊₃₁ alkanes and n-C₂₈₊₃₀ fatty acids ages from stations directly in front of the river mouths range from 900 ± 70 years to 4400 ± 170 years. These average residence times correlate with size and topography in climatically similar catchments, whereas the climatic regime appears to control continental carbon turnover times in morphologically similar drainage areas of the Black Sea catchment. Along-transect data imply petrogenic contribution of n-C₂₉₊₃₁ alkanes and input via different terrigenous biomarker transport modes, i.e., riverine and aeolian, resulting in aged biomarkers at offshore core locations. Because n-C₂₉₊₃₁ alkanes show contributions from petrogenic sources, n-C₂₈₊₃₀ fatty acids likely provide better estimates of average terrestrial residence times of vascular plant biomarkers. Moreover, sedimentary n-C₂₈ and n-C₃₀ fatty acids appear clearly much less influenced by autochthonous sources than n-C₂₄ and n-C₂₆ fatty acids as indicated by increasing radiocarbon ages with increasing chain-length and are, thus, more representative as vascular plant biomarkers.     

Mollusks from the lower quaternary Chauda sediments of the Black Sea

The analysis of paleontological remains in many samples from the Lower Quaternary Chauda sediments drilled and cored on the Bulgarian shelf of the Black Sea revealed widespread mollusks of the genera Didacna and Dreissena (Didacna tschaudae guriana, D. tschaudae, D. pleistopleura, D. crassa guriensis, Dreissena rostriformis tschaudae, D. rostriformis abchasica) accompanied by reworked Neogene representatives of the genus Digressodacna. In numerous places of a continental slope and an adjacent deep-sea depressions near Crimea and Caucasus the similar mollusc assemblage is described in the redeposited state for the first time. The composition of palynological spectra and diatom assemblages in shelf sediments indicates climate changes during the Chaudan period. The Chaudan mollusk fauna from the Black Sea sediments, which is lacking Caspian Bakuan species characteristic of the Chauda stratotype, is compositionally close to the mollusk assemblage from basal layers of the Chauda Horizon in the Guriya area of Georgia (“Gurian” Chauda). These data imply repeated changes in the level of the Chaudan basin between present-day isobaths of −30...−50 to −140 m.     

Heavy-metal pollution of sediments from the Polish exclusive economic zone,southern Baltic Sea

Analysis of 59 surface sediment samples from the Polish exclusive economic zone (EEZ) shows that Szczecin Lagoon sediments are the most polluted by heavy metals and that the degree of heavy-metal pollution decreases substantially on passing from the Szczecin Lagoon to the Pomeranian Bay and the inner shelf area and then on passing to the Bornholm Deep and Słupsk Furrow. Heavy-metal pollution in the sediments of the western part of the Polish EEZ therefore appears to follow the dispersion of the Oder River. Fluffy material from the Oder estuary appears to be the main source of heavy metals in the muddy sediments of the Bornholm Deep. The formation of sulphides is therefore not the principal factor controlling the enrichment of heavy metals in the sediments of this anoxic basin, although it may be responsible for the uptake of Mo, Sb and As. Two main factors control the distribution of the rare earth elements (REE) in sediments of the Polish EEZ: the input of Fe-organic colloids from rivers and the presence of detrital material in the sediments.