ALBERT

Description: Two foraminiferal assemblages are observed in surface sediments of the Elbe estuarv. an Elphidium excavatum assemblaae and an Ahmonia/Protelphidium assemblage. They are the result of test-size sorting in accordance to the grain size of the sediments. These assemblages of mainly empty tests differ basically from the living population, which is dominated exclusively by E. excavatum. The average test size is decreasing when advancing from the Open sea into the estuary and the living fauna disappears near the entrance of the Kiel Canal. In the dead assemblage the diversity is distinctively higher and the average test size varies with the grain size of the sediment. The assemblages found in plankton tows are nearly identical with those in corresponding bottom samples. This indicates the distribution pattern to be caused by transport in currents (mainly in suspension). This type of foraminiferal assemblages characterize macro- and mesotidal estuaries and might indicate a high tidal range when observed in sediments of fossil estuaries.

Description: The Indo-Pakistan Continental Margin represents an extreme habitat for benthic foraminifera since (1) high fluxes of organic matter offer a high food supply, (2) an intensified oxygen minimum Zone (OMZ) develops from the base of the euphotic Zone to water depths over 1000 m and (3) the monsoon causes seasonal oscillations within the biogeochemical cycle. At three stations from the uppermost (233 m), the central (658 m) and the deeper part (902 m) of the OMZ, living benthic foraminiferal assemblages were analyzed within the uppermost 10 cm of the sediment column. The ecologic structure of foraminiferal faunas is characterized by high abundances at the sediment surface and a rapid decrease within the uppermost 2 cm of the sediment column. Despite dysoxic to suboxic bottom-water conditions, stained benthic foraminifera occurred in all cores down to the base of the sampled interval. High surface abundances, a high dominance by few endobenthic calcareous taxa and a low diversity, which may result from specific physiological adaptations to almost anoxic conditions and the absence of predators, are recognized in the central part of the OMZ. The upper and lower margins of the OMZ are characterized by higher diversities and lower abundances. The shallowest part of the OMZ is dominated by calcareous foraminifera, whereas agglutinated species are the most common taxa in the deeper part. Comparisons with previous studies show that benthic foraminiferal assemblages, that are influenced by seasonal oscillations controlling food supply and/or the availability of oxygen, show variations in faunal density and species composition. Since there is strong evidence that oxygen is not a limiting factor for some taxa, it seems more likely that the distribution pattern of benthic foraminifera is preferentially controlled by trophic conditions.

Description: This data collection presents sediment core descriptions and age models of sediment cores from the South China Sea.

Description: Ice core records demonstrate a glacial-interglacial atmospheric CO2 increase by ~100 ppm, while 14C calibration efforts document a strong decrease in atmospheric 14C concentration during this period. A calculated transfer of ~530 Gt of 14C depleted carbon is required to produce the deglacial coeval rise of carbon in the atmosphere and terrestrial biosphere. This amount is usually ascribed to oceanic carbon release, although the actual mechanisms remained elusive, since an adequately old and carbon-enriched deep-ocean reservoir seemed unlikely. Here we present a new, though still fragmentary, ocean-wide d14C dataset showing that during the Last Glacial Maximum (LGM) and Heinrich Stadial 1 (HS-1) the maximum 14C age difference between ocean deep waters and the atmosphere exceeded the modern values by up to 1500 14C yr, in the extreme reaching 5100 14C yr. Below 2000 m depth the 14C ventilation age of modern ocean waters is directly linked to the concentration of dissolved inorganic carbon (DIC). We propose as working hypothesis that the modern regression of DIC vs d14C also applies for LGM times, which implies that a mean LGM aging by ~600 14C yr corresponded to a global rise of ~85-115 µmol DIC/kg in the deep ocean. Thus, the prolonged residence time of ocean deep waters may indeed have made it possible to absorb an additional ~730-980 Gt DIC, one third of which possibly originated from intermediate waters. We also infer that LGM deep-water O2 dropped to suboxic values of 〈10µmol/kg in the Atlantic sector of the Southern Ocean, possibly also in the subpolar North Pacific. The outlined deglacial transfer of the extra aged, deep-ocean carbon to the atmosphere via the dynamic ocean-atmosphere carbon exchange would be sufficient to account for two trends observed, (1) for the increase in atmospheric CO2 and (2) for the 190-permil drop in atmospheric d14C during the so-called HS-1 'Mystery Interval', when atmospheric 14C production rates were largely constant.

Description: Sediment cores were recovered from the New Ireland Basin, east of Papua New Guinea, in order to investigate the late Quaternary eruptive history of the Tabar-Lihir-Tanga-Feni (TLTF) volcanic chain. Foraminifera d18O profiles were matched to the low-latitude oxygen isotope record to date the cores, which extend back to the early part of d18O Stage 9 (333 ka). Sedimentation rates decrease from 〉10 cm/1000 yr in cores near New Ireland to ~2 cm/1000 yr further offshore. The cores contain 36 discrete ash beds, mostly 1-8 cm thick and interpreted as either fallout or distal turbidite deposits. Most beds have compositionally homogeneous glass shard populations, indicating that they represent single volcanic events. Shards from all ash beds have the subduction-related pattern of strong enrichment in the large-ion lithophile elements relative to MORB, but three distinct compositional groups are apparent: Group A beds are shoshonitic and characterised by 〉1300 ppm Sr, high Ce/Yb and high Nb/Yb relative to MORB, Group B beds form a high-K series with MORB-like Nb/Yb but high Ce/Yb and well-developed negative Eu anomalies, whereas Group C beds are transitional between the low-K and medium-K series and characterised by flat chondrite-normalised REE patterns with low Nb/Yb relative to MORB. A comparison with published data from the TLTF chain, the New Britain volcanic arc and backarc including Rabaul, and Bagana on Bougainville demonstrates that only Group A beds share the distinctive phenocryst assemblage and shoshonitic geochemistry of the TLTF lavas. The crystal- and lithic-rich character of the Group A beds point to a nearby source, and their high Sr, Ce/Yb and Nb/Yb match those of Tanga and Feni lavas. A youthful stratocone on the eastern side of Babase Island in the Feni group is the most probable source. Group A beds younger than 20 ka are more fractionated than the older Group A beds, and record the progressive development of a shallow level magma chamber beneath the cone. In contrast, Group B beds represent glass-rich fallout from voluminous eruptions at Rabaul, whereas Group C beds represent distal glass-rich fallout from elsewhere along the volcanic front of the New Britain arc.

Description: We here present a compilation of planktic and benthic 14C reservoir ages for the Last Glacial Maximum (LGM) and early deglacial from 11 key sites of global ocean circulation in the Atlantic and Indo-Pacific Ocean. The ages were obtained by 14C plateau tuning, a robust technique to derive both an absolute chronology for marine sediment records and a high-resolution record of changing reservoir/ventilation ages (Delta14C values) for surface and deep waters by comparing the suite of planktic 14C plateaus of a sediment record with that of the atmospheric 14C record (Sarnthein et al., 2007, doi:10.1029/173GM13). Results published thus far used as atmospheric 14C reference U/Th-dated corals, the Cariaco planktic record, and speleothems (Fairbanks et al., 2005, doi:10.1016/j.quascirev.2005.04.007; Hughen et al., 2006, doi:10.1016/j.quascirev.2006.03.014; Beck et al., 2001, doi:10.1023/A:1008175728826). We have now used the varve-counted atmospheric 14C record of Lake Suigetsu terrestrial macrofossils (Ramsey et al., 2012, doi:10.1126/science.1226660) to recalibrate the boundary ages and reservoir ages of the seven published records directly to an atmospheric 14C record. In addition, the results for four new cores and further planktic results for four published records are given. Main conclusions from the new compilation are: (1) The Suigetsu atmospheric 14C record on its varve counted time scale reflects all 14C plateaus, their internal structures and relative length previously identified, but implies a rise in the average 14C plateau age by 200-700 14C yr during LGM and early deglacial times. (2) Based on different 14C ages of coeval atmospheric and planktic 14C plateaus, marine surface water Delta14C may have temporarily dropped to an equivalent of ~0 yr in low-latitude lagoon waters, but reached 〉2500 14C yr both in stratified subpolar waters and in upwelled waters such as in the South China Sea. These values differ significantly from a widely assumed constant global planktic Delta14C value of 400 yr. (3) Suites of deglacial planktic Delta14C values are closely reproducible in 14C records measured at neighboring core sites. (4) Apparent deep-water 14C ventilation ages (equivalents of benthic Delta14C), deduced from the sum of planktic Delta14C and coeval benthic-planktic 14C differences, vary from 500 up to 〉5000 yr in LGM and deglacial ocean basins.

Description: Geothermal waters with maximum temperatures of 103°C emanate from two sublacustrine hot spring areas which are located in the northem part of Lake Tanganyika (East African Riftsystem). The hydrothermalism leads to the formation of crust- and stockwork-like massive sulfide bodies on the lake bottom to a maximum water depth of 46 m. These geothermal vent areas were investigated and sampled during the German-French TANGANYDRO-campaign in 1991. The aim of this work is to characterize the mineralogy and geochemistry of these sulfides and to reconstruct their genesis. Mineralogical methods that have been used inc1ude scatter electron microscopy (SEM), polarization microscopy, and X-ray diffraction analysis. The geochemical methods inc1ude electron microprobe analysis (EMP) and inductively coupled plasma mass spectrometry (ICP-MS) for the major and trace elements and sulfur isotope measurements in order to determine the d34S-values of the samples. The samples consist exc1usively of iron sulfides. The dominant minerals are marcasite and melnicovite with subordinate pyrite. All samples show collophorm textures indicating their origin from gel-like precursors. They are characterized by high contents of As (up to 3.4 wt%), Sb (up to 0.6 wt%) and Tl (up to 2.6 wt%). Low d34S-values in the range of -11.6 %0 to +2.4 %0 (rel. PDB) indicate bacterial sulfur fractionation. The crystallization of the gel-like precursor leads to the formation of marcasite and pyrite with melnicovite as a transitional phase. Pyrite is formed by the replacement of either melnicovite or marcasite. This mechanism accords to previously postulated models for the formation of iron sulfides in low temperature (〈100°C) hydrothermal systems. A significant sulfur isotope fractionation (increase of d34S) has been observed during the replace- ment of melnicovite by the mature phases marcasite and pyrite. Biogenie impact on the sulfide formation is indicated by low Co/Ni-ratios (〈1), the negative d34S-values and the occurrence of framboidal pyrite. The metabolism of sulfur oxidizing and sulphate reducing bacteria at the wall rock of the vents and in the spring waters is suggested to actively influence the setting of specific pH-values required for the formation of either marcasite or pyrite. The altemating pyrite-marcasite layers are the result of fluctuations in the productivity of those bacteria, which may depend on seasonal variations or changing nutrient support.

Description: Based on foraminiferal transfer-functions, the distribution patterns of early Holocene sea- surface temperatures (SST) were studied, using the information from 154 deep-sea sediment cores (92 Atlantic, 62 Indian Ocean and Western Pacific). For our reconstruction, we employed a uniform high-resolution, AMS 14C-calibrated d18O-chronology, converted to a calendar timescale, and the new SIMMAX-Transfer-Technique in the Atlantic Oceans (Pflaumann et al. in press). The short-term SST fluctuations during the last 30,000 years are not directly related to the relatively slow changes in insolation during this period, reaching maximum seasonal deviations from modern values at approximaterly 11,000 years B.P. Although seasonal changes in solar radiation must have triggered global warming to the modern, interglacial mode, there is little evidence for linear warming and heat transport by ocean currents. The SIMMAX-temperature estimates indicate an early and rapid warming in the Equatorial Atlantic, as well as in the eastern North Atlantic, where modern SSTs were reached for a short time between 20,000 to 16,000 kalendar-years B.P. On a core transect crossing the Island-Faroer Ridge, the history of high-latitude warming along the eastern margins of the big North Atlantic gyres was reconstructed. Prior to the Younger Dryas cold interval (12,000 kalendar years), SSTs of the Norwegian Greenland Sea were still at glacial levels. After the Younger Dryas, there was a rapid inflow of warm Atlantic surface waters into the Norwegian-Greenland basins. In the northern Indian Ocean, the SST-patterns were totally different from the Atlantic during the last 20,000 years. Temperature variations did not exeed 2-3°C in the open ocean. During the Last Glacial Maximum (18,000 years B.P.), temperatures were higher than today whereas they were lowest during the early Holocene. This was caused by changes in the monsoon-induced oceanic upwelling intensity. At this time trade winds off Northwest Africa were also stronger, related to the stronger seasonal constrasts in insolation. Perhaps, the atmospheric circulation was generally enhanced at 10,000 years B.P. High-resolution SST-records from the southern Ocean (Pichon et al. 1992) indicate a slight asymmetry between the two Hemispheres. At 10,000 years B.P, SSTs were 1-2°C higher than today in the southern Indian Ocean. At the same time, somewhat colder SSTs imply still cool, boreal conditions in the middle and high latitudes of the northern hemisphere. Although SSTs of both seasons are only little different from the modern patterns, differences in the direction and strength of the major ocean currents are indicated by internally consistent positive and negative temperature anomaly fields. They were found in both, in the lower and in the high latitudes. The distribution of the anomalies in the North Atlantic further suggests, that the remnants of the ice shields still had a strong impact on the SST distribution. The particulary stronger insolation in the high northern latitudes during summers had nearly no influence. Finally, many details in the SST fluctuations and in the distribution of temperature anomalies imply a more dynamic surface circulation than today which may be the most characteristic difference between the early Holocene and modern surface ocean.

Description: The Sunda Shelf represents one of the largest tropical shelf areas in the world. Its broad extension, the very low gradient, and the tectonical stability offer excellent conditions for a reconstruction of the exposure and flooding history during the last glacial cycle. A high fluvial input dominated this siliciclastic deposystem over long time intervals. The proximal part of the transect of the research cruise Sonne-115 covers the riverine structures of the ancient North Sunda River ('Molengraaff' River) from -70 to -126 m modern water depth. The aim of the study presented here was to analyse the stratigraphic architecture of the Sunda Shelf during the last 50 kyr, to develop a high-resolution sea-level curve, as well as to reconstruct the flooding history of this part of the world. The facies types examined in 36 sediment cores were classified by sedimentological and geochemical methods. 80 AMS-14C datings and additional fractionation measurement led to a high-resolution age determination. A shallow-seismic survey along and crosswise to the transect illustrated large- to medium-scale sediment structures. Eleven facies types were identified and related to the paleo-shoreline. They extend from terrestrial and coastline deposits to full-marine environments and were classified into five groups along the transect, which contain distinct local facies successions. The sea-level rise from 21 to 11 cal. kyr BP was determined by dating of plant remnants from the intertidal zone, following the retrograde migrating paleo-coastline. During lowstand, sea-level dropped at about -120 m. A conspicuous phase of the subsequent rise between 14.6 and 14.3 cal. kyr BP corresponding to meltwater pulse 1A was documented the first time and indicated as much as 16 m. In response to the sea-level changes during the last 50 kyr, characteristic processes formed the deposits and changed drastically several times until the terrigenous supply starved at about 11 kyr BP. Most remarkable were incised valley fills, which preserved deposits of the transgressive phase. A sequence-stratigraphic interpretation classified the deposits into three systems tracts and indicates, that three major factors controlled the depositional history: sediment input, physiography, and sea-level fluctuations. The specific modification of these factors in comparison to the general model was related to the asymmetry of the sea-level fall and rise and the extreme morphological conditions on the Sunda Shelf. Nevertheless, hiatuses of several thousand years and massive erosion activity were almost always predominantly affecting and strongly reducing the original sediment thickness.