Sea surface temperatures derived from alkenones from Late Quaternary sediments of the East Equatorial South Atlantic

Angola Basin and Walvis Ridge records of past sea surface temperatures (SST) derived from the alkenone Uk 37 index are used to reconstruct the surface circulation in the east equatorial South Atlantic for the last 200,000 years. Comparison of SST estimates from surface sediments between 5° and 20°S with modern SST data suggests that the alkenone temperatures represent annual mean values of the surface mixed layer. Alkenone-derived temperatures for the warm climatic maxima of the Holocene and the penultimate interglacial are 1 to 4°C higher than latest Holocene values. All records show glacial to interglacial differences of about 3.5°C in annual mean SST, which is about 1.5°C greater than the difference estimated by CLIMAP (1981) for the eastern Angola Basin. At the Walvis Ridge, significant SST variance is observed at all of the Earth's orbital periodicities. SST records from the Angola Basin vary predominantly at 23- and 100-kyr periodicities. For the precessional cycle, SST changes at the Walvis Ridge correspond to variations of boreal summer insolation over Africa and lead ice volume changes, suggesting that the east equatorial South Atlantic is sensitive to African monsoon intensity via trade-wind zonality. Angola Basin SST records lag those from the Walvis Ridge and the equatorial Atlantic by about 3 kyr. The comparison of Angola Basin and Walvis Ridge SST records implies that the Angola-Benguela Front (ABF) (currently at about 14-16°S) has remained fairly stationary between 12° and 20°S (the limits of our cores) during the last two glacial-interglacial cycles. The temperature contrast associated with the ABF exhibits a periodic 23-kyr variability which is coherent with changes in boreal summer insolation over Africa. These observations suggest that surface waters north of the present ABF have not directly responded to monsoon-modulated changes in the trade-wind vector, that the central field of zonally directed trades in the southern hemisphere was not shifted or extended northward by several degrees of latitude during glacials, and that a cyclonic gyre circulation has existed in the east equatorial South Atlantic over the last 200,000 years. This scenario contradicts former assumptions of glacial intensification of the Benguela Current into the eastern Angola Basin and increased coastal upwelling off Angola.

Pollen abundance in Late Quaternary sediment cores off West Africa

The pollen record of three marine late Quaternary cores off Senegal shows a juxtaposition of Mediterranean, Northern Saharan, Central Saharan elements, which are considered transported by the trade winds from a winter-rainfall area, and Sahelian, Soudanese, Soudano-Guinean elements, considered transported both by winds and mostly by the Senegal River, and coming from the monsoonal, summer tropical rainfall area of southern West Africa. Littoral vegetation is either the edaphically dry and saline Chenopodiaceae from sebkhas at the time of the main regression, or the warm tropical humid mangrove with Rhizophora during the humid optimum period. Four stratigraphic zones reflect, from basis to top: Zone 4. A semi-arid period with a balanced pollen input. Zone 3. A very arid period with the disappearance of monsoonal pollen, probably from the disappearance of the Senegal River, a very saline littoral plain with Chenopodiaceae, a larger input of northern Saharan pollen from intensified trade winds. Zone 2. A quite humid period, much more so than today, very suddenly established, with a northward extension of the monsoonal areas, a rich littoral mangrove, and weakening of the trade winds. Zone l. A slow and steady evolution toward the present semi-humid conditions with regression of the mangrove, and of the monsoonal areas toward the south. Tentative datations and correlations with the Tchad area suggested: zone 4: 22,500 to 19,000 years BP; zone 3: 19,000 to 12,500 years BP; zone 2: 12,500 to 5,500 years BP; zone 1: 5,500 years BP to top of core. Dinoflagellate cysts display a tropical assemblage with mostly estuarine neritic elements and also a weak oceanic component, mostly in the lower slope core 47. Cosmopolitan taxa dominate the assemblage and only a few species point to more specialized environments. Quantitative variations of the assemblage are the basis of stratigraphy which is not similar to the pollen stratigraphy, and an inshore-outshore gradient has to be taken into account to correlate the three cores.

The late Pliocene pollen record of ODP Site 108-658 off Cape Blanc, Atlantic Ocean

A 200 m long marine pollen record from ODP Site 658 (21°N, 19°W) reveals cyclic fluctuations in vegetation and continental climate in northwestern Africa from 3.7 to 1.7 Ma. These cycles parallel oxygen isotope stages. Prior to 3.5 Ma, the distribution of tropical forests and mangrove swamps reached Cape Blanc, 5°N of the present distribution. Between 3.5 and 2.6 Ma, forests occurred at this latitude during irregular intervals and nearly disappeared afterwards. Likewise, a Saharan paleoriver flowed continuously until isotope Stage 134 (3.35 Ma). When river discharge ceased, wind transport of pollen grains prevailed over fluvial transport. Pollen indicators of trade winds gradually increased between 3.3 and 2.5 Ma. A strong aridification of the climate of northwestern Africa occurred during isotope Stage 130 (3.26 Ma). Afterwards, humid conditions reestablised followed by another aridification around 2.7 Ma. Repetitive latitudinal shifts of vegetation zones ranging from wooded savanna to desert flora dominated for the first time between between 2.6 and 2.4 Ma as a response to the glacial stages 104, 100 and 98. Although climatic conditions, recorded in the Pliocene, were not as dry as those of the middle and Late Pleistocene, latitudinal vegetation shifts near the end of the Pliocene resembled those of the interglacial-glacial cycles of the Brunhes chron.

Benthic foraminifera of late Quaternary sediments in the northern North Atlantic

Four long sediment cores from locations in the Framstrait, the Norwegian-Greenland Seas and the northern North Atlantic were analysed in a high resolution sampling mode (1 - 2 cm density) for their benthic foraminiferal content. In particular the impact of the intense climatic changes at glacial/interglacial transitions (terminations I and II) on the benthic community have been of special interest. The faunal data were investigated by means of multivariate analysis and represented in their chronological occurence. The most prominent species of benthic foraminifera in the Norwegian-Greenland Seas are Oridorsalis umbonatus, Cibicidoides wuellerstorfi, the group of Cassidulina, Pyrgo rotalaria, Globocassidulina subglobosa and fragmented tubes of arenaceous species. The climatic signal of termination I as well as termination II is recorded in the fossil foraminiferal tests as divided transition from glacial to interglacial. The elder INDAR maximum (individuals accumulation rate = individuals/sq cm * 1.000 y; Norwegian-Greenland Seas: average 3.000 - 6.000 individuals/sq cm * 1.000 y; northern North Atlantic: average 150 individuals/sq cm * 1.000 y) is followed by a period of decreased values. The second, younger maximum reaches comparable values as the elder maximum. The interglacial INDAR are in average 700 individuals/sq cm * 1.000 y in the Norwegian-Greenland Seas and 200 individuals/sq cm * 1.000 y in average in the northern North Atlantic. The occurence of the elder INDAR maximum shows a distinct chronological transgressivity between the northern North Atlantic (12.400 ybp.) and the Framstrait (8.900 ybp.). The time shift from south to north amounts 3.500 yrs., the average expanding velocity 0,78 km per year. Within the Norwegian-Greenland Seas the average expanding velocity amounts 0,48 km per year. This chronological transgressivity is interpreted as impact of the progressive expanding of the North Atlantic and the Norwegian Current during the deglaciation. The dynamic of the faunal development is defined as increasing INDAR per time. The elder INDAR maximum shows in both glacial/interglacial transitions an exponential increase from south to north. Termination II is characterized by a general higher dynamic as termination I. By means of the high resolution sampling density the impact of regional isotopic recognized melt-water events is recognized by an increase of endobenthic and t-ubiquitous species in the Norwegian-Greenland Seas sediments. During termination I the relative minimum between both INDAR maxima occur chronological with an decrease of calculated sea surface temperatures. This is interpreted as indication of the close pelagic - benthic coupling. The climatic signal in the northern North Atlantic recorded in the fossil benthic foraminiferal community shows a lower amplitude as in the Norwegian-Greenland Seas. The occurence of the epibenthic Cibicidoides wuellersforfi allows to evaluate the variability of the bottom water mass. In general at all core locations increasing lateral bottom currents are recognized with the occurence of the second younger INDAR maximum. In comparison with various paleo-climatological data sets fossil benthic foraminifers show a distinct koherence with changes of the atmospheric temperatures, the SSTs and the postglacial sea level increase. The benthic foraminiferal fauna is bound indirectly on and indicative for regional climatic changes, but principal dependent upon global climatic changes.

Total organic carbon content and redox-sensitiv trace metal concentrations of selected late Cenoman claystones from DSDP Hole 93-603B

The Cenomanian/Turonian (C/T) intervals at DSDP Sites 105 and 603B from the northern part of the proto-North Atlantic show high amplitude, short-term cyclic variations in total organic carbon (TOC) content. The more pronounced changes in TOC are also reflected by changes in lithology from green claystones (TOC<1%) to black claystones (TOC>1%). Although their depositional history was different, the individual TOC cycles at Sites 105 and 603B can be correlated using stable carbon isotope stratigraphy. Sedimentation rates obtained from the isotope stratigraphy and spectral analyses indicate that these cycles were predominately precession controlled. The coinciding variations in HI, OI, delta13Corg and the abundance of marine relative to terrestrial biomarkers, as well as the low abundance of lignin pyrolysis products generated from the kerogen of the black claystones, indicate that these cyclic variations reflect changes in the contribution of marine organic matter (OM). The cooccurrence of lamination, enrichment of redox-sensitive trace metals and presence of molecular fossils of pigments from green sulfur bacteria indicate that the northern proto-North Atlantic Ocean water column was periodically euxinic from the bottom to at least the base of the photic zone (<150 m) during the deposition of the black claystones. In contrast, the green claystones are bioturbated, are enriched in Mn, do not show enrichments in redox-sensitive trace metals and show biomarker distributions indicative of long oxygen exposure times, indicating more oxic water conditions. At the same time, there is evidence (e.g., abundance of biogenic silica and significant 13C-enrichment for OC of phytoplanktic origin) for enhanced primary productivity during the deposition of the black claystones. We propose that increased primary productivity periodically overwhelmed the oxic OM remineralisation potential of the bottom waters resulting in the deposition of OM-rich black claystones. Because the amount of oxygen used for OM remineralisation exceeded the amount supplied by diffusion and deep-water circulation, the northern proto-North Atlantic became euxinic during these periods. Both Sites 105 and 603B show trends of continually increasing TOC contents and HI values of the black claystones up section, which most likely resulted from both enhanced preservation due to increased anoxia and increased production of marine OM during oceanic anoxic event 2 (OAE2).

Accumulation of particulate organic carbon at the Eurasian continental margin during late Quaternary times

Data on the amount and composition of organic carbon were determined in sediment cores from the Kara and Laptev Sea continental margin, representing oxygen isotope stages 1-6. The characterization of organic matter is based on hydrogen index (HI) values, n-alkanes and maceral composition, indicating the predominance of terrigenous organic matter through space and time. The variations in the amount and composition of organic carbon are mainly influenced by changes in fluvial sediment supply, Atlantic water inflow, and continental ice sheets. During oxygen isotope stage (OIS) 6, high organic carbon contents in sediments from the Laptev Sea and western East Siberian Sea continental margin were probably caused by the increased glacial erosion and further transport in the eastward-flowing boundary current along the continental margin. During OIS 5 and early OIS 3, some increased amounts of marine organic matter were preserved in sediments east of the Lomonosov Ridge, suggesting an influence of nutrient-rich Pacific waters. During OIS 2, terrigenous organic carbon supply was increased along the Barents and western Kara Sea continental margin caused by extended continental ice sheets in the Barents Sea (Svalbard to Franz Josef Land) area and increased glacial erosion. Along the Laptev Sea continental margin, on the other hand, the supply of terrigenous (organic) matter was significantly reduced due to the lack of major ice sheets and reduced river discharge. Towards the Holocene, the amount of total organic carbon (TOC) increased along the Kara and Laptev Sea continental margin, reaching average values of up to 0.5 g C/cm**2/ky. Between about 8 and 10 ka (9 and 11 Cal ka), i.e., during times when the inner shallow Kara and Laptev seas became largely flooded for the first time after the Last Glacial Maximum, maximum supply of terrigenous organic carbon occurred, which is related to an increase in coastal erosion and Siberian river discharge. During the last 8000 years, the increased amount of marine organic carbon preserved in the sediments from the Kara and Laptev Sea continental margin is interpreted as a result of the intensification of Atlantic water inflow along the Eurasian continental margin.

Late pleistocene and holocene sedimentation in the central and eastern Persian Gulf

The sandfraction of the sediment was analysed in five cores, taken from 65 m water depth in the central and eastern part of the Persian Gulf. The holocene marls are underlayn by aragonite muds, which are probably 10-11,000 years old. 1. The cores could be subdivided into coarse grained and fine grained layers. Sorting is demonstrated by the following criteria: With increasing median values of the sandfraction - the fine grained fraction decreases within each core; - the median of each biogenic component, benthonic as well as planktonic, increases; - the median of the relict sediment, which in core 1179 was carried upward into the marl by bioturbation, increases; - the percentages of pelecypods, gastropods, decapods and serpulid worms in the sandfraction increase, the percentages of foraminifera and ostracods decrease; - the ratios of pelecypods to foraminifera and of decapods to ostracods increase; - the ratios of benthonic molluscs to planktonic molluscs (pteropods) and of benthonic foraminifera to planktonic foraminifera increase (except in core 1056 and 1179); - the ratio of planktonic molluscs (pteropods) to planktonic foraminifera increases; - the globigerinas without orbulinas increase, the orbulinas decrease in core 1056. Different settling velocities of these biogenic particles help in better understanding the results : the settling velocities, hence the equivalent hydrodynamic diameters, of orbulinas are smaller than those of other globigerinas, those of planktonic foraminifera are smaller than those of planktonic molluscs, those of planktonic molluscs are smaller than those of benthonic molluscs, those of pelecypods are smaller than those of gastropods. Bioturbation could not entirely distroy this "grain-size-stratification". Sorting has been stronger in the coarse layers than in the finer ones. As a cause variations in the supply of terrigenous material at constant strength of tidal currents is suggested. When much terrigenous material is supplied (large contents of fine grained fraction) the sedimentation rates are high: the respective sediment surface is soon covered and removed from the influence of tidal currents. When, however, the supply of terrigenous material is small, more sandy material is taken away in all locations within the influence of terrigenous supply. Thus the biogenic particles in the sediment do not only reflect the organic production, but also the influence of currents. 2. There is no parameter present in all cores that is independently variable from grain size and can be used for stratigraphic correlation. The two cores from the Strait of Hormus were correlated by their sequences of coarse and fine grained layers. 3. The sedimentation rates of terrigenous material, of total planktonic and benthonic organisms and of molluscs, foraminifera, echinoids and ophiuroids are shown in table 1 (total sediment 6.3-75.5 cm/1000 yr, biogenic carbonate 1.9-3.6 cm/1000 yr). The sedimentation rates of benthonic organisms are nearly the same in the cores of the Strait of Hormus, whereas near the Central Swell they are smaller. In the upper parts of the two cores of the Strait of Hormus sedimentation rates are higher than in the deeper parts, where higher median values point to stronger reworking. 4. The sequence of coarse and fine grained intervals in the two cores of the Hormus Strait, attributed to variations in climate, as well as the increase of terrigenous supply from the deeper to the upper parts of the cores, agrees with the descriptions in the literature of the post Pleistocene climate as becoming more humid. The rise of sea level is sedimentologically not measurable in the marly sediments - except perhaps for the higher content of echinoids in the lower part of core 1056. These may be attributed to the influence of a migrating wave-base. 5. The late Pleistocene aragonite mud is very fine grained (> 50%< 2 p) and poor in fossils (0.5-1.8%) biogenic particles of total sediment. The sand fraction consists almost entirely of white clumps, c. 0.1 mm in diameter (1177), composed of aragonite needles and of detrital minerals with the same size (1201). The argonite mud was probably not formed in situ, because the water depth at time of formation was at most 35 m at least 12 m. The sorting of the sediment (predominance of the fine grained sand), the absence of larger biogenic components and of pellets, c. 0.2-0.5 mm in diameter, which are typical for Recent and Pleistocene locations of aragonite formation, as well as the sedimentological conditions near the sampling points, indicate rather a transport of aragonite mud from an area of formation in very shallow waters. Sorting as well as lenticular fabric in core 1201 point to sedimentation within the influence of currents. During alternating sedimentation - and reworking processes the aragonitic matrix was separated from the silt - and sand-sized minerals. The lenses grade into touches because of bioturbation. 6. In core 1056 D2 from Hormus Bay the percentages of organic carbon, total nitrogen and total carbonate were determined. With increasing amounts of smaller grain sizes the content of organic matter increases, whereas the amount of carbonate decreases. The amounts of organic carbon and of nitrogen decrease with increasing depth, probably due to early-diagenetic decomposition processes. Most of the total nitrogen is of organic origin, only about 10% may well be inorganically fixed as ammonium-nitrogen. In the upper part of the core the C/N-ratio increases with increasing depth. This may be connected with a stronger decomposition of nitrogen-containing organic compounds. The general decrease of the C/N-ratios in the lower part of the core may be explained by the relative increase of inorganically fixed ammonium-nitrogen with decreasing content of organic matter.

Pollen profiles from a Late Palaeolithic site in the community of Bad Buchau-Kappel, Baden-Wuerttemberg, Germany

Excavations were carried out in a Late Palaeolithic site in the community of Bad Buchau-Kappel between 2003 and 2007. Archaeological investigations covered a total of more than 200 m**2. This site is the product of what likely were multiple occupations that occurred during the Late Glacial on the Federsee shore in this location. The site is situated on a mineral ridge that projected into the former Late Glacial lake Federsee. This beach ridge consists of deposits of fine to coarse gravel and sand and was surrounded by open water, except for a connection to the solid shore on the south. A lagoon lay between the hook-shaped ridge and the shore of the Federsee. This exposed location provided optimal access to the water of the lake. In addition, the small lagoon may have served as a natural harbor for landing boats or canoes. Sedimentological and palynological investigations document the dynamic history of the location between 14,500 and 11,600 years before present (cal BP). Evidence of the deposition of sands, gravels and muds since the Bølling Interstadial is provided by stratigraphic and palynological analyses. The major occupation occurred in the second half of the Younger Dryas period. Most of the finds were located on or in the sediments of the ridge; fewer finds occurred in the surrounding mud, which was also deposited during the Younger Dryas. Direct dates on some bone fragments, however, demonstrate that intermittent sporadic occupations also took place during the two millennia of the Meiendorf, Bølling, and Allerød Interstadials. These bones were reworked during the Younger Dryas and redeposited in the mud. A 14C date from one bone of 11,600 years ago (cal BP) places the Late Palaeolithic occupation of the ridge at the very end of the Younger Dryas, which is in agreement with stratigraphic observations. Stone artifacts, numbering 3,281, comprise the majority of finds from the site. These include typical artifacts of the Late Palaeolithic, such as backed points, short scrapers, and small burins. There are no bipointes or Malaurie-Points, which is in accord with the absolute date of the occupation. A majority of the artifacts are made from a brown chert that is obtainable a few kilometers north of the site in sediments of the Graupensandrinne. Other raw materials include red and green radiolarite that occur in the fluvioglacial gravels of Oberschwaben, as well as quartzite and lydite. The only non-local material present is a few artifacts of tabular chert from the region near Kelheim in Bavaria. A unique find consists of two fragments of a double-barbed harpoon made of red deer antler, which was found in the Younger Dryas mud. It is likely, but not certain, that this find belongs to the same assemblage as the numerous stone artifacts. Although not numerous, animal bones were also found in the excavations. Most of them lay in sediments of the Younger Dryas, but several 14C dates place some of these bones in earlier periods, including the Meiendorf, Bølling, and Allerød Interstadials. These bones were reworked by water and redeposited in mud sediments during the Younger Dryas. As a result, it is difficult to attribute individual bones to particular chronological positions without exact dates. Species that could be identified include wild horse (Equus spec.), moose or elk (Alces alces), red deer (Cervus elaphus), roe deer (Capreolus capreolus), aurochs or bison (Bos spec.), wild boar (Sus scrofa), as well as birds and fish, including pike (Esox Lucius).

Orbits of the double stars, A B of [Epsilon] Hydrae and ? 883, by the graphical method.

Type-written ms.

Naẓm al-Jamīʻ al-ṣaghīr, [late 15th century?].

Fine copy of Abū Naṣr al-Farāḥī's (d.1242) versification of al-Jamīʻ al-ṣaghīr fī al-furūʻ, the well-known legal treatise by Muḥammad ibn al-Ḥasan al-Shaybānī (d.804). Excerpts from Kashf al-ẓunūn addressing these two works appear on leaf affixed to 'title page' (p.5).

Results of observations of the fixed stars made with the Madras meridian circle at the Government Observatory, Madras.

"Published by order of the government of Madras."

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