Chemical analysis with regard to global and local climatic forcing measured on sediment core GeoB3711-1, GeoB3711-3 and GeoB4917-8

Global and local climatic forcing, e.g. concentration of atmospheric CO2 or insolation, influence the distribution of C3 and C4 plants in southwest Africa. C4 plants dominate in more arid and warmer areas and are favoured by lower pCO2 levels. Several studies have assessed past and present continental vegetation by the analysis of terrestrial n-alkanes in near-coastal deep sea sediments using single samples or a small number of samples from a given climatic stage. The objectives of this study were to evaluate vegetation changes in southwest Africa with regard to climatic changes during the Late Pleistocene and the Holocene and to elucidate the potential of single sample simplifications. We analysed two sediment cores at high resolution, altogether ca. 240 samples, from the Southeast Atlantic Ocean (20°S and 12°S) covering the time spans of 18 to 1 ka and 56 to 2 ka, respectively. Our results for 20°S showed marginally decreasing C4 plant domination (of ca. 5%) during deglaciation based on average chain length (ACL27-33 values) and carbon isotopic composition of the C31 and C33 n-alkanes. Values for single samples from 18 ka and the Holocene overlap and, thus, are not significantly representative of the climatic stages they derive from. In contrast, at 12°S the n-alkane parameters show a clear difference of plant type for the Late Pleistocene (C4 plant domination, 66% C4 on average) and the Holocene (C3 plant domination, 40% C4 on average). During deglaciation vegetation change highly correlates with the increase in pCO2 (r² = 0.91). Short-term climatic events such as Heinrich Stadials or Antarctic warming periods are not reflected by vegetation changes in the catchment area. Instead, smaller vegetation fluctuations during the Late Pleistocene occur in accordance with local variations of insolation.

Investigations on sediments from Lake Nam Co (Tibetan Plateau)

This study focuses on the analysis of lake sediments retrieved from the deepest part of Lake Nam Co (Tibetan Plateau). One gravity core of 115 cm length, covering the last ~ 4000 cal BP, was analyzed for geochemical and biological parameters. High organic content at ~ 4000 cal BP and the coinciding presence of pyrite framboids until ~ 2000 cal BP point to hampered decomposition of organic material due to anoxic conditions within the lake sediments. At the same time sedimentological and biological proxies suggest a rather high lake level, but still ~ 5 m below the recent one, with less saline lake water due to enhanced monsoonal activity. During this time a change in the source of organic matter to lowered input of terrestrial components is observed. A rather quick shift to a dry environment with less monsoonal influence and a lake level ~ 15 m lower than today at ~ 2000 cal BP lead to the oxygenation of sediment, the degradation of organic matter and the absence of pyrite. Oscillations of the lake level thereafter were of minor amplitude and not able to establish anoxia at the lake bottom again. A wet spell between ~ 1500 cal BP and ~ 1150 cal BP is visible in proxies referring to catchment hydrology and the ostracod-based water depth transfer function gives only a slightly elevated lake level. The last ~ 300 years are characterized by low TOC and rising TN values reflecting enhanced nutrient supply and hence an advancing influence of human activity in the catchment. Decreasing TOC/TN values point to a complete shift to almost solely aquatic biomass production. These results show that hydrological variations in terms of lake level change based on monsoonal strength can be linked to redox conditions at the lake bottom of Nam Co. Comparison with other archives over larger parts of the Tibetan Plateau and beyond exhibits a rather homogeneous climatic pattern throughout the late Holocene.

Pollen and macrofossils profiles and age determination from three cores in Northeastern Kansas, U.S.A.

Two marshes near Muscotah and Arrington, Atchison County, northeastern Kansas, yielded a pollen sequence covering the last 25,000 yrs of vegetation development. The earliest pollen spectra are comparable with surface pollen spectra from southern Saskatchewan and southeastern Manitoba and might indicate a rather open vegetation but with some pine, spruce, and birch as the most important tree species, with local stands of alder and willow. This type of vegetation changed about 23,000 yrs ago to a spruce forest, which prevailed in the region until at least 15,000 yrs ago. Because of a hiatus, the vegetation changes resulting in the spread of a mixed deciduous forest and prairie, which was present in the region from 11,000 to 9,000 yrs ago, remain unknown. Prairie vegetation, with perhaps a few trees along the valleys, covered the region until about 5,000 yrs ago, when a re-expansion of deciduous trees began in the lowlands.

Contents of P2O5, Corg, Sr, and Ba in phosphorites and host sediments from the Atlantic and Pacific oceans

Sr contents in phosphorites on shelves of the Southwest Africa, and of Chile and Peru increase with degree of their lithification, from 0.05 to 0.28% and from 0.13 to 0.16% respectively. Phosphorites from Pacific submarine seamounts have the average Sr content 0.11%, and bone phosphate from Pacific floor 0.13%. Shelf phosphorites are characterized by high correlation coefficients between Sr and P2O5 (R = +0.82) and constant Sr/P2O5 ratio (0.0084). In phosphorites from submarine sea-mounts and in bones from the ocean floor Sr/P2O5 ratio is only a little higher than a half of that in shelf phosphorites. This indicates specific and different genesis of phosphorites from submarine mountains. Ba content in recent phosphorites from the shelf of the Southwest Africa changes with increasing degree of lithification. At first their Ba contents rise from 0.031 to 0.188%, then they diminish to 0.016%, and thereafter again increase to 0.070%. This is due to successive predominance of one of the following processes going in different directions: co-precipitation with phosphate gels or formation of true separate Ba phase, loss of phosphate in crystallization and "self-purification" of concentrations, and surface adsorption. In Peru-Chile shelf phosphorites the average Ba content is 0.017%, in phosphorites from Pacific seamounts 0.192%, and in fossilized bones 0.010%.

Benthic foraminiferal stable isotope stratigraphy of ODP Site 138-846 in the tropical Pacific Ocean

A stable-isotope stratigraphy at Site 846 (tropical Pacific, 3°06'S, 90°49'W, 3307 m water depth), based on the benthic foraminifers Cibicides wuellerstorfi and Uvigerina peregrina, yields a high-resolution record of deep-sea delta18O and delta13C over the past 1.8 Ma, with an average sampling interval of 3 k.y. Variance in the delta18O and delta13C records is concentrated in the well-known orbital periods of 100, 41, and 23 k.y. In the 100-k.y. band, both isotopic signals grow from relatively low amplitudes prior to 1.2 Ma, to high amplitudes in the late Quaternary since 0.7 Ma. The amplitude of delta18O and especially of delta13C decreases in the 41-k.y. band as it grows in the 100-k.y. band, consistent with a transfer of energy into an orbitally-paced internal oscillation. A weak 30-k.y. rhythm, present in both delta18O and delta13C, may reflect nonlinear interaction between the 41-k.y. and 100-k.y. bands in the evolving climate system. In the 23-k.y. and 19-k.y. bands associated with orbital precession, delta18O and delta13C are not coherent with each other on long time scales, and do not evolve like the 100-k.y. and 41-k.y. bands. This suggests that the source of the growing 100-k.y. oscillation is not a nonlinear response to precession, in contrast to predictions of some climate models. Sedimentation rates at this site also vary with a strong 100-k.y. cycle. Unlike the isotope records, the amplitude of 100-k.y. variations in sedimentation rate is relatively constant over the past 1.8 Ma, ranging from about 15 to 70 m/m.y. Prior to 0.9 Ma, sedimentation rates co-vary with orbital eccentricity, rather than with global climate as reflected by delta18O or delta13C. A source of this 100-k.y. cycle of sedimentation rate in the absence of similar ice volume fluctuations may be precessional heating of equatorial land masses, which in an energy balance climate model drives variations of monsoonal climates with a 100-k.y. rhythm. For the interval younger than 0.9 Ma, high sedimentation rates in the 100-k.y. band are consistently associated with glacial stages. This change of pattern suggests that when the amplitude of glacial cycles become large enough, their global effects overpower a local monsoon-driven variation in sedimentation rate at Site 846.

Seawater carbonate chemistry, pigments and proteins during experiments with phytoplankton, 2010

In the high-nutrient, low-chlorophyll waters of the Gulf of Alaska, microcosm manipulation experiments were used to assess the effect of CO2 on growth and primary production under iron-limited and iron-replete conditions. As expected, iron had a strong effect on growth and photosynthesis. A modest and variable stimulation of growth and biomass production by CO2 (high CO2: 77-122 Pa; low CO2: 11-17 Pa) was observed under both iron-replete and iron-limited conditions, though near the limit of precision of our measurements in slow-growing low-iron experiments. Physiological acclimations responsible for the changes in growth were assessed. Under iron-limited conditions, growth stimulation at high CO2 appeared to result from an increase in photosynthetic efficiency, which we attribute to energy savings from down-regulation of the carbon concentrating mechanisms. In some cases, iron-rich photosynthetic proteins (PsbA, PsaC, and cytochrome b6) were down-regulated at elevated CO2in iron-limited controls. Under iron-replete conditions, there was an increase in growth rate and biomass at high CO2 in some experiments. This increase was unexpectedly supported by reductions in cellular carbon loss, most likely decreased respiration. We speculate that this effect may be due to acclimation to decreased pH rather than high CO2. The variability in responses to CO2 among experiments did not appear to be caused by differences in phytoplankton community structure and may reflect the sensitivity of the net response of phytoplankton to antagonistic effects of the several parameters that co-vary with CO2.

Petrology of basalts from DSDP Hole 83-504B

Basalts from Hole 504B, Leg 83, exhibit remarkable uniformity in major and trace element composition throughout the 1075.5 m of basement drilled. The majority of the basalts, Group D', have unusual compositions relative to normal (Type I) mid-ocean ridge basalts (MORB). These basalts have relatively high mg values (0.60-0.70) and CaO abundances (11.7-13.7%; Ca/Al = 0.78-0.89), but exhibit a marked depletion in compatible trace elements (Cr and Ni); moderately incompatible trace elements (Zr, Y, Ti, etc.); and highly incompatible trace elements (Nb, LREE, etc.). Petrographic and compositional data indicate that most of these basalts are evolved, having fractionated significant amounts of plagioclase, olivine, and clinopyroxene. Melting experiments on similar basalt compositions from the upper portion of Hole 504B (Leg 70; Autio and Rhodes, 1983) indicate that the basalts are co-saturated with olivine and plagioclase and often clinopyroxene on the 1-atm. liquidus. Two rarely occurring groups, M' and T, are compositionally distinct from Group D' basalts. Group T is strongly depleted in all magmaphile elements except the highly incompatible ones (Nb, La, etc.), while Group M' has moderate concentrations of both moderately and highly incompatible trace elements and is similar to Type I MORB. Groups M' and T cannot be related to Group D' nor to each other by crystal fractionation, crystal accumulation, or magma mixing. The large differences in magmaphile element ratios (Zr/Nb, La/Yb) among these three chemical groups may be accounted for by complex melting models and/or local heterogeneity of the mantle beneath the Costa Rica Ridge. Xenocrysts and xenoliths of plagioclase and clinopyroxene similar in texture and mineral composition to crystals in coarse-grained basalts from the lower portion of the hole are common in Hole 504B basalts. These suggest that addition of solid components either from conduit or magma chamber walls has occurred and may be a common source of disequilibrium crystals in these basalts. However, mixing of plagioclase-laden depleted melts (similar to the Costa Rica Ridge Zone basalts) with normal MORB magmas could provide an alternate source for some refractory plagioclase crystals found out of equilibrium in many phyric MORB. The uniformity of major element compositions in Hole 504B basalts affords an ideal situation for investigating the effects of alteration on some major and trace elements in oceanic basalts. Alteration observed in whole-rock samples records primarily two events - a high-temperature and a low-temperature phase. High-temperature phases include: chlorite, talc, albite, actinolite, sphene, quartz, and pyrite. The low-temperature phases include smectite (saponite), epistilbite or laumontite, and minor calcite. Laumontite may actually straddle the gap between the low- and high-temperature mineral assemblages. Alteration is restricted primarily to partial replacement of primary phases. Metamorphic grade, in general, increases from the top to the bottom of Hole 504B (Legs 69, 70, and 83) as seen in the change from a smectiteto- chlorite-dominated secondary mineral assemblage. However, a systematic progression for the interval recovered during Leg 83 is not apparent. Rather, the extent of alteration appears to be a function of the initial texture and fracture density. Variations in whole-rock major and trace element concentrations cannot be attributed convincingly to any differences in alteration observed. Compositional characteristics of the secondary minerals indicated that extensive remobilization of elements has not occurred; local redistribution is suggested in most cases. Thus, the major and trace element signature of these basalts remains effectively the same as the original composition prior to alteration.

European mink (Mustela lutreola) and American mink (Neovison vison) detection histories in Northern Spain between 2000 and 2011

Understanding changes over time in the distribution of interacting native and invasive species that may be symptomatic of competitive exclusion is critical to identify the need for and effectiveness of management interventions. Occupancy models greatly increase the robustness of inference that can be made from presence/absence data when species are imperfectly detected, and recent novel developments allow for the quantification of the strength of interaction between pairs of species. We used a two-species multi-season occupancy model to quantify the impact of the invasive American mink on the native European mink in Spain through the analysis of their co-occurrence pattern over twelve years (2000 - 2011) in the entire Spanish range of European mink distribution, where both species were detected by live trapping but American mink were culled. We detected a negative temporal trend in the rate of occupancy of European mink and a simultaneous positive trend in the occupancy of American mink. The species co-occurred less often than expected and the native mink was more likely to become extinct from sites occupied by the invasive species. Removal of American mink resulted in a high probability of local extinction where it co-occurred with the endemic mink, but the overall increase in the probability of occupancy over the last decade indicates that the ongoing management is failing to halt its spread. More intensive culling effort where both species co-exist as well as in adjacent areas where the invasive American mink is found at high densities is required in order to stop thedecline of European mink.

(Table 1, Page 1046-1047) Chemical composition of iron-manganese concretions from the Indian Ocean recovered by the R/V Vityaz and the R/V Ob

The data given in this and previous communications is insufficient to assess the quantitative role of these supplementary sources in the Indian Ocean, but they do not rule out their local significance. Elucidation of this problem requires further data on the characteristics of the composition and structure of nodules in various different metallogenic regions of the ocean floor. A study of the distribution of ore elements in nodules both depthwise and over the area of the floor together with compilation of the first schematic maps based on the results of analyses of samples from 54 stations) enables us to give a more precise empirical relation between the Mn, Fe, Ni, Cu, and Co contents in Indian Ocean nodules, the manganese ratio and the values of the oxidation potential, which vary regularly with depth. This in turn also enables us to confirm that formation of nodules completes the prolonged process of deposition of ore components from ocean waters, and the complex physico-chemical transformations of sediments in the bottom layer. Microprobe investigation of ore rinds revealed the nonuniform distribution of a num¬ber of elements within them, owing to the capacity of particles of hydrated oxides of manganese and iron to adsorb various elements. High concentration of individual elements is correlated with local sectors of the ore rinds, in which the presence of todorokite, in particular, has been noted. The appearance of this mineral apparently requires elevated Ca, Mg, Na, and K concentrations, because the stable crystalline phase of this specific mineral form of the psilomelane group may be formed when these cations are incorporated into a lattice of the delta-MnO2 type.

Geochemistry for sediment core MD02-2496

Variations in chalcophile and redox-sensitive trace elements are examined at high-resolution intervals from a ~50 kyr long sediment core (MD02-2496) from the Vancouver Island margin. Enrichments of Ag, Cd, Re, U, and Mo above lithogenous levels, signifying sedimentary suboxia and anoxia, occurred during the early Holocene and Bølling/Allerød, and during warm interstadial events of Marine Isotope Stage (MIS) 3. Down-core trace element profiles co-vary with productivity proxy records (opal, CaCO3, and marine organic carbon), and with sedimentary nitrogen isotope ratios, which reflect variably enriched nitrate upwelled from intermediate waters that were transported northward from the Eastern Tropical North Pacific. The similarity of the MD02-2496 record with records from the southern portion of the California Current System (CCS), and to the Greenland ice core oxygen isotope record during warm climate intervals, suggests that sedimentary redox conditions along the California Current responded to local productivity, to North Atlantic climate change and to tropical Pacific surface water processes via long-distance teleconnections. Concentrations of trace elements and productivity proxies were relatively depleted during the Younger Dryas, cool stadial events of MIS 3, and in two episodes of glaciomarine sedimentation from ~14.7 to 30.5 kyr BP (last glacial maximum, LGM), and from 44 to 50.4 kyr BP. Cordilleran Ice Sheet advancement onto the Vancouver Island continental shelf during the LGM led to intervals of increased terrigenous sedimentation and greatly reduced productivity not seen in the southern portion of the CCS, and along with ventilation of North Pacific Intermediate Waters, resulted in brief sedimentary oxic conditions.