Climate and vegetation history from a 14,000-year peatland record, Kenai Peninsula, Alaska

Analysis of pollen, spores, macrofossils, and lithology of an AMS ¹⁴C-dated core from a subarctic fen on the Kenai Peninsula, Alaska reveals changes in vegetation and climate beginning 14,200 cal yr BP. Betula expansion and contraction of herb tundra vegetation characterize the Younger Dryas on the Kenai, suggesting increased winter snowfall concurrent with cool, sunny summers. Remarkable Polypodiaceae (fern) abundance between 11,500 and 8500 cal yr BP implies a significant change in climate. Enhanced peat preservation and the occurrence of wet meadow species suggest high moisture from 11,500 to 10,700 cal yr BP, in contrast to drier conditions in southeastern Alaska; this pattern may indicate an intensification and repositioning of the Aleutian Low (AL). Drier conditions on the Kenai Peninsula from 10,700 to 8500 cal yr BP may signify a weaker AL, but elevated fern abundance may have been sustained by high seasonality with substantial snowfall and enhanced glacial melt. Decreased insolation-induced seasonality resulted in climatic cooling after 8500 cal yr BP, with increased humidity from 8000 to 5000 cal yr BP. A dry interval punctuated by volcanic activity occurred between 5000 and 3500 cal yr BP, followed by cool, moist climate, coincident with Neoglaciation. Tsuga mertensiana expanded after ~ 1500 cal yr BP in response to the shift to cooler conditions.     

Measurement of the lunar neutron density profile

Anin situ measurement of the lunar neutron density from 20 to 400 g cm^?2 depth below the lunar surface was made by the Apollo 17 Lunar Neutron Probe Experiment (LNPE) using particle tracks produced by the¹⁰B (n,α)⁷Li reaction. Both the absolute magnitude and the depth profile of the neutron density are in good agreement with theoretical calculations by Lingenfelter, Canfield, and Hampel. However, relatively small deviations between experiment and theory in the effect of Cd absorption on the neutron density and in the relative¹⁴⁹Sm to¹⁵⁷Gd capture rates reported previously (Russet al., 1972) imply that the true lunar¹⁵⁷Gd capture rate is about one half of that calculated theoretically.     

Strontium, Neodymium and Lead Isotope Analyses of NIST Glass Certified Reference Materials: SRM 610, 612, 614

The NIST glass certified reference materials, SRM 610-617, have been widely adopted by the geological community as calibration samples for a variety of in situ trace element analytical techniques. There is now an urgent requirement for similar reference materials for in situ isotopic analytical techniques. We have analysed SRM 610, 612 and 614 for their Pb, Sr and Nd isotopic compositions using thermal ionisation mass spectrometry. Large differences in isotopic composition were observed between each CRM, suggesting a significant trace element content in the initial starting material (base glass). As a result, isotopic compositions for one CRM cannot be extrapolated to another, and each must be calibrated for use independently. We present the first compilation of working values for these glasses.     

Manganese(III) binding to a pyoverdine siderophore produced by a manganese(II)-oxidizing bacterium

The possible roles of siderophores (high affinity chelators of iron(III)) in the biogeochemistry of manganese remain unknown. Here we investigate the interaction of Mn(III) with a pyoverdine-type siderophore (PVD_MnB1) produced by the model Mn(II)-oxidizing bacterium Pseudomonas putida strain MnB1. PVD_MnB1 confirmed typical pyoverdine behavior with respect to: (a) its absorption spectrum at 350-600 nm, both in the absence and presence of Fe(III), (b) the quenching of its fluorescence by Fe(III), (c) the formation of a 1:1 complex with Fe(III), and (d) the thermodynamic stability constant of its Fe(III) complex. The Mn(III) complex of PVD_MnB1 had a 1:1 Mn:pvd molar ratio, showed fluorescence quenching, and exhibited a light absorption spectrum (A_max = 408-410 nm) different from that of either PVD_MnB1-Fe(III) or uncomplexed PVD_MnB1. Mn(III) competed strongly with Fe(III) for binding by PVD_MnB1 in culture filtrates (pH 8, 4°C). Equilibration with citrate, a metal-binding ligand, did not detectably release Mn from its PVD_MnB1 complex at a citrate/PVD_MnB1 molar ratio of 830 (pH 8, 4°C), whereas pyrophosphate under the same conditions removed 55% of the Mn from its PVD_MnB1 complex. Most of the PVD_MnB1-complexed Mn was released by reaction with ascorbate, a reducing agent, or with EDTA, a ligand that is also oxidized by Mn(III). Data on the competition for binding to PVD_MnB1 by Fe(III) vs. Mn(III) were used to determine a thermodynamic stability constant (nominally at 4°C) for the neutral species MnHPVD_MnB1 (log K = 47.5 ± 0.5, infinite dilution reference state). This value was larger than that determined for FeHPVD_MnB1 (log K = 44.6 ± 0.5). This result has important implications for the metabolism, solubility, speciation, and redox cycling of manganese, as well as for the biologic uptake of iron.     

A Preliminary Appraisal of Seven Natural Zircon Reference Materials for In Situ Hf Isotope Determination

There is a growing need for new zircon reference materials for in situ Hf-isotope analysis by laser ablation-multicollector inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS). In this contribution we document the results of a preliminary investigation of seven natural zircons, conducted in order to test their suitability in this regard. Solution MC-ICP-MS data on separated Lu and Hf fractions provided reference compositional data while the results of ca. 750 in situ LA-MC-ICP-MS analyses allowed assessment of potential micrometre-scale heterogeneity. On the basis of these analyses and additional relevant considerations such as availability, size and (Lu)Yb/Hf ratio, we suggest that, of the currently available zircons, Temora-2 and Mud Tank are most likely to provide robust reference materials for Hf isotope determinations both at the present time and into the future. The former has the advantage of also being well-characterised for U-Th-Pb systematics and suitable for in situ age determination, while the latter is the most readily available and is of very large grain size. Additional materials such as BR266, and 91500, although limited in supply, show more consistent Lu/Hf ratios and are thus of use in monitoring elemental fractionation during ICP-MS analysis.     

Economic restructuring, housing policy and Maori housing in Northland, New Zealand

Since 1984 the New Zealand economy has experienced a significant phase of economic restructuring which has had a differential impact on various sectors, regions and social groups within the economy. This paper examines the extent to which economic change has affected the marginalized status of Maori households in the predominantly rural region of Northland. The social implications of economic restructuring are assessed by focusing on the housing circumstances of this indigenous people. Using a newly developed Maori housing database, we argue that relatively progressive housing policies, developed in the 1980s, have failed to address the housing problems of Maori and that the recent reliance on ‘market’ mechanisms to meet housing needs is likely to exacerbate problems of housing access and cost.     

The shoreline preservation index as a relative-age dating tool for late pleistocene shorelines: An example from the bonneville basin,U.S.A.

This paper evaluates the utility of the shoreline preservation index (s.p.i.) for estimating the age of late Pleistocene palaeolake shorelines, the relative influence of various factors on shoreline preservation, and whether shoreline preservation varies significantly with shoreline aspect. Sampled shorelines from the 3300 km² study area, which includes the Skull, Tule and Puddle Valley portions of the Lake Bonneville basin, range in age from approximately 26 to 12 ka. Their total s.p.i. values range from 23 to 69 per cent, average 46 per cent, and do not vary significantly with shoreline aspect. The data from Skull and Tule Valleys, where studied shorelines are of known age, are analysed first in order to determine if there are statistically significant associations between variables representing shoreline preservation, age, degree of geomorphic development and duration of subaerial exposure. Pairwise correlation is then repeated using observations from all three valleys in order to determine how data from the Puddle Valley shorelines, whose hypothesized ages are not supported by radiocarbon analyses, affect the results. Results show that s.p.i. is useful as a relative-age dating tool, that the postulated ages of the Puddle Valley shorelines are ordinally correct, and that geomorphic development is not an important influence on the preservation of these late Pleistocene shorelines. The relative importance of shoreline age and the relative unimportance of duration of subaerial exposure with respect to shoreline preservation suggest that subaqueous processes play a more substantial role in shoreline obliteration than is generally suggested.     

Distinctive microbial structures and the pre-phanerozoic fossil record

The live and sedimentary components of the flat laminated microbial mat at Laguna Figueroa have been studied since the late sixties. This paper reports the observation and isolation of a variety of micro-organisms, both prokaryotes and eukaryotes. The microbes were taken from the flat laminated mats submerged under at least one meter of water due to the spring rains of 1979 and 1980. Both in situ and enrichment culture observations were made using light and electron microscopic techniques. New strains of the following microbes are reported here: Bacillus megaterium, Bacillus licheniformis, Arthrobacter simplex and Paratetramitus jugosus. Several pseudomonads were isolated, some of which form distinctive subsurface colonial structures. Regular distinctive colony morphologies and desiccation resistant cysts were often observed, several types of which grow to characteristically large sizes and resemble objects found in the pre-Phanerozoic fossil record.Some colonies of manganese oxidizing bacilli and other bacteria are reminiscent of microfossils of the 2 Ga-old Gunflint Iron formation such as Metallogenium, Eosphaera tyleri, Eoastrion and Huronispora. Some manganese oxidizing bacteria form colonial structures that might be mistaken for individual organisms in the tens to hundreds of microns size range. The diversity of microbial structures, including those with preservation potential, must be kept in mind when interpreting the microfossil record.     

Isotope Ratio Determination in the Earth and Environmental Sciences: Developments and Applications in 2004/2005

This review documents developments and applications in the field of isotope ratio determination, as reflected in the literature for the Earth and environmental sciences for the years 2004 and 2005. The emphasis is largely one on applications, reflecting the enormous diversity of problems to which isotopic analysis is now applied, but seen against a background of rapid change in the uptake of new analytical technologies.