Uppermost Samples Research Articles

The Frasnian Upper Kellwasser event and a lower Famennian stratigraphic gap in Calabria (southern Italy)

The identification of three late Frasnian conodont biozones (MN 11–12 and 13, as defined in the Montagne Noire, France) and of several Famennian conodont biozones (Early, Late, and Latest marginifera, and Late postera zones of the standard zonation) in the Palaeozoic record of the Stilo Unit (southern Calabria, southern Italy) indicates the existence of a stratigraphic gap during the early Famennian (triangularis, crepida and rhomboidea zones). In the studied section, this gap occurs above a thin, black, pelitic horizon that appears just on top of the uppermost sample dated as late Frasnian. The conodonts obtained from the beds underlying this black horizon are all highly pyritized, unlike the few Famennian conodonts found in the limestone bed immediately overlying this horizon, which is richer in organic matter. Both stratigraphic features (the black pelitic horizon and the gap in the conodont record) are interpreted as being related to the Upper Kellwasser Anoxic Event. These new data indicate that this important biotic crisis was also evident in the pelagic environments of the Palaeozoic succession of the Stilo Unit at the very end of the Frasnian.

Sources and timing of trace metal contamination to sediments in remote sealochs, N.W. Scotland

Sediment cores from a transect of sealochs, Etive, Sunart, Nevis, Duich, Broom and Torridon in N.W. Scotland were analysed for the trace metals lead, copper, and zinc. In addition, sediment cores from the Clyde Sea Basin (Loch Fyne, the Gareloch, Clyde dumpsite) and from the Irish and Celtic Seas were analysed as possible source areas for contaminated particles. The sediment cores were dated using excess 210Pb and 137Cs, and Al normalisation was used to correct for sediment compositional effects. All cores showed increased concentrations of all trace metals (and M/Al) towards the surface, with a maximum of 280–500% above background being observed in Loch Etive. Only cores from Duich and Torridon (Zn/Al and Pb/Al) and Etive (Zn/Al) did not continue to show an increase in trace metals to the uppermost samples. The burden of atmospherically derived trace metals accumulated over the past 100 years was compared with similar published burdens from a series of freshwater lochs adjacent to the sealochs. Plots of excess 210Pb (used to correct for sediment focusing) against atmospherically derived Pb showed a series of linear relationships of systematically decreasing gradient towards the north-west, away from potential urban sources of lead. It was calculated that 49% (15–77%) of the Pb but only 3% (1–4%) of the Zn and 2% (0–3%) of the Cu reached the sealochs from atmospheric sources. The remaining trace metals deposited in the sealochs came from marine particles. Using trace metal ratios as an indicator of pollutant provenance, it was shown that the trace metals came predominantly from the Irish Sea. There was no evidence of trace metals derived from the Firth of Clyde basin. It was concluded that trace metal contamination from the Clyde and the surrounding industrialised urban area was mainly deposited in the estuary and the Clyde Sea basin with its adjoining sealochs, such as the Gareloch and Loch Fyne.

Re-evaluation of the chronology of the palaeolithic site at Jeongokri, Korea, using OSL and TT-OSL signals from quartz

Seven samples were collected from sediments at the Palaeolithic site of Jeongokri, Korea, known for the first discovery of Acheulian-like handaxes in East Asia. Optically stimulated luminescence (OSL) ages obtained from chemically purified quartz from the upper five samples are in stratigraphic order, but the ages of the lower samples are not. The OSL signal of the oldest samples occurs well above the saturation level of the exponential part of the dose response curve; however, the OSL signal has an additional component that grows linearly at high doses, making it possible to calculate a D e value and thus an age. However the reliability of calculating D e using this linear component is not clear. In contrast, the thermally transferred OSL (TT-OSL) signal grows linearly with dose up to at least 1600 Gy, thus permitting its use for dating. The TT-OSL ages are in agreement with those from the OSL for the four uppermost samples, but give older ages for the lower three samples. Ages obtained using TT-OSL are in stratigraphic order and indicate that the oldest artefacts have an age of ∼195 ka.

Rhenium Contents in Japanese River Waters Measured by Isotope Dilution ICP-MS and the Relationship of Re with Some Chemical Components

Rhenium (Re) concentrations in 450 samples collected from 45 Japanese rivers were determined using inductively coupled plasma mass spectrometry (ICP-MS) to understand Re behavior in the geological environments. The isotope dilution method (ID), which included chemical separation and concentration steps, was applied to obtain Re recovery. Using the ID method we concentrated Re in the water 20 times. Direct sample injection was also carried out to compare the results with ID; agreement was good, but ID had lower relative standard deviations with almost 100% Re recovery from the water. The geometric mean was 0.81 ng/L. When the Re concentrations in the uppermost sampling point of each river and 60 other chemical properties in the waters were compared, good correlations were observed with 12 elements and ions; the highest correlation was observed with . The results implied that the possible chemical form for Re in parent rocks was sulfides.

Boreal forest dynamics in north-eastern Sweden during the last 10,000 years based on pollen analysis

A pollen record obtained from a 2.2-m sediment succession deposited in a small lake in the province of Vasterbotten, north-eastern Sweden, reveals the presence of continuous forest cover since 8,500 calendar years before present (cal B.P.). Forest with abundant Pinus (pine) and Betula (birch) initially colonized the area, followed by a dominance of deciduous trees, primarily Betula, from ca. 8,000 to ca. 3,200 cal B.P. Pollen accumulation rates of Quercus (oak), Ulmus (elm) and Tilia (linden) suggest the possible local presence of these thermophilous tree species during this period. The climate gradually became colder and moister around 3,500 cal B.P. and an increased abundance of Sphagnum spores indicates paludification. Picea (spruce) became established around 3,200 cal B.P. and less than 500 years later this was the dominant tree species around the lake. The fire frequency as inferred from charcoal particles exhibits a general increase from ca. 3,000 cal B.P. with subsequent charcoal accumulation maxima at around 2,800 cal B.P., 1,700 cal B.P. and in recent time. The human influence on vegetation was significant during the last 200-300 years. Soil erosion increased substantially and fern spores amount to ca. 55% of the total pollen assemblage in the uppermost samples. These results suggest an extensive anthropogenic impact on the local forest ecosystem, with abundant logging, burning and ditching in the vicinity of the lake. Independent evidence of sub-recent human-induced environmental change is provided by historical accounts. Complementary information on catchment soil development and aquatic nutrient status was provided by records of magnetic susceptibility and elemental carbon, and nitrogen contents obtained from the same sediment core.

Fluvial transport as a natural luminescence sensitiser of quartz

The optically stimulated luminescence (OSL) sensitivity of quartz sampled from the bed of the Castlereagh River in inland New South Wales increases linearly with distance downstream, through both a proportional increase in the number of luminescent grains and increases in the sensitivity of individual grains. It is argued that downstream transport provides numerous opportunities for repeated irradiation and bleaching which combine to increase sensitivity of the quartz grains. Individual quartz grains collected from the uppermost sampling site on the Castlereagh River increase in sensitivity in response to repeated cycles of laboratory irradiation, heating and illumination, providing an explanatory analogue. Furthermore, initially non-luminescent grains are shown to be ‘switched on’ by this same laboratory treatment. We conclude that downstream increases in the luminescence sensitivity of quartz observed in the Castlereagh River are due to intrinsic changes within the quartz and not due to any macro changes in the grains, for example polishing, or abrasion and loss of non-luminescent grains. We also infer that the high OSL sensitivity of sedimentary quartz from Australia is due to the predominance of environments which provide numerous opportunities for repeated irradiation, illumination and heating. Observation of the change in luminescence sensitivity of quartz bedload has the potential to provide additional information on the nature of bedload transport processes. Data from the Castlereagh River indicate that the rate of bedload transport is approximately constant along the ∼325 km sampled reach.

Age Controls on the Tanqua and Laingsburg Deep-Water Systems: New Insights on the Evolution and Sedimentary Fill of the Karoo Basin, South Africa

Abstract Improved constraints on the timing of Permian clastic sedimentation in the Karoo basin of South Africa have been revealed by new U-Pb single-grain zircon ages determined using the Sensitive High Resolution Ion Microprobe Reverse Geometry (SHRIMP-RG). Analyses were performed on 180 zircon grains recovered from six ash beds exposed in the southwestern part of the Karoo basin. Samples were collected from two distinct loci of deep-water basin-floor and submarine-slope deposition within the Permian Ecca Group: the Tanqua and Laingsburg depocenters. Previous work constrained depositional ages of the 1800-m-thick deep-water to fluvial succession to 270–255 Ma. This poor chronostratigraphic resolution precluded robust stratigraphic correlation between the depocenters and impeded interpretation of basin evolution. The new data suggest that deep-water siliciclastic deposition began ~ 275 Ma (the lower Permian Collingham Formation), while the youngest ages are latest Permian. The Tanqua and Laingsburg depocenters began sand deposition at different times. Sandstone deposition in the Laingsburg depocenter started sometime after 275 Ma, and deposition of the first thick turbidite-dominated succession (Fan A) is bracketed into a period of less than 20 My. The Tanqua depocenter was sand starved during this interval. Both the uppermost sample from the Laingsburg depocenter and the lowermost from the Tanqua depocenter yield similar maximum depositional ages. This indicates, within the resolution of the age data, synchronous submarine sandstone deposition in the two loci at this time (~ 255 Ma). These data indicate that submarine deposition was still ongoing at a time when fluvial floodplain conditions are interpreted elsewhere in the Karoo basin. All the ash samples contain late Paleozoic zircon-grain age populations, while three samples contain small numbers of early Paleozoic, Proterozoic, and Archean zircon grains. Paleozoic zircon-grain age populations are interpreted as a record of arc activity linked to subduction. Increasing numbers of Precambrian zircons stratigraphically upward provide insight into changing source terranes during deposition into the Karoo basin.

Longitudinal changes and indicator species of the fish fauna in the subtropical Sinos River, Brazil

This study investigated the fish fauna in the subtropical Sinos River, considering species addition and replacement and the occurrence of indicator species along a longitudinal gradient. Patterns in fish assemblage ordination evaluated by correspondence analysis reflected the headwater and lowland river reaches. Uppermost sampling stations were characterized by species with restricted occurrence and medium abundance, whereas in the lowland most species were captured only once during the surveyed period and in low abundance. Species addition prevailed between the headwater sampling stations and both addition and replacement occurred between the lowland sampling stations. Nine species were characteristic for the headwater reach and 14 species for the lowland reach.

Astoria Fan sediments, DSDP site 174, Cascadia Basin: Hf–Nd–Pb constraints on provenance and outburst flooding

The Astoria submarine fan, located off the coast of Washington and Oregon, has grown throughout the Pleistocene from continental input delivered by the Columbia River drainage system. Enormous floods from the sudden release of glacial lake water occurred periodically during the Pleistocene, carrying vast amounts of sediment to the Pacific Ocean. Deep Sea Drilling Project (DSDP) site 174, located on the southern distal edge of the Astoria Fan, is composed of 879 m of terrigenous sediment. The section is divided into two major units separated by a distinct seismic discontinuity: an upper, turbidite fan unit (Unit I), and an underlying finer-grained unit (Unit II). Both units have overlapping ranges of Nd and Hf isotope compositions, with the majority of samples having ε Nd values of − 7.1 to − 15.2 and ε Hf values − 6.2 to − 20.0; the most notable exception is the uppermost sample in the section, which is identical to modern Columbia River sediment. Nd depleted mantle model ages for the site range from 2.0 to 1.2 Ga and are consistent with derivation from cratonic Proterozoic source regions, rather than Cenozoic and Mesozoic terranes proximal to the Washington–Oregon coast. The Astoria Fan sediments have significantly less radiogenic Nd (and Hf) isotopic compositions than present day Columbia River sediment ( ε Nd = − 3 to − 4; [Goldstein, S.J., Jacobsen, S.B., 1987. Nd and Sr isotopic systematics of river water suspended material: implications for crustal evolution. Earth. Planet. Sci. Lett. 87, 249–265.]), and suggest that outburst flooding, tapping Proterozoic source regions, was the dominant sediment transport mechanism in the genesis and construction of the Astoria Fan. Pb isotopes form a highly linear 207Pb/ 204Pb– 206Pb/ 204Pb array, and indicate the sediments are a binary mixture of two disparate sources with isotopic compositions similar to Proterozoic Belt Supergroup metasediments and Columbia River Basalts. The combined major, trace and isotopic data argue that outburst flooding was responsible for depositing the majority (top 630 m) of the sediment in the Astoria Fan.

Wenlock and uppermost Llandovery bentonites as stratigraphic markers in Estonia, Latvia and Sweden

Fifty-nine Wenlock and uppermost Llandovery bentonite samples from the Estonian and Latvian Aizpute drill-core sections were studied by analysing magmatic sanidine composition by XRD. On the basis of sanidine composition and geochemical data the Estonian bentonites can be grouped into six types, which probably reflect different volcanic sources. These bentonites originate from 33 different eruptions, 16 of which can be recognised on the basis of their sanidine composition. Four bentonites from the Llandovery/Wenlock boundary interval in Estonia are correlated with the Aizpute core in Latvia and with outcrops on Gotland in Sweden.

Response of the fish community to human‐induced changes in the Biobío River in Chile

Summary1. The Biobío River basin of south‐central Chile exhibits the greatest species richness of all rivers in Chile, where it is one of the most important rivers for human use. Use for provision of drinking water, irrigation, sewage effluents, hydropower generation and industry has increased dramatically during the last decade. To help understand the effects of human activities on the Biobío River, we document recent changes in the fish community.2. In this study, current patterns of distribution and abundance of fishes were compared with the expected longitudinal pattern, and to historical data from studies conducted before the rapid development of the last decade. Fish distribution, biomass, abundance and diversity were studied at eight sampling stations in the middle and lower zones of the river in both high and low flow seasons.3. Contrary to the pattern observed in less impacted river systems, species richness (S), diversity (H′) and abundance [calculated catch per unit effort (CPUE)] all tended to decrease downstream from the uppermost sampling locations. Mean S decreased from 7.9 to 5.4, mean H′ decreased from 0.7 to 0.4, and mean CPUE decreased from 111 to 43 from hyporithral to potamal locations.4. Comparison with previous records indicates loss or reduction in distribution of native species, and a concurrent expansion in distribution and abundance of tolerant introduced species (e.g. Gambusia holbrooki, and Cyprinus carpio) over the last 10–15 years. These comparisons suggest a large‐scale and long‐term effect of recent human impacts on the river.

A 17 000‐year history of Andean climate and vegetation change from Laguna de Chochos, Peru

AbstractThe manifestation of major climatic events such as the timing of deglaciation and whether, or not, the Younger Dryas affected Andean systems has garnered considerable recent attention. Even the Holocene is rapidly emerging as a time of considerable interest in Neotropical palaeoclimatology and palaeoecology. The Holocene of the Neotropics is now revealed as a time of some temperature change with precipitation:evaporation ratios fluctuating markedly. Major changes in lake level, ice‐accumulation, and vegetation are indicative of changes both in precipitation and temperature regimes. Although global‐scale forcing mechanisms may underlie some of these changes, e.g. the precessional rhythm, other variability appears to be localised. In a record from near the upper forest limit of the eastern Peruvian Andes, pollen, charcoal, and sedimentary data suggest that the deglaciational period from ca. 17 000 to ca. 11 500 cal. yr BP was a period of rapid climatic oscillations, set against an overall trend of warming. A warm‐dry event is evident between ca. 9500 and ca. 7300 cal. yr BP, and comparisons with other regional archives suggest that it was regional in scale. A ca. 1500‐yr periodicity in the magnetic susceptibility data is evident between 12 000 and 6000 cal. yr BP, reaching a peak intensity during the dry event. A weaker oscillation with a 500–600‐yr periodicity is present throughout much of the Holocene. The uppermost sample of the pollen analysis reveals deforestation as modern human land use simplified the landscape. Copyright © 2005 John Wiley & Sons, Ltd.

Longitudinal patterns in benthic communities in an urban stream under restoration

Okeover Stream, on the University of Canterbury campus in Christchurch, New Zealand, has been the subject of restoration efforts since 1998. Our study focused on quantifying the response of this urban stream to current restoration efforts. Initially, physico‐chemical conditions and biological communities at three sites along the Okeover Stream were compared with three physically similar sites on each of nearby Waimairi Stream and Avon River. General physical and chemical parameters were similar in all streams with circum‐neutral pH, specific conductivity ranging from 167 to 173 μS/cm, dissolved oxygen ranging from 9.0 to 9.2 mg/litre, low turbidity, and similar hydrological conditions. However, analysis of heavy metals in the sediment showed mean lead (Pb) concentrations in Okeover and Waimairi Streams exceeded ANZECC ISQG‐low trigger values (86.9 and 83.7 mg/kg, respectively), whereas Avon River sediment Pb levels (27.3 mg/ kg) were below trigger values. Benthic taxonomic richness did not differ significantly among the three streams. However, Okeover Stream community was dominated by the amphipod Paracalliopefluviatilis, whereas in Waimairi Stream and Avon River the gastropod snails Potamopyrgus antipodarum and Physella acuta were the dominant benthic fauna. A further assessment made at six sites along 1200 m of Okeover Stream showed no distinct longitudinal patterns in physical or chemical conditions, but there was a strong pattern in benthic macroinvertebrate communities. Taxonomic richness and caddisfly diversity increased downstream, with twice as many taxa at the most downstream site than the uppermost sampling site. In upper reaches, copper (Cu), Pb, and zinc (Zn) concentrations in sediments all exceeded ANZECC ISQG‐low trigger values. Despite ongoing restoration efforts in Okeover Stream, sedimentation, the presence of high heavy metal concentrations, intermittent flows in headwaters, and possible barriers to adult recolonisation seem to be having a continuing negative impact on benthic communities, especially in the headwaters.

Geochemistry and mineralogy of the 2.45 Ga Pronto paleosols, Ontario, Canada

The Ontario, Canada Pronto paleosols, which formed around 2.45 Ga on Archean granite, were studied through field observation, mineralogical study by microscope and microprobe, and chemical analyses of major and 45 trace elements, including rare earth elements (REEs). Since the first full description of its mineralogy and chemistry of major elements by Gay and Grandstaff [Gay, A.L., Grandstaff, D.E., 1980. Chemistry and mineralogy of Precambrian paleosols at Elliot Lake, Ontario, Canada. Precambrian Res. 12, 349–373], the Pronto paleosols are among the most cited paleosols of the Archean–early Proterozoic era, though several questions have been raised as to whether they are true in-place ancient soils. Results of this study show that the studied section meets the criteria for being in-place paleosols. Furthermore, the profile has no explicit traces of being strongly affected by hydrothermal alteration. The REE-containing accessory minerals were destroyed through weathering, and secondary phosphate minerals with REEs formed. All of these observations support the weathering origin of the Pronto paleosols. However, the profile should be identified as a saprolith, rather than paleosol, as even the uppermost samples exhibit the granitic texture of the parent rock. The samples in this study were collected mainly from two sites (Site I and Site II). Saprolith samples from Site I show the retention of ΣFe and increases of the Fe(III)/Fe(II) ratios and the chemical index of alteration (CIA) values toward the unconformity. As for the Site II samples, the ΣFe/Ti ratios show slight decreases with increasing CIA values in the upper part of section, whereas these samples also show the same trend of increasing Fe(III)/Fe(II) ratios as the samples from Site I. Microprobe analyses show that Fe from the parent rock distributes mainly in mafic minerals as hornblende, biotite, or chlorite, which were completely destroyed during the early stages of weathering. In the saprolith section, Fe is present in sericite aggregates in the form of obscure patches of iron oxide tens of micrometers in size. All these characteristics indicate that: (i) the Fe was not lost during soil formation at Site I and slight amount of Fe was lost at Site II; and (ii) ferrous Fe was quantitatively transformed to ferric Fe (i.e., oxidation) during soil formation. In the samples from both sites, the ratios of Al/Ti and Si/Ti decrease toward the top of the profile. Together with the destruction of minerals toward the unconformity, such as apatite, biotite and chlorite, the depletion of Al and Si suggests that the parental granite was weathered by an acidic weathering solution. During the Archean–early Proterozoic era, the high atmospheric partial pressure of CO 2 ( pCO 2) is the most probable candidate for producing the acidic weathering solution.

Holocene Vegetation History and Palaeoenvironmental Conditions on the Temperate Atlantic Coast of Argentina, as Inferred from Multi-Proxy Lacustrine Records

Holocene vegetation history and palaeoenvironmental conditions are investigated at the south coast of Buenos Aires Province, Argentina. La Olla 1 and Laguna del Sauce Grande sediment sequences are analysed for pollen, calcareous microfossil (ostracods and foraminifers) and plant macrofossil remains (mainly seeds and charophyte oospores). Supplementary information is provided by sedimentological analysis. Modern surface sample data are used to assist in the interpretation of the fossil records. La Olla 1 sequence covers the period 7890 to 7630 cal. BP. The microfauna recovered is characteristic of a shallow marginal-marine environment such as a coastal lagoon. The microfossils indicate a marine connection between 7850 and 7800 cal. BP. Plant macrofossil remains and pollen analyses indicate an extension of the water body after 7780 cal. BP. The pollen record reveals the development of a halophytic plant community in a coastal environment. The sediment record from Laguna del Sauce Grande comprises the last 3000 years. Microfossils and macrofossil remains indicate that the lake history begins with a temporary brackish-water phase. More stable conditions and higher salinity values occur between 1940 and 900 cal. BP. Periods of water level fluctuations occur after 900 cal. BP, with high water levels between 660 and 270 cal. BP. The uppermost samples of the sequence show similar conditions to present day. Pollen spectra indicate a relatively stable vegetation composition throughout the last 3000 years. Pollen assemblages reflect the present regional grassland vegetation with taxa characteristic of the surrounding dune communities.

The Application of Steroidal Biomarkers to Track the Abandonment of a Roman Wastewater Course at the Agora (Athens, Greece)*

A subterranean, stone‐built, sediment‐filled culvert discovered during excavations at the Agora (Athens, Greece) was dated to the Roman period on the basis of its characteristic construction and associated finds, including coins. The location of the culvert relative to other adjacent watercourses and an ancient river bed suggested that the structure was a sewer. This was confirmed through a multi‐molecular biomarker approach based on analysis of the bile acids associated with sediment filling the sewer, using gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). The acid fraction contained predominantly deoxycholic and lithocholic acids, while the neutral steroid fraction comprised a complex mixture of Δ5 sterol and 5β‐ and 5α‐stanols, dominated by coprostanol, suggesting the presence of faecal matter of predominantly human origin. The concentrations of neutral and acidic faecal biomarkers were observed to vary in tandem, with the highest concentrations being found in the sediment at the base of the fill in the culvert. A reduction in concentration occurred with decreasing depth of the fill, with concentrations in the uppermost samples being little different from control samples of sediment taken beyond the confines of the culvert. The enhanced concentration of bile acids relative to 5β‐stanols compared with fresh human faeces must reflect the enhanced diagenetic stability of the former, thereby making bile acids the possibly preferred biomarker for this type of study. The quantitative data obtained suggest that the culvert fell rapidly out of use, possibly coinciding with the Slavic incursion in AD 582–3.

Terrestrial—oceanic environmental change in the southern Okhotsk sea during the Holocene

The Okhotsk Sea plays a significant role in climatic and oceanic environmental change on regional and global scales. The fluctuation in pollen and spores abundances was investigated in order to reconstruct terrestrial and ocean environmental change during the Holocene. Fluctuation of the total abundance and assemblage of most of pollen and spores reflects terrestrial environmental change along the coastal area of the southern Okhotsk Sea. On the other hand, the abundance of Cryptomeria, Cyclobalanopsis and Castanopsis pollen from plants which are not currently growing in Hokkaido, is suggested to be a good proxy for the intensity of the Tsushima Current. Relatively warm pollen assemblages characterize Periods 1 (calendar age 7240–3050 yr BP) and 3 (150–0 yr BP) while a relatively cold pollen assemblage characterizes Period 2 (3050–150 yr BP). Three warm sub-periods 1a (7240–6500 yr BP), 1c (5900–4550 yr BP) and 1e (4300–3550 yr BP) are associated with relatively strong intensity of the Tsushima Current, transgression, and the occurrence of bivalves living in warm conditions. Continuous cooling started 3000 yr BP. The area remained so cold that the intensified Tsushima Current (2800–2400 and 1700–1400 yr BP) would have made little difference to terrestrial warming in the southern Okhotsk Sea. In the uppermost samples, a large increase in total abundance of pollen and spores may be partly attributed to the modern global warming effect.

Atmospheric Pb deposition in Spain during the last 4600 years recorded by two ombrotrophic peat bogs and implications for the use of peat as archive

Two ombrotrophic peat bogs in Northwestern Spain provided a history of 4600 years of Pb accumulation. Highest Pb concentrations (84–87 μg g −1) were found near the bogs’ surface, but there were also other significant peaks (6–14 μg g −1), indicating pre-industrial atmospheric pollution. The enrichment factors (EFs) in both cores show a remarkably similar record. Atmospheric Pb pollution dates back to at least approximately 2500 years ago, reaching a first maximum during the Roman period. For the last 300 years, Pb EFs significantly increased due to industrial development, but the uppermost samples of the bogs show decreasing Pb EFs, probably due to the phasing out of leaded gasoline. These results are also supported by 206Pb/ 207Pb isotope ratios, as they continuously decrease from ca. 3000 BP until 2000 BP (from 1.275 at 4070 14C years BP to 1.182), indicating the growing importance of non-radiogenic Pb released from Iberian ores by ancient mining. Peat samples at a 3–5-cm depth are even less radiogenic ( 206Pb/ 107Pb=1.157), indicating the strong influence of leaded gasoline. Despite the common history shared by the two bogs, striking differences were found for Pb enrichment, whether this was calculated by normalising to the Pb/Ti ratio of the upper continental crust or to the Pb/Ti ratios of peats from pre-anthropogenic times. This effect seems to be related to differences in Ti accumulation in both bogs, possibly due to physical fractionation of the airborne dust during wind transport. Enrichment has to be carefully considered when comparing the results obtained for different bogs, since our results suggest that normalising to crustal proportions is meaningless when the bulk of the deposition in an area is strongly influenced by short- and medium-range dust transport.

Holocene palaeoenvironments of salt lakes in the Darling Anabranch region, south-western New South Wales, Australia

Abstract Aim Fossil pollen preserved within small salt lake basins in the Australian interior is used to reconstruct mid- to late Holocene vegetation. The study aims to identify the origin of problems such as woodland decline and salinization within present ecosystems. Location Warrananga and Tooperoopna salt lakes, south-western New South Wales, Australia. Methods Pollen, carbonized particle and sedimentological analyses of cores taken from salt lakes. Results Prior to c. 4500 years ago, the region supported a dense cover of Casuarinaceae woodlands. It is possible that the subhumid zone species Allocasuarina luehmannii comprised some of the Casuarinaceae element. In the late Holocene, A. luehmannii disappeared from the record and chenopodiaceous low shrublands expanded. About 2000 years ago, Callitris representation decreased. Woodland contraction also occurred after European settlement. Main conclusions Increasing aridity or greater seasonal variation in the climate during the late Holocene caused a contraction of woodland vegetation. Increased proportions of Chenopodiaceae may indicate soil salinization around the basins. A decrease in Callitris was possibly due to heightened severity or frequency of drought events after 2000 years ago. Decline in woodland pollen in the uppermost samples is explained by the preferential clearing of Callitris glaucophylla, Callitris gracilis and Casuarina pauper for timber and their limited regeneration because of browsing by stock and rabbits.

Sorption of heterocyclic compounds on natural clayey till

The sorption of benzofuran, dibenzofuran, benzothiophene, and dibenzothiophene from water on natural clayey till from two locations in Denmark was investigated in single solute systems for a large range of solute concentrations. The variation in sorption of a basic (quinoline) and a neutral (dibenzofuran) heterocyclic compound in samples from different depths in the natural clayey till was also investigated. The sorption isotherms for all four compounds and both clayey tills were highly non-linear, and the overall best fits were obtained with Freundlich isotherms. These observations indicate that sorption is not strictly hydrophobic or that the affinity for organic material is influenced by the sorbed solute, and that multiple components contribute to the sorption. The f oc normalized linear K d-value and Freundlich K f-coefficient were compared with estimated K oc values. Hydrophobic sorption appears to dominate for dibenzofuran, benzothiophene and dibenzothiophene, whereas benzofuran and in particular quinoline sorption is influenced by inorganic sorption sites. This corresponds reasonably well with expectations based on estimates of critical organic carbon content. The sorption of quinoline at the uppermost sample was slightly higher (10%–20%) than for the deeper locations. This is possibly related to a slightly higher clay content at this depth. The sorption of dibenzofuran was higher at the deepest location (approximately 65%) than for the above locations. The only measured geological parameter which was significantly different in the sample from the deep location was the content of fine silt.