Mineral Magnetic Properties Research Articles

Mineral magnetic properties of artificial samples systematically mixed from haematite and magnetite

SUMMARY Detailed rock magnetic investigations were carried out on a set of samples with defined ratios of haematite and magnetite. The measured parameters provide a reference for interpreting common rock magnetic parameters in investigations of sediments. The contribution of haematite to the magnetic fraction must exceed 95 wt-% of the magnetic fraction when mixed with magnetite in order to visibly influence grain size and coercitivity indicative magnetic parameters. Coercivity of remanence (BCR) and coercive force (BC) do not change in the same way with increasing haematite content, which results in a peak BCR/BC value at around 99.5 wt-% haematite. Variations in haematite content can be ignored when interpreting most rock magnetic parameters, especially grain size indicative parameters for samples where haematite contents range from 0 to 98 wt-%. The S-ratio is still the most sensitive parameter for estimating the relative amount of haematite in magnetite/haematite mixtures. A combination of S-ratio, the saturation isothermal remanent magnetization divided by the low field magnetic susceptibility (SIRM/κLF) and BCR is the most effective way to identify haematite in natural samples. Our results agree with literature data and fill the gap between results obtained either from pure magnetite or haematite with comparable grain sizes.

Mineral magnetic properties of surface sediments at Bei’anhe, Beijing, and its environmental significance

A multiparameter investigation of surface sediments from the Bei’anhe section (Beijing) has been conducted using environmental magnetic approaches. The studied sedimentary sequence consists of pluvial and lacustrine silts and clay of the Holocene age. Magnetite, hematite and pyrrhotite were identified as the dominant magnetic minerals. The mineral magnetic characteristics are considered to reflect the Holocene paleoenvironmental processes of the studied area, which are different from the mineral magnetic properties of typical polluted sections reported in the Beijing area. The low-field magnetic susceptibility and saturated isothermal remanence magnetization of the section decrease gradually with increasing depth. This indicates that the concentration of magnetic minerals in the strata decreases down the section. Values of interparametric ratios, such as ARM/SIRM, χ ARM/χ and SIRM/χ, gradually increase with increasing depth, which indicates a down-section decreasing trend in the magnetic grain size of the sediments. Pyrrhotite occurs below the depth of 22 cm, suggesting the existence of redox interface. The magnetic variations of the Bei’anhe surface sediments might be controlled by two geological processes: reductive diagenesis and pedogenesis. Our findings may have provided a reference point for magnetic investigation of polluted surface sediments in the Beijing area.

Constraints on the Pleistocene chronology of sediments from the Lomonosov Ridge

Despite its importance in the global climate system, age‐calibrated marine geologic records reflecting the evolution of glacial cycles through the Pleistocene are largely absent from the central Arctic Ocean. This is especially true for sediments older than 200 ka. Three sites cored during the Integrated Ocean Drilling Program's Expedition 302, the Arctic Coring Expedition (ACEX), provide a 27 m continuous sedimentary section from the Lomonosov Ridge in the central Arctic Ocean. Two key biostratigraphic datums and constraints from the magnetic inclination data are used to anchor the chronology of these sediments back to the base of the Cobb Mountain subchron (1215 ka). Beyond 1215 ka, two best fitting geomagnetic models are used to investigate the nature of cyclostratigraphic change. Within this chronology we show that bulk and mineral magnetic properties of the sediments vary on predicted Milankovitch frequencies. These cyclic variations record “glacial” and “interglacial” modes of sediment deposition on the Lomonosov Ridge as evident in studies of ice‐rafted debris and stable isotopic and faunal assemblages for the last two glacial cycles and were used to tune the age model. Potential errors, which largely arise from uncertainties in the nature of downhole paleomagnetic variability, and the choice of a tuning target are handled by defining an error envelope that is based on the best fitting cyclostratigraphic and geomagnetic solutions.

Sediment transport on the Freiston Shore managed realignment site: An investigation using environmental magnetism

This paper presents the first attempt to use environmental magnetism to quantify sediment provenance on a managed realignment (MR) site. MR is one technique for creating/restoring intertidal habitats and improving the standard of coastal flood protection. Monitoring of MR sites is essential for determining how successful they are at achieving these aims, and normally includes measurement of sedimentation rates through the use of accretion plates and sediment erosion tables (SETs). One limitation of this technique is that the provenance of sediment accreting on realigned surfaces cannot readily be quantified. Our results demonstrate that magnetics-based fingerprinting can successfully apportion sediment source contributions to created/restored coastal saltmarshes with an efficiency similar to that of existing un-mixing models applied to other habitats (82.87%). Analysis of mineral magnetic properties (χFD, IRMsoft and SIRM) demonstrated that the majority of sediment accreting on the Freiston Shore MR Site (Lincolnshire, UK) is derived from established saltmarshes seaward of the breached embankment. This indicates that the MR site may be growing at the expense of neighbouring saltmarshes—thereby undermining the habitat-creation objectives used to justify MR. It is recommended that future MR monitoring programmes consider the provenance of post-breach deposits to help identify any adverse impacts that wetland creation/restoration may have on existing habitats. Further testing of environmental magnetism in coastal saltmarshes and MR sites is necessary to validate wider use of the technique.

Mineral magnetic properties of a weathering sequence of soils derived from basalt in Eastern China

Abstract The magnetic properties and magnetic mineralogy of a weathering sequence of soils developed on basalt parent material from eastern China, were studied by rock magnetism, X-ray diffraction and soil chemical analyses to establish the connection between mineral magnetic properties and pedogenic development in a subtropical region. The magnetic susceptibility of soils formed on basalt varied greatly and did not increase with the degree of pedogenic development. The frequency-dependent susceptibility (χfd) values of soils ranged from 1.0 to 11.1% and increased with the pedogenic development. Highly significant linear relationship was found between the frequency-dependent susceptibility and the Fed content (R2 = 0.683) and Fed/Fet ratio (R2 = 0.780) in soils, indicating that pedogenic SP ferrimagnetic grains were associated with enrichment of the secondary iron oxide minerals in the weathering process of soil. Rock magnetism analysis showed that the major magnetic carriers in the weakly weathered soil profiles are magnetite and/or maghemite, and the highly developed soil profiles are generally enriched in magnetite/maghemite grains of pedogenic origin and the magnetically hard haematite, indicating that the magnetic component was transformed from a ferrimagnetic phase (magnetite) to antiferromagnetic phase (hematite) during pedogenic development. Results indicated that some of the magnetic parameters of soils, in this case χfd, can be useful for pedogenic comparisons and age correlations in the weathering sequence of soil. It is thus suggested that multiparameter rock magnetic investigations represent a more powerful approach for pedogenesis.

Two-year magnetic monitoring in conjunction with geochemical and electron microscopic data of roadside dust in Seoul, Korea

Mineral magnetic properties of roadside dusts in Seoul, Korea, were measured and compared with the results of geochemical analyses in order to investigate the spatio-temporal patterns of urban pollution. Scanning electron microscope (SEM) observations and energy dispersive X-ray spectroscopy (EDS) analyses were carried out to verify the magnetic materials and their potential sources. A total of 1956 dust samples were collected monthly at eight sites, from June 1998 to June 2000. Thermomagnetic data and SEM observations for magnetic extracts indicated that the major magnetic phase was magnetite-like material. In particular, the highest and the lowest magnetic concentrations were observed in industrial areas and a park area, respectively, whereas, heavy traffic areas showed low to intermediate concentration. A linear correlation between enrichment indexes of magnetic susceptibility and heavy metals suggests that magnetic susceptibility can be used as a proxy for heavy metal pollution. The magnetic concentrations and magnetic particle sizes showed systematic seasonal fluctuations (high and large in winter versus low and small in summer) due to the seasonal influx variations of anthropogenic magnetic materials. On the basis of the morphology and elemental composition, the magnetic materials were grouped into three types: magnetic spherules possibly emitted from factories and domestic heating systems, aggregates derived from vehicle emission or motor vehicle brake system, and angular magnetic particles of natural origin.

Long and short-term change in the Pátzcuaro Basin, central Mexico

Data are presented from four new cores from the Pátzcuaro basin in the volcanic highlands of central Mexico, which provide new insights into climate change and human impact over the last 23,000 cal. yr (19,000 14C yr) BP. The cores have been analysed for a range of proxies including mineral magnetic properties, loss-on-ignition, diatoms and stable isotope composition ( δ 18O and δ 13C). High lake levels are recorded in the late Pleistocene and early Holocene, with a probable shift from winter precipitation from the Pacific in the late Pleistocene, to the modern summer regime in the early Holocene. Gradual drying and increased climatic variability are indicated from the early Holocene, but particularly since 4000 cal. BP, consistent with southward displacement of the ITCZ. The changing chemical composition and depth of the lake led to the accumulation of ostracod layers. The timing of the late Holocene dry intervals corresponds to global periods of rapid change driven by Bond and/or solar cycles. By combining a range of proxies we have been able to identify climatic change, even within a period of significant human disturbance. The use of multiple cores indicates that a coherent climatic signal is recorded even in a basin subject to tectonic disturbance. This study also provides new data to support the interpretation of major human impact on the basin in both the pre- and post-Hispanic periods, refuting continued suggestions that basin-wide erosion occurred only after the Spanish conquest. A new model of sediment un-mixing has been applied to identify different source materials contributing to deposition.

Factor Analysis of Particle Size Specific Mineral Magnetic Measurements on Agricultural Topsoils from the Isle of Man

Agricultural topsoils from the five soil categories of the Isle of Man (British Isles) have been fractionated at discrete particle size intervals and their mineral magnetic properties have been analyzed. The aim was to characterize Manx soils and, with the aid of simultaneous R‐ and Q‐mode factor analysis, evaluate the use of mineral magnetic measurements as an appropriate means of discriminating soil categories. Results show Manx agricultural topsoils contain a range of magnetic concentrations (similar to sedimentary and acid igneous rocks), magnetic mineralogy (greater influence of magnetically soft than magnetically hard minerals) and magnetic domain size (mainly stable single domain and superparamagnetic grains) characteristics, with significant differences between the five identified soil categories for each of the fractionated size class intervals used. Despite the mineral magnetic approach showing considerable potential for classifying Manx soils on the basis of their magnetic properties, large variations exist within individual soil categories. However, compared with previous studies, particle size specific measurements provide a more appropriate means of discrimination than bulk magnetic measurements. Each specific fractionated particle size range accommodates similar abilities of discrimination, yet no single class size is better than any other. Nevertheless, the ability of factor analysis to detect multivariate patterns in mineral magnetic data shows it is a useful data analysis tool for interrogating soil data sets.

Magnetic properties of urban street dust and their relationship with organic matter content in the West Midlands, UK

This study demonstrates significant correlations between the organic matter content of urban street dust and certain mineral magnetic properties, which accords with previous work that indicates magnetic parameters offer potential as a proxy for organic content. However, site-specific data demonstrate the relationship can be different for particular roads, even within the same area. This indicates the association may be more complex than previous work proposes and a cautionary note is required. It is recommended that the nature of the relationship between magnetic and organic properties should be fully explored for particular urban environments and individual field settings, before using magnetic measurements as a proxy for organic matter content. Furthermore, whilst soil is believed to significantly contribute to urban street dust, magnetic values in this study are much higher than those previously reported for top-soils and indicate the influence of other sources, such as anthropogenic pollutants. This suggests that using magnetic measurements to discriminate sources of urban particulates has considerable potential for development.

Palaeolimnological and sedimentary responses to Holocene forest retreat in the Scandes Mountains, west-central Sweden

A suite of analyses was performed on sediments accumulated during the last 10 700 years in Lake Spaime, a small, hydrologically open water body in the modem alpine tundra zone of the Scandes Mountains, west-central Sweden. The study aimed to evaluate (1) the nature of climate changes that forced the late-Holocene lowering of altitudinal tree limit in the region, the timing of which is known from prior studies based on radiocarbon dating of subfossil wood, and (2) the impact of these vegetational changes on an aquatic ecosystem. Arboreal pollen and plant macrofossil data confirm the persistence of trees in the lake catchment at least from c. 9700 cal. BP until c. 3700 cal. BP. Although growing-season temperature is commonly believed to be the dominant factor driving boreal forest tree-limit variations in the region, a chironomid-based reconstruction of mean July air temperature suggests that local deforestation during the late Holocene was not accompanied by a significant cooling. The tree-limit retreat was more likely caused by increasing effective moisture and declining length of the growing season. The ecohydrological response of Lake Spaime to this combination of climate and vegetational changes included a decline in primary productivity, as indicated by an abrupt decrease in sediment organic matter content, while associated increases in organic 613C, 615N and C/N point to diminished fluxes and altered balance of catchment derived nutrients following deforestation. The decline in aquatic productivity is also marked by a distinct change in the mineral magnetic properties, from a high magnetic concentration assemblage dominated by fine-grained magnetite of biogenic origin to one dominated by background levels of coarse-grained detrital magnetite.

Mineral Magnetic Properties of Polluted Topsoils: A Case Study in Fujian Province, Southeast China

AbstractWe have conducted mineral magnetic investigations of polluted topsoil samples, which were collected in the vicinity of a steel plant and a coal‐burning power plant in Sanming City, Fujian Province, southeast China. The methods used include the temperature‐dependence of magnetic susceptibility, hysteresis loops and isothermal remanent magnetization acquisition curves. High‐temperature susceptibility measurements suggest that magnetite, partially oxidized magnetite, hematite and pyrrhotite exist in the polluted topsoil samples. The studied samples show mean magnetic grain‐sizes of large pseudo‐single domain, and multidomain‐like or multidomain. For the samples with significantly high susceptibility (x) and low frequency‐dependent susceptibility (x), x and xfd measurements can be used as an effective method for detecting the polluted topsoils. For the samples with relatively low x and high xfd, the presence of ferrimagnetic iron sulphide can serve as a potential pollution indicator in the case that an origin from bedrock weathering has been excluded. We further suggest that mineral magnetic measurements can provide a better and more complete understanding of the pollution processes forindustrially‐polluted topsoils.

Mineral magnetic properties of loess/paleosol couplets of the central loess plateau of China over the last 1.2 Myr

We have conducted a multiparameter investigation of 15 loess‐paleosol couplets (S0/L1 to S14/L15) from the Jiaodao section in the central loess plateau of China using environmental magnetic approaches coupled with soil science techniques. The magnetic parameters display systematic variations that seem to be closely related to paleoclimate variations and intensity of pedogenesis. High‐temperature susceptibility curves of paleosols show a generally decreasing trend in reversibility from the base of the Lishi Formation to the Holocene black loam, possibly indicating a decrease in weathering intensity. This may reflect a long‐term increase in aridity and/or a general long‐term cooling trend of the interior of the Asian continent from 1.2 Ma to the present. Several samples display wasp‐waisted hysteresis loops. These are most pronounced in moderately enhanced paleosols, less pronounced in the practically unaltered loess, and subdued in the well‐developed paleosols, but wasp waistedness reappears in the most developed paleosols. This wasp‐waistedness sequence suggests that the composition, concentration, and grain size of magnetic minerals all contribute to the hysteresis behavior of samples from the studied loess‐paleosol sequence, but each factor has a different effect at different stages of pedogenesis.

Magnetic remanence in the Murchison meteorite

Abstract— The Murchison meteorite is a carbonaceous chondrite containing a small amount of chondrules, various inclusions, and matrix with occasional porphyroblasts of olivine and/or pyroxene. It also contains amino acids that may have served as the necessary components for the origin of life. Magnetic analyses of Murchison identify an ultrasoft magnetic component due to superparamagnetism as a significant part of the magnetic remanence. The rest of the remanence may be due to electric discharge in the form of lightning bolts that may have formed the amino acids. The level of magnetic remanence does not support this possibility and points to a minimum ambient field of the remanence acquisition. We support our observation by showing that normalized mineral magnetic acquisition properties establish a calibration curve suitable for rough paleofield determination. When using this approach, 1–2% of the natural remanence left in terrestrial rocks with TRM and/or CRM determines the geomagnetic field intensity irrespective of grain size or type of magnetic mineral (with the exception of hematite). The same method is applied to the Murchison meteorite where the measured meteorite remanence determines the paleofield minimum intensity of 200–2000 nT during and/or after the formation of the parent body.

Environmental magnetic and magnetic fabric studies in LakeWaynewood, northeastern Pennsylvania, USA: Evidence for changes inwatershed dynamics

An environmental magnetic and magnetic fabric study of sedimentscollected from Lake Waynewood, a post-glacial lake in the PoconoMountains of Pennsylvania, USA, provided a history of the lake's watersheddynamics over the past 3500 years. Two 5 m long, Mackereth coresof lake sediments and three watershed soil profiles were analyzed magnetically.Paleosecular variation and 14C measurements allowed timing ofchanges in the lake's watershed which are documented by changes in ARM,SIRM,χ, S-ratio, SIRM/χ, ARM/χ and ARM/SIRMdowncore. Prior to 2900 years BP, there is little evidence for allogenicinflux. Dramatic changes in mineral magnetic properties and a strong AARmagnetic fabric appear approximately 2900 years BP, suggesting major changes inwatershed conditions, either in the hydrologic regime or in vegetative cover.Between 2900 and 1800 yrs BP, large variations in magnetic mineralogy areapparent, whereas about 1800 years BP, a single sediment source began todominate the magnetic mineralogy. About 100–200 years ago, conditionsagain changed, probably due to clearcutting and settlement of the watershed.Topsoil erosion appears to have dominated the magnetic signal. S and Mnconcentration downcore indicate that there is little evidence for reductiondiagenesis having caused the changes observed in magnetic mineral type andconcentration, except in the top 10 centimeters of the sediment column.

Paleoclimatic significance of mineral magnetic properties of loess sediments in northeastern Qinghai-Tibetan Plateau

Loess deposit in the northeastern Qinghai-Tibetan Plateau offers an excellent record of climate and environment changes in this region. We have conducted multiparameter mineral magnetic analyses of samples of loess deposits from the Dongchuan, Lalakou and Panzishan sections. The methods used include magnetic susceptibility, frequency-dependent susceptibility, temperature-dependent susceptibility, isothermal remanent magnetization acquisition, and magnetic hysteresis loops. The results reveal that magnetite is the dominant contributor to magnetic susceptibility. Maghemite and hematite is also present in the loess layers and paleosol horizons. The higher concentration of maghemite in paleosols suggests that the formation of maghemite occurred during in situ pedogenesis, which plays an important role in the enhancement of the magnetic susceptibility. Similar to that in the Chinese Loess Plateau lying to the east of the Liupan Mountains, magnetic granulometry in the studied loess and paleosols is predominantly pseudo-single-domain (PSD). However, the mean grain-size of the ferrimagnetic minerals in loess is evidently coarser (larger PSD and multidomain-like) than in paleosols (mainly PSD). The magnetic susceptibility of loess and paleosols is positively correlated with the content of ultrafine magnetite/maghemite grains, and hence with the intensity of in situ pedogenesis. Therefore, the enhanced magnetic susceptibility in the studied loess-paleosol sequences can be interpreted as being due to climatically induced in situ pedogenesis.

Tracer properties of eroded sediment and source material

AbstractThis paper examines the conservativeness of tracers through the sediment generation process. This is done by comparing a selection of tracer properties of sediment eroded from large plots by simulated rainfall, with the corresponding properties of the source materials within the plots. Sediment was generated using three simulated rainfall events for each of five selected erosion source types in the Tarago catchment, Victoria, Australia. As there were particle size and organic content differences between the source material and the generated sediment, the measured tracer properties of the source material were corrected for these differences. The possible role of analytical errors in this investigation was also addressed. The geochemical property, concentration of Fe2O3, was not conservative for any of the process sources investigated. Concentration of Al2O3 was not conservative for three of the four process sources investigated, and the sum of molecular proportions of CaO**, Na2O, K2O and Al2O3 was not conservative for two of the four process sources investigated. Mineral magnetic properties, IRM850 and χ were also found to be not conservative, although this may be the result of the complex relationship between particle size and mineral magnetic properties not being adequately accommodated in this analysis. The radionuclide tracers, 137Cs and 210Pbex, were found to be conservative through the sediment generation process. Copyright © 2002 John Wiley & Sons, Ltd.

A paleoecological reconstruction of the Late Glacial and Holocene based on multidisciplinary studies at Steregoiu site (Gutai Mts., Romania)

High resolution analyses of pollen, mineral magnetic properties, loss of ignition, lithostratigraphy and AMS 14C measurements of lake sediments and peat deposits accumulated in the former crater lake of Steregoiu (Gutâiului Mts., NW Romania), gave new and important information about vegetation and climate changes from the period GS-2 to the present. During the Lateglacial, three cold events were recorded: before 14,700 cal. years BP (GS-2), 14,050–13,800 cal. years BP (GI-1d), 12,900-11,500 cal. years BP (GS-1), and a warm climatic event between 13,800-12,950 cal. years BP (GI-1c to GL-1a). The Late Glacial/Holocene transition around 11,500 cal. years BP, was determined by an expansion of Betula, Alnus and Picea, followed by a rapid and strong expansion of Ulmus. At 10,700 cal. years BP, dense and highly diverse forests with Ulmus, Quercus, Tilia, Fraxinus and a few Acer and Corylus individuals dominated the area. Corylus and Picea were the dominant species in the forests from 10,150 to 8,500 cal. years BP. The first occurrence of single Fagus pollen grains was around 8,000 cal years BP. Only at 4,700 cal year BP Fagus and Carpinus became widespread and established trees in the local woodlands.

A Late Pleistocene palaeoclimate record based on mineral magnetic properties of the entrance facies sediments of Kulna Cave, Czech Republic

Kulna Cave is located in the Moravian Karst, a well-developed karstic region formed in Devonian limestones in the eastern part of the Czech Republic. The entrance facies sediments in the cave consist of interbedded layers of silts (loess) and clay-rich silts (loam) that were either directly blown into the cave entrance or redeposited in the cave by slope processes during the Last Glacial Stage. The layers of loess and loam overlie fluvial sands and gravels deposited during the Last Interglacial. Previous research at Kulna concentrated on the archaeology, palaeontology and dendrology of these entrance facies sediments. From these data, palaeoenvironmental conditions in the vicinity of the cave were reconstructed. Our results suggest that susceptibility variations and in particular variations in pedogenic susceptibility yield a more detailed record of the palaeoenvironmental conditions at the cave during the Last Glacial Stage. Magnetic susceptibility (χ) was measured on approximately 700 samples collected throughout three well-studied profiles in the cave entrance. The χ record is well defined and correlates from one profile to another. Mineral magnetic measurements [FD, ARM/SIRM, S-ratio, χ(T)] suggest that χ variations in the Kulna sediments from the Last Glacial Stage are controlled by the concentration of magnetite and/or maghemite formed during pedogenesis. After the removal of the effects of fine carbonate debris and detrital ferromagnetic minerals on the bulk χ record, we obtained a record of pedogenic susceptibility (χp) that serves to quantify the concentration of magnetic minerals formed during pedogenesis. Therefore, χp can be thought of as a proxy reflecting the intensity of pedogenesis, which in turn is controlled by climate. Our χp record is also in good agreement with the median grain size record of the Kulna sediments (another proxy for climatic change). We suggest that in the case of Kulna, χp is more sensitive to climate change than bulk χ. The Kulna pedogenic susceptibility record shows variations on both long and short timescales. The long-term trends are in good agreement with the deep-sea SPECMAP record, while the short-term oscillations correlate well with rapid changes in the North Atlantic sea surface temperatures. Our results suggest that Central European climate during the Last Glacial Stage was strongly controlled by the sea surface temperatures in the North Atlantic. Short-term warmer events and perhaps higher precipitation over the mid-continent increased the intensity of pedogenesis. Given the number of independent climate proxies determined from the entrance facies of the cave and their high resolution, Kulna is an extremely important site for studying Late Pleistocene climate.

Terminal Pleistocene/Holocene palaeoenvironmental changes revealed by mineral-magnetism measurements of lake sediments for Dali Nor area, southeastern Inner Mongolia Plateau, China

Mineral magnetic properties (SIRM, ARM, HIRM and S-ratios) are presented for two AMS 14C-dated pit-sequences of lake sediments recovered from Haoluku and Liuzhouwan (∼43°N, 117°E). The two sites fall in the semi-humid to semi-arid climate transition zone, Dali Nor area of the southeast Inner Mongolia Plateau, China. Complemented by data for loss-on-ignition (LOI), total organic carbon (TOC), carbon/nitrogen (C/N), grain-size, and pollen, these mineral-magnetic measurements provide additional insights into environmental changes occurring at this area over the last 13 500 years. Conditions were extremely dry and windy as shown by the low SIRM, ARM and HIRM and high S-ratios before 13 500yrbp. The environment began to ameliorate gradually since then, and a further humidification occurred at ∼10 300yrbp in Haoluku, the northern site, and at ∼9400yrbp in Liuzhouwan, the southern one, as implied by the increased but only moderately high SIRM, ARM and HIRM and decreased S-ratios. As indicated by the remarkably increased SIRM, ARM, HIRM and S-ratios, a deterioration commenced at ∼5600yrbp in Haoluku and at ∼4700yrbp in Liuzhouwan. In Haoluku, conditions have been generally dry and windy since ∼5600yrbp despite a minor amelioration at 4500–3000yrbp. A short but marked amelioration occurred at 1200–700yrbp in Liuzhouwan. S-ratios seem to be a reliable indicator of environmental aridity for this area.

The Late Weichselian sea level history of the Kullen Peninsula in northwest Skåne, southern Sweden

The Kullen Peninsula in northwest Skåne, at the time of the Weichselian deglaciation an island surrounded by the Kattegat Sea, is the earliest known deglaciated area in Sweden. Sediment stratigraphic and mineral magnetic properties, combined with radiocarbon dating, were used to determine and date the isolation of present‐day lake basins from the sea. Significant environmental changes, which reflect the isolations, are supported by previously published palaeoecological data and cannot be related to climate changes. Basins situated above the marine limit (ML) have short (in the order of centimetres) minerogenic sequences that are magnetically characterized by low concentrations of detrital magnetite. In contrast, the pre‐isolation sediments in basins below the ML, especially those deposited in sheltered positions in the landscape, have thick sequences (in the order of metres) of authigenic greigite‐bearing sediments. Age determinations of the isolation level are based on the AMS radiocarbon dating of terrestrial plant macrofossil remains and previously published pollen stratigraphical investigations. Supported by the upper level of a sandy beach deposit preserved on the generally steep till covered slopes, the marine limit can be determined to 88–89 m a.s.l., which developed at the regional deglaciation c. 17000 calendar years ago. The results indicate that the deglaciation shoreline level remained fairly constant, relative to the sea level, for c. 1000 years and was followed by a gentle regression. The presented shoreline displacement curve from the Kullen Peninsula extends c. 1000 calendar years further back in time than any previously published records from the Swedish west coast.