Relationships between magnetic parameters, chemical composition and clay minerals of topsoils near Coimbra, central Portugal

Lourenço, Anita; Rocha, Fernando; Gomes, Celeste

doi:10.5194/nhess-12-2545-2012

Cited by 13 publications

(5 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The relative proportions of Si, Al, and Fe in these samples are typical of aluminosilicate clay minerals derived from limestone weathering and/or eolian deposition in other cave settings (e.g., Kim et al, ; Arriolabengoa et al, ). The clay minerals present are almost certainly kaolinite and illite considering their dominance in nearby soils and in similar karst settings in Portugal (Fonseca, Barriga, & Conceição, ; Lourenço, Rocha, & Gomes, ; Rocha & Gomes, ). Field observations with a hand lens show that the sand and coarse silt fractions are composed of mostly quartz and limestone fragments, with trace amounts of heavy minerals.…”

Section: Resultsmentioning

confidence: 94%

Late Pleistocene site formation and paleoclimate at Lapa do Picareiro, Portugal

et al. 2019

View full text Add to dashboard Cite

The cave site of Lapa do Picareiro, Portugal contains a deep (~10 m) sedimentary sequence representing much of the Middle and Upper Paleolithic, with abundant animal bones, lithic/bone/shell artifacts, and charcoal/ash in hearths. A deposition model based on 49 radiocarbon ages demonstrates average sedimentation rates of 0.1-0.3 mm a −1 between 9 and 45 ka. Extrapolation suggests an age at the base of the excavation of 65-78 ka. The cave sediments are primarily limestone éboulis derived from roof spalling, and muddy fine sediment derived from weathered soil infiltrating through bedrock joints and crevices. Bone preservation in the cave is good and disturbance by bioturbation, dissolution, or erosional processes appears to be limited. Most sedimentological parameters vary conservatively with depth, indicating stable sediment sources over time. Several parameters show good agreement with paleoclimate records over the radiocarbon-dated section. The cold-arid Heinrich stadials are represented by coarse-clast beds with little fine sediment and magnetic susceptibility minima, and mild Greenland interstadials correspond with muddy beds and sharp peaks in magnetic susceptibility. This study complements ongoing archaeological excavation at the site and confirms that the sequence has the proper age, resolution, and preservation to inform on Late Pleistocene cultural and climatic transitions. K E Y W O R D S caves, Iberia, paleoclimate, Paleolithic, site formation 1 | INTRODUCTION Sedimentary deposits in caves and rock shelters are central to our understanding of human prehistory. Although caves represent only a fraction of the landscapes occupied by prehistoric humans, under the proper conditions they offer long-term preservation of valuable paleoenvironmental information in stratified sedimentary archives.The study of karstic sediments as environmental archives has a strong tradition in geoarchaeology, beginning with seminal works of the last century and advanced by developments in both methodology and theory (e.g., Collcutt). Recent geoarchaeological research in caves employs stateof-the-art dating techniques, isotope geochemistry, micromorphology, and spectroscopy to interpret site formation processes over timescales from hundreds of years to hundreds of millennia (e.g.,

show abstract

Section: Resultsmentioning

confidence: 94%

Late Pleistocene site formation and paleoclimate at Lapa do Picareiro, Portugal

et al. 2019

View full text Add to dashboard Cite

show abstract

“…Its concentration can be easily detected by measuring the magnetic properties of the soil surface samples (e.g. Lecoanet et al, 1999;Lourenço et al, 2012). Magnetic parameters, such as magnetic susceptibility (χ), saturation isothermal remanent magnetisation (SIRM) and ratios like S-ratio, SIRM/χ and HardIRM % (HARD %), can reflect the concentration, the type and the grain size of magnetic particles in the soil.…”

Section: Introductionmentioning

confidence: 99%

Magnetic, geochemical and pedological characterisation of soil profiles from different environments and geological backgrounds near Coimbra, Portugal

et al. 2014

View full text Add to dashboard Cite

This study presents an application of environmental magnetism techniques for the characterisation of the soils near Coimbra (central Portugal). Magnetic measurements, scanning electron microscopy and geochemical studies were carried out on samples collected in 6 soil profiles in order to find possible relationships and to interpret environmental implications. Magnetic susceptibility, saturation isothermal remanent magnetisation and isothermal remanent magnetisation at the backfield of 100 mT and 300 mT were measured. HardIRM %, SIRM/χ and S-ratios were also calculated. Polluted soils showed higher values of magnetic parameters in the superficial soil horizons closer to the roads, plants and urban areas. The lowest values were observed in the deeper horizons of the soil and in the areas least disturbed by human activity. The magnetic results also suggested that the magnetic signal of these soils is mainly influenced by ferrimagnetic magnetite-like minerals and with only a minor contribution from antiferromagnetic carriers (such as hematite minerals). In unpolluted soils, lithogenic contribution is reflected by the enhancement of magnetic susceptibility near parental rock material. Scanning electron microscope images of the topsoil samples revealed the presence of magnetic spherules typical of vehicular exhaust and combustion processes. This evidence suggests that the atmospheric deposition of fly ash is the main reason for the enhancement of the magnetic signal in the topsoil. Chemical analyses showed that the concentration of various heavy metals was higher than the mean background values for Portuguese soils, and higher in superficial soils. Heavy metals showed significant positive correlation with magnetic properties. The conclusions highlight the importance of using environmental magnetism methods and techniques in the evaluation process of soil evolution and pollution history throughout time.

show abstract

“…The "hard" and "soft" IRMs (referred to as HIRM and SOFT, respectively) were calculated as (SIRM+IRM −300 )/2 and (SIRM+IRM −20 )/2, respectively. The detailed discussion of the physical significance of magnetic parameters can be found in the studies of Ďurža (1999) and Lourenço et al (2012). Soil pH was measured with Mettler G20 potentiometric titration after calcium chloride extraction, deionized water using a 1:5 (w:v) of soil:solution ratio.…”

Section: Experimental Methods and Data Analysismentioning

confidence: 99%

Identifying the influence of urbanization on soil organic matter content and pH from soil magnetic characteristics

et al. 2015

View full text Add to dashboard Cite

Soil magnetic characteristics are correlated with soil pH and organic matter content. Analyzing soil magnetic characteristics, organic matter content and pH can indirectly evaluate soil pollution caused by human activities. This study analyzed the soil magnetic characteristics, organic matter content and pH in surface soil samples from different land use types in Shihezi city, a newly and rapidly developing oasis city in Xinjiang of China. The aims of this study were to explore the possible relationships among the soil magnetic parameters and thereby improve the understanding of influence of urbanization on soil properties. Eighty surface soil samples at the depth of 0-10 cm were collected from 29 July to 4 August 2013. The results showed that the magnetic minerals in surface soil were dominated by ferromagnetic minerals. Spatially, the magnetic susceptibility (χ LF ), anhysteretic remanent magnetization susceptibility (χ ARM ), saturation isothermal remanent magnetization (SIRM) and "soft" isothermal remanent magnetization (SOFT) were found to be most dominant in the new northern urban area B (N-B), followed by built-up areas (U), suburban agricultural land (F), and then the new northern urban area A (N-A). The values of χ LF , χ ARM , SIRM and SOFT were higher in the areas with high intensities of human activities and around the main roads. Meanwhile, the property "hard" isothermal remanent magnetization (HIRM) followed the order of U>N-B>F>N-A. Built-up areas had an average pH value of 7.93, which was much higher than that in the new northern urban areas as well as in suburban agricultural land, due to the increased urban pollutant emissions. The average value of soil organic matter content in the whole study area was 34.69 g/kg, and the values in the new northern urban areas were much higher than those in the suburban agricultural land and built-up areas. For suburban agricultural land, soil organic matter content was significantly negatively correlated with χ LF , and had no correlation with other magnetic parameters, since the soil was frequently ploughed. In the new northern urban areas (N-A and N-B), there were significant positive correlations of soil organic matter contents with χ ARM , SIRM, SOFT and HIRM, because natural grasslands were not frequently turned over. For the built-up areas, soil organic matter contents were significantly positively correlated with χ LF , χ ARM , SIRM and SOFT, but not significantly correlated with frequency-dependent susceptibility (χ FD , expressed as a percentage) and HIRM, because the soil was not frequently turned over or influenced by human activities. The results showed that soil magnetic characteristics are related to the soil turnover time.Citation: YANG Han, XIONG Heigang, CHEN Xuegang, WANG Yaqi, ZHANG Fang. 2015. Identifying the influence of urbanization on soil organic matter content and pH from soil magnetic characteristics. Journal of Arid Land,

show abstract

Relationships between magnetic parameters, chemical composition and clay minerals of topsoils near Coimbra, central Portugal

Cited by 13 publications

References 57 publications

Late Pleistocene site formation and paleoclimate at Lapa do Picareiro, Portugal

Late Pleistocene site formation and paleoclimate at Lapa do Picareiro, Portugal

Magnetic, geochemical and pedological characterisation of soil profiles from different environments and geological backgrounds near Coimbra, Portugal

Identifying the influence of urbanization on soil organic matter content and pH from soil magnetic characteristics

Contact Info

Product

Resources

About