Characterization of loess in central Spain: a microstructural study

Giménez, Rosario García; Villa, Raquel Vigil de la; Martín, Juan Antonio González

doi:10.1007/s12665-011-1193-7

Cited by 39 publications

(14 citation statements)

References 48 publications

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“…Although it is considered to be a rare component in loess (Mestdagh et al, 1999) it has been found in several loess areas in the world (Garcia-Gim enez et al, 2012). In our case it is present in only a limited amount (up to 28% in some areas or absent in others) as gypsum (anhydrite is not a stable mineral under subaeral exposures, or under the present climatic conditions (Herrero and Porta, 2000)).…”

Section: Possible Source Areasmentioning

confidence: 54%

“…There are no sand deposits upwind of the loess outcrops, nor have they been mentioned in any soil or geological report, and so in this case, the source material is not sand dunes as occurs in the proximal loess deposits from Neguev desert (Yaalon and Dan, 1974;Crouvi et al, 2008), at Matmata Plateau (Coud e-Gaussen, 1990 or in other cases in North, central or South Africa, Arabia or the Middle East where they are clearly due to a process of aeolian abrasion from sand dunes or active sand seas (Crouvi et al, 2010). Loess in the Tagus valley contains more than 20% clay (finer than our study area), with the origin being the fine alluvial material accumulated in the valley (Garcia-Gim enez et al, 2012). In our case, rather than texture, the predominant indicators of source area are the prevalent wind direction, the proximity to the deposits and the presence of gypsum and magnesium.…”

Section: Possible Source Areasmentioning

confidence: 63%

“…Since then, Spanish authors have overlooked the presence of such deposits and only foreign authors have mentioned them: in Andalusia (Brunnacker and Lozek, 1969;Günster et al, 2001), and the Levant region (Dumas, 1977). However, extensive accumulations of loess in the Middle of the River Tagus Valley (García-Gim enez and Gonz alez, 2010;Garcia-Gim enez et al, 2012) and the Castilian branch of the Iberian and South Submeseta (Gonz alez et al, 2000) have recently been reported. Some small areas have been dated to the Middle Pleistocene, although the most extensive areas date from the Upper Pleistocene with an age of 42.7 ka BP, and a group of small areas date from the Pleistocene-Holocene (11.1e12.1 ka BP) (García-Gim enez and Gonz alez, 2010).…”

Section: Introduction and Objectivesmentioning

confidence: 99%

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Loess and soils in the eastern Ebro Basin

Boixadera

Poch

Lowick

et al. 2015

Quaternary International

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Section: Possible Source Areasmentioning

confidence: 54%

Section: Possible Source Areasmentioning

confidence: 63%

Section: Introduction and Objectivesmentioning

confidence: 99%

See 1 more Smart Citation

Loess and soils in the eastern Ebro Basin

Boixadera

Poch

Lowick

et al. 2015

Quaternary International

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“…Given that sedimentary archives in interior Iberia are very rare for that period, it is important to explore and understand this loess record in detail. So far, efforts have been made to reveal the late Pleistocene vegetation history (Schäfer et al ., , ) and to attain a first geochemical characterization of the Tagus loess deposits (García et al ., ; Garcia Giménez et al ., ; Calvo et al ., ). Up to now there have been no clear ideas about where the loess material originated from and how it has been generated.…”

Section: Introductionmentioning

confidence: 99%

Origins and genesis of loess deposits in central Spain, as indicated by heavy mineral compositions and grain‐size variability

et al. 2018

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The formation of loess deposits strongly depends on the availability of deflatable dust-sized material. Identification of source areas and mechanisms of dust production is essential for an appropriate characterization of related palaeoenvironmental conditions. So far, little research has been done on loess deposits in the Mediterranean region and information about mechanisms of dust production is very rare. In this context, it is not clear from where the loess deposits from the upper Tagus Basin in central Spain originated. The main objective of this study was to find out whether these loess deposits were formed primarily by mountain processes and fluvial comminution, or whether they have their origin in the weathering of Tertiary marls in the centre of the Madrid Basin. A further concern was to link the determined source areas with loess formation mechanisms and concomitant environmental contexts. Following a comprehensive approach using heavy minerals and grain-size data, together with information on stratigraphic features and geomorphic positions, different local loess sources could be identified. This study shows that during the last 35 kyr a major proportion of the Tagus loess deposits was deflated from river floodplains, while the mountain region of the Iberian Range was identified as a significant source of respective floodplain sediments. Based on heavy mineral compositions and dating results, it was found that during Heinrich Stadial 3, sediment supply from the Iberian Range strongly increased, suggesting an environmental shift from initially warmer towards colder temperatures in late Marine Isotope Stage 3. Furthermore, it was found that grain-size patterns clearly indicate maximum wind strengths during Heinrich Stadial 3, followed by Heinrich Stadial 2 and Heinrich Stadial 1. These results demonstrate that the formation of dustsized particles in this part of the Mediterranean operated similar to many other places in temperate and continental regions, and that weathering processes linked to hot and dry environments were only of minor importance.

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“…Yuan and Wang (2009) attempted to link the collapsibility with seismic settlement in a loess, and concluded that both the collapsibility and seismic settlement are correlated to its metastable microstructure, but with different triggering mechanisms. Giménez et al (2012) characterized a loess in central Spain with a special perspective in microstructure analysis. It was further noted by Rogers et al (1994) that a change in particle packing is central to loess collapse.…”

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confidence: 99%

Collapsibility, composition, and microstructure of loess in China

Liu

et al. 2016

Can. Geotech. J.

240

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The collapse potential, mineralogy, microstructure, and particle morphology of a loess from the Loess Plateau, China, were characterized by double oedometer testing, X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and image analysis to elucidate the origin of its collapse behavior. Results show that the loess is highly collapsible with a maximum collapse index of 6.7% at a vertical stress of ∼200 kPa. The deposit contains both nonclay (i.e., quartz, albite, muscovite, and calcite) and clay (i.e., two chlorites) minerals. Microstructural, chemical, and image analyses indicate that interparticle calcite and clay cementation and silt particle morphology render the intact soil a metastable structure. Wetting-induced collapse is attributed to both primary and secondary microstructure features. The former is the abundance of weakly cemented, unsaturated, porous pure clay and clay–silt mixture aggregates whose slaking upon wetting initiates the overall structural collapse, while the latter consists of high porosity, unstable particle contacts, and clay coating on silt particles that act synergistically to augment the collapse. A conceptual microstructural model of a four-tiered hierarchy (i.e., primary clay and silt particles, clay aggregates and clay-coated silt particles, clay–silt mixture aggregates, and cemented aggregate matrix) is proposed to represent its structural characteristics and to account for its high collapsibility.

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Characterization of loess in central Spain: a microstructural study

Cited by 39 publications

References 48 publications

Loess and soils in the eastern Ebro Basin

Loess and soils in the eastern Ebro Basin

Origins and genesis of loess deposits in central Spain, as indicated by heavy mineral compositions and grain‐size variability

Collapsibility, composition, and microstructure of loess in China

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