Magnetic Susceptibility Properties of Loess From the Willendorf Archaeological Site: Implications for the Syn/Post-Depositional Interpretation of Magnetic Fabric

At the Willendorf site Upper Paleolithic archeological layers associated to early Aurignacian cultures were found. The environmental conditions of the associated society, potentially co-existing with Neanderthal groups, is still not fully understood. Here, we report on environmental magnetic analyses including anisotropy of the magnetic susceptibility (AMS) carried out on loessic aeolian sediments at the Willendorf site. Data on lineation, foliation and the degree of anisotropy were used to assess depositional and post-depositional magnetic fabric properties and to deduce site-specific environmental processes. Overall, the loess is of aeolian origin and shows magnetic enhancement and magnetic fabric properties similar to those of other European loess geoarchives, but the magnetic mineralogy differs from many ‘dry’ loess sites, insofar as it shows a higher susceptibility during heating. We infer an enhanced neoformation of magnetite during heating due to the presence of organic matter. While at face value the AMS properties are indicative of pure aeolian loess consistent with previous studies, imbrication suggests post-depositional slope movement toward the Danube, which obscures inferences on palaeo-wind direction. It is well possible that these post-depositional magnetic fabric alterations occur at other localities with similar geomorphological settings.

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Anisotropy of magnetic susceptibility (AMS) of lava and volcanoclastic flows of the Stephano-Permian Cadi basin (central-eastern Pyrenees)

10.5194/egusphere-egu2020-10284 ◽

2020 ◽

Author(s):

Ana Simon-Muzas ◽

Antonio M Casas-Sainz ◽

Ruth Soto ◽

Josep Gisbert ◽

Teresa Román-Berdiel ◽

...

Keyword(s):

Magnetic Susceptibility ◽

Flow Direction ◽

Anisotropy Of Magnetic Susceptibility ◽

Lava Flows ◽

Magnetic Fabric ◽

Magnetic Mineralogy ◽

Thin Sections ◽

Andesitic Lava ◽

Magnetic Fabrics ◽

Standard Specimens

The aim of this work is to apply the anisotropy of magnetic susceptibility (AMS) to determine the primary and tectonic fabrics of lava flows and volcanoclastic materials in one of the Pyrenean Stephano-Permian basins.The Pyrenean Range is a double vergence orogen located at the northern end of the Iberian Peninsula. During Carboniferous-Early Permian times the extensional or transtensional regime dominant during the progressive dismantling of the Variscan belt resulted in the development of E-W elongated intra-mountainous basins. This process was coeval with an exceptional episode of magmatic activity, both intrusive and extrusive. The Cad&#237; basin represents a good example of these structures were Stephano-Permian rocks are aligned along an E-W continuous outcrop and reach thickness of several hundreds of meters. The stratigraphy of the study area is characterized by fluviolacustrine sediments changing laterally to volcanoclastic and pyroclastic rocks with interbedded andesitic lava flows. &#160;A total of 75 sites (733 standard specimens) were studied and analysed throughout the volcanoclastic, volcanic and intrusive materials of the Stephano-Permian outcrops in the Cad&#237; basin. Samples were drilled in the field along 5 sections with N-S or NW-SE direction in the Grey and Transition Unit. Afterwards, standard specimens were measured in a Kappabridge KLY-3 (AGICO) at the Zaragoza University to characterise the magnetic fabric. The susceptibility bridge combined with a CS-3 furnace (AGICO) was used for the temperature-dependent magnetic susceptibility curves (from 20 to 700 &#176;C) to recognize the magnetic mineralogy. In addition, textural and mineralogical recognition in thin-sections of the samples was carried out in order to recognize the relationship between magnetic and petrographic fabrics.The results shows that the bulk magnetic susceptibility of the specimens ranges between 118 and 9060&#183;10-6 SI but most of the values are bracketed between 160 to 450&#183;10-6 SI. Taking into account magnetic parameters (Km, Pj and T) there is no correlation between magnetic fabrics and magnetic mineralogy and there is a dominance of triaxial and prolate ellipsoids. Thermomagnetic curves indicate the dominance of paramagnetic behaviour in all the samples and except in one case there is a ferromagnetic contribution due to the generalised presence of magnetite.Magnetic ellipsoids can be divided into four main types depending on the orientation of the main axes and associated with the lithologic types: 1) Kmax vertical and Kint and Kmin horizontal for small intrusive bodies (no restoring); 2) Kmax horizontal or subhorizontal and Kint and Kmin included in a subvertical plane (before and after restitution) for volcanic breccias; 3) Kmin vertical (after restoring) and three directional maxima for lava flows and 4) non-defined fabric for the explosive materials (probably due to their complex depositional mechanisms). In general, a dominant E-W magnetic lineation is observed in many sites, resulting either from dominant flow direction, or to secondary processes. This is the case for some of the magnetic ellipsoids, that seems to be affected by deformation, Kmin is not normal to bedding and therefore, they do not become vertical after bedding restitution.

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Mineralogical control on the magnetic anisotropy of lavas and ignimbrites: a case study in the Caviahue-Copahue field (Argentina)

Geophysical Journal International ◽

10.1093/gji/ggz483 ◽

2019 ◽

Vol 220 (2) ◽

pp. 821-838 ◽

Cited By ~ 2

Author(s):

Thiago R Moncinhatto ◽

Maurício B Haag ◽

Gelvam A Hartmann ◽

Jairo F Savian ◽

Wilbor Poletti ◽

...

Keyword(s):

Magnetic Susceptibility ◽

Magnetic Anisotropy ◽

Flow Direction ◽

Volcanic Rocks ◽

Anisotropy Of Magnetic Susceptibility ◽

Lava Flows ◽

Magnetic Fabric ◽

Volcanic Complex ◽

Magnetic Mineralogy ◽

Southern Volcanic Zone

SUMMARY Anisotropy of magnetic susceptibility is a petrofabric tool used to estimate the alignment of minerals at the site-scale, the imbrication between the magnetic foliation and the emplacement surface being an indicator of flow direction. However, despite numerous studies examining the flow direction in pyroclastic deposits and lava flows, the effect of magnetic mineralogy and the domain state of ferromagnetic phases on the magnetic fabric remains poorly understood. This paper describes the magnetic mineralogy and its influence on the magnetic fabric of Plio-Pleistocene lava flows and ignimbrites of the Caviahue-Copahue Volcanic Complex in the Andean Southern Volcanic Zone, Argentina. Rock magnetism, anisotropy of magnetic susceptibility and anhysteretic remanent magnetization and petrographic observations were performed on 30 sites of the volcanic complex. Results revealed the extrusive and pyroclastic rocks present varied magnetic mineralogy, formed in different stages of the magmatic evolution. Magnetic mineralogy variations strongly affect the anisotropy of magnetic susceptibility data in volcanic rocks and associated ignimbrites, providing ‘scattered’ fabrics when late Ti-rich titanomagnetite phases dominate the fabric, and ‘inverse’ or ‘intermediate’ fabrics when single-domain grains are present. ‘Normal’ fabrics are typically found when early crystallized pure magnetite is present. Our results highlight the complexity in the interpretation of magnetic anisotropy data in volcanic rocks and ignimbrites.

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AMS of strained shales fragments: a fast way to quantify the matrix damage

10.5194/egusphere-egu21-6377 ◽

2021 ◽

Author(s):

Francho Gracia Puzo ◽

Charles Aubourg ◽

Antonio Casas Sainz

Keyword(s):

Rock Magnetism ◽

Magnetic Fabric ◽

Magnetic Minerals ◽

Statistical Characterization ◽

Main Thrust ◽

Rock Fragments ◽

Scalar Data ◽

The Matrix ◽

Degree Of Anisotropy

With the objective of mapping strain on the footwall of a thrust in an orogenic context (Leyre thrust, South Pyrenean Range), more than 1500 unoriented shale fragments (0.7-6.2 g) have been collected. Scalar data (degree of anisotropy P and shape parameter T), together with ellipse of confidence of individual axes provide a proxy of strain acquired by shales in the footwall of the main thrust (Saur et al. 2020).Normally, sampling is done by two methods: collecting oriented decimetric hand specimens; or drilling 2.5 cm diameter cylinders. This presents the advantage to deal with oriented samples. However, those techniques are time consuming and it is difficult to collect numerous samples in loose materials such as shales. On the contrary, collecting rock fragments presents the net advantage to provide a much better statistical characterization of the site.All samples belong to the Eocene shaly formations from the Jaca Basin. Rock fragments are mostly fractured according to the bedding and/or cleavage surfaces. We demonstrate that the anisotropy parameters P and T maintain their values, regardless the shape and size of fragments. Rock magnetism indicates that AMS is primarily governed by illite, with little contribution of magnetite. AMS provides therefore a proxy of illite organisation within the matrix.In the footwall of the Sierra de Leyre we have defined up to 7 parallel sampling sections, whose traces are perpendicular to the direction of the main thrust. On average, each section is made up of about 10 sampling sites and about 15 fragments are collected per site, covering a few square meters.We are restricted by the dimensions of AGICO holders (8cm3 for cubes, or 10 cm3 for cylinders). It is possible to use an empty 10 cm3 cylinder, which can be filled with smaller fragments of rock. The automatic rotator allows a fast and precise description of the AMS tensor. We removed from analysis low susceptibility, carbonate-rich samples, that show a higher variety of magnetic minerals. All sites present homogenous results at the site scale, but with significant differences with respect to strain. P and T parameters are very sensitive to strain as illite is the dominant carrier. In addition, the ellipse of confidence of the minimum AMS axis (K3) provides a sensitive proxy to characterize the competition between bedding and cleavage.The comparison between the different sections allows to map the areas of damage linked to the propagation of faults associated with the folds. 5 stages of development of the magnetic fabric allows the detection of damage gradients. The mapping has allowed the identification of hidden faults.&#160;&#160;&#160;&#160;This new approach is very promising, and allows much more detailed samplings in difficult areas, providing more robust statistical description of scalar AMS data. This methodology could be useful for the study of outcrops that are difficult to access, and more interestingly, from borehole cuttings.

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Eucalyptus grandis Response to Calcium Fertilization in Colombia

Forest Science ◽

10.1093/forsci/fxab042 ◽

2021 ◽

Author(s):

Zach S Grover ◽

Rachel L Cook ◽

Marcela Zapata ◽

J Byron Urrego ◽

Timothy J Albaugh ◽

...

Keyword(s):

Organic Matter ◽

South America ◽

Eucalyptus Grandis ◽

Application Rate ◽

Soil Conditions ◽

Nutrient Deficiencies ◽

Site Specific ◽

Application Rates ◽

Eucalyptus Plantations ◽

Calcium Source

Abstract Calcium (Ca) is a critical plant nutrient typically applied at the time of planting in intensive Eucalyptus plantations in South America. At two sites in Colombia, we examined (1) calcium source by comparing growth after application of 100 kg ha−1 elemental Ca as lime or as pelletized highly reactive calcium fertilizer (HRCF) compared to a no application control, and (2) Ca rate by applying 0, 100, 200, and 400 kg ha−1 elemental Ca as HRCF with the addition of nitrogen, phosphorus, potassium, sulfur, and boron (NPKSB). We assessed height, diameter, and volume after 12 and 24 months. There were no growth differences from Ca source at the 100 kg ha−1 rate. We found increased volume after 24 months at the “Popayan” site with 200 and 400 kg ha−1 Ca HRCF+NPKSB treatments (112 and 113 m3 ha−1, respectively) compared to control (92 m3 ha−1), a 22% increase. In contrast, volume did not differ after 24 months at the “Darien” site, ranging from 114 m3 ha−1 in the 0 kg ha−1 Ca HRCF+NPKSB treatment to 98 m3 ha−1 in the control. Differences in response are likely due to soil characteristics, such as organic matter, emphasizing the importance of identifying site-specific nutrient deficiencies. Study Implications: Operational applications may be over- or under-applying calcium carbonate in Eucalyptus plantations in South America. In the first two years of a seven-year rotation located in volcanic soils in Colombia, we found that one site with more organic matter at a greater depth did not need Ca additions, whereas the other site required greater than current operational applications to optimize productivity. Ca application rate trials across a gradient of soil conditions could establish critical values and improve recommendations of appropriate Ca application rates and emphasize the importance of understanding site-specific soil conditions to produce effective fertilization regimes.

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On the influence of magnetic mineralogy in the tectonic interpretation of anisotropy of magnetic susceptibility in cataclastic fault zones

Geophysical Journal International ◽

10.1093/gji/ggy481 ◽

2018 ◽

Vol 216 (2) ◽

pp. 1043-1061 ◽

Cited By ~ 4

Author(s):

Teresa Román-Berdiel ◽

Antonio M Casas-Sainz ◽

Belén Oliva-Urcia ◽

Pablo Calvín ◽

Juan José Villalaín

Keyword(s):

Magnetic Susceptibility ◽

Anisotropy Of Magnetic Susceptibility ◽

Fault Zones ◽

Magnetic Mineralogy ◽

Tectonic Interpretation

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The Impact of Grain Size Composition and Organic Matter Content on Magnetic Susceptibility of Anthropogenically Transformed Bottom Sediments, as Exemplified by the Former Naval Harbour in Hel

Magnetometry in Environmental Sciences - GeoPlanet: Earth and Planetary Sciences ◽

10.1007/978-3-319-60213-4_7 ◽

2017 ◽

pp. 91-102

Author(s):

Leszek Łęczyński ◽

Żaneta Kłostowska ◽

Grzegorz Kusza ◽

Tadeusz Ossowski ◽

Bartłomiej Arciszewski ◽

...

Keyword(s):

Grain Size ◽

Magnetic Susceptibility ◽

Organic Matter ◽

Bottom Sediments ◽

Organic Matter Content ◽

Size Composition ◽

Matter Content ◽

Grain Size Composition ◽

The Impact

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Current Understanding of the Use of Alkaline Extractions of Soils to Investigate Soil Organic Matter and Environmental Processes

Journal of Environmental Quality ◽

10.2134/jeq2019.08.0292 ◽

2019 ◽

Vol 48 (6) ◽

pp. 1561-1564 ◽

Cited By ~ 1

Author(s):

Tsutomu Ohno ◽

Nancy J. Hess ◽

Nikolla P. Qafoku

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Current Understanding ◽

Environmental Processes

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Distinguishing the Mélange-Forming Processes in Subduction-Accretion Complexes: Constraints from the Anisotropy of Magnetic Susceptibility (AMS)

Geosciences ◽

10.3390/geosciences9090381 ◽

2019 ◽

Vol 9 (9) ◽

pp. 381 ◽

Cited By ~ 2

Author(s):

Claudio Robustelli Test ◽

Andrea Festa ◽

Elena Zanella ◽

Giulia Codegone ◽

Emanuele Scaramuzzo

Keyword(s):

Magnetic Susceptibility ◽

Late Cretaceous ◽

Anisotropy Of Magnetic Susceptibility ◽

Magnetic Fabric ◽

Early Eocene ◽

Accretionary Complex ◽

Geodynamic Evolution ◽

Structural Investigations ◽

Laboratory Investigations ◽

Magnetic Features

The strong morphological similitude of the block-in-matrix fabric of chaotic rock units (mélanges and broken formations) makes problematic the recognition of their primary forming-processes. We present results of the comparison between magnetic fabric and mesoscale structural investigations of non-metamorphic tectonic, sedimentary, and polygenetic mélanges in the exhumed Late Cretaceous to early Eocene Ligurian accretionary complex and overlying wedge-top basin succession in the Northern Apennines (northwest Italy). Our findings show that the magnetic fabric reveals diagnostic configurations of principal anisotropy of magnetic susceptibility (AMS) axes orientation that are well comparable with the mesoscale block-in-matrix fabric of mélanges formed by different processes. Broken formations and tectonic mélanges show prolate and neutral-to-oblate ellipsoids, respectively, with magnetic fabric elements being consistent with those of the mesoscale anisotropic “structurally ordered” block-in-matrix fabric. Sedimentary mélanges show an oblate ellipsoid with a clear sedimentary magnetic fabric related to downslope gravitational emplacement. Polygenetic mélanges show the occurrence of a cumulative depositional and tectonic magnetic fabric. The comparison of field and laboratory investigations validate the analysis of magnetic features as a diagnostic tool suitable to analytically distinguish the contribution of different mélange forming-processes and their mutual superposition, and to better understand the geodynamic evolution of subduction-accretion complexes.

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Environmental variability and human activity over the past 140 years documented by sediments of Ebinur Lake in arid central Asia

Journal of Limnology ◽

10.4081/jlimnol.2017.1587 ◽

2017 ◽

Cited By ~ 4

Author(s):

Wen Liu ◽

Long Ma ◽

Jinglu Wu ◽

Jilili Abuduwaili

Keyword(s):

Heavy Metal ◽

Magnetic Susceptibility ◽

Organic Matter ◽

Central Asia ◽

Human Activities ◽

Arid Central Asia ◽

Ebinur Lake ◽

Metal Contents ◽

The 1960S ◽

Environmental Proxies

A short (50-cm-long) sediment core from Ebinur Lake in arid central Asia has been analyzed for various environmental proxies, including organic matter content, δ13C in organic matter, magnetic susceptibility, heavy metal contents, and stable isotopic compositions of bulk carbonate (δ18O and δ13C). The results reveal that the evolutionary stages inferred from environmental indicators have an asynchronous nature. If the asynchrony of periodic changes in multi-environmental proxies is ignored, important information may be lost, especially regarding anthropogenic influences. On the basis of magnetic susceptibility and heavy metal contents, human activities appear to have resulted in increases in surface erosion and measurable heavy-metal accumulation from the mid-1960s, whereas the organic matter contents, which display an obvious shift in the late 1930s, correlate with regional climate. However, the changes in the stable isotopes of bulk carbonate are mainly controlled by the isotopic composition of the host water which is generally consistent with the lake level. From the late 1870s to the 1960s, the lake was in a natural evolutionary state. From the 1960s to the mid-2000s, the runoff feeding Ebinur Lake dropped rapidly, in association with a sharp increase in agricultural development. Finally, beginning in the early twenty-first century, the climate became wetter than during the earlier two stages, and as agricultural water demand decreased, surface runoff once again increased. It is noted that, although the different proxies respond differently to climate changes and human activities, any analysis of environmental evolution should consider them each individually, in order to fully understand the complex interactions between climate and human influence.

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