Paleocurrent direction measurements in a volcanic setting by means of anisotropy of magnetic susceptibility : a case study from the lower Miocene Tepoztlán Formation (Transmexican Volcanic Belt, Central Mexico)

Sources of ancient volcanic rocks are often unknown if they are either eroded and/or covered by younger deposits. This problem, as well as the provenance of reworked volcaniclastic, fluvial and mass-flow deposits, can be partially solved by the application of anisotropy of the magnetic susceptibility (AMS). For massive and poorly sorted volcaniclastic rocks in particular this may be the only way of finding reliable transport directions and therefore allowing for paleogeographic reconstructions. Here, we present a data set of 428 AMS measurements and 249 measurements of sedimentary paleocurrent indicators from the Miocene Tepoztlán Formation at the southern edge of the Transmexican Volcanic Belt (Central Mexico). The highest degree of reliability of AMS measurements is gained for data from lava samples and the lowest from mass flows. Sedimentary structures in sandstones and conglomerates such as trough cross-stratification, asymmetric ripple marks, and the shape of scours and channels could be used to calibrate the results from AMS data and to prove their reliability. AMS data on fluvial deposits point to a drainage systemwith aW–E flow direction, indicating an outflow of the river system into the ancient Gulf of Mexico.Deutsche Forschungsgemeinschaft,project HI 643/5-1.Conacyt (grant 46213)http://www.elsevier.com/locate/sedgeohb201

Magnetic parameters as proxies for anthropogenic pollution in water reservoir sediments from Mexico: an interdisciplinary approach

We assess the element pollution level of water reservoir sediments using environmental magnetism techniques as a novel approach. Although “La Purísima” Water Reservoir is an important source for multiple activities (e.g. recreational, fishing and agricultural) in Guanajuato state, it has been receiving for the last centuries a high load of pollutants by mining extraction, urbanization and land-use change from the Guanajuato Hydrological Basin. The analyses of environmental magnetism, geochemistry, X-ray energy dispersive spectroscopy, scanning electron microscopy and multivariate methods were applied to study sediments from the reservoir and basin. Accordingly, they indicate the presence of iron oxides (magnetite and hematite) and iron sulfides (pyrite and greigite), which evidences relevant differences in particle size and concentration within the water reservoir (median mass-specific magnetic susceptibility χ = 23.2 × 10−8 m3/kg), as well as with respect to the river basin sediments (median χ = 88.8 × 10−8 m3/kg). The highest enrichment factor EF values (median values of EF = 2–10 for As, Co, Ba, Cu, Cd, Ni and EF > 20 for S) are mainly associated with historical mining activities that have led to an enrichment of potentially toxic elements on these water reservoir sediments. We propose the use of concentration and grain size dependent magnetic parameters, i.e. χ, remanent magnetizations and anhysteretic ratios ARM/SIRM and χARM/χ, as proxies for Ba, Co, Cr, Ni, P and Pb pollution in these river and water reservoir sediments. Such parameters allow to evaluate this sedimentary environment, and similar ones, through useful and convenient proxies.Fil: Chaparro, Marcos Adrián Eduardo. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Ramírez Ramírez, Margarita. Universidad de Guanajuato. División Ciencias de la Vida; MéxicoFil: Chaparro, Mauro Alejandro Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Matemática; ArgentinaFil: Miranda Avilés, Raúl. Universidad de Guanajuato; MéxicoFil: Puy Alquiza, María Jesús. Universidad de Guanajuato; MéxicoFil: Böhnel, Harald N.. Universidad Nacional Autónoma de México. Centro de Geociencias; MéxicoFil: Zanor, Gabriela Ana. Universidad de Guanajuato. División Ciencias de la Vida; Méxic

Build-up and depositional dynamics of an arc front volcaniclastic complex : the Miocene Tepoztlán Formation (Transmexican Volcanic Belt, Central Mexico)

Volcanic terrains such as magmatic arcs are thought to display the most complex surface environments on Earth. Ancient volcaniclastics are notoriously difficult to interpret as they describe the interplay between a single or several volcanoes and the environment. The Early Miocene Tepoztla´n Formation at the southern edge of the Transmexican Volcanic Belt belongs to the few remnants of this ancestral magmatic arc, and therefore is thought to represent an example of the initial phase of evolution of the Transmexican Volcanic Belt. Based on geological mapping, detailed logging of lithostratigraphic sections, palaeocurrent data of sedimentary features and anisotropy of magnetic susceptibility, mapping of two-dimensional panels from outcrop to field scale, and geochronological data in an area of ca 1000 km2, three periods in the evolution of the Tepoztla´n Formation were distinguished, which lasted around 4 Myr and are representative of a volcanic cycle (edifice growth phases followed by collapse) in a magmatic arc setting. The volcaniclastic sediments accumulated in proximal to medial distances on partly coalescing aprons, similar to volcanic ring plains, around at least three different stratovolcanoes. These volcanoes resulted from various eruptions separated by repose periods. During the first phase of the evolution of the Tepoztla´n Formation (22Æ8 to 22Æ2 Ma), deposition was dominated by fluvial sediments in a braided river setting. Pyroclastic material from small, andesitic–dacitic composite volcanoes in the near vicinity was mostly eroded and reworked by fluvial processes, resulting in sediments ranging from cross-bedded sand to an aggradational series of river gravels. The second phase (22Æ2 to 21Æ3 Ma) was characterized by periods of strong volcanic activity, resulting in voluminous accumulations of lava and tuff, which temporarily overloaded and buried the original fluvial system with its detritus. Continuous build-up of at least three major volcanic centres further accentuated the topography and, in the third phase (21Æ3 to 18Æ8 Ma), mass flow processes, represented by an increase of debris flow deposits, became dominant, marking a period of edifice destruction and flank failures

Evidence for geomagnetic excursions recorded in Brunhes and Matuyama Chron lavas from the trans‐Mexican volcanic belt

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99072/1/arar_methodology.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/99072/2/jgrb50214.pd

Fine air pollution particles trapped by street tree barks: In situ magnetic biomonitoring

Particulate air pollution in cities comprises a variety of harmful compounds, including fine iron rich particles, which can persist in the air for long time, increasing the adverse exposure of humans and living things to them. We studied street tree (among other species, Cordyline australis, Fraxinus excelsior and F. pensylvanica) barks as biological collectors of these ubiquitous airborne particles in cities. Properties were determined by the environmental magnetism method, inductively coupled plasma optical emission spectrometry and scanning electron microscopy, and analyzed by geostatistical methods. Trapped particles are characterized as low-coercivity (mean ± s.d. value of remanent coercivity Hcr = 37.0 ± 2.4 mT) magnetite-like minerals produced by a common pollution source identified as traffic derived emissions. Most of these Fe rich particles are inhalable (PM2.5), as determined by the anhysteretic ratio χARM/χ (0.1–1 μm) and scanning electron microscopy (<1 μm), and host a variety of potentially toxic elements (Cr, Mo, Ni, and V). Contents of magnetic particles vary in the study area as observed by magnetic proxies for pollution, such as mass specific magnetic susceptibility χ (18.4–218 × 10−8 m3 kg−1) and in situ magnetic susceptibility κis (0.2–20.2 × 10−5 SI). The last parameter allows us doing in situ magnetic biomonitoring, being convenient because of species preservation, measurement time, and fast data processing for producing prediction maps of magnetic particle pollution. “magnetic biomonitoring using street tree bark is convenient because of measurement time and fast data processing for producing maps of particle air pollution”.Fil: Chaparro, Marcos Adrián Eduardo. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Chaparro, Mauro Alejandro Eduardo. Universidad Nacional de Mar del Plata. Facultad de Cs.exactas y Naturales. Centro Marplatense de Investigaciones Matematicas.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Castañeda Miranda, Ana Gabriela. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Marié, Débora Carolina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Gargiulo, José Daniel. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; ArgentinaFil: Lavornia, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Tierra del Fuego, Antártida e Islas del Atlántico Sur. Instituto de Ciencias Polares, Ambientales y Recursos Naturales; ArgentinaFil: Natal, Marcela Liliana. Universidad Nacional de Mar del Plata. Facultad de Cs.exactas y Naturales. Centro Marplatense de Investigaciones Matematicas.; ArgentinaFil: Böhnel, Harald N.. Universidad Nacional Autónoma de México. Centro de Geociencias; Méxic

El uso de parámetros magnéticos en estudios paleolimnológicos en Antártida

En esta contribuci&oacute;n se describen las distintas t&eacute;cnicas y mediciones magn&eacute;ticas utilizadas en Magnetismo Ambiental y Paleomagnetismo. Tales mediciones ofrecen &uacute;tiles indicadores para realizar estudios relacionados con cambios clim&aacute;ticos y ambientales, as&iacute; como herramientas de dataci&oacute;n. Si bien es ampliamente conocida la utilidad de la susceptibilidad magn&eacute;tica, en primer lugar se discute el potencial y necesidad del uso de par&aacute;metros adicionales obtenidos a partir de mediciones de magnetizaciones remanentes (natural, anhist&eacute;rica e isot&eacute;rmica), hist&eacute;resis magn&eacute;tica y estudios termomagn&eacute;ticos. A continuaci&oacute;n se presentan resultados magn&eacute;ticos obtenidos en sedimentos lacustres del Archipi&eacute;lago James Ross (NE de la Pen&iacute;nsula Ant&aacute;rtica) como un caso de estudio. Se complementa con estudios sedimentol&oacute;gicos, hidroqu&iacute;micos, geoqu&iacute;micos y de estad&iacute;stica multivariada, pero se pone &eacute;nfasis en los par&aacute;metros magn&eacute;ticos y su relaci&oacute;n con los distintos procesos que ocurren en los sistemas lacustres ant&aacute;rticos. Se analiza adem&aacute;s el uso de las paleointensidades relativas como herramienta de dataci&oacute;n en lagunas ant&aacute;rticas

Evaluation of the multispecimen parallel differential pTRM method: a test on historical lavas from Iceland and Mexico

Accepted versio

El uso de parámetros magnéticos en estudios paleolimnológicos en Antártida

En esta contribución se describen las distintas técnicas y mediciones magnéticasutilizadas en Magnetismo Ambiental y Paleomagnetismo. Tales mediciones ofrecen útilesindicadores para realizar estudios relacionados con cambios climáticos y ambientales,así como herramientas de datación. Si bien es ampliamente conocida la utilidad de lasusceptibilidad magnética, en primer lugar se discute el potencial y necesidad del uso deparámetros adicionales obtenidos a partir de mediciones de magnetizaciones remanentes(natural, anhistérica e isotérmica), histéresis magnética y estudios termomagnéticos. Acontinuación se presentan resultados magnéticos obtenidos en sedimentos lacustresdel Archipiélago James Ross (NE de la Península Antártica) como un caso de estudio.Se complementa con estudios sedimentológicos, hidroquímicos, geoquímicos y deestadística multivariada, pero se pone énfasis en los parámetros magnéticos y su relacióncon los distintos procesos que ocurren en los sistemas lacustres antárticos. Se analizaademás el uso de las paleointensidades relativas como herramienta de datación enlagunas antárticas

Paleocurrent direction measurements in volcanic settings by means of anisotropy of magnetic susceptibility: A case study from the Lower Miocene Tepoztlán Formation (Transmexican Volcanic Belt, Central Mexico)

Sources of ancient volcanic rocks are often unknown if they are either eroded and/or covered by younger deposits. This problem, as well as the provenance of reworked volcaniclastic, fluvial and mass-flow deposits, can be partially solved by the application of anisotropy of the magnetic susceptibility (AMS). For massive and poorly sorted volcaniclastic rocks in particular this may be the only way of finding reliable transport directions and therefore allowing for paleogeographic reconstructions. Here, we present a data set of 428 AMS measurements and 249 measurements of sedimentary paleocurrent indicators from the Miocene Tepoztlán Formation at the southern edge of the Transmexican Volcanic Belt (Central Mexico). The highest degree of reliability of AMS measurements is gained for data from lava samples and the lowest from mass flows. Sedimentary structures in sandstones and conglomerates such as trough cross-stratification, asymmetric ripple marks, and the shape of scours and channels could be used to calibrate the results from AMS data and to prove their reliability. AMS data on fluvial deposits point to a drainage system with a W–E flow direction, indicating an outflow of the river system into the ancient Gulf of Mexico