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Search Results: 1 - 10 of 401271 matches for " M;Urrutia-Fucugauchi "
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Rock-magnetic properties of the Cretaceous/Tertiary Micara Formation in the Guantánamo area, eastern Cuba
J. Urrutia-Fucugauchi,J. Pérez-Lazo,M. Fundora,J.M. Espíndola
Geofísica internacional , 1998,
Abstract: Initial results of a rock-magnetic study of the 35 m thick Calabazas sedimentary section of the Micara Formation, eastern Cuba are reported. Previous studies have interpreted the Cretaceous/Tertiary (K/T) boundary within the Micara Formation, based mainly on analyses of planktonic foraminifera assemblages and lateral correlations. The K/T boundary in sedimentary sections in Gubbio, Italy and Caravaca, Spain is characterized, in addition to the iridium anomaly, by a rock-magnetic anomaly that is related to enrichment of iron oxide minerals (magnetite). Study of rock-magnetic properties in the Calabazas section identifies three horizons characterized by increased abundance of magnetic minerals, which are located at about 4, 12 and 20 m above the base of the outcrop, respectively. The 4 m horizon is characterized by magnetic susceptibility values of about 90 x 10-5 SI, whereas in the rest of the section values are around 20 x 10-5 SI. The corresponding NRM and IRM intensities are about 7 mA/m and 7 A/m, respectively. The 12 m horizon is marked by 22 A/m IRM intensity and 14 mA/m NRM intensity. The 20 m horizon is marked by 16 mA/m NRM intensity and 3 A/m IRM intensity. The magnetic anomaly at 4 m corresponds to the highest concentration of magnetic minerals, likely iron-rich fine-grained magnetites with pseudo-single domain behavior. However, this magnetic anomaly in the Calabazas section displays a wider stratigraphic range than in other K/T boundary sections. The characteristics of the wide magnetic anomaly suggest an alternative interpretation in terms of sedimentary input of magnetic material not related to the hot early impact ejecta. The Calabazas section lies in the Paleocene, and the magnetic peaks observed in the sediments result from fluctuations in the relative contents of magnetic minerals.
Absolute Thellier paleointensities from Ponta Grossa dikes (southern Brazil) and the early Cretaceous geomagnetic field strength
Cejudo Ruiz, R;Goguitchaichvili, A;Morales, J;Trindade, R. I. F.;Alva Valdivia, L. M.;Urrutia-Fucugauchi, J;
Geofísica internacional , 2009,
Abstract: we report a detailed rock magnetic and thellier paleointensity study from 130.5 ma ponta grossa dike swarms in southern brazil. twenty-nine samples from seven cooling units were pre-selected for paleointensity experiments based on their low viscosity index, stable remanent magnetization and close to reversible continuous thermomagnetic curves. 19 samples characterized by negative ptrm tests, arai concave-up curves or positive ptrm tests with nrm loss uncorrelated with trm acquisition were rejected. high quality reliable paleointensity determinations are determined from detailed evaluation criteria, with 10 samples belonging to three dikes passing the tests. the site-mean paleointensity values obtained in this study range from 25.6 ± 4.3 to 11.3 ± 2.1 μt and the corresponding vdms range from 5.7 ± 0.9 to 2.5 ± 0.5 (1022 am2). these data yield a vdm mean value of 4.1 ± 1.6 x 1022 am2. significant variability of earths magnetic field strength is observed for ponta grossa dikes with the mean value being significantly lower as compared to the mean vdm obtained from the nearby paraná magmatic province. the paleointensities for the ponta grossa dikes are in agreement with absolute paleointensities retrieved from the submarine basaltic glasses from 130 to 120 ma. it seems that a relatively low field prevailed just before the cretaceous normal superchron.
Short Note: Human Footprints found in Central Mexico could be at least 40,000 years old
A. Gogichaishvili,A. L. Martin-del-Pozo,J. Urrutia-Fucugauchi,A. M. Soler-Arechalde
Geofísica internacional , 2007,
Abstract: Recent studies from genetics of human populations and discoveries of new occupation sites have challenged the conventional model and earlier time framework of the earliest human migration into the American continent. Paleomagnetic analyses of a volcanic ash layer near Valsequillo, central Mexico, yields strong evidence of early arrival of humans in America.
Sedimentation conditions and rock-magnetic properties of Quaternary deposits from Laguna de Santa Rosa, Iturbide region, northeastern Mexico
J. Urrutia-Fucugauchi,M.A. Ruiz-Martínez,J. Werner,H.-W. Hubberten
Geofísica internacional , 2003,
Abstract: We report initial results of an interdisciplinary study of the lacustrine sequence of Laguna de Santa Rosa, based on a 26 m long core recovered from its northern-central sector. The Laguna is an intramontane elongated basin with a small catchment area at an altitude of 1520 m asl in the central sector of the Sierra Madre Oriental in the Iturbide region, northeastern Mexico. The stratigraphic variations of rock-magnetic properties, total carbonate content and isotopic carbon, and mineralogy define three major zones separated by peaks of the calcite to quartz+phyllosilicate+feldspar ratio. The upper zone, from surface to 7-9 m, is formed by an organic clay with abundant gasteropods and two black to green clays. It is characterized by magnetic susceptibility around 10-6 SI, frequency dependent factor of 0 %, δ13 C ranging from –20.3 ‰ at surface to –26.4 ‰, presence of quartz and phyllosilicates with generally more than 20 % calcite, and sporadic occurrence of plagioclase (albite) with K-feldspars nearly absent. The middle zone, from 9 m to 17.5 m, is formed by five clay units with colors ranging from green gray to brown. This zone is characterized by variable susceptibility up to 17 10-6 SI, negative frequency dependent factors, low total carbon content, quartz and phyllosilicate enrichment, less calcite and presence of K-feldspars. This middle zone shows higher detrital input and/or reduced productivity, which suggests a cold and less humid interval. The lower zone extends from 17.5 m to 26 m and shows two brown to green gray clay units. This zone is characterized by magnetic susceptibility between 8 10-6 SI and 14 10-6 SI, variable frequency dependent factors, and δ13 C values around –24 ‰. Its mineralogy is similar to the upper zone, again enriched in calcite and occurrence of plagioclase. The phyllosilicate fraction is mainly composed of mica, chlorite, smectite and kaolinite. The magnetic minerals are allogenic, derived from the lutites that form the catchment basin.
Magnetic characteristics and archeointensity determination on Mesoamerican Pre-Columbian Pottery from Quiahuiztlan, Veracruz, Mexico
López-Téllez, J. M.;Aguilar-Reyes, B;Morales, J;Goguitchaichvili, A;Calvo-Rathert, M;Urrutia-Fucugauchi, J;
Geofísica internacional , 2008,
Abstract: we report a detailed archeomagnetic investigation on pre-columbian potteries from quiahuiztlan, veracruz, from ~900 ad to 1521 ad. archeological samples analyzed by modern magnetic techniques carry a stable univectorial thermoremanent magnetization under alternating field treatment. continuous low-field susceptibility vs. temperature curves performed in air indicates ti-poor titanomagnetites as magnetization carriers. few samples, however, show two ferrimagnetic phases with curie temperatures compatible with both ti-poor and ti-rich titanomagnetites. hysteresis parameter ratios fall essentially in the pseudo-single-domain region, which may indicate a mixture of multi-domain and a significant amount of single domain grains. early geomagnetic field intensity determinations using the coe variant of thellier method were performed on 90 selected samples. cooling rate corrected intensity values range from 34.0 ± 1.2 to 62.2 ± 0.2 μt. corresponding virtual axial dipole moments (vadm) range from 5.7 to 10.7 x1022 am2. absolute intensity curves for mesoamerica present limited spatial/temporal resolution. for tentative dating purposes, we used global archeointensity curves reduced to central and eastern mexico that permit preliminary dating of quiahuiztlan potteries. comparison of our data against those reported in archeoint database allow to identify two periods 900- 1000 and 1400-1600 ad as the most probable manufacturing ranges for the potteries studied.
Marine turtle hatchlings use multiple sensory cues to orient their crawling towards the sea: biological and conservation policy implications  [PDF]
Alma Lilia Fuentes-Farias, Gabriel Gutiérrez-Ospina, Esperanza Meléndez Herrera, Verónica Camarena-Ramírez, Gerardo Ochoa-Tovar, Julieta Mendoza-Torreblanca, Raquel Martínez-Méndez, Jaime Urrutia-Fucugauchi, Armida Báez-Salda?a, María Luisa García Zepeda
Advances in Bioscience and Biotechnology (ABB) , 2011, DOI: 10.4236/abb.2011.22008
Abstract: The ability of sea turtle hatchlings to find the seashore soon after hatching is thought to be exclusively dependent upon visual information. Target-oriented movements in most vertebrates, however, relay on combining information gathered through different sensory systems. Hence, in this work, we investigated whether olfactory and/or magnetic information might complement visual cues during hatchling’s seaward crawling. Acute olfactory deprivation and distorted magnetic sensation in visually competent hatchlings resulted in a scattering of seaward crawling routes among cardinal points, some of them being different from those strongly preferred by control hatchlings. In addition, blindfolded hatchlings also displayed a striking misrouting while crawling on the beach surface in spite of having intact olfactory and magnetic senses. Together these results support the notion that visual information is crucial for seaward crawling, but also that olfactory and magnetic information complement visual cues when turtle hatchlings display this behavior. Hence, the present observations suggest that multisensory cues are used by turtle hatchlings while crawling towards the sea. This work also has important implications on the design of species conservation measures and policies. In the near future, efforts must be made to identify and preserve the local natural sources of odors and magnetic cues, in addition to preventing the perturbing effects of artificial lighting on adult and hatchling turtle crawling behavior.
Chicxulub crater post-impact hydrothermal activity - evidence from Paleocene carbonates in the Santa Elena borehole
Escobar-Sanchez, J. E.;Urrutia-Fucugauchi, J.;
Geofísica internacional , 2010,
Abstract: active hydrothermal systems develop in impact structures formed in marine settings, associated with con-vective processes involving hydrothermal fuids and seawater. here we investigate hydrothermal activity in the chicxulub crater, which was formed by a large impact on the yucatan carbonate platform in the southern gulf of mexico at the cretaceous/tertiary boundary. the post-impact cover carbonate sediments carry a record of con-vective hydrothermal activity, which allow investigating on characteristics and timing/duration of the processes. we present the major and trace element geochemistry of basal paleocene carbonate sediments (304-332 m depth) in the santa elena borehole located south of the crater rim outside of the main basin. hydrothermal activity is evidenced in the major oxides and trace elements, enriched in the frst 10 m above the impact breccia-carbonates contact. basal limestones present high concentrations of silica, magnesium, aluminum, potassium and iron, with similar variation patterns in the other oxides and the trace element data. the geochemical data are consistent with element enrichment associated with hydrothermal input and less likely to result from other processes like diagenesis or detrital contributions. the relative contents of major oxides remain constant in the next twelve meters of the section above 322 m, with cao around 50 % wt and sio2 and mgo around 2 % wt and similar pattern in other oxides and trace elements. considering location of the study site away from the central zone, the geochemical anomalies may arise from convective activity on the underlying impact breccia sequence and input to the water column associated with the distal hydrothermal vent sources in the central area. concentration in fe, k and al is suggestive of a step pattern, also observed in the trace elements (zn, v, cr, ni, cu, zr and rb). after cessation of the active hydrothermal phase after ~1 ma following the impact, intermittent hydrothermal venting may have
Magnetic mineral study of Holocene marine sediments from the Alfonso Basin, Gulf of California: implications for depositional environment and sediment sources
Pérez-Cruz, L;Urrutia-Fucugauchi, J;
Geofísica internacional , 2009,
Abstract: results of a rock magnetic study of marine sediments from the alfonso basin, bay of la paz are used to investigate sediment sources and depositional environment in the southern gulf of california during the holocene. radiocarbon dating provides stratigraphic control, with age for the core bottom sediments of 7597-7831 cal. yr b.p. magnetic signal is dominated by fine-grained titanomagnetites, derived from the silicic volcanic units surrounding the bay of la paz. magnetic mineralogy is relatively homogenous as seen in bulk magnetic properties of low-field susceptibility, remanent intensity and coercivity. magnetic hysteresis loops show strong variable paramagnetic components; after paramagnetic correction loops show saturation at low fields and high saturation magnetization values. plots of hysteresis parameter ratios for domain state show that samples group in the pseudo-single domain field, with mixtures of single and multi-domain particles. magnetic susceptibility log shows relatively high frequency dependence factors, particularly for the middle holocene, suggesting contribution of fine-grained superparamagnetic minerals related to eolian deposition. the well-preserved laminated sequence indicates predominant anoxic conditions in the basin floor. depositional environment had a dominant supply of pluvial detrital sediments and eolian fine-grained dust composed of siliciclastic volcanically-derived material with less abundant biogenic input.
Cooling rate effects on the magnetization of volcanic rocks: Some implications for paleointensity determination
Morales, Juan;Goguitchaichvili, Avto;Urrutia-Fucugauchi, Jaime;
Geofísica internacional , 2006,
Abstract: effects of variation of cooling rate in the acquisition of thermoremanent magnetization (trm) are analyzed on a suite of volcanic rocks. we use a three-step cooling rate experimental procedure applied at three distinct temperatures of trm acquisition. sixteen selected, thermally stable samples from late quaternary lava flows were given a ptrm (300°c) at a slow cooling rate. the acquired intensities were measured at room temperature. a second ptrm was applied to the same specimens using a fast cooling rate, and the acquired intensities were measured at room temperature. finally a third ptrm was induced as in the first step, using a slow cooling rate. the procedure was repeated to create ptrm's at higher temperatures of 450° and 550°c. corresponding percent variations between magnetization intensities acquired at slow-fast and at slow-slow cooling rates were calculated to investigate the influence of cooling rate on trm intensity acquisition, and on trm acquisition capacity. we observe values as high as 300 % in the former case (300 °c). intensity of the ancient geomagnetic field obtained from volcanic rocks could be overestimated by at least 15% due to a variation in cooling rate normally employed in the laboratory, as compared to slower rates found in nature.
Paleomagnetic results for the Middle-Miocene continental Suchilquitongo Formation, Valley of Oaxaca, southeastern Mexico
J. Urrutia-Fucugauchi,I. Ferrusquía-Villafranca
Geofísica internacional , 2001,
Abstract: The Suchilquitongo Formation of the northeastern Valley of Oaxaca is a thick sequence of thin-bedded tuffaceous sandstones and siltstones, which locally contain Hemingfordian mammal fauna, and interbedded lacustrine limestones and rhyolitic tuffs (Etla Ignimbrite). Three new K-Ar dates of biotite and plagioclase concentrates from the Etla Ignimbrite yield an age of about 19-20 Ma. Well-defined reverse polarity paleomagnetic directions are recovered by alternating field demagnetization from 40 samples distributed in 5 sites. The overall mean direction for the Suchilquitongo Formation is B = 5, Dec = 190.9°, Inc = -37.7°, a95 = 6.0°, and k = 165, and the pole position lies at 79.0° N, 330.6° E. This direction deviates from the expected direction (Dec = 176°, Inc = -30°) for the Oaxaca Valley, by a 15° clockwise discordance in declination. A double rotation correction to compensate for structural deformation using a 20° plunge and a 10° bedding dip results in a corrected direction and pole position of Dec = 178.6°, Inc = -30.9° (88.6°N, 151.5°E), which agrees within the statistical uncertainties with the expected direction. The anisotropy of magnetic susceptibility principal axes for the Etla Ignimbrite are characterized by large angular dispersion, which does not permit to infer the flow directions and possible source location.
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