Research Interests:
La fábrica magnética de dos secciones de una secuencia continental mesozoica del norte de Oaxaca - sur de Puebla, se interpreta en algunos sitios como de origen primario y en otros secundario. Los criterios de interpretación se basan en... more
La fábrica magnética de dos secciones de una secuencia continental mesozoica del norte de Oaxaca - sur de Puebla, se interpreta en algunos sitios como de origen primario y en otros secundario. Los criterios de interpretación se basan en (i) el grado de anisotropía y su variación en cada sitio, (ii) la geometría de la fábrica magnética y (iii) la comparación de la fábrica con otros indicadores geológicos. La fábrica magnética se obtuvo a partir de la anisotropía de susceptibilidad magnética (AMS) en campos bajos, de 122 especímenes provenientes de 10 niveles estratigráficos. La interpretación del origen de la fábrica se relaciona con la mineralogía magnética y con los efectos en la AMS (en especímenes piloto) debido a la impartición de una magnetización remanente isotermal (IRM) y, por el posterior calentamiento a pasos en laboratorio a 130°C y 400°C. La fábrica magnética interpretada como primaria sugiere un sistema de paleocorrientes orientado al NW (270° a 320°) en la sección infe...
Research Interests:
Research Interests:
A palaeomagnetic study have been carried out on the western margin of the Mexico basin. 24 sites from Sierra de Las Cruces were sampled and analyzed in the laboratory. A total amount of 231 samples has been fully demagnetized and a simple... more
A palaeomagnetic study have been carried out on the western margin of the Mexico basin. 24 sites from Sierra de Las Cruces were sampled and analyzed in the laboratory. A total amount of 231 samples has been fully demagnetized and a simple directional magrietic behavior was observed in all samples. The mean direction obtained in this study is 0=353.11=31.6 (N=24 K=28.9 a95=5.6), in agreement with the expected direction. Therefore this area has not been affected by significant block rotations in contrast tb the counterclockwise rotations observed in the easternmost sector of the Transmexican Volcanic Belt (TMVB), towards the Gulf of Mexico, and in its central"western parto In addition a magnetic zonation has beeh observed covering at least the Matuyama and Gauss polarity chrons.
Research Interests:
Abstract The Special Issue on Paleomagnetism and Magnetic Fabrics in Latin America contains twenty-one original contributions ranging from Paleogeography and Tectonics to Paleosecular variation of the Earth Magnetic Field and Magnetic... more
Abstract The Special Issue on Paleomagnetism and Magnetic Fabrics in Latin America contains twenty-one original contributions ranging from Paleogeography and Tectonics to Paleosecular variation of the Earth Magnetic Field and Magnetic Fabrics applications, among others. They are good examples of the state-of-the-art of these disciplines applied to a broad range of Earth Sciences subjects in Latin America.
Research Interests:
Research Interests:
Early efforts for establishing an archeomagnetic reference curve for Mesoamerica failed due to the absence of reliable radiometric dates. Recently, numerous 14C data become available from Central Mexico (Teopancazco and Xalla in... more
Early efforts for establishing an archeomagnetic reference curve for Mesoamerica failed due to the absence of reliable radiometric dates. Recently, numerous 14C data become available from Central Mexico (Teopancazco and Xalla in Teotihuacan area, Xochicalco, Templo Mayor, Tlatelolco, Cholula and Cacaxtla). In light of these new radiometric and magnetic information, we present here an updated secular variation curve for the last two millennia. In addition, a comparative analysis were carried out with southwest North American data (Lengylel and Eighmy , 2001).
Research Interests:
We report paleomagnetic results of thermoremanent magnetization of the lithic clasts and matrix of the Lower Panalillo ignimbrite in the San Luis Potosi Volcanic Field (CVSLP), that provide quantitative estimation of emplacement... more
We report paleomagnetic results of thermoremanent magnetization of the lithic clasts and matrix of the Lower Panalillo ignimbrite in the San Luis Potosi Volcanic Field (CVSLP), that provide quantitative estimation of emplacement temperature range of the lithic-rich proximal facies in the Arroyo El Juachín, from which we sampled 78 specimens of lithic fragments (from 40 cm to less than about 10 cm in size) of the matrix which contains them. The results of the saturation isothermal remanent magnetization, the magnetic susceptibility vs. high temperature curves (k-T) and hysteresis loops suggest that the main magnetic carriers are titanomagnetite, titanohematite and hematite. The k-T curves in rare cases show two different thermomagnetic phases during heating, and the cooling curves show irreversibility indicating the presence of titanomagnetite and titanomaghemite. This study shows two emplacement temperatures for this ignimbrite: one of low temperature (280-360 °C and 440 C, samples ...
Research Interests:
A new archeomagnetic reference curve contains all available and updated results reported since early 70th and 27 new archaeomagnetic directions obtained during last six years. The most of samples are taken from the burned floors and... more
A new archeomagnetic reference curve contains all available and updated results reported since early 70th and 27 new archaeomagnetic directions obtained during last six years. The most of samples are taken from the burned floors and walls. In some case, lime plasters are also used. The age interval covers from 100 BC to present. Alternating field demagnetization were carried out to obtain the directions of primary remanence. Pseudo single grain size titanomagnetite seems to be main magnetic carrier as deduced from rock-magnetic experiments. The active collaboration with the archaeologists proved to be fundamental to better constrain the age of archeological events.
Research Interests:
Since 1999 we have been working on improving the Mesoamerica Secular Variation Curve. We re-sampled some sites that Wolfman initially used in its first proposal of this Curve, such as Teotihuacan, Teopancazco and Tula. Wolfman 's... more
Since 1999 we have been working on improving the Mesoamerica Secular Variation Curve. We re-sampled some sites that Wolfman initially used in its first proposal of this Curve, such as Teotihuacan, Teopancazco and Tula. Wolfman 's curve only had 4 radiocarbon dates directly associated with the sampled sites; the other dating were actually stratigraphic and ceramic correlations. More than 28
Research Interests:
We carried out a reconnaissance rock-magnetic and archeomagnetic investigations of lime-plasters at some most important pre-Hispanic sites in Central Mexico. Both burned and unburned lime plasters (in total 30 samples) were analyzed from... more
We carried out a reconnaissance rock-magnetic and archeomagnetic investigations of lime-plasters at some most important pre-Hispanic sites in Central Mexico. Both burned and unburned lime plasters (in total 30 samples) were analyzed from Teotihuacan, Tlatelolco, Santa Cruz Atizapan and Pañhu. The characteristic directions determined in this study are considered to be of primary origin. Thermomagnetic investigation show that the remanence
Research Interests:
We report here the results of archeomagnetic investigations carried out during last decade at Teotihuacan and surrounding areas. 48 new data are also incorporated into the analysis. The time interval involved is from 200 AD to 600 AD... more
We report here the results of archeomagnetic investigations carried out during last decade at Teotihuacan and surrounding areas. 48 new data are also incorporated into the analysis. The time interval involved is from 200 AD to 600 AD which corresponds to Tlalmimilolpa and Xolalpan chronological phases. The curve was estimated by cubic splines. The stratigraphic control is acomplished with radiocarbon
Research Interests:
Research Interests:
Research Interests:
A través de la datación arqueomagnética de Guachimontones de Teuchitlán, Jalisco, se contribuye a la cronología prehispánica del Occidente de México. A partir de 16 muestras arqueomagnéticas (81 especímenes en total) de hornos, pisos... more
A través de la datación arqueomagnética de Guachimontones de Teuchitlán, Jalisco, se contribuye a la cronología prehispánica del Occidente de México. A partir de 16 muestras arqueomagnéticas (81 especímenes en total) de hornos, pisos quemados y no quemados recolectados en 2005 y 2010, se hicieron mediciones para determinar la dirección media de cada muestra en el Laboratorio de Paleomagnetismo de la UNAM (Ciudad de México y Campus Morelia). Se obtuvieron dataciones arqueomagnéticas con α95 < 10° para el 88% de las muestras y corresponden a las épocas de ocupación del sitio. Este estudio aporta 2 nuevos datos a la <em>curva de variación de Mesoamérica</em>, registra modificaciones arquitectónicas en una edificación y apoya la teoría de reocupación del sitio hacia el periodo Epiclásico (450-900 d. C.). ENGLISH: Guachimontones of Teuchitlan: An Archaeomagnetic Survey to Improve the Chronology of Western Mexico. This study contributes to the pre-Hispanic chronology of Wes...
Research Interests:
El control cronoestratigráfico es fundamental para el desarrollo del trabajo arqueológico, por ello el arqueomagnetismo se ha constituido como una gran herramienta para las dataciones. En este trabajo se muestran los resultados de... more
El control cronoestratigráfico es fundamental para el desarrollo del trabajo arqueológico, por ello el arqueomagnetismo se ha constituido como una gran herramienta para las dataciones. En este trabajo se muestran los resultados de dataciones arqueomagnéticas mediante la determinación de la dirección de magnetización de pisos de estuco de tres sitios de la cultura teotihuacana: Ciudadela de Teotihuacan, Sierra de las Navajas y Xalasco, Tlaxcala. Esta cultura se desarrolló en el centro de México a partir del año 1 d. C., teniendo su mayor esplendor durante los siglos IV al VI d. C. Tres etapas constructivas fueron muestreadas en la ciudadela de Teotihuacan: la preciudadela, la pirámide de Quetzalcóatl y la pirámide adosada. La Sierra de las Navajas en Hidalgo, a 50 km de Teotihuacan, era su principal proveedor de obsidiana, por lo que es de interés conocer sus periodos de ocupación. El motivo del análisis de los pisos de Xalasco, Tlaxcala, sitio de la cultura teotihuacana, es por enco...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
ABSTRACT
Research Interests:
Results of an archaeomagnetic study of two excavation field seasons at the Xalla and Teopancazco residential areas of the ancient Prehispanic city of Teotihuacan, Central Mexico are reported. One-hundred and fifty three oriented samples... more
Results of an archaeomagnetic study of two excavation field seasons at the Xalla and Teopancazco residential areas of the ancient Prehispanic city of Teotihuacan, Central Mexico are reported. One-hundred and fifty three oriented samples of lime-plasters from the two archaeological sites were collected for the study. NRM directions are reasonably well grouped. Alternating field demagnetization shows single or two-component magnetizations. Rock magnetic measurements point to fine-grained titanomagnetites with pseudo-single domain behaviour. Characteristic site mean directions from both sites are correlated to the available palaeosecular variation curve for Mesoamerica. The mean directions obtained from Xalla site point to average dates of 550 AD±25 years that matches with the documented ‘Big Fire’ of Teotihuacan (AD 575). Two consecutive construction levels at Teopancazco were estimated as AD 250–350 and AD 350–425 respectively.
Research Interests:
We collected 21 monogenetic type lava flows (316 specimens) in the Xalapa Volcanic Field, eastern part of the Mexican Volcanic Belt. Geochronological results of twelve Ar-Ar determinations range from late Pleistocene to Holocene. The ages... more
We collected 21 monogenetic type lava flows (316 specimens) in the Xalapa Volcanic Field, eastern part of the Mexican Volcanic Belt. Geochronological results of twelve Ar-Ar determinations range from late Pleistocene to Holocene. The ages fall into three ...
Research Interests:
... This has al-ready been proposed from other analyses of paleo-magnetic data for northwestern North American terrains (eg, Hillhouse, 1977; Jones et al., 1977; Yole and Irving, 1980; Panuska and Stone, 1981; Stone et al., 1982; Gehrels... more
... This has al-ready been proposed from other analyses of paleo-magnetic data for northwestern North American terrains (eg, Hillhouse, 1977; Jones et al., 1977; Yole and Irving, 1980; Panuska and Stone, 1981; Stone et al., 1982; Gehrels and Saleeby, 1987). ...
Research Interests:
Research Interests:
Research Interests:
Anisotropy of Magnetic Susceptibility (AMS) results from a group of 17 - 18 sites (286 - 312 specimens) from the Cantera Ignimbrite - of Oligocene age and part of the San Luis Potosí Volcanic Filed (SLPVF), México - are presented and... more
Anisotropy of Magnetic Susceptibility (AMS) results from a group of 17 - 18 sites (286 - 312 specimens) from the Cantera Ignimbrite - of Oligocene age and part of the San Luis Potosí Volcanic Filed (SLPVF), México - are presented and analysed in order to help to determine the source and flow directions. In each site a flow direction is inferred based on AMS results. As the Cantera Ignimbrite is generally dipping, AMS was structural corrected. So two sets of geographical and paleo-geographical (structural corrected) inferred-flow directions were obtained. Both sets are analysed trying to define if the source of the ignimbrite is related to a calderic (concentric structure) or to the NW-SE faulting and jointing. Geographical AMS results mostly give SW flow directions, the southernmost sites give to SSE. Meanwhile structural corrected results give a wider range of flow directions, a group of them to NW and another northerly group mostly to NE. AMS was measured in a KLY2 appliance, Jeli...