The Younger Dryas black mat from Ojo de Agua, a geoarchaeologicalsite in Northeastern Zacatecas, Mexico

New explorations in the desert of northeastern Zacatecas, in central-northern Mexico, revealed dozens ofarchaeological and geoarchaeological sites. One of them, Ojo de Agua, contains the remains of a Pleis-tocene spring-fed hydrographic system located at the southeastern end of a large elongated endorheicbasin. The locality yielded a particularly dark, highly organic stratigraphic layer commonly known in theAmericas as Black Mat (BM), exposed on the natural profiles of a creek, but not associated with culturalmaterials. Several radiocarbon assessments confirmed the formation of the Ojo de Agua Black Mat duringthe Younger Dryas chronozone, with ten calibrated results clustering between 12,700e12,100 cal BP. Thismulti-proxy study confirmed the peculiarity of the deposit and found similarities and differences withother contexts of Younger Dryas age. The Ojo de Agua Black Mat (stratum C2) is far richer in charcoalspecks than the related strata, but lacks phytoliths, diatoms or ostracods. No further biological remainswere found in it, except for intrusive capillary roots. Clearly water-lain in a shallow pond, the stratumqualifies as a clayey silt with an acidic-to-neutral pH. Rich in heavy metals and with high contents oftitanium, the Ojo de Agua Black Mat yielded significant indicators of intense wildfires during the YoungerDryas, but produced no carbon spherules or nanodiamonds supposedly linked to the impact theory

Ética profesional en educación superior : finalidades, estrategias y desafíos de la formación

Todo proyecto educativo que no responde a su época se expone a problemas de legitimidad y al duro escrutinio y sanción de los usuarios. Las instituciones de educación superior no son la excepción de esta premisa clásica, incluso más validada por eldinamismos, la versatilidad y ojo crítico en el mundo contemporáneo. La ética se ha convertido en el baremo principal para someter a juicio a las instituciones y a las personas que ahí actuan, como a las finalidades que se pretenden en sus acciones. En esta perspectiva, debe examinarse la función de las instituciones de educación superior.Este libro es el esfuerzo colectivo por acercarnos a esa problemática, en especial a las finalidades, estrategias y relaciones en juego para cumplir la tarea de la formación y sus nexos inevitables con la ética profesional

Propiedades magnéticas y arqueointensidades de cerámicas teotihuacanas /

 tesis que para obtener el grado de Doctor en Ciencias de la Tierra, presenta María G. Rodríguez Ceja ; asesor Avto Gogichaishvili. iv, 170, 12 páginas : ilustraciones

AMS 14C Dating of the Mayan Codex of Mexico Revisited

The Mayan Codex of Mexico (MCM), the only Mayan codex found in the 20th century, was unveiled in 1971 during the Ancient Maya Calligraphy exhibition at Club Grolier. The codex comprises 10 pages of bark paper in accordion format, coated with a layer of plaster on both sides. It illustrates the synodic cycles of Venus, with its four phases. Since its discovery, the MCM has been subject to controversy and discussions about its authenticity. In 2016, a group of specialists led by Baltazar Brito chief of the National Library of Anthropology and History, carried out an exhaustive study of the codex with the purpose of determining its temporality and authenticity. In this work, the pre-Columbian authenticity of the codex is verified by the radiocarbon (14C) technique using AMS. Two cleaning procedures were contrasted: the standard acid-base-acid (ABA) protocol and a second one with Soxhlet plus ABA. Results obtained when samples were prepared following ABA protocol only, placed the age of the bark paper between 991 and 1147 cal AD. The second cleaning method with Soxhlet plus ABA, resulted in younger ages, between 1159 and 1261 cal AD. However, we consider that when Sohxlet is used as part of the cleaning protocol, organic contaminants are reduced to a minimum, and 14C dates are more reliable. These results indicate that the vegetal support of the MCM belongs to Postclassical Mayan period and place it as the oldest known manuscript of America found to date.6 month embargo; published online by Cambridge University Press: 01 September 2020This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Influencia de paclobutrazol en el crecimiento de brotes y rendimiento de "Psidum guajava" L. en alta densidad

Application of bioregulators is a common practice in several temperate and tropical and subtropical crop fruits to: control vegetative growth, stimulate flowering and fruit set. Paclobutrazol “PBZ” is among those products; however there is few information of its response in guava. Therefore, it was evaluated the application of PBZ on the annual sprout growth dynamic and on the fruit yield of eight guava genotypes established in a high planting density (5 000 plants ha -1 ). The study was carried out at the Experimental Site of “Los Cañones”, during two production cycles. The PBZ treatments were: 0, 1 and 2 ml tree -1 in 2013 and 0 and 1 ml tree -1 in 2015, using the commercial product Austar ® (Paclobutrazol 25%) in both years. The PBZ was applied to the soil around the base of the trunk at the beginning of each cycle, after the pruning. The sprout growth dynamic was measured during 15 weeks after de PBZ was applied in five randomly selected sprouts in one plant of the eight guava genotypes. Daily growth rate (DGR) between each two dates of the sprout growth was estimated. Internodal distance of the same five selected sprouts to measure growth dynamics was registered. At harvest, it was registered: fruit yield, fruit number and the average weight of fruits. The PBZ decreased sprout growth and the internodal distance from 15 to 41%, which was reflected on a lower DGR, being of 4.5 to 6 mm day -1 in the untreated plants, while in the PBZ treated plants DGR was only from 2.8 to 3.9 mm day -1 . In 2013, PBZ significantly increased fruit yield and fruits per plant as compared to the control; however, in 2015 the PBZ did not surpass the control. The outstanding guava genotypes in both years were: Calvillo S-XXI, Selection-12 and Selection-45 with an average of 20.6 kg tree -1 . Palabras clave: Psidum guajava , PBZ, growth regulators; sprout length, fruit quality.La aplicación de bioreguladores es una práctica común tanto en frutales templados como tropicales y subtropicales para controlar el crecimiento vegetativo, estimular floración y amarre de fruto. Tal es el caso del Paclobutrazol “PBZ”, del cual los antecedentes de su respuesta en el cultivo del guayabo son limitados. Por lo anterior, se evaluó la aplicación de PBZ sobre la dinámica de crecimiento de los brotes y producción de fruta de ocho genotipos de guayabo establecidos en un sistema de alta densidad (5 000 plantas ha -1 ). El estudio se realizó en el Sitio Experimental “Los Cañones”, durante dos ciclos de producción, donde se evaluaron tres dosis (0, 1 y 2 ml árbol -1 ) del producto comercial Austar ® (Paclobutrazol 25%) en 2013 y dos en 2015 (0 y 1 ml árbol -1 ). La aplicación se realizó al suelo a la base del tallo al inicio del cada ciclo, después de la poda. La dinámica de crecimiento de los brotes se determinó durante 15 semanas posteriores a la aplicación del PBZ en 5 brotes al azar en una planta por genotipo. Se estimó la tasa de crecimiento diaria (TCD) entre cada dos fechas del registro del crecimiento de los brotes y se midió la longitud de entrenudos a los 140 días. A la cosecha se registró el rendimiento y numero de frutos y el peso medio de fruto. El PBZ disminuyó el crecimiento de los brotes y la distancia entre nudos entre 15 a 41%, lo cual se reflejó en una menor TCD, siendo de 4.5-6 mm día -1 en el testigo, mientras que con PBZ fue de solo 2.8-3.9 mm día -1 . En 2013, el PBZ incrementó significativamente el rendimiento y número de frutos en comparación al testigo; sin embargo, en 2015 el PBZ no superó al testigo. Los genotipos sobresalientes en ambos años fueron: Calvillo S-XXI, Selección-12 y Selección-45 con un promedio de 20.6 kg árbol -1 . Palabras clave: Psidum guajava, PBZ, calidad de fruto, longitud de brotes, reguladores de crecimiento

ESTABLISHING WATER SAMPLE PROTOCOLS FOR RADIOCARBON ANALYSIS AT LAC-UFF, BRAZIL

International audienceABSTRACT Since the establishment of the first radiocarbon accelerator mass spectrometry facility in Latin America in 2009, the Radiocarbon Laboratory team of Universidade Federal Fluminense (LAC-UFF) has worked to improve sample preparation protocols and increase the range of environmental matrices to be analyzed. We now present the preliminary results for DIC sample preparation protocols. The first validation tests include background evaluation with pMC value (0.35 ± 0.04) using bicarbonate dissolved in water. We also analyzed surface seawater resulting in pMC value (101.38 ± 0.38) and a groundwater previously dated from LEMA AMS-Laboratory with pMC value (12.30 ± 0.15)

Casa de los dioses, Nevado de Toluca. Arqueología y cosmovisión de una montaña sagrada.

Este es el tercer libro derivado de las investigaciones del Proyecto Arqueología Subacuática en el Nevado de Toluca de la Subdirección de Arqueología Subacuática del INAH. Con esta obra, se da un importante paso en el conocimiento de las actividades rituales que acontecieron dentro del cráter del volcán. A lo Largo de 13 capítulos escritos por diferentes especialistas, se abordan temas diversos como los objetos arqueológicos localizados en el volcán, los análisis en laboratorio y gabinete de las ofrendas depositadas en el interior de los lagos del Sol y la Luna, aspectos de la cronología arqueológica del valle de Toluca, así como posibles relaciones culturales y temporales entre el volcán y otros sitios arqueológicos de la región. Igualmente, se presentan relatos mitológicos sobre la formación del Nevado de Toluca, la importancia de las entidades acuáticas que regían los cuerpos de agua en las tierras bajas y los lagos del cráter, así como una amplia variedad de temas que aluden a la ritualidad, cosmovisión e identidad de esta montaña sagrada.Desde tiempos inmemorables, el volcán Nevado de Toluca ha sido un referente cultural de su paisaje circundante. En época prehispánica, era considerado una montaña viva y sagrada, donde moraban deidades a las cuales se rendía un culto especial. Las evidencias de este simbolismo han perdurado a lo largo del tiempo en los vestigios arqueológicos y en la cosmovisión de los habitantes de la región. En una Mezcla de la investigación arqueológica con el que hacer artístico, el libro está ilustrado con trabajos del grabador Joel Rendón Vázquez, destacado maestro de la gráfica mexicana. Finalmente, esperamos que esta obra contribuya a la valoración, estudio y protección del Nevado de Toluca: la casa de los dioses.Universidad Autónoma del Estado de México

Evidence of human occupation in Mexico around the Last Glacial Maximum.

The initial colonization of the Americas remains a highly debated topic1, and the exact timing of the first arrivals is unknown. The earliest archaeological record of Mexico-which holds a key geographical position in the Americas-is poorly known and understudied. Historically, the region has remained on the periphery of research focused on the first American populations2. However, recent investigations provide reliable evidence of a human presence in the northwest region of Mexico3,4, the Chiapas Highlands5, Central Mexico6 and the Caribbean coast7-9 during the Late Pleistocene and Early Holocene epochs. Here we present results of recent excavations at Chiquihuite Cave-a high-altitude site in central-northern Mexico-that corroborate previous findings in the Americas10-17of cultural evidence that dates to the Last Glacial Maximum (26,500-19,000 years ago)18, and which push back dates for human dispersal to the region possibly as early as 33,000-31,000 years ago. The site yielded about 1,900 stone artefacts within a 3-m-deep stratified sequence, revealing a previously unknown lithic industry that underwent only minor changes over millennia. More than 50 radiocarbon and luminescence dates provide chronological control, and genetic, palaeoenvironmental and chemical data document the changing environments in which the occupants lived. Our results provide new evidence for the antiquity of humans in the Americas, illustrate the cultural diversity of the earliest dispersal groups (which predate those of the Clovis culture) and open new directions of research