Importancia de la paleoecología de microfósiles en reconstrucciones paleoclimáticas y sitios arqueológicos desde una perspectiva empresarial: ejemplos del sudoccidente norteamericano

El estudio del cambio climático y el impacto antrópico en sitios arqueológicos ha abierto un nuevo sendero en la micropaleontología que ha pasado de su estandarte tradicional a la vanguardista forma de mirar al futuro a través del pasado. La magnitud de este cambio queda grabado en el registro geológico y los micropaleontólogos tenemos la oportunidad única de interpretar e inferir si estos cambios han tenido un impacto en el ambiente físico o social de las comunidades que los instigaron. El sudoccidente norteamericano nos ofrece algunos ejemplos geológicos, prehispánicos y recientes de gran valor para contribuir a nuestro conocimiento sobre el cambio climático e impacto antrópico en los ultimos 11 mil años antes del presente (AP). El espectro de estos estudios micropaleontológicos comienza con el estudio de los canales de irrigación de Las Capas, Tucson, Arizona (Período Agrícola Temprano, 3000 AP a 2000 AP) entre otros en el Valle de Tucson y luego se ha extendido a gran parte de los valles de Phoenix y del Río Gila, incluyendo el vasto acervo de los complejos canales construidos por la civilización Hohokam en los primeros 1450 años de la era cristiana en el valle de Phoenix, Arizona. De ahí, se proyectó a estudios en Texas, Nuevo México, Nevada y California donde las reconstrucciones paleoclimáticas han permitido identificar el Younger-Dryas en las cercanías de Albuquerque, Nuevo México y la transición de la Anomalía Climática Medieval y de la Pequeña Edad del Hielo en el Norte de Texas. Más recientemente, nuevos estudios han permitido identificar la respuesta de los ostrácodos a la presencia de metales pesados en lagos naturales y artificiales como el Lago Patagonia, en Arizona, así como la transición de un ambiente no perturbado a uno seriamente perturbado en tiempos históricos en Ash Meadows National Wildlife Refuge, Nevada. Estos estudios han dado lugar a que algunas personas exploremos la oportunidad de hacer investigación desde la iniciativa privada. Esta ha sido una opción muy valiosa tanto individualmente, como para el potencial mercado.Conferencias plenarias.Facultad de Ciencias Naturales y Muse

Archeological Significance Testing at 41BX17/271, the Granberg Site: A Multi-Component Site along the Salado Creek in Bexar County, Texas

The Center for Archaeological Research (CAR) of The University of Texas at San Antonio conducted archeological significance testing at 41BX17, the Granberg Site, from January to March 2006. The testing was conducted for the Texas Department of Transportation, Environmental Affairs Division (TxDOT-ENV). The Granberg Site sits on the eastern flood terrace of the Salado Creek south of Loop 410 in San Antonio, Bexar County, Texas. Planned road improvements including installation of a storm sewer line and a water main prompted the need to assess whether (1) cultural deposits including human remains still exist after previous testing and (2) if the deposits contribute to the site’s National Register of Historic Places eligibility. The archeological work was conducted under Texas Antiquities Permit No. 4010. Steve A. Tomka served as Principal Investigator and Jennifer Thompson served as Project Archeologist. Fieldwork included mechanical auger boring and backhoe trenching to determine the horizontal extent of the site boundaries within the median of Loop 410 eastbound. Sixteen 1-x-1-m units were excavated to determine the distribution and integrity of the cultural deposits and to locate any possible burials that may still exist at the site. Materials recovered included burned rock features, chipped stone artifacts, animal bone, snail and mussel shell and charred plant remains. The distribution of the artifacts, the geomorphic investigations, the radiocarbon assays, and temporally diagnostic artifacts indicate the presence of Middle and Late Archaic archeological materials with good stratigraphic integrity. The Granberg Site was determined to be ineligible for the National Register of Historic Places. Following the completion of eligibility testing efforts, the TxDOT directed the CAR to develop a research design linking the data recovered from the various excavations at the Granberg Site with research goals. The CAR developed the research design (Munoz et al. 2007) under Work Authorization No. 57513SA005 with Cynthia M. Munoz serving as Project Archeologist. At roughly the time of the research design implementation, the CAR was the recipient of a donation of a collection of commingled human skeletal remains recovered from the Granberg Site. These remains were recovered from 41BX17/271 in 1962 by Harvey Kohnitz, an avocational archeologist, without knowledge or permission from the Texas Highway Department. The remains were stored at the Kohnitz home until his son, Mark Kohnitz, donated them to the CAR in 2007. An osteological analysis was conducted at the CAR laboratory during February 2008 for TxDOT, under Work Authorization No. 57513SA005 Supplemental Work Authorization No. 4. The results of this analysis are reported in Appendix H of this report. The commingled remains will be curated the CAR and all required documents, including an inventory, will be submitted to the National Park Service National NAGPRA Program to fulfill all obligations pertaining to the NAGPRA laws. All artifacts collected during this project and all project-associated documentation are permanently curated at the CAR according to Texas Historical Commission guidelines

Trace element shell chemistry of continental ostracodes and the applicability of experimentally-derived multiple regression models to paleoenvironmental reconstructions in southwestern North America.

Lacustrine ostracodes have been studied during the last three decades because of their apparent utility in reconstructing aquatic paleoenvironments. These microcrustaceans are ideal for paleoenvironmental analysis because: (1) they are cosmopolitan and abundant lacustrine inhabitants; (2) they show high diversity; (3) they are sensitive to climate-related limnological variations; (4) their valves incorporate some trace elements from host waters that may provide information on paleolimnologic conditions; and (5) their valve calcification appears to be in oxygen stable isotopic equilibrium with the host water. I designed a two-part research project to understand the significance of ostracode shell chemistry in response to the environment. First, an experiment to determine the Mg²⁺and Sr²⁺ partition coefficients (K(p)) for Limnocythere staplini, a widely distributed species in North America was executed to establish its applicability to the geologic record. Three hundred specimens of this species were individually cultured in 20 ml capped vials at discrete temperatures (15, 20 and 25 °C) and conductivities (10, 15, 20, 25, 30 μMohs/cm). After the ostracodes molted, the carapaces were removed for Ca²⁺, Mg²⁺, and Sr²⁺ analysis by inductively coupled plasma mass spectrometry (ICP-MS). Ostracode shell chemistry shows that ᵐ(Mg/Ca)(valve} is temperature dependent but not related to ᵐ(Mg²⁺/Ca²⁺)(water}. ᵐ(Sr/Ca)(valve} is dependent on TDS and possibly to ᵐ(Sr²⁺/Ca²⁺)(water}. Experimental results are applicable to a limited number of water bodies within the ranges of these analyses. Second, the equations generated in these experiments were used in a case study from the geologic record to test the applicability of this technique. Las Acequias Hohokam irrigation system provided the material for the first attempt to use ostracode shell chemistry to reconstruct the history of canal operation during Hohokam occupation (8th-15th Century A.D.). One hundred and twenty nine valves of Limnocythere staplini were analyzed by ICP-MS. I studied these valve data and associated information to determine the human water usage patterns and impact on the environment by ancient Native Americans. Current results suggest that experimental ᵐ(Mg/Ca)(valve} ratios may be used as a paleothermometer to reconstruct aquatic paleoenvironments. ᵐ(Sr/Ca)(valve} may prove to be a reliable source for reconstructing paleosalinity. The combined trace element analyses provides a powerful tool for understanding both paleoclimatic and human impact changes. However, paleoenvironmental reconstructions through partition coefficients is not warranted because thermodynamic equilibrium may not exist between water and Limnocythere staplini

Química de conchas de ostrácodos: una alternativa para medir la contaminación por metales de sistemas acuáticos

La acumulación de metales traza en agua, sedimentos y organismos es de la mayor preocupación debido a los numerosos efectos adversos que los metales pesados tienen sobre la salud humana. La rápida industrialización durante el último siglo destaca la importancia y urgencia para entender los efectos que los metales traza tienen sobre el ambiente en los registros históricos. En este estudio documentamos la presencia de metales traza y, por primera vez, la presencia de elementos de las Tierras Raras (excepto Ce) en las valvas de ostrácodos procedentes de tres sitios con diferentes niveles de contaminación. Los ejemplares fueron colectados en la laguna S'Albufera des Grau, Isla Menorca, España, la Isla Lee Stocking, Bahamas y la Laguna de Tamiahua, México. Dos de estas localidades son modernas (México y España), la tercera incluye especímenes históricos y subfósiles (Bahamas). Los elementos reportados en este estudio fueron determinados mediante espectrometría de masas con plasma de argón (ICP-MS por sus siglas en inglés) ajustado a límites de detección de 1 ng_kg-1. La mayoría de los metales pesados en las valvas de ostrácodos muestran patrones de distribución bien definidos para condiciones no contaminadas y contaminadas. Contrario a lo esperado, el Cd y el Pb no mostraron diferencias entre las dos condiciones. Los elementos de las Tierras Raras, en contraste, muestran fuerte afinidad con el Mn en las valvas de ostrácodos, lo que sugiere que su acumulación en ambientes contaminados es el resultado de actividades antrópicas. Estos resultados indican que la química de las valvas de ostrácodos puede emplearse para reconstruir el registro histórico de contaminación de sistemas acuáticos tanto marinos como continentales a partir del análisis de núcleos o materiales subfósiles

Late Quaternary lacustrine ostracods (Ostracoda, Crustacea) and charophytes (Charophyta, Charales) from the Puna Plateau, Argentina

Relatively little is known about the recent palaeontological records of the high-altitude closed basin lakes of the Central Andes, but a great need exists to remedy this knowledge gap if microfossils are to be used to infer climatic and ecological transitions from lake sediment cores. Here, eight species of non-marine ostracods and two calcareous algae are recorded from modern sediments and late Quaternary strata from Laguna de los Pozuelos, Jujuy Province, northwestern Argentina. Four species, Limnocythere alexanderi, Limnocythere foresteri, Limnocythere lysandrosi and Limnocythere ruipunctifinalis, are described as new species. Limnocythere titicaca Lerner-Seggev, 1973 has only been recorded in Lake Titicaca prior to this study and this is the first time the species is recognized outside of Bolivia. The cypridoideans Ilyocypris ramirezi Cusminsky & Whatley, 1996, Eucypris virgata Cusminsky & Whatley, 1996 and Chlamydotheca pseudobrasiliensis Martens & Behen 1994 are known species that are rare in the stratigraphic sequence in core LP06-6A. Also, the gyrogonites of two well-known species of Charophyta, Chara filiformis Hertzsch and Chara vulgaris Linnaeus, are occasionally present in the sediment from Laguna de los Pozuelos. The results provide a new vehicle for clarifying the Quaternary palaeohydrological history of the Pozuelos Basin, which is a RAMSAR wetland that is likely to be sensitive to global environmental change.Fil: Palacios Fest, Manuel R.. Terra Nostra Earth Sciences Research,; Estados UnidosFil: Cusminsky, Gabriela Catalina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: McGlue, Michael M.. University of Kentucky; Estados Unido

Prehistoric agrosystems of central Arizona: a paleoenvironmental approach to the study of Hohokam irrigated fields and canals

Prehistoric agrosystems of central Arizona: a paleoenvironmental approach to the study of Hohokam irrigated fields and canal

Prehistoric agrosystems of central Arizona: a paleoenvironmental approach to the study of Hohokam irrigated fields and canals

Prehistoric agrosystems of central Arizona: a paleoenvironmental approach to the study of Hohokam irrigated fields and canal

Ostracode biofacies and shell chemistry reveal quaternary aquatic transitions in the Pozuelos basin (Argentina)

Here we present the first use of calcareous microfossils to examine the late Quaternary paleoecology of the endorheic Pozuelos Basin (Argentina). Modern deposition in the basin centers on Laguna de los Pozuelos (LP),a shallow playa-lake that is fed by axial rivers and groundwater and dominantly accumulates siliciclastic sediments.Today, the distribution of limnocytherid and cypridoidean ostracodes across southern LP is strongly influenced bydistance to the Rıo Cincel delta, whereas the northern end of the playa-lake is characterized by a paucity of ostracodes due to frequent sub-aerial exposure. Ten ostracode biofacies define a sediment core retrieved from LP,which reveal progressive changes in aquatic environments that varied in salinity, depth, and proximity to deltas over the late Pleistocene. Closed lakes occupied the basin from ~ 37.6?30.7 ka, ~ 28.0?25.0 ka, and ~ 23.0?16.6 ka,whereas saline wetlands occurred when these lakes contracted. Extant LP has no analog in the late Pleistocene record; it formed after ~ 7.2 ka, following a hiatus that removed the Pleistocene?Holocene transition.Paleoecological evidence indicates that the core site was influenced by deltaic inflows from the eastern basin margin until ~ 24.3 ka, an area where today dry alluvial fans are found. Reorganization of the watershed by normalfaulting, most likely at ~ 18.0 ka, appears to have reduced the influence of these deltaic inflows. Extensional neotectonics, perhaps induced by incorporation of the Pozuelos Basin into the Andean hinterland, is a mechanism that along with tropical climate change is potentially important to water balance and ecology in high-altitude convergent orogenic basins.Fil: McGlue, Michael M.. University of Kentucky; Estados UnidosFil: Palacios Fest, Manuel R.. Terra Nostra Earth Sciences Research; Estados UnidosFil: Cusminsky, Gabriela Catalina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Camacho, Maria. Universidad Nacional de Jujuy; ArgentinaFil: Ivory, Sarah J.. University of Kentucky; Estados Unidos. University Brown; Estados UnidosFil: Kowler, Andrew L.. University of California; Estados UnidosFil: Chakraborty, Suvankar. University of Utah; Estados Unido