The Development Of Fan Delta In The System Lake Pueyrredón-Posadas And Its Correlation With Allocyclic Controls Postglacial Pleistocene-Holocene In The Patagonian Andes, Argentina

A los pies de los Andes en la Patagonia Argentina, se formaron una serie de lagos oligotróficos producto de la deglaciación pleistocena tardía – holocena temprana. El Sistema Lacustre Pueyrredón–Posadas (SLP-P) en Argentina pertenece a este grupo de lagos postglaciales. En la costa sur del SLP-P se desarrollaron cuatro abanicos deltaicos (fan deltas); el de mayor desarrollo areal se encuentra hacia el Este en la desembocadura del río Furioso, mientras que los tres restantes disminuyen de tamaño hacia el Oeste. El abanico deltaico del río Furioso está conectado con depósitos de una morrena firontal, entre ambos producen la separación de los lagos Pueyrredón y Posadas. Los abanicos deltaicos de los ríos Oro y Suyai han desarrollado barras litorales paralelas a la costa producto del oleaje relacionado a los intensos vientos del Oeste. Los ápices de los abanicos deltaicos se encuentran correlacionados con niveles lacustres datados en la costa norte del SLP-P. En los abanicos deltaicos se identificaron dos niveles aterrazados, a 300 msnm y a 400 msnm. Los diferentes pulsos en la caída del nivel de base del SLP-P permitieron el desarrollo sistemático de los abanicos deltaicos, tanto en sentido areal de la geoforma (en relación directa con el tamaño de la cuenca de drenaje) como altitudinal del ápice, con una disminución constante de ambos parámetros en el sentido este – oeste. Las variaciones batimétricas ocurridas en este sistema fueron corroboradas con la integración de un modelo digital de elevación y control de campo. De esta manera, el desarrollo de los abanicos deltaicos en el SLP-P habría estado controlado, principalmente, por factores alocíclicos: clima y descenso del nivel de base.At the foot of the Andes in Patagonia argentine, a series of oligotrophic lakes were formed by deglaciation during Late Pleistocene – Early Holocene. The Pueyrredón-Posadas Lacustrine System (P-PLS) in Argentina belongs to this group of postglacial lakes. In the southern coast of the P-PLS four fan-deltas were developed; the largest development in this area is located in the mouth of Furioso River Eastward, whereas the others three decrease in size westward. The Furioso River fan-delta is connected with deposits of a firontal moraine; both together produce the separation of Pueyrredón and Posadas Lakes. The Oro and Suyai fan-deltas have developed barriers parallel to the coast by wave actions related to intense winds firom West. The apexes of these fan-deltas are correlated with datings in lacustrine levels at the North coast of the P-PLS. At both sides of fan-deltas, two terraces were identifed, at 300 masl and 400 masl. The timing in the base level fall of P-PLS allowed this particular systematic development of fan-deltas, as in geoform sizes (directly related to size of drainage basin) as altitudes of these apexes, with a methodical diminution of both parameters in the East-West sense. The bathymetric variations in P-PLS were corroborated with the integration of a digital elevation model and feld work. Thus, the development of these fan-deltas in the P-PLS could be, mainly, controlled by allocyclic factors: climate and base level.Fil: Horta, Luis Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Instituto Superior de Estudios Sociales. Universidad Nacional de Tucuman. Instituto Superior de Estudios Sociales; ArgentinaFil: Georgieff, Sergio Miguel. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Busnelli, Jose. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Aschero, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Instituto Superior de Estudios Sociales. Universidad Nacional de Tucuman. Instituto Superior de Estudios Sociales; Argentin

Temporal dynamics of soil erosion and rainfall erosivity as geoindicators of land degradation in Northwestern Argentina

The subtropical region of Northwestern Argentina displays severe environmental deterioration due to a combination of factors, including seasonally contrasting weather, highly erodable loessic soils, a topography with varied slopes, and natural vegetation coverage restricted by deforestation and agricultural advance, in addition to exploitation of natural resources by people. The aim of the present research was to determine the landscape degradation, using as geoindicators the increase in erosion by water and the pluviometric gradient variations through time. Two regions were chosen as sample areas in the province of Tucumán: the eastern foothills and plain of the Southeastern Ranges (Western Chaco); and the intermountain valley of Tafi . Erosion increase was quantified by measuring the length of gullies and ravines; and the sedimentation in the artificial lake (La Angostura) located in the center of the valley of Tafi . Climate changes were analyzed by means of the rainfall erosivity variations in both sample areas during the last 30 years. The lineal increase in erosion is closely related to the pluvial dynamics. Nevertheless, this erosive intensification is also dependent on the interaction of environmental factors and human activities (deforestation, land use changes, unrestricted agriculture).Fil: Busnelli, Jose. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Geociencias y Medio Ambiente; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; ArgentinaFil: Neder, Liliana del Valle. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Geociencias y Medio Ambiente; ArgentinaFil: Sayago, Jose Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto Miguel Lillo; Argentin

Increase of erosion and land degradation for anthropogenic actions and climatic variations, Tucumán

Los procesos erosivos son aquellos que reflejan cambios ambientales, eventos climáticos extremos como grandes tormentas, desaparición de la vegetación de forma natural o antrópica y otra causa que genere discontinuidad en el modelado del paisaje. La explotación agrícola irrestricta a expensas del desmonte masivo durante décadas húmedas, ocasionó la degradación de los suelos por aceleración de procesos erosivos debidos a la acción hídrica y pérdida de nutrientes. El cultivo permanente produjo pérdida de la productividad edáfica aún cuando se implementó la siembra directa como un sistema de manejo sustentable en los últimos años. Los objetivos de este trabajo fueron evaluar y caracterizar los procesos erosivos, avance agrícola y variaciones pluviométricas en la llanura ondulada del departamento Burruyacú al noreste de la provincia de Tucumán. Los procesos erosivos generados por acción hídrica y remoción en masa, son: la erosión mantiforme en los interfluvios convexos y las cárcavas y barrancos por retroceso de cabeceras y paredes laterales en las áreas deprimidas longitudinales. Estas formas de erosión se ven favorecidas por las características limo loéssicas de los suelos, de alta erodabilidad en condiciones húmedas. El análisis pluviométrico evidencia dos incrementos del volumen de precipitaciones: en 1950 y 1970 con tendencia al aumento en los años subsiguientes. A partir de 1970 se inicia el desmonte, eliminando el monte chaqueño durante tres décadas e implementando la agricultura. La cartografía morfodinámica se efectuó con fotografías aéreas (1985 y 2001) y se digitalizó con ILWIS.Erosive processes reflect environmental changes and extreme climatic events as intense storms. Natural vegetation coverage clearance, carried out by anthropic actions, generates discontinuities in landscape modeling. Unrestricted agricultural exploitation through massive deforestation during humid decades, has promoted soils degradation through erosive processes and nutrients losses decreasing topsoil productivity even though the implementation of direct sow in the last few years. The aims of this research were to analysis erosive processes, agricultural advances, and pluviometric variations at the northeast of Tucumán province. As geoindicators of erosive process acceleration on crop areas are: sheet runoff and erosion in convex surface, headwater erosion and b anthropogenic bankfull lateral walls in gullies and ravines. These erosive landforms are favored by silt loessic contents from high erodability soils in humid conditions. Erosive process cartography was done using aerial photographs of 1985 and 2001, and then, all data were digitalized using ILWIS (Integrated Land and Water Information System).Fil: Neder, Liliana del Valle. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Geociencias y Medio Ambiente; ArgentinaFil: Busnelli, Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Geociencias y Medio Ambiente; ArgentinaFil: Sampietro Vattuone, Maria Marta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Geociencias y Medio Ambiente; Argentin

Análisis de facies y evolución paleogeográfica del sistema lacustre Pueyrredón-Posadas-Salitroso durante los últimos 25 ka

Se presenta el análisis de facies y la reconstrucción paleogeográfica pertenecientes al sistema lacustre Pueyrredón – Posadas – Salitroso (SL-PPS), el cual se encuentra ubicado al NO de la Provincia de Santa Cruz, Argentina, centrado en los 47° 22' 28" S - 71° 55' 34" O (Fig. 1). Depósitos areno-limo-arcillosos con materia orgánica de los alrededores del SL-PPS fueron datados como pleistocenos y holocenos (entre 25ka y 5ka AP). El análisis de facies indica ambientes costeros (deltas y fan-deltas), glacilacustre somero y profundo controlados por los cambios climáticos de escala global que también fueran registrados para otras regiones de la Patagonia Andina Argentina y Chilena (Sugden et al, 2005; Kaplan et al, 2008; Ariztegui et al., 2009; Harrison et al., 2012; Horta et al,. 2013). Estos ambientes sedimentarios fueron descritos y datados mediante 14C en varios perfiles estratigráficos permitiendo la reconstrucción de la evolución del SL-PPS durante los últimos 25ka. Por otro lado, se integraron los perfiles estratigráficos a la geografía actual y pasada teniendo en cuenta las características topográficas determinadas por modelos de elevación digital (DEM) extraídos del SRTM (Shuttle Radar Topography Mission). El análisis de facies sedimentarias muestra la influencia de las masas de hielo en la evolución paleoambienteal con la alternancia de ambientes glaciales y proglaciales: tillitas, glacilacustres/lacustres, glacifuviales/fluviales, abanicos de lavado/abanicos aluviales y cuerpos deltaicos. Se mapearon y reconstruyeron varios niveles de paleocostas. El más antiguo de estos niveles se estima a aproximadamente 450 msnm (Fig. 2 a), 300 m por encima del nivel actual de los Lagos Pueyrredón y Posadas, y con una edad de 23.580 años AP. Un nivel datado con un rango de edad que varía entre 21.000 – 14.180 AP se habría generado con la evolución del sistema lacustre desde los 450 msnm hasta los 360 msnm (Fig. 2 b). Un nivel intermedio (Fig. 2 c), bien identificado y delimitado, corresponde al encontrado 150 m por encima del nivel de los lagos actuales (300-315 msnm) abarcando un rango de edades entre 14.180 AP y 6.903 años AP. El nivel más bajo identificado (Fig. 2 d) y delimitado corresponde al encontrado 50 m por encima del nivel de los lagos actuales, en el cual se dataron conchillas de gasterópodos de la Familia Succineidae. Beck 1837, género Succinea, en 5.208±38 años AP. Las variaciones paleogeográficas obtenidas evidencian los cambios climáticos ocurridos durante el Pleistoceno tardío – Holoceno temprano, procesos alocíclicos que quedaron registrados en diferentes lagos patagónico como en el caso del Lago General Carrera (Bell 2008), paleolago Caldenius (Aschero et al. 1998, Dell Valle et al. 2007), Paleolago Teulche (Solari et al. 2012), o el caso del Lago Cardiel (Stine y Stine 1990, Gilli et al. 2001, Araztegui et al., 2009).Fil: Horta, Luis Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Estudios Sociales. Universidad Nacional de Tucumán. Instituto Superior de Estudios Sociales; Argentina. Universidad Nacional de La Rioja; ArgentinaFil: Georgieff, Sergio Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto Miguel Lillo; ArgentinaFil: Busnelli, Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Geociencias y Medio Ambiente; ArgentinaFil: Aschero, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Estudios Sociales. Universidad Nacional de Tucumán. Instituto Superior de Estudios Sociales; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto Miguel Lillo; ArgentinaXIX Congreso Geológico ArgentinoCordobaArgentinaAsociación Geológica Argentin

Landform analysis of the Pueyrredón Lake area in northwestern Santa Cruz, Argentina

The aim of this research was to analyze the landforms around Pueyrredón Lake (NW Santa Cruz in Argentina) to contribute to the understanding of the paleoenvironmental evolution of Patagonia during the Late Pleistocene–Early Holocene. The Pueyrredón Lake area belongs to the Patagonian shield, northwest of the Santa Cruz Province (47°22′28″ S–71°55′34″ W). Characteristic landforms were identified through satellite images (Landsat 7 ETM) and field work. These landforms include glacial troughs, glacier striations and groove casts, three fan deltas on the south margin of Pueyrredón Lake, lacustrine and glacio-lacustrine sediment, and till deposits. In addition, short detailed stratigraphic logs were measured for paleoenvironmental analysis, and several sedimentary deposits were sampled to characterize grain size variations. All of the information is displayed on a geomorphological map. The modern and ancient landforms were also analyzed based on their topographic characteristics, which were determined by a digital elevation model (DEM). Geomorphological conditions of the erosional and depositional processes in the paleoglacial environment were analyzed using longitudinal- and cross-sections. The results shed light on the climatic variability during the most recent geological period. Major changes in the landscape morphology were associated with glacier evolution and the development and division of the great lakes in the eastern Andes, in Central Patagonia.Fil: Horta, Luis Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Instituto Superior de Estudios Sociales. Universidad Nacional de Tucuman. Instituto Superior de Estudios Sociales; Argentina. Universidad Nacional de la Rioja; ArgentinaFil: Busnelli, Jose. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Georgieff, Sergio Miguel. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Aschero, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Instituto Superior de Estudios Sociales. Universidad Nacional de Tucuman. Instituto Superior de Estudios Sociales; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; Argentin

Effects of pre-operative isolation on postoperative pulmonary complications after elective surgery: an international prospective cohort study an international prospective cohort study

We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care. We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care