Glacial Morphology of Los Pelados-El Nevero Massif (Sierra de Guadarrama National Park). A new interpretation and chronology

El presente trabajo se localiza en el Macizo de Los Pelados-El Nevero y tiene como objetivos el inventario, cartografía, cronología e interpretación de la secuencia evolutiva de sus paleoglaciares. La altura media de este macizo es de 2100 m (Pico del Nevero, 2209 m) y su litología (orto, para y leuco-gneises) y ambiente climático (mediterráneo de montaña continentalizado) son los propios del Guadarrama Central. En el contexto fisiográfico, este macizo destaca por su trazado casi E-W frente a la dirección general NE-SW del conjunto de los Montes Carpetanos y por su morfoestructura de bloque disimétrico basculado (laderas meridionales escarpadas-laderas septentrionales tendidas). Esa dismetría, junto a los escalones oriental y occidental debidos a sistemas de fallas de tendencia N-S (los de los puertos de Navafría y Malagosto), dieron origen a una pequeña meseta topográfica en la planicie de cumbres que posibilitó el desarrollo de un glaciarismo distintivo en estas áreas, caracterizados por: una tendencia centrífuga de las lenguas glaciares a partir de las cimas; una relativa abundancia de glaciares con localización septentrional y la presencia de un pequeño glaciar de meseta. Los datos obtenidos mediante datación absoluta 10Be-TCN en el paleoglaciar de Hoyo Grande, muestran que la MIE local (~26 ka BP; MIS2) ocurrió sincrónicamente con el LGM.The studies on glacial geomorphology of the Sierra de Guadarrama have been focused mainly on the Peñalara Massif and, in general, the cartographies provided have little detail and in many cases are imprecise. In fact, in this mountain range there are areas with paleoglaciares that were described for the first time in the second half of the last century and the cartographies are only schematic. One of these areas is Los Pelados-El Nevero Massif, which is where this work is located. The main objectives are the inventorying, describing and mapping in detail its glacial morphology and establishing the absolute chronology of some evolutionary reference stages. Los Pelados-El Nevero Massif has an average height of 2100 m asl and its culmination is the peak of Nevero (2209 m). Its lithology (ortho, para and leuco-gneises) and climatic environment (Continentalized Mediterranean mountain climate) are the generals corresponding to central Guadarrama sector (Fig. 1). However, its morphology has some distinctive features such as its E-W tendency versus the NW-SW general direction of the whole of the Montes Carpetanos range, or the dissymmetric morphostructure of its mountain-block (tilted block: steep southern-face and gentle northern-slopes). This dissymmetry, together with the eastern and western steps due to N-S trend faults systems (those of the Navafría and Malagosto ports), gave rise to a small plateau type summit surface that enabled the development of a distinctive glaciarism in this massif (Fig. 2, Fig. 3). In the other massifs of the Sierra de Guadarrama (Peñalara, Cabezas de Hierro) the glaciers were developed on double slope (southeast-northwestern; northern-southern) predominating those of southern location. However, in the case of the Los Pelados-El Nevero Massif the glaciers had a centrifugal tendency from the topographic plateau with orientations to all the slopes although in one, the western one, were little significant. In addition, distinctive features of the glaciarism of this massif are, as much the relative abundance of glaciers in northern slopes as the existence of a small plateau-type glacier. All this configures a massif with remarkable development of the glaciers (Fig. 3, Table I). The maximum length reached by a glacier in this area was 2294 m and the lower topographic elevation reached by the ice during its maximum extension (local MIE) was 1560 m asl, parameters that corresponds to the paleoglacier of Porrinoso-Peñacabra. With the data available so far, obtained by means of 10Be-TCN absolute dating in the paleoglacier of Hoyo Grande (Table II), the local MIE is synchronous with the LGM (~26 ka Bp; MIS2). This age is in agreement with the chronology obtained for the MIE of the Peñalara paleoglacier (18 km to the SW), but it is in disagreement with chronology obtained for the MIE of the La Mujer Muerta paleoglacier (30 km to the SW), given that it is attributed an age corresponding to the MIS3 and, therefore, prior to the LGM.Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEMinisterio de Economía y Competitividad (MINECO)Organismo Autónomo de Parques Nacionalespu

Reconstruction and chronology of the Sierra de Béjar plateau glacier (Spanish Central System) during the glacial maximum

Durante el Último Ciclo Glaciar (Pleistoceno Superior) en la Sierra de Béjar se desarrolló un glaciarismo de meseta que presentaba dos tipologías: campo de hielo (plateau icefield) y domo de hielo (plateau icecap). El primero ocupó el sector sur y se trataba de un sistema de glaciares de valle coalescentes en cabecera. El segundo ocupaba el sector norte de esta sierra, se trataba de una masa de hielo con fisonomía cupuliforme y no confinada por la topografía. El estudio detallado de la morfología glaciar actual de la Sierra de Béjar, ha permitido obtener excelentes indicadores para la reconstrucción de las masas de hielo en el máximo glaciar (MG) y calcular así diferentes parámetros morfológicos, dinámicos y cronológicos útiles en las interpretaciones paleoclimáticas y evolutivas. Con los datos obtenidos se ha establece que el borde de la meseta glaciar (plateau glacier) a partir del cual irradiaban las lenguas, se localizó alrededor de los 2100 m de cota absoluta. Su extensión total era de 57,40 km2 y el espesor máximo estimado fue entre 80 y 130 m. Durante el periodo de máxima extensión (MG), el conjunto de la meseta tenía una morfología próxima al icecap, al iniciarse los primeros retrocesos la masa de hielo quedó reducida pasando a funcionar como un verdadero icefield y, finalmente, como simples glaciares de valle o residuales de circo. Los primeros datos obtenidos de los trabajos que se están realizando para determinar la cronología precisa del máximo glaciar (MG) mediante 10Be y que pertenecen a muestras de los valles de Duque-Trampal, Endrinal, y Cuerpo de Hombre, establece una edad entre 27,2 ± 2,7 y 26,2 ± 0,8 ka BP para la etapa de máximo desarrollo de las mesetas de hielo correspondientes al máximo glaciar (MG) en estas áreas.During the last glaciation (Late Pleistocene) Sierra de Béjar hosted a plateau glacier with two morphologies: a plateau icefield and a Plateau icecap. The former developed in the southern sector and was formed by a set of valley glaciers coalescent in the upper sectors. The later occupied the northern sector of the range, being a non-confined dome-shaped ice mass, which was favoured by the plateau morphology of the bedrock. The detailed study of the glacier morphology in Sierra de Béjar has conducted to identify reliable indicators to reconstruct the ice masses during the Glacial Maximum (MG). These indicators were used to calculate different morphologic, dynamic and chronologic paramenters, very useful in unravelling the glacier evolution and to extract paleoclimate interpretations. Based on the new data, the edges of the plateau glacier were established around 2100 m above sea level, its extension was of 57.4 km2 and the maximum thickness ranges from 80 and 130 m along the summits of the range. During the period of maximum extension of the glacier (MG) the plateau had a morphology close to an icecap, whereas with the onset of glacier retreat the ice mass reduced and the glacier become a truly icefield. Finally, during successive stages of retreat the glaciers were individualized and become valley and cirque glaciers. The on-going research regarding the chronology of the glacier maximum (MG) based on 10Be dates, that consider samples from Duque-Trampal, Endrinal and Cuerpo de Hombre glaciers from Sierra de Béjar, provides preliminary dates of 27.2 ± 2.7 and 26.2 ± 0.8 ka BP for the maximum extent of the plateau glacier in this area.Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEEspaña. Ministerio de Ciencia e InnovaciónCastilla-La Mancha. Junta de Comunidades. Consejería de Educaciónpu

An actionable anti-racism plan for geoscience organizations.

Geoscience organizations shape the discipline. They influence attitudes and expectations, set standards, and provide benefits to their members. Today, racism and discrimination limit the participation of, and promote hostility towards, members of minoritized groups within these critical geoscience spaces. This is particularly harmful for Black, Indigenous, and other people of color in geoscience and is further exacerbated along other axes of marginalization, including disability status and gender identity. Here we present a twenty-point anti-racism plan that organizations can implement to build an inclusive, equitable and accessible geoscience community. Enacting it will combat racism, discrimination, and the harassment of all members

Earth is (mostly) flat: apportionment of the flux of continental sediment over millennial time scales

We use a new compilation of global denudation estimates from cosmogenic nuclides to calculate the apportionment and the sum of all sediment produced on Earth by extrapolation of a statistically significant correlation between denudation rates and basin slopes to watersheds without denudation rate data. This robust relationship can explain approximately half of the variance in denudation from quartz-bearing topography drained by rivers using only mean slopes as the predictive tool and matches a similar fit for large river basins. At slopes \u3e200 m/km, topography controls denudation rates. Controls on denudation in landscapes where average slopes are 10 mm/k.y. We use global topographic data to show that the vast majority of the Earth’s surface consists of these gently sloping surfaces with modest, but positive, gross denudation rates, and that these areas contribute the most sediment to the oceans. Because of the links between silicate weathering rates and denudation rates, the predominance of low sloping areas on the Earth’s surface compared to areas of steep mountainous topography implies that mountain uplift contributes little to drawdown of CO2 at cosmogenic nuclide time scales of 103–106 yr. The poorly understood environmental controls that set the pace of denudation for the largest portion of Earth’s surface hold the key to understanding the feedbacks between erosion and climate

The effect of pH, organic ligand chemistry and mineralogy on the sorption of beryllium over timeL

Environmental contextBeryllium is a toxic environmental contaminant but has many industrial and scientific applications. Our work explores the effects of soil composition on beryllium retention, focussing on organic matter, mineralogy and pH and concludes that phosphorus and sulfur oxides in addition to soil acidity are strong controls on beryllium mobility. These results aid in future predictions regarding the fate of beryllium in the environment. AbstractUnderstanding the chemical controls on beryllium sorption is fundamental when assessing its mobility as a pollutant and interpreting its concentration as a geochemical tracer of erosion, weathering and landscape surface stability. In order to evaluate the interactions of beryllium with soil- and aquatic-related materials, we selected model organic compounds and minerals to perform sorption experiments. The retention of beryllium by each of these compounds and minerals was evaluated over a pH range of 3–6 and at various equilibration times to determine which conditions allowed the greatest retention of beryllium. We conclude that most beryllium sorption occurred within 24h for both organic and mineral materials. However, equilibration required longer periods of time and was dependent on the solution pH and sorbent material. The pH exhibited a strong control on beryllium sorption with distribution coefficient (Kd) values increasing non-linearly with increasing pH. A system with a pH of 6 is likely to retain 79–2270% more beryllium than the same system at a pH of 4. Phosphonate retained the greatest amount of beryllium, with Kd values 2–30× greater than all other materials tested at a pH of 6. Therefore, soils containing larger amounts of phosphorus-bearing minerals could result in greater retention of beryllium relative to phosphorus-limited soils. Overall, soil composition, with an emphasis on phosphorus oxide content and pH, is an important property to consider when evaluating the capacity of a system to retain beryllium

The effect of pH, organic ligand chemistry and mineralogy on the sorption of beryllium over timeL

Environmental contextBeryllium is a toxic environmental contaminant but has many industrial and scientific applications. Our work explores the effects of soil composition on beryllium retention, focussing on organic matter, mineralogy and pH and concludes that phosphorus and sulfur oxides in addition to soil acidity are strong controls on beryllium mobility. These results aid in future predictions regarding the fate of beryllium in the environment. AbstractUnderstanding the chemical controls on beryllium sorption is fundamental when assessing its mobility as a pollutant and interpreting its concentration as a geochemical tracer of erosion, weathering and landscape surface stability. In order to evaluate the interactions of beryllium with soil- and aquatic-related materials, we selected model organic compounds and minerals to perform sorption experiments. The retention of beryllium by each of these compounds and minerals was evaluated over a pH range of 3–6 and at various equilibration times to determine which conditions allowed the greatest retention of beryllium. We conclude that most beryllium sorption occurred within 24h for both organic and mineral materials. However, equilibration required longer periods of time and was dependent on the solution pH and sorbent material. The pH exhibited a strong control on beryllium sorption with distribution coefficient (Kd) values increasing non-linearly with increasing pH. A system with a pH of 6 is likely to retain 79–2270% more beryllium than the same system at a pH of 4. Phosphonate retained the greatest amount of beryllium, with Kd values 2–30× greater than all other materials tested at a pH of 6. Therefore, soils containing larger amounts of phosphorus-bearing minerals could result in greater retention of beryllium relative to phosphorus-limited soils. Overall, soil composition, with an emphasis on phosphorus oxide content and pH, is an important property to consider when evaluating the capacity of a system to retain beryllium