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Abstract: Several glaciers developed in the Cantabrian Mountains (NW Spain) during the last glacial maximum (LGM). In the last 15years, several studies of glacial geomorphology have increased the knowledge about the limits of the glaciation, but little data are available about many valleys, especially on the northern slope, due to extensive postglacial erosion. In this study, we apply the AABR method to reconstruct palaeo-equilibrium-line altitudes (ELAs) in eleven palaeo-glaciers that are considered to be representative of the different areas of the range. To reduce the ambiguity in the palaeo-ELA values caused by local factors, we analysed medium and large glaciers (4.7 to 65.5km2) except for the Sil complex glacier, which was the largest glacier in northwestern Spain (445km2). The palaeo-ELAs during the local LGM ranged between 1000 and 2000m and had a similar pattern to the present-day winter precipitation and summer temperatures. [Copyright &y& Elsevier]

During the Late Pleistocene, the main mountain ranges of the Iberian Peninsula were covered by small icefields and cirque and alpine glaciers. The deglaciation triggered paraglacial processes that generated landforms, mostly within the ice-free glacial cirques. In this research we analyse the deglaciation process in the Muxivén Cirque (42°15′N – 6°16′W), in the upper Sil River Basin, which includes some of the largest relict rock glaciers of the Cantabrian Mountains. We addressed this objective by means of accurate geomorphological reconstructions, sedimentological analysis, Schmidt-hammer surface weathering measurements and a dataset of 10 10Be Cosmic-Ray Exposure ages. Results reveal that after ~16 ka, glaciers retreated to the bottom of the cirques at the headwaters of the valley, leaving the walls free of ice and triggering rock avalanches onto the remnants of these glaciers. This paraglacial process supplied debris to a small glacier within Muxivén Cirque, which transformed in two rock glaciers. These debris isolated the ice inside the rock glaciers only for a very short period of time and ended up melting completely before the Younger Dryas. The lower sector of the largest one stabilized at 14.5 ± 1.5 ka, while the upper sector remained active until 13.5 ± 0.8 ka. Previous to the stabilization of the lower sector of the northern rock glacier, at its margin a high-energy debris avalanche occurred at ~14.0 ± 0.9 ka. These data agree with previous research, corroborating the paraglacial origin of most Iberian rock glaciers during the Bølling-Allerød interstadial. [Display omitted] • Glacier retreat triggered rock avalanches that favoured rock glacier formation. • Rock glacier activity lasted for a short time, collapsing before the Younger Dryas. • Rock glaciers stabilized at 14.5 ± 1.5 ka and 13.5 ± 0.8 ka (lower and upper sectors). • A high-energy debris avalanche occurred at ~14.0 ± 0.9 ka at the rock glacier margin. • A good example of the paraglacial origin of many Iberian rock glaciers [ABSTRACT FROM AUTHOR]

Abstract Deglaciated mountainous areas are usually affected by a great range of paraglacial processes that involve progressively denudation of glacial imprints. This study focuses on paraglacial processes and glacial landform preservation in six zones located in two catchments of the Cantabrian Mountains (NW Spain). These zones are adjacent but display important topographic, lithologic and glaciation style differences. An analysis of how these variables conditioned the intensity and diversity of paraglacial processes in these zones was investigated through a detailed study of their relief, lithology and paleo glacier surface using GIS. A comprehensive cartography of paraglacial landforms was also accomplished, considering landslides, alluvial fans and rock glaciers that show signs of having been conditioned by glaciation. Moraines and debris-mantled slopes were also included in the analysis to examine their grade of preservation depending on the studied variables. Data comparison show that differences in glaciation style influenced paraglacial processes. In the ancient icefield area, relief modification by glacial action was limited and scarce paraglacial processes occur. By contrast, in the upper areas located in the southern ranges where an alpine-style of glaciation was installed, paraglacial processes were very active, generating many rock glaciers. Lithology explains some paraglacial landforms distribution: 1) Landslides are associated with incohesive (sandy and shale) rocks; 2) Rock glaciers mainly occur in quartzite areas; 3) In limestone areas subterranean drainage contributes to glacial landscape preservation, but suffosion dolines affect some glacial deposits. Topography is also a key factor in paraglacial processes: 1) Moraines are well-preserved in gently sloping valleys, but rare in the steeper where they are usually transformed into moraine (or debris)-mantled slopes; 2) Alluvial fans are more frequent in the steeper valleys, but more dissected by postglacial river action. 3) Elevation and orientation show little influence on paraglacial landforms, except in the generation of some periglacial features such as rock glaciers. [ABSTRACT FROM AUTHOR]

Landforms resulting from the interaction between paleo-glaciers and karst are studied by using the Sierra de los Grajos (Cantabrian Mountains) as a model. This area contains glacial landforms that have not interested geomorphologists due to their low altitude (Peña Castillo is about 1857 m a.s.l.), the absence of glacial cirques and the scarcity of large moraines. However, the prevalence of groundwater flow and chemical dissolution has favoured the preservation of glacial landforms. Lateral and frontal moraines show three main glacial stages and other minor glacier stabilization phases, with the paleo-ELA oscillating between 1650 and 1760 m. Moraines are combined with depressions and sinks resulting from subglacial karstic drainage. This convergence of forms and processes is an exception in the Cantabrian Mountains, where postglacial erosion has usually eroded the frontal moraines and the proglacial sediments. In the case of the Sierra de los Grajos, despite the underground drainage and preservation of many glacial deposits on karstic landforms, an outwash-plain was formed. These proglacial sediments and others from non-karstified areas filled the depressions of the preglacial terrain located at their edges. The main glaciokarstic landforms have been mapped and a sedimentological analysis of the outwash plain was made in order to reconstruct the glacial dynamics of this area. [ABSTRACT FROM AUTHOR]

A total of 156 glacial cirques located on two different areas in the Cantabrian Mountains (NW Spain) were identified and measured in order to continue and expand the study of these large-scale erosional forms in European mountains. Environmental variables that may explain cirque distribution (altitude, aspect and lithology), and their most important morphometric features (area, length (L), width (W), headwall height (H), and L/W, L/H and W/H indices), are analysed. Statistical analysis has been applied as indicators of contrast (ANOVA) and association (correlation and regression). Conglomerate analysis (CLUSTER) has been used to discriminate cirque groups based on their morphometric variables. Results show that cirques occur at lower altitudes in the Upper Sil River basin area than in the Montaña Central area due to a lower former equilibrium line altitude (ELA) position. In the Upper Sil River basin, environmental variables appear to have had a strong influence on the location and size of cirques: the largest cirques are located in quartzite rocks at elevations above 2000 m and face N or NE. In Montaña Central, the influence of these factors was more limited as a consequence of higher geological structure control. Cirque sizes generally are modest compared with cirques present in other mountain ranges globally, most likely due to shorter glacial occupancy in the Cantabrian Mountains. [ABSTRACT FROM AUTHOR]