<p>In the Antarctic Peninsula (AP), the small ice caps distributed across its periphery and... more <p>In the Antarctic Peninsula (AP), the small ice caps distributed across its periphery and surrounding islands have recorded important ice volume changes since the end of the Last Glacial Cycle. These volume changes have occurred in the form of surface extent shrinking and ice thinning. The latter has been investigated only at a reduced number of locations. In this context, nunataks constitute key spots to assess the environmental evolution of deglaciated areas as they offer the opportunity to track the deglaciation history and reconstruct past ice losses by using Cosmic-Ray Exposure (CRE) dating. Indeed, nunataks are supposed to have played a prominent role in the vegetal and animal colonization of Antarctica.</p><p>The South Shetland Islands archipelago is one of the AP areas where past ice thinning has been least investigated, with only one study conducted in King George Island. In order to shed some light on the last deglaciation and its associated ice thinning, we apply <sup>10</sup>Be CRE dating to vertical sequences of glacially polished outcrops on two palaeonunataks and one nunatak distributed across the ice-cap covering part of the Hurd Peninsula (SW of Livingston Island): Reina Sof&#237;a Peak (62&#176;40'8" S, 60&#176;22'51" W, 273 m a.s.l.), Moores Peak (62&#176;41'21" S, 60&#176;20'42" W, 407 m a.s.l.) and Napier Peak (62&#176;40'18"S, 60&#176;19'31" W, 382 m a.s.l.).</p><p>Most of the resulting exposure ages provided a logical chronological sequence and allowed reconstructing past vertical changes of the ice surface. The uppermost surfaces of the Moores and Reina Sof&#237;a peaks became deglaciated during the Last Glacial Maximum (LGM), between ~24 ka and ~20 ka. Following the LGM, between ~20 and ~14 ka (Termination-1), a massive deglaciation occurred. This trend was especially exacerbated at around ~14 ka, triggering the onset of the deglaciation at other nunataks, such as the Napier Peak, in good agreement with the coetaneous global melt-water pulse 1a. From our results, we infer that ice shrinking during the Holocene must have been very limited compared to the post-LGM period.</p><p>Nevertheless, some of the exposure ages were either anomalously old or inconsistent, such as those found at the summits of the Reina Sof&#237;a and Moores peaks or at the base of the Napier nunatak. These artifacts suggest the occurrence of nuclide inheritance and are indicative of the conservation of previously exposed surfaces. These ages allow to qualitatively infer cold-based regimes characterized by basal ice frozen to bed, with slow mobility and inefficient subglacial erosion due to the gentle slope gradient, not capable of removing inherited nuclides accumulated during former exposure periods. But, as a whole, the dataset adds valuable knowledge on the polythermal character of the Hurd Peninsula Ice cap.</p><p>&#160;</p><p>This paper was supported by the project NUNANTAR (02/SAICT/2017 &#8211; 32002; Funda&#231;&#227;o para a Ci&#234;ncia e a Tecnologia, Portugal) and the College on Polar and Extreme Environments (University of Lisbon).</p>
The Tröllaskagi peninsula is located in north central Iceland, between the meridians of 19o30’W a... more The Tröllaskagi peninsula is located in north central Iceland, between the meridians of 19o30’W and 18o10’W, limited by the Skagafjörður fiord to the west and the Eyjafjörður fiord to the east, jutting out into the North Atlantic to latitude 66o12’N and linked to the central Icelandic highlands to the south. There are over a hundred debris-covered and rock glaciers at its valley heads, some of which have been studied in detail regarding their dynamics and activity (vid. summary in Andrés et al. 2016). This work analyses block displacements and changes in the surface morphology of the Fremri-Grjótárdalur rock glacier (65◦43’N 19◦W, 1,245 m) and the Hóladalsjökull debris-covered glacier (65◦42’N; 18◦57’W, 1,330 m), located in the centre of Tröllaskagi peninsula. A Digital Photogrammetric WorkStation -Digi3d.NET(DPWS Digi3d) has been used in this study to compare the evolution of these landforms in aerial photographs taken at different years (1946, 1980, 1985 and 1994) and a 2000 ortho...
Scripta Nova-revista Electronica De Geografia Y Ciencias Sociales, 2008
El Corral del Veleta (Sierra Nevada. Espana) cobija en su seno y bajo manto detritico hielo glaci... more El Corral del Veleta (Sierra Nevada. Espana) cobija en su seno y bajo manto detritico hielo glaciar fosil y permafrost alpino, restos, como minimo, de la Pequena Edad del Hielo (siglos XV/XIX). En la actualidad, estas masas heladas se encuentran en proceso de degradacion. Los analisis y controles que desde 2001 se vienen llevando a cabo en un glaciar rocoso incipiente instalado en el tercio oriental del Corral del Veleta muestran procesos continuados de subsidencia de su manto detritico, apoyado sobre las masas heladas referidas. La merma del manto nival durante el verano, las aguas de fusion y el grado de penetracion de la onda de radiacion externa en el suelo, son parametros clave que explican este mecanismo de subsidencia, que podria estar relacionado con variaciones climaticas que vienen detectandose desde hace decadas.
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires
The aim of this study was to generate practical recommendations to assist rheumatologists and der... more The aim of this study was to generate practical recommendations to assist rheumatologists and dermatologists in the management of cardiovascular (CV) comorbidities in patients with moderate-to-severe psoriasis (MS-PSO) and psoriatic arthritis (PsA). A two-round Delphi study was conducted. A panel of experts rated their agreement with a set of statements (n = 52) on a nine-point Likert scale (1 = totally disagree; 9 = totally agree). Statements were classified as inappropriate (median 1-3), irrelevant (median 4-6) or appropriate (median 7-9). Consensus was established when at least two-thirds of the panel responded with a score within any one range. A total of 25 experts, 60% rheumatologists and 40% dermatologists, participated in two consultation rounds. There was overall unanimity on the appropriateness of an initial assessment for CV risk factors in all patients with MS-PSO and PsA. Most panelists (88.0%) also supported the evaluation of patients' psychological and physical status. Additionally, most panelists (72.2%) agreed on a novel sequential approach for the management of CV comorbidities. This sequence starts with the assessment of hypertension, diabetes and dyslipidemia along with the identification of depression and anxiety disorders. Once these factors are under control, smoking cessation programs might be initiated. Finally, if patients have not met weight loss goals with lifestyle modifications, they should receive specialized treatment for obesity. This study has drawn up a set of practical recommendations that will facilitate the management of CV comorbidities in patients with MS-PSO and PsA.
Through a detailed geomorphological study, including thourough mapping of the geomorphic features... more Through a detailed geomorphological study, including thourough mapping of the geomorphic features as well as 10 Be Cosmic-Ray Exposure (CRE) dating, the geomorphological evolution of the Mulhacén cirque since the maximum ice extent of the last glacial cycle until nowadays was determined. This glacial cirque is shaped on the northern face of the Mulhacén peak (3479 m a. .l., 37 03 12 N / 3 18 41 W), Sierra Nevada, southern Spain. It includes several depositional and erosional glacial landforms that allowed reconstructing its environmental evolution since the last glacial cycle. Furthermore, the sequence of glacial oscillations from this site was compared to that of other cirques of the massif, evidencing that: (i) new glaciers formed in these cirques during the Younger Dryas (YD), and (ii) disappeared at 11.7 ± 1.0 ka. Depending on the altitude, orientation and height of the cirque walls, the final deglaciation of the cirques generated a diversity of landscapes, including a wide range of glacial and periglacial landforms, such as polished surfaces, sequences of moraines, proto-rock glaciers or large rock glacier systems. No glaciers existed in the Sierra Nevada during the Middle Holocene. Only the cirques whose summits exceed 3300 m, are north-exposed and whose walls exceed 300 m high (i.e. Mulhacén and Veleta) hosted glaciers during Neoglacial phases, including the Little Ice Age (LIA) (approx. 1300-1850 CE). During these periods, climate oscillations favoured the formation of small glaciers in these cirques, which generated large moraine systems with either one polygenic ridge or a sequence of spaced frontal arcs. The existence of glaciers impeded the formation of permafrost-related Manuscript File Click here to vie linked References 2 landforms, such as rock glaciers and protalus lobes until the end of the LIA, when they started to form. These results are compared with the deglacial evolution in 55 cirques from Iberian mountains as well as from glacial cirques from other mid-latitude mountains and subpolar regions. The chronology of their deglaciation as well as the landforms generated during glacial retreat followed similar patterns, with no significant differences at regional scale. For each mountain range, the geomorphological diversity existing in each cirque depends on the local topographic characteristics although they formed during the same climatic phases.
<p>In the Antarctic Peninsula (AP), the small ice caps distributed across its periphery and... more <p>In the Antarctic Peninsula (AP), the small ice caps distributed across its periphery and surrounding islands have recorded important ice volume changes since the end of the Last Glacial Cycle. These volume changes have occurred in the form of surface extent shrinking and ice thinning. The latter has been investigated only at a reduced number of locations. In this context, nunataks constitute key spots to assess the environmental evolution of deglaciated areas as they offer the opportunity to track the deglaciation history and reconstruct past ice losses by using Cosmic-Ray Exposure (CRE) dating. Indeed, nunataks are supposed to have played a prominent role in the vegetal and animal colonization of Antarctica.</p><p>The South Shetland Islands archipelago is one of the AP areas where past ice thinning has been least investigated, with only one study conducted in King George Island. In order to shed some light on the last deglaciation and its associated ice thinning, we apply <sup>10</sup>Be CRE dating to vertical sequences of glacially polished outcrops on two palaeonunataks and one nunatak distributed across the ice-cap covering part of the Hurd Peninsula (SW of Livingston Island): Reina Sof&#237;a Peak (62&#176;40'8" S, 60&#176;22'51" W, 273 m a.s.l.), Moores Peak (62&#176;41'21" S, 60&#176;20'42" W, 407 m a.s.l.) and Napier Peak (62&#176;40'18"S, 60&#176;19'31" W, 382 m a.s.l.).</p><p>Most of the resulting exposure ages provided a logical chronological sequence and allowed reconstructing past vertical changes of the ice surface. The uppermost surfaces of the Moores and Reina Sof&#237;a peaks became deglaciated during the Last Glacial Maximum (LGM), between ~24 ka and ~20 ka. Following the LGM, between ~20 and ~14 ka (Termination-1), a massive deglaciation occurred. This trend was especially exacerbated at around ~14 ka, triggering the onset of the deglaciation at other nunataks, such as the Napier Peak, in good agreement with the coetaneous global melt-water pulse 1a. From our results, we infer that ice shrinking during the Holocene must have been very limited compared to the post-LGM period.</p><p>Nevertheless, some of the exposure ages were either anomalously old or inconsistent, such as those found at the summits of the Reina Sof&#237;a and Moores peaks or at the base of the Napier nunatak. These artifacts suggest the occurrence of nuclide inheritance and are indicative of the conservation of previously exposed surfaces. These ages allow to qualitatively infer cold-based regimes characterized by basal ice frozen to bed, with slow mobility and inefficient subglacial erosion due to the gentle slope gradient, not capable of removing inherited nuclides accumulated during former exposure periods. But, as a whole, the dataset adds valuable knowledge on the polythermal character of the Hurd Peninsula Ice cap.</p><p>&#160;</p><p>This paper was supported by the project NUNANTAR (02/SAICT/2017 &#8211; 32002; Funda&#231;&#227;o para a Ci&#234;ncia e a Tecnologia, Portugal) and the College on Polar and Extreme Environments (University of Lisbon).</p>
The timing of neoglacial advances in the Antarctic Peninsula (AP) is not yet well constrained. Ac... more The timing of neoglacial advances in the Antarctic Peninsula (AP) is not yet well constrained. Accurate temporal reconstruction of Neoglaciation in the AP is needed to better understand past glacial responses and regional and global teleconnections during the Holocene. Here, we examine all available information about neoglacial advances in the South Shetland Islands (SSI) as well as in the broader geographical context of the AP region and Antarctic continent. In order to shed light on the contrasting chronologies existing for neoglacial advances in these regions, we focused on a case study where a detailed picture of the Holocene deglaciation was already available. Lake sediments revealed that Byers Peninsula, west of Livingston Island (SSI), was fully deglaciated during the Holocene Thermal Maximum. To complement this approach, we identified glacially polished bedrock surfaces, erratic boulders and a moraine ridge near the present front of the glacier in the SE corner. We applied cosmogenic ray exposure (CRE) dating using in situ 36Cl for basalt rocks and 10Be for granitic rocks in: (i) 8 samples from glacial erratic and ice-rafted boulders, (ii) 2 samples from moraine boulders, (iii) 2 samples from polished bedrock surfaces, and (iv) 1 sample from an erratic boulder deposited on one of these surfaces. The CRE dates indicate that the onset of deglaciation started around 9.9 ± 1.2 ka, with two phases of glacier expansion during the Mid-Late Holocene forming moraines at~4.1 ± 0.5 and~1.0 ± 0.2 ka, respectively. The main neoglacial advances in the AP and the SSI were mostly synchronous and coincided with cold periods, as shown by other records (e.g. glacio-isostatic marine terraces, marine and lake sediments). In addition, these periods of glacial expansion show a similar timing to those recorded in the Arctic. These results suggest that Neoglaciation was driven by global climate forcing in both polar areas despite temporal variations at regional and local scale.
The Tröllaskagi peninsula is located in north central Iceland, between the meridians of 19o30’W a... more The Tröllaskagi peninsula is located in north central Iceland, between the meridians of 19o30’W and 18o10’W, limited by the Skagafjörður fiord to the west and the Eyjafjörður fiord to the east, jutting out into the North Atlantic to latitude 66o12’N and linked to the central Icelandic highlands to the south. There are over a hundred debris-covered and rock glaciers at its valley heads, some of which have been studied in detail regarding their dynamics and activity (vid. summary in Andrés et al. 2016). This work analyses block displacements and changes in the surface morphology of the Fremri-Grjótárdalur rock glacier (65◦43’N 19◦W, 1,245 m) and the Hóladalsjökull debris-covered glacier (65◦42’N; 18◦57’W, 1,330 m), located in the centre of Tröllaskagi peninsula. A Digital Photogrammetric WorkStation -Digi3d.NET(DPWS Digi3d) has been used in this study to compare the evolution of these landforms in aerial photographs taken at different years (1946, 1980, 1985 and 1994) and a 2000 ortho...
Following the Holocene Thermal Maximum, dated between 11 and 6 ka, the Neoglacial period was one ... more Following the Holocene Thermal Maximum, dated between 11 and 6 ka, the Neoglacial period was one of the progressive, fluctuating cooling that peaked during the Little Ice Age (LIA). The almost total absence of glacial tills prior to the LIA in the Pyrenees forces recourse to a high variety of proxies, including lacustrine sediments, palynological records, dendroclimatology, ice cores from glaciers and caves, speleothems, historical documentation and glacial records. This has enabled us to identify several colder periods during the mid-and late-Holocene: (i) the first phase of the Neoglacial period occurred at some time around 6 ka; (ii) a glacial pulse immediately before 3.4 ka; (iii) a glacial re-advance during the Dark Ages, i.e., immediately before the Medieval Climate Anomaly, between the fourth and ninth centuries; and (iv) the Little Ice Age, which started at the beginning of the fourteenth century and finished in the mid-nineteenth century. During the LIA, there was remarkable climate variability, with two, and probably three, glacial pulses, mainly between 1620 and 1715 and in the first half of the nineteenth century. Of all of the Holocene cold periods, most of the European paleoclimatic records coincide on the occurrence of the LIA. For the remaining Holocene cold periods, European records show high variability and uncertainty, particularly for the onset of the Neoglacial, although the phases of glacial pulses in the Pyrenees broadly coincide with those identified in the Alps and northern Europe.
Scripta Nova-revista Electronica De Geografia Y Ciencias Sociales, 2008
El Corral del Veleta (Sierra Nevada. Espana) cobija en su seno y bajo manto detritico hielo glaci... more El Corral del Veleta (Sierra Nevada. Espana) cobija en su seno y bajo manto detritico hielo glaciar fosil y permafrost alpino, restos, como minimo, de la Pequena Edad del Hielo (siglos XV/XIX). En la actualidad, estas masas heladas se encuentran en proceso de degradacion. Los analisis y controles que desde 2001 se vienen llevando a cabo en un glaciar rocoso incipiente instalado en el tercio oriental del Corral del Veleta muestran procesos continuados de subsidencia de su manto detritico, apoyado sobre las masas heladas referidas. La merma del manto nival durante el verano, las aguas de fusion y el grado de penetracion de la onda de radiacion externa en el suelo, son parametros clave que explican este mecanismo de subsidencia, que podria estar relacionado con variaciones climaticas que vienen detectandose desde hace decadas.
Pleistocene glaciers shaped the highest lands of the National Park of Sierra Nevada, South Spain.... more Pleistocene glaciers shaped the highest lands of the National Park of Sierra Nevada, South Spain. Alpine glaciers filled the western valleys of the massif with hundreds of meters of ice. Surface exposure dating shows evidence of glacial expansion during the Younger Dryas and the subsequent disappearance of glaciers of the massif during the Early Holocene. Since then, glacial records and lake sediments reveal that the massif has been ice-free for the most part of the Holocene, with the development of small glaciers during the coldest phases inside the highest northern cirques. This occurred at 2.8-2.7, 1.4-1.2 cal. ka BP and during the Little Ice Age (1300-1850 CE), when documentary sources confirm also the existence of some glaciers at the foot of the highest summits. This historical period was probably the coldest and wettest phase of the Holocene in the massif and recorded the largest glaciers of the current interglacial. Those glaciers finally melted away during the mid-20th century.
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires
The Skagafj€ orður fjord in northern Iceland is located between the Tr€ ollaskagi Peninsula in th... more The Skagafj€ orður fjord in northern Iceland is located between the Tr€ ollaskagi Peninsula in the east and the Skagi Peninsula in the west. The tributary valleys of the fjord originate in the highland area about 15 km north of the Hofsj€ okull icecap. The results of this work improve the knowledge of the deglaciation pattern in Skagafj€ orður and explore the adequacy of the 36 Cl cosmic ray exposure dating method in an Icelandic environment, where this method has rarely been applied to deglaciated surfaces. The 36 Cl dating method was applied to 13 rock samples taken on a transect from the coastal areas towards the highlands. All samples were obtained from rock outcrops with glacierpolished surfaces from the Last Glaciation and from one of the few well-preserved erratic boulders. The cosmogenic results, combined with previous radiocarbon results, indicate that the ice margin was situated in the outermost sector of Skagafj€ orður at approximately 17-15 ka BP. Subsequently, it retreated and occupied the central part of the fjord between 15 and 12 ka BP and then the innermost sector of the fjord about 11 ka BP. The samples collected between this position and the highlands show an average age of approximately 11 ka, indicating rapid deglaciation after the early Preboreal. These results agree with earlier studies of the deglaciation history of northern Iceland, reinforce previous deglaciation models in the area and enable a better understanding of glacial evolution in the North Atlantic from the Late Pleistocene to Holocene transition.
Through a detailed geomorphological study, including thourough mapping of the geomorphic features... more Through a detailed geomorphological study, including thourough mapping of the geomorphic features as well as 10 Be Cosmic-Ray Exposure (CRE) dating, the geomorphological evolution of the Mulhacén cirque since the maximum ice extent of the last glacial cycle until nowadays was determined. This glacial cirque is shaped on the northern face of the Mulhacén peak (3479 m a. .l., 37 03 12 N / 3 18 41 W), Sierra Nevada, southern Spain. It includes several depositional and erosional glacial landforms that allowed reconstructing its environmental evolution since the last glacial cycle. Furthermore, the sequence of glacial oscillations from this site was compared to that of other cirques of the massif, evidencing that: (i) new glaciers formed in these cirques during the Younger Dryas (YD), and (ii) disappeared at 11.7 ± 1.0 ka. Depending on the altitude, orientation and height of the cirque walls, the final deglaciation of the cirques generated a diversity of landscapes, including a wide range of glacial and periglacial landforms, such as polished surfaces, sequences of moraines, proto-rock glaciers or large rock glacier systems. No glaciers existed in the Sierra Nevada during the Middle Holocene. Only the cirques whose summits exceed 3300 m, are north-exposed and whose walls exceed 300 m high (i.e. Mulhacén and Veleta) hosted glaciers during Neoglacial phases, including the Little Ice Age (LIA) (approx. 1300-1850 CE). During these periods, climate oscillations favoured the formation of small glaciers in these cirques, which generated large moraine systems with either one polygenic ridge or a sequence of spaced frontal arcs. The existence of glaciers impeded the formation of permafrost-related Manuscript File Click here to vie linked References 2 landforms, such as rock glaciers and protalus lobes until the end of the LIA, when they started to form. These results are compared with the deglacial evolution in 55 cirques from Iberian mountains as well as from glacial cirques from other mid-latitude mountains and subpolar regions. The chronology of their deglaciation as well as the landforms generated during glacial retreat followed similar patterns, with no significant differences at regional scale. For each mountain range, the geomorphological diversity existing in each cirque depends on the local topographic characteristics although they formed during the same climatic phases.
This work defends and applies a new proposal for mapping debris-covered glaciers and rock glacier... more This work defends and applies a new proposal for mapping debris-covered glaciers and rock glaciers. This proposal combines highly accurate traditional methods, such as manual geomorphological photointerpretation, with novel digital techniques. The new methodological strategy applies rendering and lighting tools from Computer-Aided Design platforms and uses graphic design from Desktop Publishing Programs, to improve the geovisualization of geomorphological maps. This combination was applied to the debriscovered glacier and a set of rock glaciers located on the Tröllaskagi peninsula (northern Iceland). The result is a 1:4,500 scale geomorphological map of 16 km 2 , which for the first time maps the features that differentiate the debris-covered glacier from rock glaciers, as well as genetically different units within each formation and a long series of landforms characteristic of different processes. This map thus becomes a very useful tool in the evolutionary study of these formations in relation to the impact of climate change.
The timing of neoglacial advances in the Antarctic Peninsula (AP) is not yet well constrained. Ac... more The timing of neoglacial advances in the Antarctic Peninsula (AP) is not yet well constrained. Accurate temporal reconstruction of Neoglaciation in the AP is needed to better understand past glacial responses and regional and global teleconnections during the Holocene. Here, we examine all available information about neoglacial advances in the South Shetland Islands (SSI) as well as in the broader geographical context of the AP region and Antarctic continent. In order to shed light on the contrasting chronologies existing for neoglacial advances in these regions, we focused on a case study where a detailed picture of the Holocene deglaciation was already available. Lake sediments revealed that Byers Peninsula, west of Livingston Island (SSI), was fully deglaciated during the Holocene Thermal Maximum. To complement this approach, we identified glacially polished bedrock surfaces, erratic boulders and a moraine ridge near the present front of the glacier in the SE corner. We applied cosmogenic ray exposure (CRE) dating using in situ 36Cl for basalt rocks and 10Be for granitic rocks in: (i) 8 samples from glacial erratic and ice-rafted boulders, (ii) 2 samples from moraine boulders, (iii) 2 samples from polished bedrock surfaces, and (iv) 1 sample from an erratic boulder deposited on one of these surfaces. The CRE dates indicate that the onset of deglaciation started around 9.9 ± 1.2 ka, with two phases of glacier expansion during the Mid-Late Holocene forming moraines at~4.1 ± 0.5 and~1.0 ± 0.2 ka, respectively. The main neoglacial advances in the AP and the SSI were mostly synchronous and coincided with cold periods, as shown by other records (e.g. glacio-isostatic marine terraces, marine and lake sediments). In addition, these periods of glacial expansion show a similar timing to those recorded in the Arctic. These results suggest that Neoglaciation was driven by global climate forcing in both polar areas despite temporal variations at regional and local scale.
An accurate review of the literature on surface exposure dating methods shows evidence of the dif... more An accurate review of the literature on surface exposure dating methods shows evidence of the difficulty in applying cosmogenic dating methods to old moraines because of the intensity of Late Quaternary erosion processes. Moreover, as in some previous cases, we found also special difficulties in applying these methods to LIA moraines, due to the intensity of current paraglacial processes. The objective of this study is to apply cosmogenic dating methods to very old and very young moraines, which in both cases have been or are being affected intensively by erosion. With this purpose, we collected samples of boulders from moraines corresponding to: (a) the penultimate glaciation, and (b) the Little Ice Age (LIA), both from Sierra Nevada, in the south of the Iberian Peninsula. The sampling strategy was based on a preliminary accurate analysis of the geomorphological settings of two valley sites that Manuscript with line numbering and double line spacing Click here to view linked References resulted in the collection of only four boulder samples from an old moraine and three more from a very recent moraine. Using in situ produced cosmogenic 10 Be to date these boulders, the old samples yielded an age of ca. 130-135 ka for moraine stabilization. The younger samples indicate that the LIA moraine accretion probably occurred between the 14 th and 17 th centuries, with a subsequent stage of accumulation during the 19 th century as suggested by historical documents. Both, dating a glaciation that occurred prior to the last Pleistocene glacial cycle and dating LIA glacial stages are novel in the context of Iberian glaciations and agree with other palaeoenvironmental studies in Iberian and in other European mountains. The limited number of boulders adequate for cosmic-ray exposure dating prevents statistical methods to be applied, and therefore highlights the need to improve geomorphological criteria in sample selection.
Following the Holocene Thermal Maximum, dated between 11 and 6 ka, the Neoglacial period was one ... more Following the Holocene Thermal Maximum, dated between 11 and 6 ka, the Neoglacial period was one of the progressive, fluctuating cooling that peaked during the Little Ice Age (LIA). The almost total absence of glacial tills prior to the LIA in the Pyrenees forces recourse to a high variety of proxies, including lacustrine sediments, palynological records, dendroclimatology, ice cores from glaciers and caves, speleothems, historical documentation and glacial records. This has enabled us to identify several colder periods during the mid-and late-Holocene: (i) the first phase of the Neoglacial period occurred at some time around 6 ka; (ii) a glacial pulse immediately before 3.4 ka; (iii) a glacial re-advance during the Dark Ages, i.e., immediately before the Medieval Climate Anomaly, between the fourth and ninth centuries; and (iv) the Little Ice Age, which started at the beginning of the fourteenth century and finished in the mid-nineteenth century. During the LIA, there was remarkable climate variability, with two, and probably three, glacial pulses, mainly between 1620 and 1715 and in the first half of the nineteenth century. Of all of the Holocene cold periods, most of the European paleoclimatic records coincide on the occurrence of the LIA. For the remaining Holocene cold periods, European records show high variability and uncertainty, particularly for the onset of the Neoglacial, although the phases of glacial pulses in the Pyrenees broadly coincide with those identified in the Alps and northern Europe.
1º Planta Industrial. 2º Fosfato di Cálcico. 3º Estudio de Factibilidad. 4º Análisis Económico. 5... more 1º Planta Industrial. 2º Fosfato di Cálcico. 3º Estudio de Factibilidad. 4º Análisis Económico. 5º Los Fosfatos a nivel mundial son limitados, y Venezuela es uno de los pocos países privilegiados en poseer este recurso natural.
<p>In the Antarctic Peninsula (AP), the small ice caps distributed across its periphery and... more <p>In the Antarctic Peninsula (AP), the small ice caps distributed across its periphery and surrounding islands have recorded important ice volume changes since the end of the Last Glacial Cycle. These volume changes have occurred in the form of surface extent shrinking and ice thinning. The latter has been investigated only at a reduced number of locations. In this context, nunataks constitute key spots to assess the environmental evolution of deglaciated areas as they offer the opportunity to track the deglaciation history and reconstruct past ice losses by using Cosmic-Ray Exposure (CRE) dating. Indeed, nunataks are supposed to have played a prominent role in the vegetal and animal colonization of Antarctica.</p><p>The South Shetland Islands archipelago is one of the AP areas where past ice thinning has been least investigated, with only one study conducted in King George Island. In order to shed some light on the last deglaciation and its associated ice thinning, we apply <sup>10</sup>Be CRE dating to vertical sequences of glacially polished outcrops on two palaeonunataks and one nunatak distributed across the ice-cap covering part of the Hurd Peninsula (SW of Livingston Island): Reina Sof&#237;a Peak (62&#176;40'8" S, 60&#176;22'51" W, 273 m a.s.l.), Moores Peak (62&#176;41'21" S, 60&#176;20'42" W, 407 m a.s.l.) and Napier Peak (62&#176;40'18"S, 60&#176;19'31" W, 382 m a.s.l.).</p><p>Most of the resulting exposure ages provided a logical chronological sequence and allowed reconstructing past vertical changes of the ice surface. The uppermost surfaces of the Moores and Reina Sof&#237;a peaks became deglaciated during the Last Glacial Maximum (LGM), between ~24 ka and ~20 ka. Following the LGM, between ~20 and ~14 ka (Termination-1), a massive deglaciation occurred. This trend was especially exacerbated at around ~14 ka, triggering the onset of the deglaciation at other nunataks, such as the Napier Peak, in good agreement with the coetaneous global melt-water pulse 1a. From our results, we infer that ice shrinking during the Holocene must have been very limited compared to the post-LGM period.</p><p>Nevertheless, some of the exposure ages were either anomalously old or inconsistent, such as those found at the summits of the Reina Sof&#237;a and Moores peaks or at the base of the Napier nunatak. These artifacts suggest the occurrence of nuclide inheritance and are indicative of the conservation of previously exposed surfaces. These ages allow to qualitatively infer cold-based regimes characterized by basal ice frozen to bed, with slow mobility and inefficient subglacial erosion due to the gentle slope gradient, not capable of removing inherited nuclides accumulated during former exposure periods. But, as a whole, the dataset adds valuable knowledge on the polythermal character of the Hurd Peninsula Ice cap.</p><p>&#160;</p><p>This paper was supported by the project NUNANTAR (02/SAICT/2017 &#8211; 32002; Funda&#231;&#227;o para a Ci&#234;ncia e a Tecnologia, Portugal) and the College on Polar and Extreme Environments (University of Lisbon).</p>
The Tröllaskagi peninsula is located in north central Iceland, between the meridians of 19o30’W a... more The Tröllaskagi peninsula is located in north central Iceland, between the meridians of 19o30’W and 18o10’W, limited by the Skagafjörður fiord to the west and the Eyjafjörður fiord to the east, jutting out into the North Atlantic to latitude 66o12’N and linked to the central Icelandic highlands to the south. There are over a hundred debris-covered and rock glaciers at its valley heads, some of which have been studied in detail regarding their dynamics and activity (vid. summary in Andrés et al. 2016). This work analyses block displacements and changes in the surface morphology of the Fremri-Grjótárdalur rock glacier (65◦43’N 19◦W, 1,245 m) and the Hóladalsjökull debris-covered glacier (65◦42’N; 18◦57’W, 1,330 m), located in the centre of Tröllaskagi peninsula. A Digital Photogrammetric WorkStation -Digi3d.NET(DPWS Digi3d) has been used in this study to compare the evolution of these landforms in aerial photographs taken at different years (1946, 1980, 1985 and 1994) and a 2000 ortho...
Scripta Nova-revista Electronica De Geografia Y Ciencias Sociales, 2008
El Corral del Veleta (Sierra Nevada. Espana) cobija en su seno y bajo manto detritico hielo glaci... more El Corral del Veleta (Sierra Nevada. Espana) cobija en su seno y bajo manto detritico hielo glaciar fosil y permafrost alpino, restos, como minimo, de la Pequena Edad del Hielo (siglos XV/XIX). En la actualidad, estas masas heladas se encuentran en proceso de degradacion. Los analisis y controles que desde 2001 se vienen llevando a cabo en un glaciar rocoso incipiente instalado en el tercio oriental del Corral del Veleta muestran procesos continuados de subsidencia de su manto detritico, apoyado sobre las masas heladas referidas. La merma del manto nival durante el verano, las aguas de fusion y el grado de penetracion de la onda de radiacion externa en el suelo, son parametros clave que explican este mecanismo de subsidencia, que podria estar relacionado con variaciones climaticas que vienen detectandose desde hace decadas.
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires
The aim of this study was to generate practical recommendations to assist rheumatologists and der... more The aim of this study was to generate practical recommendations to assist rheumatologists and dermatologists in the management of cardiovascular (CV) comorbidities in patients with moderate-to-severe psoriasis (MS-PSO) and psoriatic arthritis (PsA). A two-round Delphi study was conducted. A panel of experts rated their agreement with a set of statements (n = 52) on a nine-point Likert scale (1 = totally disagree; 9 = totally agree). Statements were classified as inappropriate (median 1-3), irrelevant (median 4-6) or appropriate (median 7-9). Consensus was established when at least two-thirds of the panel responded with a score within any one range. A total of 25 experts, 60% rheumatologists and 40% dermatologists, participated in two consultation rounds. There was overall unanimity on the appropriateness of an initial assessment for CV risk factors in all patients with MS-PSO and PsA. Most panelists (88.0%) also supported the evaluation of patients' psychological and physical status. Additionally, most panelists (72.2%) agreed on a novel sequential approach for the management of CV comorbidities. This sequence starts with the assessment of hypertension, diabetes and dyslipidemia along with the identification of depression and anxiety disorders. Once these factors are under control, smoking cessation programs might be initiated. Finally, if patients have not met weight loss goals with lifestyle modifications, they should receive specialized treatment for obesity. This study has drawn up a set of practical recommendations that will facilitate the management of CV comorbidities in patients with MS-PSO and PsA.
Through a detailed geomorphological study, including thourough mapping of the geomorphic features... more Through a detailed geomorphological study, including thourough mapping of the geomorphic features as well as 10 Be Cosmic-Ray Exposure (CRE) dating, the geomorphological evolution of the Mulhacén cirque since the maximum ice extent of the last glacial cycle until nowadays was determined. This glacial cirque is shaped on the northern face of the Mulhacén peak (3479 m a. .l., 37 03 12 N / 3 18 41 W), Sierra Nevada, southern Spain. It includes several depositional and erosional glacial landforms that allowed reconstructing its environmental evolution since the last glacial cycle. Furthermore, the sequence of glacial oscillations from this site was compared to that of other cirques of the massif, evidencing that: (i) new glaciers formed in these cirques during the Younger Dryas (YD), and (ii) disappeared at 11.7 ± 1.0 ka. Depending on the altitude, orientation and height of the cirque walls, the final deglaciation of the cirques generated a diversity of landscapes, including a wide range of glacial and periglacial landforms, such as polished surfaces, sequences of moraines, proto-rock glaciers or large rock glacier systems. No glaciers existed in the Sierra Nevada during the Middle Holocene. Only the cirques whose summits exceed 3300 m, are north-exposed and whose walls exceed 300 m high (i.e. Mulhacén and Veleta) hosted glaciers during Neoglacial phases, including the Little Ice Age (LIA) (approx. 1300-1850 CE). During these periods, climate oscillations favoured the formation of small glaciers in these cirques, which generated large moraine systems with either one polygenic ridge or a sequence of spaced frontal arcs. The existence of glaciers impeded the formation of permafrost-related Manuscript File Click here to vie linked References 2 landforms, such as rock glaciers and protalus lobes until the end of the LIA, when they started to form. These results are compared with the deglacial evolution in 55 cirques from Iberian mountains as well as from glacial cirques from other mid-latitude mountains and subpolar regions. The chronology of their deglaciation as well as the landforms generated during glacial retreat followed similar patterns, with no significant differences at regional scale. For each mountain range, the geomorphological diversity existing in each cirque depends on the local topographic characteristics although they formed during the same climatic phases.
<p>In the Antarctic Peninsula (AP), the small ice caps distributed across its periphery and... more <p>In the Antarctic Peninsula (AP), the small ice caps distributed across its periphery and surrounding islands have recorded important ice volume changes since the end of the Last Glacial Cycle. These volume changes have occurred in the form of surface extent shrinking and ice thinning. The latter has been investigated only at a reduced number of locations. In this context, nunataks constitute key spots to assess the environmental evolution of deglaciated areas as they offer the opportunity to track the deglaciation history and reconstruct past ice losses by using Cosmic-Ray Exposure (CRE) dating. Indeed, nunataks are supposed to have played a prominent role in the vegetal and animal colonization of Antarctica.</p><p>The South Shetland Islands archipelago is one of the AP areas where past ice thinning has been least investigated, with only one study conducted in King George Island. In order to shed some light on the last deglaciation and its associated ice thinning, we apply <sup>10</sup>Be CRE dating to vertical sequences of glacially polished outcrops on two palaeonunataks and one nunatak distributed across the ice-cap covering part of the Hurd Peninsula (SW of Livingston Island): Reina Sof&#237;a Peak (62&#176;40'8" S, 60&#176;22'51" W, 273 m a.s.l.), Moores Peak (62&#176;41'21" S, 60&#176;20'42" W, 407 m a.s.l.) and Napier Peak (62&#176;40'18"S, 60&#176;19'31" W, 382 m a.s.l.).</p><p>Most of the resulting exposure ages provided a logical chronological sequence and allowed reconstructing past vertical changes of the ice surface. The uppermost surfaces of the Moores and Reina Sof&#237;a peaks became deglaciated during the Last Glacial Maximum (LGM), between ~24 ka and ~20 ka. Following the LGM, between ~20 and ~14 ka (Termination-1), a massive deglaciation occurred. This trend was especially exacerbated at around ~14 ka, triggering the onset of the deglaciation at other nunataks, such as the Napier Peak, in good agreement with the coetaneous global melt-water pulse 1a. From our results, we infer that ice shrinking during the Holocene must have been very limited compared to the post-LGM period.</p><p>Nevertheless, some of the exposure ages were either anomalously old or inconsistent, such as those found at the summits of the Reina Sof&#237;a and Moores peaks or at the base of the Napier nunatak. These artifacts suggest the occurrence of nuclide inheritance and are indicative of the conservation of previously exposed surfaces. These ages allow to qualitatively infer cold-based regimes characterized by basal ice frozen to bed, with slow mobility and inefficient subglacial erosion due to the gentle slope gradient, not capable of removing inherited nuclides accumulated during former exposure periods. But, as a whole, the dataset adds valuable knowledge on the polythermal character of the Hurd Peninsula Ice cap.</p><p>&#160;</p><p>This paper was supported by the project NUNANTAR (02/SAICT/2017 &#8211; 32002; Funda&#231;&#227;o para a Ci&#234;ncia e a Tecnologia, Portugal) and the College on Polar and Extreme Environments (University of Lisbon).</p>
The timing of neoglacial advances in the Antarctic Peninsula (AP) is not yet well constrained. Ac... more The timing of neoglacial advances in the Antarctic Peninsula (AP) is not yet well constrained. Accurate temporal reconstruction of Neoglaciation in the AP is needed to better understand past glacial responses and regional and global teleconnections during the Holocene. Here, we examine all available information about neoglacial advances in the South Shetland Islands (SSI) as well as in the broader geographical context of the AP region and Antarctic continent. In order to shed light on the contrasting chronologies existing for neoglacial advances in these regions, we focused on a case study where a detailed picture of the Holocene deglaciation was already available. Lake sediments revealed that Byers Peninsula, west of Livingston Island (SSI), was fully deglaciated during the Holocene Thermal Maximum. To complement this approach, we identified glacially polished bedrock surfaces, erratic boulders and a moraine ridge near the present front of the glacier in the SE corner. We applied cosmogenic ray exposure (CRE) dating using in situ 36Cl for basalt rocks and 10Be for granitic rocks in: (i) 8 samples from glacial erratic and ice-rafted boulders, (ii) 2 samples from moraine boulders, (iii) 2 samples from polished bedrock surfaces, and (iv) 1 sample from an erratic boulder deposited on one of these surfaces. The CRE dates indicate that the onset of deglaciation started around 9.9 ± 1.2 ka, with two phases of glacier expansion during the Mid-Late Holocene forming moraines at~4.1 ± 0.5 and~1.0 ± 0.2 ka, respectively. The main neoglacial advances in the AP and the SSI were mostly synchronous and coincided with cold periods, as shown by other records (e.g. glacio-isostatic marine terraces, marine and lake sediments). In addition, these periods of glacial expansion show a similar timing to those recorded in the Arctic. These results suggest that Neoglaciation was driven by global climate forcing in both polar areas despite temporal variations at regional and local scale.
The Tröllaskagi peninsula is located in north central Iceland, between the meridians of 19o30’W a... more The Tröllaskagi peninsula is located in north central Iceland, between the meridians of 19o30’W and 18o10’W, limited by the Skagafjörður fiord to the west and the Eyjafjörður fiord to the east, jutting out into the North Atlantic to latitude 66o12’N and linked to the central Icelandic highlands to the south. There are over a hundred debris-covered and rock glaciers at its valley heads, some of which have been studied in detail regarding their dynamics and activity (vid. summary in Andrés et al. 2016). This work analyses block displacements and changes in the surface morphology of the Fremri-Grjótárdalur rock glacier (65◦43’N 19◦W, 1,245 m) and the Hóladalsjökull debris-covered glacier (65◦42’N; 18◦57’W, 1,330 m), located in the centre of Tröllaskagi peninsula. A Digital Photogrammetric WorkStation -Digi3d.NET(DPWS Digi3d) has been used in this study to compare the evolution of these landforms in aerial photographs taken at different years (1946, 1980, 1985 and 1994) and a 2000 ortho...
Following the Holocene Thermal Maximum, dated between 11 and 6 ka, the Neoglacial period was one ... more Following the Holocene Thermal Maximum, dated between 11 and 6 ka, the Neoglacial period was one of the progressive, fluctuating cooling that peaked during the Little Ice Age (LIA). The almost total absence of glacial tills prior to the LIA in the Pyrenees forces recourse to a high variety of proxies, including lacustrine sediments, palynological records, dendroclimatology, ice cores from glaciers and caves, speleothems, historical documentation and glacial records. This has enabled us to identify several colder periods during the mid-and late-Holocene: (i) the first phase of the Neoglacial period occurred at some time around 6 ka; (ii) a glacial pulse immediately before 3.4 ka; (iii) a glacial re-advance during the Dark Ages, i.e., immediately before the Medieval Climate Anomaly, between the fourth and ninth centuries; and (iv) the Little Ice Age, which started at the beginning of the fourteenth century and finished in the mid-nineteenth century. During the LIA, there was remarkable climate variability, with two, and probably three, glacial pulses, mainly between 1620 and 1715 and in the first half of the nineteenth century. Of all of the Holocene cold periods, most of the European paleoclimatic records coincide on the occurrence of the LIA. For the remaining Holocene cold periods, European records show high variability and uncertainty, particularly for the onset of the Neoglacial, although the phases of glacial pulses in the Pyrenees broadly coincide with those identified in the Alps and northern Europe.
Scripta Nova-revista Electronica De Geografia Y Ciencias Sociales, 2008
El Corral del Veleta (Sierra Nevada. Espana) cobija en su seno y bajo manto detritico hielo glaci... more El Corral del Veleta (Sierra Nevada. Espana) cobija en su seno y bajo manto detritico hielo glaciar fosil y permafrost alpino, restos, como minimo, de la Pequena Edad del Hielo (siglos XV/XIX). En la actualidad, estas masas heladas se encuentran en proceso de degradacion. Los analisis y controles que desde 2001 se vienen llevando a cabo en un glaciar rocoso incipiente instalado en el tercio oriental del Corral del Veleta muestran procesos continuados de subsidencia de su manto detritico, apoyado sobre las masas heladas referidas. La merma del manto nival durante el verano, las aguas de fusion y el grado de penetracion de la onda de radiacion externa en el suelo, son parametros clave que explican este mecanismo de subsidencia, que podria estar relacionado con variaciones climaticas que vienen detectandose desde hace decadas.
Pleistocene glaciers shaped the highest lands of the National Park of Sierra Nevada, South Spain.... more Pleistocene glaciers shaped the highest lands of the National Park of Sierra Nevada, South Spain. Alpine glaciers filled the western valleys of the massif with hundreds of meters of ice. Surface exposure dating shows evidence of glacial expansion during the Younger Dryas and the subsequent disappearance of glaciers of the massif during the Early Holocene. Since then, glacial records and lake sediments reveal that the massif has been ice-free for the most part of the Holocene, with the development of small glaciers during the coldest phases inside the highest northern cirques. This occurred at 2.8-2.7, 1.4-1.2 cal. ka BP and during the Little Ice Age (1300-1850 CE), when documentary sources confirm also the existence of some glaciers at the foot of the highest summits. This historical period was probably the coldest and wettest phase of the Holocene in the massif and recorded the largest glaciers of the current interglacial. Those glaciers finally melted away during the mid-20th century.
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires
The Skagafj€ orður fjord in northern Iceland is located between the Tr€ ollaskagi Peninsula in th... more The Skagafj€ orður fjord in northern Iceland is located between the Tr€ ollaskagi Peninsula in the east and the Skagi Peninsula in the west. The tributary valleys of the fjord originate in the highland area about 15 km north of the Hofsj€ okull icecap. The results of this work improve the knowledge of the deglaciation pattern in Skagafj€ orður and explore the adequacy of the 36 Cl cosmic ray exposure dating method in an Icelandic environment, where this method has rarely been applied to deglaciated surfaces. The 36 Cl dating method was applied to 13 rock samples taken on a transect from the coastal areas towards the highlands. All samples were obtained from rock outcrops with glacierpolished surfaces from the Last Glaciation and from one of the few well-preserved erratic boulders. The cosmogenic results, combined with previous radiocarbon results, indicate that the ice margin was situated in the outermost sector of Skagafj€ orður at approximately 17-15 ka BP. Subsequently, it retreated and occupied the central part of the fjord between 15 and 12 ka BP and then the innermost sector of the fjord about 11 ka BP. The samples collected between this position and the highlands show an average age of approximately 11 ka, indicating rapid deglaciation after the early Preboreal. These results agree with earlier studies of the deglaciation history of northern Iceland, reinforce previous deglaciation models in the area and enable a better understanding of glacial evolution in the North Atlantic from the Late Pleistocene to Holocene transition.
Through a detailed geomorphological study, including thourough mapping of the geomorphic features... more Through a detailed geomorphological study, including thourough mapping of the geomorphic features as well as 10 Be Cosmic-Ray Exposure (CRE) dating, the geomorphological evolution of the Mulhacén cirque since the maximum ice extent of the last glacial cycle until nowadays was determined. This glacial cirque is shaped on the northern face of the Mulhacén peak (3479 m a. .l., 37 03 12 N / 3 18 41 W), Sierra Nevada, southern Spain. It includes several depositional and erosional glacial landforms that allowed reconstructing its environmental evolution since the last glacial cycle. Furthermore, the sequence of glacial oscillations from this site was compared to that of other cirques of the massif, evidencing that: (i) new glaciers formed in these cirques during the Younger Dryas (YD), and (ii) disappeared at 11.7 ± 1.0 ka. Depending on the altitude, orientation and height of the cirque walls, the final deglaciation of the cirques generated a diversity of landscapes, including a wide range of glacial and periglacial landforms, such as polished surfaces, sequences of moraines, proto-rock glaciers or large rock glacier systems. No glaciers existed in the Sierra Nevada during the Middle Holocene. Only the cirques whose summits exceed 3300 m, are north-exposed and whose walls exceed 300 m high (i.e. Mulhacén and Veleta) hosted glaciers during Neoglacial phases, including the Little Ice Age (LIA) (approx. 1300-1850 CE). During these periods, climate oscillations favoured the formation of small glaciers in these cirques, which generated large moraine systems with either one polygenic ridge or a sequence of spaced frontal arcs. The existence of glaciers impeded the formation of permafrost-related Manuscript File Click here to vie linked References 2 landforms, such as rock glaciers and protalus lobes until the end of the LIA, when they started to form. These results are compared with the deglacial evolution in 55 cirques from Iberian mountains as well as from glacial cirques from other mid-latitude mountains and subpolar regions. The chronology of their deglaciation as well as the landforms generated during glacial retreat followed similar patterns, with no significant differences at regional scale. For each mountain range, the geomorphological diversity existing in each cirque depends on the local topographic characteristics although they formed during the same climatic phases.
This work defends and applies a new proposal for mapping debris-covered glaciers and rock glacier... more This work defends and applies a new proposal for mapping debris-covered glaciers and rock glaciers. This proposal combines highly accurate traditional methods, such as manual geomorphological photointerpretation, with novel digital techniques. The new methodological strategy applies rendering and lighting tools from Computer-Aided Design platforms and uses graphic design from Desktop Publishing Programs, to improve the geovisualization of geomorphological maps. This combination was applied to the debriscovered glacier and a set of rock glaciers located on the Tröllaskagi peninsula (northern Iceland). The result is a 1:4,500 scale geomorphological map of 16 km 2 , which for the first time maps the features that differentiate the debris-covered glacier from rock glaciers, as well as genetically different units within each formation and a long series of landforms characteristic of different processes. This map thus becomes a very useful tool in the evolutionary study of these formations in relation to the impact of climate change.
The timing of neoglacial advances in the Antarctic Peninsula (AP) is not yet well constrained. Ac... more The timing of neoglacial advances in the Antarctic Peninsula (AP) is not yet well constrained. Accurate temporal reconstruction of Neoglaciation in the AP is needed to better understand past glacial responses and regional and global teleconnections during the Holocene. Here, we examine all available information about neoglacial advances in the South Shetland Islands (SSI) as well as in the broader geographical context of the AP region and Antarctic continent. In order to shed light on the contrasting chronologies existing for neoglacial advances in these regions, we focused on a case study where a detailed picture of the Holocene deglaciation was already available. Lake sediments revealed that Byers Peninsula, west of Livingston Island (SSI), was fully deglaciated during the Holocene Thermal Maximum. To complement this approach, we identified glacially polished bedrock surfaces, erratic boulders and a moraine ridge near the present front of the glacier in the SE corner. We applied cosmogenic ray exposure (CRE) dating using in situ 36Cl for basalt rocks and 10Be for granitic rocks in: (i) 8 samples from glacial erratic and ice-rafted boulders, (ii) 2 samples from moraine boulders, (iii) 2 samples from polished bedrock surfaces, and (iv) 1 sample from an erratic boulder deposited on one of these surfaces. The CRE dates indicate that the onset of deglaciation started around 9.9 ± 1.2 ka, with two phases of glacier expansion during the Mid-Late Holocene forming moraines at~4.1 ± 0.5 and~1.0 ± 0.2 ka, respectively. The main neoglacial advances in the AP and the SSI were mostly synchronous and coincided with cold periods, as shown by other records (e.g. glacio-isostatic marine terraces, marine and lake sediments). In addition, these periods of glacial expansion show a similar timing to those recorded in the Arctic. These results suggest that Neoglaciation was driven by global climate forcing in both polar areas despite temporal variations at regional and local scale.
An accurate review of the literature on surface exposure dating methods shows evidence of the dif... more An accurate review of the literature on surface exposure dating methods shows evidence of the difficulty in applying cosmogenic dating methods to old moraines because of the intensity of Late Quaternary erosion processes. Moreover, as in some previous cases, we found also special difficulties in applying these methods to LIA moraines, due to the intensity of current paraglacial processes. The objective of this study is to apply cosmogenic dating methods to very old and very young moraines, which in both cases have been or are being affected intensively by erosion. With this purpose, we collected samples of boulders from moraines corresponding to: (a) the penultimate glaciation, and (b) the Little Ice Age (LIA), both from Sierra Nevada, in the south of the Iberian Peninsula. The sampling strategy was based on a preliminary accurate analysis of the geomorphological settings of two valley sites that Manuscript with line numbering and double line spacing Click here to view linked References resulted in the collection of only four boulder samples from an old moraine and three more from a very recent moraine. Using in situ produced cosmogenic 10 Be to date these boulders, the old samples yielded an age of ca. 130-135 ka for moraine stabilization. The younger samples indicate that the LIA moraine accretion probably occurred between the 14 th and 17 th centuries, with a subsequent stage of accumulation during the 19 th century as suggested by historical documents. Both, dating a glaciation that occurred prior to the last Pleistocene glacial cycle and dating LIA glacial stages are novel in the context of Iberian glaciations and agree with other palaeoenvironmental studies in Iberian and in other European mountains. The limited number of boulders adequate for cosmic-ray exposure dating prevents statistical methods to be applied, and therefore highlights the need to improve geomorphological criteria in sample selection.
Following the Holocene Thermal Maximum, dated between 11 and 6 ka, the Neoglacial period was one ... more Following the Holocene Thermal Maximum, dated between 11 and 6 ka, the Neoglacial period was one of the progressive, fluctuating cooling that peaked during the Little Ice Age (LIA). The almost total absence of glacial tills prior to the LIA in the Pyrenees forces recourse to a high variety of proxies, including lacustrine sediments, palynological records, dendroclimatology, ice cores from glaciers and caves, speleothems, historical documentation and glacial records. This has enabled us to identify several colder periods during the mid-and late-Holocene: (i) the first phase of the Neoglacial period occurred at some time around 6 ka; (ii) a glacial pulse immediately before 3.4 ka; (iii) a glacial re-advance during the Dark Ages, i.e., immediately before the Medieval Climate Anomaly, between the fourth and ninth centuries; and (iv) the Little Ice Age, which started at the beginning of the fourteenth century and finished in the mid-nineteenth century. During the LIA, there was remarkable climate variability, with two, and probably three, glacial pulses, mainly between 1620 and 1715 and in the first half of the nineteenth century. Of all of the Holocene cold periods, most of the European paleoclimatic records coincide on the occurrence of the LIA. For the remaining Holocene cold periods, European records show high variability and uncertainty, particularly for the onset of the Neoglacial, although the phases of glacial pulses in the Pyrenees broadly coincide with those identified in the Alps and northern Europe.
1º Planta Industrial. 2º Fosfato di Cálcico. 3º Estudio de Factibilidad. 4º Análisis Económico. 5... more 1º Planta Industrial. 2º Fosfato di Cálcico. 3º Estudio de Factibilidad. 4º Análisis Económico. 5º Los Fosfatos a nivel mundial son limitados, y Venezuela es uno de los pocos países privilegiados en poseer este recurso natural.
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