Journal of Maps, 2008, 235-247
Geomorphological map of the Alta Ribagorza
(Central Pyrenees, Spain)
JAVIER CHUECA CÍA1 and ASUNCIÓN JULIÁN ANDRÉS2
1 Departamento
de Geografı́a y Ordenación del Territorio, Facultad de Ciencias Humanas y de la
Educación, Universidad de Zaragoza, Plaza de la Universidad 3, 22002-Huesca, Spain;
[email protected]
2 Departamento
de Geografı́a y Ordenación del Territorio, Facultad de Filosofı́a y Letras, Universidad de
Zaragoza, Campus Plaza San Francisco, 50009-Zaragoza, Spain;
(Received 29th January 2008; Revised 11th July 2008; Accepted 15th July 2008)
Abstract: The 1:50,000 geomorphological map of the Pyrenean Alta Ribagorza is
presented here. The Spanish Alta Ribargoza is located in the northern sector of the
provinces of Huesca and Lérida, and includes the highest summit of the Pyrenean
mountains (Pico de Aneto, 3404 m a.s.l.). The mapped sector measures approximate 700
km2 . The basic source of information for the completion of the map was derived from the
photointerpretation of two series of aerial photos (the 1981 “Pirineos Sur” flight, scale
1:30,000, black and white; and the 2006 PNOA flight, scale 1:5,000, colour), and field
work. The map-legend includes 44 elements classified into six main sections, covering
lithology and structure, processes and landforms of glacial, periglacial, nival, hillslope,
karstic and fluvial origin, and conventional symbols. The variety of the identified
processes and landforms demonstrates the geomorphological richness of this mid-latitude,
high-mountain area, and the map constitutes a useful tool for land management.
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ISSN 1744-5647
http://www.journalofmaps.com
Journal of Maps, 2008, 235-247
1.
Chueca, J. & Julián, A.
Introduction
The geomorphological cartography in the Spanish Central Pyrenees has
several precedents, mainly centered in the Gállego and Ésera river
catchments (Garcı́a Ruiz, 1989; Garcı́a Ruiz et al., 1992; Rengers et al.,
1991; Chueca, 1993; Chueca et al., 2000; Serrano, 1998; Peña et al., 2002).
However, many sectors still lack detailed mapping. One of them, of which
we present here the geomorphological cartography on a scale of 1:50.000, is
the Alta Ribagorza region, of marked interest due to the presence of a
notable variety of processes and landforms characteristic of mid-latitude
high mountain areas.
2.
Study area
The Alta Ribargoza is located in the north-eastern sector of the province of
Huesca and, marginally, in the north-western end of the province of Lérida
(Figure 1). Drained by the rivers Ésera, Isábena, Baliera and Noguera
Ribagorzana, it includes some of the highest summits of the Pyrenean
mountains: Aneto (3404 m a.s.l.), Maldito (3350 m) and Maladeta (3308
m) peaks. Pleistocene glaciers formed the basic relief features, with minor
transformation taking place during the Holocene by periglacial, nival,
hillslope, karstic and fluvial processes.
From a geological perspective (Riba et al., 1972), the study area comprises
two of the main Pyrenean units: 1) the Pirineo Axial (Axial Pyrenees),
characterized by granitic intrusions (Maladeta, Besiberris) and Paleozoic
metamorphic sediments (slates, schists, quartzites and limestones of Sierra
Negra, Castanesa, Cibollés, etc.); and 2) the Sierras Interiores (Inner
Sierras), a band of Mesozoic calcareous rocks (Turbón, Ballabriga)
occasionally covered by continental deposits of Tertiary age (Sierra de Sis).
The climate reflects the transition between the Atlantic, humid influences
of the western Pyrenean regions, and the continental Mediterranean of the
eastern Pyrenees. The mean annual air temperature varies from −0.5◦ C at
3000 m to +6.8◦ C at 1500 m; however, coldest month average temperatures
reaches −4.3◦ C at 3000 m and +0.3◦ C at 1500 m. Average annual
precipitation varies from 2600 mm (3000 m) to 1400 mm (1500 m).
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Journal of Maps, 2008, 235-247
Chueca, J. & Julián, A.
Figure 1. Location map of the study area.
Discontinuous and sporadic permafrost has been reported in the Maladeta
massif (climate data for the region were provided by the Spanish Instituto
Nacional de Meteorologı́a; 12 observatories with temperature and
precipitation records with over 20 years of data recording were used;
Chueca (1993)).
3.
Material and methods
The mapped sector is included in the sheets of the Spanish 1:50,000 Mapa
Topográfico Nacional numbers 180 (Benasque), 181 (Esterri d’Aneu), 212
(Campo), 213 (Pont de Suert) and 251 (Arén), and measures approximately
700 km2 . The basic source of information for the completion of the map
was derived from the photointerpretation of two series of aerial flights: 1)
the 1981 “Pirineos Sur” flight (Instituto Geográfico Nacional), scale
1:30,000, black and white (Figure 2); and 2) the 2006 PNOA (Plan
Nacional de Ortofotografı́a Aérea) flight, scale 1:5,000, colour (Figure 3).
This information was complemented with the pertinent campaigns of field
work which include the detailed surveying of numerous photointerpretated
sectors (due to their particular geomorphological interest).
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Journal of Maps, 2008, 235-247
Chueca, J. & Julián, A.
Figure 2. 1981 “Pirineos Sur” flight: arêtes, glacial cirque limits and hörner surrounding the
Maladeta glacier (Maladeta massif) (see Geomorphological Map for the interpretation of the
depicted area).
The content of the map legend is based on Peña et al. (1997), who designed
a legend for geomorphological maps at 1:25,000/1:50,000 scales which has
been used in the geomorphological cartography made by our research group
(Departamento de Geografı́a y Ordenación del Territorio, Universidad de
Zaragoza) since the 1980’s.
4.
Results and discussion
The information shown in the map has been structured in six main sections:
1) lithology and structure, 2) glacial, periglacial and nival processes and
landforms, 3) hillslope processes and landforms, 4) karstic processes and
landforms, 5) fluvial processes and landforms and 6) conventional symbols.
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Journal of Maps, 2008, 235-247
Chueca, J. & Julián, A.
Figure 3. 2006 PNOA flight: structural cuestas, hogbacks and razorbacks in the limestones
of the Turbón massif. Talus slopes, an inactive rock glacier generated from masive rockfalls,
avalanche tracks and cones and morainic ridges are also visible (see Geomorphological Map for
the interpretation of the depicted area).
4.1
Lithology and structure
This section includes different rock groups classified according to their
origin and age: post-hercynian crystalline rocks (Figure 4), Paleozoic
metamorphic and sedimentary rocks, Mesozoic sedimentary rocks, and
Tertiary sedimentary rocks. Main faults are also indicated. The structural
and substructural elements mapped are: scarps associated with cuestas and
hogbacks, razorbacks, major watershed ridges, minor watershed ridges and
conglomerate tower-type (mallo) landforms.
The structural cuestas, hogbacks and razorbacks are linked to resistant
layered rocks, mainly limestones and sandstones (Benasque, Villarrué,
Turbón or Chordal sectors). Major and minor substructural watersheds are
located in the Paleozoic slates (Sierra Negra or Sierra del Cubilar) and in
the Tertiary conglomerates (Sierra de Sis, Sierra del Puxó).
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Journal of Maps, 2008, 235-247
Chueca, J. & Julián, A.
Figure 4. Arêtes and abraded surfaces in the post-hercynian granites of the Maladeta massif.
4.2
Glacial, periglacial and nival processes and
landforms
Due to its altitude, glacial processes and landforms have a wide
representation in the study area. The legend includes the following items:
present-day glaciers and glacierets (former glaciers motionless today),
major glacial landscape morphologies (arêtes and glacial cirque limits, main
peaks and hörner, cols), erosive landforms (U-shaped valleys, upper limits
of overdeepened glacial basins, overdeepened glacial basins, abraded
surfaces with roches moutonnées), depositional landforms (tills and
morainic ridges, proglacial fans) and glacial lakes.
Glaciers (Maladeta, Aneto, Barrancs and Tempestades) and glacierets
(Coronas), are located near the highest summits of the Maladeta massif,
above 2700 m a.s.l. The ice erosive action linked to Quaternary glaciations
is well-preserved in the Ésera and Noguera Ribagorzana upper valleys,
where resistant crystalline lithologies (granites, granodiorites) dominate.
Those two valleys (and the Turbón massif, located in the south-western
sector of the map) also present numerous examples of depositional
landforms corresponding to different glacial stages: Llauset and Senet
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Journal of Maps, 2008, 235-247
Chueca, J. & Julián, A.
sectors in the Noguera Ribagorzana, and Cerler and Ampriu sectors in the
Ésera. Glacial lakes or ibones (lakes and infilled lakes with peat deposits)
are mostly located in the uppermost sections of the Ésera and Noguera
Ribagorzana river valleys: lakes of Cregüeña, Barrancs, Anglios, Rius, etc.)
(Figure 5).
Figure 5. Glacial lakes in the overdeepened glacial basin of the Anglios sector.
Morphologies associated with periglacial (and glacial) conditions are the
rock glaciers, abundant in the granites of the Anglios and Besiberris ridges.
Talus slopes are also included in this periglacial domain, and are widely
distributed throughout the study area (Figure 6). Mapped nival landforms
and processes are the main avalanche tracks and cones: they are located in
the high altitude sierras of the northern part of the Alta Ribagorza
(Maladeta, Sierra Negra, Besiberris, etc.) and in the slopes of the Turbón
massif.
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Journal of Maps, 2008, 235-247
Chueca, J. & Julián, A.
Figure 6. Talus slopes and inactive rock glacier covering a highly karstified area near Pico de
la Mina.
4.3
Hillslope processes and landforms
This section includes hillslopes covered by individually detached rocks, mass
movements scars, rockfalls, slides, flows, areas with solifluction/gelifluction,
and sectors of concentrated water flow (rills and gullies).
Mass wasting processes are linked to different lithologies: rockfalls develop
mainly on calcareous and conglomeratic rocks (Turbón, Tozal de Sis).
Lithologies with potential high plasticity like the slates or marls produce
major slides (Baliera or Vallibierna valleys, Ampriu) and flows (Torre la
Ribera, Ampriu). The solifluction/gelifluction spreads widely in the
pastures of the geoecological subalpine and alpine zones, above the upper
timber-line. Rills and gullies are mainly located on the soft soils that cover
the highest sectors of the Paleozoic metamorphic and sedimentary rocks
(Sierra Negra, upper Isbena, Baliera and Llauset valleys) and in the marls
of the Villacarlı́ stream area (Figure 7).
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Journal of Maps, 2008, 235-247
Chueca, J. & Julián, A.
Figure 7. Rills and gullies in the blue marls of the Villacarlı́ stream area.
4.4
Karstic processes and landforms
This section groups four categories: highly karstified areas, streamsinks,
major dolines and poljes. The three most representative sectors, with
numerous examples of streamsinks, doline-fields and karren, are located: 1)
to the north of the Maladeta massif (Plan d’Están-Plan d’Aigualluts area),
on Paleozoic limestones (Figure 8); 2) on the calcareous rocks of Mesozoic
age placed around the Turbón massif (Puerto de la Munia, El Toux,
Selvaplana, Turbón de d’Alt and La Plana del Turbón); and 3) on the
Tertiary limestones of the Sierra de Chordal.
4.5
Fluvial processes and landforms
This part of the legend includes fluvial elements such as the fluvial network
(rivers, minor streams or barrancos), floodplains, fluvial terraces, alluvial
cones and accumulation glacis.
Fluvial terraces are rare in the region, due to the erosive action of the
Pleistocene glaciers. The best examples are located at the confluence of the
Isábena river with the Villacarlı́ stream (Figure 9). The junction of the
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Journal of Maps, 2008, 235-247
Chueca, J. & Julián, A.
Figure 8. The El Forau d’Aigualluts streamsink in the Paleozoic limestones (Maladeta massif
sector).
lateral barrancos with the main river floodplains frequently adopts a
morphology in alluvial cones (barrancos or ravines of Remascaró, Senet,
Vilaller, etc.). The best preserved accumulation glacis are located on the
northern slopes of the Sierra del Chordal.
4.6
Conventional symbols
Built-up areas, and the other prominent cultural element in this
high-mountain landscape, reservoirs, are indicated.
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Journal of Maps, 2008, 235-247
Chueca, J. & Julián, A.
Figure 9. Fluvial terraces in the Isábena river, near Biescas de Obarra.
5.
Conclusions
Made from photointerpretation and field work, the 1:50,000
geomorphological map of the Pyrenean Alta Ribagorza is presented here.
The map-legend includes 44 elements classified into six main sections,
covering lithology and structure, processes and landforms of glacial,
periglacial, nival, hillslope, karstic and fluvial origin, and conventional
symbols.
The variety of the identified processes and landforms reveals the
geomorphological richness of this mid-latitude, high-mountain area,
including: 1) elements inherited from previous climatic conditions (glaciers,
moraines, etc.) whose singularity in the Pyrenees makes their conservation
and protection necessary; and 2) fully active elements (nival, hillslope,
fluvial processes) that should in some cases be controlled to prevent risks.
The map presented here, therefore, constitutes a useful tool for the land
management of this Pyrenean region, and can be a starting point for
derivative maps of applied value: landscape maps used in the design and
planning of natural protected areas; hazard mapping of mass movements or
avalanches; mapping of erosive activity.
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Journal of Maps, 2008, 235-247
Chueca, J. & Julián, A.
Software
Geomorphological processes and landforms were identified using aerial
photographs and digitized in Auto CAD (v.14). This information was later
imported into the Macromedia FreeHand (v.11) software, where the final
design and layout work was done.
Acknowledgements
We gratefully acknowledge the comments of the editor and referees which
helped us to improve the paper and the map.
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