Baartman, J.E.M.

Schoorl, J.M.

Veldkamp, A.

English

Name not available

Controls on Late Quaternary landscape development in the Upper Guadalentín Basin, Murcia, SE Spain

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Wageningen Yield 

Controls on Late Quaternary Landscape development in the Upper 
Guadalentin Basin, Murcia, SE Spain 
 
 
J.E.M. Baartman(1), A. Veldkamp(1) 
 
(1) Wageningen University, Land Dynamics Group, P.O. Box 47, 6700 AA Wageningen, The 
Netherlands. E-mail: jantiene.baartman@wur.nl 
 
 
ABSTRACT  
 
Landscapes in South-eastern Spain have developed in response to tectonics, climatic 
fluctuations and, more recently, to human action. In the valleys, fluvial and colluvial 
sediments are found in the form of river terraces, pediments and slope deposits. We studied 
these sediments to evaluate landscape dynamics and the processes of sedimentation and 
erosion in the semi-arid region of the Guadalentín Basin, Murcia Province, SE Spain.  
The objective of the study is to deduce controls on Late Quaternary and Holocene landscape 
development. Fieldwork was carried out on the reach of the Upper Guadalentin, upstream of 
the city of Lorca, and two of its tributaries (Rio Velez and Rambla de Torrealvilla). River 
terrace levels were mapped using GPS and presence of gravel layers in outcrops. For the 
Rambla de Torrealvilla, more detailed sediment descriptions show their build-up. Charcoal 
was found and dated (14C) on ten locations, while 15 samples for Optically Stimulated 
Luminescence (OSL) dating were taken to have an age-control on processes of 
sedimentation and erosion.  
While the OSL dating measurements and analysis are still in process at this time, some 
preliminary results are given. Several terrace levels are identified along the Rio Guadalentin 
and the Rio Velez. These have formed in response to regional and/or global changes in 
climate. However, local mechanisms have played an important role in the area, overruling 
regional dynamics. From finely layered sediments, it is deduced that a lake existed during 
some time in the area, caused by a blockage of the valley. This lake was filled in with 
sediments and a delta was build at its end, interfering with terrace levels. When the blockage 
was broken through, lake sediments have been removed and after incision, younger terraces 
have developed.  
The Torrealvilla tributary is draining the Lorca Basin, and sediments seem to be younger 
than those along the Guadalentin and Velez rivers. Infilling of the basin and incomplete 
removal has shaped this valley. Outcrops in the gully sidewall show stacked layers of large to 
fine gravels and fine sediments with smaller gravel layers in between. 
We will present a conceptual model of landscape development since the Late Quaternary 
based on the age control (14C and OSL) and field observations. This reconstruction is 
correlated to climatic fluctuations and rates of sedimentation and erosion are approximated 
on a millennial timescale. Following this approach of longer-term geomorphological 
investigation of landscape development, we can ultimately put the relative contribution of 
human actions in the context of natural erosion and sedimentation processes. 
 
Keywords: Landscape development, Guadalentin Basin, Late Quaternary 
 
 
INTRODUCTION 
Landscapes in southeastern Spain have developed in response to tectonics, climatic 
fluctuations and, more recently, to human action. In the valleys, fluvial and colluvial 
sediments are found in the form of river terraces, pediments and slope deposits. We studied 
these sediments to evaluate landscape dynamics and the controls on sedimentation and 
erosion processes in the semi-arid region of the Guadalentín Basin, Murcia Province. 
TOPIC 3: FLUVIAL MORPHOLOGY
457
Research in this area has focused on recent processes such as gully dynamics as a result of 
intense rainstorms (Vandekerckhove et al., 2000; Bull et al., 1999; Hooke and Mant, 2000; 
Hooke et al., 2005), hillslope erosion (Bracken and Kirkby, 2005), scale-threshold effects 
(Cammeraat, 2004), the impact of land cover and land use change (Kirkby et al., 2002) and  
land degradation and desertification (Van Wesemael et al., 2006; Oñate and Peco, 2005). 
These recent processes have not, up till now, been placed in the larger timeframe of 
landscape dynamics. 
Quaternary and Holocene landscape dynamics are relatively sparsely assessed for the 
Guadalentin Basin. Baumhauer and Schütt (2006) made three augerings in an alluvial fan in 
the northwestern part of the Guadalentin Basin. Combined with 14C datings on charcoal 
pieces and chemical analysis of the sediments, they made a reconstruction of environmental 
conditions from the Late Glacial to recent times. Benito et al. (2006, 2008) applied 
palaeoflood hydrology to the Rio Guadalentin, upstream of the Valdeinfierno artificial lake. 
Calmel-Avila (2000) made a reconstruction of the morphological evolution of the lower 
Guadalentin (near Librilla), with the objective to identify phases of erosion and sedimentation 
over the past 10,000 years and to analyse the natural and human induced processes that 
could have taken place. Fuentes et al. (2005) describe an archeological site in Lorca from 
which four phases of occupation are deduced.  
 
The objective of this study is to understand and develop a conceptual model for Late 
Quaternary and Holocene landscape development for the Upper Guadalentin Basin. 
Subsequently, correlation of sedimentation and erosion processes to climatic variations, 
flood events and/or human activity is possible. Ultimately, the relative contribution of natural 
and human induced processes could be assessed using this approach. 
 
Research area 
The Guadalentin Basin (~3300 km2) is located in Murcia Province, southeastern Spain. Our 
research area is restricted to the upper part of the Rio Guadalentin, upstream of the city of 
Lorca (Fig. 1). We focussed on the Rio Guadalentin upstream of Lorca and two tributaries; 
the Rambla de Torrealvilla and the Rio Velez (Fig. 1). Altitude ranges from 300 – 1500 masl. 
Current climate is semi-arid Mediterranean. Average annual precipitation is about 300 mm, 
with 75% of rainfall in spring (mainly April) and autumn (mainly October) and high annual 
variability (Navarro Hervás, 1991). Semi-natural vegetation in the research area consists 
mainly of natural shrubs and forest. Land use is mainly dryland farming and irrigated crops. 
Geologically, the research area is located in the Betic Cordillera, a west-east oriented alpine 
orogenic belt that can be subdivided into an Internal and External Zone. The External Zone 
consists dominantly of non-metamorphic sedimentary rocks deposited during the Mesozoic 
(limestones, dolomites and marls) and Cenozoic (sandstones, (sandy) marls and 
conglomerates). The Internal Zone is formed by nappe complexes with lithologies ranging 
from highly metamorphic schists and phyllites to non-metamorphosed calcarenites, 
conglomerates and marls (Geel and Roep, 1998; IGME, 1981). The Lorca-Alhama Fault 
forms the graben of the active Guadalentin Depression. 
 
 
METHODS  
 
During fieldwork, an inventory of sediments was made along the three parts of the river. 
Presence of gravel, imbrication and stratification, deposits on top of the gravel layer and 
thickness of the gravel layer was investigated and their location recorded using a GPS 
(Garmin eTrex Legend). Relative height above the river was calculated. 
Charcoal pieces were found on ten locations (Fig. 1). These were radiocarbon dated using 
the Accelarator Mass Spectometer (AMS) at the Center for Isotope Research, University of 
Groningen, the Netherlands (Gottdang et al., 1995).  
 
ÁREA TEMÁTICA 3: MORFOLOGÍA FLUVIAL
458
 
Fig. 1: Research area (DEM) with indication of rivers. Dots indicate location of charcoal and 
OSL samples. 
 
To determine the timing and deduce rates of sediment deposition, OSL dating was used. 
This method determines the last time sand grains were exposed to sunlight, i.e. burial of the 
sediment. Samples were taken on 15 locations; 8 in the Rambla de Torrealvilla, three along 
the Rio Guadalentin and three in the Rio Velez. Samples were taken in the courser parts of 
the sediments, to ensure that sufficient large-sized quartz grains were present. Metal cores 
(diameter ~10cm; length ~50cm) were hammered into the sediment; sealed and transported 
to the laboratory. Analysis is at the moment of writing being carried out at the Netherlands 
Centre for Luminescence Dating (NCL) in Delft.  
 
 
RESULTS AND DISCUSSION 
 
Preliminary results are given here, as OSL dating results are not yet available at the time of 
writing. Several terrace levels are found ranging in height above the river from 2 to more than 
30m. Finely layered sediments are found, indicating that a lake existed during some time. 
This is being investigated at the moment. After breakthrough of the blockage, lake-sediments 
were (partly) removed by erosion and the last two terrace levels were formed afterwards. The 
existence of the lake influenced erosion and deposition upstream, as local base level 
changed abruptly. Gravel found upstream is possibly from a delta that formed at the far end 
of the lake. In this case, local processes are clearly more important than regional (climatic) 
controls on landscape formation. 
Results from charcoal dating give ages between 140 yr BP for the most recent sediments to 
about 5000 yr BP for the lowest (exposed) sediments in the Rambla de Torrealvilla. For 
charcoal found along the Rio Velez ages of about 11 and  14 ka BP were found. This implies 
that sediments in the Lorca Basin, where the Rambla de Torrealvilla is located, are relatively 
young compared to the sediments along the Rio Velez.  
 
TOPIC 3: FLUVIAL MORPHOLOGY
459
A complete reconstruction of landscape forming processes and their relative importance in 
the area is being made. Results will be presented when available. 
 
 
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A simulation model of morphological, vegetation and sediment changes in ephemeral streams.

Degradación ecológica y cambio cultural durante los últimos cuatro mil años en el sureste ibérico semiárido.

Differences in hillslope runoff and sediment transport rates within two semi-arid catchments in southeast Spain.

El Sistema Hidrografico del Guadalentin. Cuadernos Technicos 6, Consejeria de Politica Territorial, Obras Publicas y Medio Ambiente de la Region de Murcia.

Geomorphological impacts of a flood event on ephemeral channels in SE Spain.

Oligocene to middle Miocene basin development in the Eastern Betic Cordilleras, SE Spain (Velez Rubio Corridor – Espuña): reflections of West Mediterranean platetectonic reorganizations.

Palaeoflood and floodplain records from Spain: Evidence for long-term climate variability and environmental changes.

Policy impact on desertification: stakeholders’ perceptions in southeast Spain.

Riesgos de inundaciones: tendencias históricas y perspectivas de acuerdo con el cambio climatico.

Scale dependent thresholds in hydrological and erosion response of a semi-arid catchment in southeast Spain.

Spatial patterns of land degradation and their impacts on the water balance of rainfed treecrops: A case study in South East Spain.

Subrezente Morphodynamik im Bereich der Cañada Hermosa,

The HVEE 14C system at Groningen.

The impact of rainstorms on floods in ephemeral channels in southeast Spain.

The influence of land use, soils and topography on the delivery of hillslope runoff to channels

Thresholds for gully initiation and sedimentation

Controls on Late Quaternary landscape development in the Upper Guadalentín Basin, Murcia, SE Spain

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