Publication: Morfología Fluvial.-Controls on Late Quaternary Landscape development in the Upper Guadalentin Basin, Murcia, SE Spain
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Authors
Baartman, J.E.M. ; Veldkamp, A.
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Universidad de Murcia
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Publisher
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info:eu-repo/semantics/other
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Abstract
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.
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