Alava, Spain - Journal of Maps

Journal of Maps, 2010, 584-590
Geomorphology and prehistoric flint mining evidence in
the Sierra de Araico (Basque-Cantabrian Basin), BurgosÁlava, Spain
ALFONSO BENITO-CALVO1 , ANTONIO TARRIÑO1 , PEDRO JOSÉ LOBO2 , IOSU JUNGUITU3 and DAVID LARREINA4
1 Centro
Nacional de Investigación sobre la Evolución Humana (CENIEH), Paseo Sierra de Atapuerca s/n, 09002 Burgos, Spain;
alfonso.benito@cenieh.es.
2 Cartography
3 Geography,
4 Institute
Service, University of Basque Country (UPV), SGIKER, Vitoria, Spain.
Prehistory and Archaeology Department, University of Basque Country (UPV), Vitoria, Spain.
of Archaeology UCL, 31-34 Gordon Square, WC1H 0PY, London, UK.
Abstract
The limestones of the Sierra de Araico (Condado de Treviño, Spain), located in the Miranda-Treviño syncline (Basque-Cantabrian basin, Pyrenean Range), show silicificated nodules (flint) which have been exploited by means of non-complicated mining works (trenches and shallow pits), from Pleistocene through
to Holocene and historical times. The flint had wide geographical distribution and involved archaeological sites located across several tens of km. In this work we present a geomorphological map of this region,
mapping structural landforms marked by the limestones with flint and surficial deposits containing eroded flints related to the Ayuda and Rojo valleys. This map was produced using LiDAR data which was
used to map the mining trenches where lithic evidence - hundreds of hammer-stones, maces and cores were found.
(Received 6th July 2010; Revised 28th October 2010; Accepted 12th November 2010)
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ISSN 1744-5647
doi:10.4113/jom.2010.1147
Journal of Maps, 2010, 584-590
1.
Benito-Calvo, A. et al.
Introduction
Historic precedence for our research dates back to surveys carried out by the scholar
Deogracias Estavillo (Estavillo, 1955; 1957; 1975), who discovered a large number of settlements in the Sierra de Araico (Condado de Treviño, Burgos and Álava, North Spain),
including flint exploitations from Prehistory. He excavated more than 5,000 archaeological remains which were ascribed to Upper Palaeolithic tradition and some from the
Metal Ages. Araico industry was also associated with Neolitic culture (Maluquer de
Motes, 1957; 1966). Vallespı́ Pérez (1959a;b) analysed a significant number of open air
sites grouping them into flint workshops or quarry settlements and inhabitated settlements, beginning in Neolithic times with massive development during the Chalcolithic.
Further to these pioneer works, we initiated systematic fieldwork surveying in the 1980s
(Ortı́z et al., 1990), locating new mining evidence in silicated layers (Ferreira et al.,
1984; Ortı́z et al., 1990). These silicated layers are contained in Miocene lacustrinepalustrine formations (Aquitaniense-Burdigaliense) which outcrop in the E-W MirandaTrevio syncline (Basque-Cantabrian basin; Riba, 1956; Ramı́rez del Pozo, 1973). During
this fieldwork we detected mining works following the silicated layers.
In order to obtain an accurate distribution of the primary and secondary supply areas of
raw material we have elaborated a geomorphological map showing the structural landforms associated with the silicated limestones, the mining anthropogenic landforms and
the quaternary deposits which contained eroded flint. The landform mapping was complemented with a revision of the geological contact in order to establish the extension
of the limestone containing flint.
2.
Methods
The production of the geomorphological maps was carried out using two spatial data
sets (LiDAR DEM and aerial photographs) and fieldwork. The aerial interpretation of
small landforms and archaeological structures amid mountainous and wooded landscapes may entail substantial difficulties. Common data sets such as orthophotos, stereographic images and satellite images, only partially solve the problems of large areas
of considerable interest being obscured from view and therefore investigation. Nevertheless, LiDAR (Light Detection and Ranging) substantially mitigates these obstacles by
allowing the user to filter surface features and extract “bare earth” topography in zones
partially covered by vegetation.
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Journal of Maps, 2010, 584-590
Benito-Calvo, A. et al.
We used the LiDAR data provided by the Servicio de Cartografı́a del Gobierno Vasco,
Dpto. de Medio Ambiente y Urbanismo (Basque Country Government) to produce a
high resolution DEM at a spatial resolution 1 m, with a vertical precision of 15-20 cm.
LiDAR data was imported and processed using DielmoOpenLiDAR (DIELMO 3D S.L)
and gvSIG (Consejerı́a de Infraestructuras y Transportes de la Generalitat Valenciana),
before final map production in ESRI ArcGIS 9.3. The last phase of the work involved
relief shading in order to enhance landforms and archaeological structures. Interpretation of the LiDAR DEM was complemented by the stereoscopic photo-interpretation of
1:22,000 colour aerial photographs from the Diputación Foral de Álava. The symbology
used in the geomorphological map was based on the legend used by Geological Spanish
Survey (Martı́n-Serrano et al., 2004).
3.
Geomorphological Map Description
The Araico Range constitutes a structural relief developed in the southern flank of a
syncline with WNW-ESE direction which is incised by the Ayuda Valley from NNE to
SSW (Figure 1). Eastward, this relief is limited by a breached anticline of NW-SE direction (Moscador-Treviño) which forms a semicircular depression (Moscador-Dordóniz).
The bedrock in this area is composed of Oligocene marls and conglomerates, and a
Miocene sequence, which include two lacustrine carbonate formations scarly cemented
including flint (Cucho Limestones and Mijancas Limestones).
The northern hillside of the Araico Range presents a general slope of 8 − 12◦ and it
is characterized by chevron marks and cuestas developed in the lacustrine limestones
with flint, tilted between 19 − 30◦ (Figure 1). Among the layers two high quality layers
have been mapped (nodular flint and algae stripped flint), which were identified in
palaeolithic archaeological sites located several tens of km away (Tarriño, 2006). Limestone layers are incised by V-shaped valleys (Figure 1), characterized by narrow alluvialcolluvial bed valleys flowing towards the main valley of the Ayuda River, ultimately
forming alluvial cones. On the other hand, the southern hillside is defined by a steeper
slope (15◦ ), with valleys incised to a more gentle degree draining into the Rojo River, a
tributary of the Ayuda.
Gravitational landforms are restricted to some translational landslides and colluviums,
mainly located on the lower part of the valleys. The most significant landslide is situated near the syncline axis (Figure 1), associated with clay materials interbedded within
limestones. The translational slide, that causes the diversion of the stream, has occurred
on the right margin of a narrow valley.
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Journal of Maps, 2010, 584-590
Benito-Calvo, A. et al.
Figure 1. Sierra de Araico oblique perspective derived from LiDAR DEM and PNOA orthophoto (Centro Nacional
de Información Geográfica, CNIG). This structural relief is developed in the southern flank of a WNW-ESE syncline,
which is incised by V-shaped valleys, tributaries of the Ayuda Valley.
Asymmetrical fluvial terraces and the floodplain are developed in the lower part of the
Ayuda Valley (Figure 1). The fluvial terraces have a thickness of 2-4 m, composed of
sub-rounded and rounded gravels with sands and clays matrix. The composition of
the gravels is mainly carbonates, although it also includes flint clasts. The relative elevations of the terraces are +40, +30-36, +18-26, +16, +7-9 and +2 m above the Ayuda
River, framing the fluvial sequence between Middle Pleistocene and Holocene (Santisteban and Schulte, 2007; Benito-Calvo et al., 2008). In addition, erosive plains associated
with rock terraces without significant deposits are described. The LiDAR DEM has also
allowed the identification of elongate depressions within the floodplain that are related
to abandoned channels.
Polygenetic landforms corresponding to glacis are also represented in the Araico mountain range. These landforms have been identified in relative positions between +160 m
and +14 m above the bottom of the valleys. The glacis located at higher positions which are poorly preserved - probably correspond to the pediments associated with
Middle Miocene-Pliocene planation surfaces described in other zones of the BasqueCantabrian Range (Benito-Calvo and Pérez-González, 2007). The glacis located at lower
positions are related to the Quaternary evolution of the valleys and contain thin covers
of sediments, consisting of sub-angular clasts of limestone and flint, sands and clays.
Anthropogenic features are systematically associated with populations, roads, hydrology and farming activities, nevertheless the oldest human features frequently relate to
mining activities. The application of LiDAR DTM technology has allowed us to exten587
Journal of Maps, 2010, 584-590
Benito-Calvo, A. et al.
sively map former mining activity with the Araico mountain range displaying evidence
of many pits and trenches. The highest concentration of trenches is located on the northern flank of the mountain range to the south of the village of Araico. These mining
trenches are usually characterized by elongate morphologies which follow the limestone layers and appear to be associated with waste heaps.
4.
Conclusions
The Sierra de Araico is the homoclinal southern flank of the Miranda-Treviño syncline,
which includes two lacustrine formations with important silifications widely used during Prehistoric times, particularly specific flint layers, such us the nodular and algal
flints. The use of a LiDAR DEM and identification of lithostratigraphic formations, in
combination with detailed geomorphological mapping has allowed the development
of a map of flint resources. Lithostratigraphic units containing flint were eroded during Pleistocene times, causing the accumulation of flint in several geomorphological
contexts (alluvial-colluvial cones, colluvions, fluvial terraces or glacis). These concentrations could have been exploited from the Palaeolithic. In addition, the cementing
of the host rocks has also facilitated the creation of simple mining features, which follow the direction of strata, and have thousand of flakes, cores and chipping products
associated with Neolithic times.
Software
Original LiDAR data were imported DielmoOpenLiDAR application (DIELMO 3D S.L)
and then processed using gvSIG (Consejerı́a de Infraestructuras y Transportes de la
Generalitat Valenciana). DEM shading, digitizing and final composition of the geomorphological map was performed in ESRI ArcGIS 9.3.
Acknowledgements
This work was funded by the HAR2008-05797 Project of the Science & Innovation Department (Spanish Government); Ramon y Cajal Programme, RYC-2007-01626 of the
Science & Innovation Department (Spanish Government) also with contribution from
the European Union (FSE); PhD fellowship funded by the Direction of Scientific Po588
Journal of Maps, 2010, 584-590
Benito-Calvo, A. et al.
licy of Education, Universities and Research Department of the Basque Country Government. Cartography courtesy of the Service of Cartography and GIS of the Basque
Country University (SGIKER). LiDAR images courtesy of the Cartographic Service of
the Basque Country Government. Thanks also to the Archaeology Museum of Álava
for their help and attention.
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