C. Zazo

Fault-generated mountain fronts in southeast Spain: geomorphologic assessment of tectonic and seismic activity

Abstract Tectonic activity of SE Spain is evaluated through the application of a general morphometric analysis over 17 different mountain fronts. The selected fronts are distributed along the two most prominent crustal-scale structures of the Mediterranean sector of Spain: The Eastern Betic Shear Zone (EBSZ) and the Valencia Trough. Geomorphic indexes used in this study are Mountain-front sinuosity index (Smf) and Valley floor/width ratio (Vf). This work is largely based on the Smf/Vf regression analysis of the studied fronts together with previous available data from SW USA. The development of mountain fronts in both different lithologies and tectonic contexts enabled characteristic morphometric signatures for different activity scenarios (tectonic activity classes) to be obtained. This study thus indicates that variations of mountain front geomorphology triggered by different styles of faulting can be detected by morphometric analysis. It is demonstrated that discrete uplift rates of 0.15–0.08 m/ka are sufficient to keep relatively low Smf values down to 1.4 in Active fronts (Class 1). Taking into account the reported uplift rates and preliminary palaeoseismic data for some of the Class 1 studied fronts, recurrence periods for surface rupture events can be theoretically bracketed for SE Spain. Recurrence periods for Class 1 fronts could theoretically range between 10,000 and 12,500 years for maximum slip conditions, and 1750 and 2600 years for minimum slip conditions. Inactive fronts (Class 3) develop under uplift rates down to 0.03 m/ka, and tested recurrence intervals for rupture events range between 25,000 and 50,000 years. Class 2 fronts of intermediate characteristics and activity display uplift rates between 0.07 and 0.03 m/ka.

Landscape response to strike-slip faulting linked to collisional settings: quaternary tectonics and basin formation in the Eastern Betics, southeastern Spain

Abstract Neotectonic behaviour of the Eastern Betics (southeastern Spain) has been controlled by the presence of a large, left-lateral shear zone. This is an intraplate transcurrent zone, probably decoupled by a mid-crustal detachment horizon. The morphological expression of this crustal structure is a sigmoidal corridor in which the main Quaternary basins are located. Three types of morphostructural domains can be distinguished in the sigmoidal corridor: the central segment, and the northern and southern terminal splays. The central segment is characterized by wrench tectonics, whilst the southern and northern terminal splays are controlled by transtensional and transpressional tectonics, respectively. The Quaternary morphostructural pattern is only the more recent picture of the tectonic processes that have controlled the late orogenic evolution of the Eastern Betics: the indentation of the Aguilas arc, accompanied by thin-skinned thrusting and tectonic escape in its easternmost sector; and extensional collapse, accompanied by thin-skinned stretching, in its westernmost sector.

Particle size characterisation of Holocene back-barrier sequences from North Atlantic coasts (SW Spain and SE England)

Abstract In this paper, we present the results of bivariate plots of grain size parameters (mean against sorting) in the reconstruction of Holocene environmental change in coastal environments where barrier formation has had an important control on sedimentation. Sites on the North Atlantic coast with differing histories of climate, sediment flux, sea-level change and barrier integrity are investigated to determine the general efficacy of this bivariate parameter model in distinguishing between open- and closed-basin conditions, and in reviewing the significance of aperiodic high-energy geomorphic events in controlling late stage back-barrier sedimentation.

Neotectonics and Plio-Quaternary landscape development within the eastern Huércal-Overa Basin (Betic Cordilleras, southeast Spain)

Abstract The Huercal-Overa Basin is one of a series of Neogene sedimentary basins located within the Betic Cordillera of southeast Spain. Its geological and geomorphological history has been controlled by tectonic activity culminating in basin inversion during the Plio-Quaternary. Deformation of the Huercal-Overa Basin is associated with left-lateral strike-slip faulting in relation to its position within the Trans-Alboran shear zone. In this paper, we focus upon the eastern portion of the Huercal-Overa Basin and make the first attempt to reconstruct the long-term landscape development during the Plio-Quaternary. This is done through integration of geological and geomorphological data obtained through field observations and GIS and remote sensing techniques. In particular, this paper provides a case study that contributes to the understanding of landscape development within tectonically active shear zones. Within the eastern part of the Huercal-Overa Basin, the main tectonic activity is associated with the left-lateral strike-slip Lorca-Alhama fault (oriented NE–SW). During the Late Pliocene and Early Pleistocene, the interaction of this fault with older Miocene ENE–WSW to E–W orientated structures formed a subsiding area with pull-apart basin characteristics termed the Cubeta del Saltador. Subsidence within the Cubeta del Saltador enabled sedimentary infilling by braided rivers with sediment being derived from the Sierra de Las Estancias to the north and the Sierra de Almagro to the south. Sedimentary deformation has resulted in the development of a series of progressive unconformities, angular unconformities and faulting within the alluvial sediments. Towards the end of this stage of landscape development, an increase in tectonic activity resulted in the creation of elevated tectonic highs in the north (Alto de la Garita del Diablo) and east (Loma de Garcia) of the Cubeta del Saltador. From the middle Pleistocene onwards, a progressive decrease in tectonic activity is recorded. Alluvial sediments infilled the Cubeta del Saltador. These were dominated by braided river sediments that formed part of a fan-shaped alluvial distributary system derived from the Sierra de las Estancias to the north. In contrast, smaller debris-flow-dominated alluvial fans were derived from the Sierra de Almagro along the southern margin. Currently, the study area presents an asymmetric configuration, reflecting the different topographic characteristics of the northern and southern limiting mountain fronts.

CARBON STORAGE AND CONTINENTAL LAND SURFACE CHANGE SINCE THE LAST GLACIAL MAXIMUM

Abstract Estimates of the storage and flux of shelf carbon in vegetation, soils, carbonates, and organic matter during the period of the marine transgression since the Last Glacial Maximum (LGM) 18 ka are presented. Whereas at present each square metre of land on the planet carries about 10.65 kg of carbon in vegetation and soils, during the LGM most areas of exposed continental shelf carried relatively little carbon, probably about 5.86 kg C m −2 , but this increased to a maximum density of 15.49 kg C m −2 after 10 ka when conditions generally favoured peat deposition and forest development. In the ensuing sea level rise up until mid-Holocene time this large store of carbon was displaced. Assuming an average value of 10.65 kg m −2 carbon (combining the land lost to sea-level rise before and after 13 ka), a transgression covering 15–23×10 12 m 2 would mean that 160 to 245 Gigatons of Carbon (1 Gt=10 12 kg) were lost from the terrestrial system at the same time that the remainder of the terrestrial biosphere was still taking up organic carbon. This additional and opposite flux from the land system must be taken into account when considering changes in the global carbon cycle and CO 2 fluxes. Moreover, it complicates the interpretation of the ocean carbon isotope record.

Dominant soil map in ‘Las Batuecas-Sierra De Francia’ and ‘Quilamas’ nature parks (Central System, Salamanca, Spain)

To correctly and rationally plan human activities in fragile conservation areas, an exhaustive study of the soil-forming factors (climate, lithology, geomorphology, topography, hydrology and vegetation) including the soil relationships, should be conducted. We analysed the geospatial distributions of different soil types in the ‘Las Batuecas – Sierra de Francia’ and ‘Quilamas’ natural areas using soil sampling and laboratory analyses to determine the soil associations and dominant soil types and so create toposequence maps. These maps were used to assess potential soil uses and resources and to identify environmental problems from natural and/or anthropogenic causes. The GIS techniques used in this study provide georeferenced maps of forming factors and soil distribution that can be used to create databases that include fact sheets and photographs of the soil profiles. This soil information was exported in ‘kmz’ format to geospatially visualise the different soil units in 3D virtual tours using the Google Earth platform. This method of soil mapping allows a multidisciplinary approach that utilises other thematic layers and facilitates decision-making processes by the managers and directors of the natural areas studied in this work.

Augmented Reality in a Hiking Tour of the Miocene Geoheritage of the Central Algarve Cliffs (Portugal)

Eight sites with geological (including palaeontological and geomorphological) interest (geosites) representative of the Lower and Middle Miocene carbonate deposits near Albufeira in central Algarve (southern Portugal) have been selected based on our extended working experience. The sites can be visited by hiking in a 1-day field trip. A virtual 3D tour of the georeferenced sites was produced using augmented reality technique and geoinformatic tools which integrate thematic digital layers such as geological maps and orthophotos. Every stop in the tour includes descriptive and graphic elements that can be viewed in free virtual globes (e.g. Google Earth) combined with diagrams, photographs and information sheets that quantitatively assess the cultural-touristic, educational and scientific value of the geosites. A virtual flight itinerary compatible with video formats in the new free technologies (smartphones, tablets and iPads) is also presented.

Geomorphology applied to landscape analysis for planning and management of natural spaces. Case study: Las Batuecas-S. de Francia and Quilamas natural parks, (Salamanca, Spain)

Geomorphology is fundamental to landscape analysis, as it represents the main parameter that determines the land spatial configuration and facilitates reliefs classification. The goal of this article is the elaboration of thematic maps that enable the determination of different landscape units and elaboration of quality and vulnerability synthetic maps for landscape fragility assessment prior to planning human activities. For two natural spaces, the final synthetic maps were created with direct (visual-perceptual features) and indirect (cartographic models and 3D simulations) methods from thematic maps with GIS technique. This enabled the creation of intrinsic and extrinsic landscape quality maps showing sectors needing most preservation, as well as intrinsic and extrinsic landscape fragility maps (environment response capacity or vulnerability towards human actions). The resulting map shows absorption capacity for areas of maximum and/or minimum human intervention. Sectors of high absorption capacity (minimum need for preservation) are found where the incidence of human intervention is minimum: escarpment bottoms, fitted rivers, sinuous high lands with thick vegetation coverage and valley interiors, or those areas with high landscape quality, low fragility and high absorption capacity, whose average values are found across lower hillsides of some valleys, and sectors with low absorption capacity (areas needing most preservation) found mainly in the inner parts of natural spaces: peaks and upper hillsides, synclines flanks and scattered areas. For the integral analysis of landscape, a mapping methodology has been set. It comprises a valid criterion for rational and sustainable planning, management and protection of natural spaces.

Soil map and 3D virtual tour using a database of soil-forming factors

Soils are non-renewable resources and therefore must be conserved, particularly in protected natural areas. Correct and rational planning of human activities in fragile conservation landscapes should be based on detailed studies of soil-forming factors, such as climate, geology (lithology and surficial deposits), geomorphology (topography, morphology, slope and hydrology), biology (vegetation and human activity) and time and their relationships with the landscape and landforms. This study analyses the geospatial distribution of different soil units in the natural areas of “Las Batuecas-Sierra de Francia” and “Quilamas” and is based on a soil sampling field programme and textural analyses that resulted in soil association maps, dominant soil maps and toposequences that could be extrapolated to natural resource and environmental problems (natural and/or human). In this study, a set of GIS-based digital maps was developed to illustrate the physical attributes of these natural areas. In particular, georeferencing of the various soil-forming factors was used to generate a specific soil map for each natural area and to create a geospatial database, including fact sheets and photographs, of characteristic soil profiles. This soil information was converted into the “kmz” format to geospatially visualise the various soil units in 3D virtual tours using viewers, such as Google Earth, to obtain information regarding the spatial referencing and elevation of the area, interact with the 3D modelling of the tour in Google Earth, overlay the soil map on the orthophoto, activate or deactivate the visible layers, modify the spatial resolution of every point by zooming in or out and obtain the numeric and graphical information for every stop. This soil map can be used in multidisciplinary approaches by adding other thematic layers: lithology, geomorphology, topography, morphology, slope, hydrology, vegetation, et cetera, which would facilitate decision-making by managers and directors of nature areas/parks.

Ground movement risk in 'Las Batuecas-Sierra de Francia' and 'Quilamas' nature parks (central system, Salamanca, Spain)

Ground movements constitute active processes that modify the disposition and morphology of the earths surface. This work establishes a cartography procedure to obtain a ground movement risk map at a 1:50,000 scale. Such a map would be useful for establishing mitigation measures for land use planning and management in natural spaces, using Geographic Information Systems (GIS). A number of steps are taken to produce the map in GIS. First, a susceptibility map is created by considering passive or conditioning factors, which depend on the nature, structure and morphology of the ground. Second, a hazard map is created by considering active or trigger factors, which cause instabilities within hillsides and determine the magnitude and speed of their movements. Finally, the ground movements risk map is obtained by combining the susceptibility and hazard maps with risk and vulnerability map (degree of potential damage) and risk exposure map (estimate of damage, human casualty and economic loss). The resulting ground movements risk map shows very high risk at the foot of escarpments and abrupt reliefs where urban areas, fractures and/or roads are present. High risk prevails in the geomorphologic domains of fluvial incisions, where the slopes are high, as well as in areas with escarped hillsides. Medium-risk areas are distributed around the marked reliefs, forming zones of filling and slightly flat surfaces. Low-risk areas appear in topographically flat areas, since they are domains of terraces, pediments or degraded surfaces. Very scattered and less-extended areas present very low risk.