Baza Basin Research Articles

Plio-Pleistocene hydrothermal events of the Baza Basin (Betic Cordillera, SE Spain) and their paleoecological implications

AbstractThe Lower Pliocene to upper Middle Pleistocene continental sedimentary infillings of the Baza Basin (Guadix-Baza Depression, SE Spain) are worldwide unique by their high stratigraphic completeness and exceptional preservation of their fossil record of terrestrial vertebrates. These sediments were deposited in fluvio-lacustrine environments and preserve huge assemblages of large mammals, including the oldest evidence of hominin presence in Western Europe at the late Lower Pleistocene sites of Barranco León and Fuente Nueva-3, dated to ∼1.4 Ma. Since latest Miocene times, the basin was subject to intense tectonic activity, showing sedimentary deposits originated from ancient hot springs. These hot springs were developed in a spatio-temporal network related to tectonic fractures, showing a higher concentration in the Orce sub-basin during Late Pliocene to Holocene times. Compositional analyses of cherts and other facies associated with these hot springs show geochemical and mineralogical markers linked to hydrothermal scenarios. The contribution of hot springs in the Baza Basin resulted in rich and productive biotopes, which supported a high diversity and biomass of terrestrial mammals. Similar geological, hydrochemical and ecological environments are found along hotspot lines in East Africa, the Levantine Corridor and the circum-Mediterranean realm. We hypothesize here that the presence of these hot springs corridors favored the dispersal of hominins and other large mammals during the Plio-Pleistocene, which led to the first hominin arrival in Europe.

Hominins and carnivores in the Early Pleistocene site of Barranco León (Orce, Baza Basin, SE Spain): Comment on Courtenay et al. (2023)

This work investigates questions regarding obsidian circulation among the late populations (since ca. 1100 BP) of Antofagasta de Sierra (Catamarca Province, Argentinean Southern Puna Plateau). By means of geochemical provenance studies conducted on obsidian artefacts, the sources of obsidian that these groups accessed have been identified. The samples considered in this study were collected at three radiocarbon-dated sites in the micro-region: La Alumbrera, Bajo del Coypar II and Campo Cortaderas.The results obtained are compared with those available for other contemporary sites and Formative contexts (ca. 3000–1100 BP) within the area of study. A preliminary discussion is presented on the basis of the environmental, political and social tendencies that characterized the times after ca. 1100 BP at the micro-region and south-central Andes.

Holocene molluscan successions from southeastern Spain (Galera, Andalusia): a palaeoenvironmental framework and a palaeobiogeographic resource of the Granada UNESCO Geopark

ABSTRACTIn Spain, Holocene deposits are widespread, and although they have been extensively investigated by quaternarists for several decades, their malacological content has remained scarcely studied. In the framework of a German–French–Spanish collaboration, alluvial and tufa sequences in the Baza Basin, Andalusia, Spain are analysed with a multidisciplinary approach, including the analysis of the molluscan successions. Holocene fossil molluscs of the studied sequences reveal a rich assemblage of 53 species, among which 33 are terrestrial. Between 10,000 and 9,000 cal. yr BP, the Galera succession indicates strong river dynamics that prevented the establishment of adjacent terrestrial habitats. The Early to Middle Holocene transition reflects the continuity of humid environments. The Middle Holocene fauna reveals a decrease in humidity accompanied by slight evidence of drier habitats in the near periphery of the floodplain/tufa deposits from 5,900 cal. yr BP onwards. Late Holocene deposits (around 3,000 to 300 cal. yr BP) point to dry and open biotopes indicated by the appearance of xero-resistant and mesophilous gastropods. The palaeoenvironmental reconstruction inferred from the malacocenoses allows discussing local to regional responses of the malacofauna to environmental changes and is consistent with past regional environmental and climatic trends identified in southeastern Spain. The fossil record at Galera offers new evidence to question and clarify the modern range of endemic taxa whose distributions are fragmented. By following a ‘conservation paleobiology’ approach, the analysis of the mollusc fossil record at Galera provides (1) baselines to determine the natural variability of ecosystems and their response to environmental changes, (2) data to discuss and clarify species distribution evolution and (3) arguments to support conservation priorities.

Imaging extensional fault systems using deep electrical resistivity tomography: A case study of the Baza fault, Betic Cordillera, Spain

Seismic hazard assessment of present-day tectonic faults may be improved by studying their structure and kinematics. These features have been mainly determined by surface geological studies of exposed fault traces, structural lateral segmentation or paleoseismic trenches. All these approaches rely mainly on two-dimensional analyses of surface outcrops, while knowledge of the faults at depth remain largely inaccessible. To improve on such limitations, geophysical methods can be applied to establish detailed information on fault morphology and segmentation at depth. This work analyzes new results of a deep electrical resistivity tomography survey acquired across the Baza Fault, a present-day tectonic fault that controls the geometry of the Neogene intra-mountainous Baza Basin (Betic Cordillera, Spain). Interpretation of our preferred resistivity model reveals its detailed structure down to approximately 1000 m depth. The survey shows a minimum 2 km wide complex normal fault system, with rotational tilting blocks bounded by potentially listric normal faults. This study presents subsurface evidence of the Baza fault (F3), coincident the main topographic scarps. However, the geophysical model and geomorphic evidence also support a fault branch (F1) that might be an additional active seismogenic source. The geophysical survey technique presented in this study provides essential data to improve assessment of the seismogenic potential of the Baza Fault.

D\xe9j\xe0 vu: a reappraisal of the taphonomy of quarry VM4 of the Early Pleistocene site of Venta Micena (Baza Basin, SE Spain)

Venta Micena, an Early Pleistocene site of the Baza Basin (SE Spain), preserves a rich and diverse assemblage of large mammals. VM3, the main excavation quarry of the site, has been interpreted as a den of the giant hyaena Pachycrocuta brevirostris in the plain that surrounded the Baza palaeolake. Taphonomic analysis of VM3 has shown that the hyaenas scavenged the prey previously hunted by the hypercarnivores, transported their remains to the communal den, and consumed the skeletal parts according to their marrow contents and mineral density. In a recent paper (Luzón et al. in Sci Rep 11:13977, https://doi.org/10.1038/s41598-021-93261-1, 2021), a small sample of remains unearthed from VM4, an excavation quarry ~ 350 m distant from VM3, is analysed. The authors indicate several differences in the taphonomic features of this assemblage with VM3, and even suggest that a different carnivore could have been the agent involved in the bone accumulation process. Here, we make a comparative analysis of both quarries and analyse more skeletal remains from VM4. Our results indicate that the assemblages are broadly similar in composition, except for slight differences in the frequency of megaherbivores, carnivores and equids according to NISP values (but not to MNI counts), the degree of bone weathering, and the intensity of bone processing by the hyaenas. Given that VM4 and VM3 were not coeval denning areas of P. brevirostris, these differences suggest that during the years when the skeletal remains were accumulated by the hyaenas at VM3, the rise of the water table of the Baza palaeolake that capped with limestone the bones was delayed compared to VM4, which resulted in their more in-depth consumption by the hyaenas.

Geochemical and sedimentary constraints on the formation of the Venta Micena early Pleistocene site (Guadix-Baza Basin, Spain)

Despite the paleontological relevance of the terrestrial Early Pleistocene Venta Micena bonebed (Baza Basin, Spain), it lacks a comprehensive geochemical/sedimentological study. Here, we demonstrate that the 1.5-m-thick Venta Micena limestone formed in a relatively small freshwater wetland/pond located at the periphery of the large saline Baza paleolake. Two microfacies are observed, with high and low contents of invertebrate fossils, and which originated in the centre and margin of the wetland, respectively. X-ray diffraction (XRD) mineralogy and paleohydrological characterization based on ostracod and bulk-rock geochemistry (δ13C and δ18O) indicate that the limestone reflects a general lowstand of the Baza lake, permitting the differentiation of freshwater wetlands that were fed by adjacent sources. Conversely, during highstands, the Baza lake flooded the Venta Micena area and the freshwater fauna was replaced by a saline one. Bulk-rock isotopic data indicate that the lower interval C1 of the limestone (bone-rich in marginal settings) displays general negative values, while the upper interval C2 (bone free) displays less negative values. The bones of predated mammals accumulated in the marginal areas, which were flooded and buried by recurring water-table fluctuations. Lake dynamics played a critical role in bone accumulation, which was previously considered as representing a hyena den.

Holocene landscape evolution in the Baza Basin (SE-Spain) as indicated by fluvial dynamics of the Galera River

The concrete relationships between fluvial system behavior and potential influencing factors that are, among others, climate forcing, tectonics, and human activity are a key issue in geomorphological research. In this regard, especially the Iberian Peninsula is an area of great interest because its landscapes are highly sensitive towards climate changes and anthropogenic impact. Nowadays, the Iberian Peninsula reveals a strongly heterogeneous and spatially fragmented climate configuration. This should give rise to disparate behavior of fluvial geomorphic systems considering that climate is generally assumed the most important trigger of fluvial dynamics. In fact, river systems located in more humid and more arid regions in Iberia often reveal deviating patterns of Holocene floodplain evolution. This raises the question of whether these patterns were actually caused by a different climate history or if, alternatively, other factors might have been responsible. In this study, we investigated the Holocene floodplain evolution of the Galera River that is located in the upland of Eastern Andalucía (SE-Spain) named Baza Basin. A combination of detailed stratigraphic profile logging and close-meshed radiocarbon dating revealed that Holocene river dynamics generally followed the regional climatic development, which proves the Galera floodplain record to be a valuable archive of Holocene landscape evolution. However, we demonstrate that fluvial dynamics of the Galera system are hardly comparable to other river systems in Iberia even if the climate evolution was not so different. Our results suggest that in river systems with different basic conditions and catchment-specific configurations, similar climatic influences may lead to deviating fluvial process regimes (divergence phenomenon) because of substantial imprints of other parameters such as geological substratum, relief composition, tectonics, or human interventions.

A new species of dog from the Early Pleistocene site of Venta Micena (Orce, Baza Basin, Spain)

The site of Venta Micena (Orce, Spain), c. 1.6 Ma, preserves one the best paleontological records of the early Pleistocene large mammals fauna in Europe. Here we describe the specimens of the genus Canis Linnaeus, 1758 in the context of the late Villafranchian and Epivillafranchian fossil dogs from Eurasia. Anatomical and metric data suggest that the Venta Micena Canis form differs from the classical records of Canis etruscus Forsyth Major, 1877 and Canis arnensis Del Campana, 1913, and that it forms part of the younger Canis mosbachensis Soergel (1925) lineage, also recorded in two slightly younger sites of the Orce site complex, Barranco León and Fuente Nueva-3, dated to c. 1.4 Ma. The anatomy of the Venta Micena fossil material shows features that resemble the Canis forms from the Caucasian site of Dmanisi, dated to 1.8 Ma, and Canis ex gr. C. mosbachensis. Nevertheless, dental peculiarities support the creation of a new chrono-species, Canis orcensis n. sp., from the town of Orce. Morphological and paleoecological data suggest that this species probably consumed more vertebrate flesh than other similar sized early Pleistocene canids (i.e., a trend to hypercarnivory), which had more omnivorous dietary habits.

FIRST REVIEW OF THE LYNCODONTINI MATERIAL (MUSTELIDAE, CARNIVORA, MAMMALIA) FROM THE LOWER PLEISTOCENE ARCHAEO-PALAEONTOLOGICAL SITES OF ORCE (SOUTHEASTERN SPAIN)

Two archaeo-palaeontological Lower Pleistocene sites of Orce (Baza Basin, SE Spain), Fuente Nueva 3 (1.3 Ma) and Barranco Leon (1.4 Ma), preserve some of the earliest evidences of human presence in the European continent. During the 2013 field season, a small Lyncodontini mustelid mandible was found at Fuente Nueva-3. This finding was accompanied by a lower canine (c1), also from the same site, and a lower fourth premolar (p4) from Barranco Leon. Here, we report on the morphological and biometrical study of these materials, in comparison to other Eurasian Pliocene-Pleistocene species of the tribe Lyncodontini. The analyses revealed an affinity between the taxon from Fuente Nueva-3 and Barranco Leon with the small-sized European species Martellictis ardea (Gervais, 1848-1852), allowing us to ascribe the described material to the latter species. The presence of M. ardea in the sites of Orce is the southernmost occurrence of the species in the Iberian Peninsula and an important finding in the scarce fossil record of Lyncodontini in Europe.

A long Early Pleistocene pollen record from Baza Basin (SE Spain): Major contributions to the palaeoclimate and palaeovegetation of Southern Europe

The basin of Baza is located in the central area of the Betic Range (SE Spain) with a catchment area of over 4000 km2. It contains a continuous and well preserved lacustrine sedimentary record from the Late Miocene to the Middle Pleistocene. The basin encloses numerous Miocene to Pleistocene mammal fossil sites that include some of the oldest hominin occurrences in Western Europe, found at the Orce sites. The present work features the palynological analysis of sediment samples obtained from the Palominas drill core. The Palominas core cuts thorough fine grained sedimentary units located in the depocenter of the basin, which contain well preserved pollen grains. The palynoflora found in the core is rich in herbaceous pollen, as well as Quercus and Pinus, with other tree taxa appearing in lesser quantities. Spectral analysis reveals strong climatically controlled vegetation successions. The application of the Biomization method on these assemblages allows for a reconstruction of the biome succession. The Early Pleistocene landscape was dominated by a sequence of steppe, evergreen-bushland and mixed-forest biomes. The Coexistence Approach method shows that SE Spain experienced humid periods, during which precipitations were significantly higher than during the modern climate. These humid phases are correlated with warm interglacial periods which featured the development of open forests. Dryer phases and fully open environments are correlated with colder glacial periods. Based on the palynoflora a Calabrian age is suggested for the Palominas core. The flora and climatic patterns identified in Baza are similar to the ones identified in Calabrian records of Southern Italy and Greece.

The earliest cut marks of Europe: a discussion on hominin subsistence patterns in the Orce sites (Baza basin, SE Spain)

Ancient evidence of human presence in Europe is recorded in several Early Pleistocene archaeopalaeontological sites from Spain, France and Italy. This is the case of Barranco León (BL) and Fuente Nueva-3 (FN-3), two localities placed near the town of Orce (depression of Baza and Guadix, SE Spain) and dated to ~1.4 Ma. At these sites, huge assemblages of Oldowan tools and evidence of defleshing, butchering and marrow processing of large mammal bones have been recovered together with a deciduous tooth of Homo sp. in the case of level BL-D. In this study, we: (i) describe in detail the anthropic marks found in the bone assemblages from these sites; (ii) analyse patterns of defleshment, butchery and marrow processing, based on the modifications identified in the cortical surface of the fossils; and (iii) discuss on the subsistence strategies of the first hominins that inhabited the European subcontinent during Early Pleistocene times.

The mammoth from the archaeo-paleontological site of Huéscar-1: A tile in the puzzling question of the replacement of Mammuthus meridionalis by Mammuthus trogontherii in the late Early Pleistocene of Europe

The site of Huéscar-1 (Baza basin, Granada, Spain) yielded an interesting paleontological record close in age to the Early-Middle Pleistocene boundary. In 2003 two lithic artifacts were found, confirming the human presence at this site. The faunal assemblage preserves few marsh turtle remains, a number of avian species, and small and large mammals, including some elephant remains believed in the past to record the oldest appearance in Europe of Palaeoloxodon antiquus. They actually belong to the genus Mammuthus, although the identification (i.e., Mammuthus meridionalis or Mammuthus trogontherii) has been questioned. The aim of this research is two folded: (1) to provide a new description of Huéscar-1 remains, which can confidently be attributed to the southern mammoth, thus representing one among the last populations of M. meridionalis recorded in Europe; and (2) to briefly discuss open questions about time and mode of the replacement of M. meridionalis by M. trogontherii by the end of the Early Pleistocene.

The late Neogene rodent succession of the Guadix–Baza Basin (south‐eastern Spain) and its magnetostratigraphic correlation

AbstractIn this paper a magnetostratigraphically calibrated biozonation of the Miocene–Pliocene continental record of the Guadix–Baza Basin (south‐eastern Spain) is presented. This biozonation is based on a rodent succession which ranges from the latest Miocene (c. 6 Ma) to the latest Pliocene (c. 2.6 Ma). A total of nine biozones have been defined for the late Miocene and Pliocene, all of them based on the range or concurrent‐range of rodent species: Apodemus gudrunae – Apocricetus alberti Zone, Apocricetus barrierei Zone, Paraethomys aff. abaigari Zone, Trilophomys Zone, Mimomys davakosi Zone, Dolomys adroveri Zone, Mimomys hassiacus Zone, Mimomys polonicus Zone and Kislangia ischus Zone. A magnetobiostratigraphical correlation has been established between these biozones and the standard ATNTS scale, on the basis of the palaeomagnetic analysis carried out on the sections of Negratín, Botardo‐1 and Gorafe. The correlation has been completed with previous palaeomagnetic analysis in the sections of Galera and Zújar. The magnetobiostratigraphical correlation here established indicates a late Messinian age for the Apodemus gudrunae – Apocricetus alberti Zone, a Zanclean age for the Apocricetus barrierei, Paraethomys aff. abaigari, Trilophomys and Mimomys davakosi zones and a Piazencian age for the Mimomys hassiacus, Mimomys polonicus and Kislangia ischus zones. The Dolomys adroveri Zone is mostly Zanclean in age, but its uppermost part belongs to the Piazencian. Therefore, unit MN13 is correlated with the late Messinian, MN14 is correlated with the early Zanclean, most of MN15 is correlated with the late Zanclean, while the uppermost part of MN15 and MN16 are correlated with the Piazencian.

New magnetostratigraphic evidence for the age of Acheulean tools at the archaeo-palaeontological site \u201cSolana del Zamborino\u201d (Guadix \u2013 Baza Basin, S Spain)

The sedimentary record in the Guadix-Baza Basin (southern Spain) has proved to be a great source of information for the Miocene through the Pleistocene periods, due to the abundant faunal remains preserved, in some cases associated with lithic tools. The Solana del Zamborino (SZ) section has been the subject of controversy ever since a magnetostratigraphic analysis resulted in an age of 750–770 Kyr for Acheulean tools, a chronology significantly older than the ~600 Kyr established chronology for the first Acheulean record in Europe. Although recent findings at the “Barranc de la Boella” site (north-east of the Iberian Peninsula) seem to indicate that an earlier introduction of such technique in Europe around 0.96–0.781 Ma is possible, the precise age of the classical site at SZ is still controversial. The aim of this paper is to constrain the chronology of the site by developing a longer magnetostratigraphic record. For this purpose, we carried out an exhaustive sampling in a new succession at SZ. Our results provide a ~65 m magnetostratigraphic record in which 4 magnetozones of normal polarity are found. Our new magnetostratigraphic data suggest an age range between 300–480 Kyr for the lithic tools, closer to the age of traditional Acheulean sites in Europe.

Orcemys, a new genus of arvicolid rodent from the early Pleistocene of the Guadix–Baza Basin, southern Spain

A new arhizodont arvicoline rodent is described from early Pleistocene deposits of Barranco de los Conejos and Barranco del Paso in the Guadix–Baza Basin of southern Spain. The molars of Orcemys appear to represent a paedomorphic origination from a large rhizodont Mimomys. A few dental characters of Orcemys are superficially similar to those of the lagurines, but the presence of sparse cementum in reentrant folds and a Mimomys-kante formed opposite T5 on the first lower molar clearly identify Orcemys as an arvicoline. The character mosaic of Orcemys is unique among large early Pleistocene voles and the dentition of a potential ancestor probably resembled that of Mimomys medasensis with a tendency towards simplification. With Tibericola vandermeuleni and Mimomys oswaldoreigi, Orcemys represents one of the earliest experiments with arhizodonty among European voles. Including Mimomys medasensis at Barranco del Paso, this set of arvicolids redefines a previously recognized early Pleistocene MmQ1 biozone in Spain.

A new Ruscinian site in Europe: Baza-1 (Baza basin, Andalusia, Spain)

The Guadix–Baza depression (southeastern Spain) preserves one of the best continental Plio-Pleistocene records of the European continent. The new site, Baza-1, is the first Ruscinian locality with fauna of large vertebrates known in the basin. During the summer seasons of 2001, 2002, 2015 and 2016, systematic excavations were undertaken in the site over an area of 25m2, which provided>400 fossil remains of Ruscinian mammals. The faunal assemblage is diverse, comprising 17 genera. Rodentia are represented by Ruscinomys sp., Apocricetus barrierei, Debruijnimys julii, Apodemus gorafensis, Castillomys gracilis, Occitanomys cf. brailloni, Paraethomys meini, Paraethomys aff. abaigari, Stephanomys cordii, Trilophomys cf. castroi and Eliomys aff. intermedius. Large mammals are represented by two proboscideans, Anancus arvernensis and Mammut borsoni, the rhino Stephanorhinus sp. cf. S. jeanvireti, the equid cf. Hipparion sp., two bovids, a large sized Alephis sp. and a small-to-middle sized Bovidae indet. (cf. Antilope sp.), and a middle sized deer, Cervinae indet. This record is completed by the presence of a chelonid, Testudinae indet. Biostratigraphic data from micro and macromammals suggest an age for the assemblage between 4 and 4.5Ma.

Resource availability and competition intensity in the carnivore guild of the Early Pleistocene site of Venta Micena (Orce, Baza Basin, SE Spain)

With an age of ∼1.6–1.5 Ma, the Early Pleistocene site of Venta Micena (Orce, Baza Basin, SE Spain) has provided the large mammals assemblage of Late Villafranchian age with higher preservational completeness in Western Europe and offers a unique opportunity to analyze the food webs of the mammalian paleocommunity before the first human arrival in this continent. Taphonomic analysis of the fossil assemblage has shown evidence of carnivore involvement, particularly hyenas, in the bone accumulating process. In this study we use a mathematical approach based on Leslie matrices to quantify the biomass of ungulates available to the members of the carnivore guild as well as the pattern of resource partitioning and competition intensity among them. The results obtained show that although the biomass of primary consumers available to the secondary consumers was lower than the value expected under optimal conditions, more than half the individuals and biomass of carnivores expected would be reached, which allowed a viable ecosystem in Venta Micena. In fact, the biomass available for the members of the carnivore guild is 25–30% greater than the estimates obtained for two nearby sites, Barranco León-D and Fuente Nueva-3, which are somewhat younger (∼1.4 Ma) and preserve the oldest evidence on human presence in this region. Given that the competition intensity estimated in the carnivore guild of Venta Micena was lower than in the latter sites, this suggests that the timing of the first human dispersal in Western Europe was probably not a matter of ecological opportunity.

Architecture and tectono-stratigraphic evolution of the intramontane Baza Basin (Bétics, SE-Spain): Constraints from seismic imaging

The Baza basin is a large Neogene intramontane basin in the Bétic Cordillera of southern Spain that formed during the Tortonian (late Miocene). The Bétic Cordillera was produced by NW–SE oblique convergence between the Eurasian and African Plates. Three seismic reflection lines (each 18km long; vibroseis method) were acquired across the Baza basin to reveal the architecture of the sedimentary infill and faulting during basin formation. We applied rather conventional CDP data processing followed by first arrival P-wave tomography to provide complementary structural information and establish velocity models for the post-stack migration. These images show a highly asymmetric structure for the Basin with sediments thickening westward, reaching a maximum observed thickness of >2200m near the governing Baza Fault zone (BFZ). Three major seismic units (including several subunits) on top of the acoustic basement could be identified. We use stratigraphic information from the uplifted block of the BFZ and other outcrops at the basin edges together with available information from neighboring Bétic basins to tentatively correlate the seismic units to the known stratigraphy in the area. Until new drilling or surface outcrop data is not available, this interpretation is preliminary.The seismic units could be associated to Tortonian marine deposits, and latest Miocene to Pleistocene continental fluvio-lacustrine sediments. Individual strands of the BFZ truncate the basin sediments. Strong fault reflections imaged in two lines are the product of the large impedance contrast between sedimentary fill and basement. In the central part of the Basin several basement faults document strong deformation related to the early stages of basin formation. Some of these faults can be traced up to the shallowest imaged depth levels indicating activity until recent times.

On the ecological context of the earliest human settlements in Europe: Resource availability and competition intensity in the carnivore guild of Barranco León-D and Fuente Nueva-3 (Orce, Baza Basin, SE Spain)

With an age of ∼1.4 Ma, the Early Pleistocene archaeopaleontological sites of Barranco León and Fuente Nueva-3 (Orce, Baza Basin, SE Spain) provide the oldest evidence on human presence in Western Europe, including the finding of a deciduous tooth of Homo sp., huge lithic assemblages of Oldowan tradition and abundant cut-marks on large mammal bones. Here we use a mathematical approach based on Leslie matrices to quantify for the large mammal species preserved at the sites the biomass of primary consumers available, the distribution of meat resources among the secondary consumers and the competition intensity within the carnivore guild. The results obtained show a community of large mammals with a high diversity of secondary consumers that would satisfy slightly less than half of their dietary requirements under optimal ecological conditions. In the case of Homo sp., and considering that flesh resources were obtained through the scavenging of ungulate carcasses, the model indicates that the ecosystems of the basin could hold 10–14 individuals per 100 km2 during a year, a value that is close to the mean population density of recent hunter-gatherers. These density estimates decrease slightly when a mixed hunting-scavenging strategy is considered and even more in the case of a strict hunting behavior. In addition, the value of the species competition index obtained for Homo sp. is among the lowest of the carnivore guild. These results suggest that the hominin populations that inhabited Southeast Spain during the Early Pleistocene behaved more as opportunistic scavengers than as active predators.

Active shallow extension in central and eastern Betic Cordillera from CGPS data

The Betic Cordillera is an Alpine belt formed in the western Mediterranean by the westward displacement of the Alboran Domain in between the Eurasian and African convergent plates. New CGPS data from the central and eastern Betic Cordillera and its foreland—obtained mainly from the Topo-Iberia project—allowed us to precisely determine the rate of tectonic deformation. Most of the displacements of the central and eastern Betics are westward, with a variable southwestward component, in relation to the Eurasian stable plate. While in the Iberian foreland the displacements are extremely low, some deformation related to low compressional deformation occurs in the easternmost foreland basin and eastern Betic Cordillera. The displacement increases substantially southwards and westwards in relation to present-day extensional deformation. Major active discontinuities correspond to the NW–SE normal fault zones, which dip westwards; they are located in Almeria–Tabernas; Balanegra, and western Sierra de Gador; whereas the Padul fault zone located west of Sierra Nevada extends northwards to the Granada Basin. NW–SE extensional faults are also observed to the north, in the Baza Basin. Moreover, the activity of dextral faults along the Sorbas–Tabernas–Alpujarras–Guajares band, generally considered as a transfer fault zone, is evidenced by the displacement data. These results come to demonstrate the low activity or inactivity of the large northern E–W oriented folds of the central and eastern Internal Zone, such as the Sierra de Los Filabres antiform. They also point to the possible residual activity of the northern part of the NE–SW Sierra Nevada antiform, where the maximum relief of the Cordillera is found. Altogether, our data support a heterogeneous present-day westward extension that affects the upper crust of the Betic Cordillera and increases towards the thinned continental crust of the Alboran Sea and towards the west, which is compatible with roll-back subduction along the Gibraltar Arc.