Guadix Basin Research Articles

Early Pliocene Desmaninae (Mammalia, Talpidae) from Southern Spain and the Origin of the Genus Desmana

ABSTRACT Desmaninae (water-moles) are common elements in the late Miocene–Pleistocene mammal assemblages from Europe, but knowledge about this group is still scarce. Here we present the desmanines from several early Pliocene localities of the Granada Basin, southern Spain. The species Desmana marci, sp. nov. is described from the sites Calicasas-3 and 4A, characterized, among other traits, by its slightly molarized p4, enormous P2, strongly molarized P3 and P4, and very large metaconule in the M3. Desmana marci shows a typical Desmana i1, with the enamel extending further down anteriorly than posteriorly, but an Archaeodesmana-like I1, low-crowned and bilobed. Desmana marci is proposed as the oldest species of Desmana; its origin lies in Archaeodesmana baetica, and it is in turn interpreted as the ancestor of Desmana verestchagini. Besides, a desmanine of small size and ascribed to Archaeodesmana cf. getica is identified in Calicasas-5A and Purcal-13. This desmanine forms part of a lineage leading to Archaeodesmana elvirae and Archaeodesmana brailloni; this lineage is characterized by an increase in size and in the molarization of the upper premolars. Desmaninae are identified in all the latest Miocene and earliest Pliocene localities from the Granada Basin, evidencing the existence of permanent water bodies. On the contrary, they are not found in sites of similar age in the Guadix Basin, which would have had more arid conditions. The coincident appearance of A. cf. getica in both basins during the early Ruscinian indicates a change towards more humid conditions in the region, allowing the establishment of permanent water flows in the Guadix Basin. http://zoobank.org/urn:lsid:zoobank.org:pub:E3E441D0-CF66-4320-AA2E-17FB7BC10B39

New paleobiogeographical and paleoenvironmental insight through the Tortonian brachiopod and ichnofauna assemblages from the Mediterranean-Atlantic seaway (Guadix Basin, SE Spain)

The paleogeography of the Late Neogene Atlantic-Mediterranean seaway via the Betic-Rifean Domain is quite complex due to the presence of several marine corridors. The study of transitional basins in these seaways is crucial to understand the configuration and evolution of the Mediterranean-Atlantic inter-connection. A mixed skeletal-siliciclastic sandstone succession located in one of these transitional areas (Guadix Basin, Southern Spain) was studied from a comprehensive paleontological standpoint focused on the main benthic assemblages (foraminifera, brachiopods, and trace fossils), integrating the data with the study of planktic foraminifera for an accurate biostratigraphic framework. Brachiopods are mostly represented by the Aphelesia-Gryphus assemblage. Two trace fossil assemblages were observed, dominated by Ophiomorpha with Bichordites (1) and Macaronichnus (2), respectively. The benthic foraminiferal assemblage is mostly represented by Planulina and Cibicides. The data gathered from the benthic communities reveal habitats with high-energy and turbulent conditions in an outer neritic-upper bathyal bathymetric range. Brachiopods from the Alicun section show a Mediterranean paleobiogeographic affinity. They were constrained in the Late Tortonian to the restricted basins of the Betic-Rifean Seaway and after the Messinian Salinity Crisis proliferated in both Mediterranean- and Atlantic-type basins of the Betic-Rifean Domain. The Guadix Basin contributed to the Mediterranean-Atlantic faunal inter-connection through the Betic-Rifean Seaway during the Late Tortonian and facilitated the earliest Pliocene expansion of brachiopods in the Mediterranean.

A STEP fault in Central Betics, associated with lateral lithospheric tearing at the northern edge of the Gibraltar arc subduction system

We study the crustal and lithospheric mantle structure under central Betics in the westernmost Mediterranean region by migrating P-receiver functions along a dense seismic profile (∼2 km interstation distance). The profile, North–South oriented, probes the crustal structure of different geological units, from the Alboran domain in the south with metamorphic rocks, through the External Zones with sedimentary rocks to the Variscan terrains of the Iberian Massif in the north. From north to south, the Moho depth increases from ∼30 km to ∼46 km underneath the Guadix basin, due to the underthrusting of the Iberian crust below the Alboran crust, and suddenly shallows to ∼30 km underneath the Internal Zones with a step of 17 km. This sharp Moho step correlates well with a lithospheric step of ∼40 km, where the thickness of the lithosphere changes abruptly from ∼100 km in the north to ∼50 km in the south. We interpret this sharp and prominent lithospheric step as the termination of the Iberian lithosphere caused by a near-vertical STEP (Subduction-Transform-Edge-Propagator) fault that continues towards the surface as a positive flower tectonic structure of crustal scale. This STEP fault is located at the northern edge of the narrow Westernmost Mediterranean subduction system facilitating the slab rollback motion towards the west. The sharp termination of the Iberian lithosphere occurs under the contact between the Alpujarride and the Nevado-Filabride complexes of the Alboran domain in an ENE-WSW right-lateral transpressive shear zone. The thickest crust and lithosphere do not correlate with the highest topography along the profile suggesting that this high topography is a combined effect of the positive flower structure, and the push up of the asthenosphere produced by the removal of the Iberian lithosphere.

The last giant continental tortoise of Europe: A survivor in the Spanish Pleistocene site of Fonelas P-1

The presence of remains of a giant tortoise in the lower Pleistocene site of Fonelas P-1 (Guadix Basin, Betic Ranges; Granada, southeastern Spain) is reported and analyzed herein for the first time. This finding represents the youngest evidence of a large tortoise in continental Europe, dating the age of extinction of this successful lineage as several hundred thousand years younger than previously thought. So far, the most recent record known for continental Europe was at least 400,000years older than the occurrence reported herein (Vaterá, Greece), that for the Spanish record being about 1.3millionyears older (Las Higueruelas). This finding is justified as the youngest evidence of Titanochelon, a genus recorded in Europe since the beginning of the Miocene, which includes the largest terrestrial turtles known for the entire European fossil record. The decrease in the biogeographical distribution area and the final extinction of these temperature-sensitive animals in Europe is here recognized as a result of the climate changes documented during the Pliocene and lower Pleistocene. The identification of taxa with environmental and ecological requirements as restrictive as those known for the extant and extinct large tortoises, living in continental Europe 2.0Ma, has important consequences. Thus, although the paleoclimatic inferences generally assumed for the whole of Europe interpret cooler and drier conditions at the end of the Pliocene, by the increase of the seasonality and the beginning of the glacial activity in the Northern Hemisphere, the record of Fonelas P-1 indicates that, in southern Europe or, at least, in the endorheic basins of the Betic Ranges, warmer climatic conditions than in the rest of the continent continued being present in these chronologies of the lower Pleistocene, being favorable for the persistence of these large tortoises.

Facies architecture, geochemistry and palaeoenvironmental reconstruction of a barrage tufa reservoir analog (Betic Cordillera, S. Spain)

Continental carbonates are currently of high interest for the oil and gas industry, as they have proved to be good reservoir rocks in Brazil and Angola offshore oil fields. In this article, a tufa system in which continental carbonates formed mainly in the Pliocene (Rambla Becerra Tufa System, Guadix Basin, Betic Cordillera, S. Spain), is described in detail, and a model proposed for its formation and evolution through time. Several stages of tufa growth have been identified in the field, intercalated between stages of progradation of alluvial fan sediments. The tufa system connects laterally with the fluvial system developed in the axial valley of the Guadix Basin during the Pliocene and the Pleistocene, indicating that the tufa formation was coetaneous with the periods of lateral expansion of the fluvial system floodplain, that in previous works have been interpreted as more humid stages and potentially warmer. The absence of extraclasts in the tufa sediments points to the low activity of the alluvial fans during the tufa formation and therefore supports the idea that the main tufa growth happened during more humid stages, and the alluvial fans developed further during the more arid periods, which is consistent with other recent findings in the Guadix Basin. The tufa growth is represented by four main stages, the second one bearing the best example to study as a potential reservoir analog, as the main outcrop is a discrete body with a specific geometry and facies distribution. This main outcrop is a mound-shaped tufa build-up formed by prograding sigmoids of clastic tufa, interpreted as the ramp-like buttresses developed after a barrage in a barrage tufa system. From a preliminary isotopic study of the carbonates forming the barrage tufa system and by comparison with other tufas and travertines, the oxygen and carbon stable isotopes point to an intermediate situation between a palustrine tufa and a travertine. This information, when added to the sedimentological data, supports the idea that water feeding the tufa system probably had different sources: a meteoric one, coinciding with the surface runoff and a groundwater one, probably in the form of springs fed by groundwater from the nearby aquifers that still exist in the Mesozoic carbonates that form the External Zones of the Betic Cordillera in the area.

The Epivillafranchian and the arrival of pigs into Europe

Suids are found in Europe before and during the Olduvai magnetostratigraphic subchron, including the Fonelas P-1 site in the Guadix Basin (Andalusia, Southern Spain, ∼2.0 Ma), in which the remains have been ascribed to Potamochoerus magnus, and many other localities that record the presence of Sus strozzii (e.g., Saint Vallier and Senèze in France). However, there is no pig record in the biochronological range comprised between the post Tasso Faunal Unit, which marks the base of the Late Villafranchian (∼1.8 Ma), and their arrival in Western Europe at layer TE9 from Sima del Elefante, Atapuerca, Northern Spain (∼1.2 Ma), where pigs are recorded under the name of Sus sp., and at the sites of Untermassfeld (Germany), Vallonnet (France) and layer EVT12 of Vallparadís Estació (Spain), dated 1.1–1.0 Ma (MIS31), which suid remains have been ascribed to Sus scrofa priscus in the first site and to Sus sp. in the other two. Later, the genus Sus is recorded everywhere in Europe as a ubiquitous member of the Epivillafranchian/Galerian and posterior faunas. When pigs are in an ecosystem, they use to be abundant in the large mammal community given their opportunistic feeding behavior and high reproductive success. Their short gestation periods and elevated offspring numbers allow them to colonize new and varied environments and territories faster than other ungulates, which use to display a K-reproductive strategy, with a single pup per birth. For this reason, suids are usually preserved in the fossil assemblages after their dispersal and colonization of a geographic region. The arrival of suids phylogenetically related to Sus gr. scrofa into Europe marks the end of the Late Villafranchian and the beginning of the Epivillafranchian, which is approximately dated at ∼1.2 Ma. Given that suids are omnivorous, generalist mammals with bunodont teeth that do not tolerate very low temperatures, this suggests that their colonization of Europe can be related to a change in the ecosystems and climate. In addition, the arrival of suids postdates the earliest arrival of hominins into Western Europe, which is documented at the Orce sites of Barranco León-D and Fuente Nueva-3 (∼1.5–1.2 Ma). In these sites, rich faunal assemblages, abundant lithic artifacts and one human tooth have been unearthed after more than twenty years of excavations, but no evidence of pigs has yet been detected.

Climatic control on palaeohydrology and cyclical sediment distribution in the Plio-Quaternary deposits of the Guadix Basin (Betic Cordillera, Spain)

A cyclical pattern can be observed in the central sector of the Guadix Basin (southern Spain) in the Late Pliocene-Quaternary alluvial fan deposits prograding into its axial valley. A climatic significance has been attributed to this cyclicity on the basis of sedimentological and preliminary isotopic studies. The progradation phases of the alluvial fans are here attributed to more arid time intervals in which the vegetation cover would be less developed, erosion and sediment supply would be higher, and base level would be lower. In contrast, the time intervals during which the fluvial system sediments dominated the area are inferred to be wetter and base level higher, with vegetation cover retaining the soils and preventing erosion. Permanent water supply to the river would therefore facilitate the aggradation of the floodplain and prevent progradation of the fans. Starting from a litho-, bio- and magnetostratigraphical frame provided for the area, an age is assigned to the alternation of the reddish sediments of the transverse alluvial fans and the greyish to white fluvio-lacustrine sediments of the axial drainage system. A cyclicity of ca. 100 ky has been identified in most of the alluvial fan progradation phases, falling within Milankovitch high-frequency eccentricity periodicities. Correlation of the phases with insolation curves is accordingly discussed as a possible origin for the cyclicity. Finally, the results offer new insights into early hominin occupation patterns in the region, through the identification of predictable resources of permanent fresh water that would have remained available throughout the recorded time span (that includes the Early–Middle Pleistocene transition) even during times of aridification.

The late Miocene continentalization of the Guadix Basin (southern Spain) reconsidered: A comment on Hüsing et al. (2010)

Hüsing et al. (2010: Palaeogeography Palaeoclimatology Palaeoecology 291, 167–179) made an approximation to the age of the closure of the Betic Seaway through the Guadix Basin during the late Miocene, on the basis of integrated paleontological (foraminifera and micromammals) and magnetostratigraphic data from the marine-continental section of La Lancha. They provide very interesting information that contributes to understand the chronology of the marine to continental transition in the basin, but we would like to comment some inaccuracies in the interpretation of the age of the oldest continental levels of the studied section. Moreover, we discuss several recently described late Miocene continental faunas from the Guadix Basin, such as Negratín-1 and Rambla de Chimeneas-3, which were not considered by Hüsing et al. for their interpretations. Finally, we review the age of the site of Salinas, originally assigned to MN12 and discussed by Hüsing et al., but which had already been reconsidered by other authors who concluded that the existence of middle Turolian mammal faunas in this basin cannot be demonstrated.

On the Late Miocene continentalization of the Guadix Basin: More evidence for a major Messinian hiatus

The chronology of the Late Miocene Mediterranean-Atlantic gateways through southern Iberia is a key issue to better understand the geodynamic processes that lead to the Messinian salinity crisis. The timing of the North Betic corridor continentalization has recently been constrained by integrated magnetobiostratigraphic dating of the La Lancha section in the Guadix basin (Hüsing et al., 2010: Palaeogeography Palaeoclimatology Palaeoecology 291, 167–179). This work showed that the continentalization of the Guadix basin encompasses an approximately 2 myr hiatus, with the interval between ∼7.7 to ∼5.5 (or 5.0) Ma missing in the stratigraphic record. Minwer-Barakat and colleagues comment that this hiatus could be slightly shorter, but they base their hypotheses solely on an interval without any reliable magnetostratigraphic data. Their key localities Negratín 1 and Rambla de Chimeneas 3 (MN13), however, confirm that the oldest faunas found at La Lancha section correlate with the upper part of chron C3r (∼5.5 Ma). These continental faunas thus provide more evidence on the presence of a major Messinian hiatus in the Guadix record.

Micromammal biostratigraphy of the Upper Miocene to lowest Pleistocene continental deposits of the Guadix basin, southern Spain

Minwer-Barakat, R., Garcia-Alix, A., Suarez, E.M., Freudenthal, M. & Viseras, C. 2012 xx xx: Micromammal biostratigraphy of the Upper Miocene to lowest Pleistocene continental deposits of the Guadix basin, southern Spain. Lethaia, Vol. 45, pp. 594–614. Recent study of the small mammals (rodents and insectivores) from several fossil-bearing sites situated in the central sector of the Guadix Basin (Southern Spain) has notably increased the knowledge of the mammal assemblages that existed in Southern Iberia from the latest Miocene to the earliest Pleistocene. On the basis of this new information, we propose a biozonation for the continental deposits of the Guadix Basin, which consists of six biozones ranging in age from the late Turolian (MN13) to the early Villanyian (MN17). These biozones, defined according to the rules of the International Stratigraphical Guide, include not only the mentioned recently discovered fossil sites, but also other, previously known, localities of the basin. Finally, we integrate the described biozones in the Neogene Mammal units and the European Land Mammal Ages, correlate them with several classical mammal sites from other Iberian basins and the rest of Europe, and establish an approximate numerical age for the lower and upper limits of each biozone. □Biostratigraphy, Guadix Basin, rodents, insectivores, Upper Miocene, Pliocene, Pleistocene.

Thick brachiopod shell concentrations from prodelta and siliciclastic ramp in a Tortonian Atlantic–Mediterranean strait (Miocene, Guadix Basin, southern Spain)

Carbonate production by brachiopods in shallow-water habitats is generally expected to be not sufficiently high and temporally persistent to allow them to form very thick and densely packed shell concentrations. The formation of thick brachiopod concentrations requires long-term persistence of populations with high density of individuals, and such circumstances are assumed to be rare especially during the Cenozoic. However, here we show that the large-sized brachiopod Terebratula terebratula, the most common species in benthic assemblages with epifaunal bivalves and irregular echinoids, formed several decameter- to meter-thick, densely packed concentrations in shallow siliciclastic, high-energy environments, in a seaway connecting the Atlantic Ocean with the Mediterranean Sea during the Latest Tortonian (Late Miocene, Guadix Basin, southern Spain). This brachiopod formed (1) meter-scale, thick, parautochthonous concentrations in a prodelta setting and (2) thin, mainly allochthonous, tide- and storm-reworked concentrations in megaripples and dunes. The abundance of brachiopods at the spatial scale of the Guadix Basin seems to be mainly related to intermediate levels of sedimentation rate and current velocity because abundance and thickness of shell concentrations decline both (1) in onshore direction towards delta foresets with high sedimentation rate generated by debris flows and (2) in offshore direction with increasing levels of tide- and storm-induced substrate instability. Although brachiopods in dune and megaripple deposits are more fragmented, disarticulated, and sorted, and have a higher pedicle/brachial valve ratio than in prodelta deposits, taphonomic damage is still relatively high in prodelta deposits. Terebratula terebratula thus formed thick concentrations in spite of that disintegration processes were relatively intense along the whole depositional gradient. Therefore, population dynamic of this species was probably characterized by production maxima that were comparable to some Cenozoic molluscs in terms of their productivity potential to form thick shell concentrations in shallow subtidal environments. We suggest that temporal changes in brachiopod carbonate production have a significant spatial and phylogenetic component because multiple large-sized species of the family Terebratulidae, which underwent radiation during the Cenozoic, attained high abundances and formed shell concentrations in temperate regions.

A stratigraphic framework for the Pliocene–Pleistocene continental sediments of the Guadix Basin (Betic Cordillera, S. Spain)

The central sector of the Guadix Basin (Betic Cordillera, S. Spain) hosts some of the most significant Pleistocene large-mammal sites in Europe. The basin infill is divided into six genetic units, the three lower with marine sediments and the remainder mainly continental. As the environmental characterization of the sediments is crucial to understand the ecologic and geologic processes leading to the formation of these sites, a stratigraphic, sedimentologic and petrologic study is presented. Combining a lithologic correlation with previous biostratigraphic data and new magnetostratigraphic data, a detailed litho-, bio- and magnetostratigraphic scheme has been developed for the study area. It shows the stratigraphic architecture of the central sector of the Guadix Basin, together with the age and the relative spatial position of the most important mammal sites. As well, it has been also helpful to identify several isochronous surfaces, to establish the exact position and the age of the boundary between the two last units of the continental infill in the Guadix Basin and to calculate sedimentation rates.

Soricidae (Soricomorpha, Mammalia) from the Pliocene of Tollo de Chiclana (Guadix Basin, southern Spain)

ABSTRACT The fossil shrews (Soricidae, Lipotyphla, Mammalia) from the Pliocene continental deposits of Tollo de Chiclana (Guadix Basin, southern Spain) are described. Remains of Asoriculus gibberodon, Blarinoides aliciae, Petenyia hungarica, Paenelimnoecus pannonicus, Myosorex meini, and an indeterminated species of Soricidae have been recognized. With the exception of A. gibberodon, these species are very uncommon in the south of the Iberian Peninsula; in fact, this finding represents the first record of Petenyia, Blarinoides, Paenelimnoecus, and Myosorex in the Guadix Basin. The changes in the abundance of Soricidae in the studied levels indicate wet and warm climatic conditions during the late Ruscinian and early Villanyian, and a decrease in the temperature and precipitation in the late Villanyian.

On the late Miocene closure of the Mediterranean–Atlantic gateway through the Guadix basin (southern Spain)

The late Miocene Mediterranean–Atlantic connection through southern Spain is generally thought to have closed during the late Tortonian, but accurate constraints on palaeobathymetry, shallowing rates and closure age are still lacking. We present integrated biostratigraphic (planktonic, benthonic foraminifera and mammals) and magnetostratigraphic results from the marine to continental La Lancha section of the Guadix Basin, refining the chronology for the Miocene–Pliocene sedimentary sequences of this basin that occupied a central position in the marine gateway. In addition, we perform palaeobathymetric analyses on the marine sedimentary sequence to reconstruct sea level fluctuations and vertical motions. Deposition of the Lower Marine Unit took place between 8.1 and 7.85 Ma with accumulation rates of ∼ 1 m/kyr. A rapid shallowing from palaeodepths of 500–300 m to a depth of 300–200 m took place at ∼ 8.0 Ma coinciding with a decrease in downslope transport. Surprisingly, no shallowing trend has been observed towards the unconformable contact with the Transitional Unit, which was deposited in a shallow (∼ 90 m) marine environment. The youngest open marine marls are still indicative for a palaeodepth of > 200 m. This leads to the conclusion that fully marine environments in Guadix persisted until at least 7.85 Ma. The palaeomagnetic polarity pattern of the Upper Continental Unit, in combination with the presence of the murid Paraethomys meini in the basal part of this sequence, indicates that the entire continental unit at La Lancha is attributed to the latest Messinian–Zanclean time. This age is in strong contradiction with previous correlations to the late Tortonian. Consequently, we conclude that a major hiatus of at least 2 Myr, comprising most of the Messinian stage, is present in the Guadix basin. Therefore a late Tortonian closure age of the Mediterranean–Atlantic gateway through Guadix has not been confirmed by our results, so that the possibility of a Messinian gateway through southern Spain cannot be completely ruled out.

The micromammal fauna from Negratín-1 (Guadix Basin, southern Spain): new evidence of African-Iberian mammal exchanges during the Late Miocene

A rich and diverse micromammal fauna from the late Turolian (MN13) locality of Negratín-1 (Guadix Basin, southern Spain) is described. The faunal list of this site includesApodemus gudrunae, Occitanomys alcalai, Stephanomys dubari, Paraethomys meini, Myocricetodon jaegeri, Debruijnimys almenarensis, Apocricetus alberti, Ruscinomyssp.,Eliomyssp.,Atlantoxerussp.,Parasorex ibericus, and Soricidae indet. This is the most nearly complete mammal fauna from the Miocene of the Guadix Basin and allows precise correlations with localities from other Iberian areas. In addition, some of the taxa identified in Negratín-1 are useful as palaeoecological indicators (Myocricetodon, Debruijnimys, Atlantoxerus), evidencing warm and dry climatic conditions. But the principal interest of the fauna from Negratín-1 is the presence of several species of African origin, the gerbillidsDebruijnimys almenarensisandMyocricetodon jaegeri, which are recognized for the first time in Europe. We also ascribe toM. jaegerithe population from the upper Turolian karst infilling of Almenara-M. This finding constitutes new evidence for faunal exchanges between North Africa and the Iberian Peninsula during the Messinian Salinity Crisis.

Downslope-migrating sandwaves and platform-margin clinoforms in a current-dominated, distally steepened temperate-carbonate ramp (Guadix Basin, Southern Spain)

During the Late Tortonian, platform-margin-prograding clinoforms developed at the south-western margin of the Guadix Basin. Large-scale wedge-shaped deposits here comprise 26 rhythms of mixed carbonate–siliciclastic bedset packages and marl beds. These sediments were deposited on a shallow-water, temperate-carbonate distally steepened ramp. A downslope-migrating sandwave field developed in this ramp, with sandwaves moving progressively down the ramp to the ramp-slope, where they destabilized, folded and occasionally collapsed. Downslope sandwave migration was induced by currents flowing basinwards. During the Late Tortonian, the Guadix Basin was open north to the Atlantic Ocean via the Dehesas de Guadix Strait and connected east to the Mediterranean Sea through the Almanzora Corridor. According to the proposed current circulation model for the Guadix Basin for this time, surface marine currents from the Atlantic entered the basin from the northern seaway. These currents moved counter-clockwise and shifted the sediment on the ramp, forming sandwaves that migrated downslope. The development of platform-margin prograding clinoforms by the basinward sediment-transport mechanisms inferred here is known relatively poorly in the ancient sedimentary record. Moreover, these wedge-shaped geometries are similar to those found in some shelves in the Western Mediterranean Sea and could represent an outcrop analogue to (sub)-recent, platform-margin clinoforms revealed by high-resolution seismic studies.

Major controls on sedimentation during the evolution of a continental basin: Pliocene–Pleistocene of the Guadix Basin (Betic Cordillera, southern Spain)

Sequence stratigraphy, based on climatic, tectonic, and base level parameters, can be used to understand carbonate sedimentation in continental basins. The uppermost continental fill of the Guadix Basin (Betic Cordillera), containing both siliciclastics and carbonates, is investigated here. In its central sector a thick succession of fluvio-lacustrine sediments appear, hosting several important Pliocene and Pleistocene macrovertebrate sites (Fonelas Project). The need to characterize the stratigraphic and sedimentologic context of these important paleontologic sites has lead to litho-, magneto- and biostratigraphic studies. These data, together with the sedimentologic analysis of the Pliocene and Pleistocene siliciclastic and carbonate successions, establish a sedimentary model for the fluvio-lacustrine sedimentation of the two last stages of sedimentation in the Guadix Basin (Units V and VI). Unit V comprises mostly fluvial siliciclastic sediments with less abundant carbonate beds interpreted as floodplain lakes or ponds. The latter, Unit VI, is dominated by vertically-stacked, carbonate palustrine successions. Using two pre-existent continental stratigraphic models, the influence of climate, tectonism, and stratigraphic base level during the last 3.5 Ma on the sedimentary evolution of the fluvio-lacustrine system in the Guadix Basin, especially the carbonate sedimentation patterns, is outlined.

High-Frequency Rhythmicity in a Mixed Siliciclastic-Carbonate Shelf (Late Miocene, Guadix Basin, Spain): A Model of Interplay Between Climatic Oscillations, Subsidence, and Sediment Dispersal

Abstract Rhythmites in pelagic sediments can include information on paleoclimate and with orbital cycles. This paper documents and interprets an unusual rhythmic succession from a cool-water shallow-marine shelf that includes features of Mediterranean-type ramps and open-ocean-type ramps. In the subsiding southwestern margin of the Guadix Basin (southern Spain, Betic Cordillera), during the late Tortonian, a 640-m-thick succession was deposited over a short period (7.8–7.2 Ma). This succession contains 30 sedimentary packages or rhythmites, each defined by two facies associations: a mixed cross-stratified siliciclastic–skeletal sandstone and a homogeneous marl rich in planktonic foraminifera. Sandstones ranging in thickness from 3 m to 20 m contain coralline algae, bivalves, bryozoans, benthic foraminifera, echinoids, and brachiopods (typical temperate-water shelf biofacies). These units exhibit cross-strata sets up to four meters high, interpreted to have been produced by strong unidirectional currents. The marly deposits range in thickness from 2 to 17 m and contain an association of cold-water planktonic foraminifera as well as thin sandstone layers that exhibit normal grading corresponding to typical incomplete Bouma sequences or a lower division with planar lamination and an upper division of very fine- to fine-grained sandstone with hummocky and swaly cross-stratification. On the basis of the sedimentary structures, the sandstone layers are interpreted as sporadic turbidity flows and storm ebb–surge deposits. On the basis of the sedimentary structures, the hydrodynamic conditions during deposition of the mixed siliciclastic–carbonate interval were high-energy. Based on sedimentary and biogenic features of the rhythmites and their temporal durations (ca. 20 ka), rhythmicity is interpreted to reflect alternating cool-wet and cold-dry climate episodes driven by precession orbital cycles. This occurrence of alternating mixed carbonate–siliciclastic sedimentation and pelagic sediments represents a unique occurrence in the geologic record.

Late Turolian micromammals from Rambla de Chimeneas-3: considerations on the oldest continental faunas from the Guadix Basin (Southern Spain)

The fauna from Rambla de Chimeneas-3 (RCH-3), a new uppermost Miocene micro- mammal site from the Guadix Basin, is described. This level has yielded remains of Paraethomys meini, Occitanomys alcalai, Stephanomys cf. dubari, Cricetinae indet., Erinaceidae indet., and Soricidae indet. This faunal assemblage can be assigned to the upper Turolian (MN13). The section of Rambla de Chimeneas is situated in the lower part of the oldest exclusively continental stratigraphic unit distinguished in the filling of the Guadix Basin. Other rodent faunas from this unit were previously assigned to the middle Turolian (MN12). In this paper we reconsider the age of the oldest mammal localities from the Guadix Basin, concluding that none of them can be clearly assigned to MN12. Therefore, there is no evidence of the continentalization of the basin before the late Turolian.

Desmaninae (Talpidae, Mammalia) from the Pliocene of Tollo de Chiclana (Guadix Basin, Southern Spain): Considerations on the phylogeny of the genus Archaeodesmana

The fossil Desmaninae (water-moles) from the Pliocene continental deposits of Tollo de Chiclana (Guadix Basin, Southern Spain) are described. A new species, Archaeodesmana elvirae, is defined from the locality of Tollo de Chiclana-1 (upper Ruscinian). This species is characterized by relatively small canines and premolars (except the P4) and large P4 and molars, besides several morphological features. The presence of Archaeodesmana brailloni is reported from the locality of Tollo de Chiclana-1B (uppermost Ruscinian). A small sample assigned to the genus Archaeodesmana is described from the lower Villafranchian site of Tollo de Chiclana-3, which cannot be determined at the specific level. The phylogenetic relationships between the different species of Archaeodesmana are reconsidered in the light of the recent findings, which support the idea of a more complex phylogeny than previously proposed for this genus. The populations from the Guadix Basin, previously assigned to Dibolia dekkersi (= Archaeodesmana getica), are here considered to belong to a different (unnamed) species, which is the ancestor of A. elvirae. On the other hand, the new species A. elvirae is proposed as the ancestor of A. brailloni.