The Pleistocene lake deposits of the NE Baza Basin (Spain): salinity variations and ostracod succession

The Guadix-Baza Basin in Spain covers an area of approximately 3000 km² and yields a sedimentary sequence ranging from Lower Miocene to Pleistocene. Twenty five meters of Lower Pleistocene lacustrine sediments have been located in the NE part of the Basin at about 1000 meters in altitude. This sequence which overlies dolomitic mud flat deposits consists of limestones, calcareous and dolomitic mudstones, dolostones, silty clays, sands and gravels. Salinity fluctuations and short dry episodes, related to lake level oscillations, have been recorded by textural, mineralogical and faunal changes throughout the sequence. Ostracods, which are the most commonly encountered fossils, permit to detect recurrent changes in water salinity and regime, and solute composition. The faunal changes indicate an alternation of slightly saline and bicarbonate-rich water (when ostracods and gastropods occur) with a saline NaCl-dominant water (in which ostracods, Cerastoderma bivalves and non-marine foraminifers are found).The frequent and recurrent hydrochemical changes in the Baza Basin in the Early Pleistocene point to a climate of high contrast like in the Mediterranean region today but with a greater availability of water within the system compared to the present situation in the area.     

Pleistocene paleoenvironmental evolution at continental middle latitude inferred from carbon and oxygen stable isotope analysis of ostracodes from the Guadix-Baza Basin (Granada, SE Spain)

A representative paleoenvironmental reconstruction of continental middle latitude from ca. 2 my to the upper part of Middle Pleistocene (279 ± 77 ky) was obtained from the carbon and oxygen stable isotopes analyzed in ostracode shells (Cyprideis torosa) recovered in the Guadix-Baza Basin (SE Spain), an intramontaneous closed depression filled by alluvial and lacustrine sediments. This study was performed along a 356-m-thick composite section, dated previously by paleomagnetism and the amino acid racemization method. δ¹³C and δ¹⁸O profiles reflected changes in temperature, the evaporation/infill ratio in the water bodies and the amount of rain. δ¹³C is also affected by changes in plant biomass: periods with high δ¹³C and δ¹⁸O values are associated with warm and dry regimes, and with less vegetation, which, in some cases, coincide with the development of displacive gypsum crystals, whereas low δ¹³C and δ¹⁸O values correlate with cold and humid episodes, which cause more vegetation biomass and, therefore, increasing the input of isotopically light carbon. Intermediate δ¹⁸O values are linked to temperate dry or humid episodes when they coincide with high or low δ¹³C values, respectively. 86 paleoclimatic events were distinguished in the Pleistocene record from the δ¹³C and δ¹⁸O profiles. From both the statistical analysis of the geochemical data and the geological observations, four Cold and Humid Long Periods (low δ¹⁸O) and four Warm and Dry Long Periods (high δ¹⁸O) were defined. This differs with respect to the paleoclimatological behavior established for the Northern Hemisphere where during cold periods (glacial), no water was available while permafrost conditions persisted, whereas in warm episodes (interglacial), higher precipitation rates occurred. Good correspondences between the Guadix-Baza Basin paleoclimatic record and a marine oxygen-isotope sequence, two continental cores and other long Mediterranean paleoenvironmental records (pollen sequences from Israel) were found, which suggested that climate changes in the Guadix-Baza Basin were in tune with global climatic changes.     

New charophyte assemblage from middle Miocene lacustrine deposits of Moneva (Ebro Basin,Spain)

Two new fossil charophyte species from middle Miocene lacustrine deposits of Moneva (Ebro Basin, NE Spain) are described and illustrated. Sphaerochara miocenica nov. sp. is represented by medium sized gyrogonites with a characteristic spheroidal shape and ornamented with numerous small and regularly spaced tubercles arranged along the spiral cells. Several specimens show an unusual carbonate encrusted layer that covers completely or partially the gyrogonite. Psilochara monevaensis nov. sp. is characterized by large gyrogonites, with typical prolate shape and protruding apical poles. A second population of S. miocenica nov. sp. from a distant early upper Miocene lacustrine basin located in the Middle East (Bekaa Valley, Lebanon), identified in a previous study as Sphaerochara sp., is described and illustrated here, allowing the comparison of these distant populations. Ecologically, the associated fauna and facies from both localities suggest that these taxa grew in very shallow athalassic lakes. Interestingly, S. miocenica nov. sp. having a wide geographic distribution in peri-Mediterranean lakes with variable salinity, may become a fossil guide for the Miocene, providing at the same time important palaeoecological information.     

High-frequency cycles in Upper-Miocene ramp-temperate carbonates (Sorbas Basin,SE Spain)

Uppermost-Tortonian temperate carbonates occur at the southern margin of the Sorbas Basin (Almería, SE Spain). These carbonates, included in the Azagador Member, formed in a gentle, shallow-water ramp. Six facies cycles in ramp deposits comprise alternating bivalve-shell concentrations and coralline algal beds. The basic cycle reflects the landward advance, as relative sea level rose, of coralline algal deposits, which were the facies of the outer ramp, over bivalve biostromes, which grew in the shallower areas of the mid-ramp. Biostromes were mainly built by oysters and locally by Isognomon. In many cases, however, the removal of smaller shells by storms left only thin, discontinuous patches of large bivalves as residual remains of the oyster biostromes. Some original cycles might be missing due to complete removal of bivalve shells from the biostromes. The six cycles recognised, therefore, should be considered as the minimum number of original cycles in the Azagador carbonates. The available age constraints suggest these cycles were forced by orbital precession or some higher-frequency process. Lithological cycles forced by precession are characteristic of the basinal deposits laterally equivalent to the Azagador carbonates.     

Megarhizoliths in Pleistocene aeolian deposits from Gran Canaria (Spain): Ichnological and palaeoenvironmental significance

The Pleistocene dune field of Tufia, located on the east of Gran Canaria (Spain), contains different stratigraphic levels of indurated pillar-like structures that are interpreted as megarhizoliths. The megarhizoliths occur at the top of different aeolian sets and reach 31.5 cm in diameter and over 1 m in height. These scattered, free-standing, vertical, cylindrical-to-slightly conical columns usually appear as hollow cylinders, displaying elliptical cross-sections aligned with the prevailing wind. On the leeward side of some specimens the external wall shows a tail of rock matrix resembling a sort of “wind shadow”. These tails and other remains of the associated rock matrix show a texture composed of long, horizontal, parallel cylinders orientated with the wind.Internally the most complete structures show five concentrically arranged zones: Zone (a), is a central pore corresponding to the cavity originally occupied by the root; Zones (b) and (c), which include alveolar and laminated carbonate textures indicating that carbonate precipitation was mostly induced by the roots and their associated microorganisms; and Zones (d) and (e), consisting mostly of aeolian sands. In (d) the sand grains show thin micritic coatings whereas in (e) vadose aragonite cements can be seen on the grain surface suggesting a less biogenic influence in their formation. The degree of cementation and the time of the precipitation of carbonate around the roots controlled the preservation of these zones. Thus, in some cases, Zones b, c and/or d are not preserved. Cylinders are up to 30× the diameter of the root that nucleated them.The presence of the megarhizoliths at the top of the aeolianite beds indicates that aeolian sedimentation halted several times, allowing soil formation and plant colonisation during slightly more humid periods. The occurrence of megarhizoliths is further proof of the alternation of arid and slightly more humid climates in the north Atlantic during the last glacial period. It is also noted that they may be misinterpreted as animal trace fossils or tree trunk casts, resulting in incorrect ichnological or palaeoenvironmental interpretations.     

Early Miocene repetitive vegetation and climatic changes in the lacustrine deposits of the Rubielos de Mora Basin (Teruel, NE Spain)

Pollen analysis of a Lower Miocene succession from the Rubielos de Mora Basin (NE Spain) has been carried out with the aim of reconstructing the flora, vegetation and climatic changes. Previous paleobotanical studies on these sedimentary rocks and adjacent areas interpreted very diverse climates for the Early Miocene: from humid temperate to dry subtropical. In this study, a rich thermophilous pollen spectrum and a diverse subarid flora including Nitraria, Caesalpiniaceae, Ephedra and Acacia, indicative of a dry subtropical climate are identified. On the other hand, mesothermic taxa with high water requirements are also abundant. Therefore, the pollen assemblages evidence the juxtaposition of very contrasted environments: the presence of subdesertic taxa, typical of plants growing in the lowlands and conditioned by a long warm, dry season, together with others with very high water requirements, needing constant water. This can be explained by the presence of the Rubielos de Mora Lake providing local conditions for developing riparian forests. The vegetation was clearly controlled by the water availability under a subtropical and dry-seasonal climate. Pollen changes along the succession, which coincide with sedimentological changes, are related to climatic variations. Alternation in pollen taxa (thermophilous–dry vs. mesothermic–riparian) reflects the influence of the cyclicity of temperature and precipitation on the lake level and vegetation.     

Environmental Variables and Planktonic Communities in Two Ponds of El Hondo Wetland (SE Spain)

The annual cycle of physical and chemical variables and plankton dynamics was studied in two shallow ponds (East and West Ponds) of the El Hondo wetland, an ecosystem of international importance. Water conductivity increased up to 31–49 mS cm^–1 as water level decreased due to high evaporation and minimal water inputs. Initially considered mesohaline, the waters were reclassified as polyhaline during the hot season. EP was subject to successive desiccation‐flooding cycles, and flooding of the dried sediment caused the release of high concentrations of nitrogen and phosphorus compounds, which quickly depleted. The algal species composition was typical of eutrophic ecosystems, and the chlorophyll content indicated that EP was eutrophic and WP mesotrophic. Phytoplanktonic species richness and diversity were low in both ponds. Algal assemblages, in terms of biovolume, were mainly dominated by Dinophyceae in EP and by Cryptophyta in WP. The zooplankton community was dominated by Rotifers (Brachionus and Hexarthra), although Copepods and Ciliates were also important. Different water inputs to the ponds, partial drying in EP during the warm season with the subsequent higher increment of salinity, and the presence of dense populations of submerged macrophytes in WP, explain the differences in plankton communities found between the two ponds.     

Stephanorhinus hundsheimensis (Mammalia,Rhinocerotidae) from the late early Pleistocene deposits of the Denizli Basin (Anatolia,Turkey)

Pleistocene rhinoceroses are poorly documented in Turkey where they have been reported only from the late early Pleistocene (1.3–1.1 Ma) travertine deposits of the Denizli Basin. In this work, new rhinoceros remains collected from this basin are assigned to a relatively large-sized Stephanorhinus hundsheimensis on the basis of their morphology and morphometry. The first Turkish record of this species is approximately coeval with the first appearance of S. hundsheimensis in Europe, chronologically referred to the late early Pleistocene, ca. 1.2 Ma. During that time, S. etruscus still survived in Iberian Peninsula, central Italy and Dacian Basin. The presence of two successive evolutionary morphs for S. hundsheimensis during the Pleistocene is not confirmed.     

Paleoenvironmental reconstruction of the Early Pleistocene site of Quibas (SE Spain) using a rodent assemblage

In this paper we analyze the rodent assemblage from the Early Pleistocene site of Gruta1 (Quibas karstic complex, Murcia, SE Spain), providing taphonomic comments and paleoecological and paleoclimatic data. The studied assemblage includes 209 identified rodent teeth corresponding to at least four taxa. The karstic source of the site and the low presence of digested remains suggest that the accumulation is scatological in origin, with the influence of predators such as owls; the accumulation also shows certain evidence of slight hydrodynamic sorting. For the area around Quibas/Gruta1 the paleoecological study indicates a predominance of rocky areas (31.7%), forested environments (31.7%) and open dry meadows or shrublands (29.7%), which would indicate a mosaic forest environment, and to a lesser extent the presence of open humid land (5.4%) and areas along streams or ponds (1.5%). The distribution of the bioclimatic spectra yields the highest percentage for a Mediterranean climate (37.5%), while the climatic parameters calculated (MAT = 15 °C, MTW = 25.7 °C, MTC = 4.3 °C, MAP = 390 mm) suggest colder and slightly more humid conditions than today at the time of the deposition of the remains. The data also point to a relative decrease in temperature within the phase in which the site was produced, which possibly occurred during a relative cold period between MIS 36 and MIS 40 according to the age.     

Messinian Lago-Mare deposits near the Strait of Gibraltar (Malaga Basin,S Spain)

A new stratigraphic unit (named LM unit) located at the base of the Pliocene marine succession in the eastern sector of the Malaga Basin has been distinguished. This unit is composed of two fining-upward sequences bounded by a discontinuity related to synsedimentary tectonic activity. Both sequences are made up of basal alluvial deposits overlain by subaquatic deposits. The lower sequence contains rich mollusc faunas characterized by bivalves Lymnocardiinae and Dreissenidae of Paratethyan origin, and non-marine gastropods, typical of oligo-low mesohaline shallow waters, and low diversified ostracod faunas of Paratethyan origin (Loxocorniculina djafarovi, Tyrrhenocythere pontica, Euxinocythere (Maeotocythere) praebaquana and Amnicythere propinqua) typical of low mesohaline waters. Alternances of monospecific ostracod assemblages made of Cyprideis agrigentina or oligotypic assemblages made of C. agrigentina and Loxoconcha spp. and richer assemblages made of L. djafarovi accompanied by several Amnicythere spp. and Camptocypria sp.1 characterize the upper sequence, pointing to more unstable environment affected by salinity and depth changes. Some samples collected from this upper sequence yielded rare, planktonic and benthic foraminifera, which could suggest the sporadic establishment of quasi-normal marine conditions in the westernmost Mediterranean during the deposition of this sequence. The palaeontological data and the palaeomagnetic results obtained in both the LM unit and the overlying Pliocene marine sediments restrict the age of the former to the post-evaporitic late Messinian. The age and the environmental conditions correlate these deposits with the Lago-Mare event occurring throughout the Mediterranean before the quick and widespread marine flooding of the Mediterranean at the beginning of the Pliocene.     

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 25 m², 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 4.5 Ma.     

Arvicolidae (Rodentia) from the Pliocene of Tollo de Chiclana (Granada, SE Spain)

Several new fossiliferous Pliocene localities have been identified in the continental deposits of the area of Tollo de Chiclana (Guadix Basin, SE Spain), that have yielded a rich rodent and insectivore fauna. In this paper, we study the Arvicolidae from these localities. Remains adscribed to the genera Dolomys, Mimomys and Kislangia have been found, which are very interesting from a biostratigraphical point of view.     

Minor- and trace-element intra-shell variations in Santonian inoceramids (Basque-Cantabrian Basin,northern Spain): diagenetic and primary causes

Santonian deep- and platform-marine facies inoceramids from the Basque-Cantabrian Basin show clear saw-toothed intra-shell variations with respect to Mg/Ca, Sr/Ca, Na/Ca, Ba/Ca, Fe/Ca and Mn/Ca ratios. Under cathodoluminescence, the most luminescent zones in all the inoceramids present lower Mg/Ca and Sr/Ca (up to 48% and 35% lower values, respectively) and higher Fe/Ca and Mn/Ca ratios (up to 362% and 819% higher values, respectively), which is indicative of diagenetic modification. In contrast, the least luminescent zones show higher Mg/Ca and Sr/Ca ratios and lower Fe/Ca and Mn/Ca. These findings, along with the presence of frequent, well-correlated Mg/Ca, Sr/Ca and Na/Ca ratios, inversely related to Fe/Ca and Mn/Ca, in the weakest luminescent zones suggest major retention of the primary intra-shell variations in these zones. Moreover, Ba/Ca profiles, not connected with the general cathodoluminescence behaviour of the shells, also point towards partial retention of the primary patterns. The saw-toothed intra-shell variations are thought to be caused by the distinct geochemical signals acquired originally by the inoceramid alternating clear and dark growth lines. The deposition of the growth lines and thus the saw-toothed intra-shell variations may be mainly related to periodically changing palaeoenvironmental conditions, such as seawater temperature variations and phytodetritus rainfall. This interpretation is supported by the appearance of highly similar chemical saw-toothed variations in the extant shallow-marine Atrina rigida shell.     

Nannoplankton biostratigraphic calibration of the evaporitic events in the Neogene Fortuna Basin (SE Spain)

The Fortuna Basin is an example of a marginal Mediterranean basin with evaporitic sedimentation during the Late Tortonian and Messinian. This basin shows an early restriction event before the main Messinian Salinity Crisis (MSC) that allows the Tortonian Salinity Crisis (TSC) to be proposed as a tectonic uplift event isolating the eastern Betic basins. Four evaporitic events are present in the central part of the Fortuna Basin, from bottom to top: Los Baños Marls Formation (composed by Fenazar Conglomerate Bed, Lower Gypsum Member [Mb] and Sanel Mb), Tale Gypsum Formation (Fm), Chicamo Diatomites and Gypsum Cycles Fm, and Rambla Salada Gypsum Fm. The present work documents the first biostratigraphic dating based on calcareous nannoplankton of these events. The lowest occurrence (LO) of Amaurolithus primus is registered at the upper part of the Sanel Mb, below the Tale Gypsum Fm. The LOs of Amaurolithus delicatus and Reticulofenestra rotaria, which mark the base of the Messinian, occur in the lower part of the Chicamo Cycles Fm, above the Tale Gypsum Fm, the Triquetrorhabdulus rugosus-Nicklithus amplificus integrate form and the LO of Nicklithus cf. amplificus in the upper part of the Chicamo Cycles Fm. Taking into account these results, a new calibration of the available magnetostratigraphic data is presented: the Chicamo Cycles Fm were formed during the reverse chron C3Ar and the Tortonian-Messinian boundary should be found within the Tale Gypsum Fm or near the top of the Sanel Mb. The onset of the TSC, the first restriction phase of the Fortuna Basin, is represented by the Fenazar Conglomerate Bed, bottom of the Los Baños Fm, and not by the Tale Gypsum Fm, as previously considered.     

Enamel hypoplasia in the Middle Pleistocene hominids from Atapuerca (Spain)

The prevalence and chronology of enamel hypoplasias were studied in a hominid dental sample from the Sima de los Huesos (SH) Middle Pleistocene site at the Sierra de Atapuerca (Burgos, northern Spain). A total of 89 permanent maxillary teeth, 143 permanent mandibular teeth, and one deciduous lower canine, belonging to a minimum of 29 individuals, were examined. Excluding the antimeres (16 maxillary and 37 mandibular cases) from the sample, the prevalence of hypoplasias in the permanent dentition is 12.8% (23/179), whereas the deciduous tooth also showed an enamel defect. No statistically significant differences were found between both arcades and between the anterior and postcanine teeth for the prevalence of hypoplasias. In both the maxilla and the mandible the highest frequency of enamel hypoplasias was recorded in the canines. Only one tooth (a permanent upper canine) showed two different enamel defects, and most of the hypoplasias were expressed as faint linear horizontal defects. Taking into account the limitations that the incompleteness of virtually all permanent dentitions imposes, we have estimated that the frequency by individual in the SH hominid sample was not greater than 40%. Most of the hypoplasias occurred between birth and 7 years (N = 18, X = 3.5, SD = 1.3). Both the prevalence and severity of the hypoplasias of the SH hominid sample are significantly less than those of a large Neandertal sample. Furthermore, prehistoric hunter-gatherers and historic agricultural and industrial populations exhibit a prevalence of hypoplasias generally higher than that of the SH hominids. Implications for the survival strategies and life quality of the SH hominids are also discussed. © 1995 Wiley-Liss, Inc.     

Magnetic signature of environmental change reflected by Pleistocene lacustrine sediments from the Nihewan Basin, North China

A mineral magnetic study has been conducted on Pleistocene lacustrine sediments from the Xujiayao Paleolithic site within the Nihewan Basin, North China. The magnetic signal is characterized by a dominance of high-coercivity (hematite) minerals that is modulated by low-coercivity magnetite–maghemite assemblages during interglacials. A high-amplitude record of the composition dependent magnetic S_− 0.3 T-parameter varies in accord with composite marine oxygen isotope records, suggesting climate modulation of magnetic composition. The Xujiayao site is situated at the northern outskirts of the Chinese Loess Plateau (CLP) and has neither received significant eolian input nor been exposed to pedogenic processes comparable to those acting on CLP. Mineral magnetic analyses suggest that variations in both magnetite and hematite are primarily controlled by detrital fluxes rather than by authigenic production of magnetic minerals. Here we propose that the fluctuations of magnetic signals at Xujiayao are not derived from varying compositions of eolian flux with glacial/interglacial periods or minute eolian influx during interglacials, but is likely dominated by runoff-related processes, by which some weathered/pedogenized loess and soils with stronger magnetic signals have been eroded and transported to the catchment during interglacials resulting in magnetic enhancement. The inferred continuous deposition from the Brunhes/Matuyama boundary to the paleosol S₁ (ca. 129 ka) gives the age of ca. 500 ka for the sediments carrying the Xujiayao Paleolithic site, suggesting an allogenic origin of the Paleolithic artifacts and mammalian bones dated by U–Th method to ca. 100 ka.     

Fossil blackflies from Pleistocene interglacial deposits in Norfolk, England (Diptera: Simuliidae)

ABSTRACT. The occurrence is reported of fragmentary simuliids among Pleistocene fossil arthropod assemblages recovered from deposits in Norfolk of Ipswichian (last) interglacial age, 130 000–120 000 years BP. The condition of each of the nineteen available specimens is described, and sixteen of them are photographically illustrated. Specimens are identified as Simulium s. l. but reliable identification beyond generic level is precluded by lack of diagnostic taxonomic characters. The palaeoenviron-mental significance of simuliids in Quaternary fossil assemblages is briefly discussed; it is thought that the simuliids indicate a palaeoclimate no colder, and possibly warmer, than today.     

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 Alicún 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.     

Variation in the riparian landscape of the Segura River Basin,SE Spain

Abstract. The woody and shrubby riparian vegetation of the Mediterranean Region of Spain shows a progressive displacement from the Querco-Fagetea, typical of Central Europe, towards the Nerio-Tamaricetea, which has its maximum expression in North Africa. We studied the occurrence of 107 riparian plant communities on 52 locations in the Segura River Basin (SE Spain) and their presumed relation to variation in rainfall and temperature. On the basis of agglomerative clustering and Redundancy Analysis (RDA) three riparian vegetation complexes were identified and characterized by (a) Central European-related temperate communities, (b) predominantly North African riparian communities and (c) a combination of both community types, respectively. North African communities predominated in the lower stretches of the Segura Basin, probably due to the prevailing semi-arid bioclimate.