Plio Quaternary Research Articles

The influence of weathering and pedogenesis on the geochemical record of Miocene marls and Plio-Quaternary sediments, Medvednica Mt., Croatia

The geochemical signature of weathering and pedogenesis in a temperate humid climate on two parent material types in the foothills of Medvednica Mt. was studied. Five soil profiles on Miocene marls and three sections of Plio-Quaternary (PlQ) proluvial sediments with overlying soil and weathered material were analyzed. The (clay) mineralogy of all profiles and sections had been determined in previous studies. The chemical composition of the samples was determined by inductively coupled plasma emission spectroscopy (ICP-OES) and inductively coupled plasma mass spectroscopy (ICP-MS). Poorly ordered Fe and Mn oxides were determined in the PlQ sediment and overlying soil samples by atomic absorption spectroscopy (AAS), after oxalate dissolution in the dark. The concentrations and element ratios were used to determine element enrichment/mobility and intensity of chemical weathering, material provenance, and to compare the geochemical signatures with previously obtained clay mineralogy results. Trace elements in the Miocene marls, including rare earth elements (REE), indicate the continental origin of the marl siliciclastic component, while more scattered geochemical data of the PlQ sediments reflect their proluvial/torrential nature. The mass transfer coefficient (τ) for major elements and element ratios of the Miocene marl profiles indicate chemical weathering and pedogenesis of lower intensity. The geochemistry of these samples shows homogeneity within the profiles. In the geochemical signature of the PlQ sections, a chaotic proluvial deposition of the material is visible, as well as the heterogeneity with the overlying soil and weathered material. Overall, the geochemistry results largely support the clay mineralogy of the samples and demonstrate how a multiproxy approach can help test hypotheses about past environments and provide valuable additional information for complex paleoenvironmental studies.

A multiapproach for solving geoarchaeological problems: inferences from Roman gold mining in the Eria Valley (León)

The Eria River valley exhibits one of the largest gold mining complexes in NW Iberia from Roman age. In this study, a geoarchaeological work is presented, combining a multiapproach based on airborne LiDAR remote sensing, descriptive geology and radiocarbon dating. The studied area is characterized by the presence of a mining infrastructure comprised of hydraulic canals driving the water at different levels to the mines. Mining works were associated with Plio Quaternary raña deposits and Quaternary materials consisting of hillside and periglacial deposits, and fluvial terraces. The washing of the gold deposits used the hydraulic force to break up and drag out the sediment, giving rise to three different types of exploitation depending on the characteristics of the different materials. The results shed light on the geological materials exploited and other geographical aspects that conditioned the exploitation techniques. The work contributes to improving the knowledge about Roman gold mining and its geological context in northwest Iberia.

Chemical and isotopic evaluation of groundwater salinization processes in the Djebeniana coastal aquifer, Tunisia

This study aims at identifying the sources and fate of salinity in the Djebeniana basin (Tunisia) aquifers. Groundwater samples from the shallow Plio-Quaternary (PQ) phreatic aquifer and deep Miocene aquifer were analyzed for major/minor ions, trace elements, and stable isotopes of the water molecule (δ18OH2O - δ2HH2O), chlorine (δ37Cl) and bromide (δ81Br). Two clusters of samples with distinct chemical compositions were identified. Cluster I samples correspond to Na–Cl mineralized waters with δ37Cl from −0.3‰ to 0.16‰ and δ81Br from 0.21‰ to 0.39‰. Cluster II samples correspond to Ca–SO4 waters presenting a lower salinity than Cluster I, with δ37Cl from −0.3‰ to 0.09‰ and δ81Br from 0.28‰ to 0.54‰. When plotted in a δ2HH2O vs δ18OH2O graph, most of Cluster I groundwater samples tend to align on a mixing line with seawater whereas Cluster II samples appear to define a local evaporation line. The spatial distribution of samples associated with these clusters allows for evaluating the hydrogeochemical processes associated with groundwater salinization: 1) recent recharge from rainwater dissolving salts and entailing the downward migration of saltwater in the higher reaches of the groundwater flow system, 2) upward leakage of mineralized waters from the deep Miocene aquifer, 3) seawater intrusion in the lower reaches of the coastal aquifer, and 4) ion-exchange reactions prompted by seawater intrusion. A conceptual model of groundwater salinization is proposed as a tool for better managing groundwater resources in the Djebeniana basin.

Chemometrics of the Environment: Hydrochemical Characterization of Groundwater in Lioua Plain (North Africa) Using Time Series and Multivariate Statistical Analysis

This study aims to analyze the chemical composition of Lioua’s groundwater in order to determine the geological processes influencing the composition and origin of its chemical elements. Therefore, chemometrics techniques, such as multivariate statistical analysis (MSA) and time series methods (TSM) are used. Indeed, MSA includes a component analysis (PCA) and a cluster analysis (CA), while autocorrelation analysis (AA), supplemented by a simple spectral density analysis (SDA), is used for the TMS. PCA displays three main factors explaining a total variance (TV) of 85.01 %. Factors 1, 2, and 3 are 68.72%, 11.96%, and 8.89 % of TV, respectively. In the CA, total dissolved solids (TDS) and electrical conductivity (EC) controlled three groups. The elements SO42−, K+, and Ca2+ are closely related to TDS, the elements Na+, Cl−, and Mg2+ are closely related to CE, while HCO3− and NO3− indicate the dissociation of other chemical elements. AA shows a linear interrelationship of EC, Mg2+, Na+, K+, Cl−, and SO42−. However, NO3− and HCO3− indicate uncorrelated characteristics with other parameters. For SDA, the correlograms of Mg2+, Na+, K+, Cl−, and SO42− have a similar trend with EC. Nonetheless, pH, Ca2+, HCO3− and NO3− exhibit multiple peaks related to the presence of several distinct cyclic mechanisms. Using these techniques, the authors were able to draw the following conclusion: the geochemical processes impacting the chemical composition are (i) dissolution of evaporated mineral deposits, (ii) water–rock interaction, and (iii) evaporation process. In addition, the groundwater exhibits two bipolar characteristics, one recorded with negative and positive charges on pH and Ca+ and another recorded only with negative charges on HCO3− and NO3−. On the other hand, SO42−, K+, Ca2+, and TDS are the major predominant elements in the groundwater’s chemical composition. Chloride presence mainly increases the electrical conductivity of water. The lithological factor is dominant in the overall mineralization of the Plio Quaternary surface aquifer waters. The origins of HCO3− and NO3− are as follows: HCO3− has a carbonate origin, whereas NO3– has an anthropogenic origin. The salinity was affected by Mg2+, SO42−, Cl−, Na+, K+, and EC. Ca2+, HCO3−, and NO3− result from human activity such as the usage of fertilizers, the carbonate facies outcrops, and domestic sewage.

Tectonic settings of thePlio–Quaternaryvolcanism in Iran from multidimensional and multielement solutions

Geochemical data for 435 samples of the Pliocene to Quaternary (P–Q) volcanic rocks from Iran, distributed mostly along a NW–SE trending belt, were compiled from 28 papers (12 written in Persian). Until now, the rock nomenclature employed has been inconsistent with the recommendations of the International Union of Geological Sciences (IUGS). Moreover, older bivariate and ternary tectonic discrimination diagrams and only traditional qualitative approaches using Nb and Ta anomalies, have been used to understand the origin and evolution of the P–Q magmas. The P–Q magma and rock types were classified by strictly following the IUGS recommendations. Two geochemometric multidimensional models based on 10 and 16 elements, along with two decision procedures, capable of discriminating 29 fine tectonic settings, were used to document the existence of six tectonic settings in Iran during the P–Q. The rare earth elements indicated that the evolved intermediate and silicic rocks had a significant crustal component in their origin. The quantification of Nb and Ta anomalies in multielement diagrams was used to support the tectonic inferences from the multidimensional geochemometric models.

Plio–Quaternary Structural Evolution of the Outer Sector of the Marche Apennines South of the Conero Promontory, Italy

Some new results and preliminary remarks about the Plio–Quaternary structural and evolutionary characteristics of the outer Marche Apennines south in the Conero promontory are presented in this study. The present analysis is based on several subsurface seismic reflection profiles and well data, kindly provided by ENI S.p.A. and available on the VIDEPI list, together with surface geologic–stratigraphic knowledge of Plio–Quaternary evolution from the literature. Examples of negative vs. positive reactivation of inherited structures in fold and thrust belts are highlighted. Here, we present an example from the external domain of the Marche Apennines, which displays interesting reactivation examples from the subsurface geology explored. The study area shows significant evolutionary differences with respect to the northern sector of the Marche region previously investigated by the same research group. The areal distribution of the main structures changes north and south of the ENE–WSW oriented discontinuity close to the Conero promontory. Based on the old tripartite classification of the Pliocene, the results of this work suggest a strong differential subsidence with extension occurring during the Early Pliocene and principal compressive deformation starting from the Middle Pliocene and decreasing or ceasing during the Quaternary. The main structure in this area is the NNW–SSE Coastal Structure, which is composed of E-vergent shallow thrusts and high-angle deep-seated normal faults underneath. An important right-lateral strike–slip component along this feature is also suggested, which is compatible with the principal NNE–SSW shortening direction. As mentioned, the area is largely characterized by tectonic inversion. Starting from Middle Pliocene, most of the Early Pliocene normal faults became E-vergent thrusts.

Coastal subsidence, destruction layers and earthquakes from an underwater archaeological excavation: Kenchreai, eastern harbour of Roman Corinth, Greece

One of the first underwater coastal archaeological excavations was made in the 1960 in Kenchreai (Cenchreae), eastern harbour of Roman Corinth, Greece, near the Isthmus (Corinth) Canal. This excavation brought to light an Isis temple with a destruction layer containing amongst others, packs of more than 100 precious glass panels of opus sectile, testifying to a hitherto unknown mosaic-type wall decorative technique. Above this destruction layer, indicating a violently disrupted renovation of the temple in circa AD 400, thereafter abandoned, an apsidal Christian chapel was constructed, currently also found quasi-submerged. The excavators, inspired by subsidence of piscinae (fishtanks) and theories for earthquake destruction and decline of Roman Corinth, a prosperous town controlling marine routes and commerce between Eastern Mediterranean and Italy, have explained the environmental and occupation history of Kenchreai in terms of three earthquakes with 2.3 m cumulative subsidence. This theory, however, has been challenged on different grounds. New evidence about the glass panels and detailed evaluation of historical, seismological, archaeological and coastal data revealed an about 1 m seismic subsidence of Kenchreai, most of which occurred during a destructive earthquake in circa AD 400, undoubtedly with serious impacts to Corinth. Identification of the causative fault is not easy because of unfavourable lithology and because Kenchreai is in a tectonically complex environment: at the east edges of the uplifting Corinthian coast (marked by a Roman harbour 4 m above water) and of the Isthmus of Corinth, a Plio–Quaternary uplifted horst, inside an active tectonic graben. Kenchreai represents one of the very few cases of seismic coastal subsidence deriving from archaeological data.

Kinematics of the Havran-Balıkesir Fault Zone and its implication on geodynamic evolution of the Southern Marmara Region, NW Anatolia

ABSTRACTCenozoic convergence, collision and subsequent subduction between African and Eurasian plates are accommodating in overriding Eurasian plate both forming the Aegean extension and the North & East Anatolian fault zones. To understand the kinematic evolution of upper crust, here we provide new paleostress data from the Havran-Balıkesir Fault Zone located at the interaction area between the North Anatolian Fault Zone (NAFZ) and west Anatolian extensional structures. Paleostress reconstructions of fault-slip data reveal that three distinct deformation phases have been experienced in the region. Phase 1 is represented by left-lateral strike-slip faulting with reverse component in the pre-Pliocene period. The Phase 2 is characterized by approximately N–S trending contraction and associated E–W trending extension in Plio–Quaternary, which is spatiotemporally linked to the initiation of NAFZ through the area. The youngest deformation, Phase 3 is attributed to NE–SW trending extension and NW-SE-trending contraction commenced by the Quaternary transpressional tectonics in Southern Marmara Region. These results show that the main contraction axes have been experienced a spectacular anticlockwise rotation (from NW-SE to E-W), which is associated with; (i)the propagation geometry of the NAFZ into the region (ii)slab roll-back and retreat and tearing process on the Aegean subduction system, and (iii)the existence of inherited structures of the İzmir-Balıkesir Transfer Zone.

Plio–Quaternary seismic stratigraphy and depositional history of the Ulleung Basin, East Sea: Association with debris-flow activity

We analyzed multi-channel seismic reflection profiles to decipher the Plio–Quaternary stratigraphic architecture and resolve the depositional history of the Ulleung Basin. A detailed seismic stratigraphic interpretation revealed nine seismic units (Units 1–9) separated by unit boundaries in the Plio–Quaternary deposits of the Ulleung Basin. Unit 1 (Pliocene) is dominated by debris-flow deposits (DFDs) throughout the basin. Units 2–9 (Quaternary) are characterized by stacked DFDs interbedded with thin hemipelagic sediments along the southern slope, whereas the northern basin floor is filled with hemipelagic and pelagic sediments. The areal distribution and dimensional characteristics of the DFDs indicate that sedimentation in the Ulleung Basin has been controlled by a combination of tectonic movement, eustatic changes in sea level, and gas hydrates dissolution and dissociation. During the Pliocene (Unit 1), sedimentation was mainly controlled by tectonic movements, causing margin-wide slope failures under the compressional regime. Large sediment deposits were supplied to the basin through mass-transport processes, resulting in an abundance of DFDs throughout the basin. During the Quaternary (Units 2–9), compressive stress decreased sharply, causing the DFDs to retreat landward. At that time, sedimentation was mainly influenced by eustatic changes in sea level and gas hydrates dissolution and dissociation. As the sea fell to the lowstand, slope failures were activated by the generation of high pore-water overpressure and the generation of weak layers in the sediments, resulting in stacked DFDs. However, as the sea level rose to the highstand, sediment was primarily deposited via hemipelagic and pelagic processes due to increased hydrostatic pressure and slope stability.

The Crati River Basin: geomorphological and stratigraphical data for the Plio–Quaternary evolution of northern Calabria, South Apennines, Italy

Abstract In this paper, we present the results of an integrated geomorphological and stratigraphical study carried out in the eastern side of the Crati River valley (northern Calabria, South Italy). This area is characterized by the occurrence of three order palaeosurfaces that, along with low-sloping palaeovalleys and structural landforms, are striking features of the landscape. The relationships between morpho-tectonic and sedimentary evolution of the Crati Basin has been assessed through sandstone detrital modes, morphostratigraphy and geomorphological correlation with adjacent areas. The two main unconformity surfaces that typify the Quaternary fill were correlated to different steps of landscape evolution. The presence of both erosional and depositional palaeosurfaces has been a useful marker for reconstructing sedimentary and morphogenetic events, and hence to detect drainage network evolution and changes in source sediment area. In particular, we recognized that the study area experienced, during the late Pliocene–Early Pleistocene a period of sub-aerial landscape modelling as suggested by low-sloping palaeovalleys and related fluvial deposits (1st Order Palaeosurface). At that time, the source of the detrital constituents of the PPS Unit sandstones was mainly from the Sila Massif. The onset of Coastal Range identification and uplift (Early Pleistocene) marks a change in the geomorphic scenario with tectonic driven stream incision and valley development along the eastern side of Coastal Range, along with the occurrence of depositional and erosional landsurfaces (2nd Order Palaeosurface) at footslopes. During this period, the Coastal Range and Sila Massif were the sources for the detrital constituents of the PlS Unit sandstones. The progressive uplift of Coastal Range during late Early Pleistocene and the marked backstepping of the depositional systems along the Sila footslope was accompanied by alternating phases of down-cutting and base-level stability resulting in the development of a step-like distributed 3rd Order Palaeosurface. The presence of dolostone in detrital modes is clear evidence of stream piracy phenomena of ancient palaeovalleys by the Crati valley-facing drainage network.

Seismic imaging of Late Miocene (Messinian) evaporites from Western Mediterranean back-arc basins

An analysis of multichannel seismic reflection data was conducted focusing on the comparison between the Messinian Salinity Crisis (MSC) and Plio-Quaternary (PQ) evolution of the eastern Sardo-Provençal and northern Algero-Balearic basins and related margins in the West Mediterranean Sea. Both basins were completely opened during the MSC and their well-defined seismic stratigraphy is very similar in the deep parts. The primary difference between these two basins is due to their different pre-MSC extensional history, including the opening age and the stretching factors. These factors influenced the occurrence of post-MSC salt tectonics on these margins.

Strength of the Iberian intraplate lithosphere: Cenozoic deformations and seismicity

Previous studies about the strength of the lithosphere in the center of Iberia fail to resolve the depth of earthquakes because of the rheological uncertainties. Therefore, new contributions are considered (the crustal structure from a density model) and several parameters (tectonic regime, mantle rheology, strain rate) are checked in this paper to properly examine the role of lithospheric strength in the intraplate seismicity and the Cenozoic evolution. The strength distribution with depth, the integrated strength, the effective elastic thickness and the seismogenic thickness have been calculated by a finite element modelling of the lithosphere across the Central System mountain range and the bordering Duero and Madrid sedimentary basins. Only a dry mantle under strike-slip/extension and a strain rate of 10-15 s-1, or under extension and 10-16 s-1, causes a strong lithosphere. The integrated strength and the elastic thickness are lower in the mountain chain than in the basins. This heterogeneity has been maintained since the Cenozoic and determine the mountain uplift and the biharmonic folding of the Iberian lithosphere during the Alpine deformations. The seismogenic thickness bounds the seismic activity in the upper–middle crust, and the decreasing crustal strength from the Duero Basin towards the Madrid Basin is related to a parallel increase in Plio–Quaternary deformations and seismicity. However, elasto–plastic modelling shows that current African–Eurasian convergence is resolved elastically or ductilely, which accounts for the low seismicity recorded in this region.

Kinematic analysis and palaeoseismology of the Edremit Fault Zone: evidence for past earthquakes in the southern branch of the North Anatolian Fault Zone, Biga Peninsula, NW Turkey

The Edremit Fault Zone (EFZ) forms one of the southern segments of the North Anatolian Fault Zone (NAFZ) at the northern margin of the Edremit Gulf (Biga Peninsula, South Marmara Region, Turkey). Stratigraphic, structural and kinematic results indicate that basinward younging of the fault zone, in terms of a rolling-hinge mechanism, has resulted in at least three discrete Miocene to Holocene deformational phases: the oldest one (Phase 1) directly related to the inactive Kazdağ Detachment Fault, which was formed under N–S trending pure extension; Phase 2 is characterised by a strike-slip stress condition, probably related to the progression of the NAFZ towards the Edremit area in the Plio–Quaternary; and Phase 3 is represented by the high-angle normal faulting, which is directly interrelated with the last movement of the EFZ. Our palaeoseismic studies on the EFZ revealed the occurrence of three past surface rupture events; the first one occurred before 13178 BC, a penultimate event that may correspond to either the 160 AD or 253 AD historical earthquakes, and the youngest one can be associated with the 6 October 1944 earthquake (Mw = 6.8). These palaeoseismic data indicate that there is no systematic earthquake recurrence period on the EFZ.

“High resolution seismic imaging of an active fault in the eastern Guadalquivir Basin (Betic Cordillera, Southern Spain)”

We calculated the high resolution seismic velocity, Poisson's ratio, crack density and saturation ratio structures in and around the source areas of the Torreperogil seismic series (October 2012–April 2013). This seismic series, characterized by a large number of low magnitude (below Mw 3.7 or Md 3.9) and very shallow microearthquakes, took place in the Guadalquivir Basin, a large flexural foreland basin with a linear ENE–WSW trending bounded to the north by the Iberian Massif and to the south by the Betic Cordillera and filled from a middle Miocene to Plio–Quaternary sedimentary sequence.In the upper layers of the crust, strong low-velocity anomalies are extensively distributed under the central zone, which together with high Poisson's ratio and crack density values may correspond to rocks which are less likely to fracture, perhaps due to the accumulation of tectonic and seismic stress. 93% of the earthquakes occurred at depths of up to 8km, which could indicate that the base of the seismogenic zone lies at this depth. The seismic series was concentrated in layers of strong structural heterogeneities (in the boundary area between low and high anomalies), which were likely to generate earthquakes due to differential strain accumulation beneath the region. The high velocity areas are also considered to be strong yet brittle parts of the fault zone, which may generate earthquakes (at depths of between 5km and 9km). By contrast, low velocity areas are less prone to fracture, allowing seismic slippage to take place (from 2 to 4km depth).The best estimate of the depth of the main shock (mbLg 3.9) is 7.6km, which could tend to nucleate at the base of the seismogenic zone, at the “fault end” on the boundary between a low velocity zone to the east and a high velocity zone to the west, indicating the fault plane which separates both areas laterally. Assuming that this seismic contrast is one of the main Torreperogil faults it could imply that stress has accumulated in an existing fault zone with lateral heterogeneity in velocity.

Three-dimensional approach to understanding the relationship between the Plio–Quaternary stress field and tectonic inversion in the Triassic Cuyo Basin, Argentina

Abstract. The Cacheuta sub-basin of the Triassic Cuyo Basin is an example of rift basin inversion contemporaneous to the advance of the Andean thrust front, during the Plio–Quaternary. This basin is one of the most important sedimentary basins in a much larger Triassic NNW-trending depositional system along the southwestern margin of the Pangea supercontinent. The amount and structural style of inversion is provided in this paper by a three-dimensional approach to the relationship between inversion of rift-related structures and spatial variations in late Cenozoic stress fields. The Plio–Quaternary stress field exhibits important N–S variations in the foreland area of the southern Central Andes, between 33 and 34° S, with a southward gradual change from pure compression, with σ1 and σ2 being horizontal, to a strike-slip type stress field, with σ2 being vertical. We present a 3-D approach for studying the tectonic inversion of the sub-basin master fault associated with strike-slip–reverse to strike-slip faulting stress regimes. We suggest that the inversion of Triassic extensional structures, striking NNW to WNW, occurred during the Plio–Pleistocene in those areas with strike-slip–reverse to strike-slip faulting stress regime, while in the reverse faulting stress regime domain they remain fossilized. Our example demonstrates the impact of the stress regime on the reactivation pattern along the faults.

Genetic framework of Neogene–Quaternary basin closure process in central Turkey

Central Turkey represents the only orogenic plateau in the Mediterranean region. Also, the largest closed drainage basin and the largest intracontinental basin of Turkey, the Lake Tuz Basin, is located in this region. Results from a three-dimensional (3-D) computer modeling study of the Lake Tuz Basin indicate a southward-deepening freshwater lake basin with great depth in the Mio–Pliocene, which regressed toward the north during the Plio–Quaternary into the shallow saline lake basin it is today. The spatio-temporal variations of Neogene and Quaternary deposits reflect the main effects of internal forces (isostasy>volcanism>faulting) that were caused by lithospheric slab breakoff and subsequent asthenospheric upwelling under central Turkey. Climatic change played a relatively minor role during these periods and was closely associated with the results of internal forces.

Use of geochemical, isotopic, and age tracer data to develop models of groundwater flow: A case study of Gafsa mining basin-Southern Tunisia

Hydro-(major and trace elements: Cd, F and Sr), isotope (18O, 2H, 3H and 13C) geochemistry and radiogenic carbon (14C) of dissolved inorganic carbon (DIC) were used to investigate the sources of groundwater contamination and the hydrodynamic functioning of the multilayer aquifer system in the mining Gafsa basin (Southwestern Tunisia). The groundwater of the study area is subject to intense exploitation to accommodate all the water demands of this arid area. The Gafsa basin contains a multi-layered aquifer with four principal levels: Upper Zebbag (Cenomanian–Turonian), Abiod (Campanien–Maastrichian), Beglia (Miocene) and Segui (Plio–Quaternary) Formations. The hydrogeology of this system is largely affected by tectonics (Gafsa–Tebessa, Sehib, Negrine–Tozeur, Tabeddit and Metlaoui faults…). The groundwater of these aquifers undergoes a significant decline in water level (≈0.5my−1), increasing salinity (TDS increase from 400 to 800–6000mgl−1: generally, TDS increases from the mountainous regions towards the discharge area) due to a long time of aridity, irregular rainfall and overexploitation (irrigation and industrial activities). Groundwater pumped from the semi-confined Complex Terminal (C.T) aquifers (Cretaceous and Mio-Plio-Quaternary: MPQ) and from the confined Continental Intercalaire (C.I) aquifers is an important production factor in irrigated oases agriculture and phosphate washing in Southwestern Tunisia. A rise in the groundwater salinity has been observed as a consequence of increasing abstraction from the aquifer during the last few decades. The salinization phenomena in the region are complex. Several possible causes for salinization exist: (1) the upwelling of saline and “fossil” water from the underlying, confined “C.I” aquifer; (2) as well as the backflow of agricultural drainage water; (3) phosphate and domestic wastewater; (4) brine intrusion from the salt lake (Sebkha/Garaat); (5) evaporate meteoric water dams (El Khangua and El Oudeï); (6) reduced rainfall and (7) land and air alterations. The istopic study of waters establishes that the deep groundwater is “fossil” water (6000–37,000years) recharged probably during the late Pleistocene and the early Holocene periods. The relatively recent water in the MPQ aquifer is composed of mixed waters resulting presumably from upward leakage from the deeper groundwater.

Environmental isotopes as the indicators of the groundwater recharge in Tunisian Chotts region

Hydrogeological investigations in arid zones tend to be logistically difficult and costly. However, isotopic techniques can be used to gain valuable reconnaissance information, for example, in advance of new drilling programmes and also during exploitation. Thus, the most cost-effective exploration in arid zones will include both good hydrogeological data combined with isotopic and supporting geochemical information. The question of recharge is one of the most critical for groundwater management in dry areas. Is the recharge currently taking place and at what rate? If recharge is occurring, further important problems arise dealing with possible mechanisms of recharge, which may occur through direct infiltration, upward leakage, lateral recharge from areas of rainfall, and lateral seepage of river (Fontes and Edmunds, Technical documents in hydrology 77, 1989). In this study, which is of interest for an important aquifer system in southern Tunisia, conjunction of environmental isotopes, i.e.: 18O, 2H, 3H, 14C and 13C and chloride contents was used to understand the mode of recharge of the shallow Plio-Quaternary (PQ) and the intermediate Complexe Terminal (CT) aquifers. Both are unconfined in the vicinity of the Tozeur uplift and the Dahar upland and show relatively modern water that originated from present-day rainfall. It has been demonstrated that the Continental Intercalaire deep groundwater contributes to the CT aquifer recharge, the latter to the upper PQ shallow aquifer. The shallow PQ is mainly recharged by return flow irrigation and upward leakage in oases areas. Away from oases zones, sporadic recharge may occur at the inter-dunes especially between the Chott Djerid and Chott El Gharsa, in the Bir Roumi region and in the Kebili sand fields.

Bimodal Plio–Quaternary glacial erosion of fjords and low-relief surfaces in Scandinavia

Glacial landscapes exhibit both high- and low-relief land surfaces. A comparison of fjord erosion and offshore deposition suggests that glacier erosion created both the dramatic fjords and high-elevation low-relief surfaces in western Scandanavia.

Structural evidence for strike-slip deformation in the İzmir–Balıkesir transfer zone and consequences for late Cenozoic evolution of western Anatolia (Turkey)

The İzmir–Balıkesir transfer zone (İBTZ) is a recently recognized strike-slip dominated shear zone that accommodates the differential deformation between the Cycladic and Menderes core complexes within the Aegean Extensional System. Here, we present new structural and kinematic data obtained from field observations and 1/25,000 scale mapping of Miocene to Recent units within the İBTZ around İzmir Bay. The results point out that the İBTZ is a transtensional brittle shear zone that affects the pre-Neogene basement rock units, the early-middle Miocene volcano-sedimentary units and the Plio–Quaternary continental units.The analysis of large-scale structures and fault kinematic data indicate that three different deformation phases prevailed in the İzmir Bay region during the late Cenozoic. The first phase (Phase 1) is characterized by N–S directed extension and E–W contraction that gave way to the development of strike-slip faults with normal components and likely took place during the early (?) to late Miocene. This transtensional phase, forming the volcano-sedimentary basin of deposition was overprinted by the second phase (Phase 2) which is characterized by variable extension and contraction directions indicating wrench- to extension-dominated transtension. The structures related to Phase 2 are observed all around the İzmir Bay and indicate a distributed nature of the deformation that probably took place during the early Pliocene, coeval with the end of the activity of the Mid-Cycladic Lineament and the last exhumation of the central Menderes Massif. The latest deformation phase (Phase 3) is characterized by an association of NW–SE trending left-lateral and NE–SW trending right-lateral strike-slip faults and E–W trending normal faults forming transtensional deformation. During Phase 3, the İBTZ evolved from a wider shear zone into a relatively narrow discrete fault zone by the late Pliocene, during which the strike-slip and extensional deformation were completely decoupled from each other. The field-based evidence for strike-slip deformation from the region has only recently been recognized, but has very important implications for understanding the deformation styles and coupling of Aegean–West Anatolian extensional deformation system along the İBTZ. We conclude that the İzmir Bay Basin developed during the Plio–Quaternary within the dextral İBTZ.