Cenozoic uplift of Variscan Massifs in the Alpine foreland: Timing and controlling mechanisms

The European Cenozoic Rift System (ECRIS) and associated fault systems transect all Variscan Massifs in the foreland of the Alps. ECRIS was activated during the Eocene in the foreland of the Pyrenees and Alps in response to the build-up of collision-related intraplate stresses. During Oligocene and Neogene times ECRIS evolved by passive rifting under changing stress fields, reflecting end Oligocene consolidation of the Pyrenees and increasing coupling of the Alpine Orogen with its foreland. ECRIS is presently still active, as evidenced by its seismicity and geodetic data.Uplift of the Massif Central and the Rhenish Massif, commencing at the Oligocene–Miocene transition, is mainly attributed to plume-related thermal thinning of the mantle–lithosphere. Mid-Burdigalian uplift of the SW–NE-striking Vosges–Black Forest Arch, that has the geometry of a doubly plunging anticline breached by the Upper Rhine Graben, involved folding of the lithosphere. Late Burdigalian broad uplift of the northern parts of the Bohemian Massif reflects lithospheric buckling whereas late Miocene–Pliocene uplift of its marginal blocks involved transpressional reactivation of pre-existing crustal discontinuities. Crustal extension across ECRIS, amounting to no more than 7 km, was compensated by a finite clockwise rotation of the Paris Basin block, up warping of the Weald–Artois axis and reactivation of the Armorican shear zones. Intermittent, though progressive uplift of the Armorican Massif, commencing in the Miocene, is attributed to transpressional deformation of the lithosphere.Under the present-day NW-directed compressional stress field, that came into evidence during the early Miocene and further intensified during the Pliocene, the Armorican Massif, the Massif Central, the western parts of the Rhenish Massif and the northern parts of the Bohemian Massif continue to rise at rates of up to 1.75 mm/y whilst the Vosges–Black Forest arch is relatively stable.Uplift of the Variscan Massifs and development of ECRIS exerted strong controls on the Neogene evolution of drainage systems in the Alpine foreland.     

Late Cenozoic fluvial development within the Sea of Azov and Black Sea coastal plains

Late Cenozoic terrestrial deposits are widespread across the northern coastal regions of the Black Sea and the Sea of Azov and represent diverse fluvial, estuarine and deltaic environments. The dating and correlation of these deposits rely on stratigraphically-associated marine index beds, mammalian and molluscan faunas and magnetostratigraphy. In detail the geometries of these sediment bodies are extremely complex, typically varying between localities and representing many cycles of incision and aggradation. However, the overall disposition of the sediments reflects the transition from the uplifting sediment source region to the north and the subsiding depocentre in the interior of the Black Sea to the south. Since the Middle Miocene the area of the Paratethys/Black Sea depocentre has decreased significantly, but since the Middle Pliocene the hinge zone between uplift and subsidence has been located close to the modern coastline. A combination of regional and local differential crustal movements has given rise to the great variety of fluvial sediment bodies, to the erosion–aggradation cycles, different phases and river activity and to the various fluvial landforms that have all been important in landscape development in this region during the past 12 Ma. The fluvial erosion–accumulation cycles (during the upper Serravillian–Messinian, the Zanclean–late Gelasian, and the Pleistocene) and corresponding cycles of relief dissection and planation are reconstructed against a background of local sea-level changes and climatic variations determined from palaeobotanical data. The maximum fluvial incision occurred in the early Zanclean time with alluvial coastal plains, unique in this area, developing in the Gelasian. Increased climatic aridity during the Pleistocene caused a reduction of fluvial activity in comparison with the Late Miocene and Pliocene. The sea-level oscillations and Pleistocene glaciations affected fluvial processes in different ways. The most remarkable events were the substantial reduction of fluvial activity during the Messinian dessication in the Black Sea and drainage of the shelf, with intensive dissection, coeval with the Last Glaciation.     

A Quaternary uplift record for the Auckland region, North Island, New Zealand, based on marine and fluvial terraces

Marine and fluvial terrace sequences near the Waitakere Ranges on the North Island of New Zealand have been surveyed, yielding an inventory of 13 fluvial and 12 marine terrace levels. Based on sparse tephra age control and correlation with the global palaeoclimatic record, rates of regional Quaternary uplift have been reconstructed. Between 1000 ka and 345 ka the time-averaged uplift rate was 0.072 mm a^− 1, between 345 ka and 50 ka it increased to 0.278 mm a^− 1, accelerating to 0.42 mm a^− 1 since 50 ka. The fluvial terrace sequence did not yield clear sedimentary records or other datable material. However, although others have disputed the existence of marine terraces in this study region, a pattern of accelerating regional uplift, superimposed onto glacio-eustatic sea-level changes, is substantiated as the only possible mechanism for maintaining the considerable relief and the active denudation processes inland. The observed uplift is similar to that in other regions where the uplift has been attributed to coupling between surface processes and lower-crustal flow, making this a likely mechanism in the North Island of New Zealand. Regarding the fluvial terrace sequence, the proposed general model is of an actively incising river, carving out on average one strath terrace every ~ 16,000 years. The incision phases are reactivated by sea-level lowering and interrupted by net aggradation events due to landslides triggered by cyclones and/or fires within the catchment; volcanic ash falls also cause transient increases in sediment supply.     

Coeval argon‐40/argon‐39 ages of moldavites from the Bohemian and Lusatian strewn fields

Abstract— ⁴⁰Ar/³⁹Ar ages of four tektites (moldavites) from southern Bohemia (near ?eské Budějovice, Czech Republic) and a tektite from Lusatia (near Dresden, Germany) have been determined by 11 step‐degassing experiments. The purpose of the study was to enlarge the ⁴⁰Ar/³⁹Ar data base of moldavites and to check the age relations of the Bohemian and Lusatian samples. The mean plateau‐age of the Bohemian samples, which range from 14.42 to 14.70 Ma, is 14.50 ± 0.16 (0.42) (2σ) Ma (errors in parentheses include age error and uncertainty of standard monitor age). The plateau age of the Lusatian sample of 14.38 ± 0.26 (0.44) (2σ) Ma confirms the previously published ⁴⁰Ar/³⁹Ar age of 14.52 ± 0.08 (0.40) (2σ) Ma, and demonstrates that the fall of Lusatian and Bohemian tektites were contemporaneous. Because of their geochemistry and their ages there is no doubt that the Lusatian tektites are moldavites. Accepting that moldavites are ejecta from the Nördlinger Ries impact, the new ages also date the impact event. This age is slightly younger (about 0.2–0.3 Ma) than the age suggested by earlier K‐Ar determinations.     

The relation between productivity and temperature in the Pliocene North Atlantic at the onset of northern hemisphere glaciation: a palynological study

High resolution palynological analysis of DSDP Cores 607/607A shows for the interval between 2.8 and 2.2 Ma B.P. (which includes the onset of major northern hemisphere glaciations) a 41 ka cyclicity characterised by much higher palynomorph concentrations for the cooler intervals than for the warmer ones. Variation in dilution and concentration of palynomorphs can neither be explained by differential input of terrigenous clastics or carbonate, nor by differences in sedimentation rate, sediment density or selective preservation of palynomorphs. Subdivision of the palynomorph record in terms of autochthonous and allochthonous components, provides a way to detect changes in open ocean productivity and transport through time. It seems that a negative correlation between productivity and temperature in the latest Pleistocene open Atlantic had already been established before the major onset of northern hemisphere glaciations. A conceptual model is proposed to explain the observed lead of the palynological record relative to the isotope and carbonate records is proposed. This early response can result from changes in North Atlantic surface ocean circulation induced by changing atmospheric circulation.     

Palaeogeographic evolution of the marine Middle Triassic marine Germanic Basin changements – With emphasis on the carbonate tidal flat and shallow marine habitats of reptiles in Central Pangaea

More than seventy-five vertebrate track-sites have been found in Central Europe in 243–246.5 m.y. old Triassic coastal intertidal to sabkha carbonates. In the western part of the very flat Triassic intracontinental Germanic Basin, the carbonate strata contain at least 22 laterally extensive track horizons (called megatracksites). In contrast, in the eastern part of the basin only six megatracksites extended to near the centre of the Basin during marine low stands. Marine ingression and the development of extensive coastal marine environments began during the Aegean (Anisian) stage. This incursion began in the region of the eastern Carpathian and Silesian gates and spread westward due to the development of a tectonically controlled intracratonic basin. The tectonic origin of this basin made it susceptible to tsunamis and submarine earthquakes, which constituted very dangerous hazards for coastal terrestrial and even marine reptiles. The shallow sea that spread across the Germanic Basin produced extensive tidal flats that at times formed extensive inter-peninsular bridges between the Rhenish and Bohemian Massifs. The presence of these inter-peninsular bridges explains the observed distribution and movement of reptiles along coastal Europe and the northern Tethys Seaway during the Middle Triassic epoch. Two small reptiles, probably Macrocnemus and Hescherleria, left millions of tracks and trackways known as Rhynchosauroides and Procolophonichnium in the Middle Triassic coastal intertidal zone. The great abundance of their tracks indicates that their trackmakers Macrocnemus and Hescherleria were permanent inhabitants of this environment. In sharp contrast, tracks of other large terrestrial reptiles are quite rare along the coastal margins of the Germanic Basin, for example the recently discovered archaeosaur tracks and trackways referable to Isochirotherium, which most probably were made by the carnivore Ticinosuchus. Smaller medium-sized predatory thecodont reptiles, possibly Euparkeria, probably made the Brachychirotherium trackways that have been found across much of Central Europe. Large lepidosaurs such as Tanystrophaeus probably hunted in the tidal ponds and channels, where they locally produced Synaptichnium tracks. Recently discovered tracks made by a basal prosauropod are the world's oldest record of this group of dinosaurs, occurring in beds that have an age of about 243.5 Ma. (Pelsonian substage). This shows that very large prosauropods existed much earlier than was previously believed. These prosauropod tracks, along with tracks of small bipedal dinosaurs found in the Alps and Eastern France, show that by the middle part of the Middle Triassic the radiation and diversification of dinosaurs was already in progress. In the Germanic Basin, aquatic-adapted paraxial swimming sauropterygians are not known to have left tracks, except for occasional subaquatic swimming scratch-mark “trackways” within the coastal tidal flat zone. Marine-adapted aquatic reptiles migrated into the Germanic Basin with increasing frequency in the upper part of the Middle Triassic, when the bathymetry of the Germanic Basin was at its deepest following a strong regression that occurred due to basin uplift in the middle part of the Middle Triassic. These large marine reptiles included Pistosaurus, the ichthyosaurs Cymbospondylus or Mixosaurus, and many placodonts such as Cyamodus, Placodus and Paraplacodus, which fed on macroalgae and seem to have been the Triassic sea cows of their day. The distribution of these reptiles was mainly controlled by tectonics, but eustatic changes in sea level also were important and produced widespread environmental changes across the tidal flats up until their disappearance in the Germanic Basin in the late Middle Triassic. The initial break-up of Pangaea already had started in Middle Triassic time, and this event had begun to drastically change environments all over Central Europe. It is very interesting that dinosaurs began to diversify at exactly this time, and it seems likely that this was a direct reaction to these environmental changes. It can be inferred that the earliest dinosaurs must have started to evolve in the late Early Triassic, because in Europe it can be demonstrated that at least two main dinosaur groups already were present and clearly differentiated by the middle part of the Middle Triassic, and all three of the major groups of dinosaurs (theropods, sauropods and ornithischians) had diversified and spread globally throughout terrestrial habitats by the end of the Triassic Period. Six new palaeogeographic maps, representing time intervals from the Aegean to the Illyrian (Anisian) stages, show these important environmental changes in detail and explain the direction and timing of terrestrial reptile exchanges between the Central Massif, Rhenish Massif, and Bohemian Massif, and also the direction and timing of marine reptile exchanges between the Alps of Central Pangaea and the ancient northern Tethys Ocean and Germanic Basin Sea.     

Cenozoic erosion and sediment yield in the drainage area of the Storfjorden Fan

The western Barents Sea continental margin, between 74° and 77°N, comprises 7–8 km post-Paleocene sediments. The margin sediments have been divided into four seismic sequences dated by seismic correlation to adjacent areas. This chronostratigraphy shows that the uppermost three sequences are of glacial origin, deposited during the last 2.3 m.y. A huge sedimentary wedge, the Storfjorden Fan, was deposited in front of the Storfjorden Trough between 2.3 and 0.44 Ma, whereas during the last 0.44 m.y. a more evenly distribution pattern is observed. The outbuilding of the fan is related to the onset of the northern hemisphere glaciations causing intense glacial erosion of predominantly consolidated rocks. Seismic facies interpretations indicates that the fan outbuilding was connected to large-scale mass movements. Within the uppermost part of the glacial sequence parallel and continuous reflectors and locally disturbed pattern on the upper slope are associated with downslope change in facies. Volumetric calculations, based on velocity studies and isopach maps, have been used to quantify Cenozoic erosion, sediment yield, sedimentation and erosion rates. Approximately 3300 m of post-Paleocene erosion is calculated within the drainage area of the Storfjorden Fan, of which about 1700 m was eroded in late Pliocene-Pleistocene times giving an average denudation rate of 0.63 mm/yr.     

Moldavites from Austria

Abstract— Several moldavites have been discovered in the northern part of Lower Austria. Tektites from two new locations (Altenburg and Radessen) have been analyzed. These new finds lend credibility to old reports about tektites from Lower Austria, some of which are associated with artefacts of prehistoric cultures. The new locations are situated between the Bohemian and Moravian parts of the moldavite strewn field, which is thus shown to extend further south than previously known. Most of the samples show clear indications of surface alterations by water and/or humic substances, and one sample shows signs of fluviatile transport. The geological setting of the moldavite-bearing sediments is similar to the Czechoslovakian occurrences but is probably less disturbed. Chemically the samples show considerable variations even within one location. No unambiguous association with either the Bohemian or the Moravian group is evident either for the major or trace element abundances.     

Tectonic geomorphology of the northern Upper Rhine Graben, Germany

This paper focuses on the northern Upper Rhine Graben (URG), which experienced low tectonic deformation and multiple climate changes during Quaternary times. Recently, human modifications have been high. The paper presents the results of a study into the effects of fault activity on the landscape evolution of the area. The study aims to detect active faults and to determine the last phase of tectonic activity. Information on the long-term tectonic activity is gained from the geological record (drainage system, sediment distributions, fluvial terraces, fault mapping). Previous studies are reviewed and supplemented with new data on tectonic activity. The compilation of all data is presented as a series of paleogeographic maps from Late Miocene to present. It is demonstrated that differential uplift of the western margin of the northern URG had significant impact on the drainage system, the formation of fluvial terraces and the landscape of the western graben shoulder. In a second part of the paper, the imprint of tectonics on the present-day landscape is investigated at the regional scale in order to determine the location of fault scarps and tectonically influenced parts of the drainage system. This study uses an integrated analysis of topography, drainage patterns and fault network. The comparison of features suggests a structural control by numerous NNE- and NNW-oriented intra-graben faults on the flow directions of streams in the Rhine Valley. Several scarps in the Rhine Valley are identified and interpreted to result from intra-graben faulting activity, which in turn controlled fluvial dissection. The third part of the paper presents quantitative measurements of the present-day landscape shape. Calculations of geomorphic indices are used to determine the balance between erosional and tectonic processes and to identify active fault segments. The mountain-front sinuosity and valley shape indices measured along the border faults and in the footwall area are used to determine the level of activity of the faults. Stream profiles of the western and eastern catchments of the River Rhine are investigated for gradient changes at the crossing of the border faults. The combined interpretation of geomorphic indices points to active border fault segments on both sides of the graben. Based on the integration of all results it is concluded that the tectonic morphology identified for the northern URG formed in response to long-term, low level tectonic processes. Due to a significant decrease in erosional and depositional activity during the last 15,000 years, the tectonic morphology has probably been preserved until present.     

The Morávka meteorite fall: 1. Description of the events and determination of the fireball trajectory and orbit from video records

Abstract— The Morávka (Czech Republic) meteorite fall occurred on May 6, 2000, 11:52 UT, during the daytime. Six H5–6 ordinary chondrites with a total mass of 1.4 kg were recovered. The corresponding fireball was witnessed by thousands of people and also videotaped by 3 casual witnesses. Sonic booms were recorded by 16 seismic stations in the Czech Republic and Poland and by one infrasonic station in Germany. A total of 2.5% of the fireball eyewitnesses reported electrophonic sounds. Satellites in Earth orbit detected part of the fireball light curve. In this first paper from a series of 4 papers devoted to the Morávka meteorite fall, we describe the circumstances of the fall and determine the fireball trajectory and orbit from calibrated video records. Morávka becomes one of only 6 meteorites with a known orbit. The slope of the trajectory was 20.4° to the horizontal, the initial velocity was 22.5 km/s, and the terminal height of the fireball was 21 km. The semimajor axis of the orbit was 1.85 AU, the perihelion distance was 0.982 AU, and the inclination was 32.2°. The fireball reached an absolute visual magnitude of ?20 at a height of 33 km.     

Chemical and physical properties of Žďár nad Sázavou L chondrite and porosity differentiation using computed tomography

A very bright and long bolide was observed over the eastern part of the Czech Republic during late local evening on December 9, 2014. This bolide was recorded by professional instruments in the Czech part of the European Fireball Network. Three meteorites weighing in total 87 g were found in the predicted area and were named ??ár nad Sázavou. The complete material composition of the meteorite was obtained from one cut‐off piece using petrography, mineralogy, and scanning electron microscopy (together with X‐ray energy dispersive spectroscopy and wavelength dispersive spectroscopy). X‐ray computed tomography (CT) was applied on all pieces for the determination of their grain and bulk density, digitization of shape, and examination of the structural homogeneity. CT has proved its important role for nondestructive exploration of brecciated meteorites formed by distinct lithologies or petrological types. In this article, we discuss its limits in terms of structural and material resolution based on the correlation of state‐of‐the‐art CT data and SEM images. Furthermore, we introduce a new way of air cavity quantification, which distinguishes the natural porosity of meteorite and cracks related to erosion processes. This helps to discuss the presence of weathering products based on comparison of the meteorite pieces found at different times after impact.     

Deciphering plume–lithosphere interactions beneath Europe from topographic signatures

When a mantle plume rises and impinges on the base of the lithosphere, it expectably produces variations in surface topography. Taking into consideration a realistic mantle rheology, plume ascent rates can reach tens to hundreds of metres per year, whereupon the impingement of the plume head at the base of the lithosphere can be considered as an “impact". Recent numerical experiments based on tectonically realistic formulations for the lithosphere and a representative mantle rheology, have shown that plume-induced undulations exhibit temporal successions of uplift and subsidence at various wavelengths. From spectral (Fourier) analyses of the undulations would appear that two groups of wavelengths (200–400 km and 60–100 km) predominate. Interestingly, a spectral analysis of Europe's topography also reveals two dominant groups. In the present study, we have used a spectral analysis with a wavelet formulation in order to discriminate between tectonically-induced undulations (uni-directional deformation) and plume-induced undulations (omni-directional deformation). The European lithosphere is well-suited for this approach since it has been suggested that two mantle plumes (the Massif Central and the Eifel area) underlie Western Europe, where Alpine compression has folded the lithosphere over several hundreds of kilometres. The wavelet analysis of Europe's surface topography confirms that the energy distribution of the topographic undulations outside the two main volcanic provinces is homogeneous, thus contrasting with the coexistence of both large-scale and medium-scale high-energy features that are obtained for the Massif Central and Eifel areas. Similar signatures are also found beneath the northern Sudetes area. The wavelet approach dedicated to the analysis of plume-related topographic signatures needs, however, detailed theoretical grounds and would probably benefit from two-dimensional analyses.     

The chronology of a large ice-dammed lake and the Barents–Kara Ice Sheet advances, Northern Russia

Beach and shoreface sediments deposited in the more than 800-km long ice-dammed Lake Komi in northern European Russia have been investigated and dated. The lake flooded the lowland areas between the Barents–Kara Ice Sheet in the north and the continental drainage divide in the south. Shoreline facies have been dated by 18 optical stimulated luminescence (OSL) dates, most of which are closely grouped in the range 80–100 ka, with a mean of 88±3 ka. This implies that that the Barents–Kara Ice Sheet had its Late Pleistocene maximum extension during the Early Weichselian, probably in the cold interval (Rederstall) between the Brørup and Odderade interstadials of western Europe, correlated with marine isotope stage 5b. This is in strong contrast to the Scandinavian and North American ice sheets, which had their maxima in isotope stage 2, about 20 ka. Field and air photo interpretations suggest that Lake Komi was dammed by the ice advance, which formed the Harbei–Harmon–Sopkay Moraines. These has earlier been correlated with the Markhida moraine across the Pechora River Valley and its western extension. However, OSL dates on fluvial sediments below the Markhida moraine have yielded ages as young as 60 ka. This suggests that the Russian mainland was inundated by two major ice sheet advances from the Barents–Kara seas after the last interglacial: one during the Early Weichselian (about 90 ka) that dammed Lake Komi and one during the Middle Weichselian (about 60 ka). Normal fluvial drainage prevailed during the Late Weichselian, when the ice front was located offshore.     

Distinguishing between tills from Valdaian ice sheets in the Arkhangelsk region, Northwest Russia

Recent studies in the Arkhangelsk region, northwest Russia, have identified at least three consecutive tills all associated with the last Valdaian (Weichselian) glaciation. The Scandinavian ice sheet deposited a Late Valdaian till (ca. 17 ka BP), whereas two tills were deposited in the Early–Middle Valdaian by the Barents/Kara Sea ice sheet (ca. 45–60 ka BP) and an older ice sheet with an eastern centre (ca. 74 ka BP). This article expands on previous stratigraphical work on the discrimination of regional till units by a combination of compositional characteristics and directional properties. Tills associated with the Scandinavian ice sheet were deposited by a glacier advancing from west or northwest, transporting predominantly material from the Fennoscandian shield and the White Sea area. The Barents/Kara Sea ice sheet moved from the north and northeast, whereas the oldest ice advance came from the east–southeast. Although, the two oldest tills both contain material with an eastern provenance, the Viryuga Till is dominated more by local carbonate-rich material. This study demonstrates that detailed investigation of till units facilitate the distinction of glacial events imperative for the reconstructing of the last glaciation in northern Russia.     

Climate change of the last millennium inferred from borehole temperatures: regional patterns of climatic changes in the Czech Republic — Part III

Accurate temperature–depth profiles may help to assess the temperature variations associated with the climate changes in the past. Ninety-eight ground surface temperature histories inverted from the temperature–depth borehole logs drilled on the territory of the Czech Republic [Bodri, L., ermák, V., 1995. Climate changes of the last millennium inferred from borehole temperatures: results from the Czech Republic — Part I. Global Planet. Change 11, pp. 111–125; Bodri, L., ermák, V., 1997. Climate changes of the last two millennia inferred from borehole temperatures: results from the Czech Republic — Part II. Global Planet. Change 14, pp. 163–173.] are used to reconstruct the regional patterns of the respective climate change. The climate was mapped for the following periods: 1100–1300 A.D. (Little Climatic Optimum), 1400–1500 A.D., 1600–1700 A.D. (main phase of the Little Ice Age), and for the most recent climate trend after year 1960. Comparison of the obtained maps with the meteorological observations and proxy climatic reconstructions confirmed good applicability of the “geothermal” paleoclimatic reconstructions for the regional studies.     

Circumstellar molecular line absorption and emission in the optical spectra of post-AGB stars

We present preliminary results obtained with the European Observation Network. This network consists of 9 observatories in the Czech Republic, Germany and Bulgaria and has been involved in the BACODINE activities since April 1, 1994. We also discuss related problems such as the background of unknown variable stars and suggest a strategy for work in this area.     

Short Time-Scale Variability in the Light Curve of~TW~Draconis

We have re-analyzed old photometric UBV data obtained by Papoušek et al. at Skalnaté Pleso, Slovakia (1967–1980) and Brno, Czech Republic (1976–1979) observatories and analyzed new own CCD measurements (Brno, 2003–2005). In both set of photometric data the oscillations in the vicinity of the primary minimum were found. The detected periods are compatible with the previously published ones.     

European Observation Network: Ground - Based Support for Gamma-Ray Satellites

We present first preliminary results obtained with the European Observation Network consisting of 9 observatories in the Czech Republic, Germany and Bulgaria. We also discuss related problems such as the background of unknown variable stars and suggest a strategy for work in this area.     

Geology of the Selk crater region on Titan from Cassini VIMS observations

Observations of Titan obtained by the Cassini Visual and Infrared Mapping Spectrometer (VIMS) have revealed Selk crater, a geologically young, bright-rimmed, impact crater located ∼800 km north-northwest of the Huygens landing site. The crater rim-crest diameter is ∼90 km; its floor diameter is ∼60 km. A central pit/peak, 20-30 km in diameter, is seen; the ratio of the size of this feature to the crater diameter is consistent with similarly sized craters on Ganymede and Callisto, all of which are dome craters. The VIMS data, unfortunately, are not of sufficient resolution to detect such a dome. The inner rim of Selk crater is fluted, probably by eolian erosion, while the outer flank and presumed ejecta blanket appear dissected by drainages (particularly to the east), likely the result of fluvial erosion. Terracing is observed on the northern and western walls of Selk crater within a 10-15 km wide terrace zone identified in VIMS data; the terrace zone is bright in SAR data, consistent with it being a rough surface. The terrace zone is slightly wider than those observed on Ganymede and Callisto and may reflect differences in thermal structure and/or composition of the lithosphere. The polygonal appearance of the crater likely results from two preexisting planes of weakness (oriented at azimuths of 21° and 122° east of north). A unit of generally bright terrain that exhibits similar infrared-color variation and contrast to Selk crater extends east-southeast from the crater several hundred kilometers. We informally refer to this terrain as the Selk “bench.” Both Selk and the bench are surrounded by the infrared-dark Belet dune field. Hypotheses for the genesis of the optically bright terrain of the bench include: wind shadowing in the lee of Selk crater preventing the encroachment of dunes, impact-induced cryovolcanism, flow of a fluidized-ejecta blanket (similar to the bright crater outflows observed on Venus), and erosion of a streamlined upland formed in the lee of Selk crater by fluid flow. Vestigial circular outlines in this feature just east of Selk’s ejecta blanket suggest that this might be a remnant of an ancient, cratered crust. Evidently the southern margin of the feature has sufficient relief to prevent the encroachment of dunes from the Belet dune field. We conclude that this feature either represents a relatively high-viscosity, fluidized-ejecta flow (a class intermediate to ejecta blankets and long venusian-style ejecta flows) or a streamlined upland remnant that formed downstream from the crater by erosive fluid flow from the west-northwest.     

Climatic implications of correlated Upper Pleistocene glacial and fluvial deposits on the Cinca and Gállego Rivers (NE Spain) based on OSL dating and soil stratigraphy

We correlate Upper Pleistocene glacial and fluvial deposits of the Cinca and Gállego River valleys (south central Pyrenees and Ebro basin, Spain) using geomorphic position, luminescence dates, and time-related trends in soil development. The ages obtained from glacial deposits indicate glacial periods at 85 ± 5 ka, 64 ± 11 ka, and 36 ± 3 ka (from glacial till) and 20 ± 3 ka (from loess). The fluvial drainage system, fed by glaciers in the headwaters, developed extensive terrace systems in the Cinca River valley at 178 ± 21 ka, 97 ± 16 ka, 61 ± 4 ka, 47 ± 4 ka, and 11 ± 1 ka, and in the Gállego River valley at 151 ± 11 ka, 68 ± 7 ka, and 45 ± 3 ka. The times of maximum geomorphic activity related to cold phases coincide with Late Pleistocene marine isotope stages and Heinrich events. The maximum extent of glaciers during the last glacial occurred at 64 ± 11 ka, and the terraces correlated with this glacial phase are the most extensive in both the Cinca (61 ± 4 ka) and Gállego (68 ± 7 ka) valleys, indicating a strong increase in fluvial discharge and availability of sediments related to the transition to deglaciation. The global Last Glacial Maximum is scarcely represented in the south central Pyrenees owing to dominantly dry conditions at that time. Precipitation must be controlled by the position of the Iberian Peninsula with respect to the North Atlantic atmospheric circulation system. The glacial systems and the associated fluvial dynamic seem sensitive to 1) global climate changes controlled by insolation, 2) North Atlantic thermohaline circulation influenced by freshwater pulses into the North Atlantic, and 3) anomalies in atmospheric circulation in the North Atlantic controlling precipitation on the Iberian Peninsula. Our scenario of glacial and fluvial evolution during the Late Pleistocene in northern Spain could be extrapolated to other glaciated mountainous areas in southern Europe.