Morphostratigraphic Units Research Articles

Late quaternary morpho-stratigraphic record of diapir rise in the Cardona salt extrusion, NE Spain. Halokinetic sequences, raised terraces and uplift rates

Active diapirism has received very limited attention from the geomorphological and Quaternary Science perspective, despite the role played by this ground deformation process in the development of landforms and sedimentary environments, and the important practical implications associated with mobile salt structures (e,g., mining, hydrocarbon production, geostorage). The Cardona salt extrusion (NE Spain) was initiated in late Quaternary times from the post-shortening unroofing of the crest of a salt anticline by the entrenchment of the transverse Cardener River. Detailed mapping, outcrop analysis, geophysical data and trenching indicate that the diapir-flanking deposits show halokinetic complexes comprising two types of morpho-stratigraphic units: (1) an older flap of coarse-grained drapefolded colluvial deposits; and (2) younger lacustrine and fluvial deposits in peripheral depressions confined between the upturned colluvial flaps and the country rock slope. These synkinematic units record an overall relief inversion and correspond to the so-called wedge and hook halokinetic sequences, recording ratios between diapir rise rate and sedimentation rate lower and greater than 1, respectively. The radiocarbon ages obtained from several raised late Holocene strath terraces carved in the salt indicate uplift rates within the range of 36.5–12.1 mm/yr, consistent with geodetic data. The spatial variability of the uplift rates can be related to increasing flow rates towards the axis of the salt wall and potential along-strike variations. The relatively high diapir rise rates observed at Cardona diapir, unaffected by contractional displacement loading (tectonic squeezing), is attributed to the youthful stage of the salt extrusion and the low dynamic viscosity of the Cardona Saline Formation, with a low proportion of impurities and a significant amount of potash salts.

Pedology of archaeological stone-wall bench terraces

Agricultural terraces are the most widespread archaeological landforms worldwide. Despite their far-reaching prevalence in many inhabited parts of the world, archaeological soils in terraces (hereafter ‘terrace soils’) are scarcely studied and their nature is poorly defined. This study aims to depict a space–time framework for the development of calcareous soils in archaeological stone-wall bench terraces and suggest modifications to their soil classification and mapping. To do so, we examined soils at the forefront of five terraces in Catalonia (Spain), that had been previously dated with optically stimulated luminescence to periods from Medieval-Late Middle Ages (1200 ± 60 CE) to Modern (1810 ± 15 CE). Local soils surrounding the terraces are Entisols and Inceptisols in the relatively drier areas and Mollisols in the moister areas. Methods applied are field survey, standard physico-chemical analyses, and soil micromorphology. CaCO3 content, P, OM and CEC show irregularly trending values throughout the profiles. Micromorphology shows abundant content of charred components throughout the profiles and slight discontinuous carbonate recrystallization, mostly biogenic. Based on these observations, the main parent material was determined to be local soil that was redeposited by workforce as fill material for terracing. We further interpret that pedogenesis mainly involved structure development under the influence of anthroturbation and bioturbation, inheritance of ex situ aggregates from parent soil, reaggregation with little occurrence of organic matter, and low levels of lessivage and CaCO3 redistribution. We found that pedogenesis in these terraces started in a chaotic manner, considerably faster than pedogenesis in natural soils, primarily influenced by the act of terracing, the maturity of its inherited parent soil material, and relatively large depth. Therefore, early stages of terrace soil development can differ greatly from known soil models, questioning paradigms of pedogenic ‘time zero’ and ‘maturity’ in terrace soil. We suggest four terrace fill settings for terrace material and propose a model for the state of entropy and development of terrace soils. We classify the studied soils as Archaeo-Anthroportic Xerorthents, (Anthrosols (Calcaric, Escalic)), and Archaeo-Anthroportic Typic Haploxerolls (Anthrosols (Calcaric, Escalic, Relocatic, Anthromollic)), both overlying buried Inceptisols (Cambisols). Our primary conclusion is that terrace soils should be separately classified and mapped by treating terracescapes as distinct morpho-stratigraphic units in which age is the same as the age of their geomorphic surface. This study advances the pedological understanding of archaeological stone-wall bench terraces and identifies gaps in the understanding of terrace soils.

Alluvial plain morphostratigraphy affected by recent mud and debris flows: a study in the Jacareí River basin (southern coast of Brazil)

Sedimentary records are important to understand the evolution of river systems. Morphostratigraphic studies associate sedimentary records with landforms. Mud and debris flows, common in the Serra do Mar mountain range, have a marked impact on the morphostratigraphy of adjacent alluvial plains. The objective of this study was to analyze morphostratigraphic units in an alluvial plain affected by recent mud and debris flows. The study area was the Jacareí River alluvial plain (coast of Paraná State, Brazil) which was hit by extreme gravitational events in March 2011. Geospatial and field survey data were analyzed in a GIS environment to produce a morphostratigraphic map. Units were identified in three contexts: formed earlier than 2011, formed by the 2011 mud and debris flows, and formed after 2011. The deposits instantly formed in 2011 present rocks and pebbles (debris flows) and massive sandy facies (mud flows), with a thickness of between 0.5 and 1 meter. They are easily identified due to abrupt changes in particle size, color, presence of roots, and quantity of organic matter. The results shed light on the evolutionary processes at work in the Jacareí River coastal plain landscape, withthe 2011 event representing a phase of the sedimentary cycle of alluvial plains along the Serra do Mar mountain range.

Glaciations on ophiolite terrain in the North Pindus Mountains, Greece: New geomorphological insights and preliminary 36Cl exposure dating

A glacial geomorphological analysis of three valleys on Mt. Mavrovouni (North Pindus Mountains, Greece) is presented alongside a pilot study using cosmogenic 36Cl to obtain surface exposure ages from iron-rich ophiolite glacial and periglacial boulders. At least three distinct morphostratigraphic units of glacial (moraines) and periglacial (relict pronival ramparts) origin have been identified. Four 36Cl surface exposure ages were obtained from the stratigraphically youngest glacial and periglacial deposits. Although this limited dataset with relatively large uncertainties cannot support a robust geochronology, the ages are consistent with the 36Cl-based chronologies of limestone-derived moraines on Mt. Tymphi (NW Greece) and Mt. Chelmos (S Greece), confirming that the last glaciers on this massif formed during the Last Glacial Maximum as also indicated by other studies in the Pindus mountains. At the same time it provides confidence in the suitability of 36Cl dating for iron-rich samples, such as ophiolites, using an updated 36Cl model that incorporates improved production rates for iron spallation. The presented preliminary chronology of moraines and pronival ramparts is based on those ages as well as on local and regional morphostratigraphic correlations. The stabilisation of the most extensive Late Pleistocene glaciers took place during the Last Glacial Maximum, at 27.0 ± 6.5 ka whereas the presence of pronival ramparts dated at 20.2 ± 4.8 ka suggests persisting cold and arid conditions. Older, still undated glacial deposits exist lower in the valleys which can be attributed to the Middle Pleistocene major glaciation phases (MIS 12/MIS 6), based on their relative morphostratigraphic position within the glacial sedimentary sequence.

Seasonal control on coastal dune morphostratigraphy under a monsoon climate, Mui Ne dunefield, SE Vietnam

Having developed in the later Quaternary Period, the Mui Ne dunefield, representing the upper-most portion of a major coastal barrier complex in SE Vietnam, formed by wind regimes associated with the Asian monsoon climate. The barrier complex is 100 km long and higher than 150 m in elevation but despite its large dimensions, research on its geomorphological and geological characterization is limited. Several active dune fields extend 2–10 km landwards from the coast while the rest of the barrier surface is stabilized. We applied ground-penetrating radar (GPR) and quartz optically-stimulated luminescence (OSL) dating to the transverse dunes of the Mui Ne dunefield to characterize the morphostratigraphy and recent aeolian sedimentation history. Currently the dunes have a relief of typically 5–10 m and a wavelength of 50–100 m. They are driven by the northeasterly winter monsoon winds and reversed with minor relief in response to the southwesterly summer monsoon. GPR profiles and OSL ages define three morphostratigraphic units: the modern, Holocene, and Pleistocene dune units. The GPR data of the modern dune unit is dominated by a series of steep reflections that dip exclusively towards the west reflecting the winter monsoon and is punctuated by reactivation surfaces. Evidence for the wind reversal is not preserved in the sediment successions but is represented by reactivation surfaces. Thus a subunit bounded by the reactivation surfaces defines annual deposition. The preservation potential of a subunit varies with the migration rate of the transverse dune, and in the fastest migrating dunes, approximately one subunit was preserved every year (1.1 ± 0.6 subunit/yr). The modern dunes are generally younger than 100 years and have migrated WSW at net rates of 0.6–2.5 m/yr. The Holocene dune unit is as thick as the modern unit although it spans a period, ten times longer, reflecting the lower preservation potential of the transverse dunes as sedimentary records, due to erosion associated with their migration. The rate of dune migration suggests that an aeolian contribution of coastal sands has occurred following the sea level highstand of the Middle Holocene, accounting for the extent of the active dunefields. This mode of the barrier accumulation is considered as an analogue for earlier highstand events. However, the dunefields only cover a fraction of the entire barrier. It is thus inferred that barrier formation occurred over a long period, probably encompassing several glacial-interglacial cycles. Sand accumulation during the lowstand, either by transport of sand from the subaerially exposed shelf and/or reworking of sand emplaced during the prior highstand, may contribute significantly to the barrier development.

Evaluating Quaternary activity versus inactivity on faults and folds using geomorphological mapping and trenching: Seismic hazard implications

The incorporation of active faults in seismic hazard analyses may have a significant impact on the feasibility, design and cost of major engineering projects (e.g., nuclear facilities, dams), especially when located in the site vicinity. The regulatory definition of active versus inactive fault is generally based on whether the fault has ruptured or not after a specific chronological bound (i.e. fault recency). This work presents a methodology, mainly based on geomorphological mapping and trenching, for determining whether specific faults can be considered as active or inactive. The approach is illustrated through the analysis of several faults located in the Spanish Pyrenees (Loiti, Leyre, La Trinidad, Ruesta faults). The 29 km long Loiti Thrust was included in the Neotectonic Map of Spain as a probable neotectonic structure. Previous works, based on geomorphological investigations, incorporated the 28 km long Leyre Thrust as a significant seismic source in a probabilistic seismic hazard analysis, which challenged the seismic design of nearby large dams. The production of detailed geomorphological strip maps along the faults allowed the recognition of specific sites where the faults are covered by Quaternary deposits. The establishment of chronosequences (pediments-terrace sequences) and the available geochronological data helped identifying the most adequate morpho-stratigraphic units for satisfactorily evaluating fault activity vs. inactivity. The excavation of trenches at the selected sites provided unambiguous information on the presence or lack of deformation in the Quaternary cover overlying the fault, and the origin of scarps (tectonic versus erosional). Trenches were also useful for collecting samples and reliably measuring the relative height of terraces overlain by thick colluvium. The evidence gathered by these methods were complemented with the numerical dating of non-deformed slope deposits covering a fault, the analysis of the longitudinal profiles of old pediment surfaces located in the proximity of a fault, the examination of a cave situated next to a fault searching for speleoseismological evidence, and regional geodetic and seismotectonic data (GPS measurements, earthquake focal mechanisms). The integration of all the data, and especially the trenches dug in non-deformed old terrace deposits (>100 ka) truncating the faults, indicates that the analysed faults can be considered inactive and that previous neotectonic postulations were based on non-valid geomorphological interpretations.

Glacial Geomorphology and Preliminary Glacier Reconstruction in the Jablanica Mountain, Macedonia, Central Balkan Peninsula

Although glacial landforms on the Balkan Peninsula have been studied since the 19th century, only scarce data are available about the extent of the former glaciations in the Central Balkan Peninsula, the transition zone between the Mediterranean and Central Europe. Glacial features of the Jablanica Mt. were mapped, described and classified into morphostratigraphic units. A revised glacio-geomorphological map was produced and glacial landforms were assigned to six morphostratigraphic units. Ten primary and two secondary cirques were identified in the upper parts of the studied valleys, while downstream the valleys were steep and glacially shaped with several glacial steps and thresholds. Cirque and valley morphology indicate that subglacial deepening was limited within the cirques and was more intensive in the valley sections during more extensive glacial phases. The largest reconstructed glaciers were 4.6–7 km long, while the last cirque glaciers were only a few hundred meters long. Using morphostratigraphic data, a glacier reconstruction was carried out for the largest mapped glacial extent. On the basis of glacial geomorphology, a former equilibrium-line altitude (ELA) of ~1800 m and glacier cover of 22.6 km2 were estimated during this stage. The local ELA values were compared to the regional ELA record and enabled to tentatively attribute a MIS 6 age for the reconstructed maximum ice extent in the study area.

Chronology of Quaternary terrace deposits at the locality Hohle Gasse (Pratteln, NW Switzerland)

The Quaternary stratigraphy of the Alpine Foreland consists of distinct terrace levels, which have been assigned to four morphostratigraphic units: Hohere (Higher) Deckenschotter, Tiefere (Lower) Deckenschotter, Hochterrasse (High Terrace) and Niederterrasse (Lower Terrace). Here, we focus on the terrace gravels at Hohle Gasse, SSE of Pratteln near Basel, which are mapped as Tiefere Deckenschotter. Petrographic and morphometric data established from clasts allowed to infer the transport mechanisms and sources of the gravels. Sedimentological analyses indicate that the gravels were transported by a braided river and deposited in a distal glaciofluvial setting. In addition, it can be shown that the majority of the clasts display multiple reworking and only a minority maintained a distinct glaciofluvial shape. Cosmogenic multi-isotope dating using 10Be and 36Cl allowed direct dating of the sediments at the study site. A depth-profile age of $$2 70_{ - 1 90}^{ + 8 30}$$ ka for 10Be was achieved for the deposits at Hohle Gasse. Unfortunately, no age could be modelled from the 36Cl concentrations as the blank correction was too high. Furthermore, this age proves that the studied terrace level should be assigned to the morphostratigraphic unit Hochterrasse.

Terrace formation in the upper Bengal basin since the Middle Pleistocene: Brahmaputra fan delta construction during multiple highstands

AbstractFloodplains, paleosols, and antecedent landforms near the apex of the Brahmaputra fan delta in north‐central Bangladesh preserve cycles of fluvial sediment deposition, erosion and weathering. Together these landforms and their associated deposits comprise morphostratigraphic units that define the river's history and have influenced its channel position and avulsion behaviour through the Late Quaternary. Previously, temporal differentiation within these units has not been sufficient to decipher their sequence of deposition, an important step in understanding the spatial pattern of migration of the Brahmaputra River. Holocene units in this region are fairly well established by radiocarbon dating of in situ organic material, but pre‐Holocene units are considered Pleistocene‐aged if organic material is dated >48 000 year BP (the limit of radiocarbon dating) or the sediments are positioned beneath a prominent paleosol, interpreted as a buried soil horizon that developed during a previous sea level lowstand. In such cases, these morphostratigraphic units have been broadly interpreted as Pleistocene without knowing their absolute depositional ages or relative evolutionary chronology. Here we use detailed sediment analysis to better differentiate morphostratigraphic units at the Brahmaputra's avulsion node, establishing the sequence of deposition and subsequent weathering of these bodies. We then test this relative chronology by luminescence dating of the sands beneath these landform surfaces. This work provides the first absolute depositional age constraints of terrace sediments for the Middle to Late Pleistocene Brahmaputra River and upper Bengal basin. The luminescence ages are complemented by detailed compositional trends in the terrace deposits, including clay mineralogy and the degree of weathering. Together, these newly dated and carefully described morphostratigraphic units reflect eustasy‐driven cycles of terrace development by way of highstand floodplain deposition and subsequent lowstand exposure and weathering, along with active tectonic deformation. Defining this Late Quaternary history of terrace development and position of the Brahmaputra River is a first step toward an integrated understanding of basin and delta evolution over multiple glacioeustatic cycles and tectonically relevant timescales.

Sedimentological and palaeohydrological characterization of Late Pleistocene and Holocene tufa mound palaeolakes using trenching methods in the Spanish Pyrenees

AbstractLakes developed in the inner depressions of tufa mounds are rare geomorphic features and still poorly understood. Sedimentation in this unusual type of endorheic lake with a very restricted catchment area is highly sensitive to environmental and hydrological changes. The Isona tufa mound complex, north‐eastern Iberian Peninsula, is associated with the discharge zone of a confined artesian aquifer and comprises 11 tufa mounds consisting of an annular rimstone enclosing a central depression filled with lake deposits. Data gathered from trenches excavated in four palaeolakes located within three different morphostratigraphic units permitted a precise analysis of the geometrical characteristics and stratigraphic relationships of the deposits and provided a sedimentation model for the Late Quaternary infilling of the spring‐fed lakes. The work illustrates that trenches allow a precise characterization of the stratigraphic arrangements, lateral facies changes and deformation structures, which are not apparent in studies relying solely on borehole records, and facilitate sampling for dating and geochemical analyses. The five sedimentary facies described represent different evolutionary stages of the lakes, including: (i) carbonate‐rich palustrine deposits probably related to periods with strong hydrological seasonality; (ii) massive highly bioturbated organic ooze; (iii) banded organic carbonate‐rich facies associated with an increase in the regional effective moisture; (iv) fine‐grained quartz‐rich aeolian/slope‐wash sediments; and (v) colluvial facies deposited following the desiccation of the lakes located at higher altitudes. Geochemical and sedimentological analyses of the lacustrine sequences provided information on the palaeohydrological evolution of the Isona tufa mound complex and the palaeoenvironmental conditions of the area over the last 28 ka. Radiometric dating suggests that deposition occurred simultaneously at ca 22 ka in palaeolakes situated at different elevations. A drop in the piezometric level prompted by the opening of springs at lower altitudes probably caused the deactivation of the upper springs and the desiccation of the lakes. Arid conditions prevailed in the area during the Late Glacial and the early Holocene (28·0 to 8·5 ka bp). More humid conditions recorded from 8·5 to 4·2 ka and again since 1·7 ka are in accordance with palaeoenvironmental reconstructions available in the Western Mediterranean since the Last Glacial Maximum.

Le site acheuléen d’Erg Tihodaïne : caractéristiques technologiques de l’industrie lithique du Pléistocène moyen (Sahara central, Algérie)

For more than a century, the Acheulian site of Erg Tihodaïne has been the subject of several research works that yielded an abundant lithic material from surface and from the morphostratigraphic unit related to the Middle Pleistocene. Despite the importance of the lithic industry, no overall technological analysis has been conducted so far. In this article, we provide the characteristics of a strategy of lithic production through technological analysis of three series, in an attempt to identify key technical behavior of the Acheulian hominids settled on the former lakeshore of Erg Tihodaïne.

Geological map of the Miocene-Pleistocene successions of the Mejillones Peninsula, Northern Chile

The Mejillones Peninsula (northern Chile) has undergone a complex tectono-sedimentary history from the Miocene onward and is dissected by a network of normal faults that generated three asymmetric half-grabens located in a forearc position with respect to the Chile subduction system. A new 1:50,000-scale geological map of the peninsula, covering an area of ca 800 km2 and based on a detailed facies analysis and field mapping (1:20,000 scale) in conjunction with a comprehensive interpretation of aerial photographs (1:33,000 scale), gives new and updated information about the nature of marine sedimentation and deformation during the Miocene to Pleistocene and permits the geological history of the peninsula during this time period to be reconstructed. An important aspect of organising the Miocene to Pleistocene stratigraphy has been the recognition of three regional allostratigraphic units in the hangingwall basin-fill sediments (the Miocene Caleta Herradura, Pliocene La Portada, and Pleistocene Mejillones alloformations) and two major morphostratigraphic units (PlioMMU and PleiMMU) including extensive flights of Pliocene and Pleistocene marine terraces carved on crestal and flanking areas of adjacent footwall blocks.

DEGLACIATION OF THE DUNGIVEN BASIN, NORTH-WEST IRELAND

This paper describes glacigenic landforms and sediments occurring within the Dungiven Basin, north-west Ireland. It relates them to the pattern and timing of deglacial events within several sectors of the late Midlandian British-Irish Ice Sheet. The distribution, association and sedimentology of relatively well-preserved relict deglacial landforms are used in combination to reconstruct the nature and pattern of déglaciation in the region. An intricate pattern of ice-marginal and topographic control on the formation of glacially fed water bodies within the basin occurred during glacial down-and back-wastage toward icesource areas. The dominant ice masses in the basin retreated west and south-west toward the south Donegal Highlands and Omagh Basin regions (Derrynaflaw Morphostratigraphic Unit). During evacuation of the Dungiven Basin by these ice fronts, the easternmost valleys of the northern Sperrin Mountains were deglaciating south-eastward, in the direction of the Lough Neagh Basin (Banagher Morphostratigraphic Unit). A proglacial lake in the mid-to lower Roe Valley during initial stages of the Derrynaflaw Unit was caused by the impoundment of proglacial drainage by a lobe of Donegal ice occupying the Foyle Basin. Subsequent glaciolacustrine environments in the valleys of the northern Sperrin Mountains were created by the interaction of retreating ice margins with local topography. Local watersheds provided control of water-body elevations as ice margins retreated south and west toward ice-dispersal centres.

Deglaciation of the Dungiven Basin, North-West Ireland

This paper describes glacigenic landforms and sediments occurring within the Dungiven Basin, north-west Ireland. It relates them to the pattern and timing of deglacial events within several sectors of the late Midlandian British-Irish Ice Sheet. The distribution, association and sedimentology of relatively well-preserved relict deglacial landforms are used in combination to reconstruct the nature and pattern of deglaciation in the region. An intricate pattern of ice-marginal and topographic control on the formation of glacially fed water bodies within the basin occurred during glacial down- and back-wastage toward ice- source areas. The dominant ice masses in the basin retreated west and south-west toward the south Donegal Highlands and Omagh Basin regions (Derrynaflaw Morphostrati- graphic Unit). During evacuation of the Dungiven Basin by these ice fronts, the easternmost valleys of the northern Sperrin Mountains were deglaciating south-eastward, in the direction of the Lough Neagh Basin (Banagher Morphostratigraphic Unit). A proglacial lake in the mid- to lower Roe Valley during initial stages of the Derrynaflaw Unit was caused by the impoundment of proglacial drainage by a lobe of Donegal ice occupying the Foyle Basin. Subsequent glaciolacustrine environments in the valleys of the northern Sperrin Mountains were created by the interaction of retreating ice margins with local topography. Local watersheds provided control of water-body elevations as ice margins retreated south and west toward ice-dispersal.

Contextes et âge des nouveaux restes dentaires humains du Pléistocène moyen de la carrière Thomas I à Casablanca (Maroc)

Contexts and age of the new dental human fossils from Middle Pleistocene deposits at Thomas Quarry I (Casablanca, Morocco) – The Thomas Quarry I locality became famous in 1969 with the discovery of a human half-mandible in a cave. From 1988 onwards, modern controlled excavations took place within the framework of the Franco-Moroccan co-operative project “ Casablanca.” The stratigraphy of Thomas I Quarry is complex and represents several major episodes of coastal sedimentation that are dated to the final Lower and early Middle Pleistocene on the basis of a detailed regional lithostratigraphical and microfaciological study and form the Oulad Hamida Morpho-stratigraphic Unit. Within this MSU, some lithostratigraphic units fossilize a polyphase palaeo-shoreline in which caves have developed. A continental sediment series dated to the Middle and Upper Pleistocene on lithostratigraphical and biochronological evidence and by OSL is preserved in the Hominid Cave (GH). The top of the GH general stratigraphy shows a red complex with abundant microfauna (stratigraphic unit 1). Below this, a multilayer dripstone floor interbedded with loose red sands (stratigraphic units 2-3) caps the lower stratigraphic units (4 and 5). Stratigraphic unit 4 contains artefacts, fauna and hominid fossils and rests on collapsed eolianite blocks imbedded in coarse sands which form stratigraphic unit 5 ; this lowermost intertidal unit fossilizes a notch in the polyphase shoreline. The Acheulean lithic assemblage recovered by recent excavations in GH stratigraphic unit 4 is similar to the series collected at the time of the discovery of the first Homo fossil in 1969. It is manufactured mainly on various quartzites available close to the site as pebbles of small to medium size and some blocks as well as a few flint nodules collected in a secondary position from beach deposits. The flint nodules derive from the phosphatic plateau of the Meseta hinterland and were carried to the ocean by wadis. The assemblage consists of chopper-cores (mainly unifacial unidirectional cores with a retouched cutting edge) and cores, semi-cortical flakes obtained by direct and bipolar knapping, along with rare handaxes made from large flakes or from flat pebbles, handaxe-like cores, hammerstones and anvils. Stone knapping was mainly oriented towards flake production and a few handaxes were probably imported to the site. A rich mammalian macrofauna supplemented by the addition of a few reptiles and birds is associated with the lithics in GH stratigraphic unit 4. The abundance and diversity of carnivores attest to their use of the cave. The most common species is a middle-size canid, with enlarged crushing part of the dentition. The fauna indicates an open woodland environment and suggests an age younger than Tighenif in Algeria, but the remoteness of this latter site, its distance from the seashore, and the fact that it is an open-air site may account for some of the differences. Preliminary taphonomic analysis of the megafauna indicates that the carcasses were processed by carnivores. Cut-marks are still absent from this assemblage despite the association with refitted lithic artefacts, which raises the question of any human role in the bone accumulations. Similar cases of accumulations created by humans, carnivores and porcupines have already been described in the Mediterranean area. However, the studied assemblage comes from inside the cave, whereas any human occupation may well have been concentrated closer to the entrance. Geological studies have demonstrated that unit 4 containing the assemblage results from several sedimentary processes having possibly mixed artefacts with bones previously accumulated by predators. Between 1994 and 2005, four teeth of Homo were recovered in stratigraphic unit 4, a right upper premolar (ThI 94 OA 23-24), another right upper premolar (ThI 95 SA 26 no 89), a first left upper incisor (ThI 95 SA 26 no 90) and a left upper premolar (ThI 2005 PA 24 no 107). The teeth are larger than those of modern humans and show moderate to heavy wear Laser ablation ICP-MS dating combining tESR and U-series data for modelling U-uptake has given an US/ ESR age of 501 ka for a human premolar while new OSL measurements yielded an age of 420 ± 34 ka for sediments immediately above the dated tooth and 391 ± 32 ka below. Nevertheless, biostratigraphy and lithostratigraphy point to greater antiquity, towards the base of the Middle Pleistocene. + 94 − 76

Origin and evolution of tufa mounds related to artesian karstic springs in Isona area (Pyrenees, NE Spain)

This work analyses a suite of relict tufa mounds generated by artesian karstic springs in Isona area (Spanish Pyrenees). Geological and geophysical data (seismics and vertical electrical resistivity soundings) indicate that the location of the discharge area in which the spring mounds formed was controlled by (1) a bulge in the axial zone of the anticline that affects the Areny-Montsec aquifer, with the consequent thinning of the overlying confining unit and (2) N-S and E-W trending extensional faults. These uncommon meteogene mounds occur in two stepped morphostratigraphic units that constitute the caprock of a mesa 9 km2 in area. The upper tufa complex is 47 m thick and has yielded several U/Th dates of >350 ka. The obtained U/Th ages for the mounds of lower tufa complex, 10 m thick, range from >350 to 214 ± 11 ka. The sedimentological analysis of the scarce exposures and electrical resistivity profiles show the same morphological and depositional components as those described in geothermal springs: (1) Cylindrical vents; (2) Pools fed by the vents and dammed by annular tufa barriers; (3) Tufa barriers (rimstones) constructed by overflowing waters through vertical accretion and progradation. These rimstones may have overhanging upflow sides. (4) Slope tufa facies with terracettes and microgours.

Stratigraphie und Morphogenese von frühpleistozänen Ablagerungen zwischen Bodensee und Klettgau

Abstract. The stratigraphy and paleogeography of the Deckenschotter (“cover gravels”) of the Rhine glacier system between Lake Constance, the city of Schaffhausen and the Klettgau area (Switzerland, Germany) was revised. This was achieved by means of new surveying and mapping, petrographical analysis und a systematic evaluation of available literature and borehole data. Within the Deckenschotter three morphostratigraphic units can be discerned: (a) Höhere (higher) Deckenschotter, (b) Tiefere (lower) Deckenschotter and (c) Tiefere Deckenschotter, unteres Niveau (lower level). The topographically highest unit, the Höhere Deckenschotter, cannot be subdivided into lithostratigrafic units. The gravels classified as Tiefere Deckenschotter are grouped into two morphostratigraphical units; the altitude difference of the bases of both units is minor. They are, however, separated by an erosional discontinuity caused by a signifi cant rearrangement of the hydrographic network.The older one of the two units (Tiefere Deckenschotter) comprises sediments of at least two depositional phases, separated from each other by a hiatus. There are signs of temperate climatic conditions during the period of non-deposition. The tectonic analysis of the study area showed that in general the altitude of the Deckenschotter was not affected by post-depositional tectonic activity. A tectonic displacement of the Deckenschotter occurrences in the Hegau cannot be ruled out as their topographic position is unusually high compared to equivalent deposits further paleo-downstream. However, this does not affect the proposed morphostratigraphic subdivision. The Upper Rhine Graben system (tectonic lowering) controlled the hydraulic base level and the morphogenesis for both the Deckenschotter occurrences discussed here and those in central northern Switzerland. Therefore, the morphostratigraphic units of both regions can be correlated, even though the number of lithostratigraphic units does not match. In the Höhere Deckenschotter this could be ascribed to an incomplete sedimentary record or a lack of data; on the other hand, this might indicate that the connection Lake Constance – Upper Rhine Graben was established later than the connection Lake Walen – Upper Rhine Graben. In contrast, there is no simple morpho- or lithostratigrafic correlation with the early pleistocene deposits of the German Alpine Foreland, since they are oriented towards and controlled by the Donau river system.

A suburban inter-dike river reach of a large river: Modern morphological and sedimentary changes (the Bratislava reach of the Danube River, Slovakia)

The paper outlines contemporary geomorphic and sedimentary changes (1949–2007) in the suburban inter-dike reach of the Danube River in Bratislava underpinning requirements of its management. The studied river reach represents the right bank inter-dike area of a tectonically determined bend of the Danube River which is about 5 km long with a radius of 1.5 km. The landform and floodplain roughness classification schemes show variations in hydraulic and depositional conditions during flooding. Investigation of landform and floodplain roughness changes and the bank retreat rate is based on the multitemporal interpretation of aerial photographs. Sedimentological analysis of 10 borings and 20 pit exposures helped to delimit the morphostratigraphic units. The process and the rate of the vertical accretion of the modern floodplain were investigated by sedimentological and dendrochronological methods. The behaviour of the study reach is dependent on upstream dams in Austria. Dams produce changes in the suspended load regime and a steady riverbed erosion of 2 to 3.5 cm occurs upstream of the study river reach near the Slovak–Austrian border. The Čunovo dam downstream expediates upstream channel filling in spite of the ongoing channel gravel mining in the Danube channel. This has resulted in channel bed aggradation of about 1 m since 1992. The bank retreat of about 100 m during 1949–2007 was caused by the natural bank erosion processes as well as by channel straightening as a flood control measure for Bratislava. The bank shift resulted in the development of the new levee. The current overbank deposits differ from the older gravels, consisting of a fine-grained alluvium varying in thickness from 0.5 m to 1 m. The lithofacies of three flood deposits (March 2002, August 2002, and September 2007) were examined. Overbank sediments differentiate with distance from the bank and vertically. Suburban settings of the study reach and the flood control measures along with the external forcing (dams) induced changes in channel morphology as well as in floodplain roughness variability. This has resulted in changes in the present floodplain sedimentary conditions, channel forms and biodiversity. The landscape evolved through three distinct evolutionary phases.

The Lower Acheulian site of Ambrona, Soria (Spain): ages derived from a combined ESR/U-series model

The Lower Paleolithic sites of Ambrona and Torralba (Soria, Spain) are often associated with each other because of their proximity although they do not represent the same morphostratigraphic unit. Systematic and extensive excavations were conducted at these sites by an American team during the 1960s and 1980s. Recently (1989–2000), a Spanish team has reactivated the research by initiating a new interdisciplinary project. In the central sector and west of the Ambrona site a stratigraphy has been established with six units from AS1 at the base to AS6 at the surface, corresponding to fluvial–lacustrine deposits in which abundant fauna associated with Acheulian artefacts were found. The most abundant species were elephant, horse, deer and aurochs. Other species like carnivores occur in small numbers only. The lithic assemblage is relatively sparse and consists of a few bifaces, choppers and several flake tools distributed throughout levels AS1 to AS5. The fauna and the lithic industry therefore document human presence at Ambrona during the Middle Pleistocene. In order to verify the presumed antiquity of the Ambrona deposits, horse teeth sampled in levels AS1, AS2 and AS6 were analysed using combined ESR/U-series (US) methods. The samples from the lower levels (AS1 and AS2) underwent a very recent uranium uptake as indicated by the U-series dates, ranging between 5 and 18 ka. In contrast, a more conventional postmortem uranium uptake was observed in the upper level samples (AS6) in the enamel and dentine tissues, while a light U-leaching was observed in the cementum. The combined ESR/U-series dates obtained on these samples suggest a minimum age of approximately 350 ka, contemporaneous of OSI 9 or the end of OSI 11, for the Ambrona site.

A New Ichnogenus for Crustacean Trace Fossils from the Upper Miocene Camacho Formation of Uruguay

Maiakarichnus currani ichnogen. et isp. nov. is a crustacean trace fossil from the Upper Miocene Camacho Formation of Uruguay. This trace fossil is a subspherical chamber preserved in full relief, with numerous thin shafts radiating in a stratigraphically upward direction mainly from its upper part and from the sides. In the Camacho Formation it can be found intergrading with Ophiomorpha and Thalassinoides. Previous (unnamed) findings of similar material are only from the Pamlico Morphostratigraphic Unit (Pleistocene) of North Carolina; these have been interpreted as callianassid brood structures. In this paper we also interpret Maiakarichnus as a brood structure of callianassid origin based on its association with Thalassinoides and Ophiomorpha.