Upper Oligocene lithostratigraphic units and the transition to the Miocene in North Belgium

The presence of Chattian deposits in Belgium was confirmed in the early 20th century by correlation of their mollusc faunas with the type Chattian in Germany. Consequently, the Voort Formation in the Campine Basin and the Boncelles Sand on the northeastern Ardennes were established and assigned a Chattian age. Contacts with underlying Rupelian and overlying Burdigalian formations are marked by hiatuses, linked mainly to end-Oligocene Savian tectonics and reactivation of the Roer Valley Graben (RVG). On the Campine Block, only the lower part of the Chattian, the Voort Sand is deposited, increasing in thickness in the direction of the RVG and including a geophysically traceable clayey marker horizon allowing the mapping of this unit in the Campine Basin, into the Netherlands and even possibly link it to the hydrostratigraphic subdivision of the Chattian in the Lower Rhine Graben. Lithologically, these uppermost Paleogene Chattian deposits form the base of the Neogene sequence along the Southern Bight of the North Sea, characterised by predominantly glauconite-bearing sand. The Chattian sediments rapidly become thicker in the strongly subsiding RVG, resulting in a more continuous sedimentation with the development above the Voort Sand of a clay unit and another sand unit, forming together the Veldhoven Formation. In Belgium such sequence is only found in the RVG without biostratigraphic data. However, it can be demonstrated that lithostratigraphically this sequence is comparable to the better-studied Veldhoven Formation in the Netherlands where biostratigraphy revealed that the Veldhoven Formation grades into the Aquitanian to Burdigalian, crossing the Paleogene–Neogene boundary and separated from middle Miocene deposits by the Early Miocene Unconformity (EMU). It is proposed to harmonise Belgian and Dutch stratigraphic nomenclatures, making the more complete Veldhoven Formation applicable both in the Campine Basin and the Roer Valley Graben, and further north in the Netherlands. Within this scheme, the Belgian Voort Formation becomes the Voort Member as the lower part of the Veldhoven Formation, of which the middle Wintelre clayey and upper Someren sandy members are only recognised in the graben.

THE AGE OF LOOSE SEDIMENTS AT THE ELISEYEVICHI 1 SITE BASED ON DATING BY THE OPTICALLY STIMULATED LUMINESCENCE METHOD

В статье представлены первые результаты OSL-датирования рыхлых отложений второй надпойменной террасы реки Судости (притока Десны), которые включают культурный слой стоянки Елисеевичи 1. Датировки указывают на то, что формирование культурного слоя происходило относительно быстро в период с 16 до 15 тыс. л. н. В разрезе по результатам датирования не выделяется резких несогласий, перерывов, возрастных инверсий, что может свидетельствовать об относительно непрерывном осадконакоплении. Полученные датировки указывают на поздневалдайский возраст отложений (конец морской изотопной стадии 2) и хорошо коррелируют с полученными ранее по костям мамонта радиоуглеродными датами и оценками возраста на основании изучения палинологии и фауны стоянки. The paper describes the first results of OSL-dating of loose sediments in the second terrace above the flood-plain of the Sudost’ river, a tributary of the Desna river, which include the occupation layer of the Eliseyevichi 1 site. Luminescent dating demonstrates that the formation of the occupation layer occurred relatively quickly in the period from 16,000 to 15,000 years ago. The breakdown by dating results does not reveal any sharp disagreements, disruptions, age-related inversions, which may indicate a relatively continuous sedimentation. The obtained OSL dates indicate the Late Valday age of the deposits (end of the marine isotope stage 2) and well correlate with the radiocarbon dates for mammoth bones obtained earlier and estimates of the age based on palynological and faunal studies at the site

Combining hyperspectral and XRF analyses to reconstruct high-resolution past flood frequency from lake sediments

<p>Due to global climate changes, an intensification of extreme events such as floods is expected in many regions, affecting an increasing number of people. An assessment of the flood frequencies is then a public concern. For several years now, numerous studies are undertaken on geological paleoclimate records and especially on lake sediments to understand the fluctuations of the flood activities in contrasting climatic contexts and over long time periods. Flood events produce turbidity currents in lake basins that will usually lead to a normal graded detrital layer that differs remarkably from the continuous sedimentation. Currently, in an overwhelming majority of studies, once identified, the layers with the same characteristics (e.g. texture, geochemical composition, grain-size) are usually counted by naked-eye observation. Unfortunately, this method is time-consuming, has a low spatial resolution potential and can lead to accuracy bias and misidentifications. To resolve these shortcomings, high-resolution analytical methods could be proposed, as X-ray computed tomography or hyperspectral imaging. When coupled with algorithms, hyperspectral imaging allows automatic identifications of these events.</p><p>Here, we propose a new method of flood layer identification and counting, based on the combination of two high-resolution techniques (hyperspectral imaging and high-resolution XRF core scanning). This approach was applied to one sediment core retrieved from the Lake Le Bourget (French Alps) in 2017. We use two hyperspectral sensors from the visible/near-infrared (VNIR, pixel size: 60 µm) and the short wave infrared (SWIR, pixel size: 200 µm) spectral ranges and several machine learning methods (decision tree and random forest, neural networks, and discriminant analysis) to extract instantaneous events sedimentary signal from continuous sedimentation. The study shows that the VNIR sensor is the optimal one to create robust classification models with an artificial neural network (prediction accuracy of 0.99). This first step allows the estimation of a classification map and then the reconstruction of a chronicle of the frequency and the thicknesses of the instantaneous event layers estimated.  </p><p>High-resolution XRF core scanning (XRF-CS) analyses were performed on the same core with a 200 µm step. Titanium (Ti) and Manganese (Mn) were selected as a high-resolution grain size indicator and a redox-sensitive element that shows abrupt inputs of oxygenated water-related to floods, respectively. Both elements have thus been added to the model in order to refine the chronicle derived from hyperspectral sensors. The combination of both hyperspectral and XRF-CS signal indicator allows to decipher floods from instantaneous deposits (e.g slump). This combined chronicle is in good agreement with the expected frequency obtained from the naked-eye chronicle realized on the same core (r² = 0.8). In this study, we present for the first time, an innovative approach based on machine learning which allows to propose fast automatized flood frequencies chronicles. This work was assessed by traditional deposits observations, but it can be easily applied to very micrometric deposits, undistinguishable to the naked eye. Finally, this model can be implemented with other indicators. It then represents a promising tool not only for flood reconstructions but also for other paleoenvironmental issues.</p>

Complex investigation of Lake Bannoe sediments (South Ural, Russia)

<p>In paper presented results of complex investigations of Lake Bannoe (53°34'40.5"N 58°38'05.0"E) and its sediments. The origin of the Lake is tectonic. Seismoacoustic investigations were carried out for choose the best places for coring with continuous sedimentation and avoid gas saturated sediments. 4 long cores of sediments (up to 5.5 meters) were collected with using special hydraulic corer.</p><p>To study the sediments, a set of methods was used including petromagnetic and paleomagnetic studies, the study of mineralogical and elemental composition. According radiocarbon dating the maximum age of samples is 12.5 thousand. The age of samples increases with depth naturally, which means we have continuous sedimentation without hiatus.</p><p>Measurements of magnetic susceptibility (MS), hysteresis parameters and thermomagnetic analysis were carried out to determine changes in magnetic mineralogy and sedimentation conditions. Thermomagnetic curves measured on Curie express balance, coercitive parameters on J-coercivity spectrometer and magnetic susceptibility on multi-function kappabridge MFK1-FA (AGICO). The elemental composition was studied on an S8 Tiger X-ray fluorescence wave dispersion spectrometer. X-ray diffraction was performed on a Bruker D2 Phaser for studying mineralogical composition.</p><p>Changes in the magnetic susceptibility along the section are not significant, which indicates the constancy of sedimentation conditions. Only lower part, below 4.7 meters, MS increasing which corresponds to big input of terrigenous material. Most common magnetic minerals of sediments are pyrite and magnetite. Main minerals are quartz, albite, mica, from 1.3 meters and below in sediments detected calcite and dolomite.</p><p>Obtained data from all methods (magnetic properties, minerology, elemental composition) used for preliminary paleoclimatic and paleoenvironmental reconstructions of South Ural region for last 12.5 kyr. According petromagnetic data there is no big changes in sedimentation conditions. Also elemental composition shows the same, no big changes. Bottom part of sediments core are consist of more coarse material this is reflected both in magnetic properties and in elemental composition.</p><p>This work was funded by the Russian Science Foundation under grant № 18-17-00251.</p>

Late-Holocene climatic record from a glacial lake in Ladakh range, Trans-Himalaya, India

A multi-proxy study using mineral magnetism, sediment texture, total organic content, palynofacies and diatoms was conducted in one of the highest proglacial lake situated at North Pulu (5098 m a.s.l.) of Ladakh sector of NW Himalaya – a high-altitude cold arid desert. This study presents climatic variations that occurred between 5412 and 419 cal. yr BP (14C AMS chronology). Directly recharged by meltwater from Khardung glacier, this proglacial lake provides a complete record of past climatic variability due to continuous sedimentation and this attribute makes it an exceptionally important geochronological archive for climatic studies. This first high-resolution palaeolimnology record from Karakoram Himalayas shows intermittent warm and cold periods in which the cold events are short but sudden events recorded at 5700, 4600, 4400, 4200, 3800, 3500, 3000, 1800–1700, 1200, 910, 840 and 770–710 cal. yr BP. Between 5412 and 4840 cal. yr BP, an oxic lake condition existed with freeze–thaw action, prominent weathering, more sediment generation and less organic productivity. The following period till 4410 cal. yr BP was cold and dry, a transition phase to the next warmer phase. Between 4410 and 2064 cal. yr BP, climate ameliorated to somewhat moderate warm climate and relatively high lake levels. Glacial melting due to a warm climate resulted in high TOC%, and well-preserved OM indicating reducing conditions in the lake system. From 2064 to 1711 cal. yr BP cold conditions and from 1272 to 1182 cal. yr BP warmer conditions are seen with large appearance in Amphora ovalis indicating increased nutrients input and moderate water levels. This was followed by warmer climatic conditions between 1182 and 958 cal. yr BP. LIA in the region is experienced between 958 and 644 cal. yr BP with anoxic condition. Between 644 and 419 cal. yr BP, climatic condition was again warmer comparatively. However, this warming was not so severe and only had a regional impact.

Historical anthropogenic heavy metal input to the south-eastern North Sea

The Helgoland Mud Area (HMA) in the German Bight, covering an area of approximately 500 km2, is one of a few depocentres for finer sediments in the North Sea. Radiocarbon and 210Pb analyses revealed continuous sedimentation over the last several centuries. Zinc (Zn) and lead (Pb) contents in the sediments show a distinct increase towards the youngest most sediments with the thickness of the heavy metal enriched sediments ranging from 15 to 103 cm. Stratigraphic data indicate that the onset of heavy metal enrichment is diachronous progressing north-westward over the depocentre, paralleled by a decrease in the thickness of the enriched layer. Beginning already during medieval times, the enhanced input of Zn and Pb seemingly is related to silver and zinc mining in the Harz Mountains and the Erzgebirge, well-known mining areas since the Bronze Age. Both regions are directly connected to the HMA by the Elbe and Weser rivers. Zn and Pb enrichment began in the south-eastern HMA and progressed subsequently with an average of 10 m per year north-westward, most likely triggered by variations in river discharge and by the hydrodynamic setting. Quantitative assessments of the Zn and Pb content in the sediments suggest that since the onset of enhanced Zn and Pb deposition, the anthropic Zn and Pb input in the HMA amounts to ~ 12,000 t and ~ 4000 t, respectively.

Ichnostratigraphy of the Ediacaran-Cambrian boundary: new insights on lower Cambrian biozonations from the Soltanieh Formation of northern Iran

Strata in the Central Alborz Mountains, northern Iran, are interpreted to show continuous sedimentation from Ediacaran through Cambrian times. The Soltanieh Formation consists of five members: Lower Dolomite, Lower Shale, Middle Dolomite, Upper Shale and Upper Dolomite members. The clastic units (Lower and Upper Shale members) represent sedimentation in distal marine settings, ranging from the shelf to offshore, and contain abundant trace fossils of biostratigraphic utility. Four ichnozones have been recognized. Ichnozone 1, containingHelminthoidichnites tenuis,Helminthopsis tenuis, andCochlichnus anguineus, is early Fortunian based on small shelly fossils, and is interpreted as a distal expression of theTreptichnus pedumzone. Ichnozone 2, comprising the first occurrence ofT.pedum, is middle Fortunian, and is best regarded as the upper half of theTreptichnus pedumZone. Ichnozone 3 is late Fortunian–Cambrian Age 2, characterized by a sudden change in abundance and complexity of trace fossils. Main elements in this ichnozone includeCruziana problematica,Curvolithusisp., Phycodesisp.,Treptichnus pedum,Treptichnus pollardi, andTreptichnusisp. Ichnozone 4 is of Cambrian Age 2–Age 3 and marked by the first appearances ofPsammichnites gigas,Rusophycus avalonensis, andDidymaulichnus miettensis. Integration of trace fossils with small shelly fossils suggests that the Ediacaran–Cambrian boundary should be placed at the base of the Soltanieh Formation or within the Lower Dolomite Member. The delayed appearance ofT.pedumand the low ichnodiversity in the Lower Shale and lower interval of the Upper Shale reflect limited colonization of settings below storm wave base during the early Fortunian.