From the Allerød to the mid-Holocene: Palynological evidence from the south basin of the Caspian Sea

This article has been made available through the Brunel Open Access Publishing Fund. Copyright @ The Authors. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-No Derivative Works License, which permits non-commercial use, distribution, and reproduction in any medium, provided the original author and source are credited.Pollen and dinoflagellate cysts have been analysed in a core from the south basin of the Caspian Sea, providing a picture of respectively past vegetation and water salinity for the Late Pleistocene to middle Holocene. A relatively sharp lithological change at 0.86 m depth reflects a shift from detrital silts to carbonates-rich fine silts. From this depth upwards, a Holocene chronology is built based on ten radiocarbon dates on ostracod shells and bulk carbonates. From the vegetation point of view, the Late Pleistocene deserts and steppes were partially replaced in the most sheltered areas by an open woodland with Pinus, Juniperus-Hippophae-Elaeagnus and even Alnus-Quercus-Pterocarya and Fraxinus, related to the Allerød palynozone. This was interrupted by the Younger Dryas palynozone when Artemisia reaches a maximum in a first instance followed by a very dry phase with only a slight return of Pinus and Quercus and the rare presence of Ulmus-Zelkova. From 11.5 to 8.4 cal. ka BP, an open landscape dominated by shrubs such as Ephedra and progressively increasing Quercus appeared. The final spread of diverse evergreen and deciduous trees is delayed and occurs after 8.4 cal. ka BP. It is suggested that this delay is caused by an arid climate in the Early Holocene linked to high insolation and perhaps to a lake effect. The dinocyst assemblages fluctuate between slightly brackish (Pyxidinopsis psilata and Spiniferites cruciformis, 7 psu and lower) and more brackish (Impagidinium caspienense, ∼13 psu). In the Lateglacial (Khvalynian highstand), the assemblages remained dominated by relative low salinity taxa. A late and brief increase of salinity occurred prior to 11.2 cal. ka BP associated with the Mangyshlak lowstand. It is suggested that it was caused by a brief drop in meltwater flow from both the north and the southeast (Uzboy) and a likely evaporation increase. This lowstand occurs quasi at the same time as the end of a longer lowstand in the Black Sea. The freshest waters are then inferred as having occurred between 8.4 and ≤4.4 cal. ka BP, linked to a connection with the Amu Darya and the melting glaciers on the Pamir Mountains. The Caspian Sea is a sensitive environment, easily perturbed by global climatic changes, such as the Allerød and Holocene warming, and the Lateglacial and Younger Dryas cooling, as well as by regional changes in its hydrography, such as shifts in the Eurasian meltwater and the Volga and Amu Darya inflows.Centre National de la Recherche Scientifique, Franc

The Ponto-Caspian basin as a final trap for southeastern Scandinavian Ice-Sheet meltwater

This paper provides new data on the evolution of the Caspian Sea and Black Sea from the Last Glacial Maximum until ca. 12 cal kyr BP. We present new analyses (clay mineralogy, grain-size, Nd isotopes and pollen) applied to sediments from the river terraces in the lower Volga, from the middle Caspian Sea and from the western part of the Black Sea. The results show that during the last deglaciation, the Ponto-Caspian basin collected meltwater and fine-grained sediment from the southern margin of the Scandinavian Ice Sheet (SIS) via the Dniepr and Volga Rivers. It induced the deposition of characteristic red-brownish/chocolate-coloured illite-rich sediments (Red Layers in the Black Sea and Chocolate Clays in the Caspian Sea) that originated from the Baltic Shield area according to Nd data. This general evolution, common to both seas was nevertheless differentiated over time due to the specificities of their catchment areas and due to the movement of the southern margin of the SIS. Our results indicate that in the eastern part of the East European Plain, the meltwater from the SIS margin supplied the Caspian Sea during the deglaciation until ∼13.8 cal kyr BP, and possibly from the LGM. That led to the Early Khvalynian transgressive stage(s) and Chocolate Clays deposition in the now-emerged northern flat part of the Caspian Sea (river terraces in the modern lower Volga) and in its middle basin. In the western part of the East European Plain, our results confirm the release of meltwater from the SIS margin into the Black Sea that occurred between 17.2 and 15.7 cal kyr BP, as previously proposed. Indeed, recent findings concerning the evolution of the southern margin of the SIS and the Black Sea, show that during the last deglaciation, occurred a westward release of meltwater into the North Atlantic (between ca. 20 and 16.7 cal kyr BP), and a southward one into the Black Sea (between 17.2 and 15.7 cal kyr BP). After the Red Layers/Chocolate Clays deposition in both seas and until 12 cal kyr BP, smectite became the dominant clay mineral. The East European Plain is clearly identified as the source for smectite in the Caspian Sea sediments. In the Black Sea, smectite originated either from the East European Plain or from the Danube River catchment. Previous studies consider smectite as being only of Anatolian origin. However, our results highlight both, the European source for smectite and the impact of this source on the depositional environment of the Black Sea during considered period

L’assemblage faunique des localités paléonto-archéologiques de la zone Quranwala, Pliocène final, formation de Masol, chaîne frontale des Siwaliks, Nord-Ouest de l’Inde

Le programme de recherche franco-indien « Siwaliks » poursuit ses investigations dans la zone Quranwala de la formation de Masol, connue depuis les années 1960 pour sa faune de la fin du Pliocène, également nommée faune de transition Plio-Pléistocène. Notre étude paléontologique s’est imposée à la suite de la découverte de traces de découpe sur des fossiles proches de choppers et d’éclats en quartzite. Neuf campagnes de terrain (2008–2015) sur 50 hectares de paysage particulièrement accidenté (ravins et petits plateaux) ont permis d’identifier 12 localités où au moins un chopper était mêlé à des fossiles, lesquels totalisent 1500 spécimens. Leur étude montre que les mammifères les plus abondants sont les Proboscidiens, avec Stegodon insignis et Elephas en bien moins grand nombre. Les bovidés présentent la plus grande variété, avec six tribus de la plus petite à la plus grande taille. Hexaprotodon sivalensis vient en troisième position. Sivatherium giganteum est visible dans plusieurs localités, Merycopotamus dissimilis dans une seule. Deux types de cervidés au moins ont été observés. La faune de transition est attestée par la co-existence de Stegodon et Elephas hysudricus, d’Hipparion antelopinum et d’Equus sivalensis. Les fossiles de tortues sont abondants avec la forme terrestre géante Colossochelys, et celle d’eau douce, Geoclemys. En comparaison, les prédateurs sont peu représentés (crocodile), voire rares (hyène, félin), tandis que les primates (Procynocephalus) n’ont pas encore été observés. L’assemblage faunique correspond bien aux faunes de transition Plio-Pléistocène également décrites dans les Pabbi Hills (Pakistan) ; elle caractérise le début de la biostratigraphie de la zone intervalle Equus sivalensis, qui s’étend de 2,6 Ma à 600 ka. La répétition systématique des prospections a donc permis la collecte de taxons rares comme Crocuta (2010), Merycopotamus dissimilis (2014) et un grand félin (2015). Ces derniers résultats sont significatifs pour la découverte d’ Homininae dans les Siwaliks.The Indo-French Program of Research ‘Siwaliks’ carried out investigations in the ‘Quranwala zone’ of the Masol Formation (Tatrot), Chandigarh Siwalik Range, known since the 1960s for its “transitional fauna”. This new paleontological study was implemented following the discovery of bones with cut marks near choppers and flakes in quartzite collected on the outcrops. Nine fieldwork seasons (2008–2015) on 50 hectares of ravines and a small plateau recovered lithic tools and fossil assemblages in 12 localities with approximately 1500 fossils. Their study shows that the most abundant mammal species are the Proboscideans with Stegodon insignis . The transition with the Pleistocene fauna is evidenced by Elephas hysudricus, Hipparion antelopinum and Equus sivalensis. The freshwater mammal is also well illustrated with Hexaprotodon sivalensis. Bovids present the greatest variety with six tribes from the smallest to the largest. Two types of cervids are observed; Sivatherium giganteum is visible in several localities and Merycopotamus dissimilis in one. Turtles, with the giant terrestrial Colossochelys and the freshwater Geoclemys , are abundant. The aquatic predators are limited (crocodile) and terrestrial carnivores are very scarce (hyena, felid). The faunal assemblages match the Plio-Pleistocene transitional fauna, also described in the Pabbi Hills (Pakistan), and mark the beginning of the Equus sivalensis Biostratigraphic interval-Zone, which extends from 2.6 Ma to 600 ka. The systematic repetition of surveys has, therefore, allowed the collection of rare taxa, such as Crocuta (2010), Merycopotamus dissimilis (2014) and a large felid (2015). These latest findings are significant for the discovery of Homininae in Siwaliks.</p

Étude des polarités magnétiques des dépôts de la localité de Masol 1, chaîne frontale des Siwaliks, Nord-Ouest de l’Inde

Les formations mio-pléistocènes des Siwaliks sont mondialement connues depuis le XIXe siècle pour leurs hominoïdes fossiles. De nombreuses études paléomagnétiques ont contribué à établir le cadre chronologique du groupe Siwalik (du Miocène au Pléistocène moyen). Notre étude porte sur la formation Tatrot (Pliocène supérieur) du sous-groupe Siwalik supérieur affleurant à Masol, une localité située dans la chaîne frontale des Siwaliks proche de Chandigarh (piémonts himalayens du Nord-Ouest de l’Inde), accessible par la rivière Patiali Rao. La structure anticlinale et l’érosion ont formé une boutonnière donnant accès à des vertébrés fossiles terrestres et d’eau douce, caractéristiques de la fin du Pliocène supérieur (zone fossilifère Quranwala de la formation de Masol, Tatrot final). Depuis 2008, le programme de recherche franco-indien « Siwaliks » prospecte cette boutonnière et collecte des outils lithiques en surface des affleurements parmi des fossiles dont certains portent des traces de boucherie. Le premier fossile avec des traces de découpes a été découvert à Masol 1 en 2009. L’étude des polarités magnétiques des unités lithostratigraphiques de cette localité (M1) indique une polarité normale et intermédiaire. Compte tenu des nombreuses données biochronologiques de la zone Quranwala dans laquelle s’inscrivent les fossiles aux traces de découpe, d’une part, et des analyses magnétostratigraphiques bien connues du Patiali Rao, d’autre part, les dépôts concernés sont attribués à la magnétozone de Gauss et à la fin du Pliocène.The Mio-Pleistocene Siwalik formations have been known worldwide since the 19th century for their fossil hominoids. Numerous paleomagnetic studies have contributed to build the chronological framework of the Siwalik Group subdivided into Lower, Middle and Upper Siwalik Subgroups. Our study concerns the Tatrot Formation (Late Pliocene) of the Upper Siwalik Subgroup located at Masol in the Chandigarh Siwalik Frontal Range (India), and is accessible by the Patiali Rao River. At Masol (district Mohali, Punjab), the erosion of the anticline structure has formed an inlier and exposed paleontological assemblages characterizing the Late Pliocene “Quranwala fossiliferous zone”. Since 2008, the Indo-French research program, “Siwaliks”, has conducted surveys in the Masol inlier and has collected stone tools on the surface of the outcrops among fossilized bones, a few with cut marks. The first cut-marked bone was discovered in 2009 at Masol 1 (M1). The study of the magnetic polarities of some stratigraphic units of M1 revealed that the deposits recorded a normal polarity. According to the paleontology and the previous magnetostratigraphy of the Patiali Rao, it appeared that the deposits of Masol 1 are older than the Gauss-Matuyama reversal, dated to 2.58 Ma.</p

Les industries lithiques sur les affleurements fossilifères fin Pliocène de la formation de Masol, chaîne frontale des Siwaliks, Nord-Ouest de l’Inde (Pendjab)

La zone Quranwala du secteur de Masol (chaîne frontale des Siwaliks, Pendjab) est connue depuis les années 1960 pour ses vertébrés terrestres et d’eau douce, vivant dans la plaine d’inondation sous-himalayenne à la fin du Pliocène. Des fossiles et des galets de quartzite sont exhumés en permanence des affleurements du cœur d’un anticlinal, situés 130 m sous la limite paléomagnétique Gauss/Matuyama, datée de 2,588 Ma. Depuis 2009, le programme de recherche franco-indien « Siwaliks » a mis en évidence une douzaine de localités où des artefacts lithiques sont associés en surface aux ossements fossiles, dont certains, de bovidés, portent des traces de boucherie. Quelques galets taillés et un éclat ont été mis au jour dans un sondage ouvert dans la même limite limon/grès (Masol 2) que celle d’où provient un fût tibial portant des traces de boucherie (Masol 1). Les quelques 250 artefacts, récoltés le plus souvent en surface, parfois dans les pentes des affleurements récemment érodés, comprennent majoritairement des macro-outils et surtout des choppers, plus transversaux que latéraux, parmi lesquels des « choppers simples » (façonnés par un unique enlèvement) sont fréquents. L’outillage léger consiste en des éclats, exceptionnellement retouchés. Les nucléus sont très rares et les éclats proviennent généralement du façonnage des choppers, sauf les plus grands, complétés par les splits de galet. La cohérence des assemblages lithiques entre chacune des localités plaide en faveur d’une homogénéité chronologique. Leurs caractères n’évoquent aucune tradition technique connue dans la région, comme l’Acheuléen ou le Soanien (choppers classiques non pas « simples »).The Quranwala zone (QZ) in the sector near Masol (Siwalik Frontal Range, Punjab) has been known since the 1960s for yielding freshwater and terrestrial vertebrates living during the late Pliocene on the sub-Himalayan floodplain. The fossils and quartzite cobbles are constantly unearthed from the core of an anticline. The basal member of QZ is about 130 meters below the Gauss/Matuyama paleomagnetic reversal, i.e. , 2.588 Ma. Since 2009 the Indo-French Program of Research ‘Siwaliks’ has surveyed 50 hectares and highlighted a dozen localities on outcrops where artefacts in quartzite occur with fossil bones, of which a few show butchering marks. A few cobble tools and a flake were unearthed from a trial trench opened along the same boundary between silts and sandstones (Masol 2) as the one that provided a bovid tibia shaft bearing cut marks (Masol 1). Some 250 artefacts were collected mainly from the surface, sometimes in the slopes of outcrops recently eroded. These were mostly heavy-duty tools that comprised a majority of choppers, end choppers rather than side choppers, among which the “simple choppers” (shaped by one single removal) are common. The light-duty tools consist of flakes that are seldom retouched. The cores are very few and the flakes generally result from the shaping of choppers, except the larger flakes that are complemented by split cobbles. The consistency of the lithic assemblages among the localities supports their chronological homogeneity. Their features do not reflect any lithic technical tradition known in the region, neither Acheulean nor Soanian (in which the choppers are usually classical, not “simple”).</p

Chronology of the Late Pleistocene Caspian Sea hydrologic changes: A review of dates and proposed climate-induced driving mechanisms

International audienceThis paper provides a review of the dates used to define major hydrologic changes in the Caspian Sea during the Late Pleistocene that includes the Early Khvalynian and Hyrcanian highstands and the Atelian lowstand, and it discusses their driving mechanisms. Dates obtained by 14 C (that are the most numerous), by OSL and by U/Th for samples that are well identified in the literature through their geographic location and their laboratory number, are considered. Samples derive from sediments both in the current Caspian Sea coast and in its Middle and Northern basins. Most of dates concern the Early Khvalynian highstand while less abundant ones correspond to the Hyrcanian highstand and Atelian lowstand that preceded the Early Khvalynian. The review of these Late Pleistocene dates provides an overall revision of the hydrologic changes that the Caspian Sea experienced. Accordingly, the Early Khvalynian highstand presents two major phases. The first Early Khvalynian phase (hv1-1) took place between 36.0 and 22.0 cal kyr, and water level reached ca 0 m a.s.l. Its second phase (hv1-2) is characterised by the deposition of the so-called Chocolate Clays especially in the Northern Peri-Caspian and took place between ca 22.0 and 12.5 cal kyr BP with a water level rise until at least 40 m a.s.l. between ca 17 and 13 cal kyr BP. Before the Early Khvalynian highstand, the Caspian water level underwent a lowstand between at least 70.0 and 36.0 kyr, i.e. the Atelian lowstand, which was interrupted by the Hyrcanian highstand. During the late stage of the Atelian lowstand, between 43.5 and 42.9 and 36.0 cal kyr BP, the water level decreased between more than À60 m a.s.l. and less than-90 m a.s.l. at 42.0 cal kyr BP. The importance of the water level drop in the early stage of the Atelian regression between ca 70 and 55.2 kyr could not be estimated but according to seismic profiles, it was much less pronounced than later. The dates for the Hyrcanian highstand range from 55.2 (or even before) to 43.5 e42.9 cal kyr BP and the water level reached at least 0 m a.s.l. in its late phase. Through this synthesis, the origins of water inflows into the Caspian Sea could be suggested for the upper part of the Early Khvalynian transgression: it matches with a very large inflow of meltwater from the southern front of the Scandinavian Ice Sheet; the fluvio-glacial waters from the ice cap discharging to the Caspian Sea via the Volga River. Concerning the Hyrcanian transgression, meltwater inputs from the glaciers of western High Asia can be proposed, the fluvio-glacial waters being transported into the Caspian Sea by the Syr Darya and Amu Darya (via the Aral Sea or bypassing it)

Sedimentary archives of climate and sea-level changes during the Holocene in the Rhone prodelta (NW Mediterranean Sea)

A 7.38 m-long sediment core was collected from the eastern part of the Rhone prodelta (NW Mediterranean) at 67 m water depth. A multi-proxy study (sedimentary facies, benthic foraminifera and ostracods, clay mineralogy, and major elements from XRF) provides a multi-decadal to century-scale record of climate and sea-level changes during the Holocene. The early Holocene is marked by alternative silt and clay layers interpreted as distal tempestites deposited in a context of rising sea level. This interval contains shallow infra-littoral benthic meiofauna (e.g. Pontocythere elongata, Elphidium spp., Quinqueloculina lata) and formed between ca. 20 and 50 m water depth. The middle Holocene (ca. 8.3 to 4.5 ka cal. BP), is characterized, at the core site, by a period of sediment starvation (accumulation rate of ca. 0.01 cm yr−1) resulting from the maximum landward shift of the shoreline and the Rhone outlet(s). From a sequence stratigraphic point of view, this condensed interval, about 35 cm-thick, is a Maximum Flooding Surface that can be identified on seismic profiles as the transition between delta retrogradation and delta progradation. It is marked by very distinct changes in all proxy records. Following the stabilization of the global sea level, the late Holocene is marked by the establishment of prodeltaic conditions at the core site, as shown by the lithofacies and by the presence of benthic meiofauna typical of the modern Rhone prodelta (e.g. Valvulineria bradyana, Cassidulina carinata, Bulimina marginata). Several periods of increased fluvial discharge are also emphasized by the presence of species commonly found in brackish and shallow water environments (e.g. Leptocythere). Some of these periods correspond to the multi-decadal to centennial late Holocene humid periods recognized in Europe (i.e. the 2.8 ka event and the Little Ice Age). Two other periods of increased runoffs at ca. 1.3 and 1.1 ka cal. BP are recognized, and are likely to reflect periods of regional climate deterioration that are observed in the Rhone watershed

Iron oxyhydroxides inclusions in dolomitic banded iron formations (exemple from the Cauê Formation, Quadrilátero Ferrífero, Brazil)

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HEMATITE AND GOETHITE INCLUSIONS IN LOW-GRADE DOLOMITIC BANDED IRON FORMATIONS: PHYSICAL PARAMETER EVALUATION TO OPTIMIZE ORE BENEFICIATION

International audienceBanded iron formations (BIFs) comprise complex textures and mineralogy, which result from fluid-rock interactions related to high and low temperature alteration. The initial iron oxy hydroxide mineralogy and associated phases such as carbonates, quartz, apatite and phyllosilicates were transformed leading to an upgrading of these BIFs into the world's largest source of iron ore. In low-grade BIFs, a large part of the iron is related to micro-and nano-metric iron-bearing inclusions within micrometric quartz and/or carbonates (mainly dolomite). We studied laminated jaspilitic BIF samples from a drill core containing 26.71 wt.% total iron, 0.2 wt.% SiO 2 , 0.32 wt.% MnO, 15.46 wt.% MgO, 22.32 wt.% CaO, 0.09 wt.% P 2 O 5 , < 0.05 wt.% Al 2 O 3 , 0.15 wt.% H 2 O and 34.08 wt.% CO 2 (Àguas Claras Mine, Quadrilátero Ferrífero, Brazil). Bright rose coloured dolomite and quartz bands alternate with massive specular hematite bands. Raman spectroscopy, X-ray diffraction and FIB-TEM analyses reveal that the micro-and nano-metric inclusions in dolomite are mainly hematite and minor goethite, partly occurring as clusters in voids. Curie Balance analyses were carried out at different heating steps and temperatures on whole rock samples and a synthetic mix of decarbonated sample and pure dolomite. X-ray diffraction on the products of the heating experiments shows that that hematite is stable and new phases: magnesioferrite (MgFe 2 O 4), lime (CaO), periclase (MgO), portlandite (Ca(OH) 2) and srebrodoskite (Ca 2 Fe 2 O 5) were formed between 680°C and 920°C. These finding gives hints to optimizing the beneficiation process, as the presence of hydroxyl ions bearing goethite micro-and nanoinclusions lowers the sintering temperature. Prior separation of coarse hematite and barren dolomite and quartz, followed by lower temperature sintering of the inclusion-bearing dolomite/quartz leads to transformations into phases with higher magnetic susceptibilities (such as hematite and magnesioferrite). The entire Fe and Fe/Mg oxide feed (the priorly separated fraction added to the sintered fraction) can then pass through wet-high intensity magnetic separation after crushing

Unraveling extreme events from deep water cores of the south Caspian Sea

International audienceSouth Caspian Sea sub-basin, as the deepest part of the Caspian Sea (CS) remained as land-locked basin even during extreme sea level fall that most part of the CS desiccated. Therefore, bottom sediments of the south CS continuously recorded many past intra-basinal and extra-basinal events. In the current research we have used four short cores (<2 m) from deep waters of the south CS (300–800 m) to unravel past extreme events based on the sedimentological and geochemical analysis. Presence of coarse grained sediment laminae in the deep basin represents frequent slope failure that transported materials from lower shelf. XRF core scanning along with Magnetic Susceptibility measurements showed multiple changes along the cores. Elements incorporating in biological activities (Ca, Sr) have sharp contrast with lithogenic elements (Zr, Ti) mainly during rapid environmental changes. The deepest core has significant changes in the basal part that covers certainly Younger Dryas or even older sediments. Material influx into the deep basin of the south CS demonstrate both basinal extreme events as turbidite and mass wasting as well as catchment basin events e.g. river avulsion that caused changes in sediment properties