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Abstract: Dinoflagellate cyst assemblages were analysed in four short sediment cores collected in the south Basin of the Caspian Sea for assessing environmental changes over the last few millennia. Two of these cores were dated by radionuclides. The sedimentation rate of one of them was very high, in the order of 20 mm per year. The interpretation of the four sequences is supported by a collection of 27 lagoonal or marine surface sediment samples. A sharp increase in the concentration of the dinocyst occurs after 1967, especially owing to Lingulodinium machaerophorum. Considering nine other cores covering parts or the whole of Holocene, it became clear that this species started to develop in the Caspian Sea only during the last three millennia. By analysing instrumental data and collating existing reconstructions of sea level changes over the last decades, we show that the main forcing for the recent increase of L. machaerophorum percentages and concentration is global climate change, especially sea surface temperature increase. Sea level fluctuations likely only have a minor impact. We argue that the recent increase in L. machaerophorum indicates that the Caspian Sea clearly is in the Anthropocene. [Copyright &y& Elsevier]

Abstract: This study presents combined mineralogical, chemical, isotopic (87Sr/86Sr and U–Th disequilibria series) and palynological analyses on bulk sediments and on distinct mineral phases (carbonates and clays) from a 10-m-long core drilled in the southern Caspian Sea and containing a Late Pleistocene and Early Holocene record. The data allowed identifying 1) the main variations in sedimentation, 2) the processes causing these variations, 3) the modification of erosion vs weathering, and 4) the influence of climatic and/or Caspian Sea level changes in the region since the Late Pleistocene. The chemical and mineralogical results allowed the division of the sedimentary sequence into three main units and a transition zone. The lower unit (unit U1) primarily consists of silicate and carbonate-rich detritus. Sedimentation characteristics, including observation of detritus in secular equilibrium, are relatively constant within this unit and reflect mechanical erosion in a cold climate. Unit U1 probably corresponds to a glacial period when the vegetation cover was sparse and wind and river transport of pollen were strong. Subsequently, global increase in temperatures has greatly modified the sedimentation in the Caspian Sea south basin. Biogenic sedimentation is higher in units U2 and U3, and detrital inputs varied from unit U1. Variations in detrital input are likely to be caused by decreasing aeolian contribution and by relative changes in river volumes and origins. The study of the bulk sediments, clays and carbonates reflects an increase in chemical weathering since about 10 14C ka BP ago (base of unit U2), in line with an increase in the vegetation cover. Our results suggest an evolution of continental weathering conditions in the catchment area of the Caspian Sea, from dominantly mechanical/physical erosion during the cold period to a continuous increase in weathering since the Lateglacial period, as climate improved, which illustrates the strong relation between climate, vegetation cover and weathering processes. This paper also highlights how the U–Th disequilibrium series proxy, combined with other geochemical and palynological studies, could be a useful tool to record and constrain the modification of weathering regime in response to climatic and environmental changes at regional scale. [Copyright &y& Elsevier]

Abstract We present results of mineralogical (light, heavy and clay minerals), geochemical and palynological investigations of floodplain sediments at Saqqara. Our investigations provide new insights into our understanding of the source of the Holocene Nile sediments, local palaeoclimate and palaeoenvironment of the floodplain at Saqqara as well as the Holocene palaeoclimatic variations at the Nile headwaters. We also investigate the relationship between Nile floods and global climate changes and the impact of changing flood conditions on episodes of societal and central governmental collapse at the end of the Egyptian Old Kingdom. The Holocene sequences recorded in two shallow drill cores (SAQA 21 and 22) were investigated and subdivided into six sedimentary units, from underlying Late Pleistocene sand and gravels (unit I) to overlying modern soil (unit VIII). Early Holocene sediments were essentially missing in the studied cores, probably due to intensive erosion during the well-known 8.2 kyr cal BP arid event. Middle Holocene sediments are represented by unit II, which reflect high Nile floods of Equatorial African origin with less contribution from Ethiopian sources. The Old Kingdom sediments (unit III), seems to be mainly of White Nile sources with frequent contributions from the Blue Nile. Late Holocene sediments (unit IV-VII) show an increased contribution from Blue Nile River sources. Low Nile flow episodes were recorded at 5.2 (between units II and III), 4.2 (between units III and IV), 3.5 (within unit IV) and 2.7 kyr cal BP (between units V and VI). The second event corresponds to the First Intermediate Period (FIP) and the third probably coincides with the Second Intermediate Period (2nd IP), periods of disorder in Egypt. [ABSTRACT FROM AUTHOR]

Abstract: The central Guilan coast along the Iranian Caspian coastline is characterized by sandy beaches and the development of spit–lagoon complexes, which are prone to preserve past sea-level fluctuations. The morphology of three spit–lagoon complexes along the central Guilan coast was studied using ground penetrating radar (GPR) and sediment sequences to understand the effects of past sea-level changes on spit–lagoon development. The results showed the prominent role of coastal setting in conditioning the development of spit–lagoon formation in response to sea-level change. When the Caspian Sea experienced a highstand in the Little Ice Age, the coast of central Guilan recorded fluctuations in sedimentation which are reflected, for example, by river avulsion and beach ridge formation depending on physical setting. In the western half of the central Guilan, eastward longshore currents and strong wave action on a W–E coastline coupled with sea-level changes shaped the Anzali spit–lagoon complex; while in the eastern part of the studied area river avulsion and changing the coastline orientation are responsible for development of the Amirkola and Kiashahr spit–lagoon complexes under the same sea-level fluctuations. Although sea-level change has a major role in spit–lagoon development, an increase in the frequency of storms, changes in sediment supply due to more precipitation, and river avulsion are other players in spit–lagoon development in the central Guilan during the Little Ice Age and more recent times. [Copyright &y& Elsevier]