diatom inferred salinity in palaeolakes an indirect tracer of climate change lakes in arid and semi arid regions respond to climatic change through shifts in lake water volume and ionic concentration because diatom distribution is highly correlated with lake hydrochemistry diatoms can be used to infer changes in salinity and brine composition and thus to infer past climates here we critically examine the use of diatom inferred salinity as a climate proxy with examples taken from both modern waterbodies and sedimentary profiles sediment records may contain assemblages mixed from periods or sites of differing hydrochemistries because of the high degree of spatial and temporal heterogeneity in saline systems dissolution and diagenesis in saline brines may further complicate interpretation of sedimentary assemblages furthermore threshold effects salinity regulation via groundwater seepage antecedent conditions and other aspects of local hydrology may modify the relationship between salinity change and climatic forcing these complexities necessitate critical examination of the ecology and taphonomy of sedimentary assemblages as well as evaluation of potential non linearities in the salinity climate relationship through comparison of diatom inferred salinity with other proxy records of hydrochemical change historical documents where they exist and with other regional lake systems

holocene diatom assemblages and their palaeoenvironmental interpretations in fayoum depression western desert egypt abstract diatom assemblages from the diatomaceous deposits of fayoum depression egypt were analysed to reconstruct the palaeoenvironmental changes during the early to middle holocene a total of 283 diatom species and varieties representing 57 genera were identified the stratigraphic distribution patterns of the recorded diatoms explained eight diatom assemblage zones which revealed an interesting history of shifts in paleosalinity ph and water level of the old fayoum lake as the water body filled in planktonic and benthic epiphytic assemblages alternate throughout the studied sections the alternations reflect paleolimnologic conditions as water levels rose and fell the diatom results have shown four high stands of the freshwater lake level during humid warmer wet climatic phases coinciding with abundance of planktonic stephanodiscus spp and aulacoseira granulata assemblage zones rising lake levels are alternated with phases of lowering freshwater lake level with relatively slight rises in salinity and alkalinity one phase during arid conditions is represented by an abundance of a benthic navicula radiosa assemblage zone the second phase during cold and drier climate is dominated by a staurosira staurosirella spp assemblage zone the third phase is distinguished by predominance of epiphytic epithemia spp encyonema cymbella spp synedra spp and cocconeis placentula assemblage zones during warm arid conditions

applications of organic geochemistry to paleolimnological reconstructions a summary of examples from the laurentian great lakes the organic matter content of lake sediments contains information that helps to reconstruct past environmental conditions evaluate histories of climate change and assess impacts of humans on local ecosystems the elemental isotopic and molecular compositions of organic matter buried in sediment provide evidence of the biota that have lived in a lake and its catchment area and they serve as proxies of organic matter delivery and accumulation sedimentary records from the north american great lakes provide examples of applications of organic geochemistry to paleolimnological reconstructions the records of these lakes date from retreat of the laurentide ice sheet around 12 ka include the mid holocene hypsithermal and show consequences of recent human changes low corg ntotal ratios indicate that most of the sediment organic matter in the great lakes is from algal production yet changes in biomarker molecule compositions also show that varying amounts of land plant organic matter have been delivered to the lakes elevated algal productivity that accompanies nutrient enrichments of lake waters is recorded as excursions to less negative 13c values in the organic matter of sediments that were deposited in the 1960s and 1970s increased organic carbon mass accumulation rates mirror the isotopic excursions in most parts of the great lakes accumulations of petroleum residues and pyrogenic polycyclic aromatic hydrocarbons in sediments identify fluvial and eolian delivery of organic matter components to different parts of the great lakes emerging applications of multiple and novel organic geochemical proxies to paleolimnological reconstructions are promising yet some potentially important measurements remain underutilized

precipitation at lake qinghai ne qinghai tibet plateau and its relation to asian summer monsoons on decadal interdecadal scales during the past 500 years knowledge of the variability of precipitation at lake qinghai and its relation to the asian summer monsoons is helpful in constraining global climatic dynamics based on the high resolution precipitation indicators of 13 c of the organic matter 13 corg c n atomic ratio and the detrended total organic carbon content tocdetrended we found that the trend of precipitation at lake qinghai is inversely correlated to that of the indian summer monsoon ism inferred from layer thickness of a stalagmite s3 in southern oman on decadal interdecadal scales the chinese drought flood d f indices which can indicate the dryness wetness over large geographic areas are also used to indicate the intensity of the monsoon rainfall the d f index of xining near lake qinghai is synchronous with those of the regions in northern china where the east asian summer monsoon easm dominates while it is anti phase with those of southwestern china where ism prevails these materials suggest that during the past 500 years the source of moisture to lake qinghai on decadal interdecadal scales is controlled mainly by the easm but not by the ism it is also suggested that the intensity of easm is inversely related to that of the ism on decadal interdecadal scales the decadal interdecadal variability of enso may be responsible for the inverse relationship between the intensity of easm and that of ism 2007 elsevier b v all rights reserved

moment magnitude local magnitude calibration for earthquakes off canada s west coast local magnitude m l values of earthquakes off canada9s west coast are known to be underestimated by at least 0 5 magnitude units compared with other magnitude scales moment magnitude m w derived from moment tensor analysis provides the most robust estimate of the magnitude of earthquakes moment tensor analysis of regional seismic data in western canada is now possible due to the installation of more than 40 three component broadband stations in western canada the u s pacific northwest and southeast alaska moment tensor solutions are now possible down to m 4 0 more than 230 regional moment tensor solutions have been calculated off canada9s west coast at the geological survey of canada for 1995 2002 these solutions along with 14 previous solutions by oregon state university in 1994 1995 and 13 harvard solutions for 1984 1993 allow a systematic m w m l calibration for earthquakes in this region the study area extends from the queen charlotte islands region in the north to the area off the west coast of southern vancouver island at the northern end of the study area where there is little oceanic crust in the source receiver travel path m w is systematically larger than m l by 0 28 0 08 magnitude units at the southern end of the study area where there is a significant amount of ocean crust in the source receiver travel path m w is systematically larger than m l by 0 62 0 08 magnitude units calibration of m l with m w will allow the western canadian earthquake database to be used more effectively for tectonic studies and seismic hazard analysis

a record of late quaternary continental weathering in the sediment of the caspian sea evidence from u th sr isotopes trace element and palynological data 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

holocene climate variations from zhuyeze terminal lake records in east asian monsoon margin in arid northern china zhuyeze palaeolake is a terminal lake situated in the arid northern china in the east asian monsoon margin in order to examine the holocene palaeoclimatic change in the east asian monsoon margin qingtu lake section qtl from zhuyeze palaeolake is sampled in high resolution palaeoclimatic proxies such as grain size carbonate toc c n and delta 13 c of organic matter were analyzed eleven 14 c samples and six optically stimulated luminescence osl samples were dated to provide chronological control we also investigated the geomorphic features of lake shorelines in this area the results show that the climate was warm and dry in early holocene 9 5 7 0 cal ka bp cool and humid in mid holocene 7 0 4 8 cal ka bp and increasingly drier in late holocene since 4 8 cal ka bp comparisons of our records with other records in adjacent areas as well as with the records in the asian monsoon areas suggested that changes in effective moisture was synchronous in east asian monsoon marginal zone i e the pattern of dry early holocene humid mid holocene and aridity increasing late holocene and that the moisture optimum during the holocene was out of phase between asian monsoon margin and asian monsoonal dominated region possibly due to the high temperature at that time c 2010 university of washington published by elsevier inc all rights reserved zhuyeze palaeolake is a terminal lake situated in the arid northern china in the east asian monsoon margin in order to examine the holocene palaeoclimatic change in the east asian monsoon margin qingtu lake section qtl from zhuyeze palaeolake is sampled in high resolution palaeoclimatic proxies such as grain size carbonate toc c n and delta 13 c of organic matter were analyzed eleven 14 c samples and six optically stimulated luminescence osl samples were dated to provide chronological control we also investigated the geomorphic features of lake shorelines in this area the results show that the climate was warm and dry in early holocene 9 5 7 0 cal ka bp cool and humid in mid holocene 7 0 4 8 cal ka bp and increasingly drier in late holocene since 4 8 cal ka bp comparisons of our records with other records in adjacent areas as well as with the records in the asian monsoon areas suggested that changes in effective moisture was synchronous in east asian monsoon marginal zone i e the pattern of dry early holocene humid mid holocene and aridity increasing late holocene and that the moisture optimum during the holocene was out of phase between asian monsoon margin and asian monsoonal dominated region possibly due to the high temperature at that time c 2010 university of washington published by elsevier inc all rights reserved

late little ice age palaeoenvironmental records from the anzali and amirkola lagoons south caspian sea vegetation and sea level changes abstract two internationally important ramsar lagoons on the south coast of the caspian sea cs have been studied by palynology on short sediment cores for palaeoenvironmental and palaeoclimatic investigations the sites lie within a small area of very high precipitation in a region that is otherwise dry vegetation surveys and geomorphological investigations have been used to provide a background to a multidisciplinary interpretation of the two sequences covering the last four centuries in the small lagoon of amirkola the dense alder forested wetland has been briefly disturbed by fire followed by the expansion of rice paddies from ad1720 to 1800 on the contrary the terrestrial vegetation reflecting the diversity of the hyrcanian vegetation around the lagoon of anzali remained fairly complacent over time the dinocyst and non pollen palynomorph assemblages revealing changes that have occurred in water salinity and water levels indicate a high stand during the late little ice age lia from ad

holocene oscillations of the caspian sea and forecasts based on palaeogeographical reconstructions abstract investigation of deltas and terraces adjacent to the caspian sea has indicated the pattern of holocene fluctuations in level since the initiation of the earliest holocene transgression the surface of the caspian sea has varied between 20 and 32 m below modern sea level six transgressive episodes are recognized in the holocene record separated by regressive episodes when the level fell below 28 m a s l the modal holocene level of the caspian sea is estimated at 28 2 m a s l beginning in 1929 water levels fell rapidly in the caspian sea reaching 29 m a s l the lowest value in 400 years in 1977 however the water level began to rise a trend which has continued to the present currently the caspian sea surface stands at approximately 27 m a s l throughout the past 2500 years the level has not exceeded 25 m a s l and it is not anticipated to exceed this value in the near future the fluctuations recorded since 1929 fall within the range of variations expected from natural environmental factors which have operated since the early holocene

the african humid period and the record of marine upwelling from excess 230th in ocean drilling program hole 658c using a high resolution 230 th normalized record of sediment flux we document the deglacial and holocene history of north african aridity and coastal upwelling at ocean drilling program hole 658c at both the end of the younger dryas and after the 8 2 ka event there are significant drops in terrigenous accumulation at our site indicating an increase in the monsoon moisture flux over africa at this time at 5 5 ka there is an abrupt end to the african humid period and a return to stronger upwelling conditions for carbonate and opal fluxes the 230 th normalization completely changes the shape of each record based on percentage variations alone this site is a clear example of how variations in one sediment component can obscure changes in the others and it demonstrates the need for radionuclide measurements more generally in paleoceanography by taking our new records and a large amount of previous data from this site we conclude that increases in african moisture are tightly coupled to decreases in coastal upwelling intensity

landscape evolution and agro sylvo pastoral activities on the gorgan plain ne iran in the last 6000 years the gorgan plain ne iran is characterized by fertile soils formed on a loess plateau and is at present primarily exploited for intensive agriculture however the timing and intensity of the human impact on the landscape in the past are still unclear a sediment core taken from the centre of the eastern gorgan plain in the kongor lake covering the major part of the holocene from 6 1 to 0 8 ka all ages are calibrated before present has been studied for pollen non pollen palynomorphs botanical macroremains insects charcoal geochemistry biomarkers and magnetism in order to provide new insights into the evolution of the landscape and to estimate the intensity of human activities the data obtained suggest a dry period between 5 9 and 3 9 ka and an increase in regional humidity afterwards with a maximum between 2 7 and 0 7 ka during the period of the persian empires achaemenid through sasanian and the islamic era the eastern part of the gorgan plain was characterized by open steppe landscapes d

river inflow and salinity changes in the caspian sea during the last 5500 years abstract pollen spores and dinoflagellate cysts have been analysed on three sediment cores 1 8 1 4 m long taken from the south and middle basins of the caspian sea a chronology available for one of the cores is based on calibrated radiocarbon dates ca 5 5 0 8 cal ka bp the pollen and spores assemblages indicate fluctuations between steppe and desert in addition there are some outstanding zones with a bias introduced by strong river inflow the dinocyst assemblages change between slightly brackish abundance of pyxidinopsis psilata and spiniferites cruciformis and more brackish dominance of impagidinium caspienense conditions during the second part of the holocene important flow modifications of the uzboy river and the volga river as well as salinity changes of the caspian sea causing sea level fluctuations have been reconstructed a major change is suggested at ca 4 cal ka bp with the end of a high level phase in the south basin amongst other hypotheses this could be caused by the end of a late and abundant flow of the uzboy river now defunct carrying to the caspian sea either meltwater from higher latitudes or water from the amu daria a similar later clear phase of water inflow has also been observed from 2 1 to 1 7 cal ka bp in the south basin and probably also in the north of the middle basin

mid to late holocene paleoclimatic changes and paleoenvironmental shifts inferred from pollen and diatom assemblages at lake hamra wadi el natrun western nile delta north western desert egypt abstract four palynological and three diatom zones of mid to late holocene are identified along a 370 cm long radiocarbon dated sediment core collected in lake hamra at wadi el natrun western nile delta egypt the mid late holocene between the predynastic to old kingdom was terrestrial wetland habitat with high seasonal rainfall and or nile flood as revealed by the dominance of cyperaceae pollen therefore people gathered in and around the nile valley and the agricultural activities increased during the early stage of late holocene coincident with the old kingdom to middle kingdom the paleoclimate became more arid with low seasonal precipitation and or nile flood as reflected by the increasing abundance of poaceae pollen and the absence of diatoms in addition to low values of toc tn ts c s and high values of c n these drought conditions possibly played a role in the old kingdom collapsing the late stage of the late holocene showed terrestrial wetland habitat with brackish conditions coupled with aquatic contribution under oxic conditions as inferred by the dominance of typha sp and amaranthaceae pollens as well as the diatom assemblages the relatively high values of toc c n c s coupled with low values of ts and tn reveal terrestrial origin of organic matter the late holocene recent has turned into a terrestrial wetland habitat with more brackish conditions and increasing in the seasonal rainfall as supported by the marked increasing of cyperaceae pollen the overall increase of the diatom inferred salinity dis as well as the marked increasing of c s tn and decreasing of toc c n and ts values towards the recent point to higher saline brackish wetland paleoenvironment and a terrestrial origin of the organic matter with more aquatic contribution under oxic conditions

abrupt onset and termination of the african humid period rapid climate responses to gradual insolation forcing a detailed ca 100 yr resolution and well dated 18 ams 14 c dates to 23 cal ka bp record of latest pleistocene holocene variations in terrigenous eolian sediment deposition at odp site 658c off cap blanc mauritania documents very abrupt large scale changes in subtropical north african climate the terrigenous record exhibits a well defined period of low influx between 14 8 and 5 5 cal ka bp associated with the african humid period when the sahara was nearly completely vegetated and supported numerous perennial lakes an arid interval corresponding to the younger dryas chronozone punctuates this humid period the african humid period has been attributed to a strengthening of the african monsoon due to gradual orbital increases in summer season insolation however the onset and termination of this humid period were very abrupt occurring within decades to centuries both transitions occurred when summer season insolation crossed a nearly identical threshold value which was 4 2 greater than present these abrupt climate responses to gradual insolation forcing require strongly non linear feedback processes and current coupled climate model studies invoke vegetation and ocean temperature feedbacks as candidate mechanisms for the non linear climate sensitivity the african monsoon climate system is thus a low latitude corollary to the bi stable behavior of high latitude deep ocean thermohaline circulation which is similarly capable of rapid and large amplitude climate transitions

100 000 years of african monsoon variability recorded in sediments of the nile margin abstract multiproxy analyses were performed on core ms27pt recovered in hemipelagic sediments deposited on the nile margin in order to reconstruct nile river palaeohydrological fluctuations during the last 100 000 years the strontium and neodymium isotope composition of the terrigenous fraction and the major element distribution reveal large and abrupt changes in source oscillating between a dominant aeolian saharan contribution during arid periods and a dominant nile river contribution during pluvial periods iron content shows a strong correlation with strontium and neodymium isotopes this allows the use of a high resolution continuous fe record as a proxy of blue nile sediment input over the last 100 000 years the detailed fe record with approximately 10 years resolution during pluvial periods is consistent with subtropical african records of well dated lake level fluctuations and thus constitutes a first continuous high resolution record of the east african monsoon regime intensity over ethiopia the detailed fe record shows the two main known pluvial periods attributed to strengthening of the african monsoon over ethiopia the nabtian period from 14 to 8 ka cal bp and the saharan period from 98 to 72 ka bp for the first time the last glacial period marine isotope stage mis 2 3 and 4 is documented with a continuous record showing large oscillations between high and low east african palaeo monsoon regimes the end of the nabtian period occurred at 8 ka in core ms27pt i e much earlier than on the east equatorial african region where it ended around 5 5 ka we interpret this as evidence that the southward shift of the rain belt occurred 3000 years earlier over the eastern ethiopian highland and propose that the gradual southward migration of the rain belt was associated with highly variable intensity and longer rainy seasons from 8 to 5 ka during the last glacial period two wet periods are present around 60 50 ka bp and 38 30 ka bp these two humid periods are in phase with the rise of atmospheric ch4 concentrations suggesting that wetland tropical african area was one of the sources of the atmospheric ch4 during the mis 3 during the last glacial maximum and mis 4 high saharan aeolian influxes in phase with records of aeolian dust deposited in east antarctica are documented this study highlights the importance of reconstructions of monsoon rainfall fluctuation at high temporal resolution to better understand the link between low and high latitude climate variability at millennial timescales

sefidrud delta and quaternary evolution of the southern caspian lowland iran abstract the southern caspian sea lowland in iran forms a thick sedimentary prism produced by interactions of marine deltaic and fluvial processes during the late neogene and quaternary deltaic and fluvial deposits have been developed mainly by the sefidrud which is the largest river of the country its drainage area ca 61 600 km 2 includes nearly the entire alborz mountain range and forms deep valleys gorges and a large delta at the southern coast of the caspian sea the sefidrud delta is so large that it covers one third of the large guilan mazanderan plain both from an aerial and volumetric point of view consequently the drainage network of the sefidrud represents the quaternary evolution of northern iran and can be used to test the hypothesized evolution of the region the sefidrud delta has been investigated using many short and long cores satellite images and lithofacies maps and the results show that this delta complex 1680 km 3 consists of a covered lower part and exposed upper deltaic sequences the lower and upper parts of the complex were formed during the early pleistocene and late pleistocene respectively the upper exposed alluvial and deltaic sediments represent a total progradation of approximately 50 km forming three separate delta subsequences d1 3 of which the last one d3 is the modern sefidrud delta the modern delta is a wave dominated blanket like sediment cover ca 30 m thick and 1550 km 2 produced during the last three millennia it was formed by 30 km progradation of six juxtaposed lobes each lobe corresponds to a long term sea level fluctuation of the caspian sea the active lobe ca 50 km 2 has been forming since 1550 ad late pleistocene deltaic sequences d1 3 particularly the modern one d3 were produced by relatively fast deposition due to high volume sediment load of the sefidrud it is suggested that they were produced after the opening of the rudbar gorge by river capture that in turn six times enlarged the drainage area previous deltaic progradation and marine transgressions were relatively slow and the development of the whole lowland at the southern caspian sea lasted ca 1 1 2 ma bp

evidence for late holocene highstands in central guilan east mazanderan south caspian coast iran abstract the iranian caspian coast in the central guilan and east mazanderan were investigated using the analysis of samples retrieved from outcrops cores and through geophysical campaign the analysis of particle size organic matter calcium carbonate and fossil content as well as radiometric dating extends the caspian sea level records through the latest holocene ca 2500 years ground penetrating radar provides information about the internal stratigraphy of exposures along the central guilan coast lagoonal sediments that contained caspian mollusc shells have been dated at 2500 900 and 500 bp their dated horizons are located at altitudes of 22 24 and 25 m respectively which indicate higher sea levels during the late holocene the internal architecture and morphology of the coastal areas demonstrate spit lagoon development through littoral drift on the central guilan and east mazanderan coasts these structures also indicate lagoon formation due to rapid sea level rise a wide shallow lagoon in the central guilan sefidrud area was formed due to the last sea level rise 500 bp this lagoon then dried up as the result of falling sea level and infilled due to diversion of the sefidrud course these coastal developments show three highstands during the last 2500 years

solar forced 2600 bp and little ice age highstands of the caspian sea abstract the level of the caspian sea the largest inland sea in the world has fluctuated capriciously in history with amplitudes up to 3 m in the last century to 25 m in the last millennium and to over 150 m since the last glacial there is little consensus about the causes and forecasts are contradictory mainly due to a lack of solid data about past sea levels before 1837 ad when instrumental observation started we studied the holocene turali barrier complex along the western caspian shore in dagestan russia barrier dynamics during the last 3 m sea level cycle in the past century show that only lagoonal deposits overridden by highstand barriers are suitable for dating former highstands in the holocene barrier complex we selected the most suitable sites for dating using ground penetrating radar gpr profiles outcrops and gravel pits we obtained 14 accelerator mass spectrometry ams 14c data on in situ double valved molluscs from highstand lagoonal deposits the results suggest that the last major highstands occurred around 2600 bp and in the little ice age and coincide with global cooling events associated with minima in solar activity this suggests that millennial precipitation changes in the volga river drainage basin are also forced by solar activity

a two step expansion of the dinocyst lingulodinium machaerophorum in the caspian sea the role of changing environment 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

late pleistocene and holocene sea level change and coastal paleoenvironment evolution along the iranian caspian shore the authors published by elsevier b v this is an open access article under the cc by nc nd license http creativecommons org licenses by nc nd 4 0

a full sea level cycle in 65 years barrier dynamics along caspian shores abstract the caspian sea being a closed basin shows much higher rates of sea level change up to 340 mm yr than the oceans it experienced a full sea level cycle with an amplitude of 3 m between 1929 and 1995 its coasts therefore present an attractive physical model to test predicted changes along oceanic coasts as a result of expected eustatic sea level rise and to validate sequence stratigraphical interpretations of ancient sediments along the wave dominated coasts with intermediate shore face slopes in dagestan low onshore bars were formed during the 1929 1977 sea level fall they represent minor short lived 1 2 years transgressive oscillations within the major regressional trend after the 1977 lowstand a prominent barrier lagoon system was formed which during the first phase of sea level rise 1977 1988 encroached landwards about 18 m each year by washover during storms continuous retreat between 1988 and 1995 however barrier size diminished lagoons widened and deepened apparently due to lack of coarse grained sediment supply discontinuous retreat the 1995 highstand prevented the barriers from being overstepped altogether sea level fall after 1995 again produced low bars without lagoons the caspian sea barrier coast demonstrates that for the formation of barrier lagoon complexes the combination of transgression and storms is essential barriers may show either continuous or discontinuous development at constant rate of sea level rise and constant offshore slope depending essentially on the availability of coarse grained sediments the rate of sea level rise as a factor in barrier behaviour cannot be viewed independently from barrier dimensions which in turn depend on wave base depth and maximum storm wave height relations between para sequence thickness and frequency and amplitude of sea level change in closed basins with an independent sea level regime may differ markedly from those in basins influenced by eustasy

biostratigraphy of the marine holocene on the iranian coasts of the caspian sea abstract marine holocene deposits of the coast of iran are represented by the upper khvalinian and new caspian beds upper khvalinian sediments are faunistically barren whereas the new caspian beds contain abundant fossil molluscs that allow subdivision into the daghestan new caspian and modern layers the only fossil species found in the daghestan layer is didacna cristata the new caspian sediment layer is characterized by a taxonomically diverse molluscan assemblage dominated by cerastoderma glaucum it is subdivided into the upper and lower new caspian sub layers modern sediments are lithologically diverse besides the new caspian fauna they also contain the valves of the species mytilaster lineautus which is known to have immigrated from the black sea

paleolimnological records of climatic change in north america lacustrine fossil records provide long time series of data on limnological and climatic conditions these data are useful for establishing natural patterns of climate variability and for generating testable hypotheses about atmospheric circulation and climate ecosystem linkages shoreline features can indicate past lake level fluctuations that may reflect changes in moisture balance but often these records are discontinuous and are evidence of only extreme conditions the organisms geochemistry and sedimentology of lake sediments may provide a more continuous sequence of direct and indirect lake climate interactions in the past the most clearly interpretable paleolirnnological records of climatic change are those that use several lines of evidence to corroborate a climatic hypothesis and are from sites near an ecotone or in regions of extreme climate in all cases hydrologic setting mediates a lake s response to climate and must be considered in interpreting sedimentary sequences discussion of the impact of recent and future climatic changes necessitates a baseline against which the magnitude of observed or predicted changes can be measured commonly we look to recent history as a reference point for comparison however the landscape of recent decades or in some cases even centuries has been altered greatly by human activities thus to determine whether recent or future climatic change is unique or unusual we need long natural preanthropogenic time series against which observed or predicted climatic states and variability can be compared paleolimnological archives are a tool for looking at environmental patterns prior to anthropogenic impact and show a range of climatic states far greater than those documented by written records former strand lines of pluvial lakes bonneville and lahontan in the western u s for example testify to moisture extremes unsurpassed in recent centuries or even millennia in addition one can us the paleolimnological record as an independent climatic proxy against which patterns and rates of terrestrial response to climatic change can be compared here i present a broad overview of paleoclimatic reconstruction in north america from lacustrine records with a focus on the late quaternary the review is limited to climatic inference from paleolirnnological records a term i use in a restrictive sense to refer to records of past lake states physical biological and geochemical as opposed to records of past stream hydrology e g ely et al 1993 knox 1993 or terrestrial conditions i summarize paleolimnological tools available for reconstruction of past climate the capabilities and limitations of these tools

nile river sediment fluctuations over the past 7000 yr and their key role in sapropel development the provenance pattern of nile river sediments can be used as a proxy for paleoclimatic changes in east africa the 87sr 86sr ratios are particularly appropriate for such provenance investigations because the white nile drains predominantly crystalline basement rocks whereas the blue nile and atbara flow off the ethiopian highlands which consist of tertiary volcanic rocks a high resolution profile of 87sr 86sr and ti al ratios from a well dated core in the nile delta shows a close correspondence with known changes in nile flow over the past 7000 yr at times of higher river flow there was markedly decreased input of blue nile derived and total sediment this change was caused by northward movement of the inter tropical convergence zone resulting in increased vegetative cover in the ethiopian highlands due to higher rainfall and a longer wet season this inverse relationship between nile river flow and sediment flux may have had important implications in the development of agricultural technology in ancient egypt the marked minimum in 87sr 86sr at 4200 4500 yr b p is coincident with the end of the old kingdom in egypt and provides independent evidence that demise of the old kingdom might have been associated with an extended period of catastrophic low floods during the quaternary and late neogene there was periodic deposition of organic rich sediments sapropels in the eastern mediterranean that represent important indicators of major environmental change evidence from the ti al ratio suggests that the pattern of erosion and sediment supply from the nile catchment observed in this study also occurred throughout much of the neogene and quaternary the reduced inputs of blue nile sediment during times of sapropel formation contributed to the increased primary productivity by reducing the amount of phosphate removed on particles and to the observed change to n limitation in the eastern mediterranean which are important characteristics of sapropel deposition

late pleistocene dust dynamics and pedogenesis in southern eurasia detailed insights from the loess profile toshan ne iran abstract in southern eurasia recurrent phases of aridization dust source extension and enhanced aeolian sedimentation alternated with moister intervals promoting reduced deflation areas and dust accumulation in the context of late pleistocene climate changes weathering and soil forming intensity in this greater region are hence mainly governed by fluctuations in the balance between dust supply and moisture availability among the hitherto known sections the toshan loess soil sequence lps represents a key site due to the quality of the record and the multitude of available data giving detailed insights into the timing and magnitude of dust accumulation and soil formation of the region to elucidate these dynamics for much of the past 130 000 years bulk mineralogical and geochemical data are presented supplemented by a high resolution magnetic susceptibility record and by the results of a detailed micromorphological study of loess at toshan the last interglacial luvisol phaeozem like mis 5e and the early glacial interstadial steppic palaeosols mis 5 c and a are characterized by gradually increasing grain size and decreasing degrees in decomposition of micaceous and mafic minerals pronounced feldspar weathering is detected in the last interglacial and modern soils only which formed under reduced or absent dust deposition on penultimate and last glacial loess respectively postsedimentary the overall pedosedimentary conditions correspond to large scale trends of increasing drought dust accumulation and wind strength in southern eurasia in relation to decreasing moisture availability towards the early pleniglacial mis 4 causing soil formation under ongoing dust deposition synsedimentary similar intervals of synsedimentary soil formation are recorded during the interglacial interstadial stadial transitions of the early glacial and during pleniglacial mis 4 to 2 interstadials the latter are marked by gradual increases in magnetic susceptibility colour and decreasing texture conversely silicate weathering could not be detected suggesting that grain size fluctuations are a primary feature thus windy and arid pleniglacial conditions in southern eurasia were interrupted by intermittent phases of synsedimentary soil formation in response to short lived and relatively moist interstadials although the interrelation of these incipient soils throughout southern eurasia is afflicted with considerable restrictions the oscillatory pattern of the toshan lps bears great similarity with millennial scale oscillations recorded in limnic archives of western asia

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

oceanic pollen transport and pollen dinocyst ratios as markers of late cenozoic sea level change and sediment transport abstract palynological studies of late cenozoic cores from nine sites show large peaks in the ratio of pollen and spores to dinocysts p d which reflect major increases in terrigenous sediment influx to the north atlantic ocean under normal pelagic conditions in the north atlantic i e in the absence of ice rafting or mass wasting p d in oceanic sediments is low usually

natural and anthropogenic rapid changes in the kara bogaz gol over the last two centuries reconstructed from palynological analyses and a comparison to instrumental records abstract palynological analyses pollen and dinocysts of a sediment core taken in the kara bogaz gol have been used to reconstruct rapid and catastrophic environmental changes over the last two centuries chronology based on 210pb a natural cyclicity 65 years of water level changes in the caspian sea cs and in the kara bogaz gol kbg and anthropogenic factors building of a dam separating the cs and the kbg waters combine to induce rapid changes in water levels of the kbg in the salinity of its waters and in vegetation cover of its surroundings the impact of low water levels on the dinocysts is marked by a lower diversity and the survival of two species that are typical of the kbg the caspian sea species present in the kbg having disappeared during periods of higher water levels ad 1871 1878 the lake is surrounded by a steppe like vegetation dominated by artemisia whereas during periods of low water levels ad 1878 1913 and ad 1955 1998 the emerged shore are colonised by chenopodiaceae the period of ad 1913 1955 corresponding to decreasing water levels has an extremely low pollen concentration and a maximum of reworking of arboreal taxa during the last low level period humans responded by abandoning the shores of the bay what happened to the kbg can be used as an example of what may happen in the future for the aral sea a problem of reworking of tertiary dinocysts into modern deposits has been detected owing to the knowledge of the modern dinoflagellate assemblages recently made available through a water survey a comparison to modern surface pollen samples from central asia anzali caspian sea south and central basins aral sea lake balkhash lake issyk kul and the chinese tien shan range allows us to establish the potential reworking of at least five arboreal pollen taxa possibly by run off and dust storms

human induced changes on wetlands a study case from nw iberia abstract wetlands are exceptional ecosystems that contribute to biodiversity and play a key role in the hydrological and carbon cycles knowledge of their long term ecology is essential for a proper understanding of these valuable ecosystems we present the application of multi proxy analyses to a 115 cm thick core from la molina mire alto de la espina located in nw iberia with a chronology spanning since 500 bc the mire is located in an area intensively mined for gold during the roman period and close to a water canalization system used for mining operations at that time our aim was to get insights into the development of the wetland by combining palynological records of hydro hygrophytes non pollen palynomorphs and geochemical analyses supported by 14c datings and multivariate statistics the results indicate a complex pattern of ecological succession during the local iron age the wetland was minerotrophic since 20 ad it was subjected to dramatic hydrological changes due to a rise of the water table fluctuating between the presence of open water and phases of drawdown finally by 745 ad the wetland experienced a rapid evolution towards ombrotrophic conditions high grazing pressure was detected for the last decades the significant change occurred during early roman empire seems to have been the consequence of the direct use of the wetland as a water reservoir of the canalisation system used for gold mining thus the current nature of the mire may be the result of human impact although multiple human and climate induced causes were potentially linked to the detected shifts however the system seems to have been resilient successfully buffering the changes without substantial alterations of its functioning our investigation shows that palaeoecological research is necessary to understand modifications in the structure of wetland ecosystems their long term ecology and the role of human induced changes

formation of pyrite in freshwater sediments implications for c s ratios abstract the vertical distribution of pyrite acid volatile sulphide avs carbon and total s st were determined directly in the sediments of three lakes of different trophic status the results showed that freshwater pyrite formation reflects the redox status of the sediment or overlying waters it appears to form chiefly in reducing sediments which are subject to oxidizing influences by either a low turnover of organic carbon or periodic incursions of oxygen although there are high concentrations of avs in the near surface sediments of productive lakes very little is diagenetically converted to pyrite the feasibility of using sulphur ratios to diagnose whether rocks were formed in marine or freshwater environments is assessed new values for fes 2 fes of 0 5 5 show that this ratio does not provide a reliable test values of c sp where sp represents pyrite sulphur lie within the range of 160 700 and are much higher than previously measured ratios of c s t of 1 50 these new determinations show that if pyrite sulphur is unequivocally measured c s ratios may be a more sensitive indicator of salinity than had been previously thought

diatom inferred salinity and carbonate oxygen isotopes in holocene waterbodies of the western sahara and sahel africa abstract thirteen holocene palaeolakes in the western sahara and sahel have provided diatom records with carbonate oxygen isotope profiles available from eight of them most of these palaeolakes were groundwater fed lake water chemistry is reconstructed using diatom transfer functions lake water salinity and 18 o records are assembled with some isotopic and chemical groundwater data to better understand the response of the hydrological systems to climate changes over the past 15 000 yr data are in general agreement with climate simulations using coupled atmosphere ocean vegetation models which show a mid holocene wetting over the whole of northwest africa and a rapid drying by 6 4 ka the lake record also shows that at many sites the major lake infilling lags the end of the younger dryas by 1 2 ka regional differences also appear in the timing of the lake hydrological optimum ca 10 5 8 5 and 7 5 4 5 ka in the northern sahara 10 8 5 ka in the air tenere 10 5 7 or 4 5 in the sahel and 7 5 ka in lake chad the whole of the holocene is punctuated by short term drying events changes in water isotopic composition through time are partly explained by changes in rainfall amount and air humidity during the wet holocene period however the very low values in the southern sahara also imply changes in the moisture transport pattern or rainfall mechanisms data suggest an apparent decrease in 18 o content of precipitation along the monsoon flow in contrast with modern patterns changes in water availability and quality have driven population migrations in and out of the sahara sahel but relationships between climate and cultures are complex short term dry events might have driven inventive adaptations in the sahara drying at 5 4 5 ka coincides with both the collapse of the classical neolithic civilization and the settlement of new cultures

regional and local changes inferred from lacustrine organic matter deposited between the late glacial and mid holocene in the skaliska basin north eastern poland abstract the article presents the results of a combination of isotopic 15 n and 13 c geochemical toc tn c n and palaeobotanical investigations they were carried out on organic matter om that had been deposited from the younger dryas to the subboreal chronozone in palaolake sediments north eastern poland om from the late younger dryas consists only a small amount of toc and tn which together with the lack of aquatic macrophyte macrofossils confirm low primary production in the then reservoir the higher values of c n ratio 18 27 and 13 c ca 26 suggest that om was mainly terrestrial in origin during the preboreal chronozone 11 450 10 150 cal bp there was a probable deepening of the reservoir through the melting of dead ice this might have been intensified by an increase in precipitation and a fall in evapotranspiration during the preboreal oscillation from the early preboreal chronozone ca 11 345 cal bp a mixed source of om is indicated by c n ratio from 8 to 13 at the same time significant increase in toc and tn probably registered a rise in primary production in the palaeolake from the older part of the boreal chronozone ca 9865 cal bp algae productivity increased the c n ratio dropped to ca 8 and was then constant at the beginning of the atlantic chronozone ca 8650 cal bp a probable increase in the water level caused the partial relocation of om from the reed swamp belt and or the adjacent alder carr into deeper sections of the palaeolake an increase in toc and tn in the late atlantic chronozone ca 6965 6650 cal bp toc and tn decreased while 13 c had high values which probably reflected a more distinct stratification of the water column with anoxic bottom waters next in the late atlantic and early subboreal chronozone ca 6650 5205 cal bp the amount of om in palaeolake sediments was still rising the 13 c values dropped suggesting an intensification of processes of water mixing these processes were simultaneous with the constant shallowing of the palaeolake and the disappearance of habitats suitable for submerged macrophytes the topmost part of the profile is characteristic of a strong decomposition of peat causing a release of carbon dioxide and therefore the depletion of the carbon pool in the peat a drop in the c n ratio the concurrent upward trend of the 15 n curve is probably the effect of a greater anthropogenic impact on the palaeolake mire and its catchment and or more recent human interference in the topmost peat layers

evolutionary trend of the gorgan bay southeastern caspian sea during and post the last caspian sea level rise abstract the gorgan bay gb is a semi confined sedimentary environment at the southeastern corner of the caspian sea cs high sensitivity to eustatic sea level variations resulted in changes in the sedimentary facies and patterns of erosion sedimentation for the gb in the last caspian sea level cycle 1977 1995 therefore the evolutionary trend in coastal sedimentary environments was studied to determine the pattern of erosion and sedimentation related to sea level fluctuation cycles the sedimentology of the bay basin was studied in 500 km2 of the study area in 2001 in addition coastal changes over the two past and post periods of sea level rise were studied using satellite images landsat 7 with a resolution of 30 m and arcgis 10 1 software waves wave induced currents and sediment transport were simulated using the mike 21 software package mixed sediments particularly at the western and southern areas of the bay basin were detected through reworking of coarser barrier island sediments into deeper areas well sorted 0 35 0 5 sediments with 98 31 2 8 sand size particles were identified as the common texture along the wave dominated coasts sea progradation destruction of the beach profile and an increase in sea coverage of approximately 15 600 ha around the gb were other impacts of the cs level rise additional impacts included severe erosion and submergence of a 9000 ha area of the flat coastal plains slope 0 035 the results demonstrate that water level rise has strengthened the sediment accumulation in the bay inlet and basin at a mean rate of 0 430 mcm and 12 7 mcm respectively both field measurements and simulation results revealed the notable shoaling of the bay entrance at a mean rate of 0 2 m simulations concluded that annual longshore transport toward the bay inlet has occurred at a net rate of 80 000 m3 during the last cs level rise natural events after the eustatic cycle in the southeastern corner of the cs resulted in severe shoaling of the gb inlet and basin and restriction in the water exchange between the bay and open sea therefore comprehensive management practices to restore the gb capacity and its natural habitats are critically needed

from the allerod to the mid holocene palynological evidence from the south basin of the caspian sea 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 allerod 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 w13 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

climatic and anthropogenic impacts on the ria de vigo nw iberia over the last two centuries a high resolution dinoflagellate cyst sedimentary record abstract a high resolution dinoflagellate cyst record spanning the period of 1830 2012 ce from ria de vigo atlantic margin of nw iberia is presented changes in concentrations and percentages of dinoflagellate cysts and freshwater algal spores reflect climatic and anthropogenic influences on the ria i e coastal inlet formed by the partial submergence of a river valley statistical analyses pca and clustering were used to identify the main patterns of change in the cyst assemblages the cyst record was compared with reconstructed and measured instrumental environmental data nao temperatures mean sea level etc to support palaeo reconstructions four main phases were identified the first phase 1830 1855 ce of lower relative sea level rsl temperatures and precipitations represents the last stages of the lia little ice age the second phase 1855 1910 ce is interpreted as a transition between the colder lia and the wetter and warmer conditions that prevailed through the 20th century the third phase 1910 1975 ce is characterized by strong river inputs and water stratification in the ria and the fourth phase 1975 2012 ce reflects impacts of anthropogenic warming and pollution the anthropogenic signal consists of increases in heterotrophic cyst proportions and cysts diversity as well as of a marked decline of potentially toxic lingulodinium machaerophorum increasing organic matter content nutrients and industrial wastes have likely caused detrimental impacts on the autotrophic dinoflagellates by increasing turbidity and toxicity the b5 cyst record and its comparison with previously published data suggest that increased concentrations of l machaerophorum in the 20th century were mainly related to river flow variations that in turn were primarily driven by nao changes rather than cultural eutrophication we also report high abundances of peridinium ponticum in our record determining that this species is not exclusive to the black and marmara seas and has much wider natural distribution

climatic variations over the last 4000 cal yr bp in the western margin of the tarim basin xinjiang reconstructed from pollen data the nature of holocene climate patterns and mechanisms in central asia are open areas of inquiry in this study regional vegetation and climate dynamics over the last ca 4000 years are reconstructed using a high resolution pollen record from the kashgar oasis on the western margin of the tarim basin central asia ephedra chenopodiaceae and cannabaceae dominate the pollen assemblages and chenopodiaceae ephedra ratios and percentages of long distance transported pollen taxa are used to infer regional variations in moisture and vegetation density three periods of increased humidity are identified from ca 4000 2620 cal yr bp ca 1750 1260 cal yr bp and ca 550 390 cal yr bp and these periods coincide with the respective holocene bond events 2 1 and 0 which are reported in the north atlantic any increase in strength or southward migration of the mid latitude westerlies would result in more precipitation and meltwater on mountains surrounding the study site warm and dry conditions are detected between ca 1260 and 840 cal yr bp ad 690 1110 and cool and wet conditions are detected between ca 840 and 680 cal yr bp ad 1110 1270 during the medieval warm period ca ad 800 1200 the climate variations in the kashgar region over the last 4000 years appear to have been dominated by changes to the westerly circulation system and glacier dynamics on surrounding mountains however the question of whether the asian monsoon delivers precipitation to the western tarim basin a region that is influenced by several climate systems is still open to debate c 2012 elsevier b v all rights reserved

lithofacies and ichnofacies distribution in offshore sediments of the langarud rudsar region of iran southern caspian sea innovative computerized co axial tomography cat scan methods have been applied to two short cores collected in the southern caspian sea offshore from the langarud rudsar region of iran to the east of the sefidrud delta magnetic susceptibility ms readings in association with other lithological criteria are used to correlate the cores and calibrate to real time the cores provide a sedimentary record from this largely unstudied region covering the last 200 years 1784 to 2008 ce three principal lithofacies types were recognized the more distal locality t2 3 water depth 117 m consists entirely of poorly fossiliferous silty muds whereas the more proximal locality t2 2 water depth 51 m contains beds with rich ostracod gastropod and bivalve assemblages peak ms readings occur between 1872 and 1918 ce and are linked to erosion of sediments deposited during the little ice age lia highstands of the caspian sea cat scan results reveal the presence of the non marine mermia ichnofacies type which is reported for the first time in the caspian sea horizontal burrows feeding structures by treptichnus ichnofauna coincide with periods of lia highstand in caspian sea level and suggest low energy conditions on the marine shelf vertical burrows feeding structures occur at times of relatively stable but variable caspian water levels interbedded dark coloured organic rich muds and lighter silt rich layers within the last 100 years show potential cyclicity which may be linked to climatic and or river discharge events

climate change and the collapse of the akkadian empire evidence from the deep sea the akkadian empire ruled mesopotamia from the headwaters of the tigris euphrates rivers to the persian gulf during the late third millennium b c archeological evidence has shown that this highly developed civilization collapsed abruptly near 4170 150 calendar yr b p perhaps related to a shift to more arid conditions detailed paleoclimate records to test this assertion from mesopotamia are rare but changes in regional aridity are preserved in adjacent ocean basins we document holocene changes in regional aridity using mineralogic and geochemical analyses of a marine sediment core from the gulf of oman which is directly downwind of mesopotamian dust source areas and archeological sites our results document a very abrupt increase in eolian dust and mesopotamian aridity accelerator mass spectrometer radiocarbon dated to 4025 125 calendar yr b p which persisted for 300 yr radiogenic nd and sr isotope analyses confirm that the observed increase in mineral dust was derived from mesopotamian source areas geochemical correlation of volcanic ash shards between the archeological site and marine sediment record establishes a direct temporal link between mesopotamian aridification and social collapse implicating a sudden shift to more arid conditions as a key factor contributing to the collapse of the akkadian empire

holocene climate and cultural evolution in late prehistoric early historic west asia abstract the precipitation climatology and the underlying climate mechanisms of the eastern mediterranean west asia and the indian subcontinent are reviewed with emphasis on upper and middle tropospheric flow in the subtropics and its steering of precipitation holocene climate change of the region is summarized from proxy records the indian monsoon weakened during the holocene over its northernmost region the ganges and indus catchments and the western arabian sea southern regions the indian peninsula do not show a reduction but an increase of summer monsoon rain across the holocene the long term trend towards drier conditions in the eastern mediterranean can be linked to a regionally complex monsoon evolution abrupt climate change events such as the widespread droughts around 8200 5200 and 4200 cal yr bp are suggested to be the result of altered subtropical upper level flow over the eastern mediterranean and asia the abrupt climate change events of the holocene radically altered precipitation fundamental for cereal agriculture across the expanse of late prehistoric early historic cultures known from the archaeological record in these regions social adaptations to reduced agro production in both dry farming and irrigation agriculture regions are visible in the archaeological record during each abrupt climate change event in west asia chronological refinement in both the paleoclimate and archaeological records and transfer functions for both precipitation and agro production are needed to understand precisely the evident causal linkages

an exploratory early and middle holocene sedimentary record with palynoforms and diatoms from faiyum lake egypt abstract we report on the sedimentology pollen and diatom records in a 26 m long core of holocene sediments from the tersa area near the centre of the faiyum depression egypt two radiocarbon and one osl dates have been obtained for the core dates range from 9545 60 cal bp to c 4040 bp these correspond respectively with the terminal palaeolithic qarunian and neolithic faiyum a faiyumian cultures the core is subdivided into 3 sedimentological units unit 1 21 26 m is very thinly laminated calcareous silt deposited in a deep water lake unit 2 9 5 21 m is finely laminated sand silt and carbonates formed as a lacustrine fan delta unit 3 9 5 m to the core top is formed of massive silt sandy silt and very fine grained flood plain sands planktonic diatom taxa mainly cyclostephanos aulacoseira cyclotella and stephanodiscus spp were abundant in units 1 2 a indicating deep open lake conditions magnetic minerals increased from the base of unit 2 indicating an increasing contribution of nile alluvium benthic taxa such as fragilaria cocconeis amphora and navicula tended to increase towards the core top from unit 2 b 3 a to 3 b indicative of lake shallowing and periods of low nile floods unit 3 c is barren of diatoms and is compatible with terrestrial flood plain conditions vegetation was mainly represented by herbaceous pollen throughout most of the core and in the topmost sediment pollen was scarce but pteridophyte osmundaceae spores increased arboreal vegetation had low percentages in most of the record but increased in the middle section of the core unit 2 a depositional deltaic environment was indicated throughout most of the core sub units 2 a 3 a where high abundances of poaceae cyperaceae chenopodiaceae amaranthaceae polypodiaceae and osmundaceae were recorded indicating high nile floods and fluctuating rainfall

late quaternary araucaria forest grassland campos fire and climate dynamics studied by high resolution pollen charcoal and multivariate analysis of the cambara do sul core in southern brazil abstract late quaternary vegetation fire and climate dynamics have been studied based on high resolution dated pollen and charcoal samples and multivariate data analysis the samples were taken from a 212 cm long sediment core of a bog in the cambara do sul region on the highlands of northeastern rio grande do sul state brazil the records including seven ams radiocarbon dates span 42 840 14c years for the first time extending the reconstruction of past environmental changes on the southern brazilian highlands back to the last glacial maximum lgm and pre lgm times the last 1100 years provide a decadal resolution initially the site was a permanent shallow lake which became seasonally dry after 26 900 14c yr bp seasonal climate with a long annual dry period prevailed until the late holocene the climate was somewhat wetter from 42 840 to 41 470 14c yr bp and from 41 470 to 26 900 14c yr bp than during the lgm and the late glacial period natural fires were rare but became very frequent after 7400 cal bp suggesting human occupation of the southernmost brazilian highlands since that time the records suggest that a species rich campos grassland vegetation existed in the area under a relatively dry and cold climate during glacial times under possibly as low as 10 c the record also suggests that small populations of araucaria were probably only present in refugia of deep and protected valleys and or on wetter coastal slopes campos vegetation existed through the early and mid holocene until 4320 cal yr bp after which araucaria forest expanded into the network of gallery forests along the streams by 1100 cal yr bp the araucaria forest replaced the campos vegetation reflecting the onset of the wettest period with no marked annual dry season the marked expansion of the araucaria forest coincided with the reduction in fire between ad 1520 and 1770 weinmannia became a common taxa in the araucaria forest suggesting a shift to warmer climatic conditions on the highlands this interval was synchronous with a cool phase within the little ice age known from north atlantic land records after about ad 1780 human activities changed the original forest composition first by introducing cattle into the forest and than by selective logging of araucaria trees multivariate analysis of the pollen data shows compositional changes that follow a trajectory alternating undirectional random phases and phases with directional sometimes fast transitions the results also show that compositional changes in the vegetation are slower during cool periods lgm compared to pre lgm and faster in warm periods holocene

source of nile sediments in the floodplain at saqqara inferred from mineralogical geochemical and pollen data and their palaeoclimatic and geoarchaeological significance 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

total organic carbon isotopes a novel proxy of lake level from lake qinghai in the qinghai tibet plateau china abstract the isotopic compositions of total organic carbon toc in lakes have been widely used to interpret paleoclimatic changes and the depositional environments of lake sediments however the main factors that affect the carbon isotopes of toc source of organic material water condition and others may vary in different lake sediment records which have limited the applicability of organic carbon isotopes in explaining biogeochemical and environmental changes in lakes in this study the organic carbon isotopic compositions of aquatic plants and surface sediments from lake qinghai and the living terrestrial plants and surface soils around the lake were systematically investigated to identify the sources of toc in the sediments and the significance of the organic carbon isotopes of sedimentary toc we found that the aquatic plants in the deep water areas 10 m were primarily dominated by cladophora but submerged plants potamogeton and ruppia l are the dominant species in shallow water 13 c org values 33 6 to 28 6 that are caused by c 3 like photosynthesis but the submerged plants have enriched 13 c org values 17 8 to 15 4 that are caused by c 4 like photosynthesis in addition the 13 c org values of cladophora become more negative with increasing water depth because of the slow photosynthetic rate caused by the weak light intensity at depth the isotopic data indicate that the carbon isotopes of organic material in the surface sediments are primarily controlled by the types of aquatic plant and that the 13 c org values of toc can be used to indicate the variation of the water depth lake level the organic carbon isotopic data from the 1f core showed that the water was shallow

palaeoclimatic changes deduced from 13c 12c and c n ratios of karewa lake sediments india most long palaeoclimatic records based on isotope studies have come from deep sea cores however in order to obtain information on regional climatic variations it is essential to study continental deposits the chief limitation has been the lack of well preserved datable geological records with the exception of cave formations we report here values for the stable carbon isotope ratio 13c 12c and the elemental carbon to nitrogen c n ratio of the organic fraction of the palaeomagnetically and radiometrically dated pleistocene karewa lake sediments from kashmir india together the two ratios which are anticorrelated provide an excellent marker of the source of organic matter in the lake the karewa sediments indicate at least three major episodes of shallower than normal levels these episodes of shallow lake levels and hence a cold dry climatic regime are broadly correctable with deep sea records

20 000 years of nile river dynamics and environmental changes in the nile catchment area as inferred from nile upper continental slope sediments multi proxy analysis of two marine sediment cores ms27pt and md04 2726 from the nile continental slope provides evidence of changes in nile sediment discharge related to changes in ethiopian african monsoon eam precipitation and allows us to reconstruct changes in nile river runoff vegetation and erosion in the nile headwaters sediment element composition and neodymium isotopic composition reveal significant changes in clastic sediment provenance with sources oscillating between a saharan aeolian contribution during the last glacial maximum deglacial transition and during the late holocene and a blue atbara nile fluvial contribution during the african humid period ahp this study provides a new understanding of past environmental changes between 14 6 and 14 13 ka there was a major input of sediments from the ethiopian highlands consistent with a stronger eam at that time climate in the nile basin was wetter between 14 8 and 8 4 ka with a corresponding increase in blue nile water and sediment discharge via the main nile into the eastern mediterranean the gradual climatic transition from the ahp to the present day dry climate was reflected in a decrease in blue nile sediment deposition and flood discharge between 8 4 and 3 7 ka with aridity at a maximum between 3 7 and 2 6 ka the onset of drier conditions in the blue nile basin seems to have begun before the 8 2 ka cooling event in the north atlantic we speculate that the climatic change from the wet ahp to the dry late holocene may have been a result of a break in the low latitude dynamic equilibrium between climate vegetation and erosion which may in turn have affected the climate in higher latitudes reduced nile flow may also have had an impact on levantine intermediate water originating in the eastern mediterranean through an increase in intermediate water formation

millennial scale environmental changes in the asian monsoon margin during the holocene implicated by the lake evolution of huahai lake in the hexi corridor of northwest china the pattern of holocene environmental changes in the asian monsoon margin on a millennial timescale remains controversial based on lithological characteristics and sedimentological proxies we reconstructed holocene effective humidity changes and the lake evolution of huahai lake in the marginal area of the asian monsoon in the hexi corridor of nw china our results show that alluvial and aeolian deposition before 10 4 cal ka bp indicate an arid environment that lacustrine deposition from 10 4 to 8 8 cal ka bp indicates a transition from an arid to a humid environment and that lacustrine deposition from 8 8 to 5 5 cal ka bp occurred during the most humid conditions indicated by proxy records grain size carbonate toc and c n after 5 5 cal ka bp a depositional hiatus implicates an arid environment in the late holocene holocene environmental changes on millennial timescales in huahai lake imply that climate was arid to humid in the early holocene most humid in the mid holocene and arid in the late holocene these moisture changes were influenced by the asian monsoon particularly the transportation of water vapor by the indian monsoon in addition these moisture changes could have been affected by westerly winds that could have contributed to the water vapor supply to this region during the mid holocene the most humid conditions that occurred in the study area during the mid holocene may have been caused by strong westerlies and low levels of evaporation

rapid holocene sea level changes along the iranian caspian coast abstract the caspian sea is well known for its rapid sea level change during 1929 1995 a full sea level cycle was observed first the sea level dropped 3 m with a lowstand in 1977 followed by a 3 m rise to 1995 after which the sea level has been relatively stable these oscillations are a specific feature of the caspian sea and its sedimentary record the main purpose of this study is to reconstruct the sea level curve in the holocene by using sedimentological and biostratigraphic analysis and radiocarbon dating along the iranian part of the caspian shore remote sensing images and historical maps show that two lagoons totally emerged and the gorgan delta prograded rapidly at a rate of around 160 m y 1 until the 1975 lowstand gorgan bay was reduced in size considerably and the connection to the sea was blocked due to growth of a spit and change in base level when sea level started to rise again the coastal morphology rapidly changed and the gorgan delta retrograded at the rate of around 140 m y 1 these sedimentary dynamics can be recognized in the preserved deposits in addition to the recent dynamics core data from the southeastern lowlands show four earlier highstands using characteristic barrier lagoon deposits early holocene sea level rose until a highstand was reached of ca 34 m this phase was followed by fluvial deposition in the gorgan delta associated with a base level fall there is also an evidence of sea level rise between 5000 and 2300 bp at ca 27 7 m on top of these deposits there is evidence of a highstand between 2700 and 2300 bp at ca 23 5 m the fourth highstand from the core data is dated to the little ice age at ca 24 m data from these last two highstands correspond well with other observations from the caspian region

sediment and pollen evidence for an early to mid holocene humid period in the eastern sahara a major problem in the study of holocene palaeoenvironments of the arid and wind deflated sahara is the low preservation potential of sediments from which a record of past climatic change can be established several indirect and imprecisely dated pieces of evidence have suggested humid episodes in the holocene that may have supported more productive ecosystems and denser human populations than today searches for reliable proxy data on past climates however have failed to yield satisfactory results we report here the discovery of buried lake muds in north west sudan in the hyperarid core of the eastern sahara which yield sedimentological and palynological data clearly interpretable as recording an early to mid holocene humid episode that supported a relatively deep stratified lake surrounded by tropical savanna woodland vegetation

great sand sea and selima sand sheet eastern sahara geochronology of desertification the relation of playa sediments and associated archeological sites with longitudinal dunes allows estimation of ages for the two uppermost strata of the great sand sea active dune formation corresponds with interpluvial periods of hyperaridity dune stability corresponds with semiarid pluvial periods archeological sites associated with truncated paleosols in the selima sand sheet suggest a similar climatic relation and indicate that the isohyets of central sudan shifted at least 400 kilometers northward during the peak of pluvials

the late holocene climate change vegetation dynamics lake level changes and anthropogenic impacts in the lake urmia region nw iran two short 100 and 175 cm long sediment cores from the southwestern corner of lake urmia provide a record of vegetation dynamics lake level changes and the role of climate and humans in shaping the landscape around lake urmia over the last 2550 years relatively low values of arboreal pollen ap and substantial values of artemisia pollen from 2550 to 1500 cal bp indicate the prevalence of steppe vegetation and relatively arid climate in the area however a prominent peak of riella spores may indicate a short lived lake level rise for the period 1900 2000 cal bp the next period 1500 550 cal bp is characterized by substantial rise in ap particularly quercus and a sharp decline of artemisia chenopodiaceae amaranthaceae and wetland pollen types suggesting the expansion of oak forests under a rather moist climate and or a decline in agro sylvo pastoral practices in the area agricultural activity in the area can be inferred from sporadic occurrences of vitis ricinus and juglans pollen from the beginning of the record the rise of saline habitat pollen types between 1100 and 800 cal bp along with increased values of magnetic susceptibility and organic matter suggest a lower water level and the subaerial exposure of saline mud flats which could favour the re colonization of chenopods and other halophytes around the margins of the lake thus the medieval climatic anomaly seems to be warmer than present in the lake urmia region from 450 to 150 cal bp the decline in quercus and high values of artemisia along with higher lake levels and high magnetic susceptibility values could be associated with the little ice age since 500 cal bp quercus and riella steadily decline and fade out towards the surface of the core whereas pollen types attributable to steppe and desert vegetation increase a prominent increase in organic matter in the uppermost part of the record could be associated with a lower lake level and the expansion of wetland vegetation in the recent past our findings suggest that the regional forest coverage in the highlands of zagros and azerbaijan has reached its minimum during recent decades while urmia s lake level dropped dramatically increasing its water salinity most likely as a function of extensive anthropogenic activities and general climate aridification c 2015 elsevier ltd and inqua all rights reserved

development of spit lagoon complexes in response to little ice age rapid sea level changes in the central guilan coast south caspian sea iran 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

stable isotopes in bulk carbonates and organic matter in recent sediments of lake qinghai and their climatic implications abstract multi proxy indices on annual decadal scales during the past 600 years were developed from the surface sediments of lake qinghai based on 210pb and 137cs geochronology the 13ccarb 18ocarb and total carbonate content are consistent with one another in trends and their variations have been mainly ascribed to regional temperature it is suggested that the strong evaporation contributes in modifying 18o of lake water and 13c of the dissolved inorganic carbon of the surface water and appears to be responsible for the covariance between 13ccarb and 18ocarb photosynthesis of the aquatic plants appears to have played a significant role in determining 15n of organic matter the discrimination of 14n and 15n during photosynthesis may have triggered a positive linkage between temperatures and 15norg after removal of the stratigraphic trend variations of total organic carbon toc c n ratio and 13corg have been ascribed to local precipitation toc after removal of the stratigraphic trend is positively correlated with the c n ratio r 0 45

nile delta vegetation response to holocene climate variability a 7000 yr palynologic record from burullus lagoon nile delta egypt is assessed to investigate changes in terrestrial vegetation in response to nile flow previous studies in this region have shown that sea level rise in the early to mid holocene and markedly increased human land use during the past several centuries altered vegetation in and around the lagoon the pollen record from this study documents changes in delta vegetation that likely reflect variations in nile flow we suggest that cyperaceae pollen is a sensitive marker of precipitation over the nile headwaters and the resultant nile flow decreases in cyperaceae pollen interpreted as a marker for diminished nile flow as well as the increase in relative abundance of microscopic charcoal occurred at ca 6000 5500 ca 5000 ca 4200 and ca 3000 cal yr b p calibrated years before present these correspond to extreme regional and global aridity events associated with a more southerly mean position of the intertropical convergence zone these changes also recorded by other proxy studies indicate that several marked regional drought events affected the nile delta region and impacted ancient egyptian and middle eastern civilizations

luminescence dating of holocene playa sediments of the egyptian plateau western desert egypt abstract this study is part of a multidisciplinary project dealing with the investigation of geoarchaeological sites on the egyptian plateau with the aim of reconstructing the palaeoecological background providing age assessment which put the various results in an age frame that is of special interest here results of one particular section have been selected because of a discrepancy in age determination based on different approaches radiocarbon ages were inconsistent with the age range provided by the archaeological context in this area the underestimation observed is inferred to be caused by poor 14 c sample quality an attempt to overcome this problem was the determination of the depositional ages of the non organic sediments by using optically stimulated luminescence osl equivalent doses of four sediment samples were estimated from osl measurements carried out on sand sized quartz grains using the single aliquot regenerative dose sar protocol dose rates were calculated from neutron activation analysis results from the osl ages obtained we conclude that the sediment sequence exposing an alternation of lacustrine and eolian layers was deposited in a short period of time during the mid holocene mean of osl ages 7 8 ka compared to the 14 c ages the luminescence ages fit better into the archaeological context confirmed by surface dating