human environment interaction during the holocene along the shoreline of the ancient lake ladoga a case study based on palaeoecological and archaeological material from the karelian isthmus russia this paper presents the results of pollen diatom charcoal and sediment analyses from lake bol shoye zavetnoye situated between the gulf of finland and lake ladoga on the karelian isthmus north

micromorphology of the lower pleistocene loess in the iranian loess plateau and its paleoclimatic implications abstract the loess deposits in iran are a valuable archive of regional paleoclimatic and paleoenvironmental information extensive sedimentological and chronological studies have been carried out on the middle to upper pleistocene loess successions during the past decades but there is an absence of comparable research in the older loess deposits recently a 19 m thick loess paleosol sequence was discovered in the central iranian loess plateau ilp which was paleomagnetically dated to 2 4 1 8 ma and thus represents by far the oldest loess known in northern iran here we present the results of a detailed micromorphological investigation of these lower pleistocene loess paleosol sequences red sequence from the ilp our main findings are as follows 1 the agh band red sequence deposits are an extremely thick soil complex comprising paleosols in different stages of development 2 the micromorphological index of soil development miseca suggests that the moderately and well developed paleosols in the red sequence formed in an environment with mean annual precipitation ranging from around 450 to 650 mm respectively and 3 miseca suggests that the red sequence formed under a semi arid to sub humid climate and thus under wetter and more favorable conditions than the overlying late pleistocene loess and modern soils

late holocene sea level changes along the southern coast of finland baltic sea abstract lake isolation studies provide a reliable method for reconstructing the sea level history of areas affected by the glacio isostatic land uplift in this study late holocene relative sea level changes were investigated along the southern coast of finland gulf of finland in the baltic sea by studying 11 isolation basins in four areas kirkkonummi orslandet tenhola and prastkulla which extend across 120 km of finnish coastline that is characterised by a narrow archipelago the methods employed were lithostratigraphic interpretation diatom analyses and radiocarbon dating also used in this work are the results from three previously studied isolation basins with four 14 c dates the sea level history varies within the study area the 3000 yr old baltic sea shoreline is located about 11 m above present sea level a s l in prastkulla and about 8 m a s l in kirkkonummi these differences are due to the differences in isostatic uplift rates which have been slower in the east the main trend in relative sea level along the southern coast of finland is one characterised by a generally decreasing uplift rate during the late holocene however we identify the uplift anomalies in two areas where our data show phases of relative sea level lowering they are the first verified late holocene land uplift anomalies detected in finnish sea level data

luminescence chronology of the loess palaeosol sequence toshan northern iran a highly resolved climate archive for the last glacial interglacial cycle loess palaeosol sequences are highly resolved archives for palaeoenvironmental reconstruction and build an important link to correlate european and central asian loess sequences for the loess palaeosol sequence at toshan northern iran a luminescence based chronological framework was established the timing of dust accumulation and soil formation was investigated and thereby information on changes in palaeoenvironmental conditions in the region obtained for luminescence dating the 4e11 mm grain size fraction was used and the pirir290 approach was applied to polyminerals tests concerning bleachability dose recovery and anomalous fading were conducted the results show that residual doses have only minor influence on the determination of the equivalent dose the eemian mis 5e soil seems to be preserved but a chronological classification based on luminescence ages for this soil remains difficult the pirir290 age estimates from the lower part of the profile range from 104 9t o 127 8 ka lumi nescence ages from the central profile part point to an increase in dust accumulation starting around the mis 4 mis 3 transition furthermore a chronological framework for interstadial soils was developed indicating e g soil formation at around 40 ka during mis 3 and 26 ka during mis 2 the top part of the profile was dated to about 22 ka the age estimates show that the toshan loess profile is a highly resolved loess record providing a valuable climate archive for the last glacialeinterglacial cycle reflecting several climatic shifts represented by dust accumulation or enhanced degrees of soil formation stadials and interstadials

pedogenetic investigation of soil degradation on a deforested loess hillslope of golestan province northern iran abstract genesis mineralogy and micromorphology of soils formed on a forest and adjacent cultivated loess hillslope were investigated to assess the effects of deforestation and hillslope position on soil properties and the intensity of soil degradation the study revealed that deforestation caused a loss of soil organic carbon a reduction of cation exchange capacity and an increase in carbonates in the surface soil the soils of the different slope positions of the forest land were alfisols and mollisols with well developed argillic horizons speckled b fabric of the argillic horizons and the crystallitic b fabric of the underlying calcic horizon are evidence for a more stable landscape under forest ecosystem downward leaching caused decalcification of the upper horizons and clay movement in the profile formation of the mollic epipedon in the forest land confirms the accumulation of organic carbon and lower erosion in the surface soil soils of the adjacent cultivated area however are less developed and classified as inceptisols and mollisols absence of the mollic epipedon in the shoulder backslope and footslope positions presence of the near surface calcic horizon and absence of argillic horizon in all slope positions are due to severe erosion absence of speckled b fabric in all the slope positions of the deforested land is evidence that downward and surface movements of water have resulted in soil erosion and flooding higher smectite concentrations and occurrence of vermiculite in the forest area indicate favorable moisture availability pedology is an effective way of documenting the adverse effects of land use change especially in the hilly regions

late holocene land uplift neotectonics on the island of valamo valaam lake ladoga nw russia abstract the emergence of eight small lake basins from the lake ladoga basin waters in the island of valamo valaam nw russia was studied to work out the late holocene uplift history of the area all eight small lake basins in the island of valamo valaam emerged from lake ladoga when the water level fell 12 m in connection of the formation of river neva the current outlet of the lake the consistent valamo data is in harmony with the results from kilpolansaari north western lake ladoga and show that river neva originated 3100 14 c bp in corrected radiocarbon years at 3350 cal bp since the origin of river neva the island of valamo has been uplifted 3 3 5 m more than the neva threshold area at porogi as shown by the tilted transgression shoreline of ladoga before the neva was formed one millimetre difference in annual uplift during the past 3000 years which is the difference in the current uplift rate explains this height difference suggesting passive neotectonics in the area during the late holocene this result conflicts with russian geodetic measurements showing anomalously high uplift rates up to 6 4 mm y in the north east ladoga area where uplift values are 1 2 mm y according to fennoscandian isobase maps the above land uplift anomaly within precambrian shield terrain far from the uplift centre around the gulf of bothnia would be difficult to explain the isobase maps of present day fennoscandian uplift indicate a highly regular dome shaped uplift pattern with no anomalies at a regional scale the suggested anomalous holocene uplift discoveries in the gulf of finland and southern gulf of bothnia areas are challenged whereas strong palaeoseismicity resulting from rapid land uplift immediately following deglaciation of the scandinavian ice sheet resulted in earthquakes bedrock dislocations and massive rock falls e g in the northern lake onega area and lapland

spinel from archean impact spherules abstract large meteorite impacts are recorded in distal fall deposits preserved in two early archean greenstone belt sequences 3 2 3 5 ga mapping stratigraphie and geochemistry studies have been used to identify at least four impact layers in the barberton greenstone belt of southern africa and one in the pilbara greenstone belt of western australia spherules that represent impact melt droplets distinguish these impact layers from associated tuffs spinel with unusual compositional traits occurs within spherules in two of these impact layers spinel is the only preserved primary phase and is found within up to 10 of the spherules in the best preserved layers some spherules contain up to 40 spinel which is often the only primary phase that crystallized within the spherules spinel morphologies include dendrites and skeletal octahedra typical of those found in high temperature melts spinel compositions are similar to those of cenozoic impacts including very high ni and ferric iron contents but the archean spinel is distinctive in being composed dominantly of the chalcophile elements fe ni cr and v this spinel is not metamorphic or metasomatic in origin closely associated komatiites in the underlying onverwacht group both fresh and highly altered have unaltered spinel with igneous compositions and morphologies quite distinct from the impact spinel characteristics of spinel preserved in these archean impact spherules suggest a rather complex series of steps following a large bolide impact initial high temperature reduction produced melt droplets some of which were immiscible silicate metal sulfide density differences allowed separation of some of these immiscible melts which subsequently evolved independently and formed spherules with highly variable chalcophile element contents oxidation during atmospheric reentry increased ni fe and fe 3 fe 2 in the chalcophile siderophile melts archean impact spinel has higher ni fe than cenozoic impact spinel though distinctly lower fe 3 fe 2 which probably reflects a substantially less oxidizing atmosphere during the archean the archean atmospheric oxidation may in fact be a transient phenomenon associated with a large impact into the terrestrial ocean resulting in very high atmospheric h 2 o h 2 bolide size is estimated to be 24 km in diameter based on the average diameter of 0 85 mm for the spinel bearing spherules this estimate is consistent with the observed ir fluence in spinel bearing impact layers of approximately 5 3 mg cm2 which would be produced by a 30 km diameter chondritic bolide

loess stratigraphy in central china abstract loess sequences in central china provide a detailed record of climate changes during the last 2 5 million years at least 44 major shifts from glacial to interglacial conditions occurred during this time in china prolonged loess deposition lasting more than 40 millennia occurred eleven times with only four of these intervals in brunhes chron the climate oscillations took place with increased frequency between 2 4 and 0 5 ma compared to the last half million years major shifts toward cooler and drier climates occurred at about 2 4 ma 1 2 ma and 0 5 ma while less pronounced shifts are dated to 1 65 ma 0 8 ma and 0 2 ma three of the last four reversals of the earth s magnetic field whose lithostratigraphic position has been detail are recorded in a glacial deposit the low field magnetic susceptibility of loess and soils which reflects the concentration of ultrafine magnetite is related to the degree of pedogenesis and serves as a proxy measure of climate the accumulation rate of the magnetite was fairly constant throughout the last 1 2 million years and can serve as a measure of time susceptibility records from localities near xifeng and luochuan located 160 km apart are compared and used to define informal lithostratigraphic units in the loess plateau of china

preliminary magnetostratigraphy of a thick eolian red clay loess sequence at lingtai the chinese loess plateau magnetic remanence and bulk susceptibility measurements are reported for a 305 m eolian loess red clay sequence at lingtai the chinese loess plateau polarity zonation defined by about 680 remanence data yields a basal age of about 7 05 ma for the section which represents the oldest wind blown dust deposited continuously in north central china during the late cenozoic the resultant magnetostratigraphic scheme implies a nearly linear accumulation rate about 2 98 cm ka of atmospheric dust on the loess plateau during the period of 7 05 to 2 58 ma comparison of the bulk susceptibility record with the pedogenic characteristics of the red clay observed in the field suggests that magnetic susceptibility in the red clay is not as useful as in the loess soil sequence to indicate summer monsoon variations

micromorphological investigations of the late quaternary loess paleosol sequences of the kashmir valley india abstract the loess paleosol sequences of the karewa group preserve a valuable repository of the late quaternary climatic changes and the landscape evolution history of the karewa basin of kashmir valley in their lithological and pedogenic records three representative loess paleosol sections at shankerpora sp khan sahib ks and pattan pt localities were chosen for detailed lithostratigraphic fieldwork and micromorphological observations of thin sections lithostratigraphic analysis revealed lateral and vertical variation in thickness and number of paleosol profiles from south west to north west of the karewa basin suggesting the availability of land surface for periodic loess deposition the sp section is marked by 6 sp s6 s7 s8 s9 s10 s12 ks section by 3 ks s2 s4 s5 and pt section by 2 pt s1 s3 thick mature paleosol profiles theses paleosols have well developed ah and btk horizons representing prolonged land surface stability when pedogenic processes outpace loess deposition on the other hand comparatively thin to thick paleosol profiles represent weak to moderate pedogenic maturity indicating short stratigraphic breaks with rapid loess deposition micromorphological observations of thin sections suggested that clay illuviation and caco3 accumulation have operated within the paleosol profiles caco3 features are often associated with clay coatings suggesting decalcification of carbonates followed by clay illuviation pedogenic caco3 probably resulted from the precipitation of the soil solution near the average depth of wetting front the pedogenic caco3 illuvial clay mottles iron manganese features pedal microstructure and blocky aggregates reveal variation in the pedogenic maturity among and within the loess paleosol sections the morphological both micro and macro morphological attributes of loess paleosols suggest variation of climatic conditions during the late quaternary period in the karewa basin of kashmir valley india

late quaternary ice sheet history of northern eurasia the maximum limits of the eurasian ice sheets during four glaciations have been reconstructed 1 the late saalian 140 ka 2 the early weichselian 100 80 ka 3 the middle weichselian 60 50 ka and 4 the late weichselian 25 15 ka the reconstructed ice limits are based on satellite data and aerial photographs combined with geological field investigations in russia and siberia and with marine seismic and sediment core data the barents kara ice sheet got progressively smaller during each glaciation whereas the dimensions of the scandinavian ice sheet increased during the last ice age the barents kara ice sheet attained its maximum size as early as 90 80 000 years ago when the ice front reached far onto the continent a regrowth of the ice sheets occurred during the early middle weichselian culminating about 60 50 000 years ago during the late weichselian the barents kara ice sheet did not reach the mainland east of the kanin peninsula with the exception of the nw fringe of taimyr a numerical ice sheet model forced by global sea level and solar changes was run through the full weichselian glacial cycle the modeling results are roughly compatible with the geological record of ice growth but the model underpredicts the glaciations in the eurasian arctic during the early and middle weichselian one reason for this is that the climate in the eurasian arctic was not as dry then as during the late weichselian glacial maximum

noble metal abundances in an early archean impact deposit we report detailed analyses on the concentrations of the noble metals pd os ir pt and au in an early archean spherule bed s4 of probable impact origin from the lower fig tree group barberton greenstone belt south africa compared to other sedimentary deposits of known or suspected impact origin some noble metals are present in exceptionally high concentrations noble metal abundances are fractionated relative to abundances in chondrites with ratios of osir ptir pdir and auir at only 80 80 41 and 2 of these values in ci chondrites although an extraterrestrial source is favored for the noble metal enrichment the most plausible cause of the fractionation is by regional hydrothermal metasomatic alteration

geological and geochemical record of 3400 million year old terrestrial meteorite impacts beds of sand sized spherules in the 3400 million year old fig tree group barberton greenstone belt south africa formed by the fall of quenched liquid silicate droplets into a range of shallow to deep water depositional environments the regional extent of the layers their compositional complexity and lack of included volcanic debris suggest that they are not products of volcanic activity the layers are greatly enriched in iridium and other platinum group elements in roughly chondritic proportions geochemical modeling based on immobile element abundances suggests that the original average spherule composition can be approximated by a mixture of fractionated tholeiitic basalt komatiite and ci carbonaceous chondrite the spherules are thought to be the products of large meteorite impacts on the archean earth

recent postglacial rebound gravity change and mantle flow in fennoscandia summary the recent postglacial rebound of fennoscandia is investigated using sea level data levelling data and gravity data in particular an analysis is made of the repeated data obtained hitherto on the fennoscandian land uplift gravity line along latitude 63 methods for this analysis include an iterative procedure for computing the relation between gravity change and absolute land uplift the mass flow parameter and the geoid rise the remaining land uplift is also estimated the mass flow parameter c is used to characterize the relation between additional mass and additional volume due to rebound it is a number between 0 and 1 1 corresponding to full inflow of mantle below the rising crust and 0 to no inflow but some kind of decompression the main result is that c is significantly different from 0 at the 99 per cent level we find c 0 8 this means that models proposed of the present uplift based on pure decompression must be ruled out and that a viscous inflow of mantle is a necessary part of the ongoing uplift process on the other hand this process might be more complicated than a pure viscous flow

the pedosedimentary evolution and chronology of tortugas a late quaternary type site of the northern pampa argentina new micromorphological magnetic susceptibility geochemical and geochronological data have been collected from tortugas a key late quaternary type site of the northern pampa argentina thus enabling the detailed reconstruction of the pedogenic and sedimentary history of this loess paleosol sequence paleosols developed in the ceres formation and the overlying lower member of the tezanos pinto formation retain evidence for leaching bioturbation and particularly clay translocation processes being dominant both paleosols are truncated evidence for water sorting and sediment reworking as well as continued bioturbation and redistribution of carbonates suggests that intervening depositional phases were complex the previously recorded hypsithermal soil developed in the upper member of the tezanos pinto formation has similar characteristics to the buried paleosols yet does not appear to have been truncated at this site and is only covered by a thin layer of sediment san guillermo formation this latter unit has been pedogenically welded onto the hypsithermal soil thus creating the present day surface soil complex a series of optically stimulated luminescence dates from throughout the sequence provide a stratigraphically consistent chronological framework ca 1 150 ka for the pedosedimentary reconstruction yet conflict with the previously reported thermoluminescence based chronology for the site and region ca 1 90 ka

fan delta sequence in the archean fig tree group barberton greenstone belt south africa abstract the fig tree group of the barberton greenstone belt in south africa records the onset of tectonism and significant terrigenous and volcaniclastic sedimentation following a period of predominantly effusive volcanism in the southern part of the greenstone belt the lower fig tree conformably overlies the onverwacht group and can be grouped into either 1 volcaniclastic deposits consisting of pyroclastic and reworked volcanic detritus or 2 non volcanogenic terrigenous deposits of sandstone and conglomerate these petrologic groups are further divided into six lithofacies the lithofacies within the lower fig tree formation can be grouped into two facies associations 1 a subaqueous delta front association made up of fine grained airfall pyroclastic and slightly reworked pyroclastic debris along with resedimented land derived sandstone and conglomerate and 2 a subaerial association that is interpreted as forming from deposition of sandstone and conglomerate by flashy ephemeral stream processes on an alluvial fan surface the stratigraphic sequence coarsens upward from predominantly siltstone and fine grained sandstone at the base to pebble and cobble conglomerate at the top this sequence is interpreted as forming from the progradation of a fan delta into a body of relatively shallow quiet water composition of clasts in the conglomerates indicates that immediately underlying greenstone belt rocks or coeval volcanic rocks were the source for these coarse sedimentary accumulations erosion of uplifted greenstone belt terrain was apparently only to shallow levels both tectonic and volcanic activity played a role in producing several cycles of fan delta progradation

genesis morphology and mineralogy of planosols developed from different parent materials in southern brazil abstract the genesis of planosols is a complex process since it can involve multiple cycles of soil formation deposition of allochthonous materials and also past climate changes furthermore this subject is still poorly studied in the humid tropics thus hindering a proper appraisal of the potentials and limitations of planosols the objective of this research was to study pedogenetic processes and properties of planosols formed from different parent materials in southern brazil four soils were sampled p1 hypereutric luvic albic planosol developed on lagoon plain sediments p2 orthoeutric luvic albic planosol on holocene alluvial deposits p3 hypereutric luvic albic planosol on granite and p4 orthoeutric luvic albic planosol on gneiss all planosols presented sandy horizons a and e with low ph

the depositional environment of the late pliocene red clay jing le basin shanxi province china abstract red silty clays of late pliocene age are widely distributed in northern china at the type section in the jing le basin in shanxi province they overlie alluvial and lacustrine sands and gravels and underlie loess new data on grain size grain shape fabric chemistry floral pollen content and previously catalogued faunal evidence suggest sedimentation of the silty clays in a warm temperate and sub humid environment as a weathered mantle transported down gentle slopes by creep and rainwash the jing le formation represents a transition from dominantly alluvial deposition in the upper pliocene to dominantly aeolian deposition in the lower pleistocene

pedosedimentary development and palaeoenvironmental significance of the s1 palaeosol on the northeastern margin of the qinghai xizang tibetan plateau the s1 pedocomplex correlated to oxygen isotope stage 5 of the ocean cores has been traced west of the loess plateau on to the extreme northeastern margin of the qinghai xizang tibetan plateau in china detailed micromorphological analysis of closely spaced thinsections from the pedocomplex at this site provides the basis for reconstruction of the sequence of pedosedimentary processes and associated palaeoenvironmental changes occurring during this time interval the six pedosedimentary stages identified are interpreted in terms of temporal variations in depositional rates size of particles transported and availability of moisture for pedogenic alteration as determined by changing balances in dominance of winter and summer monsoonal forces two main soil forming intervals are identified the more extensive of the two in terms of resultant pedological features reflects pedogenic alteration at a relatively stable land surface under a semi arid climate during the later part of pedosedimentary stage 2 the other main period corresponds to pedosedimentary stages 4 and 5 when leaching and bioturbation processes were active at aggrading surfaces leading to development of an accretionary unit without clear differentiation of horizons pedosedimentary stages 1 3 and 6 were characterised mainly by rapid rates of coarse loess accumulation with synsedimentary modification restricted to surface slaking and crust formation and minor localised redistribution of calcite

use of micromorphology for palaeoenvironmental interpretation of complex alluvial palaeosols an example from the mill creek formation albian southwestern alberta canada abstract field observations are often not sufficient for process based interpretations of palaeosols particularly where they form parts of thick aggradational pedocomplexes within alluvial successions under such conditions micromorphology provides genetic temporal and spatial information on soil forming processes that is critical to an understanding of past environmental conditions thick alluvial successions of the albian mill creek formation contain abundant evidence of pedogenesis but few well developed palaeosol profiles and therefore provide an ideal case study in which to demonstrate the usefulness of micromorphological data for palaeoenvironmental interpretation the micromorphological features of greatest interpretive value are types of clay coatings and ferruginous segregations structure and fabric papules evidence of bioactivity and ferruginous concretions provide information on geomorphic surface stability and assist in reconstructing temporal changes in drainage conditions while individual features can provide some palaeoenvironmental information the relationships of features to one another and assemblages of features provides additional information when analysed hierarchically to establish a sequence of sedimentologic and pedogenic events a common recurring sequence of palaeoenvironmental events subject to local variations can be recognized throughout the mill creek formation the presence of illuvial clay requires that water percolated through the soil and that the soil periodically dried out so that the translocated clay was retained dark reddish clay coatings indicate clay illuviation under freely drained conditions while pale yellow and silty clay coatings suggest that phases of free drainage alternated with phases of poorly drained or saturated soil conditions the presence of iron depletion coatings iron nodules and quasiferrans indicates that these units were at least periodically saturated and the occurrence of multiple overlapping phases within single thin sections demonstrates that redox conditions fluctuated strongly suggesting development in the vadose zone recent soils containing similar assemblages of features develop under warm temperate seasonal climates alternating phases of well drained and saturated conditions on the mill creek floodplains are attributed to changing sediment supply and local palaeogeomorphology rather than to any major regional climate change this type of process based micromorphological analysis should have broad application in other complex pedogenically modified alluvial successions and similar studies would lead to a more detailed understanding of ancient palaeoenvironments

late cenozoic base level variations of the caspian sea a review of its history and proposed driving mechanisms abstract the caspian sea is characterized by significant variations in its base level during the late cenozoic and provides an important repository for long term records of both regional climate and tectonics due to its position within the interior of the eurasian continent and at the northern margin of the ongoing arabia eurasia collision zone the caspian also serves as an important moisture source for eastern eurasia including the northern tibetan plateau and thus the history of caspian base level variations represents an important and poorly understood constraint on paleoclimate reconstructions throughout eurasia prior work in the caspian region has largely focused on developing biostratigraphic age divisions and investigating the history of connection between the caspian black and mediterranean seas as well as the global ocean recent geochronologic work in the caspian and related basins has questioned previous correlations of hydrologic events in these different basins as a result prior estimates of the chronology and magnitude of caspian sea level variations may be incorrect here we synthesize previous work to develop a new caspian base level curve starting at the beginning of the meotian regional stage 7 ma we also present a new synthesis of potential driving mechanisms for the large variations in caspian base level and speculate on a possible cause for the enigmatic akchagyl transgression this synthesis highlights the dynamic range of caspian sea level which varied from 200 m above to in excess of 1000 m below its current level during the late cenozoic and provides a basis for future work investigating the tectonic and climatic drivers behind variations in caspian base level

shoreline displacement in the belomorsk area nw russia during the younger dryas stadial abstract a total of six small basins were cored to determine the shoreline displacement of the belomorsk area nw russia during the last deglaciation conventional shoreline displacement methods were applied where the isolation contacts of the sediment cores from lakes at different altitudes were determined using lithological and diatom taxa changes the isolation contacts were subsequently dated using the 14c ams method the results show that the area around the cored basins formed part of an extensive ice lake that existed in the white sea basin prior to 12 000 cal yr bp dating together with lithostratigraphical and diatom results indicate that the isolation of the lakes between 72 and 134 m above the present sea level occurred at 12 000 cal yr bp and the relative water level in the white sea basin dropped at least 62 m within a maximum of 300 years it is estimated that at least 50 55 m of the relative water level fall was caused by a sudden drainage of the ice lake waters into the barents sea via the gorlo strait and 7 12 m of the water level decline was caused by glacioisostatic uplift preliminary calculations suggest that the total volume of water that burst into the barents sea was c 3000 km3 this together with that of c 7000 km3 of water which drained into the north atlantic as the result of the baltic ice lake drop around 11 600 cal yr bp must have affected the behaviour of the eastern flank of the scandinavian ice sheet and had a cooling effect on local climate

diatom and stable isotope records of late holocene lake ontogeny at indrepollen lofoten nw norway a response to glacio isostasy and neoglacial cooling borg indrepollen is a coastal lake on the island of vestvagoy lofoten nw norway a sedimentary sequence spanning the last 4500 cal yr bp was analysed for diatom c n and stable isotopes 13c and 15 n the record provides clear evidence of glacio isostatic rebound in the lofoten region five distinct lithostratigraphic geochemical zones i v and four major diatom zones a d were identified the early record i iii a biii 4500 550 cal yr bp contains coarse sedimentary material and diatoms indicative of more marine conditions the correlation between the isotopic data high 13c and low c n and trends in the biological data marine brackish flora suggest the marine influence on the indrepollen basin is a controlling factor of the source of organic material the latter part of the record iv c 550 cal yr 550 226 indicates a transitional phase from marine dominated diatom to brackish taxa and is coincident with a section of microlaminations in the core the youngest zone v d 226 cal yr bp

holocene sea level changes and glacio isostasy in the gulf of finland baltic sea abstract shoreline displacement in the eastern part of the gulf of finland during the past 9000 radiocarbon years was reconstructed by studying a total of 10 isolated lake and mire basins located in virolahti in southeastern finland and on the karelian isthmus and in ingermanland in russia study methods were diatom analyses sediment lithostratigraphical interpretation and radiocarbon dating in southeastern finland the marine litorina transgression maximum occurred ca 6500 6200 14 c yr bp 7400 7100 cal yr bp in areas of the slower land uplift rate on the karelian isthmus and in ingermanland the transgression maximum occurred ca 6400 6000 14 c yr bp 7300 6800 cal yr bp the highest litorina shoreline is located at ca 23 m above present sea level in southeastern finland whereas in the eastern part of the karelian isthmus near st petersburg it is located at ca 8 m above present sea level the amplitude of the litorina transgression in virolahti area is ca 4 m whereas on the karelian isthmus and in ingermanland the amplitude has varied between 5 and 7 m the regional differences between areas are solely due to different glacio isostatic land uplift rates the seven basins studied in this research were connected to the baltic sea basin during the litorina sea stage and their diatom and lithostratigraphical records indicate a single smooth litorina transgression

micromorphology and development of loess derived surface and buried soils along a precipitation gradient in northern iran abstract the northern footslopes of the alborz mountains and an extensive hill area in eastern golestan province are covered by thick 70 m loess deposits divided by different types of interstadial and interglacials paleosols the area shows a precipitation gradient of about 800 mm over 80 km north south along this gradient eight pedons of modern soils and six paleosols were selected in order to investigate the types of modern and past soil forming processes and to compare the degree of soil development of surface and buried soils the soils were described and sampled using standard sedimentological pedological laboratory analysis the soil ph and calcium carbonate contents show a decreasing trend with precipitation while soil organic carbon clay content and cation exchange capacity increase with rainfall the silt content however shows a decreasing trend with rainfall clay mineralogy of parental loess is illite chlorite smectite kaolinite from north to south the relative proportion of smectite in soil horizons increases reaching almost dominance in regions with typic xeric soil moisture regime smr 600 mm of rainfall in the areas with udic smr vermiculite increases and sometimes dominates micromorphology provides evidence for the formation of bt horizons and intensified decalcification and increase of clay mobilisation as indicated by b fabrics with increasing rainfall soils within the xeric and udic smrs are either alfisols or mollisols both showing clay illuviation features whereas clay mobilisation is very limited in the arid part of the area the paleosols show differential weathering degrees indicated by trends of increasing carbonate depletion clay mobilisation and clay enrichment with assumed paleo precipitation pedogenesis micromorphological properties and clay minerals in the last interglacial paleosols suggest similar climate controlled trends to those reflected in the modern soils

isotopic and micromorphological studies of late quaternary loess paleosol sequences of the karewa group inferences for palaeoclimate of kashmir valley abstract pedogenic carbonates widespread in paleosols throughout the geological ages have been widely used to infer climatic conditions and vegetation type during their formation they are ubiquitous and widespread in the late quaternary loess paleosol sequence of the kashmir valley mostly in the form of carbonate nodules in the present study pedogenic carbonates are studied to analyze trends in the stable isotopic composition of carbonate nodules across three well developed loess paleosol sections in the kashmir valley the stable carbon isotopic 13 c analysis reveals a gradual increase of the c 4 vegetation towards the top of the sections the development of c 4 plant biomass towards the top of sections possibly reflects water stress and or reduced atmospheric pco 2 and increasing aridity the oxygen 18 o isotopic analysis reveals little variation with the values ranging from 6 37 to 7 75 reflecting stable climatic conditions during the development of pedogenic carbonate nodules the use of geospatial data including digital elevation model dem and landsat tm remote sensing imagery have added morphological characterization of the topographic and landform features observed in the area the tectonic uplift of the pir panjal range variation in the geometry of karewa basin and the slope gradient have played a key role in the spatial variation of loess paleosol sequences in the valley the late quaternary climate changes deposition of loessic sediments formation of the interbedded paleosol profiles and the subsequent denudation processes have resulted in the present day typical geomorphic landscape of the kashmir valley the micromorphological analysis of loess paleosol horizons reveals cold arid to semi arid climatic conditions prevailed during the late quaternary in the valley

argillic horizon development in calcareous soils of arid and semiarid regions of southern iran abstract ten representative pedons with argillic horizons from southern iran were selected for micromorphological and mineralogical study they were classified as haploxeralfs haplustalfs argixerolls argiustolls and argigypsids with thermic hyperthermic and mesic temperature regimes some of the argillic horizons were probably formed in a less arid previous climate during which carbonate migrated through the profile thus allowing clay to illuviate into deeper horizons thin sections showed few to no clear clay coatings in argillic horizons with greater clay content where shrink swell has disrupted them clay coatings superimposed on carbonate coatings and in turn covered by calcite indicate recalcification calcite depletion pedofeatures were the most striking features in these soils sodium may have played an important role in the dispersion of clay and formation of argillic horizons within two of the pedons studied a micromorphological index of soil evolution in highly calcareous arid and semiarid conditions is proposed it correlates with the content of free fe2o3 fedcb in fine earth the colour index the clay illuviation index and the smectite chlorite illite ratio the index can be useful for correlation of soils with argillic horizons formed on highly calcareous parent material in different landscape units new subgroups of haploxeralfs and argiustolls are suggested for inclusion in soil taxonomy based on the properties of some of the studied profiles

early archean spherule beds chromium isotopes confirm origin through multiple impacts of projectiles of carbonaceous chondrite type comment and reply reply this is a exchange in the form of a comment and a reply in regards to an earlier article the authors of the original article consider it likely that virtually all of the projectile will condense with the silicate fraction resulting in very little platinum group element fractionation in the final ejecta deposit further we find no evidence in the commentator s i e glikson comment to support vapor fractionation we note that the pd ir ratios of published data on 2 56 ga hamersley basin spherules are all greater than in chondrites contrary to the assertion by glikson this is consistent with relatively high pd concentrations and pd ir ratios in crustal rocks

a review of the history of the baltic sea 13 0 8 0 ka bp abstract the dynamic history of the baltic sea during the millennia following the last deglaciation has been one of the main topics for many generations of quaternary geologists around the baltic sea based on the present state of knowledge and certain hypotheses a model for the development during the baltic ice lake yoldia sea and ancylus lake stages are presented the oresund strait was the threshold of the initial stage of the baltic ice lake and was eroded down to bedrock as a result of the isostatic uplift the emerging threshold forced the baltic ice lake to rise above sea level at ca 12 0 ka bp this gradual up damming ended at ca 11 2 ka bp when the large glacial lake was lowered 5 10m by possible subglacial drainage at mt billingen a glacial readvance during the younger dryas ended a ca 400 year long land bridge between sweden and the continent by blocking the former drainage route once again the baltic ice lake had to rise above sea level to be drained over the oresund strait at ca 10 5 ka bp a gradual ice recession began and 200 years later when the receding ice sheet could not withhold the up dammed water masses the final drainage of the baltic ice lake occurred which rapidly lowered the water level within the baltic basin with ca 25 m and ended the baltic ice lake stage the next stage the yoldia sea was characterized by a complex pattern of relative sea level changes with large differences within the baltic basin a very restricted baltic sea in the south and thus an extensive landbridge at ca 9 9 ka bp a short 100 200 years saline ingression is seen in the baltic sediment records from stockholm in the north to the southernmost parts of the yoldia sea the gradually shallower strait in south central sweden the narke strait ended the saline influence 300 400 years later the two remaining outlets west of lake vanern gota alv and otteid steinselva had become too shallow to swallow the outflowing yoldia sea waters at this stage the baltic lake vanern level could thus not fall in pace with the relative sea level fall outside the outlet areas this was the isolation of lake vanern and the baltic from the sea and the beginning of the ancylus lake since the water depth of the larger gota alv outlet had to be more or less maintained the ancylus lake level had to rise in pace with the uplift of the outlet region this caused a significant and rapid transgression 10 30 m in ca 300 years in the southern baltic which flooded large areas with recently immigrated pine forests since the oresund strait during the yoldia sea stage had been uplifted more than southerly areas the ancylus transgression ended with a new drainage pathway at ca 9 2 ka bp through the darss sill area in the southern baltic and northwards through the store belt strait this so called dana river had cut off the former large land bridge the quaternary deposits of this new threshold were eroded and a fairly rapid regression set in at ca 9 0 ka bp the dana river had eroded down to the sea level which isolated lake vanern from the ancylus lake and created a land bridge between southern sweden and northwards ca 800 years later when the sea level rose above the oresund threshold marine water could enter the baltic and at ca 8 0 ka bp brackish water characterized the southern baltic this marks the end of the ancylus lake

genesis and micromorphology of loess derived soils from central kansas abstract the genesis and micromorphology of three harney soils from different precipitation regions from 540 mm to 715 mm fine smectitic mesic typic argiustolls in the smoky hills of central kansas were investigated the objectives were to 1 examine the morphological chemical physical and mineralogical characteristics of harney soils formed in loess 2 determine the clay mineral distribution with depth and the origin of the clay minerals present and 3 investigate the relationship between the clay mineralogy and other soil properties such as soil plasmic fabric cole values and fine clay total clay ratios mineralogical and micromorphological techniques were used to evaluate the characteristics of the loess derived soils the first pedon was formed in 88 cm of bignell loess over peoria loess and the other two pedons were formed from peoria loess the chemical properties were similar for the pedons studied differences were observed in physical properties especially in particle size distribution oven dry bulk density and coefficient of linear extensibility values although the soils were mapped in the same soil series the geomorphic positions of the pedons and the nature of the parent material affected the characteristics of the soils smectite was the predominant clay mineral especially in the fine clay fraction regardless of the location in the precipitation gradient the dominance of smectite increased in the c horizons this implies a detrital source of smectite in the b horizons formed in both bignell and peoria loess units the presence of randomly interstratified mica smectite and the micromorphological observations of weathering biotite indicate that weathering also plays an important role in the mineralogy of harney soils the high content of clay mica in the surface horizons was caused by dust fall in the study area thick and continuous argillans were observed when fc tc and cole values were low and crystalline smectite was present in the lower part of the soil profiles the plasmic fabric was mostly ma skelsepic granostriated b fabric and smectite was more crystalline as indicated by sharper x ray diffraction peaks

loess soil sequence at toshan northern iran insights into late pleistocene climate change abstract the knowledge of palaeoclimate in iran is still limited however insight into the timing and the dynamics of quaternary climate change in iran might offer valuable information to improve the global palaeoclimate record the loess soil sequence of toshan provides the first high resolution record of late pleistocene climate dynamics in iran and complements the hitherto known sections at neka now deh and agh band to establish a pedostratigraphic record of the north eastern caspian lowland our spectroscopic and grain size analysis are combined to propose i a pedostratigraphical scheme for the sequence at toshan ii describe and estimate the degree of soil development of selected stratigraphical units iii infer palaeoclimatic information and provide iv a correlation with previous loess palaeosol records of n iran as based on pedostratigraphic assumptions the section at toshan hosts a strongly developed reddish brown argillic palaeosol bt as well as eight moderately to weakly developed brownish palaeosol horizons lacking clay illuviation features bw bwk these remnants of fossil soils are separated by finely textured loess and horizons that host characteristics of both loess and mineral subsoils cb cbk giving evidence for syngenetic soil formation the stratigraphical succession of palaeosols loess and syngenetically altered sediments covering the last ca 130 ka gives evidence for recurrent climate changes as well as fluctuations between dominance of soil formation or dust accumulation in relation to changes in moisture regime the formation of bt and bw bwk horizons is related to relatively humid and warm conditions likely corresponding with interglacial and interstadial climate

loess chronology of the caspian lowland in northern iran the loess palaeosol sequences of the caspian lowland in northern iran provide detailed archives of climate and environmental change showing a close relationship to global cooling and warming trends for the quaternary period the magnitude of these changes is under discussion owing to uncertainties in the chronologies for individual sites a chronological frame was set up for the last glacial loess record for three upper pleistocene key sections by infrared optically stimulated luminescence irsl in the caspian lowland irsl dating gives reliable ages for sediments covering at least the past 60 ka however for sediments older than 60 ka a significant age underestimation is likely the first strongly developed buried bt bwt horizons or pedocomplexes at the three sections under study correlate most likely with the last interglacial mis 5 at least four periods of increased sediment accumulation were determined for the last glacial period intercalated by periods of weak soil formation the loess palaeosol sequences in northern iran recorded coeval and similar major climatic changes as in south eastern central europe and central asia

soil formation in loess derived soils along a subhumid to humid climate gradient northeastern iran abstract in order to contribute to the understanding of carbonate enrichment and clay illuviation in loess derived soils of subhumid to humid regions the development of soils was studied along a climate gradient with xeric and udic soil moisture regimes smr and thermic and mesic soil temperature regimes str respectively in the golestan province northeastern iran six representative pedons along a climate gradient were investigated soils were classified mainly as hapludalfs and haploxeralfs stability of the geomorphic surface under forest vegetation associated with high leaching conditions has provided appropriate conditions for decalcification followed by clay migration through the profile and formation of argillic horizons in all the studied soils clay content of the bt horizons soil organic carbon concentration of the a horizons and depth of the bk horizons increased significantly with increasing precipitation and decreasing temperature there was a considerable decrease in silt content with soil development the main pedofeatures observed in the bt horizons were clay coatings and decalcified zones nodules coatings and hypocoatings were the main calcitic pedofeatures observed in the bk horizons occurrence and preservation of clay coatings were more pronounced in the udic regions with illite and vermiculite as the dominant clay minerals type of clay minerals shrink swell properties and precipitation rate are factors affecting the abundance and preservation of clay coatings in the strongly developed horizons of the udic smr the occurrence of vermiculite clay minerals could reduce the shrink swell potential and increase the amount of clay coatings the presence of crystallitic b fabrics and the high carbonate contents caco 3 in the lower horizons bk were mainly related to decalcification processes under descending water flow in the overlying horizons

mineral composition vs soil forming processes in loess soils a case study from krakow southern poland abstract the mineral composition of soil parent material has a clear impact on soil formation soil properties especially chemical properties and mineral transformation in soil environment despite many studies concerning loess soils detailed quantitative studies on the mineral composition and transformation of clay minerals in loess soils formed during holocene and the influence of the mineral composition of parent material on the properties of loess soils are rare the main aims of the present study were 1 to determine the influence of loess mineral composition on soil genesis and 2 to determine layer silicate transformations and clay mineral formation in loess soils in relation to soil forming processes using qualitative and quantitative x ray diffraction analyses xrd and qxrd the obtained results show that the occurrence of carbonate minerals i e calcite and their influence on chemical properties of soil play a crucial role in the evolution of loess soils in loess that does not contain carbonates dispersion and translocation of clay particles including clay minerals down the profile occur this leads to the formation of luvisols and albeluvisols in carbonate loess clay minerals and soil organic matter form stable humus mineral complexes leading to the accumulation of humus and the formation of chernozems the transformation of mica and or smectite and or vermiculite to hydroxy interlayered minerals hims is the dominant process in the studied loess soils developed in a temperate climate because intense weathering of layer silicates is possible after removal of carbonates from soil profile this indicates that the occurrence of carbonates which maintain soil ph on a level of about 7 or higher is most likely the main factor controlling the rate of weathering of layer silicates in a loess soil environment in carbonate loess the dissolution and leaching of carbonates prevail over the weathering of silicates it is highly likely that the continuous leaching of carbonates assuming that the climate will not change will lead to more intense weathering of layer silicates

stable isotope composition of subfossil cerastoderma glaucum shells from the szczecin bay brackish deposits and its palaeogeographical implications south baltic coast poland abstract the environmental conditions of the szczecin bay which existed prior to szczecin lagoon have been reconstructed on the basis of the stable carbon and oxygen isotope 18 o and 13 c analysis and radiocarbon dates obtained for subfossil shells of cerastoderma cardium glaucum the shells in the collected core were well preserved in their life positions representing a geochemical record of past temperature variation over the middle holocene three major periods with different thermal conditions have been distinguished in the interval 6000 4300 cal yr bp when the important littorina regional transgression took place during the first period 6000 5250 cal yr bp water temperature decreased by 1 4 c and then remained constant over the second period 5250 4750 cal yr bp in contrast during the third period 4750 4300 cal yr bp both values were highly variable and the mean summer temperature march november increased by about 3 5 c during first two periods 18 o and 13 c were significantly correlated indicating stability of the environmental conditions

forced regressive deposits of a deglaciation sequence example from the late quaternary succession in the lake saint jean basin quebec canada differentiating between forced regressive deposits from deglacial periods in high latitude domains and forced regressive deposits from the onset of glacial periods in low latitude domains is fundamental for the accurate interpretation of glacial cycles within the geological record and then for the reconstruction of palaeogeography and palaeo climate a forced regressive deglacial sequence is documented from the lake saint jean basin quebec canada in this area the late pleistocene to holocene sediments have recorded the laurentide ice sheet retreat accompanied by the invasion of marine waters laflamme gulf from ca 129 cal kyr bp subsequently fluviodeltaic and coastal prograding wedges were deposited they followed the base level fall due to glacio isostatic rebound this succession representing a transition from glacial to post glacial periods within a previously glaciated area was investigated through recent mapping preserved landforms facies analysis and new optical stimulated luminescence and radiocarbon dates three basin scale geological sections share a common lower part made of isolated ice contact fan deposits overlying bedrock throughout the entire basin ice contact fans are capped by glacimarine muds above fluvial and coastal prograding systems were deposited and evolved through four steps i deltaic systems progressively increased in width ii coastal influence on sedimentation increased iii hydrographic drainage systems became more organised and iv deltas graded from steep gilbert delta to low angle foresets mouth bar delta deposited during the base level fall from glacioisostatic rebound the complete succession has been designated as a single falling stage system tract referred to as a deglacial falling stage system tract it is representative of a deglaciation sequence in areas previously covered by ice during glacial periods i e medium to high latitude domains diagnostic criteria are provided to identify such a deglacial falling stage system tract in the geological record which may aid identification of previously unknown glacial cycles

a multi proxy palaeolimnological study to reconstruct the evolution of a coastal brackish lake lough furnace ireland during the late holocene abstract this study examines the evolution of lough furnace a coastal brackish lake in the west of ireland using high resolution sensors in the water column and palaeolimnological examination of the sediment archive palaeoenvironmental reconstructions suggest that meromixis formed as a result of sea level rise prior to ca 4000 cal yr bp increased seawater inflow has progressively led to permanent water stratification which caused the onset of anoxia making the monimolimnion a harsh environment for biological life diatom floristic interpretations suggest a progressive upcore increase in salinity which is paralleled by a reduction in cladocera remains diagenetic processes have not altered the sediment organic matter signature organic matter mainly derives from freshwater doc and appears to be linked to the presence of peat bogs in the catchment as confirmed by the c n ratio upcore variations in the c n ratio with a ca 800 year periodicity have been interpreted as the result of alternating dry and wet climatic phases during the late holocene which appear synchronous with the nao and long term solar cycles the current hydrology is largely controlled by freshwater inflow which determines permanent meromictic conditions overturns are rare requiring a specific combination of factors such as exceptionally dry and warm summers followed by cool autumns according to the climate projections for the next century in ireland permanent meromictic conditions will probably continue

micromorphology and classification of argids and associated gypsiferous aridisols from central iran abstract gypsiferous aridisols occupy the largest area within the iranian aridisols information on the genesis and classification of these soils is rather limited objectives of this research were to study the micromorphology of the gypsic argillic and calcic horizons to understand the mode of formation of gypsic horizon in three different landscapes and to test the criteria of the most recently revised soil taxonomy and fao classification system in selected gypsiferous aridisols occurring in central iran a total of 15 representative pedons occurring on three different landscapes colluvial fans plateaus and alluvial plain were studied evidence of illuviation in the colluvial soils is provided by the increase in the clay content and the fine to total clay ratio in the subsoil and by the well developed but considerably disrupted clay coatings observed in thin sections in addition to pendants gypsum occurs as microscopic sized particles such as single and radiating fibrous shaped particles random lenticular and granular crystals along channels and planar voids with no apparent orientation to the associated surface gypsum also occurs as relatively larger interlocking plates the horizon sequence together with their chemical and micromorphological properties reveals that gypsum accumulated in different landscapes has different modes of formation the coexistence of argillic calcic and gypsic horizons in colluvial soils is a peculiar combination suggesting a multistage pedogenesis in this landscape paleo argillic horizons were likely developed under a moister environment than today this study has also shown that the most recently revised version of the american soil taxonomy and fao soil classification can reasonably well classify these soils however there is still a need to modify the criteria of both classification systems at the lower levels particularly for the classification of the soils that are polygenetic