fabric evolution in salem attur shear zone south india and its implications on the kinematics abstract domains of opposing shear sense relative to the overall kinematic framework often add to the ambiguities in the interpretation of movement picture along major shear zones rheologic properties strain partitioning as well as rotation of fabric are the principal mechanisms that contribute to the evolution of fabric during shearing the relative dominance of these mechanisms varies with progressive strain leading to the development of domainal fabric departing from the regional stress strain vectors the salem attur shear zone exhibits imprints of multiphase shearing and domains of meso to micro fabrics indicating opposing shear sense resulting in conflicting interpretations of the regional kinematics since the sense of movement is a major constraint in matching the shear zones in gondwana fragments this paper focuses on understanding the movement picture of the shear zone and the mechanism of evolution of domainal fabric

biological remains geochemistry and stable isotopes for the reconstruction of environmental and hydrological changes in the holocene lakes from north sahara abstract a detailed reconstruction of the holocene palaeoenvironments and palaeohydrology is presented for wwamp and lacustrine calcareous sediments which lie in closed depressions along the northern margin of the great western erg algeria it is based on a multidisciplinary approach using numerous techniques the chronological framework is established on the basis of 23 14 c dates on inorganic calcite and mollusc shells ranging from ca 9300 to 3000 yr b p and on an isolated 14 c age of ca 10 900 yr b p the significance of various environmental markers is discussed biological remains are abundant and diversified about 150 taxa including diatoms chrysophytes charophytes ostracods molluscs and foraminifera they provide information on the water chemistry total salinity ionic ratio ph and partial pressure of carbon dioxide and on the habitats water depth development of aquatic plants ephemerality etc emphasis is given to the total salinity individual organisms and palaeobiological assemblages are ordered as a function of their salt requirements and tolerances calibration based on modern diatom samples allows a tentative estimate of the palaeosalinities which range from fresh to marine like and even hypersaline waters attention is drawn to the possible colonization of marine organisms in continental basins without any connection with the sea stable isotope analyses have been carried out on both inorganic and biogenic mollusc and ostracod shells charophyte gyronites carbonates the 18 o contents demonstrate wide changes in the hydrological balance fluctuations in 13 c contents inform on water mixing residence time and on the importance of biological effects on total dissolved inorganic carbon geochemical analyses were performed on inorganic calcite and on ostracod shells high contents in fe and mn indicate reducing environments during stages of high salinity sr ca and mg ca are used as salinity indicators zn mg ratios suggest that the major water supply was the aquifer of the great western erg today down to about 50 m rather than surface waters from the atlas mountains salinities resulted from the balance between inputs from the water table evaporation rate leaching of pre existing salt crusts and seepage through the lake bottom a reconstruction of the evolution of the palaeosystems through time and space has been attempted with special attention to the instability of the water and ionic balances for different time scales short term fluctuations occurring during a single hydrological cycle annual or seasonal are deduced from the apparent discrepancies between the various indicators found in a given sample long term 10 2 10 3 years changes confirm the existence of a climatic phase being wetter than today from at least ca 9300 and may be from ca 10 900 yr b p to 3000 yr b p for the first time the salinity deduced from diatoms and the 18 o content of the water deduced from that of the carbonate at 25 c are used simultaneously to model the hydrological history of the basins and to estimate the relative humidity of the atmosphere during the holocene major environmental trends recorded from ca 9300 to 3000 yr b p do not show a clear synchronims between the different profiles studied therefore they cannot be interpreted in terms of palaeoclimate but instead demonstrate the importance of local hydrology in the evolution of closed basins associated with groundwater a common situation in arid and semi arid zones

how accurate are 234th measurements in seawater based on the mno2 impregnated cartridge technique in the past decade a mno2 impregnated cartridge technique has been widely used to extract 234th from seawater one of the inherent assumptions associated with this technique is that all th species in the dissolved phase are subject to extraction by the mno2 cartridges in this study an intercalibration between the cartridge technique and a small volume mno2 coprecipitation technique was carried out to test this assumption we demonstrated that the collection efficiency for 234th could be substantially overestimated by the mno2 cartridge technique this may be the result of organic complexation of a significant portion of 234th in seawater causing this fraction of th to pass through the mno2 cartridges the overestimate in collection efficiency may explain the deep water 234th deficit observed in some oceanographic settings e g the gulf of mexico the middle atlantic bight and the gulf of maine sensitivity tests show that using the cartridge technique can yield 234th based particulate organic carbon export rates that are overestimated by factors of up to 10 furthermore the frequent observed disagreements between th fluxes recorded by shallow sediment traps and estimated using the cartridge method may be ascribed at least partially to this methodological issue

dating loess up to 800 ka by thermoluminescence thermoluminescence tl ages agreeing with expected ages have been obtained for 13 loess samples spanning the age range from 20 to 800 ka our samples are from alaska and north island new zealand and are unusual in tl dating studies of loess older than 80 100 ka by having independent age assignments that are generally well constrained from ages of associated tephra beds with the polymineral fine silt sized 4 11 m grains the partial bleach tl technique yielded expected ages up to about 350 ka whereas the total bleach method gave accurate ages in the range 100 to 800 ka thus the much disputed upper age limit of 100 150 ka for the tl dating of loess now appears to be sample and worker dependent rather than a global property of the tl signals in the tl dominant feldspars

vegetation zones in nw africa during the brunhes chron reconstructed from marine palynological data abstract six east atlantic sites between 9 and 35 n allow the reconstruction of the latitudinal position and extension of the nw african vegetation zones during the last 0 7 ma the response of the vegetation to alternating glacial dry and interglacial humid climatic conditions has been recorded the vegetation response to a climatic amelioration starts with the northward expansion of the tropical rain forest followed by the northward shift of the saharan sahelian boundary and ends with the southward shift of the saharan mediterranean transitional steppes and the expansion of the mediterranean oak forests most sensitive is the reaction of the saharan sahelian boundary to climatic change large shifts of the saharan sahelian boundary seem to occur faster than small ones annual precipitation estimates for the latitude of dakar 15 n range from 100 to 1000 mm at 24 n yearly precipitation probably ranged from 0 to 150 mm smallest extent of the guinean tropical rain forest probably occurred during the arid conditions of isotope stages 2 and 6 reducing the carbon fixation of these forests to a minimum large extent of the guinean tropical rain forest occurred during most of the odd isotope stages more humid interglacials

enhanced anticyclonic circulation in the eastern north atlantic during cold intervals of the last deglaciation inferred from deep sea pollen records pollen analyses on two deep sea records recovered in the eastern atlantic between lat 37 and 4 n show two coeval peaks in wind transported terrestrial elements pollen and spores mainly from dry steppe type formations at 15 ka and at 10 3 ka this may reflect the dominance of anticyclonic circulation during the cold phases of the last deglaciation responsible for strong winds leading to the advection of polar air masses equatorward at lat 37 n the predominant influence of the westerlies was established after 9 3 ka

a 300 kyr high resolution aridity record of the north african continent new oxygen isotope data and a high resolution carbonate record of a core from the northwest african margin are presented in combination with geochemical zr rb ratio al ba organic carbon and biogenic opal fluxes and sedimentological median grain size parameters to show variations in african continental aridity wind strength and upwelling productivity the carbonate record is diluted by the supply of aeolian dust from the arid saharan region of north africa and is seen to vary with a characteristic sawtooth pattern indicating rapid increases in dust flux followed by gradual declines spectral analysis of the carbonate profile and comparison with specmap stacked oxygen isotope and etp solar radiation profiles shows that the precessional 23 kyr insolation induced african climate system is decoupled from global ice volume climate changes operating on a 100 kyr frequency detailed studies of glacial terminations i ii and iii confirm the presence of rapid short timescale climatic variations in aridity

u series dating by the tims technique of land snails from paleosols in the canary islands a sequence of seven superimposed paleosols developed on eolian calcarenites and alluvium was sampled on the island of lanzarote in order to examine the possibility of dating land snail shells by the u series method using a tims technique allowing measurement of u and th isotopes in very small samples in the lower six units the fossil shells yielded d allo l isoleucine a i ratios of about 0 5 and apparent ams 14c ages ranging from 41 000 to 34 000 yr b p indicating that most paleosols formed during a relatively short mid wurm humid episode the upper unit paleosol 7 yielded more variable a i ratios ranging from 0 6 to 0 2 and a younger 14c age 27 000 yr b p most samples contained enough u to allow the calculation of u series ages after correction for the presence of a detrital component in samples containing a few tens of ppb of u paleosols 1 2 3 6 and 7 the ages are strongly dependent upon the model used for the correction in samples containing more than 300 ppb of u paleosols 4 and 5 concordant ages of 31 000 1000 yr were obtained regardless of the correction model used u uptake in these shells occurred during one single early diagenetic phase soon after burial since shells of modern snails do not contain any significant amount of u the arid conditions subsequent to the mid wurm humid episode have likely ensured since then a fair closure of the radioactive system

recognition of insufficient bleaching by small aliquots of quartz for reconstructing soil erosion in greece optical dating of sediments requires sufficient bleaching of the material to be dated using single aliquot techniques the statistical parameter of the coefficient of variation v in combination with the reduction of mineral grains per aliquot enables the detection of insufficiently bleached samples this was empirically tested on quartz extracts from the greek study area which were artificially bleached differently dosed and then mixed to simulate insufficiently bleached samples the single aliquot regenerative dose protocol was applied the test measurements show that for the studied quartz material the detection of insufficient bleaching is possible if small aliquots of 200 500 grains and a threshold value of v 10 are used the technique was applied to the age determination of colluvial and alluvial torrential deposits from the study area the basin of phlious in greece the optically stimulated luminescence age data allow reconstruction of the history of holocene soil erosion which essentially started in the 7th millennium bc simultaneous with the onset of agricultural activities in the early neolithic

ice growth and oceanic heat flux models and measurements heat fluxes at the ice ocean interface and ice thickness are investigated by comparing field data from the coordinated eastern arctic experiment cearex drift phase with model calculations the calculations are based on two types of models the first one is a one dimensional ice ocean model with high vertical resolution this model is based on the conservation equations for heat salt and momentum and uses turbulence models to achieve closure a discrete element approach is also introduced to explicitly parameterize the ice roughness the second model is a simple one dimensional bulk heat transfer model in this version the interfacial salinity is modelled on the basis of salt conservation at the ice ocean interface the bulk heat transfer model is then calibrated using the former model the two models predict ocean heat fluxes that are quite variable in time owing to short term variations in the ice drift both models calculate realistic ice thicknesses it is demonstrated that the observed time variation in ice thickness from eight different experimental sites with varying initial thicknesses and bottom topographies can be reproduced by applying bulk heat transfer coefficients in the range 2 8 1 10 4 horizontal variation of the thermal state within a single pack ice floe results in simultaneous freezing and melting over relatively small spatial scales when modeling or averaging ice data in space these aspects need to be considered

response of the u pb chronometer and trace elements in zircon to ultrahigh temperature metamorphism the kadavur anorthosite complex southern india abstract zircon from quartzites in the contact aureole and wider environs of the kadavur anorthosite complex se india was studied by laser ablation icp ms to assess the response of the u pb isotope system and trace element concentrations to ultrahigh temperature uht contact metamorphism 1000 c combined cathodoluminescence imaging and la icp ms analyses show that zircon grains contain detrital cores which yield ages between 3 4 ga and 1 8 ga and exhibit a large spread in ree concentrations these cores are associated with one or two rims that provide concordant age populations at 955 16 ma and 810 7 ma 2 and relatively uniform ree patterns the older ages of ca 955 ma record the imprints of regional early neoproterozoic metamorphism related to rodinia assembly the younger age is interpreted to date anorthosite emplacement and its associated contact metamorphism during a second regional metamorphic episode coeval with the intrusion of a type granites in the area zircon grains from the country rocks away from the anorthosite show additional rims yielding ages from 590 to 490 ma corresponding to regional pan african tectonometamorphism the zircon rims are either newly grown domains or represent recrystallized and re equilibrated parts of precursor zircon discordance is only observed in 25 of the detrital cores these cores have relatively high u concentrations 400 ppm which strongly suggests that pb loss occurred under u ht conditions by partial recrystallization annealing of zircon that had become metamict the preservation of old concordant ages and source ree characteristics by the low u i e weakly to non metamict detrital cores shows that pristine zircon is extremely robust to thermal disturbance and that its u pb systematics can remain unaffected despite multiple u ht metamorphic episodes these observations imply that u pb ages in zircon cannot be reset by volume diffusion under any crustal conditions disturbance of the u pb system in individual zircon crystals or parts thereof can only be achieved by recrystallization of radiation damaged zircon

orbital forcing of dust supply to the north canary basin over the last 250kyr abstract the canary basin lies in a region of strong interaction between the atmospheric and ocean circulation systems trade winds drive seasonal coastal upwelling and dust storm outbreaks from the neighbouring sahara desert are the major source of terrigenous sediment to investigate the forcing mechanisms for dust input and wind strength in the north canary basin the temporal pattern of variability of sedimentological and geochemical proxy records has been analysed in two sediment cores between latitudes 30 30 n and 31 40 n spectral analysis of the dust proxy records indicates that insolation changes related to eccentricity and precession are the main periods of temporal variation in the record si al and grain size of the terrigenous fraction show an increase in glacial interglacial transitions while al concentration and fe al ratio are both in phase with minima in the precessional index hence the results obtained show that the wind strength was intensified at terminations at times of maxima of northern hemisphere seasonal insolation when the african monsoon was enhanced the north canary basin also received higher dust input this result suggests that the moisture brought by the monsoon may have increased the availability of dust in the source region

soil moisture fluctuations recorded in saharan dust deposits on lanzarote canary islands over the last 180 ka abstract aeolian sediments trapped in volcanically dammed valleys on lanzarote canary islands were investigated in order to reveal environmental changes over the last 180 ka clay content and frequency dependent magnetic susceptibility were used as proxies for pedogenesis and palaeo soil moisture during the last 180 ka these proxies showed a general pattern of enhanced soil moisture during glacials and stadials and more arid conditions during interglacials and interstadials comparisons of these results with proxies from regional palaeoclimate studies identified a positive correlation with proxies of trade wind strength off northwest africa and inverse correlations with both sea surface temperatures in the northeast atlantic and the extent of mediterranean vegetation possible causes for the observed pattern include a glacial enhancement of precipitation from westerly cyclones a change in relative humidity due to fluctuating air temperatures and an occasional influence of the african summer monsoon although it is not yet possible to clearly differentiate among these factors it is clear that the first two factors must have been primarily dominant these results represent the first quasi continuous terrestrial data testifying to environmental changes in the northwest african coastal area for the last 180 ka and complement the abundant data derived from marine cores of the region high latitude dynamics had a major influence in this area and were intermediated by north atlantic sea surface temperatures a possible negative correlation can also be observed with the orbital obliquity cycle with a 10 ka time lag which is similar to the lag recorded from north atlantic sea surface temperatures

loess in europe mass accumulation rates during the last glacial period abstract upper pleistocene loess palaeosol sequences provide excellent high resolution terrestrial archives of climate forcing due to improvements in numerical age determinations especially in luminescence dating methods a more reliable time based reconstruction of the past climate and environmental change has become available for the loess record in europe chronological information was collected from 43 sites along a northwest to southeast transect in europe thirty three of these sites had sufficient age information to allow estimation of mass accumulation rates and it was possible to isolate the mass accumulation rates of primary loess during the last glacial period 28 13 ka bp at 21 of these locations these sites fall along a coarse climatic gradient from the relatively coastal climate of belgium and france to the drier more continental climate of central europe interpreting mass accumulation rates of loess in terms of this climatic gradient is not straightforward as these deposits are dominated by sources in floodplains and large river systems thus accumulation rates are influenced strongly by regional wind and precipitation patterns but mostly by the availability of glacially derived material from the alps and the periglacial terrains that characterized european fluvial systems during and immediately following glaciation

higher himalayan shear zone zanskar indian himalaya microstructural studies and extrusion mechanism by a combination of simple shear and channel flow thin section studies of the zanskar shear zone zsz rocks reveal a top to sw and subsequent primary and secondary top to ne ductile shearing brittle ductile and brittle extensions top to sw brittle shear steep normal faulting and fracturing in the proposed two phase model of ductile extrusion of the higher himalayan shear zone hhsz a top to sw simple shearing during 22 18 ma was followed by a combination of top to sw simple shear and channel flow at 18 16 ma the second phase simulates a thin zsz characterized by a top to ne shearing the channel flow component ceased around 16 ma the extruding hhsz entered the brittle regime but the top to sw shearing continued until perturbed by faults and fractures variation in the extrusion parameters led to variable thickness of the zsz shear strain after the extrusion is presumably maximum at the boundaries of the hhsz and falls towards the base of the zsz which crudely matches with the existing data the other predictions 1 spatially uniform shear strain after the first stage 2 fastest extrusion rate at the base of the zsz and 3 a lack of continuation of the zsz along the himalayan trend are not possible to validate due to paucity of suitable data non parabolic shear fabrics of the zsz indicate their heterogeneous deformation

last glacial maximum to early holocene wind strength in the mid latitudes of the southern hemisphere from aeolian dust in the tasman sea dust transported by southern hemisphere mid latitude westerly winds from australia and deposited in the tasman sea shows no evidence for stronger winds during the last glacial maximum lgm compared to the holocene features of the particle size distributions of the dust do however indicate enhanced dry deposition of dust in the lgm changing to rainfall scavenging during deglaciation and the early holocene as climate ameliorated from these results it appears that activation of desert dunefields over 40 of australia during the lgm was the result of a reduction in stabilizing vegetation and more frequent episodes of sand movement rather than of increased wind strength the lgm climate of inland australia must have been considerably more stressful for plants as a result of lower precipitation and or carbon dioxide stress to achieve the implied levels of surface destabilization enhanced atmospheric dust loads in the southern hemisphere and deposition over antarctica were most likely the result of greatly expanded source areas in the mid latitude southern continents and a weaker hydrological cycle rather than greater entrainment or more efficient transport by stronger winds during the lgm wind strength appears to have varied regionally and predominantly in high latitudes rather than uniformly for all zonal winds

storminess control over african dust input to the moroccan atlantic margin nw africa at the time of maxima boreal summer insolation a record of the last 220 kyr abstract precessional forcing of dust flux from northwest africa to the atlantic during the last 220 kyr is recognised through changes in physical and chemical sediment properties sediment colour reflectance magnetic susceptibility x ray fluorescence element intensity in a core from the moroccan margin sediment colour reflectance magnetic susceptibility and ca and fe element intensity changes are thought to be driven by dust input from north africa spectral analysis of the sediment properties records displays a dominant periodicity in the 1 23 kyr 1 frequency band that is associated with the earth s orbital precession peaks in terrigenous supply match precessional minima this suggests a close link between maxima of boreal summer solar radiation monsoon activity and dust generation enhanced precession driven solar radiation would have caused increased seasonal temperature contrasts which amplified atmospheric turbulence and stimulated storminess such a scenario is similar to today s summer conditions when frequent storms cause distinct dust plumes to form in the area and transport fine terrigenous material to the adjacent north atlantic ocean

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

loess like and palaeosol sediments from lanzarote canary islands spain indicators of palaeoenvironmental change during the late quaternary abstract on lanzarote canary islands quaternary saharan dust and weathered local volcanic material were trapped in miocence to pliocene valleys dammed by younger volcanic edifices these sediments show sequences of alternating reddish clayey and loess like yellowish silty material in order to investigate if reddish clayey layers contain material derived from local pedogenesis and if so which pedogenetic processes were active we performed sedimentological micromorphological and environmental magnetic analyses the analyses demonstrate that these layers contain material derived from local soils these soils were characterised by clay formation rubefication and the formation of superparamagnetic particles during periods of enhanced soil moisture thus they can serve as natural archives in order to reconstruct the terrestrial palaeoclimatic history of lanzarote the distribution of soil material in the profiles shows that cold periods of the late quaternary were characterised by more humid conditions than today using palaeontological remains and a comparison with recent soils on tenerife we can roughly estimate maximal palaeoprecipitation values during more humid periods

hotspot volcanism close to a passive continental margin the canary islands the canarian archipelago is a group of volcanic islands on a slow moving oceanic plate close to a continental margin the origins of the archipelago are controversial a hotspot or mantle plume a zone of lithospheric deformation a region of compressional block faulting or a rupture propagating westwards from the active atlas mountains fold belt have been proposed by different authors however comparison of the canarian archipelago with the prototypical hotspot related island group the hawaiian archipelago reveals that the differences between the two are not as great as had previously been supposed on the basis of older data quaternary igneous activity in the canaries is concentrated at the western end of the archipelago close to the present day location of the inferred hotspot this is the same relationship as seen in the hawaiian and cape verde islands the latter archipelago associated with a well defined but slow moving mantle plume shows anomalies in a plot of island age against distance which are comparable to those seen in the canary islands these anomalies cannot therefore be used to argue against a hotspot origin for the canaries individual islands in both archipelagoes are characterized by initial rapid growth the shield building stages of activity followed by a period of quiescence and deep erosion erosion gap which in turn is followed by a post erosional stage of activity the absence of post shield stage subsidence in the canaries is in marked contrast with the major subsidence experienced by the hawaiian islands but is comparable with the lack of subsidence evident in other island groups at slow moving hotspots such as the cape verdes comparison of the structure and structural evolution of the canary islands with other oceanic islands such as hawaii and reunion reveals many similarities these include the development of triple mercedes star rift zones and the occurrence of giant lateral collapses on the flanks of these rift zones the apparent absence of these features in the post erosional islands may in part be a result of their greater age and deeper erosion which has removed much of the evidence for their early volcanic architecture we conclude that the many similarities between the canary islands and island groups whose hotspot origins are undisputed show that the canaries have been produced in the same way

the distribution of apparent dose as determined by optically stimulated luminescence in small aliquots of fluvial quartz implications for dating young sediments abstract we noted recently murray et al 1995 that quartz samples taken from in channel fluvial deposits have apparent doses ranging over several orders of magnitude we suggested that these dose distributions are best explained by a mixture of a small number of poorly bleached grains and a larger number of well bleached grains in this paper we examine the distribution of apparent dose in small aliquots each composed of 2000 grains of different particle size fractions 63 90 m 90 125 m 125 180 m 180 212 m 212 250 m diameter from two samples collected from the murrumbidgee river new south wales australia the samples are of known burial age the first being 70 years old and the second being its modern equivalent 0 2 gy the difference in the lowest apparent dose in the two samples is considered to be the result of their different burial times we suggest a method for dating recently deposited

geomorphological investigations of sediment traps on lanzarote canary islands as a key for the interpretation of a palaeoclimate archive off nw africa abstract on lanzarote canary islands late quaternary saharan dust and volcanic material were trapped in miocence to pliocene valleys dammed by volcanic lava flows these trapped sediments are potentially interesting as they can be natural archives useful to reconstruct the terrestrial palaeoclimate history of the nw african margin nevertheless slope wash processes altered the primarily eolian deposits making climatic interpretation not straightforward geomorphological mapping gis calculations and sedimentological investigations were used to unravel these processes influencing the temporal resolution of the palaeoclimatic archive demonstrating that they average the palaeoclimatic signal by some ka thus despite the colluvial geomorphic environment the valley fillings can be used for palaeoclimatic interpretation of events with a length of at least some ka the youngest sediments deposited since at least 2 5 ka are anthropogenically triggered and thus cannot be used for palaeoclimatic interpretation the results show that the input of saharan dust at lanzarote increased during the last 1 0 ka and especially during the early middle holocene

long range transport of giant aeolian quartz grains linkage with discrete sedimentary sources and implications for protective particle transfer abstract several articles have documented the presence of large particles 62 5 m that have been transported great distances 1000 km through the atmosphere at present we do not understand the mechanisms that lead to mineral grains being carried aloft far beyond the limits imposed by conventional gravitational settling models typically marine geologists refer to ice rafting and or advective transport by ocean currents as the dominant transport processes that deliver large mineral grains to deep sea sediments textural analyses of giant quartz grains from six sedimentary deposition events collected from various sources including a single site in the north pacific ocean and sites in the british isles and france strongly support the idea that in each case all of the grains were initially eroded from a discrete sediment type and often a discrete point source and subsequently transported via the atmosphere to our sampling sites up to 10 000 km away these findings suggest that at least at times erosional events fuelling long distance atmospheric transport are exceedingly specific and operate upon geologically distinctive assemblages and are able to effect long distance transfer of large grains with no grain to grain collisions this work also suggests that atmospheric transport should be included as a possible means of delivery for significant quantities of giant sedimentary particles to remote marine sites such as the lord howe rise

complexity of quaternary aeolian dynamics canary islands abstract carbonate aeolianites are important quaternary archives at the point of intersection between marine and terrestrial systems since they are composed of alternating aeolian sediments and several paleosol units these sequences are highly suitable to reconstruct palaeoenvironmental conditions in northern fuerteventura at least five different areas are characterised by successions of different dune generations and paleosols few studies have addressed the stratigraphic order of individual dune areas therefore a comprehensive consideration spanning several dune fields is needed here we aim to present a detailed stratigraphy of two different dune areas and to identify the contribution of different materials shelf origin dust origin volcanic origin along with processes accumulation soil formation erosion preservation that build up these archives four key sections were selected and sampled for laboratory analyses texture elemental composition caco3 content palaeoenvironmental magnetics luminescence dating and gastropod assemblages based on main stratigraphic features five major sedimentary sequences were identified indicating differences in prevailing sediment supply humidity and volcanic activity first luminescence dating irsl of the sequences revealed sedimentation ages between 360 ka and 15 ka finally we are able to demonstrate that different dune areas show comparable stratigraphic patterns but each studied site is defined by certain characteristics depending on the respective features of the closer surrounding the knowledge of these peculiarities and the underlying background is essential in order to correlate different sites and to attempt an appropriate environmental interpretation of the sedimentary sequences

structural fabric of the southern indian shield as defined by gravity trends abstract southern indian shield represents a mosaic comprised of several smaller structural domains separated by discrete shear zones here we present a horizontal bouguer gravity gradient map of the indian shield south of 14 n to define a continental mosaic of gravity trends domains akin to structural domains the gravity gradient image is based on 7862 newly collected observations merged with 6359 old gravity data this combined dataset delineates structural boundaries of the five gravity domains related to the eastern dharwar craton the eastern ghats mobile belt the extended eastern ghats mobile belt the southern granulite terrain and the western dharwar craton other belts of significant gravity gradients are found associated with the eastern and the western coasts the loci of closepet granite and kolar schist belts do not manifest themselves as boundary zones between two distinct gravity domains of the eastern dharwar craton lack of a gravity gradient across karur oddanchatram kodaikanal and karur kambam painavu trichur shear zones may be attributed to a lack of gravity measurements caused by difficulties in collecting data in topographically difficult terrain the subdued gravity gradient across the palghat cauvery shear zone and a weak gradient across the achankovil shear zone indicates a lithological and or morphological boundary rather than a terrane boundary alternatively structural domains encompassing palghat cauvery and achankovil shear zones may have been in a neighbouring position during the gondwana assembly when pan african thermal perturbation reactivated the structures and reworked partly or totally obliterating earlier crustal fabric

holocene climatic change in morocco a quantitative reconstruction from pollen data annual precipitation july and january temperatures were reconstructed from a continuous holocene pollen sequence from the middle atlas morocco using the best modern analogues method the reconstructions show a clear difference between the early and late holocene from 10 ka to 6 5 ka the climate was drier and warmer than during the period since 6 5 ka the average value of annual precipitation was 870 mm until 6 5 ka then rose to 940 mm between 10 ka and 6 5 ka january and july temperatures were about 4 c higher than the present both temperatures show a marked decrease between 7 ka and 6 ka after 6 5 ka july and january temperatures fluctuated between 21 and 23 c and 2 5 and 5 c respectively january temperatures show a period of intermediate values 3 5 c between 4 ka and 5 5 ka the reconstructed climate values generally match palaeolimnological data from the same core which show five intervals of low lake level during the holocene they are also consistent with regional scale cohmap simulated palaeoclimate that shows contrasting patterns of rainfall variation between the northwesternmost part of africa and the intertropical band

east asian monsoon variation during the last 130 000 years evidence from the loess plateau of central china and lake biwa of japan abstract the loess paleosol sequence on the loess plateau of central china constitutes an excellent proxy record of variations in asian monsoon climate over the past 2 5 ma magnetic susceptibility of loess and paleosols has been used as a proxy indicator for summer monsoon intensity while the median diameter of quartz isolated from the loess and paleosols has been regarded as a proxy index of the strength of winter monsoon winds that were responsible for most of the dust transport the eolian quartz flux to lake biwa of central japan during the last 130 000 yr provides direct information on variations of the east asian winter monsoon whereas the fluvial quartz flux reflects significant changes in paleoprecipitation over the lake area the intervals of high eolian quartz flux values during marine oxygen isotope substages 5d and 5b and stages 4 and 2 correspond to the periods of large quartz median diameter values of the chinese loess and paleosols indicating strengthened winter monsoon winds whereas the intervals of high fluvial quartz flux values during isotope substages 5e 5c and 5a and stages 3 and 1 correlate to the periods of high magnetic susceptibility values of the chinese loess and paleosols suggesting increased summer monsoon intensity variations in winter monsoon strength indicated by the eolian quartz flux and quartz median diameter proxies bear a general inverse relation to those in summer monsoon intensity inferred from the fluvial quartz flux and magnetic susceptibility proxies

new constraints on the early formation of the western dharwar craton india from igneous zircon u pb and lu hf isotopes abstract the western dharwar craton wdc is an archean crustal segment for which the earliest stages of development have remained poorly constrained because the oldest identified lithologies are chronologically indistinguishable despite vastly different compositions and origins i e 3352 110 ma sargur group komatiites and 3342 6 ma hassan gorur ttg gneiss indication for older crust come from ancient detrital zircons 3450 3610 ma although their genetic link to the wdc is purely conjectural in order to bring new understanding to early development of the wdc we studied orthogneisses around the holenarsipur schist belt hsb for their petrography major oxide concentrations zircon u pb geochronology and lu hf isotope systematics our results reveal that the wdc igneous record contains crust older than 3350 ma in the form of a 3410 8 3 6 ma granitic gneiss and inherited zircons with ages ranging from 3295 18 to 3607 16 ma that were found within a 3178 10 ma trondhjemitic gneiss and a biotite rich enclave found within it the presence of muscovite and the peraluminous signature of the granitic gneiss in spite of mildly depleted hf isotopic signature ehf 2 2 0 6 at 3410 8 ma suggest that this sample formed by reworking of a felsic precursor with short crustal residence time possibly marking the beginning of wdc formation the oldest inherited zircons display variable ehf ranging from 10 4 at 3414 ma to 2 3 at 3607 ma that did not seem to have influenced the hf isotopic composition of granitoids of the wdc that formed between 3200 and 3410 ma except perhaps in the sargur area we suggest that the wdc formed remote from continental crust until a crustal block containing 3410 ma zircons was accreted to it 3200 my ago this event resulted in the stabilization of the wdc which is marked by diapiric granitoids to which the 3178 ma trondhjemitic gneiss belongs after 3200 ma the crustal block together with granitoids formed between 3410 and 3200 ma buffered the hf isotopic signature of newly formed granitoids hence indicating that by then the wdc already was a stable continental segment

dust transport and the question of desert loess formation although contemporary dust storms are frequent in arid and semi arid areas desert loess deposits are poorly developed much of the world s loess occurs in mid latitude areas which experienced glaciation during the pleistocene ocean core evidence indicates that dust transport from sub tropical deserts increased during cold stages of the pleistocene but loess formed only on certain desert margins for reasons which have not been fully explained this paper re examines the mechanisms of dust transport and deposition and the circumstances leading to the accumulation of thick loess typical loess is composed mainly of medium silt grains which are transported in short term suspension a few metres above the ground significant thicknesses of loess form only when dust is trapped within a limited area often relatively close to the source dust particles finer than 20 m are transported mainly in long term suspension over a greater height range and may be widely dispersed the availability of silt and the frequency magnitude and direction of dust transporting winds are important factors governing the potential for loess formation but the existence of a suitable dust trap is particularly important traps may be formed by topographic obstacles areas of moist ground or vegetated surfaces vegetation adjacent to glacial outwash plains and braided meltwater streams trapped dust in mid latitudes during the pleistocene dust blown during glacial periods from certain deserts notably in sinai soviet central asia and china accumulated as loess in neighbouring semi arid regions on the margins of other deserts loess formation was inhibited partly by the absence of vegetation traps during most of the holocene net dust deposition rates in all desert marginal areas have been too low for significant loess accumulation this is mainly due to a reduction in silt availability and a tendency towards landscape stability reported dust storm frequencies during the past 50 years over estimate the longer term holocene dust flux due to the effects of human activities much modern dust owes its origin to erosion of cultivated soils in semi arid areas and is finer than typical loess

synoptic and seasonal variations of the ice ocean circulation in the arctic a numerical study abstract the circulations of the arctic ice cover and ocean are investigated using a coupled ice ocean model the coupling is strong and two way for synoptic time scales but is limited on seasonal time scales the geostrophic ocean currents are not changed by the computed heat and salt fluxes the ice drift motion ekman transports and the wind driven part of the barotropic circulation are examined for the months of february and august 1986 representing different atmospheric forcing ice thickness and ice strength regimes initial examination of the results revealed no significant seasonal dependence of ice drift response on the synoptic time scale other than larger velocities with larger wind stresses daily maximum ice drift velocities range from 20 40 cm s in february and 15 30 cm s in august the corresponding mean monthly maximum drifts were 11 and 9 cm respectively the drag associated with the geostrophic currents plays a much bigger role in the summer because of the lighter atmospheric stresses the well known reversal of the normally clockwise beaufort gyre to a cyclonic system in august takes place in a few days and lasts well into september in february the beaufort gyre varies between a large clockwise system covering all the canadian basin to a small tight gyre centered over the southern beaufort sea without any hint of reversal or disappearance large areas of strong divergence were found in the ekman transport patterns as well as the ice divergence fields indicating areas where ice thinning openings and new ice formation might occur in august this occurred in the chukchi sea and in february just north of novaya zemlya

osl dating of coarse grain fluvial quartz using single aliquot protocols on sediments from ne peloponnese greece abstract optical ages of quartz extracts in holocene sediments from the north eastern peloponnese greece are reported the single aliquot regenerative dose protocol proposed by murray and wintle 2000 radiation measurements 32 57 73 was used to estimate the equivalent dose in these samples a large inter aliquot scatter in d e values was observed for all samples this is ascribed to heterogeneous bleaching of the samples at deposition to estimate a d e for age calculation a technique is suggested based on the analysis of the d e scatter obtained from nine different quartz samples which were artificially bleached and irradiated this procedure is especially useful when the sample quantity is limited the optical age estimates increase with sampling depth an average aggradation rate of 1 5 mm yr is derived using the osl ages this value is consistent with the known uplift rate of 1 2 mm yr

the evolution of saharan dust input on lanzarote canary islands influenced by human activity in the northwest sahara during the early holocene an overall holocene increase of saharan dust input to the canary islands and to the north canary basin is accompanied by a strong coarsening of saharan dust in loess like sediments deposited on lanzarote from 7 8 ka no similar coarsening events are indicated in investigations of the sedimentological record for the last 180 ka a period showing several dramatic climate changes therefore a mobilisation of holocene dust by anthropogenic activity in the northwest sahara east of the canary islands is assumed although scarce archaeological data from the coastal area of that region does not point to strong anthropogenic activity during the early holocene a high density of unexplored archaeological remains is reported from the coastal hinterlands in the western sahara thus the hypothesis of early anthropogenic activity cannot be excluded

nature of the crust along kuppam palani geotransect south india from gravity studies implications for precambrian continental collision and delamination abstract closely spaced 3000 gravity measurements around kuppam palani geotransect indicate the presence of an ancient continental collision along the moyar bhavani mettur shear zone and crustal delamination beneath the palghat gap paired gravity anomaly along with the faulted contact dip reversal in seismic reflectivity pattern northward vergence of the southern domain and high pressure temperature granulites exposed on the shevaroy hills are characteristic features of crustal thrusting through a late archaean continental collision along the moyar bhavani mettur shear zone a unified 2 1 2 d gravity model along the seismic line is consistent with a tectonic history in which the eastern dharwar craton has been transported beneath the southern granulite terrain the gravity modeling further defines a 10 km thick high density 2 89 g cm3 crustal body at 10 15 km depth and a moho warped up to a depth of about 38 km beneath the palghat gap the high density intrusive body together with the upwarped moho signifies the crust mantle interaction in the palghat gap region late archaean continental collision and subsequent delamination are suggested as the twin cause mechanism for the present day crustal configuration along the geotransect

on eustatic sea level history last glacial maximum to holocene abstract this paper addresses the question of the magnitude and time dependence of the globally averaged eustatic rise of sea level that occurred subsequent to the time of last glacial maximum lgm at approximately 21 000 calendar years before present through the analysis of relative sea level rsl histories predicted by a realistic mass conserving and gravitationally self consistent theory of postglacial sea level change it is demonstrated that there are preferred oceanic locations at which this eustatic function is well approximated by local sea level history one such location is the island of barbados in the caribbean sea a site from which a coral based record exists that extends from mid holocene to lgm because of the sea level ambiguity that is inherent to coral based records however it is important that the global ice equivalent eustatic sea level curve inferred on the basis of the barbados data be tested against observations at other locations from which similarly extensive records are also available but which are derived on the basis of sea level indicators which are not subject to the ambiguities inherent to corals it is shown that when the eustatic function employed in the global theoretical model is tuned so as to enable the model to fit the barbados observations where the maximum relative sea level rsl depression is assumed to be near 120 m then the theory misfits the record from the sunda shelf in the indonesian archipelago as well as the record from j bonaparte gulf in northern australia both of these recently published records appear to constrain the lgm low stand of rsl to a value above 120 m the implications of these results for interpretation of the long coral derived records from the huon peninsula of papua new guinea and the island of tahiti are also discussed

an assessment of human versus climatic impacts on holocene soil erosion in ne peloponnese greece soil erosion is a natural geomorphological process which can be triggered by both natural climate tectonics or both and anthropogenic e g agriculture perturbation of the ecosystem evidence has accrued that the holocene climate experienced large fluctuations in amplitude and suggestions of human impact on the ecosystem provided by the neolithic revolution dating back to the early holocene have been made the question of whether man or climate was the dominant factor responsible for holocene soil erosion remains unresolved to resolve the reasons for holocene sediment redistribution high resolution chronometric data on sediments derived from colluvial and alluvial archives from southern greece were obtained and combined with available archaeological and paleoclimatic data from the eastern mediterranean these data show a significant correlation between sedimentation rates and settlement history climatic fluctuations are only weakly correlated with sedimentation history the results show high sedimentation rates during the early neolithic 7th millennium bc in southern greece suggesting that holocene soil erosion was triggered by human activity and then amplified by enhanced precipitation this would explain the high sedimentation rates during the early neolithic in connection with enhanced precipitation in the eastern mediterranean which continued until the mid holocene

late pleistocene and holocene dune activity and wind regimes in the western sahara desert of mauritania the western sahara desert in mauritania is dominated by extensive sand seas consisting largely of linear dunes analyses of landsat images geomorphic and stratigraphic studies and optically stimulated luminescence dating of dunes in the azefal agneitir and akchar sand seas provide evidence that three main generations of dunes were formed during the periods 25 15 ka centered around the last glacial maximum 10 13 ka spanning the younger dryas event and after 5 ka the wind regimes that occurred during each of these periods were significantly different leading to the formation of dunes on three distinct superimposed trends northeast north northeast and north and the development of the sand seas as composite geomorphic features

north atlantic control on precipitation pattern in the eastern mediterranean black sea region during the last glacial based on proxy records from western black sea cores we provide a comprehensive study of climate change during the last glacial maximum and late glacial period in the black sea region for the first time we present a record of relative changes in precipitation for nw anatolia based on variations in the terrigenous supply expressed as detrital carbonate concentration the good correspondence between reconstructed rainfall intensity in nw anatolia and past western mediterranean sea surface temperatures ssts implies that during the glacial period the precipitation variability was controlled like today by mediterranean cyclonic disturbances periods of reduced precipitation correlate well with low ssts in the mediterranean related to heinrich events h1 and h2 stable oxygen isotopes and lithological and mineralogical data point to a significant modification in the dominant freshwater sediment source concomitant to the meltwater inflow after 16 4 cal ka bp this change implies intensification of the northern sediment source and with other records from the mediterranean region consistently suggests a reorganization of the atmospheric circulation pattern affecting the hydrology of the european continent the early deglacial northward retreat of both atmospheric and oceanic polar fronts was responsible for the warming in the mediterranean region leading simultaneously to more humid conditions in central and northern europe

climatic cycles inferred from the aminostratigraphy and aminochronology of quaternary dunes and palaeosols from the eastern islands of the canary archipelago aminochronological and aminostratigraphical methods have been used to study the quaternary a e o l i a n deposits f r om the islands located east of the canary archipelago fuerteventura and lanzarote islands and la graciosa montana clara and alegranza islets t h e extent of racemisation epimerisation of four amino acids isoleucine aspartic acid phenylalanine and glutamic acid was measured in land snail shells of the genus theba the age calculation algorithms of these amino acids h a v e b e e n determined to permit t he numerical dating of these deposits eight a m i n o z o n e s e a ch defining dune palaeosol formation episodes have been distinguished and dated at 4 8 6 6 4 42 5 6 0 37 8 4 6 29 4 4 8 22 4 4 5 14 9 3 6 11 0 4 0 and 5 4 1 1 ka b p t h e first f i ve of t h em defining c y c l e s of 5 7 ka the alternation of palaeosols and a e o l i a n deposits w h i c h are related to abrupt transitions from humid to arid conditions are t he reflection of globally induced changes in north africa palaeoenvironmental conditions linked to the effect of african palaeomonsoons on the trade w i n d s and the saharan air layer probably these a eolian cycles with a recurrence neriod of 5 7 ka are t he expression of multiples of the 2 4 ka solar cycle

implications of channel flow analogue models for extrusion of the higher himalayan shear zone with special reference to the out of sequence thrusting the higher himalayan shear zone hhsz contains a ductile top to n ne shear zone the south tibetan detachment system lower stdsl and an out of sequence thrust oost as well as a top to n ne normal shear at its northern boundary and ubiquitously distributed compressional top to s sw shear throughout the shear zone the oost that was active between 22 ma and the holocene varies in thickness from 50 m to 6 km and in throw from 1 4 to 20 km channel flow analogue models of this structural geology were performed in this work a newtonian viscous polymer pdms was pushed through a horizontal channel leading to an inclined channel with parallel and upward diverging boundaries analogous to the hhsz and allowed to extrude to the free surface a top to n ne shear zone equivalent to the stdsu developed spontaneously this also indirectly connotes an independent flow confined to the southern part of the hhsz gave rise to the stdsl the pdms originally inside the horizontal channel extruded at a faster rate through the upper part of the inclined channel the lower boundary of this faster pdms defined the oost the model oost originated at the corner and reached the vent at positions similar to the natural prototype some time after the channel flow began the genesis of the oost seems to be unrelated to any rheologic contrast or climatic effects profound variations in the flow parameters along the hhsz and the extrusive force probably resulted in variations in the timing location thickness and slip parameters of the oost variation in pressure gradient within the model horizontal channel however could not be matched with the natural prototype channel flow alone presumably did not result in southward propagation of deformation in the himalaya

cretaceous to cenozoic evolution of the northern lhasa terrane and the early paleogene development of peneplains at nam co tibetan plateau abstract highly elevated and well preserved peneplains are characteristic geomorphic features of the tibetan plateau in the northern lhasa terrane north northwest of nam co the peneplains were carved in granitoids and in their metasedimentary host formations we use multi method geochronology zircon u pb and u th he dating and apatite fission track and u th he dating to constrain the post emplacement thermal history of the granitoids and the timing and rate of final exhumation of the peneplain areas la icp ms u pb geochronology of zircons yields two narrow age groups for the intrusions at around 118 ma and 85 ma and a third group records paleocene volcanic activity 63 58 ma in the nam co area the low temperature thermochronometers indicate common age groups for the entire nam co area zircon u th he ages cluster around 75 ma apatite fission track ages around 60 ma and apatite u th he ages around 50 ma modelling of the thermochronological data indicates that exhumation of the basement blocks took place in latest cretaceous to earliest paleogene time by middle eocene time the relief was already flat documented by a thin alluvial sediment sequence covering a part of the planated area the present day horst and graben structure of the peneplains is a late cenozoic feature triggered by e w extension of the tibetan plateau the new thermochronological data precisely bracket the age of the planation to early eocene i e between ca 55 and 45 ma the erosional base level can be deduced from the presence of early cretaceous zircon grains in eocene strata of bengal basin the sediment generated during exhumation of the nam co area was transported by an early cenozoic river system into the ocean suggesting that planation occurred at low elevation

molecular stratigraphy of cores off northwest africa sea surface temperature history over the last 80 ka the molecular stratigraphy of biogeochemical oceanic flux study core 31k 19 n 20 10 w and ocean drilling program hole 658c 20 45 n 18 35 w has been studied for c37 alkenone abundances over the past 80 ka at high resolution circa 200 500 years the derived uk37 sea surface temperature record for both cores shows a range of temperatures from about 18 c during the last glacial to 21 5 c during the early holocene both records also reveal changes in sea surface temperature as much as 2 4 c over a few hundred years which correlate well with similar abrupt climatic changes observed in cores from elsewhere in the ne atlantic associated with heinrich events our results indicate that meltwater produced by these ice rafting events was transmitted southward by the canary current where it had considerable impact on sea surface temperatures in the subtropical eastern atlantic

optical dating studies of quartz and feldspar sediment extracts abstract continuing developmental work into optical dating has led to some clarification of the optical behaviour of quartz and feldspar sediment extracts we have verified the key assumption intrinsic to the method that the optical signal is zeroed completely upon exposure to daylight we also show that the rate of zeroing in optical dating is much more rapid than it is in tl dating studies concerned with the extraction of the thermally stable signal from laboratory irradiated samples showed that problems may arise from medium to high temperature preheating of young samples optical alternatives to thermal stabilization were tested using dye and krypton lasers using a krypton laser we have succeeded in obtaining an equivalent dose of 0 0 0 7 gy for the quartz from a modern intertidal sand and an average dose of 120 22 gy for the feldspar extract of a 70 ka sand unit both were obtained using six wavelengths from the infrared to the violet and no dependence on wavelength was found we found that the photon energies of infrared and deep red light can stimulate luminescence in unirradiated quartz and feldspar extracts of sediments this was not expected and suggests that the process of trap emptying is more complex than we had envisioned but implies a far greater than expected degree of technical flexibility for the optical dating method

isotopic evidence for the eolian origin of quartz and mica in soils developed on volcanic materials in the canary archipelago quartz and mica contents of soils developed on volcanic materials in the canary archipelago lanzarote tenerife gomera and la palma islands off western africa are often higher in surficial horizons with higher rainfall and older landscape age the soil quartz particles are fine grained less than 53 m in diameter and well sorted the oxygen isotopic abundance 18osmow of fine aerosol sized quartz 1 10 m in diameter showed a range of 16 0 to 18 2 the values are compatible with those of the same sized quartz from two holocene deep sea sediments in cape verde rise 16 0 and 16 1 and saharan dusts 15 8 la laguna tenerife 16 2 barbados west indies a distinct 87sr 86sr ratio of 0 717 for a micaceous horizon from lanzarote is comparable with those of saharan dusts 0 715 to 0 721 but not with reported values 0 7032 from local volcanics these geochemical parameters show that the fine grained quartz together with mica in soils of the canary archipelago are transported from north african sahara deserts by trade winds and negate both possibilities of authigenesis and inheritance from weathering of local volcanics

continental record of the southwest monsoon during the last 130 ka evidence from the southern margin of the thar desert india abstract field stratigraphy sedimentology and luminescence dating of the exposed fluvial and aeolian sequences from the southern desert margin were used to discern the pattern of southwest monsoon variability during the last 130 ka the sedimentary architecture and textural attributes of the sediments belonging to the period 130 120 ka suggests the existence of a meandering river system consequent to enhanced southwest monsoon conditions a shift from a meandering to a braided pattern during 120 100 ka indicates a phase of reduced precipitation presence of flood plain fines and bedded calcretes during 100 70 ka suggest a period of enhanced monsoon with seasonality following this a phase of weak monsoon activity was observed during 70 60 ka regional flood plain aggradation and pedogenesis during the period termination of a regional fluvial phase around 30 ka and incision of dunes dated to 20 11 ka suggest that the present rivers occupied their course between 11 ka drowned valleys in the estuarine zones suggest that the incision began during the low sea stand around 20 ka when the rivers were graded to the exposed shelf the incision intensified with the re establishment of monsoon during the early holocene

3d lithosphere density structure of southern indian shield from joint inversion of gravity geoid and topography data abstract we present the 3d crustal and lithospheric structure and crustal average density distribution of southern indian shield south of 18 n sri lanka and adjoining oceans the model is based on the assumption of local isostatic equilibrium and is derived from joint inversion of free air gravity and geoid anomalies and topography data the derived crustal thickness of 10 25 km in the oceanic region increases to 34 35 km along the coast a crustal thickness of 34 38 km is obtained beneath the eastern dharwar craton and 36 45 km beneath the western dharwar craton and the southern granulite terrain sri lanka has a thinner crust of 30 35 km the lithosphere asthenosphere boundary is located at depths of 70 120 km under oceanic regions and 150 180 km below the dharwar craton and the northern block of southern granulite terrain a notably thinned lithosphere of 130 km near bangalore in the eastern dharwar craton 140 km beneath the southern block of southern granulite terrain and 130 km in sri lanka is observed the thickness of the lithosphere 130 km near bangalore is inferred as the frozen in signature of a small fossil mantle plume and or tectono compositional effect of a rifted margin and a suture considerable stretching and or convective removal of pristine lithosphere in the southern block of southern granulite terrain and adjoining sri lanka before disappearing completely in the archaean northern block of southern granulite terrain and dharwar craton is suggested

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

comparison of laser grain size analysis with pipette and sieve analysis a solution for the underestimation of the clay fraction classically the grain size of soil and sediment samples is determined by the sieve method for the coarse fractions and by the pipette method based on the stokes sedimentation rates for the fine fractions results from the two methods are compared with results from laser diffraction size analysis which is based on the forward scattering of monochromatic coherent light from a point of view of laboratory efficiency the laser sizing technique is far superior accuracy and reproducibility are shown by measurements on certified materials it appears that laser grain size measurements of certified materials correspond very well with the certificated measurements tests were also done on a set of randomly selected sediments of fluvial aeolian and lacustrine origin except for the 2 m clay fraction there is a coarsening of the mean diameter of one to two size classes 0 25 caused by the non sphericity of the particles the platy form of the clay particles induces considerable differences eight size classes between pipette and laser measurements the 2 m grain size defined by the pipette method corresponds with a grain size of 8 m defined by the laser particle sizer for the studied sediments using a higher grain size level for the clay fraction when laser analysis is applied enables workers in the geological and environmental field to compare classical pipette analysis with a laser sizing technique

heat flux at the ice ocean interface the role of the oceanic heat flux fw in the sea ice energy and mass balance is discussed and a method is described for determining fw from measurements of the temperature and thickness of sea ice results obtained using this method and data collected in the fall of 1988 during a drift in the eastern arctic northeast of fram strait are presented estimates of fw ranged from 0 to 37 w m 2 and varied in both time and space the gradual variation over the course of the drift reflects transformation of the west spitsbergen current into arctic water masses a significant intersite variability on horizontal scales of 10 to 100 m is ascribed to the interaction between under ice topographic features and turbulent energy and mass transfer in the boundary layer in addition there is a variability in the ice growth rate on horizontal scales of 0 1 to 1 m which is ascribed to the instability of the ice ocean phase boundary in the presence of turbulent flow these observations have implications for modeling and future experiments

variability in terrigenous sedimentation processes off northwest africa and its relation to climate changes inferences from grain size distributions of a holocene marine sediment record variations in deposition of terrigenous fine sediments and their grain size distributions from a high resolution marine sediment record offshore northwest africa 30 51 0 n 10 16 1 w document climate changes on the african continent during the holocene end member grain size distributions of the terrigenous silt fraction which are related to fluvial and aeolian dust transport indicate millennial scale variability in the dominant transport processes at the investigation site off northwest africa as well as recurring periods of dry conditions in northwest africa during the holocene the terrigenous record from the subtropical north atlantic reflects generally humid conditions before the younger dryas during the early to mid holocene as well as after 1 3 kyr bp by contrast continental runoff was reduced and arid conditions were prevalent at the beginning of the younger dryas and during the mid and late holocene a comparison with high and low latitude holocene climate records reveals a strong link between northwest african climate and northern hemisphere atmospheric circulation throughout the holocene due to its proximal position close to an ephemeral river system draining the atlas mountains as well as the adjacent saharan desert this detailed marine sediment record which has a temporal resolution between 15 and 120 years is ideally suited to enhance our understanding of ocean continent atmosphere interactions in african climates and the hydrological cycle of northern africa after the last deglaciation

complexity of holocene climate as reconstructed from a greenland ice core glaciochemical time series developed from summit greenland indicate that the chemical composition of the atmosphere was dynamic during the holocene epoch concentrations of sea salt and terrestrial dusts increased in summit snow during the periods 0 to 600 2400 to 3100 5000 to 6100 7800 to 8800 and more than 11 300 years ago the most recent increase and also the most abrupt coincides with the little ice age these changes imply that either the north polar vortex expanded or the meridional air flow intensified during these periods and that temperatures in the mid to high northern latitudes were potentially the coldest since the younger dryas event

saharan dust on fuerteventura island canaries chemical and mineralogical characteristics air mass trajectories and probable sources from april 12 to 19 1984 dust was collected by cascade impactor on fuerteventura island 100 km from the saharan coast the samples were analyzed by x ray fluorescence spectrometry elemental composition by x ray diffraction mineral constituents and by scanning electron microscope sem and energy dispersive x ray analyzer edxa examination shape surface features and mineralogy of particles with the aim of determining the possible source areas of the dust on the scale of dust clouds another method allowed us to define the displacements of the dust using remote sensing meteosat ii national oceanic and atmospheric administration noaa and computing trajectories for any starting or ending point at any time these various methods gave complementary results and pointed out two successive episodes of dust with two different continental origins the first originated from a nearby source in the souss plain southern morocco and was characterized by very fine quartz particles the second drifted above more remote calcareous regions this study allows us to show how different methods can be used to characterize dust and to find the source areas the results suggest some general questions about the occurrence of coarse particles in the atmosphere and their role in the atmospheric deposition flux budget

米国南西部 コロラド川伸張地域 black山脈アコモデーション帯の背斜部分における中新世伸張と伸張しゅう曲運動 原標題は英語

centennial scale late pleistocene to mid holocene synthetic profile of the medjerda valley northern tunisia during the late pleistocene to mid holocene the medjerda river system in mediterranean tunisia shows events of increased flooding and aggradation of relatively coarse overbank deposits geomorphic activity in river systems within this region correlate with aridification of the climate but not with temperature the late pleistocene to mid holocene synthetic profile of the ghardimaou floodplain mid medjerda river indicates fluvial activity from 12 4 to 11 8 6 6 to 6 0 and after 4 8 ka cal bp external correlations imply global and regional causes of the late pleistocene to mid holocene climatic development such as north atlantic deep water formation fluctuations in saharan humidity and impacts of local mediterranean weather phenomena palaeomagnetic records offer additional opportunities to interpret fluvial activity in river systems especially for detecting chronological hiatuses in apparently homogeneous sediment sequences

magmatic and metamorphic imprints in 2 9 ga chromitites from the sittampundi layered complex tamil nadu india abstract the ca 2 9 ga old sittampundi layered complex slc of south india belongs to a special group of deformed and metamorphosed archaean rocks where chromitites are interlayered with anorthosite detailed field studies have revealed that the slc comprises of a sequence of magmatic rocks consisting of clinopyroxenite anorthosite and mafic rocks of tholeiitic composition minor bif banded iron formations intercalated with the mafic rocks are the only sedimentary rock within the slc chromitite occurs as continuous to discontinuous bands a few mm up to 6 m thick within clinopyroxenite and highly calcic anorthosite an 99 100 but never in the enclosing mafic rocks chromite occurs broadly in three textural types a cumulus grains in chromitite layers b disseminated grains in clinopyroxenite and anorthosite and c small grains included in clinopyroxene and plagioclase a suite of felsic magma intruded the slc at ca 2 51 ga subsequently the entire rock sequence underwent polyphase deformation and metamorphism at ca 2 50 2 45 ga granulite facies and at 0 72 0 50 ga amphibolite facies during the latter event extensive alteration of clinopyroxene to amphibole and chlorite of plagioclase to clinozoisite and of chromite to cr poor green spinel took place chromite compositions show large variations cr 26 60 mg 4 45 fe 3 2 24 depending upon textural type and nature of the associated phases the most conspicuous compositional variation took place when chromite was metasomatically replaced by green spinel cr 3 21 mg 45 61 during amphibolite facies metamorphism on a cr vs mg plot pristine magmatic compositions of chromite define an array that suggest increasing cr with concomitant decrease in mg presumably during magmatic fractionation highly calcic plagioclase in anorthosite and fe al rich chromite in chromitite in the slc are consistent with a hydrous parental magma of tholeiitic composition this hydrous magma was generated in an oceanic arc environment and crystallized close to the surface of the earth in terms of mineralogy and field relations chromitite bearing rocks of the slc show remarkable similarity with the archaean anorthosite hosted chromitite deposits in layered magmatic complexes at fiskenaesset greenland and messina south africa but contrasts sharply with the chromitite deposits of proterozoic and phanerozoic age a change in the style of arc magmatism appears to be the controlling factor for marked change in chromite compositions across the archaean proterozoic boundary

a mathematical model of the ocean boundary layer under drifting melting ice abstract a mathematical model of the ocean boundary layer under drifting melting ice is formulated verified and applied the model is based on the conservation equations for heat salt and momentum and uses turbulence models to achieve closure novel features of the model include a low reynolds number turbulence model for the viscous region and a discrete element approach to the parameterization of roughness basic verification studies using laboratory measurements include the budget of turbulent kinetic energy and the mean temperature profile all verification studies are focused on the viscous region good agreement with measurements is generally obtained the model is finally compared to field data obtained during mizex predicted melt rates are in good agreement with measurements an analysis of the fluxes of salt and heat within the boundary layer is also provided

modern and last glacial maximum eolian sedimentation patterns in the atlantic ocean interpreted from sediment iron oxide content eolian dust derived from the desert regions of north africa is blown far into the tropical atlantic ocean by persistent easterly and northeasterly winds in this paper we demonstrate that the iron oxides hematite and goethite are a worthwhile addition to proxy monitors of eolian sedimentation in the tropical atlantic iron oxides are identified by diffuse reflectance spectrophotometry a technique capable of identifying these minerals in concentrations as low as 0 01 by weight we analyze samples from both the modern and last glacial maximum lgm synoptic levels from 178 sample locations yielding a total of 356 samples distributed throughout the atlantic ocean to determine the relative contribution of the iron oxides we factor analyzed the modern and lgm levels as a single data set the iron oxide factor explains about 25 of the variance in the combined core top and lgm data set mapped factor scores for the lgm and modern ocean indicate high iron oxide values are present in just two regions one off eastern north america and the other off northwest africa in the region off eastern north america iron oxide occurs primarily during the lgm as the previously noted brick red lutite a unique sediment type derived from the erosion of permo carboniferous red beds in atlantic canada a larger lobe shaped area of iron oxide rich sediment is present off northwest africa in both the modern and lgm levels the modern iron oxide lobe is coincident with the distribution of eolian dust as determined by observations from ships satellites and analysis of air samples during the lgm iron oxides exhibit a similar distribution except the southern margin of the region shifts equatorward and iron oxide concentration increases

stratigraphy chronology and paleoenvironmental reconstruction of the quaternary sedimentary infilling of a volcanic tube in fuerteventura canary islands abstract la cueva del llano is a volcanic tube of pleistocene age on fuerteventura island in the canary islands part of it is infilled with sediments of external origin these deposits are exceptional in stratigraphic complexity and thickness compared with other known tube infillings and they comprise nine stratigraphic units deposited in five phases in phase i which has not been dated sedimentation of cinder from a nearby cone occurred phase ii began ca 16 830 900 14 c yr b p whereas phase iv dates to 9280 370 14 c yr b p the interpretation of sedimentary features shows that phases iii and v correspond to a dry climate similar to the present one whereas the climate was much wetter during phases ii and iv this paleoclimatic sequence agrees with those suggested by the study of deposits formed in other sedimentary environments not only in fuerteventura but on other islands of the canary group and the sud maroc region

the last 140 ka in the afro asian arid semi arid transitional zone abstract during the last ten years a great number of geological or other proxy records provided radiocarbon u th or tl dated information on the past climatic oscillations in the arid semi arid zones extending between the atlantic and the pacific comparisons and a synthetic view of these results can now be attempted for the last 140 ka and compared with global changes as registered in oceanic or ice cores and with palaeomonsson models for this purpose wide spatial and time scales have to be used on the whole arid humid alternations roughly fit global changes cold phases corresponding to an extension of the arid areas to the south warm phases corresponding to the shrinking of the same to the north the last interglacial is associated with an increase of precipitation throughout the area considered isotopic stage 4 brings no evidence whatsoever of humid conditions two wetter episodes are registrated during stage 3 a major rainfall decrease is everywhere associated with the last glacial maximum 21 15 ka in most regions the arid or semi arid zones extending several hundred kilometers southwards relative to the present day pattern the two abrupt deglaciation steps and the younger dryas are recorded in all of the most sensitive regions at the margins of the present day monsoonal range during the holocene the precipitation increases everywhere by 100 400 mn relative to the present day values the optimum being at 8 5 6 5 ka a climatic deterioration follows with an irregular pattern of dry wet episodes according to the different geographic conditions the humid phase terminates at 3 5 3 ka in the whole transitional zone the major southward shift of the monsoonal precipitation range since its optimum some 8000 years ago fits the astronomical neoglacial trend and may possibly be correlated with past stage 5d although its rapidity and spatial importance may just reflect one of the sharp successive cold warm variations registered by grip during the whole stage 5

a 300 kyr record of aridity and wind strength in southwestern africa inferences from grain size distributions of sediments on walvis ridge se atlantic abstract the terrigenous fraction of sediments recovered from walvis ridge se atlantic ocean reveals a history of southwestern african climate of the last 300 kyr end member modelling of a data set of grain size distributions n 428 results in three end members the two coarsest end members are interpreted as eolian dust the third end member as hemipelagic mud the ratio of the two eolian end members reflects the eolian grain size and is attributed to the intensity of the se trade winds trade winds were intensified during glacials compared to interglacials changes in the ratio of the two eolian end members over the hemipelagic one are interpreted as variations in southwestern african aridity late quaternary southwestern african climate was relatively arid during the interglacial stages and relatively humid during the glacial stages owing to meridional shifts in the atmospheric circulation system during glacials the polar front shifted equatorward resulting in a northward displacement of the zone of westerlies causing increased rainfall in southwestern africa the equatorward shift of the polar front is coupled with an increase of the meridional pressure gradient leading to enhanced atmospheric circulation and increased trade wind intensity

provenance of present day eolian dust collected off nw africa 1 atmospheric dust samples collected along a transect off the west african coast have been investigated for their physical grain size distribution mineralogical and chemical major elements composition on the basis of these data the samples were grouped into sets of samples that most likely originated from the same source area in addition shipboard collected atmospheric meteorological data modeled 4 day back trajectories for each sampling day and location and total ozone mapping spectrometer aerosol index data for the time period of dust collection february march 1998 were combined and used to reconstruct the sources of the groups of dust samples on the basis of these data we were able to determine the provenance of the various dust samples it appears that the bulk of the wind blown sediments that are deposited in the proximal equatorial atlantic ocean are transported in the lower level 900 hpa ne trade wind layer which is a very dominant feature north of the intertropical convergence zone itcz however south of the surface expression of the itcz down to 5 s where surface winds are southwesterly we still collected sediments that originated from the north and east carried there by the ne trade wind layer as well as by easterly winds from higher altitudes the fact that the size of the wind blown dust depends not only on the wind strength of the transporting agent but also on the distance to the source hampers a direct comparison of the dust s size distributions and measured wind strengths however a comparison between eolian dust and terrigenous sediments collected in three submarine sediment traps off the west coast of nw africa shows that knowledge of the composition of eolian dust is a prerequisite for the interpretation of paleorecords obtained from sediment cores in the equatorial atlantic

the maximum warmings of the pleistocene world climate recorded in the canary islands abstract evidence of the warmest pleistocene climatic changes is preserved in the eastern canary islands although the existence of raised fossiliferous marine deposits in northern gran canaria has been known since the 19th century their chronology and significance with regard to past sea levels and temperatures have remained uncertain here we show three marine transgressions recorded by raised marine deposits the highest 85 m above sea level masl and oldest marine deposit is interbedded in basaltic lava flows and has been dated using both palaeomagnetic and radiometric methods the age of these deposits located on the northwest coast of gran canaria near the town of agaete places the marine transgression in a first pleistocene interglacial into the plio pleistocene limit the marine deposit at an intermediate altitude 35 masl has been dated using the unspiked k ar method on a pillowed basaltic lava flow the age of these deposits in arucas places the transgression in the penultimate european mindel riss sense interglacial the deposits at 12 masl in las palmas are attributed to the last pleistocene interglacial on the basis of their fossil content which is similar to that of the matagorda deposits in lanzarote and matas blancas in fuerteventura radiometric dating of a lava flow overlying similar deposits at el cotillo in fuerteventura has been carried out the molluscan fauna associated with the deposits permits an estimation of the sea temperatures by reference to their present biogeographical distributions the plio pleistocene boundary coincides at agaete end of olduvai event with a high sea level between 1 8 and 1 75 ma oxygen isotopic stage ois 63 the dated marine deposits at arucas 0 42 ma place an interglacial in ois 11 3 and finally we confirm that in the canaries with only one high sea level with a senegalese fauna ois 5 5 they are not an outpost for the mediterranean tyrrhenian deposits with strombus oscillations

geoarchaeological and chronometrical evidence of early human occupation on lanzarote canary islands abstract two desert loess paleosol sequences in sediment traps were investigated using pedo stratigraphy sedimentology soil mineralogy and irsl dating so far we cannot recognise significant irsl age underestimates from the polymineral fine grain fraction of our samples we establish a first palaeoclimatic sequence spanning the past ca 200 ka which can be compared to data from other canary islands and surrounding areas including terrestrial and deep sea records more humid phases on lanzarote are apparently triggered by milankovich forcing but the climate remained semi arid to arid all over the past 200 ka the onset of human occupation of the island during a slightly moister period is bracketed between 5 and 10 ka based on the occurrence of archaeosediments containing bones of ovicaprid this is the first proof of much earlier occupation than witnessed so far from archaeological records the early subsidiary economy had a strong impact on soil stability and landscape shaping of the island

saharan dust transport and high latitude glacial climatic variability the alboran sea record millennial to submillennial marine oscillations that are linked with the north atlantic s heinrich events and dansgaard oeschger cycles have been reported recently from the alboran sea revealing a close ocean atmosphere coupling in the mediterranean region we present a high resolution record of lithogenic fraction variability along images core md 95 2043 from the alboran sea that we use to infer fluctuations of fluvial and eolian inputs to the core site during periods of rapid climate change between 28 000 and 48 000 cal yr b p comparison with geochemical and pollen records from the same core enables end member compositions to be determined and to document fluctuations of fluvial and eolian inputs on millennial and faster timescales our data document increases in northward saharan dust transports during periods of strengthened atmospheric circulation in high northern latitudes from this we derive two atmospheric scenarios which are linked with the intensity of meridional atmospheric pressure gradients in the north atlantic region

dating saharan dust deposits on lanzarote canary islands by luminescence dating techniques and their implication for palaeoclimate reconstruction of nw africa 1 lava flow dammed valleys vegas on lanzarote canary islands represent unique sediment traps filled with autochthonous volcanic material and allochthonous saharan dust these sediments and the intercalated palaeosoil sediments document past environmental change of the last glacial interglacial cycles both on lanzarote and in nw africa a reliable chronology must be established to use these sediment archives for palaeoclimate reconstructions owing to the lack of organic material and the limiting time range of the 14c dating method luminescence dating is the most promising method for these sediments however the fluvio eolian character of these sediments is a major problem for luminescence dating because these sediments are prone to insufficient resetting of the parent luminescence signal bleaching prior to sedimentation to check for the best age estimates we compare the bleaching behavior of 1 different grain sizes coarse versus fine grain quartz osl and 2 different minerals fine grain feldspar irsl versus fine grain quartz osl the results show that owing to its bleaching characteristics quartz is the preferable mineral for luminescence dating on the basis of the fine and coarse grain quartz osl age estimates a chronostratigraphy up to 100 ka could be established beyond this age limit for osl quartz the chronostratigraphy could be extended up to 180 ka by correlating the vega sediments with dated marine sediment archives

quaternary laminar calcretes with bee nests evidences of small scale climatic fluctuations eastern canary islands spain thick laminar calcrete profiles are common on the surface of the eastern canary islands of lanzarote and fuerteventura this paper reports the study of one profile from lanzarote macher profile and one from fuerteventura tef a profile these profiles are about 2 m thick the macher profile is developed on basaltic host rocks and consists of two main horizons a lower horizon in which white veins of laminated micrite penetrate cracks and an upper laminar horizon the tef a profile is cumulative and consists from base to top of massive laminar and massive and laminar brecciated horizons highlighted in the study of these profiles are the presence of ooids the complex structure of the laminar horizons and the occurrence of fossil bee nests celliforma ooids consist of a nucleus of clay micrite and etched grains coated with envelopes of micrite and clay mainly palygorskite organic films favoured both the precipitation of carbonate and the adhesion of clays when the ooids formed in the soil the laminar horizons consist of a centimetre scale alternation of massive micrite with varied amounts of ooids and detrital grains with laminated micrite this alternation indicates the small scale periods of sedimentation erosion and soil formation in the upper part of a relatively stable surface these small scale alternations may reflect climatic vegetation changes in which arid periods are represented by micrite with ooids while laminated micrite reflects a better developed vegetation of the wet periods celliforma occur as ovoid larval cells with more or less rounded bases and a flat top the cells are about 3 cm long and 1 5 cm in diameter their wall is about 5 mm thick and is commonly laminated celliforma is interpreted as fossil nests of solitary bees their presence in the laminar horizon is evidence for the existence of a vegetation cover containing angiosperms

imprints of archean to neoproterozoic crustal processes in the madurai block southern india madurai block the largest crustal block in the southern granulite terrane sgt of peninsular india preserves the imprints of multistage tectonic evolution here we present u pb and hf isotope data on zircons from a charnockite granite suite in the north western part of this block the oscillatory zoning and the lree to hree enriched patterns of the zircons with positive ce and negative eu anomalies suggest that the zircon cores are of magmatic origin with ages in the range of 2634 2435 ma implying neoarchean paleoproterozoic magmatism followed by subsequent metamorphism and protocontinent formation in the north western part of the madurai block a regional 550 500 ma metamorphic overprint is also preserved in the zircons coinciding with the final amalgamation of the gondwana supercontinent the hf isotopic data suggest that the granite and charnockite were derived from isotopically heterogeneous juvenile crustal domains and the charnockites show a significant contribution of mantle derived components therefore the hf isotopic data reflect mixing of crustal and mantle derived sources for the generation of neoarchean crust in the north western madurai block possibly in a suprasubduction zone setting during continent building processes c 2014 elsevier ltd all rights reserved

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