selective dissolution of magnetic iron oxides with the acid ammonium oxalate ferrous iron extraction technique ii natural loess and palaeosol samples summary chemical extraction techniques are being introduced into environmental magnetism studies to aid in the interpretation of magnetic climate proxies previous studies have shown that the acid ammonium oxalate ferrous iron aao fe 2 extraction technique can be used to selectively dissolve very fine grained magnetite and maghemite from synthetic samples here we present the results of a study of this extraction technique to serve as a tool for selective dissolution of pedogenic magnetic minerals from a loess palaeosol transect before and after extraction the samples were subjected to classic mineral magnetic methods measurement of low field susceptibility and hysteresis parameters as well as first order reversal curve analysis in addition acquisition curves of the isothermal remnant magnetization irm were fitted with logarithmic distributions these analyses showed the magnetic dominance of lowcoercivity magnetic minerals by subtracting the irm remaining after extraction from that before extraction the magnetic fraction that was dissolved could be characterized as well supplying extra information concerning the performance of the extraction technique the aao fe 2 method successfully dissolved the superparamagnetic and part of the singledomain material from the palaeosol samples in one extraction step repeating the extraction resulted in hardly any further changes to the magnetic content of the samples the magnetic characteristics of the loess samples remained stable throughout the extraction experiment the combination of the aao fe 2 extraction with mineral magnetic analysis has successfully identified the pedogenic contribution in our samples therefore variations in the lithogenic fraction potentially present in pedogenically enhanced intervals can be assessed improving the merit of mineral magnetic climate proxy parameters

potbellies wasp waists and superparamagnetism in magnetic hysteresis because the response of a magnetic substance to an applied field depends strongly on the physical properties of the material much can be learned by monitoring that response through what is known as a magnetic hysteresis loop the measurements are rapid and quickly becoming part of the standard set of tools supporting paleomagnetic research yet the interpretation of hysteresis loops is not simple it has become apparent that although classic single domain pseudo single domain and multidomain loops described in textbooks occur in natural samples loops are frequently distorted having constricted middles wasp waisted loops or spreading middles and slouching shoulders potbellies such complicated loops are often interpreted in oversimplified ways leading to erroneous conclusions the physics of the problem have been understood for nearly half a century yet numerical simulations appropriate to geological materials are almost unavailable in this paper we discuss results of numerical simulations using the simplest of systems the single domain superparamagnetic sd sp system examination of the synthetic hysteresis loops leads to the following observations 1 wasp waisting and potbellies can easily be generated from populations of sd and sp grains 2 wasp waisting requires an sp contribution that saturates quickly resulting in a steep initial slope and potbellies require low initial slopes the sp contribution approaching saturation at higher fields the approach to saturation is dependent on volume hence the cube of grain diameter therefore there is a very strong dependence of hysteresis loop shape on the assumed threshold size 3 we were unable to generate potbellies using an sp sd threshold size as large as 30 nm and wasp waists cannot be generated using a threshold size as small as 8 nm the occurrence of both potbellies and wasp waists in natural samples is consistent with a room temperature threshold size of some 15 nm 5 4 simulations using a threshold size of 15 20 nm with populations dominated by sp grain sizes that is with a small number of sd grains produce synthetic hysteresis loops consistent with measured hysteresis loops and transmission electron microscopic observations from submarine basaltic glass 5 simulations and measurements using two populations with distinct coercivity spectra can also generate wasp waisted loops a relatively straightforward analysis of the resulting loops can distinguish the latter case from wasp waisting resulting from sp sd behavior

the late pleistocene palaeoclimatic record of north atlantic deep sea sediments revealed by mineral magnetic measurements eight cores of north atlantic deep sea sediment are correlated using simple rapid and non destructive measurements of magnetic susceptibility and isothermal remanence this stratigraphy is demonstrably related to late pleistocene palaeoclimatic variations by comparison with the oxygen isotope and microfossil records of these cores fluctuations in the concentration dependent magnetic properties of the cores largely reflect their lithological composition consisting of climatically modulated cycles of marl glacial horizons and nannofossil chalk interglacial horizons high magnetic concentration characterises glacial horizons which correspond to periods when carbonate productivity was severely restricted and ice rafted detrital inputs were prolific coincident with the migration south of the north atlantic polar front to within 3 of latitude north of the coring site in contrast interglacial horizons are characterised by low magnetic concentration and high carbonate content of the sediment consequent on the retreat of the polar front and the re establishment of coccolith floras in its wake during these periods ratios formed between individual magnetic parameters are independent of magnetic concentration and are thus free of any climatic influences wrought by carbonate oscillations in this study however such ratios exhibit a definite response to palaeoclimatic variations attributable to differences in the composition and grain size of the magnetic mineral assemblage of glacial vis a vis interglacial horizons of the cores these differences in mineral magnetic composition are substantially confirmed by mossbauer effect studies of selected samples representing peak glacial and interglacial horizons of one core such glacial interglacial contrasts in the concentration mineralogy and grain size of the magnetic assemblage most probably result from variations in the source and flux density of detritral inputs induced by changes in climate x ray diffraction studies of the same core indicate that variations in the mineralogy of the detrital fraction of the sediment are consistent with those of the magnetic assemblage together these data point to the conclusion that a subsidiary low latitude possibly aeolian detrital flux supplements high latitude ice rafted input in glacial horizons of the cores the low latitude flux however is also identifiable in interglacial horizons independent evidence suggests that this low latitude aeolian flux may be derived from the sahel region of north africa and transported to the coring site by harmattan winds associated with saharan dust outbreaks

partly pedogenic origin of magnetic variations in chinese loess quaternary sequences of interbedded aeolian silts loess and buried soils palaeosols potentially provide one of the best terrestrial records of past climates1 5 magnetic susceptibility variations in loess and palaeosol sequences from china are strongly correlated with climate induced fluctuations of oxygen isotope ratios in deep sea sediments2 4 6 8 as an explanation of this correlation it has been suggested that the recorded variations in magnetic susceptibility depend primarily on the degree of dilution by non magnetic bulk loess constituents of a uniform magnetic assemblage derived from remote but unknown sources6 8 it has also been suggested that such a model involving changes in the accumulation rate of loess superimposed on a constant flux of magnetic particles provides a relative geological timescale through the control of loess deposition by astronomically modulated climate fluctuations7 here we report a preliminary test of this model using rock magnetic properties especially sensitive to variations in magnetic grain size our results show that palaeosols are characterized by much finer magnetic grain size assemblages than are the intervening loess units this suggests that a simple model based on constant magnetic influx and dilution by variable amounts of non magnetic loess is inadequate our magnetic measurements establish the close comparability of the fine grained magnetic minerals in the palaeosol samples to those in contemporary soils and thus point to a partially pedogenic origin for the magnetic mineral assemblages in the palaeosols

palaeoclimate records from ois 8 0 5 4 recorded in loess palaeosol sequences on the matmata plateau southern tunisia based on mineral magnetism and new luminescence dating mineral magnetic studies of loess palaeosol sequences on the matmata plateau southern tunisia coupled with a new chronology based on luminescence dating confirm the presence of at least four phases of pedogenesis during the period 100 250 ka inter site correlations between the reddened fersiallitic palaeosols confirms that despite modern gullying processes the records are regional and repeatable the palaeosol magnetic signal is controlled by the formation of secondary ferrimagnetic minerals which may be easily detected by magnetic susceptibility and frequency dependent susceptibility measurements comparison of the magnetic record with global proxy climate records shows a correlation with loess palaeosol sequences in china and the marine oxygen isotope oi record during stages 8 0 5 4 preliminary attempts to infer palaeoprecipitation levels from modern analogues of soil magnetism climate associations suggests that during the periods 100 120 ka and 200 ka precipitation was 400 mm a 1 compared with modern precipitation 150 mm a 1

intermediate magnetite formation during dehydration of goethite abstract the dehydration of goethite has been studied by low temperature induced magnetization ltim and x ray diffraction on well characterized acicular crystals fresh samples were heated in air to temperatures between 155 c and 610 c goethite and hematite were the magnetically dominant phases after all runs except 500 c and 610 c for which only hematite was found however partially dehydrated goethites after the 238 402 c runs had broad peaks or inflections in the ltim curves around 120 k suggesting the formation of an intermediate spinel phase these samples were next given a saturation remanence in a field of 2 t at 10 k and the remanence was measured continuously during zero field warming to 300 k there was a decrease in remanence at the verwey transition 120 k diagnostic of magnetite the possible formation of a small amount of magnetite is of serious concern in studies of goethite bearing sediments and rocks chemical remanent magnetization crm of this strongly magnetic spinel phase could significantly modify the direction as well as the intensity of the original goethite crm as well it would be a new source of paleomagnetic noise as far as primary remanence carried by other mineral phases is concerned

36cl in ground water of the mazowsze basin poland abstract groundwater samples from the oligocene aquifer of the mazowsze artesian basin have been analysed for 36cl using the eth psi ams facility results of measurements and their hydrogeological interpretation are presented

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

african dust observed over canary islands source regions identification and transport pattern for some summer situations bulk filtration samples of dust were collected on fuerteventura canary islands in july 1985 in order to investigate african dust transport over this region during summer air mass trajectories and elemental and mineralogical analyses allowed us to distinguish between oceanic and continental influences three african dust transport cases occured during this period geochemical and mineralogical tracers combined with air mass trajectories indicate that two different source regions of dust sahelian and moroccan ones are involved each of these exhibits specific si al and fe al ratios that can be considered as tracers of dust origin a meteorological study based on satellite imagery meteorological maps and air mass trajectories confirms the previous identification of the source region it is also possible to describe the meteorological situation controlling the atmospheric pathway of the dusts from the source regions up to the canary islands this study suggests that some source regions especially the sahelian one of dust affecting the canary islands during summer are rather different from the moroccan ones observed in a spring situation by coude gaussen et al 1987

reconstruction of past climate conditions over central europe from groundwater data abstract here we present a 30 000 years low resolution climate record reconstructed from groundwater data the investigated site is located in the bohemian cretaceous basin in the corridor between the scandinavian ice sheet and the alpine ice field noble gas temperatures ngt obtained from groundwater data preserved multicentennial temperature variability and indicated a cooling of at least 5 7 c during the last glacial maximum lgm this is further confirmed by the depleted 18 o and 2 h values at the lgm high excess air ne at the end of the pleistocene is possibly related to abrupt changes in recharge dynamics due to progression and retreat of ice covers and permafrost these results agree with the fact that during the lgm permafrost and small glaciers developed in the inner valleys of the giant mountains located in the watershed of the aquifers a temporal decrease of deuterium excess from the pre industrial holocene to present days is linked to an increase of the air temperatures and probably also to an increase of water pressure at the source region of precipitation over the past few hundred years

diagenetic sources of stable remanence in remagnetized paleozoic cratonic carbonates a rock magnetic study hysteresis measurements lowrie fuller tests cisowski tests and low temperature demagnetization experiments on samples of the knox dolomite trenton limestone and onondaga limestone indicate that the remanence in these remagnetized carbonate units resides principally in single domain magnetite in contrast to previous interpretations volumetrically however a significant fraction of the magnetite is coarser grained as previous scanning electron microscopic work on magnetic extracts has shown these conclusions are based mainly on the characteristic wasp waisted shape of the hysteresis loops and on the anomalously high ratios of remanent coercivity to bulk coercivity both of which clearly indicate a bimodal distribution of coercivities grain sizes the magnetization is controlled mainly by cubic magnetocrystalline anisotropy consistent with the spheroidal particles commonly observed in extracts hysteresis trends show that especially the finest particles lack shape anisotropy in view of these conclusions the two components of natural remanence in these rocks are interpreted as 1 a late paleozoic kiaman chemical remanence carried by single domain diagenetic magnetite and 2 a cenozoic thermoviscous overprint residing principally in coarser pseudosingle domain and multidomain magnetite also of late paleozoic diagenetic origin

origin and age of saline waters in busko spa southern poland determined by isotope noble gas and hydrochemical methods evidence of interglacial and pre quaternary warm climate recharges abstract in the busko and solec spas saline sulphide and sulphate waters are exploited at different depths the shallow water system in busko is related to an interglacial or interstadial period shown by the lack of tritium and 14 c and its 18 o and d values equal to that of modern water the noble gas temperatures ngt are somewhat lower than the present air temperatures but the 4 he and 40 ar ages of about 90 480 ka confirm a pleistocene recharge the 18 o and d values of the deep system are much heavier than those of local modern waters which may mean the recharge of a warm pre quaternary climate the 4 he 40 ar and 21 ne contents and the ngt values confirm the deep system to be recharged at the pre quaternary stages of the present hydrologic cycle i e after the sea transgression in the badenian high so 4 2 contents indicate that the cl and so 4 2 in both systems originated from simultaneous leaching of nacl and gypsum other components can be explained by cation exchange between water and badenian clay minerals in marls e g ca 2 for mg 2 and na for k and by the decay of marine organic matter supplying br i and b

a late quaternary magnetic record of tunisian loess and its climatic significance magnetic measurements for a 10 m loess palaeosol sequence from the matmata plateau in southern tunisia show significant down profile variations in concentrations of pedogenic ferrimagnetic minerals the sequence appears to correlate with regional and global records of climate change over the past 70 kyr there is strong evidence from comparisons of mineral magnetic properties in modern soils and palaeosols that the sequence holds a proxy record of winter precipitation

quaternary palaeoclimates in the eastern canary islands abstract in the eastern canary islands aeolian formations interbedded with palaeosols have been studies the sequences cover the last 40 ka as evidenced by one 14 c accelerator analysis and several classical radiocarbon dates as in the sahara at least two wet episodes characterize isotopic stage 3 a short pedogenesis corresponds to the first deglaciation step at 15 ka after a new aeolian episode the holocene wet phase begins at around 10 ka the aeolian sedimentation is of saharian dust in particular during the stage 3 dry episode s u th and osl dating are current

the magnetism of a glacial aeolianite sequence from lanzarote canary islands coupling between luvic calcisol formation and saharan dust trapping processes during wet deposition events off northwestern sahara summary in order to better document the climatic origin of pedogenized loess deposits west of sahara rock magnetic measurements were performed on a last glacial coastal sand sequence from la mala lm quarry lanzarote canary islands containing six interbedded loess palaeosol units hysteresis and susceptibility data point to a coarse grained magnetic enhancement in the coastal sand which contrasts with the superparamagnetic sp to pseudo single domain psd behaviour of the saharan loess and palaeosol high and low temperature experiments show that oxidized titanomagnetite contributions dominate in the sand while fine grained sp to psd iron oxidation products such as maghemite and goethite are evidenced in the saharan loess palaeosol units at room temperature the detrital psd multidomain titanomagnetite contribution of local origin is tentatively estimated from the ac field dependence of magnetic susceptibility surface oxidation of detrital spinel grains and authigenesis of fine grained iron oxides including sp goethite are proposed to explain the magnetic properties of the primarily fine saharan dust bearing material the dry local climate of the present day and late holocene means that loess deposits are not preserved the six pedogenized loess units however point to dust trapping under semi arid wetter conditions probably illustrating periods of reduced latitudinal temperature gradients and climate variability of the north atlantic climate respectively these findings suggest that both the canary palaeosol and its content of ultra fine iron oxide might be constrained by wet deposition and trapping of fine saharan dust

pleistocene climates in china dated by magnetic susceptibility the magnetic susceptibility of loess and interbedded soils in central china varies with the degree of pedogenesis and serves as a proxy measure of climate the concentration of magnetic minerals in the sediment is inversely proportional to sedimentation rates throughout the brunhes epoch susceptibility measurements combined with the reversal stratigraphy provide a time scale that is independent of astronomic chronology on this scale the susceptibility record closely parallels the oxygen isotope fluctuations in deep sea sediments suggesting a close interdependence of the chinese dust falls the volume of land based ice and global climate

magnetic hysteresis of pseudo single domain and multidomain magnetite below the verwey transition abstract hysteresis loops have been measured as a function of temperature between 10 k and room temperature for two size fractions of crushed magnetite 1 5 m pseudo single domain psd and 100 150 m multidomain md the material under study appears to be fairly close to stoichiometric magnetite with a verwey transition temperature of 115 k for the md sample and 118 k for the psd sample for both samples hysteresis properties below the verwey transition depend critically on whether or not the samples were cooled through the transition in the magnetic field for the psd sample an even more complex behavior has been observed temperature dependences of coercive force obtained after zero field cooling differ significantly for the demagnetized versus magnetized starting magnetic state

quantitative estimates of palaeoprecipitation at xifeng in the loess plateau of china abstract using10be recent studies heller et al 1993 beer et al 1993 have tried to reconstruct palaeoclimatic records by separating the secondary pedogenic and primary aeolian detrital contributions to the magnetic susceptibility of chinese loess here we use a technique which monitors the temperature dependence of magnetic remanence to estimate the magnetisation and relative contribution of the superparamagnetic sp single domain sd and multidomain md ferrimagnetic components in the xifeng loess section on the assumption that the sp ferrimagnetic component is dominantly of pedogenic origin the magnetisation of this component has also been determined for samples taken from the topmost palaeosol s0 at six sites over the loess plateau and directly correlated with present day precipitation at these sites this correlation is then used to estimate quantitatively palaeoprecipitation for the topmost 16 m of the xifeng section which covers about the last 140 000 years the data indicate a considerably reduced precipitation during the glacial loess forming periods and a significantly higher level of precipitation than today during the last interglacial period

climate related variations in the composition of the late glacial and early holocene sediments of lake perespilno eastern poland abstract this paper presents an array of analyses of the laminated sediments of lake perespilno eastern poland covering the period between older dryas and preboreal using the varve chronologies pollen and 14 c data the laminated sequence of lake perespilno has been synchronised with that of lake go ciaz the length of the allerod and younger dryas periods derived from lake perespilno sediments agrees well with the previous estimates according to our data the climate in the allerod was relatively mild with some increase of precipitation and humidity after ca 13 2 kyr cal bp the beginning of the younger dryas is marked by drastic changes in temperature as well as humidity thinning of forests facilitated input of allochtonous material to the lake it seems that the groundwater level as well as lake level dropped significantly and the period of lowest water table was prolonged for ca 300 years surprisingly the abrupt warming at the beginning of the holocene is only slightly reflected in the sediments changes in sediment composition at that time seem to be controlled more by the development of surrounding vegetation than by the climate itself

high resolution lacustrine record of the late glacial holocene transition in central europe abstract in this paper we present the high resolution record of proxy climatic data in central europe during the final stages of the last deglaciation derived from the annually laminated sediments of lake go ciaz central poland the isotopic palynological and other microfossil data confirm sudden changes of climate at the onset and termination of the younger dryas completed within 150 and 70 years respectively in close agreement with the previous estimates derived from the polar ice cores and marine sediments in the upper yd some amelioration of climate took place already about 600 years before the main yd preboreal transition counting of annual varves in the lake sediments allows a direct estimate of the duration of the younger sdryas in central europe it lasted approximately 1640 years substantially longer than suggested by previous estimates derived from laminated lake sediments and glacial varves but agreeing with the radiocarbon calibration data obtained for barbados corals the calendar ages of the boundaries of the yd 12 920 and 11 280 cal bp are tentatively set

low temperature magnetic properties of pelagic sediments ocean drilling program site 805c tracers of maghemitization and magnetic mineral reduction magnetic properties of pelagic sediments from the western equatorial pacific ocean drilling program odp site 805c have been measured at low temperatures to investigate changes in magnetic mineralogy and the distribution of bacterial magnetite with depth a saturation isothermal remanent magnetization mrs was given to the samples by applying a strong magnetic field 2 5 t at 20 k after cooling both in the absence zero field cooling zfc and presence of a 2 5 t magnetic field field cooling fc the thermal demagnetization of both mrszfc and mrsfc was measured from 20 to 300 k no pronounced verwey transition was observed in the data from samples shallower than the iron redox boundary below the boundary the verwey transition is visible for all samples studied we interpret this behavior as reflecting low temperature oxidation maghemitization of primary magnetite and the subsequent dissolution of maghemite coatings below the iron redox boundary the low temperature oxidation may occur both at the water sediment interface and deeper in the suboxic zone of sediments as a result of bacteria mediated processes including the reduction of nitrate compounds mrszfc and mrsfc thermal demagnetization curves of all samples diverge for the entire temperature range measured the divergence may be caused by the low temperature stabilization of spontaneous magnetization vectors along with exchange interaction in the magnetite maghemite system together maghemitization and magnetic reduction diagenesis appear to play a dominant role in controlling the low temperature properties of the sediment studied as a result low temperature magnetic studies may provide more information on differences in reduction diagenesis than on the distribution of bacterial magnetite in natural sediments the changes in effective oxidation state below the iron redox boundary detected by low temperature methods may be useful in the study of some paleoenvironmental processes

origine eolienne de certains encroutements calcaires sur l ile de fuerteventura canaries orientales abstract on fuerteventura island eastern canaries extensive and diversified calcrete horizons overlie various volcanic rocks which at most include 10 to 12 cac0 3 many data drawn from their geomorphological situation in the field or from analyses in the laboratory show that only a small part of the carbonates have come from the underlying rocks the greater part has been brought in by wind transport after deposition the carbonates have been concentrated by soil forming processes downward migration of carbonate components or calcareous epigenesis when the ocean level was lower than today during the glacial times bioclastic sands were moved inland from the shoreline by the effects of both westerly gales and an arid climate mineralogical isotopical and field data show a good relationship between these eolian sands and the calcretes present on slopes until the tardiglacial period carbonate particles were transported close to the ground or carried in suspension in the air from these old shorelines during holocene time another eolian source supplied calcretes with carbonates at that time the sea level was indeed high but eastern or northeastern winds brought abundant dust from the sahara the methods used in the study of carbonates on fuerteventura island could be applied to study the eolian origin of some carbonates included in other calcretes of north africa or the near east

origins of peri saharan dust deposits traced by their nd and sr isotopic composition abstract isotopic ratios of sr and nd can be used as very precise tracers in conjunction with mineralogical geochemical tracers and climatic models to identify the origins of dust deposit and to quantify their fluxes both today and throughout the last climati cycles this technique is useful for constraining aeolian transport and atmospheric circulation trajectories from desert sources and over the oceans the present work concerns dust deposits surrounding the saharan desert on the canary islands the african fraction of the dust deposits displays isotopic values which are typical of moroccan origin on the other hand tunisian loesses have been derived from the northern part of the sahara in this case tracers are sensitive enough to distinguish between center saharan shield origin and peri saharan secondary sources allowing us to distinguish between transport due to the trade winds vs the harmattan or mediterranean wind regimes

high absolute paleointensity during a mid miocene excursion of the earth s magnetic field abstract a record of an excursion of the earth s magnetic field was found in a 14 3 myr old lava sequence of the shield basalts from gran canaria canary islands the thermal and alternating field demagnetization of the samples from 14 subsequent lava flows revealed mainly single component magnetizations and sometimes minor viscous overprints four consecutive flows showed intermediate paleodirections which represent an excursion of the virtual geomagnetic pole vgp from the south pole towards the equator in the central atlantic rock magnetic and microscopic analysis revealed high temperature oxidized titanomagnetites as the dominant carrier of remanence on the basis of reversibility of thermomagnetic curves and limited variation of susceptibility during thermal demagnetization we selected suitable samples for three slightly different thellier type paleointensity methods the results show a minimum in paleointensity after the directional excursion with intensity values of 9 t with the pole approaching the equator values of 27 t are reached the intensity at the beginning and at the end of the section is 20 t corresponding to a virtual dipole moment vdm of 6 1022 am2 the high intensities during the vgp excursion with a pole near the equator are explained by the same vdm

holocene climate change and its influence on early agriculture in the nile delta egypt abstract to investigate how holocene climate patterns influenced the development of early egyptian agriculture at the archaeological site of sais on the nile delta we conducted a palynological study seven palynological zones were defined to reveal holocene climate fluctuations zone i ca 9000 7000 cal yr bp was a period of warming climate succeeded by a progressive drying climate phase in zones ii vii ca 7000 2000 cal yr bp pollen records indicate nile flooding prevailed before 7000 years ago making the study area uninhabitable before it later developed into a wetland setting the earliest farming started at ca 6700 cal yr bp as indicated by the abrupt appearance of cereal poaceae 35 m during a time of climate warming zone iii this material can be differentiated from wild poaceae

identification of groundwater chemistry origins in a regional aquifer system wielkopolska region poland this paper describes the origin of the groundwater chemistry in the regional aquifer located in the wielkopolska region of western poland factor analysis was used for the identification of geochemical processes that influence the groundwater chemistry two groups of processes were identified anthropogenic i e caused by groundwater contamination and geogenic i e caused by natural geochemical processes based on a background of the natural variations in the groundwater chemistry the effect of upward groundwater flow from the deep part of the flow system on the groundwater chemistry was identified the boron concentrations and isotope data allowed for the identification of zones of relatively old groundwater the spatial distribution of fluoride concentrations allowed for the identification of recharge zones this study demonstrates the general usefulness of groundwater chemistry differentiation for supporting identification of groundwater flow patterns it also demonstrates the importance of using chemical data to evaluate the connectivity between different aquifers these interpretations can be used for better management of water resources on a regional scale

low temperature magnetic behavior of titanomagnetites titanium substitution has a significant effect on the temperature dependence 5 300 k of low temperature saturation remanence and of initial susceptibility in synthetic and natural titanomagnetite fe3 xtixo4 0 x 0 4 and electronic and lattice relaxation phenomena over the entire titanomagnetite compositional range these features produce diagnostic magnetic behavior useful for titanomagnetite identification in natural samples moreover the apparent similarities between the thermal decay of low temperature remanence of titanomagnetite with pyrrhotite pure magnetite and superparamagnetic phases can lead to complications in interpreting low temperature remanence data when titanomagnetite is present

paleoceanographic reconstructions from planktonic foraminifera off the iberian margin temperature salinity and heinrich events a quantitative analysis of planktonic foraminifera in a core from the iberian margin allows a reconstruction of the evolution of oceanographic parameters during the last glacial cycle with a resolution of 1000 years a principal component analysis performed on 19 species allows the identification of 11 intervals characterized by increased abundances of the subpolar species the youngest six of these intervals are correlated with the last 6 heinrich events hes the five cold events older than stage 4 are dated at 81 90 110 129 and 140 ka respectively paleotemperatures reconstructed using the modern analog technique indicate 4 c decreases during all even numbered isotopic stages and stage 3 during the hes temperature decreases reach 10 c and seawater 18o anomalies reach 1 temperature and salinity reconstructions indicate that the environment of the iberian margin has been under the combined influence of global factors such as the migration of the polar front and iceberg discharge and of regional factors such as the precipitation evaporation regime on both oceanic and continental area

holocene saharan dust deposition on the cape verde islands sedimentological and nd sr isotopic evidence holocene aeolian silts deposited on the cape verde islands provide information about the origin of african palaeodusts that have fallen on the north eastern atlantic ocean over the last 10 000 years sedimentological composition indicates that most of these aeolian silts are unquestionably of continental origin their sr and nd isotopic composition identifies a saharan origin suggesting transport by harmattan winds we estimate that saharan dust comprises 75 95 of material in these holocene silts the rest coming from the weathering of local basaltic bedrock

field dependence of ac susceptibility in titanomagnetites abstract ac susceptibility measurements as a function of field amplitude hac and of frequency show a strong field dependence for a set of synthetic titanomagnetites fe3 xtixo4 and for certain basalts from the soh 1 hawaiian drill hole and from iceland in phase susceptibility is constant below fields of about 10 100 a m and then increases by as much as a factor of two as hac is increased to 2000 a m both the initial field independent susceptibilities and the field dependence of susceptibility are systematically related to composition initial susceptibility is 3 si for a single crystal sphere of tm0 x 0 and decreases with increasing titanium content field dependence is nearly zero for tm0 and increases systematically to a maximum near tm60 x 0 6 this field dependence can in some cases be mistaken for frequency dependence and lead to incorrect interpretations of magnetic grain size and composition when titanomagnetite is present

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

radioelements radiogenic helium and age relationships for groundwaters from the granites at stripa sweden abstract the solution of radioelements and radiogenic 4he by groundwaters in fractured rocks is dependent upon the radioelement distribution in the rock matrix and the extent of the rock water interface the 234 u 238 u activity ratio and the dissolved u rn and he contents of such groundwaters respond to changes in the flow regime with time although 234 u 238 u activity ratios change with groundwater residence time as a consequence of 234th recoil induced solution of 234u the activity ratio is strongly influenced by the u distribution within fractures by the extent of the rock water interface and by the amount of 238u in solution a model for the quantitative evaluation of these effects is presented groundwaters from depths up to 880 m in the stripa granite have variable dissolved uranium contents and 234 u 238 u activity ratios the uranium geochemistry is primarily determined by variations in flow path rather than by groundwater age dissolved radiogenic 4he in the groundwaters increases with their depth of origin and is dependent upon the u content of the granite and upon its fracture porosity it increases with groundwater residence time but movement of 4he by diffusion and transport processes make the actual groundwater age indeterminate

single domain and superparamagnetic titanomagnetite with variable ti content in young ocean floor basalts no evidence for rapid alteration high resolution electron microscope studies have been carried out on zero age new flow basalts from the juan de fuca ridge and on young 20 ka basalts from the axis of the east pacific rise at 12 n such data lead to characterization of the magnetic minerals especially those of smaller grain size which have been hypothesized by kent and gee to have undergone grain size dependent alteration in addition to larger titanomagnetite grains abundant submicrometer titanomagnetite has been observed in globules within a glassy matrix these grains likely to be single domain sd or superparamagnetic are associated with apatite uncommon pyrrhotite and residual glass the submicrometer titanomagnetite grains have a wide compositional range 0 x 0 8 where x is the fraction of ulvospinel component whereas the larger multi domain md sized titanomagnetite grains have a narrow composition range of approximately x 0 6 this variability in ti content provides a ready explanation for the thermal rock magnetic properties observed by kent and gee and eliminates the need to invoke extremely rapid 20 ka alteration of these young basalts

combined marine proxy and pollen analyses reveal rapid iberian vegetation response to north atlantic millennial scale climate oscillations abstract a deep sea sediment core from the western portuguese margin has provided a continuous high resolution record of millennial scale climatic oscillations during the interval 9000 65 000 yr b p pollen analysis of the same sequence allows direct in situ assessment of the phase relationship between the north atlantic climate system and vegetation changes on the adjacent landmass this demonstrates for the first time that variability in nw iberian tree population size closely tracked millennial scale climate variability

pedogenesis and paleoclimate interpretation of the magnetic susceptibility record of chinese loess paleosol sequences in the chinese loess paleosol sequences from luochuan haanxi province china variations in the magnetic susceptibility have been accepted as an excellent proxy for paleoclimate and the standard interpretation is that climatic processes have enhanced the magnetic susceptibility of the paleosols beyond the base line level of the loess by using mineral magnetic properties and a soil chemistry extraction procedure we show that most of the magnetic susceptibility signal in both the paleosols and the loess is due to pedogenesis in effect loess deposition and pedogenesis are competing processes at all times and the presence of a paleosol simply indicates that the latter process was predominant these results imply that any interpretation of the paleoclimate record of loess paleosol sequences must recognize the pedogenic nature of the magnetic susceptibility signal and that the focus of future research must be on the critical role of climate in the development of the paleosols

establishing constraints on groundwater ages with 36cl 14c 3h and noble gases a case study in the eastern paris basin france abstract groundwaters from the tithonian kimmeridgian oxfordian and upper dogger aquifers within the eastern part of the paris basin france were characterised using 3 h 14 c and 36 cl and noble gases tracers to evaluate their residence times and determine their recharge period this information is an important prerequisite to evaluating the confinement properties of the callovo oxfordian clay formation sandwiched between the oxfordian aquifer and the dogger aquifer currently being investigated by the french nuclear waste management agency andra for radioactive waste disposal data presented in this paper are used to test 4 hypotheses 1 the oxfordian limestone is isolated from the overlying tithonian kimmeridgian surface aquifer this first hypothesis is supported by the presence of measurable 3 h activities in groundwaters from the surface aquifer 6 11 tu and by its absence in groundwaters derived from deeper aquifers 2 the callovo oxfordian clay sequence in the vicinity of the url serves as an effective barrier to advective flow and transport between the underlying upper dogger aquifer and the overlying oxfordian limestone aquifer this second hypothesis is supported by relatively low concentrations of cl 3 5 78 mg l 1 na 15 145 mg l 1 br 0 08 0 4 mg l 1 and 4 he rad 0 2 2 3 ccstp g 1 and slightly higher 36 cl cl ratios 2 7 59 10 15 at at 1 in groundwaters from the oxfordian aquifer compared to those from the upper dogger aquifer 345 4027 mgcl l 1 402 2390 mgna l 1 1 8 22 2 mgbr l 1 1 6 37 2 ccstp he g 1 1 5 10 15 at 36 cl at 1 cl 3 groundwaters from the oxfordian aquifer in the vicinity of url are pre holocene with residence times exceeding 10 ka geochemical and isotopic lines of evidence for this hypothesis include a 13 c values measured on oxfordian aquifer waters that are close to 13 c of the aquifer matrix reflecting strong isotopic exchange over several thousand years b noble gas temperatures that indicate recharge temperatures between 3 and 8 6 c lower by 2 7 c than the modern average temperature in this area c radiogenic 4 he concentrations between 0 16 10 5 and 2 3 10 5 ccstp g 1 of water about 2 3 orders of magnitude greater than the 4 he concentration of air equilibrated water 4 groundwater residence time for the upper dogger aquifer in the vicinity of the url probably exceed several hundred thousand years such long residence times are indicated by the accumulation of radiogenic he up to 37 10 5 ccstp g 1 assuming a closed system primary contributors to uncertainties in interpretation of the data presented in this paper are the lack of well defined 36 cl cl input ratio knowledge about the 4 he rad sources for oxfordian and dogger aquifers knowledge about transport processes occurring through the dogger aquifer and the extensive dilution of initial 14 c activities by dissolution exchange with aquifer matrix overall however although the data presented in this paper remain semi quantitative due to inevitable intrinsic limitations of the methods none contradict the hypotheses of long residence times and aquifer isolation in the vicinity of the url

isothermal remanence experiments at room and at liquid nitrogen temperature application to soil studies a simple magnetic mineral identification technique is proposed which measures isothermal remanent magnetisation irm acquired in different field strengths at 293 k and 77 k magnetic parameters are introduced that use these irms in order to distinguish concentration and type of ferromagnetic minerals in different magnetic states the method determines easily contributions of superparamagnetic ferrimagnetic minerals in environmental magnetism studies in addition high coercivity goethite and possibly superparamagnetic hematite are identified the analysis of the magnetic properties of a soil profile on a late pleistocene terrace from the jarama river in central spain is given as an example

dating of glacial palaeogroundwater in the ordovician cambrian aquifer system northern baltic artesian basin abstract the ordovician cambrian aquifer system in the northern baltic artesian basin contains glacial palaeogroundwater that originates from the scandinavian ice sheet that covered the study area in the pleistocene previously no absolute dating of this palaeogroundwater has been attempted in this multi tracer study we use 3h 14c 4he and stable isotopes of water to constrain the age distribution of groundwater we apply the geochemical modelling approach developed by van der kemp et al 2000 and blaser et al 2010 to calculate the theoretical composition of recharge waters in three hypothetical conditions modern glacial and interstadial for 14c model age calculations in the second phase of the geochemical modelling the calculated recharge water compositions are used to calculate the 14c model ages using a series of inverse models developed with netpath the calculated 14c model ages show that the groundwater in the aquifer system originates from three different climatic periods 1 the post glacial period 2 the late glacial maximum lgm and 3 the pre lgm period a larger pre lgm component seems to be present in the southern and north eastern parts of the aquifer system where the radiogenic 4he concentrations are higher from 3 0 10 5 to 5 5 10 4 cc g 1 and the stable isotopic composition of water is heavier 18o from 13 5 to 17 3 glacial palaeogroundwater from the north western part of the aquifer system is younger and has 14c model ages that coincide with the end of the lgm period it is also characterized by lower radiogenic 4he concentrations 2 0 10 5 cc g 1 and lighter stable isotopic composition 18o from 17 7 to 22 4 relations between radiogenic 4he and 14c model ages and between radiogenic 4he and cl concentration show that groundwater in the aquifer system does not have a single well defined age rather the groundwater age distribution has been influenced by mixing between waters originating from end members with strongly differing ages overall the results suggest that in the shallower northern part of the aquifer system significant changes in groundwater composition can be brought about by glacial meltwater intrusion during a single glaciation however multiple cycles of glacial advance and retreat are needed to transport glacial meltwater to the deeper parts of the aquifer system

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

mineral magnetic record of the chinese loess and paleosols variations in the magnetic susceptiblity of the chinese loess and its interbedded paleosols correlate strikingly well with the deep sea oxygen isotope record low susceptibility values are found for the loess layers and high values are found for the soil horizons two interpretative models have been advanced to account for these magnetic variations both of these models discount any significant in situ formation of magnetite during soil forming periods instead they infer relative concentration of detrital or atmospheric magnetite at these times we critically examine the assumptions made in these models and on the basis of some new mineral magnetic data and fromalized magnetic flux calculations offer an alternative explanation of the loess magnetic record our model identifies pedogenic formation of magnetite as the major contributor to the high magnetic susceptibility of the paleosols the formation and preservation of this pedogenic magnetite is dependent on soil froming conditions and hence reflects the regional climate

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

rock magnetism of late neogene and pleistocene deep sea sediments relationship to sediment source diagenetic processes and sediment lithology we use bivariate scatter plots to illustrate variations in selected rock magnetic properties low field susceptibility anhysteretic and isothermal remanence of late neogene and pleistocene deep sea sediments from 16 sites in the arctic ocean north atlantic equatorial atlantic and north pacific ocean and the arabian sea our intention is to examine the ability of the rock magnetic properties to differentiate the sediments according to factors such as lithology geographical area and the dominant mode of terrigenous sedimentation which at these sites is via ice rafting via bottom currents or via eolian processes overall correlations between sediment magnetic properties and gross lithology is poor and factors such as the source and transport path of terrigenous sediment and detrital magnetic minerals together with the action of reductive diagenetic processes are the major controls on the magnetic properties on the bivariate scatter plots sites with major ice rafted contributions tend to have high sedimentary ferrimagnetic mineral concentrations relatively coarse ferrimagnetic grain sizes and scattered sample point distributions in contrast sites where we infer significant bottom current supply of terrigenous material have tightly grouped sample point distributions carbonate sediments in which the terrigenous component is supplied by eolian processes tend to have a broad range of magnetic mineral concentration caused by glacial interglacial fluctuations in carbonate accumulation and eolian activity sediments containing significant volcanogenic material have high concentrations of relatively coarse grained ferrimagnetic material reductive diagenesis is a significant determinant of sediment magnetic properties in high productivity areas and has the effect of preferentially removing the fine grained ferrimagnetic fraction causing a coarsening of the ferrimagnetic grain size distribution and a rise in the antiferromagnetic ferrimagnetic ratio

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

field and temperature behavior of remanence in synthetic goethite paleomagnetic implications synthetic powders of pure goethite exhibit an antiferromagnetic behavior and negligible isothermal remanent magnetization up to 4 tesla however thermoremanence up to 0 3 am kg 1 can be imparted to the samples high field measurements show median acquisition field of 9 13 t and suggest saturation fields of the order of 10 t large increase in remanence at low temperature is an intrinsic feature of goethite the weak ferromagnetism observed is linked to a bulk origin for spin imbalance rather than to an effect of very fine grain size or surface defects the results are compared with properties of rocks bearing goethite and hematite

evidence for massive discharges of icebergs into the north atlantic ocean during the last glacial period sediments in the north atlantic ocean contain a series of layers that are rich in ice rafted debris and unusually poor in foraminifera1 here we present evidence that the most recent six of these heinrich layers deposited between 14 000 and 70 000 years ago record marked decreases in sea surface temperature and salinity decreases in the flux of planktonic foraminifera to the sediments and short lived massive discharges of icebergs originating in eastern canada the path of the icebergs clearly marked by the presence of ice rafted detrital carbonate can be traced for more than 3 000 km a remarkable distance attesting to extreme cooling of surface waters and enormous amounts of drifting ice the cause of these extreme events is puzzling they may reflect repeated rapid advances of the laurentide ice sheet perhaps associated with reductions in air temperatures yet temperature records from greenland ice cores appear to exhibit only a weak corresponding signal moreover the 5 10 000 yr intervals between the events are inconsistent with milankovitch orbital periodicities raising the question of what the ultimate cause of the postulated cooling may have been

paleointensity variations across the last geomagnetic reversal at la palma canary islands spain a detailed volcanic record of absolute paleointensity has been obtained for the period encompassing the last geomagnetic reversal from a succession of 69 distinct lava flows in two adjacent sections on the island of la palma the correlation between the two sections relies on the positions of the brunhes matuyama boundary and on the flow chronology obtained by a refined potassium argon k ar dating technique several pretransitional flows exhibit very shallow paleomagetic inclinations but they cannot be considered as really transitional paleointensity experiments conducted on 288 specimens provided 168 successful determinations 14 were obtained after correction for 50 lava flows that were considered to represent 45 distinct units the evolution of the paleofield intensity can be constructed by assuming uniform extrusion rates between three dated lava flows the period preceding the transition is characterized by large fluctuations with typical peak to peak amplitudes between 20 and 40 t which decrease down to 7 t prior to the transition the 100 kyr long interval following the reversal is associated with field intensities as high as 60 t and depict a strong and rapid restoration of the dipole field the virtual dipole moments vdms have been compared with sedimentary vdms generated from the record of relative paleointensity from ocean drilling program site 851 to which have been added non dipole components similar to the present geomagnetic field a reasonable fit can be made between the two curves which implies variations in the eruption rates but not incompatible with the uncertainties in the k ar age determinations thus these results can support but do not fully demonstrate the existence of asymmerical saw toothed variations in field intensity

age and recharge pattern of water in the oligocene of the mazovian basin poland as indicated by environmental tracers abstract controversies exist about the recharge pattern age and renewal rate of water in the oligocene sands of the mazovian basin poland hydrodynamic modelling yields ages of about 1 5 ka whereas earlier estimates based on environmental tracer methods suggested from 30 ka to more than 200 ka this age discrepancy mainly resulted from apparent inconsistency of environmental isotope data and partly from unidentified flow paths sparse data and poor knowledge about the hydrodynamic parameters of the overlying pliocene sediments however in spite of 18 o and d values only slightly lighter than those typical for local holocene waters low inferred noble gas temperatures obtained within this study 0 3 4 9 c in comparison with the present air temperature of 7 5 c and low 14 c contents 0 7 pmc indicate a dominant role of glacial recharge the isotope shifts to heavier values and to the right of w m w l which decrease the difference between the holocene and glacial waters are caused by evaporation prior to recharge via numerous paleolakes and by admixture of ascending saline water though several earlier 36 cl analyses suggest ages of the order of 200 ka such great ages are excluded by 40 ar 36 ar ratios close to the atmospheric equilibrium and relatively low 4 he excess values obtained within the present study a good correlation of 4 he excess with cl content indicates its origin to be related mainly to local ascension of older waters and to be little depended on the radiogenic production within the aquifer or to the accumulation of crustal flux along the flow paths therefore the noble gas data have appeared to be indispensable for the identification of the glacial age of water far from erosion windows in spite of weak 18 o and d climatic signal and for confirmation of a conceptual model invoking significant vertical recharge by leakage through pliocene sediments

european climatic response to millennial scale changes in the atmosphere ocean system during the last glacial period abstract pollen foraminifer dinocyst and coarse lithic high resolution analyses and 18 o measurements have been carried out for the last glacial section of marine core md95 2042 located near the southwestern margin of the iberian peninsula the pollen data indicate a high frequency of vegetational changes on the adjacent continent during this period suggesting a climatic variability very similar to that of the dansgaard oeschger cycles recorded by the greenland ice cores the detailed direct correlation of the terrestrial and marine proxy data from core md95 2042 indicates a three phase pattern of heinrich events in land and ocean environments the first and last phases of the h5 and h4 events are characterized by a mild and humid climate in southwestern europe probably associated with the european origin of the ice rafted detritus the middle phase exhibits a cold and dry climate in iberia linked with the maximum input of ice rafted detritus this phase seems to correspond with the laurentide ice sheet surges between the heinrich events several cold and dry periods on land are correlated with stades of the dansgaard oeschger cycles the impact of the dansgaard oeschger stades in southwestern europe seems to be preferentially connected to the cold winter air masses reaching this mid latitude region

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