rock albedo and monitoring of thermal conditions in respect of weathering some expected and some unexpected results broadly speaking there is at least within geomorphic circles a general acceptance that rocks with low albedos will warm both faster and to higher temperatures than rocks with high albedos reflectivity influencing radiative warming upon this foundation are built notions of weathering in respect of the resulting thermal differences both at the grain scale and at the scale of rock masses here a series of paving bricks painted in 20 per cent reflectivity intervals from black through to white were used to monitor albedo influenced temperatures at a site in northern canada in an attempt to test this premise temperatures were collected for five months for the rock surface and the base of the rock the blocks being set within a mass of local sediment resulting thermal data did indeed show that the dark bricks were warmer than the white but only when their temperatures were equal to or cooler than the air temperature as brick temperature exceeded that of the air so the dark and light bricks moved to parity indeed the white bricks frequently became warmer than the dark it is argued that this negating of the albedo influence on heating is a result of the necessity of the bricks both white and black to convect heat away to the surrounding cooler air the darker brick being hotter initially convects faster than the white as a product of the temperature difference between the two media thus where the bricks become significantly hotter than the air they lose energy to that air and so their respective temperatures become closer the albedo influence being superceded by the requirement to equilibrate with the surrounding air it is argued that this finding will have importance to our understanding of weathering in general and to our perceptions of weathering differences between different lithologies copyright 2005 john wiley sons ltd

salt weathering simulations under hot desert conditions agents of enlightenment or perpetuators of preconceptions because of access difficulties and inhospitable environmental conditions our understanding of rock weathering in hot deserts has been strongly influenced by laboratory simulations however a risk exists that results may come to owe more to experimental design than to actual environmental conditions experienced at the atmosphere rock surface interface this was especially true in early salt weathering simulations that seemingly sought to reinforce the orthodoxy of a physically dominated weathering environment driven by extremely high absolute temperatures and large diurnal temperature ranges however improvements in environmental sensors over the last 20 years have established the complexity of desert climates and the importance of microclimatic controls and allowed considerable refinement of experimental design this overview evaluates the implications of recent simulation studies and presents new information on possible fatigue effects of differential thermal expansion of salts and the salt weathering of test blocks under compressive loading in doing so it demonstrates how physical rock properties change during experimentation the importance of short term surface temperature fluctuations distinctions between the weathering of unconfined debris and larger rock surfaces the importance of moisture and salt applications that replicate their availability in deserts the importance of rock thermal properties in controlling their weathering response in environments dominated by radiative heating and cooling and the overall complexity of weathering regimes

effects of direct and indirect heating on the validity of rock weathering simulation studies and durability tests rock surface and subsurface temperature responses in samples exposed to direct heating insolation under natural hot desert conditions reveal considerable variability between lithologies related to differences in thermal properties especially albedo and thermal conductivity however when the same samples are heated indirectly by air in an oven based environmental cabinet lithological differences in temperature response disappear and all samples attain temperatures similar to the air temperature within the cabinet rates and patterns of rock decay produced in such environmental cabinets may not therefore reflect those encountered under natural conditions where breakdown is related to micro environmental conditions at the rock air interface and where rock temperature is one of the most important controlling factors in addition to implications for assessment of weathering effectiveness use of only indirect forms of heating affects the determination of comparative rock durability because all rock types are cycled through the same temperature regimes because temperature exerts such a major control on rock breakdown through its control on physical and chemical weathering processes all significant factors influencing it must be included in the design of weathering simulations and durability tests

daytime rock surface temperature variability and its implications for mechanical rock weathering tenerife canary islands summary summer and winter rock surface temperature measurements are presented from three sites along an altitudinal gradient significant between and within site variability is recognised related to insolation cloud cover and air temperature differences maritime influences and time of year the variability argues against the use of a single rock temperature regime to characterise hot desertic environments in for example weathering simulation studies superimposed upon diurnal patterns of heating and cooling are numerous short 3 15 minutes and medium term 1 2 hours fluctuations related to wind speed and cloud cover variations rates of surface temperature change are very high during these fluctuations 3 c minute and it is proposed that they may enhance the operation of a number of mechanical rock weathering mechanisms

laboratory simulation of the wick effect in salt weathering of rock the wick effect is the upward migration of saline solutions into rocks and their subsequent crystallization lower carboniferous sandstone blocks of rectangular shape have been subjected to this process in the laboratory using a range of salt types a range of salt concentrations and various mixtures of salts some treatments produced severe disintegration notably sodium carbonate and a mixture of sodium carbonate with magnesium sulphate whereas other salts including sodium chloride and gypsum were much less effective the debris produced by this experimental salt weathering included appreciable quantities of silt sized material which were analysed with a laser granulometer such material could provide a source for desert loess

weathering of superficial limestone debris in a hot desert environment abstract weathering of superficial limestone debris is described from stone pavements on the hamada de meski in southeast morocco the dominant features are due to surface and subsurface solution mechanical weathering and aeolian action have only a limited effect microfeatures produced by solution include solution facetting microrills solution pits case hardening micropitting or vesicular weathering and possibly surface crazing such microforms are the most likely representatives of a truly arid karst

tomography based characterization of ice air interface dynamics of temperature gradient snow metamorphism under advective conditions snow at or close to the surface commonly undergoes temperature gradient metamorphism under advective flow which alters its microstructure and physical properties a functional understanding of this process is essential for many disciplines from modeling the effects of snow on regional and global climate to assessing avalanche formation time lapse x ray microtomography was applied to investigate the structural dynamics of temperature gradient snow metamorphism exposed to an advective airflow in controlled laboratory conditions experiments specifically analyzed sublimation and deposition of water vapor on the ice structure in addition an analysis of the ice air interface dynamics was carried out using a macroscopic equivalent model of heat and water vapor transport through a snow layer the results indicate that sublimation of the ice matrix dominated for flow rates 10 6 m3 s 1 while during increased mass flow rates the water vapor deposition supplied by the advective flow counteracted sublimation a flow rate dependence of water vapor deposition at the ice interface was observed asymptotically approaching an average estimated maximum deposition rate on the whole sample of 1 05 10 4 kg m 3 s 1 the growth of microsized whisker like crystals on larger ice crystals was detected on microscope photographs leading to an increase of the specific surface area and thus suggest a change of the physical and optical properties of the snow the estimated values of the curvature effect of the ice crystals and the interface kinetic coefficient are in good agreement with previously published values

reconstructing thermal properties of firn at summit greenland from a temperature profile time series we have constrained the value for thermal diffusivity of near surface snow and firn at summit station greenland using a fourier type analysis applied to hourly temperature measurements collected from eight thermistors in a closed off air filled borehole between may 2004 and july 2008 an implicit finite difference method suggests that a bulk diffusivity of 25 3m2 a 1 is the most reasonable for representing macroscale heat transport in the top 30 m of firn and snow this value represents an average diffusivity and in a conduction only model generates temperature series whose phase shifts with depth most closely match those of the summit borehole data rms difference between measurements and model output is 6 days this bulk value derived numerically and corroborated analytically is useful over large tracts of the greenland ice sheet where density and microstructure are unknown

the influence of climate during and after a glacial surge a comparison of the last two surges of fridtjovbreen svalbard abstract glacial surges are periods of fast flow often limited in space and time and driven by internal conditions which are not fully explained the quantity and variety of documented case studies and settings demonstrate that the critical variables are difficult to isolate in an alternative approach two surges from the same basin were compared at fridtjovhamna one of the few known sites where this is possible fridtjovbreen is a polythermal glacier that has been through two recent surges the last event 1991 2002 occurred during an unusually warm period in the high arctic whereas the previous surge culminated in 1861 around the little ice age when many svalbard glaciers had their maximum holocene extent based on a multi disciplinary study processes and landforms from the two episodes were compared with respect to ice front movement rates formation and decay of ice cored moraines and glacial meltwater drainage patterns the study demonstrates that moraines and meltwater traces from the oldest surge locally well preserved provide excellent opportunities for reconstructing the behavior of the ice mass the last surge however took place during a period with ablation rates never seen at this latitude and 10 years after the maximum extent the deglaciated areas onshore hardly show traces from the event

evolution of the academician ridge accommodation zone in the central part of the baikal rift from high resolution reflection seismic profiling and geological field investigations new high resolution seismic reflection data from the central part of lake baikal provide new insight into the structure and stratigraphy of academician ridge a large intra rift accommodation zone separating the central and north baikal basins four seismic packages are distinguished above the basement a thin top of basement unit seismic stratigraphic unit x seismic stratigraphic unit a and seismic stratigraphic unit b units a and b were cored on selected key locations the four packages are correlated with a series of deposits exposed on the nearby western shores the ularyar sequence oligocene the tagay sequence lower to middle miocene the sasa sequence upper miocene to lower pliocene the kharantsy sequence upper pliocene and the nyurga sequence lower pleistocene based on stratal relationships sedimentary geometries distribution patterns and principal morphostructural elements both onshore and offshore we propose a new palaeogeographic evolution model for the area in this model progressive tectonic subsidence of the baikal basins and successive pulses of uplift of various segments of the rift margins lead to a formation of the ridge as a structural and morphological feature separating the central and north baikal basins during the middle to late miocene b gradual flooding of the main parts of the ridge and establishment of a lacustrine connection between the two rift basins during the late miocene and c total submergence of the top parts of the crest of the ridge during the latest pleistocene this new model helps to better constrain numerous phases in the structural evolution of the baikal rift in which the academician ridge as an accommodation zone plays a crucial role

temperature measurements and heat transfer in near surface snow at the south pole to study near surface heat flow on the antarctic ice sheet snow temperatures were measured at south pole station to a depth of 3 m at 15 min intervals during most of 1992 solar heating and water vapor transport were negligible during the 6 month winter as was inter grain net thermal radiation leaving conduction as the dominant heat transport mechanism the rate of temperature change at depth over 15 min intervals was smaller than that at the surface by one order of magnitude at 20 cm depth and two orders of magnitude at 1 m depth a finite difference model with conduction as the only heat transfer mechanism and measured temperatures as the upper and lower boundary conditions was applied to foursets of three thermistors each the thermal conductivity was estimated as that which minimized the difference between modeled and measured 15 min changes in temperatures at the center thermistor the thermal conductivity obtained at shallow depths above 40 cm was lower than that given by existing parameterizations based on density probably because the snow grains were freshly deposited cold and poorly bonded a model using only vertical conduction explains on average 87 ofthe observed 15 min temperature changes at less than 60 cm depth and 92 below 60 cm the difference between modeled andmeasured temperature changes decreased with depth the discrepancies between model and observation correlated more strongly with the air snow temperature difference than with the product of that difference with the square of the wind speed suggesting that the residual errors are due more to non vertical conduction and to sub grid scale variabilis of the conductivity than to windpumping the residual heating rate not explained by the model of vertical conduction exceeds 0 2 w m 3 only in the top 60 cm of the near surface snow

reconstruction of snow firn thermal diffusivities from observed temperature variation application to iceberg c16 ross sea antarctica 2004 07 two inverse methods are proposed as a means of estimating the thermal diffusivity of snow and firn from continuous measurements of their temperature the first method is applicable to shallow depths where temperature experiences diurnal variations and is based on the fact that phase and amplitude of these diurnal variations are functions of the thermal diffusivity the second method is applicable to the deeper part of the firn layer and is based on a simple least squares estimation technique the methods applied here differ from various methods used for borehole paleothermometry in that observations are continuous in time and performance constraints on model data misfit can be applied over a finite temporal period both methods are tested on temperature records from thermistor strings operating in the upper 2 5m of firn on iceberg c16 ross sea antarctica from 2004 to 2007 results of the analysis show promise in identifying melting events and the movement and refreezing of meltwater within the snow firn layer

extensive boulder erosion resulting from a range fire on the type pinedale moraines fremont lake wyoming abstract in july 1988 the flatfish range fire burned over the type pinedale moraines at fremont lake wyoming and caused extensive exfoliation of exposed boulder surfaces the mass of exfoliated material from 130 of 1030 boulders investigated was measured and recorded with information concerning factors that could influence the extent of fire induced exfoliation the range in thickness of material removed from 98 randomly selected boulders within the burn area averaged over the entire exposed boulder surface area is 6 1 to

the major and minor element geochemistry of lake baikal funding for u s participation in the fieldwork and sample collection was provided by the u s national science foundation funding for the analytical work was obtained by various means

rock temperatures as an indicator of weathering processes affecting rock art to aid rock art conservation rock temperatures have been monitored at different depths and at low 30 min and high 1 min acquisition rates in a painted rock shelter in the ukhahlamba drakensberg park south africa preliminary data for winter cold and dry show that in that season cryoclasty is unlikely to occur rare subzero thermal events and probable reduced moisture availability and thermal shocks are improbable highest measured t t 2 c min 1 high amplitude about 30 c rock temperature cycles accompanied by reversals of the thermal gradient have been observed to occur almost daily and hint at the possibility of thermal stress fatigue copyright 2006 john wiley sons ltd

rare earth elements in the sediments of lake baikal lake baikal is the deepest and probably oldest lake on earth its water column is pervasively oxic and sedimentation rates are very low which leads to the formation of a dynamic iron fe and manganese mn enrichment below the mn ii o2 boundary these often massive accumulations can be buried within the reducing part of the sediments and give rise to complex and cryptic redox cycles the mobility of rare earth elements rees is influenced by the dissolution and reduction dynamics of the ferromanganese oxides the present study offers an overview of the ree chemistry in lake baikal and its catchment area and more specifically ree distribution in five 11 to 26 cm long sediment cores situated across the lake at different water depths we analysed and discussed normalised ree patterns and their consequential cerium ce anomalies while particulate ree concentrations are mainly influenced by processes above or near the surface of lake baikal such as the development of a widespread negative ce anomaly processes occurring during early diagenesis in the sediment are most reflected in pore water rees the dissolution of ferromanganese oxides at the mn ii o2 boundary remobilizes significant amounts of ree into the pore water whereby some are likely adsorbed onto colloidal fe oxides however besides the tendency of ce being associated with mn oxides pore water rees fractionate predominantly around the buried fe mn accumulation where light rees preferentially adsorb onto fe oxides

experimental determination of snow sublimation rate and stable isotopic exchange snow sublimation is a fundamental process that affects the snow crystal structure and is important for ice core interpretation remote sensing snow hydrology and chemical processes in snow prior studies have shown that sublimation can change the isotopic content of the remaining snow these studies have inferred sublimation rates using field data and were unable to control many of the environmental parameters that determine sublimation rate e g temperature relative humidity snow microstructure we present sublimation rate measurements on snow samples in the laboratory where we have controlled many of these parameters simultaneously we use the same experimental apparatus to determine sublimation rate investigate the isotopic effects of sublimation and study the isotopic exchange between vapor and solid our results suggest that pore spaces in snow are almost always at saturation vapor pressure undersaturation may be possible in large pore spaces or in regions of rapid interstitial airflow we present a revised formulation for determining the mass transfer coefficient for snow as a linear function of reynolds number hm 0 566re 0 075 estimate the fractionation coefficient for sublimating snow and provide evidence for isotopic exchange between vapor and solid

contour scaling of a sandstone by salt weathering under simulated hot desert conditions a laboratory study has been used to investigate relationships between salts and contour scaling a weathering feature commonly observed on rock surfaces in salt rich environments surface disaggregation and essentially surface parallel cracks were produced in sandstone blocks using 10 per cent solutions of sodium sulphate and magnesium sulphate applied daily to single exposed surfaces for sixty days a control block soaked once in saturated magnesium sulphate and subsequently wetted daily with distilled water showed extensive surface disaggregation but no cracking both surface disaggregation and subsurface cracking were associated with relative concentrations of microcrystalline salt a tentative model of contour scaling is proposed which involves linking together potential cracks by salt induced fracturing of intervening crack stopping grains further control blocks treated respectively with 10 per cent and saturated sodium chloride showed no evidence of subsurface cracking and only limited surface disaggregation of the saturated block

temperatures heating rates and vapour pressures in near surface snow at the south pole a finite volume model is used to simulate 9 years 1995 2003 of snow temperatures at the south pole the upper boundary condition is skin surface temperature derived from routine upwelling longwave radiation measurements while the lower boundary condition is set to the seasonal temperature gradient at 6 5 m depth taken from prior measurements at the south pole we focus on statistics of temperature heat fluxes heating rates and vapour pressures in the top metre of snow but present results from the full depth of the model 6 5 m the monthly mean net heat flux into the snow agrees with results from previous studies performed at the south pole on shorter timescales the heating rates and vapour pressures show large variability the net heat flux into the snow which is between 5wm 2 in the monthly mean can be greater than 20 w m 2 on hourly timescales on sub daily timescales heating rates exceed 40 k d 1 in the top 10 cm of the snow subsurface temperatures and therefore heating rates are more variable during winter april september due to increased synoptic activity and the presence of a strong surface based atmospheric temperature inversion the largest vapour pressures 60 70 pa and vertical gradients of vapour pressure are found in the top metre of snow during the short summer december january in contrast during the long winter the low temperatures result in very small vapour pressures and insignificant vapour pressure gradients the high summertime vapour pressure gradients may be important in altering the isotopic composition of snow and ice on the antarctic plateau

an investigation of the thermal conductivity of snow thermal conductivity of snow has been investigated experimentally using the thermal probe method which is a transient method of measurement the measurements have been made over a wide range of snow density for fresh and dense snow for varying temperatures and for different conditions of water content snow grain type etc both in the field and in the laboratory the results are presented along with detailed sample descriptions thermal conductivity of snow increases with density and water content it also increases with temperature and the effect is more pronounced for temperatures between 15 and 0 c

the terminology and the concepts of gypsum rich soils abstract many terms in earth sciences and their underlying ideas have been developed in temperate humid countries both geological and climatic reasons cause gypsum rich soils to occur in dry lands soil science has paid little attention to gypseous soils and this limited knowledge is reflected in the direct loan of customary terms of soil science that can lead to misconceptions on the composition and behaviour of soils with large proportions of gypsum elements for discussion on the use of sundry terms about soils containing gypsum are presented here and some of their implicit assumptions discussed some generic terms are examined as well as several expressions used by organizations devoted to soil survey and classification the transformations occurring in gypseous soils are discussed in particular the effects from exposure the refinements herein proposed aim to help understand the role of gypsum in local and global earth surface processes

origin and dynamics of fe and mn sedimentary layers in lake baikal remobilization and accumulation of iron and manganese were measured by porewater and sediment core analyses at six contrasting sedimentary environments of lake baikal with bulk sedimentation rates varying between 0 8 and 0 02 mm year 1 the results allow for the distinction between two types of fe and mn diagenesis in areas of relatively high sedimentation and in regions of low sedimentation rates in the first case only small fe mn enrichments near the sediment water interface were observed in the central and southern basins at the high sediment flux area near the selenga delta and in maloe more strait massive sedimentary layers enriched in fe and mn were found within the upper 15 25 cm of the sediments exclusively in northern baikal and in the underwater academician ridge which are characterized by low sedimentation rates and deep sulfate penetration depths in the porewaters the mn content in the enriched layers ranged from 10 5 mol cm 2 at the sites near the selenga delta up to 10 2 mol cm 2 at academician ridge the accumulation times for the enriched fe mn layers calculated from the size of the fe and mn oxide pools and the diffusive fluxes into the enriched zones also varied by a factor of 1000 they ranged from a few years near the selenga delta to several thousand years for the sites at academician ridge and northern baikal these values were generally congruent with the sediment age of the accumulation zones calculated from sedimentation rates these findings have significant implications for paleolimnological studies iron and manganese dynamics at sites with high sedimentation rates is dominated by allochthonous input which is only partially dissolved close to the sediment surface in contrast the massive fe mn sedimentary layers at sites of slow sedimentation are of autochthonous origin slow dissolution and reprecipitation maintain their constant position with respect to the sediment surface and prevent burial as long as the sedimentation regime remains constant buried fe mn sedimentary layers widespread in lake baikal may therefore serve as general indicators for low sedimentation rates and as specific proxies for sudden changes in the sediment regime d 2004 elsevier b v all rights reserved

depositional and tectonic framework of the rift basins of lake baikal from multichannel seismic data recent multichannel seismic reflection data from lake baikal located in a large active continental rift in central asia image three major stratigraphic units totaling 3 5 to 7 5 km thick in four subbasins a major change in rift deposition and faulting between the oldest and middle rift units probably corresponds to the change from slow to fast rifting in early pliocene time inferred from on land studies a minor modification of fault patterns characterizes the youngest unit a brief comparison of the basins of lake baikal with those of the east african rift system highlights differences in structural style that can be explained by differences in age and evolution of the surrounding basement rocks

a new age model for the sediment cores from academician ridge lake baikal based on high time resolution ams 14c data sets over the last 30 kyr paleoclimatic and environmental implications abstract we constructed a new age model based on high time resolution 14 c data sets from three sediment cores from academician ridge lake baikal for reconstruction of environmental and biological changes in southern siberia during the last ca 30 kyr we used 14 c ages of total organic carbon toc for the model because terrestrial plant residues and biogenic carbonate were not observed in the sediments for accurate dating and age models based on 14 c ages of toc the freshwater 14 c reservoir effect and the effect of dead carbon from land derived organic materials must be estimated in this study we estimated the correction factor for these effects to be 2100 90 yr on the basis of a key layer the 14 c plateau caused by changes in the atmospheric 14 c concentration during the younger dryas yd cooling event the new age scale along with the toc mass accumulation rate mar toc and stable carbon isotope ratio in the sediment cores clearly indicate a rapid decrease in lake productivity and reduced influx of terrestrial organic materials into the lake during the yd 12 8 11 6 cal ka bp productivity was high mar toc up to 19 7 mg cm 2 kyr in and around lake baikal during 9 3 6 4 cal ka bp holocene climate optimum moreover paleoproductivity changes during the last ca 30 kyr in and around the lake baikal were clearly associated with fluctuations in the east asian monsoon intensity as inferred from the 18 o record from sanbao and hulu caves china during the late quaternary wang et al 2008 nature 451 1090 1093

unusual phosphate concretions related to groundwater flow in a continental environment abstract occurrence of phosphate cemented sandstone concretions in alluvial sand containing archaeological layers implies that they have formed during the last 2000 years morphology and petrography of the concretions indicates a relationship with groundwater cementation the phosphate cement of the concretions consists of concentric isopachous aureoles about 10 m thick that wrap the detrital grains aureoles are formed of collophane the cryptocrystalline or amorphous variety of hydroxyapatite geochemical modeling indicates that the apatite cement likely results from the leaching of a preexisting phosphate deposit bones in an acidic soil environment and the precipitation of dissolved phosphate under ph control at the mixing zone of down moving soil water with the calcite saturated groundwater

a rock magnetic record from lake baikal siberia evidence for late quaternary climate change rock magnetic measurements of sediment cores from the academician ridge region of lake baikal siberia show variations related to late quaternary climate change based upon the well dated last glacial interglacial transition variations in magnetic concentration and mineralogy are related to glacial interglacial cycles using a conceptual model interglacial intervals are characterized by low magnetic concentrations and a composition that is dominated by low coercivity minerals glacial intervals are characterized by high magnetic concentrations and increased amounts of high coercivity minerals the variation in magnetic concentration is consistent with dilution by diatom opal during the more productive interglacial periods we also infer an increased contribution of eolian sediment during the colder windier and more arid glacial conditions when extensive loess deposits were formed throughout europe and asia eolian transport is inferred to deliver increased amounts of high coercivity minerals as staining on eolian grains during the glacial intervals variations in magnetic concentration and mineralogy of lake baikal sediment correlate to the specmap marine oxygen isotope record the high degree of correlation between baikal magnetic concentration mineralogy and the specmap oxygen isotope record indicates that lake baikal sediment preserves a history of climate change in central asia for the last 250 ka this correlation provides a method of estimating the age of sediment beyond the range of the radiocarbon method future work must include providing better age control and additional climate proxy data thereby strengthening the correlation of continental and marine climate records

surface temperature differences between minerals in crystalline rocks implications for granular disaggregation of granites through thermal fatigue thermal expansion differences between minerals within rocks under insolation have previously been assumed to drive breakdown by means of granular disaggregation however there have been no definitive demonstrations of the efficacy of this weathering mechanism different surface temperatures between minerals should magnify thermal expansion differences and thus subject adjacent minerals to repeated stresses that might cause breakdown through fatigue failure this work confirms the existence of surface temperature differences between minerals in granitic rocks under simulated short term temperature fluctuations so as to discriminate their potential for initiating granular disaggregation the influence of colour as a surrogate for albedo and crystal size as a function of thermal mass are specifically identified because of their ease of quantification four rock types with a range of these properties were examined and subjected to repeated short term temperature cycles by radiative heating and cooling under laboratory conditions results show that while albedo is the main control for overall and individual maximum temperatures crystal size is the main factor controlling higher temperature differences between minerals thus stones with large differences of mineral sizes can undergo magnified stresses due to thermal expansion differences

rock temperatures from southeast morocco and their significance for experimental rock weathering studies surface and subsurface rock temperature measurements are presented from three rock types chalk granite and sandstone from a hot desert climate the temperature regimes undergone by each rock type and the differences between them can be best explained by reference to the values of albedo and thermal conductivity for the rocks the significance of thermal properties in influencing rock temperatures suggests that these properties should be taken into account when attempting to simulate desert weathering and also when trying to explain variations in the weathering behavior of different rock types

authigenesis of vivianite as influenced by methane induced sulfidization in cold seep sediments off southwestern taiwan abstract authigenesis of iron rich phosphate nodules occurs in iron rich cold seep sediments md052911 core at yung an ridge offshore southwestern taiwan raman ftir and quantitative x ray energy dispersive spectroscopic analyses indicate that the phosphate mineral is vivianite or baricite and shows fe mg molar ratios spanning from ca 0 6 to 4 0 and a general down core trend of increasing fe mg ratios the formation of vivianite is limited to a depth interval of 13 17 mbsf meters below seafloor and is most prominent at 16 mbsf in association with high dissolved iron concentrations and depleted dissolved sulfide below a peak sulfidization zone enriched in mackinawite and greigite alternate growths of vivianite and iron monosulfides and compositional zoning with mg enriched towards the peripheries of individual nodules occur in the transition from the zone of vivianite mineralization to the sulfidization zone the crystallization of vivianite below the sulfidization front could have been favored by scavenging of downward diffusive dissolved sulfide from pore waters in the sulfidization zone alternate growths and overlapping of the zones of iron monosulfides and vivianite can be attributed to fluctuations of the sulfidization front and methane flux the discovery of vivianite in the yung an ridge sediments implies that authigenic vivianite can be an important sink for phosphorus burial in cold seep sediments that have high reactive iron contents and high sedimentation rates

effect of atmospheric water vapor on modification of stable isotopes in near surface snow on ice sheets south pole are used to simulate the d 18 o of near surface snow as it evolves in time the sensitivity of d 18 o of near surface snow to wind speed surface temperature and accumulation rate is tested through model experiments a steady wind of 5 10 m s 1 results in annual mean d 18 o enrichment of 3 7 enrichment of the heavy isotope occurs predominantly in buried winter snow layers during summer however in many simulations there is a slight depletion of d 18 o summer layers that occurs as atmospheric water vapor is deposited within the snow during winter postdepositional modification of water stable isotopes in near surface snow also depends on the snow accumulation rate high accumulation rates quickly advect snow layers away from the influence of the atmosphere preventing significant modification low accumulation rates e g at vostok and dome c allow significant postdepositional modification because the near surface snow is exposed to forced ventilation for several annual cycles postdepositional modification during the last glacial maximum lgm at summit greenland is estimated to be greater than the present day postdepositional modification therefore the temperature difference for lgm may be larger than that previously inferred from the d 18 o record however because of the compensating effects of lower temperatures and smaller accumulation during the lgm in antarctica the postdepositional enrichment in east antarctica may be approximately the same for lgm as for the modern climate

the structure and development of the baikal rift depression abstract the baikal rift depression located in southeastern siberia is one of the best investigated intra continental rift structures in the world in addition to being the site of comprehensive studies by russian geo scientists for decades the baikal depression is now the subject of new international investigations using advanced technical means and technologies the present paper summarizes the principal results concerning the morphostructure of the baikal rift the stratigraphy of the cenozoic deposits and the stages of the baikal depression development based on cross sections which exhibit the impact of both tectonic and climatic processes the development of the baikal depression occurred through two stages i the pre crypto rift stage of the late cretaceous eocene and ii active rifting of the oligocene recent the second stage is divided into several steps and substeps separated by tectonic phases formation of the baikal rift zone appears to be related to the indo eurasian plate collision related to a model of passive rifting the uplifted shoulders of the depression have a complex morphostructure overlain by cenozoic deposits which are thin and restricted in area the near marginal zones of the rift are largely defined by the system of longitudinal blocks of different width surfaces of the blocks are inclined either to the uplifted shoulder of the rift bound by listric faults typical for western edges of the depression or to the axis of the depression cenozoic deposits on the blocks consist of accumulative plains composed primarily of thick lacustrine sequences

non climate influences on stable isotopes at taylor mouth antarctica the late holocene trends in 18 o differ significantly in two ice cores 30 km apart from the area of taylor dome antarctica it is unlikely that the trend in the core from taylor mouth the flank site is due to a standard 18 o surface temperature relationship assuming that the taylor dome near summit core records local climate variations common to both cores we assess two leading possible causes for the observed differences 1 relative to taylor dome taylor mouth may collect snow from more sources with distinct isotopic compositions 2 vapor motion during prolonged near surface exposure may cause post depositional isotope enrichment at taylor mouth where the accumulation rate is low our model of firn pore space vapor and sublimating ice grains suggests that post depositional processes can modify 18 o values by several o isotopic samples from areas with significantly different accumulation rates near taylor mouth could differentiate between possibilities 1 and 2

seismic deformation of varved sediments in southern fennoscandia at 7400 cal bp abstract soft sediment deformation structures are preserved in clastic biogenic varves of the lake nurmijarvi sequence from central southern finland deformation structures include centimeter scale folding and faulting structures and larger convolute bedding which are separated from the overlying undisturbed varved section by a turbidite dated at 7400 cal bp the soft sediment deformation provides evidence for postglacial seismic activity ca 3500 years after the deglaciation of the study area by screening the sizes of potential source faults for the event the maximum earthquake moment magnitudes associated with the deformation structures were constrained to mw 5 1 6 9 with realistic 40 rupture scenarios or up to mw 5 1 7 7 if more conservative scenarios are considered the results of the study thus indicate a relatively high magnitude postglacial seismic event in southern finland which adds to the evidence that the postglacial seismic activity was not just restricted to northern fennoscandia but was a more widespread phenomenon the age of the lake nurmijarvi seismic event further demonstrates that high magnitude seismic activity was not restricted to a relatively short period after deglaciation but the period of high magnitude postglacial seismic activity was much longer than previously thought by assessing the orientations of faults that are presently active and using available focal mechanism data our results suggest that strike slip faulting may be a more important mechanism for the generation of both present day and postglacial earthquakes in southern finland than reverse faulting which should further be accounted for in the assessment of long term seismic hazards

high time resolution ams 14c data sets for lake baikal and lake hovsgol sediment cores changes in radiocarbon age and sedimentation rates during the transition from the last glacial to the holocene abstract high time resolution 14 c dating of lake baikal sediment cores indicates negative and positive anomalies of calculated linear sedimentation rate lsr 1 1 and 35 6 cm ka respectively during the period of climate transition from the last glacial to holocene the timing of the lake baikal apparent lsr anomalies is consistent with that of the changes in the atmospheric radiocarbon concentration 14 c during younger dryas rapid cooling event 14 c dating of lipids in the lake baikal surface sediments revealed that the sources of sedimentary lipids were different in each basin in the northern basin of lake baikal the 14 c age of total lipids from the surface sediment 4 0 14 c ka was found to be older than that of toc 1 6 14 c ka by contrast the 14 c age of total lipids in the southern basin was younger than that of the toc by ca 0 7 3 0 ka in the lake hovsgol sediment cores ages of the main lithologic boundaries during the last glacial interglacial transition were estimated based on new 14 c data sets toc concentration in the cores started to rapidly increase at 13 8 0 3 14 c ka at the base of the basinwide finely laminated layer deposited during bolling allerod the base of the layer diatomaceous mud corresponds to the end of younger dryas event 10 6 0 1 14 c ka

influence of surface heterogeneities of building granite on its thermal response and its potential for the generation of thermoclasty surface properties especially albedo and aspect are widely accepted as strong influences on the surface thermal response of building stone to insolation however the influence that adjacent areas of stone with very different surface properties may have on the thermal response of a patch of stonework and the ways in which spatial variation in thermal characteristics might enhance stone decay has received relatively little attention this paper examines the differential thermal response of granite used in construction that results from the presence of dark coloured micro granular enclaves within a leucocratic host surface temperatures and temperature differences between enclaves exhibiting mico spalling enclaves with no spalling and the surrounding stone were measured for different aspects and seasons on a 20th century building in madrid these data were used to calculate a number of indices related to short term temperature cycling and temperature gradients that have the theoretical capability of generating irreversible deformation of the stone these indices suggest that micro spalling of enclaves compared to a lack of similar decay on the host rock is related to their differential thermal response to insolation most importantly the lower albedo and thermal conductivity values of the enclaves however these factors are not sufficient on their own to trigger spalling and breakdown was only observed where enclaves also experienced repeated short term surface temperature cycling caused by for example temporary shading by adjacent vegetation these rapid temperature reversals are identified as a key contributory factor to the thermally driven decay observed on some of the enclaves

theory of metamorphism of dry snow the growth of ice particles in dry seasonal snow is caused by vapor diffusion among particles due to temperature gradients imposed on the snow cover the diffusion is calculated by using the potential field solutions for electrostatically charged particles the stereography of snow is represented by using a log normal distribution function for a geometrical enhancement factor defined here reasonable crystal growth rates and supersaturations are found the transition between the growth of highly faceted crystals and the growth of highly rounded crystals is determined by the critical supersaturation for the onset of dislocation aided growth thermal convection and the continuous movement of vapor around the particles due to the imposed temperature gradient are accommodated in the theory although both have little effect relative to the interparticle diffusion the growth of a layer of faceted crystals just below semi permeable crusts is explained by showing that crusts can cause the local supersaturation to exceed the critical value faceted crystals are shown to grow most rapidly in the lower warmer portions of the snow cover because of temperature effects on growth rate

authigenic apatite formation and burial in sediments from non upwelling continental margin environments abstract evidence for precipitation of authigenic carbonate fluorapatite cfa in long island sound and mississippi delta sediments suggests that formation of cfa is not restricted to environments of active coastal upwelling we present porewater data suggestive of cfa formation in both these areas application of a sequential leaching procedure designed specifically to separate authigenic carbonate fluorapatite from other phosphorus containing phases including detrital apatite of igneous or metamorphic origin provides strong supporting evidence for authigenic apatite formation in these sediments the size of the authigenic apatite reservoir increases with depth indicating continued formation of cfa during early diagenesis this depth increase is mirrored by a decrease in solid phase organic p at both sites suggesting that cfa is forming at the expense of organic p mass balance considerations application of diagenetic models to interstitial water nutrient data and the saturation state of the interstitial water are consistent with this interpretation diagenetic redistribution of phosphorus among the different solid phase reservoirs is observed at both sites and results in near perfect retention of p by these sediments over the depth intervals sampled formation of cfa in continental margins which do not conform to the classically defined regions of phosphorite formation renders cfa a quantitatively more important sink than has previously been recognized including this reservoir as a newly identified sink for reactive p in the ocean the residence time of p in the modern ocean must be revised downward the implication for ancient oceans of cfa formation in continental margin sediments other than phosphorites is that phosphorite formation may be less a representation of episodicity in removal of reactive p from the oceans than of localized concentration of cfa in phosphatic sediments by secondary physical processes

bound forms compositional features major sources and diagenesis of long chain alkyl mid chain diols in lake baikal sediments over the past 28 000 years abstract to elucidate the possibility of long chain alkyl mid chain diols hereafter mid chain diols in lake baikal sediments over the past 28 ka being paleoproxies we studied their i bound forms and compositional features ii major sources and iii diagenesis during sedimentation of the seven bound forms investigated i e free form free type three base hydrolysable types base 1 base 2 and base 3 and acid hydrolysable type acid 1 type in solvent extractable lipids and base hydrolysable nb and acid hydrolysable na types in non solvent extractable nonex lipids only three viz free nb and base 3 types were found the relative compositions of the three types were 70 100 0 30 and 0 8 respectively the most abundant component of the free type diols was the c 32 1 15 diol whereas that of the base 3 and nb types was the c 30 1 13 diol the average chain length ratio of total amount of even chain lengths to that of odd chain lengths the relative composition of positional isomers for each carbon number and the diol index obtained using the equation c 30 1 15 diol c 30 1 15 diol c 32 1 15 diol 100 hardly responded to reported major paleoenvironmental changes around the lake baikal region over the last 28 ka comparison of mid chain diol compositions and their bound forms with those in possible sources suggested that the major biological source of all mid chain diols in the sediments might be the eustigmatophyceae class of algae in the alga the occurrence of mid chain diols in the five bound forms free base 3 acid 1 nb and na types was suggested while the acid 1 and na types were not found in the sediments under the oxic depositional conditions of lake baikal most of the acid 1 and na type diols and part of the base 3 and nb type diols might be degraded and or released free type diols in the anoxic sediments of the lake the base 3 and nb diols seem to be resistant to diagenesis all investigated parameters for the free base 3 and nb diols in the sediments did not provide any information on paleoenvironments around the lake on the other hand among the fluxes of the three diol types the base 3 type diol flux seems to have responded to the climatic events around the lake especially over the last 15 ka hence this flux might be a potential paleoproxy for the productivity of the biological source s and associated environmental factors

thermal effects due to air flow and vapor transport in dry snow the thermal effects of air flow forced through a snow sample are investigated numerically a new method for calculating vapor transport in snow is presented which allows for the determination of the effects of sublimation in this method the snow is not assumed to be saturated with water vapor results of the model show very good agreement with analytical and experimental results

natural convection in the subarctic snow cover the purpose of this study was to determine if air convects in a natural snow cover to detect convection the temperature field in the subarctic snow cover in fairbanks alaska was measured hourly during three winters 1984 1987 using an array of thermistors which were suspended on threads and allowed to be buried by snowfall the results indicate that convection occurred sporadically in 1984 1985 and almost continuously in 1985 1986 and 1986 1987 the evidence was 1 simultaneous warming and cooling at different locations in a horizontal plane in the snow and 2 horizontal temperature gradients of up to 16 c m 1 during the winter warm and cold zones developed in the snow and remained relatively fixed in space we interpret these zones to be the result of a diffuse plumelike convection pattern linked to spatial variations in the temperature of the snow soil interface air flow was inferred to have been primarily horizontal near the base of the snow and vertical elsewhere calculated flow speeds were of the order of 0 2 mm s 1 with a maximum value of 2 mm s 1 the convective circulation was time dependent with perturbations such as high wind or rapid changes in air temperature triggering periods when horizontal temperature gradients were strongest suggesting that these were also periods when the air flow was fastest the coincidence of depth hoar crystals with horizontal c axes and the horizontal flow lines at the base of the snow suggests that convection may have affected crystal growth directions

continental climate response to orbital forcing from biogenic silica records in lake baikal changes in insolation caused by periodic changes in the earth s orbital parameters provide the primary forcing for global ice ages1 6 but it is not clear to what extent the climates in continental interiors are controlled directly by regional variations in insolation and to what extent they are driven instead by the highly nonlinear response of the oceans and ice sheets here we investigate this question using the record of biogenic silica in lake baikal as a proxy for climate change in this high latitude mid continental region we find a good correlation between this record and that of marine oxygen isotopes4 over the past 250 kyr the baikal record exhibits both a strongly nonlinear component manifested in a 100 kyr periodicity and weaker direct insolation components manifested in the 41 kyr obliquity and 23 and 19 kyr precession orbital cycles these results show that even though extreme continental climates such as this are influenced directly by insolation variations they are dominated by the nonlinear rhythm of the oceans and ice sheets

formation of ferric iron crusts in quaternary sediments of lake baikal russia and implications for paleoclimate phosphate bearing ferric iron and siliceous crusts ranging in age from recent to approximately 65 000 yr b p are observed in sediments of lake baikal in younger sediments the crusts are at the base of a spectrum of secondary iron and manganese oxides that accumulate near the sediment water interface in the zone of positive oxidation potential beneath an oxygenated water column in areas where the average quaternary sedimentation rates have been slow e g 0 026 mm yr the crusts are more common and span a wider range of ages no crusts have been found where the quaternary sedimentation mode has been deltaic and rapid 0 15 mm yr independent core correlation based on magnetic properties of the sediment suggests that crusts can be correlated over most of academician ridge an area that is particularly sensitive to climatic events affecting the concentration of suspended sediment these crusts may be indicative of periods of low suspended sediment concentration which occur during sustained transitions from glacial periods of high detrital input to interglacial periods of high diatom sedimentation the crusts are dominated by iron rich and siliceous amorphous mineral phases with an feo sio2by weight of 3 1 regardless of age or location in the lake the fe phase always includes ca p and mn extensive microprobe data for these four elements recast as normalized elemental weight percent reveal linear trends of ca p and fe p with increasing p ca also increases such that the two elements maintain a linear relationship passing very close to the origin and with a mean molar ca p 0 3 too low for well characterized apatite conversely with increasing p fe decreases mean molar fe p 3 4 there is no correlation between mn and p molar fe p ratios for vivianite an fe ii phosphate mineral observed in sediments closely below some crusts are clustered around a stoichiometric composition the covariant increase in ca p and the corresponding decrease in fe p may be explained by 1 coupled adsorption of aqueous ca and p by a colloidal ferric hydrous oxide 2 loss of fe from a ca p fe phase or 3 oxidation of vivianite to a metastable mineral phase that gradually loses ca and gains fe the first explanation is favored because there is no petrographic evidence for either the existence of an originating ca p fe phase or for the oxidation of vivianite further it is suggested that by continually equalizing surface charge ca allows more phosphate to be adsorbed leading to thicker crusts and longer preservation after burial

deep ventilation of lake baikal waters due to spring thermal bars increase of density due to mixing cabbeling instability in a spring thermal bar in lake baikal results in the sinking of cold surface water t 3 2 3 4 c w 0 3 cm s 1 below the profile of tmd this density increase generates forced convection and subsequent movement of cold water along the underwater slope to maximum depths cooling of deep and near bottom waters caused by forced convection is compensated during other seasons of the year by eddy heat flux directed toward the bottom on a long term basis vertical temperature profiles in deep waters remain constant

new insights into the formation and burial of fe mn accumulations in lake baikal sediments abstract lake baikal is the deepest and oldest lake on earth extraordinary features of the lake are manganese and iron enriched layers and crusts occurring at different depths within the sediment they can be broadly subdivided into an upper accumulation at the o 2 mn ii redox boundary and one or more layers buried within the reducing part of the sediment the processes leading to their formation and peculiar distribution within the sediment have remained subject of debate in particular whether the burial of vast amounts of mn and fe oxides results from a steady state process or if it is the consequence of singular events such as changes in sedimentation rate bottom water oxygen concentrations or the mass accumulation rate mar of organic carbon c org mn or fe we retrieved short cores from the south basin the north basin and academician ridge determined sedimentation rates contents of c org mn and fe and estimated pore water fluxes from concentration profiles of o 2 no 3 mn ii fe ii so 4 2 and ch 4 a consistent picture emerged from the data showing that the upper fe mn layer formed at the lower end of the oxygen penetration depth as a dynamic pattern moving upward with the growing sediment thereby reductive dissolution of mn iv occurred at the lower margin upward diffusing mn ii was oxidized with o 2 forming the upper boundary of the fe mn accumulation the buried fe mn layers were immobilized within the sediment and underwent slow reductive dissolution mainly driven by the anaerobic oxidation of ch 4 the process leading to the detachment of the active fe mn layer from the top redox interface is not unambiguously clear however we suggest a cyclic pattern where the burial of a fe mn layer is accompanied by the generation of a new enrichment at the o 2 mn ii redox boundary which is subsequently nourished by the slowly dissolving old layer

thermal properties as controls on rock surface temperature maxima and possible implications for rock weathering four rock types basalt sandstone granite and chalk are examined with respect to the maximum surface temperatures which they experience when subjected to similar conditions of exposure rock temperature measurements are reported for an urban environment and for two experimental situations in which an infrared lamp is used to simulate heating under cold and hot conditions differences in rock temperatures are discussed with reference to thermal rock properties albedo specific heat capacity and thermal conductivity some natural situations are suggested in which thermal rock properties could conceivably play a role in determining the extent to which rocks would be affected by particular weathering processes

sandstone weathering a century of research and innovation abstract a review of sandstone weathering research particularly in the past 100 years reveals a trajectory of enquiry from early description and classification of features to development of process based explanations to decreasing scales of investigation and a disparity between understanding of process es and explanations of the genesis of sandstone weathering features developments in expositions on mesoscale weathering features on sandstone surfaces are discussed demonstrating a range of approaches to weathering phenomena field based and laboratory based that must be linked to provide an explanation of observed features on a landform scale throughout the twentieth century a thematic chronology highlights certain trends in research description of forms often in arid and semi arid environments single process form models an emphasis on experimentation difficulties in measuring weathering rates and a persistent emphasis on physical causes of breakdown a new research agenda is promoted in which biodeterioration and chemical processes gain parity a holistic approach based on conceptual modeling of weathering systems gains prominence and scale issues are addressed more rigorously

the role of grain dissolution and diagenetic mineral precipitation in the cycling of metals and phosphorus a study of a contaminated urban freshwater sediment this paper describes the detrital mineralogy early diagenetic reactions and authigenic mineral precipitates for freshwater contaminated sediments deposited in an urban water body the salford quays of the manchester ship canal greater manchester uk these sediments contain a mix of natural and anthropogenic detrital grains detrital grains are dominated by quartz and clay grains whilst anthropogenic grains are dominated by metal rich glass grains concentrated at a depth of 12 17 cm in the sediment as a result of historical inputs sediment porewaters contain significant concentrations of fe mn zn and phosphate bacterial fe iii and mn iv reduction are hypothesised to supply fe2 and mn2 to porewaters with phosphate released from fe oxide reduction or organic matter oxidation petrographic observations indicate that the metal rich glass grains are undergoing chemical dissolution during early diagenesis supplying fe and zn to porewaters the most abundant authigenic mineral in the sediments is vivianite fe3 po4 2 8h2o containing a significant level of redlingite with minor framboidal pyrite fes2 electron microprobe analysis shows the vivianite to contain zn cu and pb suggesting that vivianite acts as a long term sink for these metals in this sediment this implies that authigenic vivianite in freshwater sediments may act as a long term sink for metals in a similar manner to sulphides in marine sediments this study highlights that the nature of detrital and diagenetic mineralogy in addition to porewater and sediment chemistry needs to be considered in assessing contaminated sediments

two hourly surface change on supra tidal rock marengo victoria australia a traversing micro erosion meter was used to measure rock surface micro topography over 40 cm2 on a supra tidal cliff face from early morning to late evening in late spring from 06 00 hours to 22 00 hours the relative heights of 188 coordinates were obtained using the meter at 2 hour intervals resulting in a data set of 1607 readings monitoring shows that rock surfaces are dynamic entities with significant rise and fall relative to the first measurement at shorter timescales than previously reported the maximum positive rise between readings was 0 261 mm and lowering was 0 126 mm the pattern of change did not relate as expected to environmental variables such as temperature or insolation rather the surface showed greater surface change in the early morning and late afternoon it is hypothesized that this pattern relates to the expansion and contraction of lichen thalli as moisture is absorbed during higher humidity in the morning and late afternoon the implications of these results for weathering studies are considered copyright 2006 john wiley sons ltd

primary aerosol sea salt and soil dust deposited in greenland ice during the last climatic cycle comparison with east antarctic records ion chromatography data of ca mg cl and ca and coulter counter particle measurements are used to study the cycle of marine and continental primary aerosol reaching greenland in relation to climatic changes over the last 150 kyr a detailed comparison between greenland dome summit and antarctic vostok records provides new insight on a potential link between northern and southern patterns ca is a good indicator of continental input and is mainly emitted as caco3 an attempt is made to estimate the contribution of aluminosilicates using the concentration of insoluble particles greater than 0 5 m in diameter the relative abundance of non sea salt mg and ca and of aluminosilicate shows that the calcium content of continental background aerosol over greenland was much higher during the glacial age the neutralization capacity of carbonaceous aerosol is estimated the inverse relationship between 18o and continental input as well as the response of this input to the rapid climatic variations that have occurred during the second part of the glacial age are discussed in terms of source and transport modification in relation to the presence and the extent of the great laurentide ice cap the corresponding vostok profiles strongly suggest that some of the phenomena observed at high northern latitudes are of global concern the marine component of na nam is a good tracer of sea salt aerosol similarly to continental input it shows an inverse but more linear relationship with 18o the sensitivity of greenland and antarctic marine input to climate variations of small and large amplitude is compared and a corresponding estimation is made for the aeolian contribution the respective influence of atmospheric circulation and the water vapor cycle is discussed the chlorine to marine sodium weight ratio increases with temperature from values very close to the bulk seawater ratio during the last glacial maximum 18 20 kyr b p to values significantly higher during the holocene and warm eemian the corresponding excess of chloride hcl is discussed in terms of atmospheric transport taking into account the role of atmospheric acidity on sea salt fractionation processes owing to postdepositional phenomena similar vostok data must be considered cautiously nevertheless aerosol fractionation seems to have been much more important over the vostok site except during glacial extrema

biogeochemical phosphorus mass balance for lake baikal southeastern siberia russia abstract extensive data for lake baikal have been synthesized into a geochemical mass balance for phosphorus p some of the p budget and internal cycling terms for baikal have been compared to similar terms for oligotrophic lake superior mesotrophic lake michigan and the baltic sea and the ocean lake baikal has a large external source of fluvial p compared to the laurentian upper great lakes and the ocean the major tributary to lake baikal has experienced substantial increases in organic p loading during the past 25 years this coupled with potential p inputs from possible phosphorite mining may threaten baikal s oligotrophic status in the future water column remineralization of particulate organic p is substantially greater in lake baikal than in the laurentian great lakes this is probably due to the great water depths of lake baikal there is a gradient in p burial efficiency with very high values 80 for lake baikal and lake superior lower values 50 for lake michigan and the baltic sea and a low value 13 for the ocean the accumulation rate of p in lake baikal sediments is somewhat greater than that in the laurentian upper great lakes and the baltic sea and much greater than in the ocean benthic regeneration rates are surprisingly similar for large lacustrine and marine environments and supply less than 10 of the p utilized for primary production in these aquatic environments