late quaternary chronology of tufa deposits walker lake nevada walker lake a terminal desertic lake in mineral county nevada has fluctuated greatly in lake level throughout its long history due to changes in climate and drainage in its late pleistocene high stand walker lake formed the southernmost embayment of pluvial lake lahontan calcareous tufa and other shoreline deposits of pleistocene and holocene ages provide a valuable record of past lake levels studies of tufa morphology and stable isotope character closely integrated with sedimentologic data show great promise for elucidating the post glacial climatic history of the great basin three prominent shoreline carbonate deposits below 1250 m have been studied in the field and with stable isotope and radiocarbon analyses the oldest deposit 18 000 radiocarbon yrs b p consists of massive bowl shaped tufa heads outcropping from conspicuous wavecut and fan deltaic terraces three bigheads are covered by alluvial fan deposits which in turn are coated by an encrusting tufa of 3 cm average thickness

lithium saltworks of the salar de atacama a model for mgso 4 free ancient potash deposits abstract potash basins similar to those in the geological past no longer exist at present there are only hypersaline lakes such as those in the tibetan plateau where carnallite kcl mgcl2 6h2o precipitates given that the purpose of common saltworks is to obtain nacl the halitic stage is not exceeded by contrast saltworks extracting lithium by solar evaporation reach more advanced stages of brine evolution and saline precipitation in the salar de atacama saltworks with a relative humidity commonly below 30 monthly average salts precipitate following a sequence of halite nacl sylvite kcl carnallite and bischofite mgcl2 6h2o and display a useful model of evolution similar to that which gave rise to mgso4 free potash deposits in the past prismatic acicular gypsum caso4 2h2o the main accessory mineral is transformed into a less hydrated calcium sulfate probably anhydrite caso4 during carnallite precipitation mineral crystal size and annual sedimentary thickness of each paragenesis are compared with those in ancient potash deposits the behavior of sylvite and carnallite as cements is observed at the onset of their precipitation in ponds where both minerals coexist with previous halite millimeter cyclicity due to day night thermal variations is observed in these saltworks whereas cm and mm cyclicities have been interpreted in ancient sites as annual regular and intra annual irregular respectively conditions similar to those existing at the salar de atacama were necessary to preserve carnallite which is commonly the most evolved mineral in the ancient deposits the development of potash deposits in the south pyrenean foreland basin and the rhine graben near the eocene oligocene boundary is attributed to global aridity and cooling and to the basin restriction associated with a decrease in the ocean level caused by the spread of the antarctic ice cap

evaporites and siliciclastics of the permian nippewalla group of kansas usa a case for non marine deposition in saline lakes and saline pans the mid permian nippewalla group of kansas consists of bedded evaporites red bed siliciclastics and grey siliciclastics deposited in a non marine environment lithologies and sedimentary features indicate lacustrine and aeolian deposition subaerial exposure and palaeosol formation grey siliciclastic mudstones characterized by planar and convolute laminations ostracods peloids and plant material represent a freshwater brackish perennial lake facies bedded anhydrites containing gypsum crystal pseudomorphs clastic anhydrite grains and grey mud drapes and partings suggest deposition in saline lakes bedded halites consist of chevron and cumulate crystals dissolution surfaces and pipes and mudcracked microcrystalline salt crusts which were deposited in saline pans dominated by flooding evaporative concentration and desiccation chaotic halite composed of red bed mudstone and siltstone with displacive halite crystals formed in saline mudflats red bed mudstone and siltstone with little or no displacive halite but with abundant cracking root and plant features suggest deposition in a dry mudflat red bed sandstone composed of well sorted well rounded quartz grains cemented with halite indicate aeolian and rare shallow water deposition most deposition took place in halite dominated ephemeral saline lakes surrounded by saline and dry mudflats sandflats and sand dunes evaporation desiccation flooding and wind played significant roles in this environment the nippewalla group siliciclastics and evaporites represent an evolution from a perennial lacustrine system to a non marine acidic saline pan system in the mid continent of north america the problem of distinguishing between ancient marine and non marine evaporites as well as recognizing those evaporites deposited in acid settings with detailed field core and petrographical study of both evaporite deposits and associated sedimentary rocks has successfully been addressed in addition interpretations of mid permian palaeoclimate data in the form of short term air temperature proxies within longer term wet dry trends have been made these data provide a new palaeogeographic and palaeoclimatic model for the mid permian of western pangaea

environmental implications of salt facies in the dead sea thick sequences of salt halite have been recovered in a 456 m long core drilled at the deepest floor of the dead sea by the dead sea deep drilling project and extending 200 k y back in time the salt sequences were precipitated in the ancient lake that occupied the dead sea basin during the last three interglacials during intervals of extreme aridity in the lake s watershed the salt layers alternate with mud layers that indicate wetter periods in the watershed when floods transported fine detritus matter to the lake the salt sources include brine discharge and freshwater runoff that dissolved halite units dissolved salts accumulated in the lake during glacials and relatively wet periods when the lake expanded and precipitated during interglacials when the lake levels dropped this study establishes for the first time the evaporite facies and sedimentological features of the deep dead sea brine during interglacial periods by using the modern precipitation of halite in the dead sea as an analogue for past halite depositional periods as recorded in the drill core the halite intervals provide a record of facies characterizing a deep water evaporitic environment the halite layers consist mainly of two types of crystals small cumulate crystals containing halite rafts which indicate precipitation from the surface brine of the lake epilimnion and bottom growth usually large halite crystals that precipitated on the lake floor hypolimnion the layers of small halite crystals formed during drier periods as compared to the bottom growth crystals the bottom growth halite crystals contain variable quantities of detritus and show mild dissolution structures at the contact between the mud and the halite crystals these two main types of halite in combination with muds and gypsum comprise seven categories of salt facies that reflect the hydrological conditions dry to wet and that display a cyclic decadal to millennial pattern along the sampled core intervals frequent alternation of these two salt crystal types suggests seasonal changes whereby the small cumulate crystals were formed during the summer and the bottom growth crystals were formed during the winter when the surface temperatures of the lake were low and the surface water was less saline and less likely to be saturated with respect to halite comparison of the last interglacial halite with the modern halite facies together with the absence of significant dissolution features within the halite and the cyclic nature of the facies indicates that the lake was continuously deep 100 m during the last 200 k y

criteria for the recognition of acid precipitated halite modern acid and neutral saline lakes in western australia are an excellent natural laboratory for testing how ph affects halite and for developing criteria for distinguishing past acid saline waters from past neutral saline waters in the rock record this study characterizes and compares physical chemical and biological features in halite precipitated from acid ph 1ae 7t o 4 ae2 and neutral ph 6ae 8t o 7 ae3 saline lakes in southern western australia supplemental data include synthetic halite grown from acid and neutral saline solutions as well as halite deposited in permian acid lakes although physical processes of halite growth are not affected by ph there are differences in the colour accessory minerals fluid inclusions and microfossils between acid and neutral halites acid lake halite commonly is yellow or orange in colour neutral lake halites examined in this study are always snow white acid halites tend to contain abundant sulphate and iron oxide minerals both as solid inclusions and as solids within fluid inclusions neutral halites contain little if any sulphates and no iron oxides acid fluid inclusion freezing melting behaviours include characteristics that differ from neutral fluid inclusion behaviours such as lower eutectic temperatures higher and wider temperature range of hydrohalite rims with a definable fuzzy border and more complex metastable phases acid halite contains hairy blobs clusters of bacterial archaeal fungal remains and sulphate crystals which are not found in halite from neutral lakes this distinct assemblage of features characteristic of modern acid lake halites may serve as informal criteria for the recognition of past acid lake evaporites in the rock record

chemistry of modern soils as a guide to interpreting precambrian paleosols precambrian paleosols are potentially one of our best sources of information about the composition of the atmosphere early in earth s history to be used this way however an alteration profile must be shown to be an in situ product of vadose processes data from modern soils show that the ratios of less mobile elements such as zr ti and al can be used as a preliminary screen to test for the in situ nature of a profile if the ti zr ratio departs from that of the host rock by more than 40 or the ti al ratio departs by more than 50 for moderate degrees of weathering then a significant allochthonous contribution to the profile is indicated this technique correctly separates in place from allochthonous horizons when applied to independent data from two modern profiles a review of published precambrian profiles identifies two often cited examples denison and pronto as suspect based on these criteria in the interpretation of paleoatmospheres it is also necessary to show that fe is controlled not b

molybdenum isotopes in late archean carbonate rocks implications for early earth oxygenation abstract we present carbonate mo isotope data of the 2 64 2 5 ga old ghaap group transvaal supergroup south africa to contribute to the debate on early earth oxygenation mo fractionation in carbonates has just recently been introduced as a potential new proxy for ocean redox chemistry and it was suggested that under favorable conditions non skeletal carbonates closely monitor the ambient seawater 98 95 mo composition the record presented here is characterized by three phases of moderately to strongly fractionated 98 95 mo with values of up to 1 6 interrupted by two shifts towards detrital levels this near continuous presence of heavy 98 95 mo suggests a quasi permanent availability of free atmospheric o 2 because fractionation relative to the continental background signature occurs exclusively when mo is present as dissolved molybdate ions moo 4 2 we compare our carbonate data to a previously published black shale mo record on samples from the same drill core the general interpretation of both records is identical a rise in o 2 preceded the commonly accepted transition to a consistently oxygenated atmosphere by 150 ma however in the ghaap group carbonates fractionated mo is found at a time when the coeval black shales still indicate detrital sedimentation a combination of detritus admixture and or redox controlled mo isotope fractionation during shale formation in suboxic to anoxic waters is suggested as cause for a period characterized by a persistent offset between lighter shale and heavier carbonate 98 95 mo the apparent offset can then be attributed to the different geochemical behavior of the two archives with respect to the local depositional conditions redox vs non redox dependent such changes in the sedimentary environment might also explain why the carbonates do not reproduce rapid fluctuations found throughout the shale record but show a continuous signature with scarce outliers thus by means of the combined archives the conspicuous 98 95 mo scatter found in the shale record could be attributed to variable depositional conditions during its formation rather than global oxic anoxic fluctuations simultaneously the carbonates provide a better approximation of the long term 98 95 mo seawater evolution this study introduces the mo isotopic composition of carbonates as a promising new tool for paleo redox studies in particular when combined with black shales

microfossils and possible microfossils from the early archean onverwacht group barberton mountain land south africa there is widespread textural evidence for microbial activity in the cherts of the early archean onverwacht group layers with fine carbonaceous laminations resembling fossil microbial mats are abundant in the cherty metasediments of the predominantly basaltic hooggenoeg and kromberg formations in rare cases filamentous microfossils are associated with the laminae the morphologies of the fossils as well as the texture of the encompassing laminae suggest an affinity to modern mat dwelling cyanobacteria or bacteria a variety of spheroidal and ellipsoidal structures present in cherts of the hooggenoeg and kromberg formations resemble modern coccoidal bacteria and bacterial structures including spores the development of spores may have enabled early microorganisms to survive the relatively harsh surficial conditions including the effects of very large meteorite impacts on the young earth

the record of temperature wind velocity and air humidity in the δd and δ18o of water inclusions in synthetic and messinian halites abstract deuterium and oxygen isotope fractionations between liquid and vapor water were experimentally determined during evaporation of a nacl solution 35 g l 1 as a function of water temperature and wind velocity in the case of a null wind velocity slopes of d 18o trajectories of residual waters hyperbolically decrease with increasing water temperatures in the range 23 47 c for wind velocities ranging from 0 8 to 2 2 m s 1 slopes of the d 18o trajectories linearly increase with increasing wind velocity at a given water temperature these experimental results can be modeled by using rayleigh distillation equations taking into account wind related kinetics effects deuterium and oxygen isotope compositions of water inclusions trapped by the precipitated halite crystals were determined by micro equilibration techniques these isotopic compositions accurately reflect those of the surrounding residual waters during halite growth isotopic compositions of water inclusions in twenty natural halites from the messinian realmonte mine in sicily suggest precipitation temperatures of 34 4 10 c that match the homogenization temperatures obtained by microthermometry median 34 5 c the similarity between the measured and experimental slopes of the d 18o evaporation trajectories suggests that the effect of wind was negligible during the genesis of these halite deposits hydrogen and oxygen isotope compositions of water inclusions from realmonte halite also define a linear trend whose extrapolation until intersection with the mediterranean meteoric water line allows the characterization of the water source with d and 18o values of 70 10 and 11 5 1 5 respectively these results reveal that the huge amounts of salts deposited in sicily result from the evaporation of seawater mixed with a dominant fraction 50 of meteoric waters most likely deriving from alpine fluvial discharge

initiation of leaking earth an ultimate trigger of the cambrian explosion abstract for life to have dramatically evolved and diversified during the so called cambrian explosion there must have been significant changes in the environmental conditions of earth a rapid increase in atmospheric oxygen which has been discussed as the key factor in the evolution of life cannot by itself explain such an explosion since life requires more than oxygen to flourish let alone survive the supply of nutrients must have played a more critical role in the explosion including an increase in phosphorus p and potassium k which are key elements for metabolisms to function so what happened at the onset of the cambrian to bring about changes in environmental conditions and nutrient supply and ultimately evolution of life an ultimate trigger for the cambrian explosion is proposed here the geotherm along subduction zones of a cooling earth finally became cool enough around 600 ma to allow slabs to be hydrated the subduction of these hydrated slabs transferred voluminous water from the ocean to the mantle resulting in a lowering of the sea level and an associated exceptional exposure of nutrient enriched continental crust along with an increase in atmospheric oxygen this loss of water at the surface of the earth and an associated increase in exposed landmass is referred to here as leaking earth vast amounts of nutrients began to be carried through weathering erosion and transport of the landmass rock fragments of the landmass would break down into ions during transport to the ocean through river providing life forms prokaryote sufficient nutrients to live and evolve also plume driven dome up beneath the continental crusts broadened the surface area providing a supply of nutrients an order magnitude greater than that produced through uplift of mountains by continental collision simultaneously atmospheric oxygen began to increase rapidly due to the burial of dead organic matter by enhanced sedimentation from the emergence of a greater landmass which ultimately inhibited oxidation of organic matter hence oxygen began to accumulate in the atmosphere which when coupled with a continuous supply of nutrients resulted in an explosion of life including an increase in the size an enhanced oxygen supply in the atmosphere resulted in the formation of an ozone layer providing life a shield from the uv radiation of the sun this enabled life to invade the land in addition to a change in the supply of nutrients related to a leaking earth the evolution of life was accelerated through mass extinction events such as observed during snowball earth possibly related to a starburst in our galaxy as well as mutation in the genome due to radiogenic elements sourced from carbonatite magma atomic bomb magma in rift valley there are two requirements to find a habitable planet 1 the initial mass of an ocean and 2 the size of a planet these two conditions determine the history of a planet including planetary tectonics and the birth of life this newfound perspective which includes the importance of a leaking planet provides a dawn of new planetary science and astrobiology

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

permian chronostratigraphy in kansas correlations between the type permian system of russia and north american strata have been difficult for decades because of biostratigraphic and nomenclatural confusion consequently a standard permian section was established in west texas that is widely accepted throughout north america series of the north american standard section are in ascending order wolfcampian leonardian guadalupian and ochoan this nomenclature was adopted for usage in kansas in 1951 but was later abandoned in favor of local terminology however direct biostratigraphic correlations between kansas and the west texas standard section have now been firmly established and local chronostratigraphic names i e big blue lyon geary cimarron and custer have not been widely accepted the kansas geological survey has now readopted usage of the wolfcampian series for rocks of the admire council grove and chase groups the leonardian series for rocks of the summer and nippewalla groups and the guadalupian series for rocks of the whitehorse day creek and big basin formations the wolfcampian series in kansas and elsewhere in north america contains post virgilian latest carboniferous strata that predate the classical permian system of the russian type section consequently the pennsylvanian permian boundary will probably have to be raised stratigraphically to conform to global usage

late pleistocene detrital sediment yield of the jura glacier france abstract measures of present day glacial erosion vary widely with the technique employed this paper quantifies the glacial material trapped in a proglacial lake during the wurm glacial period the combe d ain site was occupied by a meltwater lake where all the detrital material entering it from the jura glacier accumulated sediment yield is computed from three factors 1 the size of the sediment source area 2 the length of time the system operated and 3 the volume of sediment trapped the sediment budget of the lake system suggests a detrital sediment yield of 4400 1700 metric tons per square kilometer and per calendar year this represents a denudation rate of 1 6 0 6 mm per year illustrating that mechanical erosion by the jura glacier is more intensive than other processes of erosion

displacive halite hoppers from the dead sea some implications for ancient evaporite deposits abstract large hopper shaped halite cubes up to 10 cm on a side grow displacively within holocene sediments near the southern end of the dead sea under conditions of high temperatures ionic concentrations and rapid rates of crystallization two theories of formation are presented downward diffusion of ions versus upward diffusion and evaporative pumping both alternatives are considered possible and the correct choice probably depends upon the location of the sediments at the time of precipitation whether subaqueous or subaerial a choice indeterminate at present because of human disturbance to the sediments prior to collection displacively formed halite crystals similar in morphology to the dead sea cubes are common in evaporite bearing carbonate rocks of many regions such as the salina fm u silurian michigan basin the kirkham mudstone u triassic cumbria england and the u miocene gessoso solfifera fm of sicily these are believed to have formed under conditions analogous to those in the present dead sea these observations taken together with those of other authors may now be used for the facies interpretation of ancient halite deposits

criteria for the recognition of salt pan evaporites layered evaporites can accumulate in 1 ephemeral saline pans 2 shallow perennial lagoons or lakes and 3 deep perennial basins criteria for recognizing evaporites deposited in these settings have yet to be explicitly formulated the characteristics of the ephemeral saline pan setting have been determined by examining eight holocene halite dominated pans salt pans and their deposits marine and non marine from the u s mexico egypt and bolivia these salt pans are typified by alternating periods of flooding resulting in a temporary brackish lake evaporative concentration when the lake becomes saline and desiccation which produces a dry pan fed only by groundwater the resulting deposits consist of alternating layers millimetres to decimetres of halite and mud the layers of halite are characterized by 1 vertical and horizontal cavities rounded crystal edges and horizontal truncation surfaces due to dissolution during flooding 2 vertical chevrons and cornets grown syntaxially on the bottom during the saline lake stage 3 halite cements overgrowths and euhedral cavity linings and disruption of layering into metre scale polygons produced during the desiccation stage the muddy interbeds are characterized by displacive growth of halite during the desiccation stage immediately below the surface of the pan the halite layers are matured by repeated episodes of dissolution and diagenetic crystal growth this results in porous crusts with patches of chevron and cornet crystals truncated by dissolution clear diagenetic halite cement and internal sediment these layers of mature halite closely resemble the patchy cloudy and clear textures of ancient halite deposits holocene salt pans are known to cover thousands of square kilometres and cap halite deposits hundreds of metres thick so they are realistic models for ancient evaporites in scale e g permian salado formation of new mexico texas which preserves many primary salt pan features

precambrian age of the boston basin new evidence from microfossils a vendian late proterozoic z age has been determined for the boston basin by comparison of a microflora from the cambridge argillite with other late precambrian assemblages the microfossils which include bavlinella cf faveolata are preserved as petrifactions in pyrite this age designation for the sedimentary rocks of the boston basin should allow for the reinterpretation of the structure of the basin and its regional correlations

ediacaran seawater temperature evidence from inclusions of sinian halite abstract seawater temperatures throughout earth s history have been suggested to illustrate a long term cooling trend from nearly 70 c at 3500 ma to around 20 c at 800 ma the terminal neoproterozoic prior to the cambrian explosion is a key interval in evolutionary history as complex multicellularity appeared with the advent of the ediacara fauna these organisms were likely the first that required higher levels of atmospheric and dissolved marine oxygen for their sustainability it is known that most modern macroinvertebrates are intolerant of temperatures in excess of 45 c perhaps more importantly these high seawater temperatures limit the potential of dissolved oxygen and therefore become an integral part of this evolutionary story previously our understanding of seawater temperature during the terminal neoproterozoic comes only from 18 o 16 o and 30 si 28 si ratios ascertained from a limited number of cherts isotopic ratio methods for assessing seawater temperatures are inherently indirect and have a wide range of oscillation however maximum homogenization temperatures th max of primary fluid inclusions in halite provide a direct means of assessing brine temperature and have been shown to correlate well with average maximum air temperatures the oldest halites date to the neoproterozoic lower paleozoic 700 500 ma and ediacaran representatives can be found in sichuan province china which do preserve primary fluid inclusions for analysis via cooling nucleation methods we utilized halite samples from the changning 2 well correlative to the dengying formation 551 542 ma to provide a direct assessment of terminal neoproterozoic seawater temperature our measurements indicate that seawater temperatures where these halites formed are highly similar to tropical phanerozoic seawater temperature estimates from compiled paleotemperature data the decline in seawater temperatures over the course of the proterozoic accompanied by the reduction of seawater salinity with the sequestration of salt in massive halite deposits in the neoproterozoic allowed the ocean system to accumulate more dissolved oxygen and potentially paved the way for the evolutionary innovation of complex multicellularity

paradigm shift in determining neoproterozoic atmospheric oxygen acknowledgments we thank the geological survey of australia for permission to sample the empress 1a and lancer 1 cores the natural sciences and engineering research council of canada for financial support grant 7961 15 of u brand and the national natural science foundation of china for support of f meng and p ni grants 41473039 and 4151101015 we thank m lozon brock university for drafting and constructing the figures we thank the editor brendan murphy as well as three reviewers steve kesler erik sperling and an anonymous reviewer for improving the manuscript into its final form

continental erosion and large scale relief a worldwide investigation of continental erosion is carried out by the study of large drainage basins on the basis of hydrological data environmental factors and basin relief distribution inside each basin mean geochemical and mechanical denudation rates are defined a multicorrelation analysis shows that the mechanical denudation rates ds are uncorrelated with environmental factors and correlated with mean basin elevation h while chemical denudation rates dd are insensitive to relief but correlated with mean annual precipitation furthermore two linear relationships between h and ds are detected 1 ds m 10 yr 419 10 6 h m 0 245 with v explained variance 95 1 this law concerns basins related to orogenies younger than 250 ma the negative intercept is interpreted as a continental sedimentation rate of 245 m m y an alternative model in which one invokes a critical elevation separating erosion from sedimentation is equally successful and leads to lower sedimentation rates 60 110 m m y for both models one derives from the slope of the adjustments erosion time constants on the order of 2 5 m y 2 ds m 10 yr 61 10 6 h m with v 86 5 this law concerns basins related to older orogenies the null intercept suggests the lack of continental storage because of the more important dispersion of the data the erosion time constant is calculated separately for each basin it ranges from 15 to 360 m y the tectonic implications of these results are discussed in particular the short time constant 2 5 m y agrees with orogenic uplift rates on the order of 1 mm yr observed in active mountain chains

origin of polyhalite deposits in the zechstein upper permian zdrada platform northern poland polyhalite deposits in the zechstein upper permian of northern poland occur in the lower werra anhydrite in the zdrada sulphate platform the polyhalite appears to be a very early replacement of anhydrite the replacement was caused by the halite precipitating brines which contained potassium and magnesium ions the formation of polyhalite was preceded by the syndepositional anhydritization of the original gypsum deposit which has often preserved its primary textures this anhydritization on the platform and its slopes was a reaction of the precipitated gypsum in a hydrologically open evaporite basin with brines of salt basins adjacent to the sulphate platform these brines when nearly saturated with respect to halite and potassium and magnesium rich reacted with anhydrite to precipitate polyhalite along the slopes of the zdrada platform the oxygen and sulphur isotopic compositions of sulphate evaporites indicate that marine solutions were the only source of sulphate ions supplied to the zechstein basin and that anhydrite was transformed to polyhalite by reaction with marine brines more concentrated than those that precipitated precursor calcium sulphate minerals

chemical and boron isotope compositions of non marine brines from the qaidam basin qinghai china the general chemistry and boron isotope composition were investigated in fresh waters and hypersaline brines from the qaidam basin northern qinghai xizang tibet plateau china this basin is a large tectonically active system isolated from the ocean and composed of thick clastic and evaporite sediments the modern playas are subject to intense evaporation and are characterized by hypersaline brines as well as potash and borate evaporites the chemical composition of the dissolved solutes in the modern brines and waters reveals three main sources 1 inflow of hot springs enriched in sodium sulphate and boron evaporation of these waters leads to a high na cl ratio 1 a na cl so4 brine and an evaporite mineral assemblage of halite mirabilite borate lakes daqaidam and xiaoqaidam 2 inflow surface river waters which are modified by preferential dissolution of halite and potassium and magnesium salts characterized by a na mg cl solute type with low na cl 1 brcl licl and bcl ratios and 3 ca chloridic subsurface brines which are controlled by both salt dissolution and dolomitization processes evaporation and salt crystallization of mixtures of the latter two types leads to a marine like brine e g na mg cl type nacl ratio 1 and mineral assemblages similar to that predicted for progressive evaporation of seawater e g qarhan playa halite sylvite carnallite bischofite the 11 b values of the input waters to the qaidam basin range of 0 7 to 10 9 vs nbs 951 and brines from salt lakes 0 5 to 15 0 are similar to those of associated granitic rocks 11b 2 3 to 3 7 n 3 and hence indicate the non marine origin of these fluids the highest 11b values are associated with fluids with low bli ratios indicating selective removal of elemental boron and 10b by adsorption onto clay minerals the magnitude of 11b enrichment due to adsorption is 15 20 and thus non marine brines are well distinguished from marine derived brines 11b of 39 to 59 preserving the large isotopic difference 40 of their source waters it is proposed to use this distinctive isotopic signature for tracing the origin of ancient evaporite environments

the so called paleophytic mesophytic transition in equatorial pangea multiple biomes and vegetational tracking of climate change through geological time abstract the paleophytic mesophytic and cenophytic were originally conceptualized as chronostratigraphic intervals not specific floras and were used principally in that way for about 100 years they supposedly reflected massive irreversible biotic changes on land that were thought to have happened about half a geological period prior to the changes in marine faunas that mark the more traditional geological era boundaries the terms were applied initially only to terrestrial rocks from the euramerican portions of equatorial pangea especially parts of central europe where the boundary between the paleophytic and mesophytic the eras of interest here was placed at the top of the german rotliegends more recently the terms have been coopted to describe vegetation types not chronostratigraphic units even to the point where specific linnean ordinal or class level clades evolutionary lineages of plants have been attributed solely to one vegetation type or the other at a global level furthermore the paleophytic mesophytic transition has been recognized in the largely taxonomically distinct vegetation types of temperate as well as the equatorial paleolatitudes the result of this conceptual coopting of terms that already were of questionable value is a blurring of the concepts almost to the point of meaninglessness a reading of the literature indicates confusion in terms of what represents the paleophytic flora vs the mesophytic flora the botanical basis for the floras and the taxonomic scale at which they can be recognized the geographic pattern and temporal correlation of the supposed transition and the evolutionary and ecological significance of the vegetational changes these terms supposedly capture we propose that these terms be completely and utterly abandoned as confusing and worse yet misleading evidence suggests that paleozoic vegetation tracked climate which should not come as a surprise in light of what is known of plant dynamics in the holocene and recent furthermore the evidence for a global paleophytic vs mesophytic vegetation is simply unsubstantiated by the fossil record rather there appears to have been a complex of global species pools reflecting climate at many spatio temporal scales the vegetational changes occurring in the late paleozoic thus can be understood best when examined as spatial temporal changes in biome scale species pools responding to major global climate changes locally and regionally manifested

choosing the best ancient analogue for projected future temperatures a case using data from fluid inclusions of middle late eocene halites abstract after the paleocene eocene thermal maximum petm global temperature and co2 levels decreased concurrently in the middle late eocene using different approaches estimated co2 levels of the middle late eocene are very similar to the 1000 ppm co2 level projected for the next 100 years as a result of increasing greenhouse gas concentrations the average global temperature is projected to increase from 1 4 to 5 8 c by 2100 relative to 2001 levels thus the middle late eocene may be the best ancient analogue for a future with increased temperatures due to burning of fossil fuels in order to explore the sensitivity range of global annual temperature with respect to co2 concentration exact atmospheric co2 concentrations and air temperatures of ancient analogs must be known previous palynological studies provide only indirect estimates of temperature however the homogenization temperature of fluid inclusions in halites obtained by the cooling nucleation method can provide the exact temperature of saline lake water which is similar to overlying air temperature in shallow lakes in this paper we measured the range of homogenization temperatures from 5 8 to 43 3 c of fluid inclusions in middle late eocene halites of the yunying depression central china the maximum homogenization temperature of fluid inclusions thmax in these middle late eocene halites is 4 6 c higher than the modern extreme highest temperature 38 7 c recorded for this area

expansion and retreat of the jura ice sheet france during the last glacial maximum in continental environments while there is no uninterrupted record of glaciation glacier activity can be reconstructed from the nature and geometry of sediments trapped by lake filling examination of the combe d ain lake filling provides insight into the history of the jura mountains during the last glacial maximum lgm from the evidence of outcrops borehole cores and seismic reflection profiles of the lake filling we show that glaciation was marked by three stages of stabilization then recessional moraines marked five episodes of stabilization in the course of glacial retreat comparison with b 18 o data from ice cores of greenland makes possible to date the last glacial maximum at 25 500 22 000 cal bc and

late jurassic paleoclimate of central africa abstract paleopedology and geochemical analysis of upper jurassic deposits in the stanleyville group of central africa indicate harsh late jurassic paleoclimates in the interior of gondwana subsurface samples collected from the samba borehole near the center of the congo basin show only weak morphological evidence of pedogenesis but are characterized by an abundance of shrink swell vertic features and rare calcium carbonate nodules indicating seasonal variations in moisture availability and net soil moisture deficiency respectively x ray diffraction analysis of paleosol matrix material reveals the presence of analcime and the clay mineral palygorskite strong indicators of hot arid climatic conditions the 18 o and d values of clay minerals from paleosol profiles range from 22 3 to 25 4 and 44 4 to 39 6 smow respectively and correspond to crystallization temperatures between 25 c and 40 c these crystallization temperatures compare favorably with austral summer surface temperature estimates for central africa that result from late jurassic global circulation models calculations of soil co 2 production using the 13 c values of pedogenic carbonates and plant derived organic matter produce lower co 2 production estimates for the stanleyville group relative to the roughly contemporary morrison formation of the western u s these low soil co 2 production estimates provide further support for arid late jurassic climate conditions in the congo basin the paleoclimatic conditions inferred here from the stanleyville group are similar to those reconstructed from other upper jurassic african continental localities between 5 s and 20 s paleolatitude however penecontemporaneous terrestrial coastal sites within this latitudinal belt of gondwana retain evidence of generally wetter conditions suggesting that those regions may have received more rainfall than the continental interior the paleoclimatic setting reconstructed here from geologic indicators and geochemical proxies suggests that general circulation models accurately predict unique paleoenvironmental conditions that lack modern analogs

holocene denudation rates from the superhumid southernmost chilean patagonian andes 53 s deduced from lake sediment budgets abstract holocene denudation rates and their regional variations in the superhumid and temperate climate of the southernmost patagonian andes are poorly surveyed therefore we have investigated denudation in five small lake catchments 0 11 1 62 km 2 across a precipitation gradient from 600 to 9000 mm yr 1 in southernmost chile at 53 s variations in denudation rates can be defined most precisely by using small catchments and short time spans holocene thus can be related to variable bedrock types vegetation cover elevation and climate minimum physical denudation rates were determined from sediment budgets based on sediment echosounder data and physical properties of sediment cores the holocene denudation rates vary from 0 08 mm kyr 1 in the highly elevated bare granitic rock catchments to 9 01 mm kyr 1 in the low and vegetated catchments with a basement of sedimentary rocks these values are comparable with those from similar areas in norway sweden and nw iceland the high annual precipitation in the study area has only a minor effect on denudation enhanced geomorphic activity during paraglacial conditions caused a faster denudation after the glacier retreat until either the clastic glacial detritus was removed or the catchment was covered with vegetation chemical comparisons between basement rocks and lake sediments indicate a pronounced chemical denudation in catchments with peaty soils and low soil water ph values of 3 to 5 the holocene surface lowering rates are on average 200 fold lower than cenozoic surface lowering rates calculated from fission track data for the southern andes this discrepancy can be explained by significantly higher erosion rates during glacial periods

clues from fluid inclusions the reconstruction of past conditions on earth involves a multitude of disciplines and techniques in his perspective goldstein highlights the potential of fluid inclusions in small halite or calcite crystals formed for example when marine waters evaporate such inclusions can provide information for example about seawater composition paleoclimatic conditions and paleobiology for example lowenstein et al have used inclusions in halite crystals to show that the chemical composition of ancient seawater was different from that of modern seawater and that plate tectonics probably controlled much of this variation

late permian global coal hiatus linked to 13c depleted co2 flux into the atmosphere during the final consolidation of pangea at a time when all continents were finally arrayed in their pangea supercontinental configuration 250 50 ma earth9s stratigraphy records a global and very abrupt coal discontinuity from the tartarian stage of the late permian to the middle triassic reduced coal productivity and or preservation overlaps with a period of anomalous oceanic and atmospheric decrease in 13 c as recorded in marine carbonates and organic matter and terrestrial plant and animal fossils from the northern and southern hemispheres during the same short period the peripheral margin of the entire supercontinent pangea except for the southern shores of tethys was effectively under compressive stress this unique tectonic state caused deformation and uplift of coal bearing foreland basins and oxidation of pangea9s vast peat deposits the latter resulted in a rapid massive 13 c depleted co 2 flux into the atmosphere which in turn may have forced global warming

the major composition of a middle late eocene salt lake in the yunying depression of jianghan basin of middle china based on analyses of fluid inclusions in halite abstract during the cretaceous tertiary transition in eastern china abundant halites formed in non marine areas many continental salt deposits from inland salt lakes were formed in eastern china in faulted basins as a result of the northward movement and collision of the indo china plate with the eurasian plate including the bohai gulf basin however a marine transgression versus a non marine origin of these evaporites remains to be determined primary fluid inclusions trapped in halite deposits can directly record the composition of evaporated seawater or salt lake water such as those in the cretaceous halite in the khorat plateau laos and thailand area can resolve the origins of the evaporate deposits recent fluid inclusions data in the khorat plateau coincide with the predicted secular variation of seawater and are comparable to other fluid inclusions in cretaceous marine halite indicating these fluid inclusions are directly related to a marine transgression our analyses in this study shows that the average k mg2 and so 4 2 contents are 8 8 5 0 and 6 8 g l respectively in the primary fluid inclusions in halite of middle late eocene from the yunying depression of china these numbers are much less than those in the contemporary spanish primary fluid inclusions in halite precipitated from seawater 16 4 36 3 and 12 5 g l for k mg2 and so 4 2 respectively furthermore br contents of all fluid inclusion samples in halite from the yunying depression are lower than 2 ppm vs 55 58 ppm at the base of spanish contemporary marine halite and their 37cl values range from 0 11 to 2 94 vs 0 09 to 0 24 in sylvite of spanish deposit indicating that the compositions of the middle late eocene brines trapped in halite in the yunying depression of china are very different from those derived from the contemporary seawater and are considered to be resulted from evaporation of an inland saline lake water with little influence of seawater

extremely high temperatures and paleoclimate trends recorded in permian ephemeral lake halite although the late paleozoic deglaciation is arguably one of the best deep time analogs for current and predicted climate change quantitative paleotemperature data from this interval are generally lacking we reconstruct extreme paleoweather conditions and paleoclimate changes from permian nippewalla group probably uppermost leonardian kungurian north america ephemeral lake halite by using fluid inclusion homogenization temperatures to directly measure the water temperature when the halite precipitated in these depositional settings this is an excellent air temperature proxy extremely high temperatures to 73 c and large diurnal temperature ranges are evidenced in the lower nippewalla group suggesting conditions more extreme than anywhere on earth today in contrast the upper nippewalla group was cooler maximum temperature was 43 c and diurnal temperature ranges were smaller though even these conditions are similar to modern extremely hot environments comparison to prior studies suggests that these results may be indicative of regional patterns this study represents the first pre quaternary high resolution quantitative data set of extreme paleoweather and possible paleoclimate trends from fluid inclusions in halite and provides new insight into climate change during the late paleozoic deglaciation

sediment supply to the continental shelf by the major rivers of china the yalu luan the yellow changjiang and pearl rivers discharge 90 of china s total annual input of 20 14 10 8 t of sediment to the sea this huge volume of sediment is deposited in the river mouths and in the vicinity of the inner shelves in the form of deltas or submarine sandy ridges depending upon the dominant processes or dynamics of the area even though the continental shelves of the china seas were coastal plains during the late pleistocene modern river sediments rarely extend to the outer shelves except in response to changes in sea level

variations in sediment yield from the upper doubs river carbonate watershed jura france since the late glacial period abstract the upper doubs river valley is a 910 km2watershed feeding into lake chaillexon the lake was formed by a natural rockfall at the end of the bolling chronozone around 14 250 cal yr b p and since then has trapped material eroded from the watershed the filling process and variations in sediment yield have been investigated by mechanical coring seismic surveys and electric soundings the detrital sediment yield of the upstream watershed can be calculated by quantifying the sedimentary stocks for each climatic stage of the late glacial period and holocene epoch and estimating the lake s entrapment capacity this enables us to determine the intensity of the erosion processes in relation to climate and environmental factors the bolling allerod interstade produced the greatest yields with mean values of 19 500 metric tons per calendar year t yr the younger dryas chronozone saw a sharp fall 8900 t yr that continued into the preboreal 2100 t yr clastic supply increased during the boreal 4500 t yr before declining again in the early atlantic 2400 t yr since then yields have risen from 4500 t yr in the late atlantic to 6800 t yr in the subboreal and 11 100 t yr in the subatlantic comparison of quantitative data with the qualitative analysis of the deposits and with the paleohydrologic curve of the watershed based on level fluctuations in lakes around chaillexon shows that climate was the controlling factor of sediment yield until the late atlantic from the late atlantic subboreal around 5400 cal yr b p 470014c yr b p and especially from the end of the subboreal chronozone and during the subatlantic chronozone 2770 cal yr b p 270014c yr b p present climatic constraints have been compounded by human activity related to forest clearing and land use

geology and geochemistry of paleosols developed on the hekpoort basalt pretoria group south africa the hekpoort paleosols comprise a regional paleoweathering horizon developed on 2 224 0 021 ga basaltic andesite lavas at the top of the hekpoort formation of the pretoria group transvaal supergroup south africa in five separate profiles from outcrops along road cuts near waterval onder and the daspoort tunnel and in three drill cores from the bank break area bb3 bb8 and bb14 the top of the paleosol is a sericite rich zone the sericite zone grades downward into a chlorite rich zone in core bb8 and in the road cut at the daspoort tunnel we sampled the underlying or parent basaltic andesite into which the chlorite zone grades we did not obtain samples of the parent material at waterval onder and in cores bb3 and bb14 but chemical analyses indicate that the chlorite and sericite zones in these profiles derive from underlying lavas similar to the ones we sampled in core bb8 and at the daspoort tunnel the presence of apparent rip up clasts of the paleosol in the overlying ironstones of the strubenkop formation in the cores from bank break makes it very unlikely that most of the alteration was a result of interactions with hydrothermal fluids desiccation cracks at the top of the paleosol that were filled with sand during the deposition of the overlying sediments at waterval onder point to a subaerial weathering origin very little if any al ti zr v or cr moved a discernible distance during weathering of any of the five profiles the vertical distribution of fe mg mn ni and co indicates that these elements were largely removed from the top of the soil during weathering the overall abundance of these elements in each of the profiles indicates that a significant fraction of the complement lost from the top subsequently reprecipitated in the lower portion of the soil as constituents of an fe 2 rich smectite the loss of fe from the top of the soil during weathering of the hekpoort paleosols indicates that atmospheric p o 2 was less than 8 x 10 4 atm about 2 22 ga fe 2 rich smectite should only precipitate during soil formation if atmospheric p co 2 is less than or equal to 2 x 10 2 atm rye kuo and holland 1995 ca and na were largely lost during weathering some na was apparently added to the sericite zone in cores bb3 bb8 and bb14 after weathering all five profiles are enriched in k and rb and most are enriched in ba the distribution of these elements indicates that they all were added during post weathering hydrothermal metasomatism rb sr analysis of the paleosol at the daspoort tunnel indicates that metasomatism last affected that profile 1 925 0 032 ga macfarlane and holland 1991

sedimentology and evaporite genesis in a holocene continental sabkha playa basin bristol dry lake california bristol dry lake a 155 km2 continental sabkha playa basin in the mojave desert of south eastern california is filled with at least 300 m of interbedded terrigenous clastics gypsum anhydrite and halite evaporite facies conform approximately to a bull s eye pattern with gypsum and anhydrite surrounding a basin centre accumulation of halite transects through bristol dry lake from the alluvial fan to the centre of the playa reveal 1 crudely bedded alluvial fan clastics interfingering with 2 playa margin sand flat and wadi sand and silt followed by 3 gypsum anhydrite chaotic mud halite and clay of the saline mud flat and 4 salt pan halite beds terrigenous clastics were deposited in bristol dry lake by sheetflow and by suspension settling from ponded floodwater some sediment has been reworked by aeolian processes to form barchan dunes around the playa margin thin nodular like beds of anhydrite and several types of gypsum occur across most of the playa giant hopper shaped halite cubes are suspended in saline mud flat facies suggesting that they grew displacively in brine soaked sediment just below the surface thick beds 4 m of halite in the playa centre may have formed through a complex alternating history of subaqueous and intrasedimentary precipitation under the influence of periodic floods intense evaporation and brine level lowering and capillary discharge of brines the stratigraphy in the playa centre is cyclic an ideal cycle consists of 1 chaotic mud halite at the base overlain by 2 green to red clay with abundant giant hoppers and at the top 3 red clay gypsum and anhydrite with flaser to wavy bedded sand and silt this type of cycle probably records a gradual progradation of mud flat facies over salt pans bristol dry lake sediments are nearly identical to some of the permian evaporites of the permian basin region u s a and they can serve as modern analogues for ancient sabkha facies analysis

a paleoweathering profile from griqualand west south africa evidence for a dramatic rise in atmospheric oxygen between 2 2 and 1 9 bybp a core drilled near wolhaarkop in griqualand west south africa intersected highly oxidized kuruman iron formation below red beds of the gamagara formation the lateral equivalents of the kuruman iron formation in this drill hole consist largely of siderite ankerite magnetite greenalite and quartz the oxidation of the kuruman iron formation in wol 2 occurred almost certainly during weathering prior to the deposition of the gamagara formation the date of this weathering episode is bracketed between about 2 2 and 1 9 bybp by the age of the ongeluk lavas in the transvaal sequence below the unconformity and by the age of the hartley lavas in the olifantshoek group above the unconformity the ratio of iron to sio2 in the several facies of the weathered kuruman iron formation in wol 2 is nearly the same as that in their unweathered equivalents since sio2 loss during weathering was almost certainly minor the similarity of the fe sio2 ratio in the weathered and unweathered bif indicates that nearly all the feo in the kuruman iron formation was oxidized and retained as feo3 during weathering such a high degree of iron retention is best explained by an o2 content of the atmosphere or 0 03 atm at the time of weathering such an o2 pressure is very much greater than that suggested by the composition of paleosols developed on basalt or 2 2 bybp but is consistent with the highly oxidized nature of the 1 85 by flin flon paleosol the new data suggest that po2 rose dramatically from about 1 percent pal present atmospheric level to or 15 percent pal between 2 2 and 1 9 bybp

carbon and sulfur isotopic compositions of organic carbon and pyrite in sediments from the transvaal supergroup south africa abstract sedimentary organic matter and pyrite from parts of the lower transvaal supergroup and few samples from the olifantshoek group have been studied for their carbon and sulfur isotopic compositions respectively carbon isotopic compositions for minimally altered organic matter range from 43 to 31 sulfur isotope values for sedimentary pyrite display values between 1 3 to 23 6 results from this and previously published work are being interpreted with respect to past biochemical pathways carbon isotope data indicate autotrophic carbon fixation as the process of primary production in addition products of secondary biological reworking contributed to the total organic carbon content sulfur isotope data indicate bacterial sulfate reduction as the main process however changes in sulfate availability and or the rate of sulfate reduction may have caused the observed range in isotopic compositions

sediment and basalt hosted regoliths in the huronian supergroup role of parent lithology in middle precambrian weathering profiles weathering profiles developed side by side on sandstone and a mafic dike provide an unusual opportunity to examine the role of parent rock bulk composition in the chemical evolution of middle precambrian regoliths because the profiles are adjacent to one another differences in topography can be eliminated in accounting for differences in the chemical evolution of the two profiles both profiles show upward increases in al ti k and rb and decreases in mg ca and na in addition the mafic regolith increases upward in zr and nb and decreases in zn and ni total fe decreases upward in both profiles but the sandstone profile retains significantly more of its initial fe than does the mafic dike this difference in fe loss is consistent with weathering in a low oxygen atmosphere of rock types with very different initial fe contents and therefore different atmospheric requirements for complete oxidation of the fe present the fe in the sandstone was mostly oxidized and retained within the profile whereas

permian paleoclimate data from fluid inclusions in halite abstract this study has yielded surface water paleotemperatures from primary fluid inclusions in mid permian nippewalla group halite from western kansas a cooling nucleation method is used to generate vapor bubbles in originally all liquid primary inclusions then surface water paleotemperatures are obtained by measuring temperatures of homogenization to liquid homogenization temperatures ranged from 21 c to 50 c and are consistent along individual fluid inclusion assemblages indicating that the fluid inclusions have not been altered by thermal reequilibration homogenization temperatures show a range of up to 26 c from base to top of individual cloudy chevron growth bands petrographic and fluid inclusion evidence indicate that no significant pressure correction is needed for the homogenization temperature data we interpret these homogenization temperatures to represent shallow surface water paleotemperatures the range in temperatures from base to top of single chevron bands may reflect daily temperatures variations these permian surface water temperatures fall within the same range as some modern evaporative surface waters suggesting that this permian environment may have been relatively similar to its modern counterparts shallow surface water temperatures in evaporative settings correspond closely to local air temperatures therefore the permian surface water temperatures determined in this study may be considered proxies for local permian air temperatures

surface crusts on soils sediments of the southern aral sea basin uzbekistan soils and sediments of the southern aral sea basin of central asia are commonly covered by salt bearing surface crusts these crusts represent a potential source of salt rich dust that can contribute to salinisation of soils in a large area crust types include takyric crusts surface crusts on solonchaks and salt crusts covering dry parts of the lake bed the takyric crusts are structural crusts showing features related to flooding and shrinkage gypsum formed within the sediment matrix is the only evaporite mineral they contain one studied solonchak crust is fine grained with a thin thenardite and bloedite coating along the irregular surface and halite coatings along the sides of pores all salts in this crust formed by evaporation of solutions contained in the groundmass a solonchak crust with a sandy texture contains prismatic gypsum crystals that formed in a water saturated surface layer as well as bloedite eugsterite and halite formed by evaporation of interstitial brines the lake bed crust is a pure accumulation of salt minerals bloedite hexahydrite halite kainite with synsedimentary and diagenetic features salt mineral assemblages in the three crust types are those that form during successive stages of evaporation of aral sea waters in agreement with published theoretical predictions

diagenesis of saline pan halite comparison of petrographic features of modern quaternary and permian halites abstract petrographic studies of modern saline pan halites saline valley ca salina omotepec baja california mexico and quaternary shallow buried 0 200 m halites saline valley ca bristol dry lake ca searles lake ca qarhan saline pan qaidam basin china lake uyuni bolivia show that the diagenetic modification of halite begins contemporaneously with deposition is most intense within the upper few meters of burial and is essentially complete within the first 45 m of burial halite crusts from modern saline pans that have undergone repeated episodes of flooding evaporative concentration and desiccation contain abundant syndepositional diagenetic features these mature modern halites are dominated by dissolution textures and fabrics formed during flood stages and cementati n textures formed during desiccation stages interlayered mud beds contain varying amounts of displacive halite crystals at shallow burial depths halites retain many textural features of mature modern saline pan halite halites below the first few meters are no longer susceptible to dissolution from floodwaters but continue to be cemented by clear halite within the first 10 m of burial cementation reduces the porosity of halite crusts to less than 10 the remaining pore spaces are completely filled by burial depths of approximately 45 m displacive growth of halite in muds continues at shallow burial depths and is probably limited to the first few tens of meters of burial depth the mechanisms for cementation and displacive growth of halite at shallow burial depths probably include 1 evaporative concentration of groundwater brines and 2 cooling of surface brines when they sink below the sedime t surface undeformed halites from the permian salado and rustler formations of new mexico contain delicate syndepositional textures and abundant clear halite cements that are comparable to those observed in modern saline pan halites and shallow buried halites the permian halites are interpreted to have undergone a depositional and early diagenetic history similar to the modern and quaternary analogs complete cementation of saline pan halites at shallow burial depths has important implications for the origin of saline formation waters in sedimentary basins parent evaporite brines may not be stored in the pores of halite rocks and later expelled during burial compaction if the rocks are cemented early and tightly crystallized halite rocks may also impede the downward migration of dense syndepositional brines

quantitative temperature records of mid cretaceous hothouse evidence from halite fluid inclusions abstract quantitative temperature reconstructions for the mid cretaceous are still rare although its typical greenhouse climate is regarded as one of the best analogues for future global warming for the first time mid cretaceous temperatures were quantitatively reconstructed based on homogenization temperatures th of halite fluid inclusions from the lower member of the nong bok formation in the thakhek mining area laos petrological features and primary textures of halite indicate a shallow water setting during halite formation that allows the use of homogenization temperatures as air temperature proxy obtained homogenization temperatures mainly range from 30 to 50 c probably representing local air temperature conditions of laos during the mid cretaceous the determined temperatures are relatively similar to temperatures in many modern and ancient evaporative settings the maximum homogenization temperature th max for the nong bok formation of 62 1 c is significantly higher than existing mid cretaceous paleotemperature records from both continental and marine sediments and comparable with the temperature records from the contemporaneous mengyejing formation of yunnan southern china the correspondence of the temperature records from laos and yunnan implies that very high temperature conditions prevailed in the region our results and other reconstructed very high temperatures from potash deposits e g 59 c for the silurian michigan basin and 58 c for the quaternary lop nur region suggest that extremely high temperatures probably had an important impact on the formation of the large potash deposits of the world however more studies are needed to improve our understanding of the detailed and quantitative relationships between temperature conditions and potash formation

stable isotopic compositions of carbonates from the mesoproterozoic bangemall group northwestern australia marine carbonate rocks from the mesoproterozoic bangemall group of northwestern australia show little deviation 1 3 in whole rock delta 13c carb values about a mean of 0 5 this narrow range persists despite close sampling every 10 20 m through long sections up to 2500 m that are geographically widespread up to 250 km apart over many depositional environments supralittoral to outer shelf sediment sources stromatolitic bioherms to detrital calcilutites and rock types pure limestones to dolomitic shales the only major excursions from the norm seem related to unusual environmental or post depositional processes as they are correlated with large enrichments to 3 or depletions to 16 in 18o relatively heavy delta 13c values up to 2 5 occur in a single bed of brecciated ferruginous dolostone at a single locality these abnormal values may result from local evaporitic conditions limey and shaley nodular dolostones have delta 13c values as low as 4 3 probably caused by remineralization of organic matter during late and patchy dolomitization most notably sharp negative excursions in delta 13c up to 8 4 occur in bleached kerogen free rocks with mineral assemblages of dolomite quartz calcite tremolite talc reflecting isotopic re equilibration in thick metamorphic aureoles around dolerite intrusions general environmental variations are minor with delta 13c values of peritidal facies tending to be slightly positive whereas those of subtidal facies are slightly negative there are no strong secular trends but subtle fluctuations within the range 2 to l can be correlated along the northwestern margin of the basin this resembles the pattern seen in other mesoproterozoic successions but is markedly unlike the heavy background 5 and extreme variations up to l0 in delta 13c evident in neoproterozoic successions of similar thickness and environmental setting hence in contrast to the neoproterozoic the global rate of organic carbon burial was probably fairly constant during deposition of the bangemall group and perhaps generally during the mesoproterozoic as was the redox state of the atmosphere and hydrosphere

paleobrine temperatures chemistries and paleoenvironments of silurian salina formation f 1 salt michigan basin u s a from petrography and fluid inclusions in halite abstract a 3 7 m stratigraphic section of the silurian salina group f 1 salt detroit salt company mine michigan basin was studied to document the paleodepositional conditions including brine chemistry and temperature of evaporite precipitation sedimentary features including rippled surfaces halite chevrons cumulate halite and dissolution surfaces confirm a shallow water depositional setting penecontemporaneous dissolution surfaces indicate that waters undersaturated with respect to halite were introduced into the michigan basin and that the basin brines were nonstratified during flooding allowing inflow waters to come into contact with halite crystals at the bottom fluid inclusions in primary chevron halite have homogenization temperatures between 5 and 25 c which represent brine temperatures during halite precipitation these temperatures are lower than expected for a marginal marine basin at a subtropical paleolatitude and they suggest a climatic cold spell for a period of thousands of years the major ions in fluid inclusion brines analyzed using the esem x ray eds method have relatively low concentrations of na mg2 and so42 and elevated concentrations of ca2 compared to modern seawater brine inclusion chemistries from the f 1 salt compare closely with the major ion composition of fluid inclusions from other silurian marine halites a 1 a 2 and b evaporites of the salina group and carribuddy group canning basin australia these results indicate a seawater parentage of the michigan basin f 1 salts and that the major ion chemistry of seawater remained more or less constant during the last 15 million years of the silurian detailed documentation of the temperatures brine chemistries and environments of halite deposition is a prerequisite for geobiological study of the entrapment of ancient microbes in salt the results reported here can help pinpoint the timing of entrapment of microorganisms in fluid inclusions in halite and can be used to argue that brine inclusions in the f 1 halites have been isolated and preserved in an unmodified state for more than 400 million years

ree chemistry and sm nd systematics of late archean weathering profiles in the fortescue group western australia two weathering profiles each consisting of an upper sericite rich zone and a lower chlorite rich zone are preserved between flows of the mt roe basalt in the fortescue group hamersley basin western australia ree concentrations in samples from these two profiles which originally developed ca 2 760 ma show large variations depending on stratigraphic position lree abundances and la yb n are greatest at depths of 3 6 m below the paleosurface of the mt roe 1 profile and are somewhat lower in samples above this level the lrees reach concentrations 6 9 times greater than in the underlying basalt and thus appear to have been mobilized downward in the paleosol and concentrated in its middle part lree concentrations in the 2 profile show a similar distribution but with a sharp increase in all ree concentrations within 50 cm of the paleosurface the distinction between the ree profiles in the two paleosols may be related to the difference in the overlying material the 1 paleosol is overlain by a few meters of sediments and then by basalt whereas the 2 paleosol is directly overlain by basalt the lrees appear to have been mobilized both during chemical weathering of the parental basalt and during later lower greenschist facies metamorphism and metasomatism of the paleosols remobilization of the rees during the regional metamorphism of the fortescue group is confirmed by a whole rock sm nd reference isochron of mt roe 1 samples with an age of 2 151 360 ma variable initial 143nd 144nd values of unweathered basalt samples which may represent the paleosol protolith prevents a confident determination of the magnitude of lree mobility both the initial mobilization of the rees during weathering and the metasomatic remobilization appear to have taken place under redox conditions where ce was present dominantly as ce3 because ce anomalies are not developed within the sericite zone samples regardless of concentration europium anomalies in the paleoweathering profile are somewhat variable and were probably modified by mobilization of eu2 at metamorphic conditions in all samples the hrees appear to have been relatively immobile and correlate with al ti cr v zr and nb sm nd systematics and ree patterns of four unweathered basalt samples indicate derivation of the mt roe basalts from a heterogeneous and enriched source having epsilon nd between 4 0 and 7 4 initial 143nd 144nd values of these basalts are even lower than those reported by nelson et al 1992 for fortescue group basalts and indicate a substantial crustal component in the generation of mt roe basalts

an examination of spherulitic dubiomicrofossils in precambrian banded iron formations using the transmission electron microscope abstract the discovery of microfossils from the banded iron formations of southern ontario tyler and barghoorn 1954 has spurred many researchers to attribute a biogenic origin to a great variety of unusual structures in precambrian bifs in particular laberge 1973 has argued that jaspery and sideritic spherulites common to all major bif deposits represent the fossilized remains of a unicellular blue green algae of the early proterozoic eosphaera tyleri oehler 1976b on the other hand regards such structures as crystallization products of a viscous and impure silica gel examination of these 30 m spherulites with a transmission electron microscope sheds doubt on both interpretations our analysis suggests that the jaspery spheres formed from the local recrystallization of the chert hematite matrix after contact with an infiltrating fluid thus these structures are best viewed as diagenetic features on the other hand we discovered that the sideritic spheres contain cores of apatite consequently these spheres may have a biogenic origin though the abundance of phosphate would indicate that they are not fossils of individual cells

40ar 39ar dating of late permian evaporites southeastern new mexico usa 40ar 39ar dating of the potassium magnesium sulfate mineral langbeinite from permian evaporites of the salado formation near carlsbad new mexico provides quantitative evidence that some salts in these deposits have not recrystallized for 251 myr since deposition survival of permian salts supports the possibility that bacillus bacteria recovered from nearby halite was isolated in a closed system and represents a sample of uncontaminated permian life local recrystallization of langbeinite and other nearby minerals is also indicated by the dating suggesting both the need and the opportunity to document closed system behavior more rigorously the shoaling and desiccation event recorded by the salado formation began at least 1 myr before the permian triassic boundary temporal correlation of the salado with the zechstein evaporites of north central europe supports previously inferred regression models for the origin of these deposits significant paleoenvironmental change at the permian triassic boundary thus occurred on a time scale more protracted than that implied by geologically instantaneous events such as bolide impacts

origin of depositional cycles in a permian saline giant the salado mcnutt zone evaporites of new mexico and texas two types of metre scale depositional cycles have been recognized within the mcnutt potash zone of the permian salado evaporites the cycles record progressive drawdown and concentration of brine in a shallow marginal marine basin type i cycles made of basal carbonate siliciclastic mudstone then anhydrite polyhalite pseudomorphous after primary gypsum overlain by halite and capped by muddy halite are interpreted as marine sea water dominated they formed by massive spillover of sea water through a connection with the permian ocean at high relative sea level stands lagoonal mudstone and anhydrite polyhalite after subaqueous gypsum followed by relative lowering of sea level and gradual basin restriction shallow saline lake and salt pan halite and ending with a desiccated basin isolated from the permian ocean salt pan halite and saline mudflat muddy halite cycle cap type ii cycles occur between the type i cycles and contain halite overlain transitionally by muddy halite they record a temporal evolution of environments from a shallow saline lake to an ephemeral salt pan saline mudflat complex and are interpreted as continental dominated sequences sourced by meteoric inflow from surrounding land areas that mixed with variable amounts of sea water either residual or introduced into the salado basin by seepage the vertical stacking of type i cycles is best explained by periodic invasions of sea water into the salado basin coincident with eustatic sea level rises the continental dominated type ii cycles formed during intervening periods of eustatic sea level fall and low stands the maximum time interval between major marine incursions is an average of 10 5 yr

early cambrian seawater chemistry from fluid inclusions in halite from siberian evaporites abstract thirty nine samples of lower cambrian marine sedimentary halite with zoned primary fluid inclusions were analyzed using the umca method introduced by petrichenko 1973 petrichenko o i 1973 metody doslidzhennya u mineralakh galogennykh porid naukova dumka kyiv 91 pp in order to determine the contents of k mg 2 so 4 2 and ca 2 ions and to interpret the composition of parent seawater the analyzed samples were from the giant salt basin of eastern siberia where five major phases of salt deposition can be distinguished in the late vendian danilovo and early cambrian usolye belsk angara and litvintsevo basins our samples are all from early cambrian basins although the largest data set comes from the angara basin the results indicate that early cambrian parent seawater was similar in all studied basins and was characterized by lower mg 2 and so 4 2 and higher ca 2 concentrations relative to modern seawater the concentration of k in early cambrian seawater was similar to that of modern seawater accordingly the seawater in the entire early cambrian was ca 2 rich and so 4 2 poor the change of composition of seawater from so 4 2 rich ca 2 poor in the latest neoproterozoic to ca 2 rich so 4 2 poor recorded throughout the early cambrian probably occurred within a relatively short time span during the earliest cambrian nemakit daldynian time and caused a rise in ca 2 concentrations in the shelf seas leading to the onset of biocalcification and then the cambrian explosion

extremely acid permian lakes and ground waters in north america evaporites hosted by red beds red shales and sandstones some 275 265 million years old extend over a large area of the north american mid continent1 they were deposited in non marine saline lakes pans and mud flats2 settings that are typically assumed to have been alkaline here we use laser raman microprobe analyses of fluid inclusions trapped in halites from these permian deposits to argue for the existence of highly acidic ph 1 lakes and ground waters these extremely acidic systems may have extended over an area of 200 000 km2 modern analogues of such systems may be natural acid lake and groundwater systems ph 2 4 in southern australia3 4 5 6 7 8 9 both the ancient and modern acid systems are characterized by closed drainage arid climate low acid neutralizing capacity and the oxidation of minerals such as pyrite to generate acidity the discovery of widespread ancient acid lake and groundwater systems demands a re evaluation of reconstructions of surface conditions of the past and further investigations of the geochemistry and ecology of acid systems in general

geochemical and mineralogic effects of contact metamorphism on banded iron formation an example from the transvaal basin south africa intrusion of a diabase sill into the paleoproterozoic kuruman iron formation transvaal basin south africa makes it possible to distinguish between effects of contact and regional metamorphism on mineralogic elemental and isotopic compositions of banded iron formation bif lithofacies temperatures within the aureole of contact metamorphism likely did not significantly exceed 450 c as suggested by the presence of early diagenetic carbonates greenalite and stilpnomelane formed prior to intrusion in chert rich facies as close as 4 m from the sill in sediments 32 m away from the intrusion a temperature of 280 c is indicated by the magnitude of 18o fractionation between successive chert and siderite microbands in unmetamorphosed equivalents similar isotopic analyses on whole rock samples yield temperature estimates between 150 and 230 c in comparison with samples of similar lithofacies from the underlying campbellrand kuruman transition zone carbonates from within the metamorphic aureole are depleted in 13c and 18o the abundance and c isotopic composition of total organic c toc in whole rock samples is lower and more enriched in 13c than those in samples outside of the zone of contact metamorphism within 5 m of the diabase sill the abundance of fe increases dramatically and the oxidation state of the sediments fluctuates considerably more than in sediments outside of the metamorphic aureole isotopic and mineralogic systematics in the zone of contact metamorphism in the kuruman iron formation are similar to those in siliceous dolomites and limestones altered by similar thermal processes as the most distinct isotopic and elemental variations occur within 10 m of the diabase sill it is suggested that volatilization and fluid infiltration associated with the intrusion were the main processes of alteration consideration of the effects of metamorphism both contact and regional as well as early diagenesis on the mineralogy and isotopic chemistry of bif sediments may be a key to our understanding of primary mineralogies and oxidation state of these enigmatic deposits

a general model of paraglacial landscape response a unifying attribute of all forms of paraglacial response is that deglaciation results in the exposure of unstable or metastable sediment sources that are subsequently tapped by a wide variety of processes over a wide range of timescales the paraglacial period in different geomorphological contexts is therefore con ditioned by two variables glacially conditioned sediment release and rate of sediment reworking under steady state conditions the latter may be approximated by an exhaustion model in which sediment yield is related to the amount of remaining available sediment by a negative exponential function this model offers an approximation for the behaviour of primary paraglacial systems in which glacigenic sediment sources are not replenished the long term behaviour of secondary primarily uvial paraglacial systems in which sediment inputs include both in situ and reworked glacigenic sediment appears intrinsically more complex but consistent with an exhaustion model if initial sediment avai

the antiquity of oxygenic photosynthesis evidence from stromatolites in sulphate deficient archaean lakes the tumbiana formation about 2700 million years old was largely deposited in ephemeral saline lakes as judged by the unusual evaporite paragenesis of carbonate and halite with no sulfate stromatolites of diverse morphology occur in the lacustrine sediments some with palimpsest fabrics after erect filaments these stromatolites were probably accreted by phototropic microbes that from their habitat in shallow isolated basins with negligible sulfate concentrations almost certainly metabolized by ozygenic photosynthesis

a 106ka paleoclimate record from drill core of the salar de atacama northern chile abstract a 100 m long salt core sqm 2005 from the salar de atacama northern chile 23 s 68 w a dry lake bed contains a 106 kyr paleoclimate record of hydrologic balances on the western slopes of the central andes of south america six u series disequilibrium dates range sequentially from 106 1 6 4 to 5 4 2 7 ka based on sedimentary structures and petrographic textures of salts and associated siliciclastic sediments interpretations of paleoenvironments and net hydrologic balance suggest that relatively wet periods saline lakes and expanded mudflats existed in the salar de atacama from 75 7 to 60 7 ka and from 53 4 to 15 3 ka with the wettest perennial lake interval from 26 7 to 16 5 ka short relatively wet periods also occurred in the holocene from 11 4 to 10 2 ka and from 6 2 to 3 5 ka these wet periods at salar de atacama correspond well with other late pleistocene climate records from the central andes that are a function of the net hydrologic budget the minchin tauca lake sequence from salar de uyuni bolivia is synchronous with the 53 4 15 3 ka saline lake wet period at salar de atacama the tauca phase coincided with the wettest perennial lake interval at salar de atacama from 26 7 to 16 5 ka the coipasa lake phase from uyuni was probably contemporaneous with the early holocene wet period at salar de atacama from 11 4 to 10 2 ka the early holocene wet interval at salar de atacama was also synchronous with the maximum holocene lake levels of the chilean altiplano lakes to the east and with grass rich rodent middens between 11 8 and 10 5 ka in age from the atacama basin the lake period at salar de atacama between 26 7 and 15 3 ka compares closely with low 18o values low anion concentrations and high accumulation rates from the sajama glacial ice core southwestern bolivia between 25 and 15 5 ka it is concluded that wet and dry phases were synchronous in the central andean plateau of southwestern bolivia and along the western flank of the andes of northern chile over the past 50 kyr this region which today receives its moisture from the amazon basin to the east probably also did so in the past the wet periods at salar de atacama are in phase with january insolation maxima at 15 s at 70 45 and 20 ka which suggests that past changes in summer insolation influenced precipitation patterns in the central andes however there are no major wet periods linked to the january insolation maximum at 93 ka and the present day extremely dry climate in the atacama desert is associated with a peak in summer insolation therefore there must be other important influences over precipitation in the central andes which modify the first order insolation controls

contrasting siliciclastic evaporite strata in subsurface and outcrop an example from the permian nippewalla group of kansas u s a abstract geologists tend to expect that rocks as they appear in outcrop are a very good approximation of the same strata in the subsurface but this is not the case in mixed siliciclastic evaporite units strata that contain both a siliciclastic and an evaporite mineral component distinct differences in lithologic and stratigraphic descriptions of ancient siliciclastic evaporite strata exist between outcrop and core these differences present challenges in stratigraphic nomenclature lithologic correlation age determinations and interpretations about past depositional environments diagenetic history and paleoclimate an example of siliciclastic evaporite strata is the middle permian to early triassic gypsum and or anhydrite hereby referred to as gypsum anhydrite and halite bearing red beds throughout the midcontinent of north america and equivalent strata from other pangean deposits here we use core and field observations of the middle permian nippewalla group in kansas to show the range of similarities and differences in lithologies and thicknesses of specific lithofacies in outcrop and at various depths for example the displacive halite lithology consisting of red mudstones dominated by randomly oriented halite crystals is abundant in cores and interpreted as saline mudflat deposits the outcrop counterpart is less common friable massive red mudstones with some gypsum anhydrite pseudomorphs after displacive halite crystals we interpret these lithologic differences of this saline mudflat lithofacies as the result of excellent preservation of buried displacive halite and late stage dissolution of near surface halite additionally bedded halite and intergranular halite cements in siltstones and sandstones are also vulnerable to late stage dissolution near the surface further modifying lithologies and thicknesses thickness of the nippewalla group in the amoco rebecca k bounds core of western kansas is 931 feet 284 meters thick but it is estimated to be only half as thick in the outcrop belt of south central kansas to estimate amount of rock lost to late stage dissolution we conducted dissolution experiments on displacive halite units from cores which resulted in 60 95 loss of rock thickness and mass due to dissolution of halite the unconsolidated red sediment resulting from these dissolution experiments compares favorably with much of the fine massive red siliciclastics that make up the greater part of the nippewalla group outcrops we propose that major lithologic differences resulting from near surface diagenetic processes must be expected in any evaporite bearing siliciclastic unit besides guiding correlation attempts between surface and subsurface this knowledge is vital for making accurate interpretations of depositional and diagenetic history of siliciclastic evaporite units

tracking physicochemical conditions of evaporite deposition by stable magnesium isotopes a case study of late permian langbeinites magnesium isotopic compositions of evaporite deposits may record information concerning brine evolution during deposition we report mg isotopic values delta mg 26 dsm3 measured from an evaporite deposit of langbeinite k2mg2 so4 3 found in the permian salado formation we used these data to model mg isotope fractionation between langbeinite and its parent brine in addition both measured and theoretical results are used to estimate precipitation temperature and interpret depositional environment the salado langbeinite delta mg 26 values are relatively low and fall within a relatively narrow range 4 12 0 03 parts per thousand to 3 81 0 07 parts per thousand equilibrium fractionation factors between langbeinite and aqueous mg2 solutions were calculated using quantum chemical density functional theory all computations were performed at the b3lyp 6 31 g d p level solvation effects were addressed using a solvent model water droplet approach and mineral structures were investigated using volume variable cluster models vvcm the equilibrium mg isotopic fractionation factors a between langbeinite and model brine solution we obtained are 1 0005 1 0004 and 1 0003 delta mg 26 langb water approximate to 10 3 ln alpha 0 473 parts per thousand 0 390 parts per thousand and 0 322 parts per thousand at 10 degrees c 25 degrees c and 40 degrees c respectively these relatively large equilibrium fractionation factors indicate significant mg isotope fractionation between langbeinite and its parent brine during precipitation as langbeinite preferentially incorporates the heavier mg 26 and mg 25 isotopes rayleigh distillation modeling of the salado langbeinite s relatively light mg isotopic composition requires delta mg 26 dsm3 values of 4 parts per thousand for the parent brine models favor a precipitation temperature as high as 40 degrees c under equilibrium conditions potential disequilibrium precipitation conditions suggested by mg isotopic data also imply rapid deposition in a hot arid sedimentary environment prevailing in the southwestern u s during the late permian

the global water cycle and continental erosion during phanerozoic time 570 my asensitivity study is conducted to determine what effect two mechanisms namely continental size and latitudinal location might have on the global wtaer cycle the global water cycle over phanerozoic time 570 my is established first by analyzing the distribution of rainfall p evaporation e and runoff d by bands of 10 of latitude on the present day earth and then applying these values to the ancient phanerozoic world in this backward projection the global cosmic climatic and orographic conditions prevailing today are supposed constant through time while the only variable parameter controlling the system are the latitudinal positions of the continents and the relative area of continents and oceans the calculated phanerozoic global runoff clearly shows that the humid periods are the cretaceous 100 my the devonian silurian 400 my and the cambrian 500 my while the dry periods are close to the present day 0 my and the permo triassic 200 my the continal global runoff together with the survival rate of the volcanics are used to predict the fluctuations of the isotopic ratio 87sr 86sr in marine sediments predicted and measured values appear to be in good agreement except for the present which somewhat validate the calculations the continental runoff is also related to the sedimentation rate and used to estimate the specific erosion rate of the continents through the phanerozoic thus the sedimemtation rate variations are understood as a consequence of the continental runoff fluctuations through time

temperature seasonality control on modern halite layers in the dead sea in situ observations layered halite sequences are found in deep basins throughout the geological record however analogs for such sequences are commonly studied in shallow environments here we studied active precipitation of halite layers from the only modern analog for deep halite precipitating basins the hypersaline dead sea in situ observations in the dead sea link seasonal thermohaline stratification halite saturation and the characteristics of the actively forming halite layers the spatiotemporal evolution of halite precipitation in the dead sea was characterized by means of monthly observations of 1 lake thermohaline stratification temperature salinity and density 2 degree of halite saturation and 3 textural evolution of the active halite deposits we present the observed relationships between the textural characteristics of layered halite deposits i e grain size consolidation and roughness and the degree of saturation which in turn reflects the limnology and hydroclimatology the lake floor is divided into two principal environments a deep hypolimnetic lake floor and a shallow epilimnetic lake floor in the deeper hypolimnetic lake floor halite continuously precipitates with seasonal variations 1 during summer consolidated coarse halite crystals form rough surfaces under slight supersaturation 2 during winter unconsolidated fine halite crystals form smooth lake floor deposits under high supersaturation these observations support interpretations of the seasonal alternation of halite crystallization mechanisms the shallow epilimnetic lake floor is highly influenced by the seasonal temperature variations and by intensive summer dissolution of part of the previous year s halite deposit which results in thin sequences with annual unconformities this emphasizes the control of temperature seasonality on the characteristics of the precipitated halite layers in addition precipitation of halite on the hypolimnetic floor at the expense of the dissolution of the epilimnetic floor results in lateral focusing and thickening of halite deposits in the deeper part of the basin and thinning of the deposits in shallow marginal basins

missing records and depositional breaks in french late pleistocene cave sediments abstract cave entrance and rock shelter infillings are positioned within the pleistocene chronology for three areas of france northern alps franche comte and perigord despite minor local variations it is possible to identify regional types with a consistent depositional record over long intervals of time the interregional variability relates to the frequency and position of the gaps within the infillings sites in the northern alps have not yielded any artifacts older than the upper paleolithic magdalenian and dated sedimentary sequences do not go back beyond the older dryas more complete sequences in franche comte contain mousterian industries two major gaps occur here one lasting about 50 000 yr during the lower glacial and lower pleniglacial periods and the other lasting some 10 000 yr during the upper pleniglacial the sequences are more complete in the perigord where all major climatic phases have been identified with no significant sedimentary gaps differences in sedimentary records can be explained by variations in regional conditions during the last interglacial glacial cycle and especially by the distance from the maximum advance of ice daring glaciation

fluid inclusions in sedimentary and diagenetic systems abstract some of the major problems in sedimentary geology can be solved by using fluid inclusions in sedimentary and diagenetic minerals important fluids in the sedimentary realm include atmospheric gases fresh water of meteoric origin lake water seawater mixed water evaporated water formation waters deep in basins oil and natural gas preserving a record of the distribution and composition of these fluids from the past should contribute significantly to studies of paleoclimate and global change research is essential for improving understanding of diagenetic systems and provides useful information in petroleum geology applications of fluid inclusions to sedimentary systems are not without their complexities some fluid inclusions exposed to natural conditions of increasing temperature may be altered by thermal reequilibration which results in stretching or leakage and refilling of some fluid inclusions similarly overheating in the laboratory can also cause reequilibration of fluid inclusions so fluid inclusions from the sedimentary realm must be handled carefully and protected from overheating natural overheating of fluid inclusions must be evaluated through analysis of the most finely discriminated events of fluid inclusion entrapment fluid inclusion assemblages fia consistency in homogenization temperatures within a fluid inclusion assemblage consisting of variably sized and shaped inclusions is the hallmark of a data set that has not been altered through thermal reequilibration in contrast fluid inclusion assemblages yielding variable data may have been altered through thermal reequilibration if a fluid inclusion assemblage has not been altered by thermal reequilibration its fluid inclusions may be useful as geothermometers for low and high temperature systems or useful as geobarometers applicable throughout the sedimentary realm if a fluid inclusion assemblage has been altered partially by thermal reequilibration techniques for distinguishing between altered and unaltered fluid inclusions may be applied in studies of global change fluid inclusions can be used as sensitive indicators of paleotemperature of surface environments fluid inclusions also preserve microsamples of ancient seawater and atmosphere the analysis of which could figure prominently into discussions of past changes in chemistry of the atmosphere and oceans in petroleum geology fluid inclusions have proven to be useful indicators of migration pathways of hydrocarbons they can delineate the evolution of the chemistry of hydrocarbons and they remain important in understanding the thermal history of basins and relating fluid migration events to evolution of reservoir systems in studies of diagenesis fluid inclusions can be the most definitive record most diagenetic systems are closely linked to temperature and salinity of the fluid thus fluid inclusions are sensitive indicators of diagenetic environments

ancient microspheres abiogenic protobiogenic or biogenic criteria of biogenicity of microspheroidal objects which have been interpreted as microfossils are here reviewed in the light of additional data much weight has been placed by some commentators on constrained heterogeneity as a primary criterion of biogenicity the data from the field and laboratory suggest the need for continuing reservation in the interpretation of these objects on the basis of these and other data reasons are given for the alternative explanation that the objects are lithified relics of protobiotic assemblages the question remains open as to whether the early archean spheroidal objects are abiotic protobiotic or biotic in origin

quantitative temperature recovery from middle eocene halite fluid inclusions in the easternmost tethys realm middle eocene climatic reconstruction has long been the focus of geoscientists however quantitative temperature records for this interval remain lacking the easternmost tethys realm is especially problematic because the traditional climatic proxies are limited by the presence of widespread and thick evaporite deposits in this study we present the first quantitative seawater temperatures records revealed by homogenization temperatures th of primary halite fluid inclusions from the middle eocene xiaokuzibai formation of the kuqa basin in western china a total of 231 th data were obtained from two halite samples with values ranging from 12 8 to 37 3 c average th values of 22 4 c and 23 3 c are in good agreement with the previous studies of climatic proxies by combining our results with previously reported temperature records we infer that the entire tethys realm experienced similar climate conditions during the middle eocene including a maximum seawater temperature above 34 c which may be related to the middle eocene climatic optimum

late quaternary climatic change in france estimated from multivariate pollen time series abstract in regions like southern france where usual analytical techniques are unsatisfactory due to the heavy influence of human activity and the existence of a complex climate the quantitative reconstruction of climate from pollen is particularly difficult that is why an original method has been performed the first step of the method based on best analogs estimation and multiple regression is to calculate a relationship between climate monthly temperature and precipitation and modern pollen spectra for data from 182 sites the result is called the analog climate the second step of the method an original combination of canonical correlation and principal components analyses extracts the common information from several fossil pollen sequences to produce a so called paleobioclimate this step removes the effects of local differences in the vegetation among nearby sites and also reduces the effects of human disturbance in the third step the signals obtained from the first two steps are merged by kalman filter into a final reconstruction where the noise is reduced by around 37 the results presented with a 95 confidence level suggest that the pleni wurm was 7 to 13 c colder than present and had 20 to 60 less precipitation than today this large confidence takes into account the climatic diversity of the region at 13 000 yr b p the climate reached the modern level of precipitation but the temperature was just less than present the subsequent decrease of precipitation is less important than that of temperature this fact may explain the advance of alpine glaciers during the younger dryas preboreal warming was abrupt 3 to 4 c per 500 yr and precipitation increased more slowly

the nature of fossil bacteria a guide to the search for extraterrestrial life in an attempt to establish reliable criteria for the identification of potential fossil life in extraterrestrial materials the fossilizable characteristics of bacteria namely size shape cell wall texture association and colony formation are described and an overview is given of the ways in which fossil bacteria are preserved as compressions in fine grained sediments preservation in amber permineralized by silica replacement by minerals such as silica pyrite fe mn oxides calcite phosphate and siderite or as molds in minerals the problem of confounding minerally replaced bacteria with non biological structures having a bacterial morphology is addressed examples of fossilized bacteria from the early archaean through to the recent are used to illustrate the various modes of preservation and the morphology of fossil bacteria

sedimentology of ancient saline pans an example from the permian opeche shale williston basin north dakota u s a abstract the mid permian opeche shale of north dakota consists of bedded evaporites and red bed siliciclastics detailed core and petrographic study has documented sedimentary and early diagenetic features in order to develop a depositional model and to refine paleoclimatic data and paleogeographic setting for the late paleozoic of the u s midcontinent lithologies and sedimentary features indicate lacustrine distal alluvial and minor eolian deposition subaerial exposure and soil formation bedded halites consisting of chevron and cumulate crystals dissolution surfaces and pipes and mudcracked microcrystalline salt crusts were deposited in a saline pan dominated by flooding evaporative concentration and desiccation bedded halites containing chevron and cumulate crystals but lacking any dissolution or desiccation features formed in perennial saline lakes chaotic halite composed of red mudstone and siltstone with displacive halite crystals represents saline mudflat deposits red mudstone and siltstone with little or no displacive halite but with abundant cracks and root features suggest deposition in a dry mudflat red bed sandstones and conglomerates composed of poorly sorted subrounded quartz grains cemented with halite indicate distal alluvial deposition with possible transport by ephemeral streams sheet floods and debris flows most deposition took place in halite dominated shallow perennial and ephemeral saline lakes surrounded by saline and dry mudflats evaporation desiccation flooding and wind played significant roles in this environment therefore the opeche evaporites and red beds are representative of an ancient saline pan system an inland playa setting is favored as a depositional model for the opeche shale the abundance of soil features and halite dominance as well as lack of nearshore carbonates and lack of restricted marine fossils suggest a closed basin nonmarine setting for the mid permian of the u s midcontinent

paleoclimate reconstruction during the messinian evaporative drawdown of the mediterranean basin insights from microthermometry on halite fluid inclusions 1 data constraining the paleoenvironmental conditions during the messinian evaporative drawdown of the mediterranean basin are still conflicting here we present a comprehensive paleoclimatic reconstruction during messinian halite deposition from several italian sites we performed fluid inclusion analyses to define better both the composition of the mediterranean water body and the paleotemperatures of the messinian brine during halite crystallization we measured homogenization temperatures on 218 primary all liquid fluid inclusions in messinian halite from the volterra crotone and caltanissetta evaporite basins these measurements provided mean homogenization temperatures of 17 18 c with a range between 10 11 c and 28 29 c which should be close to the sst of the mediterranean sea during halite deposition the occurrence of major elements such as cl na mg s ca and k within the halite fluid inclusions together with the presence of minerals such as pentahydrite polyhalite and ca k and mg sulfates indicates that these salt bodies originated from mainly marine water taking into account both the present day annual sst of the mediterranean sea around the sampling sites which ranges between 18 and 20 c and the lower latitude of the mediterranean basin during the messinian salinity crisis our homogenization temperatures point to a colder climate during the messinian halite deposition compared to the present interglacial climate stage this conclusion is consistent with halite deposition during a late miocene glacial interval tg12

polymeric substances and biofilms as biomarkers in terrestrial materials implications for extraterrestrial samples organic polymeric substances are a fundamental component of microbial biofilms microorganisms especially bacteria secrete extracellular polymeric substances eps to form slime layers in which they reproduce in the sedimentary environment biofilms commonly contain the products of degraded bacteria as well as allochthonous and autochthonous mineral components they are complex structures which serve as protection for the colonies of microorganisms living in them and also act as nutrient traps biofilms are almost ubiquitous wherever there is an interface and moisture liquid liquid liquid solid liquid gas solid gas in sedimentary rocks they are commonly recognized as stromatolites we also discuss the distinction between bacterial biofilms and prebiotic films the eps and cell components of the microbial biofilms contain many cation chelation sites which are implicated in the mineralization of the films eps biofilms and their related components thus have strong preservation potential in the rock record fossilized microbial polymeric substances fps and biofilms appear to retain the same morphological characteristics as the unfossilized material and have been recognized in rock formations dating back to the early archaean 3 5 b y we describe fps and biofilms from hot spring deep sea volcanic lake and shallow marine littoral environments ranging up to 3 5 b y in age fps and biofilms are more commonly observed than fossil bacteria themselves especially in the older part of the terrestrial record the widespread distribution of microbial biofilms and their great survival potential makes their fossilized remains a useful biomarker as a proxy for life with obvious application to the search for life in extraterrestrial materials

geology and major and trace element chemistry of late archean weathering profiles in the fortescue group western australia implications for atmospheric po2 abstract we have identified two thick weathering profiles between flows of the mt roe basalt unit of the fortescue group in the pilbara area of western australia the age of weathering is constrained by u pb zircon dating to lie between 2765 and 2715 ma the profiles herein referred to as the mt roe 1 and 2 paleosols were mapped in detail for 1500 m and 760 m along strike respectively samples were collected along traverses across both profiles where they were well developed and well exposed the profiles which may be structurally offset parts of the same weathering horizon have well developed upper sericite zones 1 15 m thick these grade downward into chlorite rich zones which are chemically and physically heterogeneous the chlorite zones grade downward into unweathered basalts the mt roe 1 profile is overlain by 2 6 m of bedded probably lacustrine sediments these in turn are covered by succeeding lava flows evidence of a surficial origin for the paleosols includes mud cracks ripple marks and rip ups of the paleosol material in the post paleosol sediments soft sediment deformation and probable dewatering structures are present along the paleosol sediment contact the mt roe 2 profile is overlain directly by the succeeding lava flow with little or no intervening sediments some brecciation and pillowing is observed along the base of the overlying basalt flow in both cases probably due to emplacement of lava into a shallow lake or onto wet soil in the sericite zones of both profiles nearly all of the fe mn mg and zn and a substantial fraction of the ca pb na ni and si have been leached the chlorite zones have elevated fe pb ni and zn contents and appear to be repositories of elements lost from the sericite zone al ti zr and th were immobile in the mt roe 1 paleosol and are concentrated by factors of 2 5 2 6 over the unweathered basalt v u and cr were also nearly immobile major element and trace element data indicate that weathering took place under conditions of low atmospheric oxygen k is strongly enriched toward the upper contact of the sericite zone and was introduced during post weathering metasomatism together with rb and sr na and ca are also enriched near the top of each profile and small amounts of each may have been introduced during regional low grade metamorphism of the hamersley basin at 2168 10 ma

a master of the earth h d holland and his contributions to geochemistry abstract h d holland was one of the great geochemists of modern times as a professor at princeton university for 22 years and at harvard for 33 he mentored 24 graduate students and 24 postdoctoral researchers he was a member of the u s national academy of sciences and a president of the geochemical society he co authored 179 publications in 64 years from 1949 to 2012 including four books he edited one other book and with karl turekian co edited the ten volume treatise on geochemistry his contributions to geochemistry were mainly in economic geology hydrothermal processes and especially the chemistry and evolution of the earth s atmosphere and oceans a topic to which he devoted nearly half of his publications his most significant contributions documented changes in the composition of seawater through geologic time and the rise of oxygen in earth s atmosphere he pioneered the use of mineral sequences in marine evaporite deposits and fluid inclusions in evaporite minerals to determine the composition of ancient seawater he collected extensive data on paleosols and used them to calibrate the oxygen content of the ancient atmosphere documenting its rise in the great oxidation event that peaked between 2 41 and 2 32 ga and writing extensively about the causes of this event one of the most significant in earth history

early archean fossil bacteria and biofilms in hydrothermally influenced sediments from the barberton greenstone belt south africa abstract sem imaging of hf etched 3 3 3 5 ga cherts from the onverwacht group south africa reveals small spherical 1 m diameter and rod shaped structures 2 3 8 m in length which are interpreted as probable fossil coccoid and bacillar bacteria prokaryotes respectively preserved by mineral replacement other possibly biogenic structures include smaller rod shaped bacteriomorphs 900 m textures in the sediments in which these biogenic structures occur suggest that they were probably deposited in a shallow water environment which was subjected to intermittent subaerial exposure pervasive hydrothermal activity is evidenced by oxygen isotope studies as well as the penecontemporaneous silicification of all rock types by low temperature 220 c hydrothermal solutions

paleotemperatures preserved in fluid inclusions in halite a variety of paleoclimate proxy records allow determination of relative warming or cooling however if we are to understand climate change quantification of past temperature fluctuations is essential our research indicates that fluid inclusions in halite can yield homogenization temperatures that record surface brine temperatures at the time of halite precipitation to avoid problems with stretching leaking and initial trapping of air samples with primary single phase liquid fluid inclusions are chilled in a freezer to nucleate vapor bubbles we tested the reliability of this method of obtaining fluid inclusion homogenization temperatures using modern salts precipitated at badwater basin death valley california homogenization temperatures correlate well with measured brine temperatures the same method is applied to fluid inclusions in pleistocene halite from a core taken at the same location in death valley results are at several scales recording diurnal temperature variations seasonal temperature fluctuations and longer term warming and cooling events that correlate with major changes in the sedimentary environment related to climate this technique is uniquely instrumental for paleoclimate studies because it offers actual not just proxy paleotemperature data 27 refs 17 figs

halite depositional facies in a solar salt pond a key to interpreting physical energy and water depth in ancient deposits subaqueous deposits of aragonite gypsum and halite are accumulating in shallow solar salt ponds constructed in the pekelmeer a sea level salina on bonaire netherlands antilles several halite facies are deposited in the crystallizer ponds in response to difference in water depth and wave energy cumulate halite which originates as floating rafts is present only along the protected upwind margins of ponds where low energy conditions foster their formation and preservation cornet crystals with peculiar mushroom and mortarboard shaped caps precipitate in centimetre deep brine sheets within a couple of metres of the upwind or low energy margins downwind from these margins cornet and chevron halite precipitate on the pond floors in water depths ranging from a few centimetres to approximately 60 cm halite pisoids with radial concentric structure are precipitated in the swash zone along downwind high energy shorelines where they form pebbly beaches this study suggests that primary halite facies are energy and or depth dependent and that some primary features if preserved in ancient halite deposits can be used to infer physical energy conditions subenvironments such as low to high energy shorelines and extremely shallow water depths in ancient evaporite basins

sedimentation in proglacial sunwapta lake alberta the hydrologic and limnologic conditions of sunwapta lake a small proglacial lake in the canadian rocky mountains were investigated with special reference to the sedimentology of this lake discharge and suspended sediment concentrations of the inflowing streams were measured to give estimates of sediment input distribution of large loads of fine glacial sediment is largely by an inflow and wind controlled circulation which commonly fluctuates diurnally the spatial distribution of sedimentation was determined by use of sediment collecting pans placed on the lake bed turbidity currents are rare with only one event monitored in 2 years this event was caused by a burst of highly sediment charged inflow water the rarity of turbidity currents is attributed to the high sediment concentration in the lake water which results from the small size of the lake in relation to the inflow wind generated water movement at the lake floor ranges from 0 0 0 03 m s while the maximum recorded velocity of the turbid

deposition and early alteration of evaporites summary the depositional settings for primary and early diagenetic evaporite deposits generally fall into three categories marginal mixed shallow subaqueous and subaerial shallow and deep subaqueous these three environmental groupings hold for both marine and nonmarine settings although the details of continental evaporites may be far more complex than in most marine fed water bodies the primary evaporite morphologies from many continental playa hypersaline marine and marine marginal depositional settings are reasonably well understood because of the numerous detailed studies of recent holocene and cenozoic deposits that serve as models for sedimentary interpretation the sedimentological features that develop in deeper water settings are inferred based on examination of unaltered cenozoic deposits each environmental setting develops characteristic depositional features and patterns and one facies grades into the next because there may be significant physiochemical changes in water composition during deposition as well as sudden change s in both water depth and basinal circulation description and interpretation of evaporative rocks should not be based on mineralogy alone but on the distinct sedimentary characteristics of each part of a deposit in cases where sediments still reflect their primary mineralogy and morphology most of the environments can now be recognized however geochemical studies are commonly required to determine the source s of the original water the determinative geochemical techniques that presently serve as a support to sedimentologic study include studies of fluid inclusions bromine content of chloride salts and the stable isotopes of strontium sulphur carbon and oxygen only after these and perhaps other chemical analyses are considered can the full depositional history of a region be reasonably unravelled

sediment yield from glacio lacustrine calcareous deposits during the postglacial period in the combe d ain jura france the middle valley of the river ain jura cuts through glacio lacustrine deposits laid down in an ice dammed lake during the most recent glacial advance the total volume eroded is about 6 21 10 8 m 3 for a surface area of 3 7 10 7 m 2 erosion occurred between 18 ka bp and 6 ka bp i e over a duration of some 12 ka sediment yield from the area was of the order of 2500 t km 2 a 1 which is comparable with modern day sediment yield from nw african badlands these high values are ascribed to the amenability of glacio lacustrine deposits to mechanical weathering and to the rapid geomorphological changes that affected glacial and paraglacial sedimentary cover after the retreat of the ice the valley slopes were destabilized by mass wasting earthflow and mudflow which was the predominant erosional process the slopes are currently stabilized or very exceptionally active 1998 john wiley sons ltd

burial evolution of evaporites with implications for sublacustrine fan reservoir quality a case study from the eocene es4x interval dongying depression bohai bay basin china abstract eocene sublacustrine fan sandstones that developed in a rift basin are important tight gas reservoirs in the dongying depression bohai bay basin northeastern china two units of evaporites developed at the top and bottom of the lower unit of the es4 interval es4x consist predominantly of anhydrite with subordinate gypsum evaporite and related diagenetic processes greatly influenced reservoir quality 13 c values for micritic dolomite cements in es4x are depleted 7 45 to 2 57 due to microbial sulfate reduction msr under shallow burial conditions and this interpretation is supported by large 34 s fractionation between anhydrite and framboidal pyrite precipitation temperatures for micritic dolomite are calculated as 57 5 72 8 c anhydritization of gypsum probably occurred at 100 5 145 2 c during progressive burial as evidenced by homogenization temperatures of aqueous inclusions within anhydrite cements this process resulted in dehydration fractures within anhydrite cements that increased reservoir permeability by connecting isolated pores thermochemical sulfate reduction tsr probably resulted in dissolution of gypsum and anhydrite cements under relatively deep burial conditions ankerite cements are replaced by anhydrite cements and are enclosed by solid bitumen in es4x ankerite cements likely were derived from tsr as reflected in negative 13 c values 7 12 to 3 70 and high calculated temperatures 121 3 185 1 c dissolution by products e g saddle dolomite ankerite nodular pyrite related to tsr precipitated in adjacent pores a lack of significant 34 s fractionation between parent sulfate and nodular pyrite indicates that tsr occurred in a relatively closed system therefore dissolution of gypsum and anhydrite related to tsr contributed little to reservoir quality middle fan lithofacies with better sorting porosity and permeability than inner and outer fan lithofacies constitute high quality reservoirs in es4x