evaporation from cultivated soils containing rock fragments abstract evaporation from bare soil surfaces represents an important water loss for agriculture in semi arid regions numerous efforts have been undertaken to modify the topsoil characteristics mulching tillage in order to create a thin dry topsoil that reduces evaporation however little attention was paid to the role of natural rock fragments in topsoils with respect to evaporation this paper presents the results of laboratory experiments simulating evaporation from initially wet and air dry soils containing a range of rock fragment contents and compares them to field conditions evaporation was stimulated by blowing fans at one high evaporative demand eo 7 7 9 2 mm day 1 time domain reflectometry tdr was used to investigate the relation between the water content of the topsoil and the actual evaporation rate for soils at field capacity initial fine earth water content decreases with rock fragment content and consequently evaporation rates decrease in the same order for air dry soils that received a limited amount of rain 10 and 20 mm an opposite behaviour was observed initial fine earth water content and evaporation rates increase with rock fragment content a strong positive sigmoidal relation between relative evaporation rate actual over open pan evaporation rates and fine earth water content in the centre of the wetted soil section was observed during the laboratory experiments except for the columns covered with a mulch there were no systematic differences in this relation between the treatments a rock fragment mulch reduces evaporation rate at a given soil water content significantly these trends explain the often ambivalent effects of rock fragments on evaporation rates in the field

unsaturated hydraulic conductivity in limestone dolines influence of vegetation and rock fragments abstract vegetation and rock fragments have a profound impact on runoff generation in the dolines of the sierra de gador southeastern spain this study investigated the effect of vegetation and rock fragments on unsaturated hydraulic conductivity k h in three limestone dolines and examined whether variation in k h was consistent with differences in runoff from simulated rainfall tension infiltrometers were used to measure unsaturated hydraulic conductivity at three pressure heads h of 30 60 and 120 mm at 70 locations within the three dolines generally the trends of the k h were consistent with the simulated rainfall data and accounted for difference in runoff for the vegetated surfaces vegetation resulted in high infiltration with unsaturated hydraulic conductivities at 30 and 60 mm are significantly greater for the vegetated surface than for the rock fragment covered surface and bare soil surface rock fragments had no obvious effect on soil hydraulic conductivity as compared with bare soils the k h of the non crusted soil were 2 5 times higher than that of the crusted soil the k h decreased with increasing tensions k 60 and k 120 were only 8 4 and 0 89 respectively of k 30 for the vegetated surfaces and were about 30 and 8 7 respectively of k 30 for both rock fragment covered surfaces and bare soils suggesting that pores in the 0 5 to 1 mm diameter range dominate flow under unsaturated conditions there were significant differences in k h among the different topographic units of the dolines and k h tended to be higher in the upper position than in the lower position of the doline

miocene sea level falls related to the geologic history of midway atoll a period of atoll emergence results in the development of a karst surface on the atoll upon resubmergence this surface is preserved as a subsurface solution unconformity that can be identified by petrographic characteristics and a distinctive stable isotope signature imprinted by subaerial or phreatic diagenesis determination of the magnitude of miocene sea level falls by considering subsidence rates and depths to solution unconformities must take into account the lowering of the emergent atoll surface by dissolution previously the depth to a miocene solution unconformity below midway atoll was assumed to record a maximum highstand of sea level that preceded a period of island emergence however because of surface dissolution the solution unconformity must represent some elevation between a past highstand and a subsequent lowstand the subsurface stratigraphy of midway atoll shows that a late miocene sea level fall of 75 125 m below present sea level took place the magnitude of this fall is greater than that previously determined on the basis of stable isotope data from midway atoll but approximates miocene sea level falls determined by seismic stratigraphic methods

the neogene larger foraminiferal sequence in the australian and new zealand regions and its relevance to the east indies letter stage classification abstract in northern australia neogene larger foraminifera range from the late oligocene into the earliest middle miocene and are restricted to the late early miocene in southern australia in contrast these forms range over a longer interval in new zealand from late oligocene to mid middle miocene even though correlation with the letter stages lower te to lower tf can be achieved the usefulness of these stages to southeastern australia and new zealand is reduced because of the lower diversity of faunas in this area compared with areas nearer the equator the association of good planktic foraminiferal faunas with the larger foraminifera further reduces the usefulness of the letter stage correlations because finer correlations can be achieved using planktic forms the presence of larger foraminifera gives considerable environmental and palaeogeographic information

ages of subsurface stratigraphic intervals in the quaternary of enewetak atoll marshall islands abstract drill cores of enewetak atoll marshall islands reveal six stratigraphic intervals numbered in downward sequence which represent vertical coral growth during quaternary interglaciations radiocarbon dates indicate that the holocene sea transgressed the emergent reef platform by about 8000 yr b p the reef grew rapidly upward about 5 to 10 mm yr until about 6500 yr b p afterward vertical growth slowed to about 0 5 mm yr then lateral development became dominant during the last several thousand years the second interval is dated at 131 000 3000 yr b p by uranium series this unit correlates with oxygen isotope substage 5e and with terrace viia of huon peninsula new guinea and of main reef 2 terrace at atauro island the third interval is not dated because corals were recrystallized and it is tentatively correlated with either oxygen isotope stages 7 or 9 the age of the fourth interval is estimated at 454 000 100 000 yr b p from measured 234 u 238 u activity ratios this unit is correlated with either oxygen isotope stage 9 11 or 13

oxygen isotope calibration of the onset of ice rafting and history of glaciation in the north atlantic region we report here that dsdp site 552a cored with the hydraulic piston corer on the west flank of rockall bank recovered an undisturbed sequence of alternating white deep sea carbonate oozes and dark coloured layers that are rich in glacial debris oxygen isotope analysis of the sequence together with detailed nannofossil and palaeomagnetic stratigraphy shows that the first major horizon of ice rafting occurred at about 2 4 myr and was preceded by a minor pulse of ice rafting at about 2 5 myr the carbon isotope record shows that the site has been bathed by a water mass of similar characteristics to present day north atlantic deep water at least since 3 5 myr

chemical diagenesis in near surface zone above oil fields in geochemical exploration abstract hydrocarbon microseepages result in chemical and mineralogical changes in the near surface zone above oil reservoirs the results of geochemical research within the three oil fields of the west siberian basin demonstrate that chemical diagenetic processes lead to an increased inhomogeneity in chemical element distribution in soils subsoil atmosphere and snow pulse cathodoluminescence pcl study of soils and transmission electron microscopy tem study of micro and nanoparticles collected from the subsoil atmosphere showed that geochemical conditions over oil reservoirs were favorable for the enrichment of silicate and aluminosilicate minerals by chemical impurities chemical composition of micro and nanoparticles of metal compounds collected from within the vertical projection of the oil field outline suggested that these compounds were formed under intense reductive conditions that are not characteristic for the hypergene zone

integrated hyperspectral remote sensing geochemical and isotopic studies for understanding hydrocarbon induced rock alterations abstract the main objective of this work was to determine if there are characteristic mineral assemblages and chemical changes in areas affected by hydrocarbon microseepages for this purpose remote sensing was utilized for mapping surficial rock alterations and geochemical tools were used to understand the alteration processes the key area chosen for this type of work were altered and unaltered wingate sandstone outcrops in lisbon valley utah the spectral angle mapper method was applied on hymap hyperspectral data to classify the extent of altered and unaltered outcrops as well as to map the changes in mineral content within the outcrops the spectral feature fitting method was used to identify lithological changes in the area reflectance spectroscopy thin section studies major minor and trace element analyses and stable carbon and oxygen studies on both bleached altered and unbleached unaltered samples were successfully used to delineate areas of similar rock composition and relate changes due to hydrocarbons leaking from underlying petroleum reservoirs unbleached wingate sandstone samples had higher hematite and feldspar content than bleached wingate samples which were characterized by larger amounts of clay calcite and pyrite some bleached samples also had higher concentrations of elements u mo characteristic of hydrocarbon related reducing environments and were depleted in 13c when compared to the unbleached samples based on these results the following model of chemical reactions is suggested for diagnostic changes within wingate sandstone hydrocarbon induced reducing environment caused the transformation of sulfate ion obtained from groundwater or from oxidation of h2s to sulfide ion resulting in the reduction of hematite to pyrite the released hydrogen ion from this reaction reacted with available feldspars in the rock leading to precipitation of kaolinite these conditions favor the reaction between bicarbonate ion and ca2 ions that can be obtained from the groundwater leading to precipitation of calcite in pore spaces left open after the reduction and removal of hematite

cenozoic ice volume history development of a composite oxygen isotope record to view cenozoic ice volume and ocean temperature history a composite 18 o time series was constructed for tropical shallow dwelling planktonic foraminifers and for deep water benthic foraminifers we conclude that cenozoic benthic 18 o primarily reflect considerable deep ocean temperature variation and that tropical planktonic 18 o afford the best record of cenozoic ice volume the planktonic composite indicates the presence of a significant ice budget for the past 40 m y the difference between the benthic and planktonic 18 o composites suggests that low latitude production of warm saline bottom water dominated tertiary thermohaline circulation

evaluation of possible gas microseepage mechanisms petroleum microseepage anomalies over petroleum accumulations are commonly explained by rapid vertical migration of colloidal gas bubbles through fracture networks this article is a theoretical anal ysis of this mechanism and of continuous gas phase flow in frac tures the gas bubble ascent mechanism is much slower than re ported microseepage velocities so it cannot account for observed microseepage in contrast continuous gas phase flow through frac tures can equal or exceed reported microseepage velocity while maintaining total flux low enough so that petroleum accumulations can exist for geological lengths of time fracture entry pressure for bubbles is more than twice that of a continuous gas phase so con tinuous gas phase migration also requires a lower pressure threshold before initiating seepage vertical microseepage is therefore best explained by the same mechanism interpreted for macroseepage although this article provides a theoretically justified mecha nism for microseepage it also shows why interpretation of surface microseepage signals is problematic fracture geometry controls seepage velocity and flux so geochemical anomalies may indicate an increase in fracture aperture as well as possible subsurface ac cumulations larger fractures require very low gas capillary entry pressures so in some settings surface seepage could result from fractures over stratal migration pathways as well as over petroleum accumulations

isotopic composition of bank margin carbonates on midway atoll amplitude constraint on post early miocene eustasy the university of hawaii9s continuously cored borehole through the midway atoll coral cap provides a record of post early miocene eustasy subaerial exposure horizons are identified by light carbon isotope signatures and in some instances by lithologic criteria sea level highstands are recorded by aggradational units of reef sediment that are bounded by these subaerial exposure horizons sea level lowstands are constrained to fall no farther than a meteoric marine diagenetic boundary observed in the core this diagenetic boundary is defined by an offset in both oxygen and carbon isotope data light isotopic composition being indicative of intermittent meteoric diagenesis these data constrain the amplitudes of three post early miocene glacio eustatic sea level falls to be no more than 32 43 and 52 m absolute sea level elevations are estimated by constructing a subsidence model for midway atoll application of this analytic approach may provide amplitude constraints on eustasy elsewhere in the geologic record

soil containing rock fragments effects on infiltration abstract infiltration is a very complex process rock fragments affect infiltration by their presence in the soil matrix and on the soil surface procedures for quantifying soil and surface rock fragments are reviewed within the soil the physical properties and hydraulic properties that affect infiltration are shown to be influenced by rock fragments physical properties discussed are bulk density porosity and water content hydraulic properties that affect infiltration are water retention saturated conductivity and unsaturated conductivity rock fragments on the soil surface have been reported to both increase or decrease infiltration rates and amounts

strontium isotope stratigraphy of enewetak atoll sup 87 sr sup 86 sr ratios determined for samples from a 350 m core of neogene lagoonal shallow water limestones from enewetak atoll display a remarkably informative trend like the recently published data for deep sea drilling project dsdp carbonates sup 87 sr sup 86 sr at enewetak increases monotonically but not smoothly from the early miocene to the pleistocene the data show intervals of little or no change in sup 87 sr sup 86 sr punctuated by sharp transitions to lower values toward greater core depths the sharp transitions correlate with observed solution disconformities caused by periods of subaerial erosion whereas the intervals of little or no change in sup 87 sr sup 86 sr correspond to intervals of rapid accumulation of shallow water carbonate sediments when converted to numerical ages using the published dsdp 590b trend the best resolved time breaks are at 282 m 12 3 to 18 2 ma missing and 121 6 m 3 0 to 5 3 ma missing below the lagoon floor at enewetak sr isotopes offer a stratigraphic resolution for these shallow marine neogene carbonates comparable to that of nannofossil zonation in deep sea carbonates 0 3 3 m y in addition the correlation of times of sr isotope breaks at enewetak with times of rapid sr isotope change in the dsdp 590b samples confirms the importance ofmore sea level changes in the evolution of global marine sr isotopes and shows that the sr isotope response to sea level falls is rapid less

the effect of rock fragment size and position on topsoil moisture on arid and semi arid hillslopes abstract rock fragments on arid hillslopes affect rainwater redistribution and overland flow through various hydrological processes the present study focuses on the evolution of topsoil moisture content under rock fragments following rain events measurement was taken under rock fragments in various sizes large and small and positions on top of the soil surface and partially embedded within the soil surface at north and south facing hillslopes in arid and semi arid areas the main findings 1 the topsoil moisture content under rock fragments was higher over time than that of bare soil areas 2 rock fragments affect the topsoil moisture content for a longer time in semi arid areas than in arid areas and 3 large rock fragments and partially embedded ones are favorable micro environments for accepting and retaining rainwater and overland flowing water this may have eco geomorphic implications regarding the mosaic like patterns of source and sink areas on arid hillslopes

effects of rock fragments on infiltration and evaporation in hilly purple soils of sichuan basin china this paper presents the results of laboratory experiments showing the effects of rock fragments contained in three different purple soils of the sichuan basin of southwest china the experiments investigated how these rock fragments alter the soil s physical chemical and agronomical characteristics such as infiltration and evaporation we found that the infiltration rate whether horizontal or vertical in the three soils has the following order gray brown purple soil reddish brown purple soil brown purple soil with increasing rock fragment contents the accumulated infiltration decreases while the total time decreases first and then increases the minimum occurs at approximately 10 20 of fragment content by weight the infiltration rate also changes with the distance in the 0 5 cm range the initial infiltration rate increases with increasing rock fragment contents while in the 5 10 cm range the slope of infiltration curve increases with increasing rock fragment contents with increasing distance the slope gradually decreases and finally reaches a stable value the presence of rock fragments reduces soil water content the minimal value appearing when the rock fragments were on top of the soil column soil rock sample decreasing with increasing rock fragments for other samples mixed with fragments under the constant 40 c temperature the accumulated evaporation and evaporation rate are minimal for soils covered by rock fragments and the accumulated evaporation decreases with increasing rock fragment for other soil samples however the evaporation rate increases with increasing rock fragments in the first 4 days and decreases thereafter

field experiments on the transport of rock fragments by animal trampling on scree slopes qualitative observations in an area with steep scree slopes in turkey suggested that trampling by goats and sheep may contribute significantly to the downslope movement of rock fragments in these environments therefore a series of field experiments was set up to determine the rate of rock fragment transport caused by trampling the experimental results allowed the calculation of a unit displacement distance from each trampling experiment which may then be used to extrapolate the measured transport rates over longer time periods and larger areas although such extrapolations should be interpreted with great caution the results demonstrate that trampling contributes significantly to rock fragment transport in such environments as calculated yearly displacement distances are equal to or higher than those reported in the literature for other geomorphic processes the observed travel distance distributions are not well described by a negative exponential distribution trampling causes a weak downslope sorting the coarsest clasts move farther but has a significant effect on vertical sorting and is one of the factors which can explain the layered structure of the scree slopes in the area

mineralogy and geochemistry of alteration induced by hydrocarbon seepage in an evaporite formation a case study from the zagros fold belt sw iran abstract leaking hydrocarbon and associated fluids produce a reduced environment which initiates diagenetic reactions in the rocks and soils overlying hydrocarbon reservoirs this article introduces mineralogical and geochemical alterations induced by hydrocarbon seepages in the gachsaran evaporite formation masjed soleiman zagros folded belt sw iran using various geochemical methods x ray diffraction xrd analysis revealed two dominant groups of mineralogical changes in the anomalous zone including 1 spotty occurrences of jarosite natroalunite and sulfur 2 simultaneous decrease of sulfate and increase of carbonate the 13c values of carbonate phases vary between 8 9 and 32 3 which support a partial contribution of hydrocarbon in these phases ph measurements of rock samples indicated that hydrocarbon seepage causes decrease of ph though not very significantly however ph in areas that show ongoing sour hydrocarbon seepage among rarely pure gypsum beds decrease to 0 09 which produces acid sulfate soil trace element concentrations indicated that cr co ni v cd u cu and zn increase in various patterns around the hydrocarbon seepages excepting the areas with very low ph

oligocene to holocene hydrocarbon migration and salt dome carbonates northern gulf of mexico abstract the geochemistry and geology of damon mound salt dome in brazoria county texas provides an insight to the timing of hydrocarbon migration and carbonate caprock development in the houston salt dome province reservoir rocks flanking the salt dome received a charge of crude oil from deeply buried eocene source rocks during early oligocene early miocene time the light 13c of the carbonate caprock at damon mound 24 8 to 31 7 pdb is consistent with an origin from bacterial oxidation of crude oil with similar 13c 27 1 to 28 8 pdb a minimum weight estimate of carbonate caprock at damon mound is 32 7 106 metric tons suggesting bacterial oxidation of about 34 2 106 barrels of crude oil to form the carbonate late oligocene early miocene erosional exposure of the carbonate caprock provided a hard substratum to initiate the development of a coral reef in an otherwise unfavourable mud dominated environment although the bulk of the reef carbonate displays normal marine 13c some late carbonate cements show light 13c values 22 1 to 29 6 from bacterial hydrocarbon oxidation buried carbonate caprocks and coral reef facies serve as carbonate reservoir rocks over gulf of mexico salt domes lending support to the hypothesis that intense hydrocarbon oxidation can in itself give rise to some carbonate reservoir rocks ongoing hydrocarbon migration from deeply buried cretaceous source rocks and the development of embryonic carbonate caprocks over shallow salt domes on the present gulf of mexico continental slope offer analogies and contrasts to the processes that gave rise to carbonates at damon mound in the geological past

recent hydrocarbon alteration sulfate reduction and formation of elemental sulfur and metal sulfides in salt dome cap rock abstract geochemical analysis of hydrocarbons and scanning electron microscopy sem provide insight to recent alteration of crude oil microbial sulfate reduction and mineral deposition in carbonate cap rock at damon mound brazoria county texas u s a previous work showed that intense aerobic biodegradation of hydrocarbons occurs in shallow cap rock where s 0 and metal sulfides are not abundant the present study focuses on some deeper carbonate cap rock characterized by more limited oxygen availability the c 1 c 4 hydrocarbons in deeper cap rock are a biodegraded residue of hydrocarbons derived from crude oil alteration of higher molecular weight crude oil components is best explained by the effects of water washing accompanied by some biodegradation sem of cavities in carbonate cap rock shows microbes in association with globular masses of solid crude oil and sulfate minerals late forming minerals in cavities include s 0 pyrrhotite pyrite sphalerite and aragonite the presence of s 0 and sulfide minerals indicates that microbial sulfate reduction is associated with limited hydrocarbon biodegradation in this deeper cap rock environment similar processes could explain the origin of some s 0 and metal sulfides at damon mound in the geologic past

an integrated interpretation for the origin of the patrick draw oil field sage anomaly 1 the patrick draw oil field has been the site of research into surface and remote sensing methods for hydrocarbon exploration for nearly 10 yr the oil field is a stratigraphic trap with conspicuous sage vegetation on the surface and an associated tonal anomaly within that sage visible via landsat overlying the field s gas cap this paper attempts to resolve the controversy of whether the patrick draw sage anomaly is related to oil field factors or to other independent factors geology and production history of the field show the sage die out anomaly results from upward migration of injected gases and waters used to maintain reservoir pressures in the field these gases and waters produced anoxic low eh oxidation potential high ph and high salinity soils that are toxic to the overlying sage population stunted sage associated with the anomaly commonly occurs in marginal terrains in the western united states and is not tied uniquely to oil fields a velocity for the seeping gases of 250 1000 ft yr 76 305 m yr was calculated from the reservoir to the surface failure to account for the lag time associated with movement of seepage to the surface has been a source of misinterpretation

the record of pliocene sea level change at enewetak atoll abstract detailed seismic stratigraphy lithostratigraphy and chemostratigraphy indicate that atoll wide subaerial exposure surfaces major disconformities developed during major sea level lowstands form prominent seismic reflectors and are coincident with biostratigraphic breaks in the plio pleistocene on enewetak atoll sea level models based on the stratigraphic position and age of major disconformities suggest a maximum sea level highstand elevation of 36 m above present sea level and a maximum sea level lowstand elevation of 63 m below present sea level for the pliocene

origin of carbonate cemented beds on the naglfar dome voring basin norwegian sea abstract lower eocene sediments cored north in the voring basin include calcite cemented beds with unusual microstructures the origin of these beds has been interpreted on the basis of optical microscopy sem microprobe analyses and stable isotope analyses the calcite cement includes perfect pseudomorphs of vesicular ash and lapilli and a few micro sized 0 1 mm remains of unaltered sideromelane were discovered the sideromelane has the composition of relatively alkali rich tholeiitic basalt similar to lower eocene plagioclase basalt from dsdp site 342 on the voring marginal high the earliest phase of diagenesis in the marine environments was associated with palagonitisation and glauconitisation of volcanic glass and growth of smectite and zeolites an early diagenetic origin is also inferred for the more extensive growth of calcite and pyrite cement stable isotope analyses of the calcite cement show very light 13 c values between 55 and 28 4 and with the largest negative values in beds with pseudomorphic textures after ash lapilli such low 13 c values are consistent with a carbon source associated with oxidation of methane within the upper levels of the sediment body close to the sediment water interface the metastable basalt glass acted as a source for ca 2 and fe 2 ions required for calcite and pyrite growth whereas sulphur for pyrite formation may have been supplied from accompanying sulphate reduction the combined occurrence of volcaniclastic deposits and methane seepage as documented in the voring basin may have implications for more widespread formation of calcite cemented beds in the offshore tertiary sediments

hydrocarbon microseepage related geobotanical analysis in and around oil fields hydrocarbon microseepage can be detected by its altering effect on rocks soils and overlying vegetation this study examines the impact of hydrocarbon seepage on vegetation microseeping hydrocarbons alter soil chemistry often creating an environment that can impact the health of overlying vegetation these effects can be observed using remote sensing blackburn and eagle springs oil fields in nevada patrick draw and little buffalo basin oil fields in wyoming and cement oil field in oklahoma were selected for this study because previous investigations confirmed the presence of microseeping hydrocarbons in these locations in this study moderate resolution imaging spectroradiometer s modis monthly average normalized difference vegetation index ndvi data from january 2003 to december 2012 were used to observe vegetation health inside oil fields average ndvi was calculated for these locations the typical range of ndvi in desert environments such as those observed in semi arid desert environments

rock fragments in top soils significance and processes this introductory paper reviews various aspects of rock fragments in top soils such information is required for various reasons and in particular for predicting the impact of climatic or landuse changes on the response of these soils particular attention is paid to the definition and measurement of rock fragment content in top soils the density of soils containing rock fragments the spatial distribution and movement of rock fragments in top soils the effects of rock fragments on some key hydrological processes thermal properties of top soils physical soil degradation soil erosion and soil productivity

cold water coral banks and submarine landslides a review this paper aims to review the relation between cold water coral bank development and submarine landslides both are common features on continental margins but so far it has not been reviewed which effect if at all they may have upon each other indirect and direct relations between coral banks and landslides are evaluated here based on four case studies the magellan mound province in the porcupine seabight where fossil coral banks appear partly on top of a buried slide deposit the sula ridge reef complex and the storegga landslide both off mid norway and the mauritania coral bank province associated with the mauritanian slide complex for each of these locations positive and negative relationships between both features are discussed based on available datasets locally submarine landslides might directly favour coral bank development by creating substratum where corals can settle on enhancing turbulence due to abrupt seabed morphological variations and in some cases causing fluid seepage in turn some of these processes may contribute to increased food availability and lower sedimentation rates landslides can also affect coral bank development by direct erosion of the coral banks and by the instantaneous increase of turbidity which may smother the corals on the other hand coral banks might have a stabilising function and delay or stop the headwall retrogradation of submarine landslides although local relationships can be deduced from these case studies no general and direct relationship exists between submarine landslides and cold water coral banks

the history of post miocene sea level change inferences from stratigraphic modeling of enewetak atoll the history of post miocene sea level change has been investigated using a quantitative one dimensional stratigraphic forward model the stratigraphic model produces synthetic stratigraphies including mineralogy and sediment age versus depth in response to changes in sea level subsidence sedimentation and diagenesis model outputs using sea level curves inferred from passive margin sequence stratigraphy and deep sea foraminiferal oxygen isotope stratigraphy were compared to the post miocene stratigraphy of enewetak atoll modeling results support high frequency 104 to 105 years fluctuations of post miocene sea level post miocene sea level elevations significantly greater than modern sea level elevation are not easily reconciled with the stratigraphy of enewetak atoll model data fit is maximized when a rapid subsidence rate for enewetak atoll is used alternatively model data fit may be maximized using a lower subsidence rate for enewetak and having post miocene sea level elevations significantly lower than modem sea level elevation given the present state of knowledge much work is still needed to accurately decipher the record of post miocene sea level change

conceptual modeling of onshore hydrocarbon seep occurrence in the dezful embayment sw iran petroleum and gas seeps on the ground surface are direct indicators of accumulations of hydrocarbons in the subsurface and could reflect the migration of hydrocarbons in a sedimentary basin quantitative analyses of the spatial pattern of hydrocarbon seeps and their spatial associations with geological features could aid in deducing geological controls on their occurrence in this study the fry analysis was applied to study the spatial pattern of mapped hydrocarbon seeps whereas spatial association analyses were implemented to quantify the spatial association of mapped seeps and their alteration products with geological features the spatial pattern analysis of hydrocarbon seeps showed that oil seeps followed prominent nw se and ne sw trends while gas seeps followed nw se and n s trends suggesting that nne ssw and nw se fractures are possible migration pathways for hydrocarbons to reach the surface the results of the spatial association analysis illustrated strong positive spatial associations of oil and gas seeps with the gachsaran and the mishan formations implying upward migration of hydrocarbons through permeable micro fractures and micro pores in their strata a conceptual model has proposed for the occurrence of onshore hydrocarbon seeps in the dezful embayment

do carbonate reefs form due to fluid seepage buried carbonate reefs are favoured hydrocarbon prospecting targets mainly due to their high porosity and potential for containing large quantities of petroleum the question of the true relationship between reef structure and the internally trapped fluids hydrocarbons is here raised as one of cause and effect in other words which came first the hydrocarbons or the carbonate reef itself modern bioherms and seabed carbonate reefs in amongst other locations the north sea and the gulf of mexico are shown to form in close association with active hydrocarbon seepages mainly based on results from ecological studies at deep ocean vent communities a new model for carbonate reef formation is promoted that such reefs form at locations containing high concentrations of bacteria and other microorganisms suspended in the water column as a result of seeping fluids solutions and gases that provide some of the energy basis and carbon source for ecosystems independently of photosynthesis therefore on burial and effective sealing capping these carbonate reefs become hydrocarbon reservoirs trapping and accumulating the very minerals on which they in the first place were dependent

late cenozoic sea level and the rise of modern rimmed atolls this paper is not subject to u s copyright the definitive version was published in palaeogeography palaeoclimatology palaeoecology 451 2016 73 83 doi 10 1016 j palaeo 2016 03 018

variation of rock fragment cover and size along semiarid hillslopes a case study from southeast spain abstract the spatial variation of rock fragment cover rc and rock fragment size rs along semiarid hillslopes and transects in the mediterranean is largely controlled by hillslope gradient total rock fragment cover rc 5 mm often increases in a convex upward curve with hillslope gradient while the d50 of the surface rock fragments 5 mm increases linearly with hillslope gradient on south facing slopes rc 5 mm is slightly higher than on north facing slopes lithology controls the size distribution of the stone pavement rather than its cover percentage spatial variation of rock fragment cover reflects spatial variation in past erosion and deposition rates hillslope sections that are steep south facing or have been abandoned a long time ago have undergone intense interrill and rill erosion and thus have high rock fragment covers tillage erosion leads to high rock fragment covers on convex hillslopes in intensively cultivated areas thus using information on hillslope gradient aspect lithology and landuse we have been able to describe the spatial variation of rock fragment cover and size along semiarid hillslopes in southeast spain such information is crucial for understanding and modelling the spatial variation of the hydrological and erosion response of semiarid hillslopes under environmental change especially in semiarid environments of the mediterranean where vegetation cover is predicted to decrease due to climatic or landuse changes and rock fragments at the surface become the only soil surface stabilisers

role of diffusion in primary migration of hydrocarbons the following effective diffusion coefficients d cm2 sec were determined for the diffusion of light hydrocarbons through the water saturated pore space of shales methane 2 12 10 6 ethane 1 11 10 6 propane 5 55 10 7 iso butane 3 75 10 7 n butane 3 01 10 7 n pentane 1 57 10 7 n hexane 8 20 10 8 n heptane 4 31 10 8 and n decane 6 08 10 9 on the basis of these new data a deterministic dynamic model was set up to simulate the diffusive transport of light hydrocarbons c1 to c10 from source rocks for eight documented source rock units representing a wid range of geologic conditions maturities of 0 40 to 1 35 mean vitrinite reflectance oil to gas prone kerogens the cumulative amounts of hydrocarbons escaping with time were calculated thus it was shown that diffusion represents an effective process for primary migration of gas but not for oil the rate of mass transport for gas from source rocks with geologic time can be sufficiently high to account for the origin of commercial size gas fields for example a cumulative amount of 109 kg of methane 1 5 109 std m3 or 5 3 1010 scf has escaped by diffusion in 540 000 years from a certain volume 1 000 km2 by 200 m thick of a high mature gas prone mesozoic source rock in western canada the origin of hydrocarbon accumulations with high gas to oil ratios in low mature sediments in geologically young basins early gases and condensates can be explained by an early phase of primary migration predominantly based on diffusion during the initial stages of the accumulation history of those fields extending up to millions of years under certain conditions the reservoir gas changes with geologic time from a methane rich to a wet gas composition at low maturity levels below about 0 6 rm even oil prone source rocks yield methane rich light hydrocarbon mixtures by migration through diffusion compositional trends among reservoir gases of several multiple pay gas fields in louisiana represent evidence for diffusive transport of hydrocarbons the variation in gas composition between the individual pay zones is controlled by increasing distances of diffusive transport of the hydrocarbons from a uniform source rock at depth to their present accumulation sites in the shallow pay zones compounds of high diffusivity are enriched for example in the sligo gas field of louisiana the methane ethane and the iso butane n butane ratios increase from 10 2 to 36 0 and from 0 86 to 1 13 respectively from the deepest to the shallowest of the five productive reservoir sands which are spread over a a depth interval of 5 500 ft 1 676 m diffusion of light hydrocarbons in the subsurface can also have economically adverse effects for example existing gas accumulations can be destroyed by dissipation the rate of this destruction was calculated for the harlingen gas field holland by diffusive loss through 400 m of shale cap rock the initial amount of methane in place of 1 93 109 std m3 6 8 1010 scf is reduced by one half over a period of 4 5 million years this leads us to propose the concept that large gas accumulations can persist through extended periods of geologic time only as dynamic systems reaching some kind of steady state equilibrium between diffusive loss through the cap rock and continuous replenishment from the source rock

post miocene diagenetic and eustatic history of enewetak atoll model and data comparison the post miocene diagenetic and eustatic history of enewetak atoll was investigated using a one dimensional forward model comparison of model and data suggests that the post miocene history of enewetak atoll was dominated by multiple episodes of meteoric phreatic diagenesis attendant with high frequency 10 sup 4 to 10 sup 5 yr fluctuations in sea level and a subsidence rate of 39 0 m m y sensitivity testing indicates that subaerial erosion results in the preservation of additional subaerial unconformities because stratigraphic shortening permits a succeeding sea level rise to flood the exposure surface and deposit sediment whereas without subaerial erosion this sea level rise would be recorded as a paleophreatic lens model results indicate that less then 10 of lapsed time is recorded by sediment deposition during periods of high frequency changes in sea level incompleteness of the stratigraphic record suggest that magnetostratigraphy may give erroneous ages for shallow marine carbonate sequences deposited during times of high frequency changes in sea level and frequent magnetic polarity reversals

characterization of microseepage induced diagenetic changes in the upper red formation qom region iran part ii a new insight using reflectance spectroscopic analysis abstract the classic microseepage model supports the notion that hydrocarbon pools leak to the surface over time and trigger an array of diagenetic physicochemical and mineralogical changes in the overlying sediments mapping the induced alteration mineralogy for microseepage targeting has been an appealing yet ambiguous practice mostly because of our incomplete understanding of the diversity of changes occurring in the environment to close this gap an integrated spectroscopic approach is adopted here to investigate the variability quantity and physicochemistry of diagenetic minerals induced by active microseepage systems over the alborz oil reservoir in the qom region iran the area includes an effectively sealed carbonate reservoir overlain by thick oligocene sediments of the upper red formation a large suite of samples collected from microseepage affected zones was spectrally characterized in the 350 2500 nm wavelength region and then statistically contrasted against unaffected samples gathered from a nearby control area the analysis reveals a novel array of mineralogic indicators for microseepage systems it indicates that smectites montmorillonite nontronite al rich mixed layer illite smectite fe rich chlorite and traces of palygorskite constitute the clay alterations this array is associated with the enrichment of k2o and loss of na2o and mgo from the system as indicated by x ray fluorescence measurements in the arid climate of the region the iron rich red beds fe2o3 6 are only moderately bleached and thus the subsequent chemical weathering of the relict irons has triggered goethite al poor and likely ferrihydrite and maghemite precipitation consequently besides the typical ferric iron bleaching the modification in the mineralogy of iron oxides oxyhydroxides marked by a shift in the absorption minimum at 900 nm is suggested as an additional indicator of microseepage systems fe chlorites constitute the dominant ferrous mineral present in the environment the affected strata are also associated with prevalent calcite and gypsum cements and occasionally jarosite occurrences based on the silica contents of the host rock the microseepage induced alterations are classified into two categories namely felsic and mafic wherein the latter is typified by the assemblages described here this study provides new insights into microseepage induced alterations and highlights the significance of reflectance spectroscopic techniques in facies determination and the alteration footprints mapping of onshore microseepage systems

concentrated flow erosion rates as affected by rock fragment cover and initial soil moisture content abstract concentrated flow experiments using a small hydraulic flume and a constant flow discharge and bed slope have been conducted in order to investigate the effects of rock fragment cover rc on sediment yield for an initially wet and an initially air dry loamy topsoil the experimental results indicate that rc reduces concentrated flow erosion rates e in an exponential way i e e e brc which is similar to previously reported relations for other water erosion processes such as interrill erosion and sheet rill erosion measured on runoff plots the decay rate b of this exponential relationship increased throughout the experiments because of scour hole development and bed armouring the concentrated flow erosion rates and b values also depend on the initial moisture content of the topsoil depending on rc mean concentrated flow erosion rates were 20 to 65 less on initially wet compared to initially air dry topsoils the mean value for b was 0 032 for the initially wet but only 0 017 for the initially air dry topsoil indicating that a rock fragment cover is less efficient in reducing concentrated flow erosion rates when the topsoil is initially air dry than when it is initially wet the results help explain the data scatter in reported relationships between rc and interrill rill erosion rates they also indicate that a given surface rock fragment cover will offer more protection to wet topsoils than to dry topsoils which are very common in mediterranean environments event based water erosion models should incorporate effects of antecedent soil moisture content as well as those of rc on concentrated flow erosion rates

relationships between seepage tectonics and subsurface petroleum reserves abstract the relationship between visible petroleum seepage and commercial subsurface reserves has been investigated by a study of the distribution of documented seeps in south east asia this is accompanied and integrated with a broader global study the intensity of flowing seepage is controlled largely by present day tectonics and by the timing of petroleum migration when such influences are reduced by isolating sets of tectonically similar basins correlations are found between numbers of seeps and basin reserves at a sub basinal scale seeps are observed to concentrate over tectonic features such as active diapirs active faults and uplifted basin margins it is relatively rare for seeps to directly overlie major fields although many seeps may be linked to downdip accumulations by long tortuous paths the best seep accumulation relationships are observed in active compressional and diapiric settings particularly those involving shallow reservoirs seeps are rare where traps are buried beneath thick undisturbed overburdens the prime value of visible seeps in most frontier basins lies at the regional level in the clues they give to the nature extent and quantitative hydrocarbon potential of a basin s source system

high eustatic sea level during the middle pliocene evidence from the southeastern u s atlantic coastal plain the middle pliocene approximately 3 5 2 5 ma was a period of global warmth preceding the growth of major northern hemisphere ice sheets the authors report on eustatic sea level for the middle pliocene based on microspaleontologic study of marine deposits of the duplin formation of south carolina and north carolina the duplin was deposited during a middle pliocene marine transgression that formed the orangeburg scarp a prominent wave cut geomorphic paleoshoreline of the southeastern u s atlantic coastal plain they concluded that 1 the scarp in south carolina was formed mostly during the middle pliocene 3 5 3 0 ma 2 eustatic sea level was about 35 plus minus 18 m higher than modern sea level the scarp has been uplifted about 50 65 m since the middle pliocene and 3 ocean water temperatures along eastern north america were warmer when the scarp was formed that they are at present

remote sensing and geochemistry for detecting hydrocarbon microseepages this work tests the hypothesis that chemical and mineralogical alterations in rocks and soils are related to hydrocarbon microseepages above some of the major oil fields in this study we used hyperion hyperspectral imaging sensors to map alterations that appear to be associated with hydrocarbon microseepages in the patrick draw area of wyoming our mineralogical geochemical and carbon isotope data support the presence of hydrocarbon microseepages satellite imagery training classifications defined by areas of hydrocarbon microseepage have resulted in the successful identification of the areal extent of an anomalous area geochemical characteristics of samples that define this anomalous area were then compared to the remaining non anomalous samples using x ray diffraction xrd reflectance spectroscopy and carbon isotope techniques xrd analyses demonstrated the increased presence of feldspars in non anomalous samples compared to anomalous samples spectroscopy results demonstrated higher proportions of clays within the anomalous samples compared to non anomalous samples the 13 c values range from 2 88 to as low as 45 32 indicating hydrocarbon sources these methods may provide a foundation upon which further hydrocarbon exploration techniques can develop

the potential use of biogeochemistry in the detection of petroleum microseepage biogeochemistry was applied to the indirect detection of petroleum microseepage in the vicinity of eagle springs oil field railroad valley nevada and cave canyon field paradox basin utah trace elements were measured in native vegetation over and surrounding areas of production at the test sites the oxidation of microseepage in the upper part of the soil column is postulated to cause an increase in plant uptake of transition trace elements such as iron manganese and vanadium and a decrease in plant uptake of alkaline earth elements such as calcium strontium and barium compared to nonproductive areas an increase in uptake of transition trace elements and a decrease in alkaline earth elements was observed in fourwing saltbush over eagle springs field the postulated increase in uptake of transition trace elements and decrease in alkaline earth elements was not as apparent in big sagebrush nor in utah juniper over the cave canyon field the observation of the postulated effects on vegetation at eagle springs may be due to the relatively large rates of microseepage independently observed using other methods and the extensive faulting in railroad valley the weaker response observed at cave canyon may reflect the lack of faulting and the retention of light hydrocarbons in the reservoir another possible reason for weak response is that the available plant species at cave canyon do not exhibit the effect at the lower soil ph measured in the area at low ph and low eh the solubility of transition elements in soil pore waters and plant uptake is increased due to the high soil ph of the railroad valley area the uptake of alkaline earth elements should be decreased where microseepage is occurring because of crystallizat on of carbonate minerals

paleoceanographic implications of miocene deep sea hiatuses miocene paleoceanographic evolution exhibits major changes resulting from the opening and closing of passages the subsequent changes in oceanic circulation and development of major antarctic glaciation the consequences and timing of these events can be observed in variations in the distribution of deep sea hiatuses sedimentation patterns and biogeographic distribution of planktic organisms the opening of the drake passage in the latest oligocene to early miocene 25 20 ma resulted in the establishment of the deep circumpolar current which led to thermal isolation of antarctica and increased global cooling this development was associated with a major turnover in planktic organisms resulting in the evolution of neogene assemblages and the eventual extinction of paleogene assemblages the erosive patterns of two widespread hiatuses ph 23 0 22 5 ma and nh 1 20 18 ma indicate that a deep circumequatorial circulation existed at this time characterized by a broad band of carbonate ooze deposition siliceous sedimentation was restricted to the north atlantic and a narrow band around antarctica a major reorganization in deep sea sedimentation and hiatus distribution patterns occurred near the early middle miocene boundary apparently resulting from changes in oceanic circulation beginning at this time deep sea erosion occurred throughout the caribbean hiatus nh 2 16 15 ma suggesting disruption of the deep circumequatorial circulation and northward deflection of deep currents and or intensification of the gulf stream sediment distribution patterns changed dramatically with the sudden appearance of siliceous ooze deposition in the marginal and east equatorial north pacific by 16 0 to 15 5 ma coincident with the decline of siliceous sedimentation in the north atlantic this silica switch may have been caused by the introduction of norwegian overflow water into the north atlantic acting as a barrier to outcropping of silica rich antarctic bottom water the main aspects of the present oceanic circulation system and sediment distribution pattern were established by 13 5 to 12 5 ma hiatus nh 3 coincident with the establishment of a major east antarctic ice cap antarctic glaciation resulted in a broadening belt of siliceous ooze deposition around antarctica increased siliceous sedimentation in the marginal and east equatorial north pacific and indian oceans and further northward restriction of siliceous sediments in the north atlantic periodic cool climatic events were accompanied by lower eustatic sea levels and widespread deep sea erosion at 12 to 11 ma nh 4 10 to 9 ma nh 5 7 5 to 6 2 ma nh 6 and 5 2 to 4 7 ma nh 7

spatial distribution of rock fragments in dolines a case study in a semiarid mediterranean mountain range sierra de gador se spain abstract rock fragments rfs at the soil surface have great effects on the intensity of various hydrologic and geomorphic processes however little information is available on the spatial distribution of rock fragments rf in the dolines which may be of importance in understanding overland flow and subsequent recharge in limestone karst landscapes this study analysed spatial variability of rf cover and size in different topographic positions top upper middle and lower position in three dolines in sierra de gador almeria province south east spain the results indicated that cover percentage of small rfs 5 20 mm increased but large rf cover 250 600 mm and 600 mm decreased from the upper position to the lower position of the dolines small rfs were usually resting on the soil surface while most large rfs tended to be partly embedded in the soil surface total rf cover and d 50 median diameter of the surface rfs greater than 5 mm tended to increase with slope gradient

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

model for hydrocarbon microseepage and related near surface alterations despite recent advances in surface and near surface geochemical methods there continues to be a need for improved understanding of the scientific basis relating these methods to petroleum deposits we have reviewed the literature pertinent to the several methods we have used and integrated that information with some 100 man years of our experience to contribute to that end evidence indicates that hydrocarbon micro seepage from reservoirs most probably involves buoyant colloidal size microbubbles of light hydrocarbons principally methane through the butanes ascending relatively rapidly through a water filled network of fractures joints and bedding planes bacterial consumption of these hydrocarbons creates carbon dioxide and hydrogen sulfide which may alter sediments producing detectable modifications in geomorphic seismic magnetic and radiometric properties we have used combinations of 1 airborne microwave sensing and laboratory analyses of soil gas hydrocarbons 2 shallow source aeromagnetic and soil magnetic susceptibility measurements 3 aerial and surface gamma ray measurements and 4 geomorphology to find productive oil and gas deposits results suggest that using these methods can substantially increase the probability of wildcat success and reduce finding costs in selected geologic settings however these surface methods cannot reveal depth size or quality of reservoirs or even if producible hydrocarbons will be found

the effects of coal gangue and fly ash on the hydraulic properties and water content distribution in reconstructed soil profiles of coal mined land with a high groundwater table soil water systems have been severely degraded in coal mined and subsiding land where a shallow groundwater table is also present the present paper discussed the effects of fly ash fa and coal gangue cg as filling materials on the hydraulic properties and water content distribution in a profile for the purpose of rehabilitating subsided lands the saturated water content water characteristic curve and water diffusivity of local soil fa cg and a mixture of fa and cg mixed filling were characterized a column experiment was conducted to investigate the changes of water content in profiles reconstructed from the combination of soil and filling materials including soil only fa cg and a mixture of fa and cg which were used to fill the lower part of the reconstructed profile the mixture of fa and cg was found to possess similar hydraulic properties to those of the soil particularly high water holding capacity and permeability moreover the volumetric water contents in the whole profile containing the mixture of fa and cg were consistent with those of the profile reconstructed with soil only as a result it is recommended to adopt the mixture of fa and cg for reconstructing the lower profile of the land to alleviate or rehabilitate subsided land in coal mines

variation of gypsum morphology along deep core sg 1 western qaidam basin northeastern tibetan plateau and its implication to depositional environments abstract the qaidam basin is an arid closed intermontane basin located on the northern margins of the tibetan plateau in china a 938 5 m long core sg 1 dated between 2 8 ma 0 1 ma was obtained from the western qaidam basin gypsum is one of major evaporative minerals in the core a total of 201 gypsum samples were selected and their crystal morphologies were carefully investigated the crystal habits are lenticular prismatic tabular twinned stubby and aggregate prismatic crystals occur in the upper 723 m while lenticular crystals exist almost entirely in the upper 523 m tabular crystals are the most common morphology the total abundance of gypsum crystal including tabular lenticular and prismatic forms tends to increase with decreasing depth the relationship between crystal habits and depositional environments is complex because same morphology can appear in different environments and different morphologies can also occur in the same depositional environment however the occurrence of different morphologies can be attributed to the variable growth rates caused by the inhibition effect of additional cations e g mg 2 na k and sr 2 on particular lattice parameters and the variation in precipitation experiments the lattice parameters of the unit cell of gypsum measured by x ray diffraction method are a 5 854 12 57 a b 9 654 16 231 a and c 5 163 14 024 a 113 54 119 88 volume 601 55 712 65 a 3 the substitution of k na and mg 2 for ca 2 can reduce c axis while sr 2 can reduce a and b axes a c b c a b tend to increase with k na and mg 2 and decrease with sr 2 the mg 2 na k and sr 2 contents in gypsum show significant variability with k ca molar ratios varying from 1 03 10 4 to 32 08 10 4 mg ca molar ratios from 0 0023 to 0 1629 na ca molar ratios from 0 031 to 0 575 and sr ca molar ratios from 5 59 10 4 to 19 67 10 4 sr 2 mg 2 na and k concentrations in gypsum mainly depend on growth rate and brine concentration

conservation of soil moisture by different stone covers on alpine talus slopes lassen california abstract this study reports on the influence of stone covers with different clast sizes on the soil moisture of alpine talus slopes in lassen california fifteen four plot sets were sampled in the dry season july 1990 in sandy areas and in talus covered with pebbles cobbles or blocks between 2740 and 2775 m three depths 0 5 5 10 10 15 cm were sampled field moisture content increased gradually with depth in all soil profiles and also in plots covered by increasingly larger rocks surface soils in sand areas were very dry but under rocks had water contents 6 to 14 times greater differences among plots decreased with depth but subsoil samples in sand were still drier than those beneath any stone cover at similar depths blocks were most effective in conserving moisture water content below them was higher than even in deep 10 15 cm sand soils soil temperatures were recorded in sand and under blocks for an 11 day period minima were not significantly different but average maxima were 5 6 c lower under blocks than in sand which reached highs 4 4 c lower than the air differences in soil moisture among talus types are ascribed to lower evaporation losses under stones due to both disruption of capillarity by the coarse particles which prevented water flow to the talus surface and to their efficient reduction of maximum temperatures an irrigation experiment was conducted at 2110 m on a steep talus on the chaos crags from july 18 to aug 2 1993 four 100 75 cm plots with the same surface types than at lassen received 22 5 mm water moisture content was then periodically sampled watering produced similar water distributions among soil depths and talus types to those in lassen evaporation occurred quickly in bare soils due to high air and soil temperatures the sand surface was already dry 2 days after watering but stone covered plots remained moist until day 15 when soils under blocks still retained 77 97 of the water content percent by weight at the start of the test

neogene biostratigraphy and paleoenvironments of enewetak atoll equatorial pacific ocean abstract micropaleontologic analyses of neogene sediments from enewetak atoll marshall islands provide data on the age of lagoonal deposits stratigraphic disconformities and the paleoenvironmental and subsidence history of the atoll benthic foraminifers planktic foraminifers calcareous nannofossils and ostracodes were studied from six boreholes the deepest penetrating 1605 feet below the lagoon floor into upper oligocene strata the oligocene miocene boundary occurs at about 1200 ft below the lagoon floor the early and middle miocene is characterized by brief periods of deposition and numerous hiatuses ostracodes and benthic foraminifers indicate a shallow marine reefal environment with occasional brackish water conditions upper miocene and lower pliocene deposits placed in calcareous nannofossil zones nn9 15 and in planktic foraminifer zones n16 19 contain species rich benthic microfaunas which indicate alternating reefal and brackish water mangrove environments the upper pliocene contains at least two major depositional hiatuses that coincide with a major faunal turnover in benthic foraminiferal and ostracode assemblages the quaternary is characterized by benthic microfaunas similar to those of modern atoll lagoons and is punctuated by at least 11 disconformities which signify periods of low sea level atoll subsidence rates during the last 10 ma averaged 30 to 40 m m y

influence of rock fragments on the water retention and water percolation in a calcareous soil abstract the water retention properties of a calcareous soil containing rock fragments have been determined in the laboratory thanks to pressure plate measurements done on both the fine earth and the rock fragments from the soil the available water content awc has been calculated from these data we have shown that when the rock fragments are neglected the awc can be overestimated by 39 when we do not neglect their volume but when their hydraulic properties are not considered the awc can be underestimated by 34 by using a reservoir model we have also calculated the effect of rock fragments on water percolation to groundwater depending of the climatic characteristics of the year the underestimation of percolation when we neglect the rock fragments can reach up to 14 9 and the overestimation when we neglect their hydraulic properties can be equal to 15 8 these findings emphasise the role of the rock fragments on the water supply in stony soils