Absence Of Minerals Research Articles

Microbially Induced Flotation of Galena and Quartz from Pyrite

Selective separation of pyrite from galena and quartz was achieved through microbiologically induced flotation in presence of Bacillus subtilis. B. subtilis functions as a depressant for pyrite while it promotes the flotation of galena and quartz. Bacterial extracellular protein (EP) was isolated and the protein profile of bacterial cells grown in presence and absence of minerals established.

QUALITATIVE ASSESSMENT OF TENSILE STRENGTH COMPONENTS OF HUMAN FEMUR TRABECULAR BONE USING RADIOGRAPHIC IMAGING AND SPECTRAL ANALYSIS

In this work, the primary and secondary tensile strength components of human femur trabecular bone are qualitatively assessed using planar radiographic images and spectral analysis. Normal and abnormal femur trabecular images (N = 40) were recorded using planar radiography following standard image acquisition protocol. From the images, the tensile strength components of the trabeculae are delineated using image processing procedures and are then subjected to Fourier transform. The zero (DC), First (FMOI), and Second Moments of Inertia (SMOI) are the parameters considered and are correlated with presence and absence of mineralization in the image. Results show that the values of moments correlate well with percentage mineralization in normal images when compared to abnormal images for both primary and secondary tensile strength components. Further, no or poor correlations were found for abnormals in all cases. Among all, the values of second moment showed highest correlation in the secondary tensile region. In this paper the objectives, methodology, significance results and the conclusions are presented.

Kerogen pyrolysis in the presence and absence of water and minerals: Amounts and compositions of bitumen and liquid hydrocarbons

The confined pyrolysis experiments of Kukersite kerogen in the presence and absence of minerals and water revealed the effects of mineral acidity and water/OC ratio on the conversion of kerogen into petroleum. The amount of bitumen and liquid hydrocarbons demonstrate that organic maturation rate increase with mineral acidity even in the presence of a large amount of water (water/OC 7–10). Organic maturation rate appeared unaffected with the addition of a small amount of water (water/OC 1.5), but it can be retarded with the addition of a large amount of water (water/OC 7–10) in confined pyrolysis experiments. The relative abundances of n-alkanes decrease whereas those of isoalkanes, cycloalkanes and light alkylbenzenes increase with both the mineral acidity and water/OC ratio. The relative abundances of naphalene, methylnaphalenes, phenanthrene and methylphenanthrenes also increase with mineral acidity but exhibit no clear variation trend with water/OC ratio.

Influence of Mineral on the Load Deformation Behavior of Polymer in Hydroxyapatite-Polyacrylic Acid Nanocomposite Biomaterials: A Steered Molecular Dynamics Study

Composites of hydroxyapatite and polymers are widely studied for bone replacement. To perform satisfactorily in the human body, these composites need to be biocompatible and exhibit optimum mechanical properties. The load-deformation behavior of composites is often investigated using experimental techniques. However, the molecular mechanisms of load deformation behavior are not clearly understood. We have used Steered Molecular Dynamics to evaluate the load-deformation behavior at interfaces in polyacrylic acid-hydroxyapatite (HAP) composite models. The polymer is pulled at constant velocity in close proximity of HAP. On comparing the results obtained for deformation behavior of polymer in vicinity of mineral and in the absence of mineral, it was found that energy required to pull the polymer in close proximity of HAP is significantly higher. Also, structural details of the load transfer mechanisms in composite were investigated under both conditions. Our simulations indicate that there is a significant role of mineral-polymer interactions on the mechanical response of polymer.

Characterization of Highly Luminescent LaPO4:Eu3+/LaPO4 One-Dimensional Core/Shell Heterostructures

Composites of hydroxyapatite and polymers are widely studied for bone replacement. To perform satisfactorily in the human body, these composites need to be biocompatible and exhibit optimum mechanical properties. The load-deformation behavior of composites is often investigated using experimental techniques. However, the molecular mechanisms of load deformation behavior are not clearly understood. We have used Steered Molecular Dynamics to evaluate the load-deformation behavior at interfaces in polyacrylic acid-hydroxyapatite (HAP) composite models. The polymer is pulled at constant velocity in close proximity of HAP. On comparing the results obtained for deformation behavior of polymer in vicinity of mineral and in the absence of mineral, it was found that energy required to pull the polymer in close proximity of HAP is significantly higher. Also, structural details of the load transfer mechanisms in composite were investigated under both conditions. Our simulations indicate that there is a significant role of mineral-polymer interactions on the mechanical response of polymer.

Basalt weathering rates on Earth and the duration of liquid water on the plains of Gusev Crater, Mars

Where Martian rocks have been exposed to liquid water, chemistry versus depth profi les could elucidate both Martian climate history and potential for life. The persistence of primary minerals in weathered profi les constrains the exposure time to liquid water: on Earth, mineral persistence times range from ~10 k.y. (olivine) to ~250 k.y. (glass) to ~1 m.y. ( pyroxene) to ~5 m.y. (plagioclase). Such persistence times suggest mineral persistence minima on Mars. However, Martian solutions may have been more acidic than on Earth. Relative mineral weathering rates observed for basalt in Svalbard (Norway) and Costa Rica demonstrate that laboratory pH trends can be used to estimate exposure to liquid water both qualitatively (mineral absence or presence) and quantitatively (using reactive transport models). Qualitatively, if the Martian solution pH >~2, glass should persist longer than olivine; therefore, persistence of glass may be a pH indicator. With evidence for the pH of weathering, the reactive transport code CrunchFlow can quantitatively calculate the minimum duration of exposure to liquid water consistent with a chemical profi le. For the profi le measured on the surface of the exposed Martian rock known as Humphrey in Gusev Crater, the calculated exposure time is 22 k.y., which is a minimum due to physical erosion. If correct, this estimate is consistent with short-term, episodic alteration accompanied by ongoing surface erosion. More of these depth profi les should be measured to illuminate the weathering history of Mars.

Generation of hydrocarbon gases and CO 2 from a humic coal: Experimental study on the effect of water, minerals and transition metals

The yields and composition of hydrocarbon gases and CO 2 generated from a humic coal were experimentally determined using the confined pyrolysis technique with different lithological conditions simulated by adding a variety of minerals (haematite, siderite, pyrrhotite, gypsum, KCl salt) and transition metals (including iron, nickel and vanadium). The experiments were conducted at 340 and 360 °C for time durations ranging from 24 to 240 h. The amount of water in the absence of minerals has negligible effect on the hydrocarbon gas yields; whereas some mineral–water environments impose a small, but measurable influence on both the yields and composition of the generated gases. The experiments with vanadium generated the highest hydrocarbon gas yield, while those with siderite yielded the least; with the difference as high as 15 mol%. The hydrocarbon gas yields increase slightly in the order from runs with Fe 2O 3, Ni, Fe, and V, and this trend becomes more pronounced at higher maturity. The dryness of HC gas decreases and then increases with increasing maturity, whereas the i-C 4/ n-C 4 isomer ratios progressively decrease with increasing maturity. The effects of most studied mineral matrices on these two ratios are insignificant, except the effect of Fe and haematite on the butane isomers. The effects of mineral environments with siderite, Fe, Ni and KCl on the variations of CO 2 yields are significant: CO 2 yield is highest in siderite and lowest in metallic iron or nickel environments. The effect of mineral environments on the variations of CO 2 yields is more pronounced than that of hydrocarbon gases.

Repair of porcine articular cartilage defect with autologous chondrocyte transplantation

Articular cartilage is known to have poor healing capacity after injury. Autologous chondral grafting remains the mainstay to treat well-defined, full-thickness, symptomatic cartilage defects. We demonstrated the utilization of gelatin microbeads to deliver autologous chondrocytes for in vivo cartilage generation. Chondrocytes were harvested from the left forelimbs of 12 Lee-Sung pigs. The cells were expanded in monolayer culture and then seeded onto gelatin microbeads or left in monolayer. Shortly before implantation, the cell-laden beads were mixed with collagen type I gel, while the cells in monolayer culture were collected and re-suspended in culture medium. Full-thickness cartilage defects were surgically created in the weight-bearing surface of the femoral condyles of both knees, covered by periosteal patches taken from proximal tibia, and sealed with a porcine fibrin glue. In total, 48 condyles were equally allotted to experimental, control, and null groups that were filled beneath the patch with chondrocyte-laden beads in gel, chondrocytes in plain medium solution, or nothing, respectively. The repair was examined 6 months post-surgery on the basis of macroscopic appearance, histological scores based on the International Cartilage Repair Society Scale, and the proportion of characteristic chondrocytes. Tensile stress-relaxation behavior was determined from uniaxial indentation tests. The experimental group scored higher than the control group in the categories of matrix nature, cell distribution pattern, and absence of mineralization, with similar surface smoothness. Both the experimental and control groups were superior to the null group in the above-mentioned categories. Viable cell populations were equal in all groups, but the proportion of characteristic chondrocytes was highest in the experimental group. Matrix stiffness was ranked as null > native cartilage > control > experimental group. Transplanted autologous chondrocytes survive and could yield hyaline-like cartilage. The application of beads and gel for transplantation helped to retain the transferred cells in situ and maintain a better chondrocyte phenotype.

Cultivation and Soil Organic Matter Management in Low Input Cereal Production following the Ploughing out of Grass Leys

Nitrogen fertility of low input cereal systems following ploughing out of grass leys is investigated using the soil nitrogen dynamics model SOILN with its linked cereal growth model, supported by a set of experimental data for spring and winter barley cropping. Soil organic matter (OM) plays an important part in transfer of fertility from the fertility-building ley phase to the fertility exploitation arable phase of ley-arable rotations. One aspect investigated is a possible role of ‘protected organic matter’, a component of soil OM which generally mineralises at a slow rate, but which becomes ‘unprotected’ so it mineralises at a somewhat faster rate for a limited period following disturbance of the soil by ploughing. Measurements of CO2 emissions in the laboratory and field support the concept of protected OM. In simulations with the SOILN model, this is represented by a temporary increase in the value of the humus decomposition rate constant for a few weeks following ploughing. The assumption of raised humus decomposition rates after ploughing makes some improvements to fits of simulations with the linked models to measured grain and straw yields and N offtakes, as well as giving a more realistic decline in soil OM over successive years of cereal cropping. Predictive simulations demonstrate how, in the absence of mineral N fertiliser, cereal crop yields decline over the years following ploughing out of leys, but yields can be maintained by making applications of organic manure or slurry.

Nitrogen-fixing and vesicular–arbuscular mycorrhizal symbioses in some tropical legume trees of tribe Mimoseae

Response to mineral fertilization and inoculation with rhizobia and/or arbuscular mycorrhiza fungi (AMF) of the Anadenanthera colubrina, Mimosa bimucronata and Parapiptadenia rigida (Leguminosae–Mimosoideae) native trees from Brazilian riparian forests, were studied in nursery conditions. Each species was submitted to seven treatments, varying nitrogen and phosphorous fertilization and inoculation with rhizobia (r), mycorrhiza (m) or both (rm): NP, P, P+r,P+rm, N, N+m and N+rm. Results showed that AMF inoculations did not enhance the mycorrhizal colonization, and P uptake was not sufficient to sustain good growth of plants. The level of P mineral added affected negatively the AMF colonization in A. colubrina and M. bimucronata, but not in P. rigida. Native fungi infected the three legume hosts. The absence of mineral N limited growth of A. colubrina and P. rigida, but in M. bimucronata the lack of N was corrected by biological nitrogen fixation. N mineral added inhibited the nodulation, although spontaneous nodulation had occurred in A. colubrina and M. bimucronata. Rhizobia inoculation enhanced the number of nodules, nitrogenase activity and leghemoglobin content of these two species. Thus, the extent of rhizobial and mycorrhizal symbiosis in these species under nursery conditions can affect growth and consequently the post-planting success.

Dispersion of gold in Slesse Creek, British Columbia

Because of the high costs and difficult logistics of geochemical surveys in remote regions, sediments collected from large streams must often suffice to determine the presence or absence of mineralization. Here we study this problem in Slesse Creek, a gold-rich river that drains north from the Mt. Baker District, Washington, USA, to enter the Chilliwack River, British Columbia, c . 90 km east of Vancouver. Anomalous Au values are derived from the abandoned Red Mountain Mine just south of the USA–Canada border. Sediments were collected from Slesse Creek and its tributaries, and from other large streams in the Chilliwack River basin. Concentrations of Au in tributaries from the Red Mountain Mine range from 250 to 2330 ppb and are much greater than in other tributaries. Sediments from Slesse Creek also have anomalous, but extremely erratic, Au values. This erratic distribution of Au is generally similar to that of magnetic grains and associated elements (e.g. V) but is negatively correlated with elements, such as Na, associated with light minerals. Results are interpreted as an evolution in sediment geochemistry from the tributaries to Slesse Creek: composition of the former appears to be controlled by source (i.e. geology) whereas geochemistry of sediments in Slesse Creek has been strongly modified by fluvial processes that concentrate Au and other heavy minerals. This shift from source- to process-related geochemistry invalidates the traditional geochemical dilution model and gives long anomalous dispersion trains for Au. These provide suitable targets for low-density regional surveys, but are difficult to interpret because of their erratic character. The contribution of fluvial processes to the concentration of Au can, however, be evaluated by comparison with elements such as V, that are associated with ubiquitous heavy minerals, or by plotting data on x – y – z source–process plots.

The magmatic-hydrothermal evolution of two barren granites: a melt and fluid inclusion study of the Rito del Medio and Cañada Pinabete plutons in northern New Mexico (USA)

The magmatic-hydrothermal evolution of two barren granites associated with the Tertiary Questa Caldera in northern New Mexico was reconstructed on the basis of microthermometric and laser-ablation inductively coupled plasma mass spectrometry analysis of fluid and melt inclusions in quartz of magmatic and hydrothermal origin. During progressive crystallization and fluid exsolution, the Cs content of the residual melt increased from 1 ppm to values as high as 5500 ppm, which requires an increase in crystallinity by at least 99.98%. In conjunction with a Rayleigh fractionation model simulating the melt evolution at fluid-saturated vs. fluid-undersaturated conditions, the melt inclusion data can be used to determine the crystallinity at which fluid saturation was reached. Our results suggest that both plutons attained fluid saturation before 30% crystallization and that evolved residual melts accumulated in their roof zones. At ∼90% crystallization, the exsolving fluids were of low salinity (∼5 wt.% NaCl equiv) and in the one-phase field, in accordance with phase relations at the reconstructed P and T conditions (∼1.1 to 1.3 kbar, 700 to 720°C). Fluid-melt partition coefficients for a range of metals determined on assemblages of coeval melt and fluid inclusions were generally too low to allow efficient metal extraction from the melt ( D X, fluid-melt < 22). As a result, the metal concentrations in both the residual melt and the coexisting fluid increased with progressive crystallization. Absolute metal contents in the fluids exsolving from barren systems appear low, however, when compared with mineralized systems. It is concluded that the absence of mineralization in the Rito del Medio and Cañada Pinabete plutons primarily stems from a low salinity of the exsolving fluids, resulting in a less efficient metal extraction from the melt.

The Placenta in Pseudoxanthoma Elasticum: Clinical, Structural and Immunochemical Study

Pseudoxanthoma elasticum (PXE) is a rare genetic disorder clinically characterized by skin, cardiovascular and eye manifestations, mainly due to calcification and fragmentation of elastic fibres. Although infrequent, complications during pregnancy in women affected by PXE have been reported.The aim of the present study was to compare structural features of placentae at term from 14 control and 15 PXE-affected women, in order to better understand if and how abnormal mineral and/or matrix accumulation might affect placental function in PXE. In all cases, pregnancy, fetus growth and delivery were normal. Both gross and light microscopy examination did not reveal dramatic differences between placentae of PXE patients and controls, with regard to weight, dimensions, infarcts, thrombi, inflammatory lesions or vessels. However, necrotic changes and mineralization appeared statistically more pronounced in PXE. By electron microscopy the most remarkable differences between PXE and control placentae were observed in the localization and morphology of mineral precipitates; a significant higher deposition of mineral precipitates was observed associated with the ‘matrix’-type fibrinoid and among collagen fibrils, especially on the maternal side. Immunocytochemistry revealed the presence of vitronectin and fibronectin associated with the PXE-specific mineralizations and the absence of mineralization on the small and scarce elastic fibres in either controls or in PXE.

Surface chemical characterisation of Paenibacillus polymyxa before and after adaptation to sulfide minerals

A heterotroph Paenibacillus polymyxa bacteria is adapted to pyrite, chalcopyrite, galena and sphalerite minerals by repeated subculturing the bacteria in the presence of the mineral until their growth characteristics became similar to the growth in the absence of mineral. The unadapted and adapted bacterial surface have been chemically characterised by zeta-potential, contact angle, adherence to hydrocarbons and FT-IR spectroscopic studies. The surface free energies of bacteria have been calculated by following the equation of state and surface tension component approaches. The aim of the present paper is to understand the changes in surface chemical properties of bacteria during adaptation to sulfide minerals and the projected consequences in bioflotation and bioflocculation processes. The mineral-adapted cells became more hydrophilic as compared to unadapted cells. There are no significant changes in the surface charge of bacteria before and after adaptation, and all the bacteria exhibit an iso-electric point below pH 2.5. The contact angles are observed to be more reliable for hydrophobicity assessment than the adherence to hydrocarbons. The Lifschitz–van der Waals/acid–base approach to calculate surface free energy is found to be relevant for mineral–bacteria interactions. The diffuse reflectance FT-IR absorbance bands for all the bacteria are the same illustrating similar surface chemical composition. However, the intensity of the bands for unadapted and adapted cells is significantly varied and this is due to different amounts of bacterial secretions underlying different growth conditions.

The use of nitrogen-15 natural abundance in white clover ( Trifolium repens L.) to determine nitrogen fixation under different management practices

The 15N natural abundance (δ15N) of white clover (Trifolium repens L.) grown in pasture under different management practices was determined. Plants were split into leaflets, petioles and stolons and the 15N signature of each tissue was measured. The δ15N of leaflet tissue from plants of two non-N2-fixing species (Lolium perenne L. and Ranunculus repens L.), growing in close proximity to the sampled T. repens, was also measured. By using T. repens plants grown in the absence of mineral N to provide reference material, the proportion of N derived from N2 fixation (%Ndfa) in pasture plants was calculated. Within a plot, variation was present in the δ15N between the tissues of T. repens. Variation was also present between the same tissues under different management practices. The %Ndfa in the leaf material of T. repens varied from 34% to 100% between the plots. The use of different reference species did not affect the estimate of %Ndfa.

Mineral Favorability Mapping: A Comparison of Artificial Neural Networks, Logistic Regression, and Discriminant Analysis

A Probabilistic Neural Network (PNN) was trained to classify mineralized and nonmineralized cells using eight geological, geochemical, and geophysical variables. When applied to a second (validation) set of well-explored cells that had been excluded from the training set, the trained PNN generalized well, giving true positive percentages of 86.7 and 93.8 for the mineralized and nonmineralized cells, respectively. All artifical neural networks and statistical models were analyzed and compared by the percentages of mineralized cells and barren cells that would be retained and rejected correctly respectively, for specified cutoff probabilities for mineralization. For example, a cutoff probability for mineralization of 0.5 applied to the PNN probabilities would have retained correctly 87.66% of the mineralized cells and correctly rejected 93.25% of the barren cells of the validation set. Nonparametric discriminant analysis, based upon the Epanechnikov Kernel performed better than logistic regression or parametric discriminant analysis. Moreover, it generalized well to the validation set of well-explored cells, particularly to those cells that were mineralized. However, PNN performed better overall than nonparametric discriminant analysis in that it achieved higher percentages of correct retention and correct rejection of mineralized and barren cells, respectively. Although the generalized regression neural network (GRNN) is not designed for a binary—presence or absence of mineralization— dependent variable, it also performed well in mapping favorability by an index valued on the interval [0, 1]. However, PNN outperformed GRNN in correctly retaining mineralized cells and rejecting barren cells of the validation set.

Formation of saline brines and salt in the lower crust by hydration reactions in partially retrogressed granulites from the Lofoten Islands, Norway

Anorthosites, gneisses and mangeritic rocks from the Lofoten Islands in northern Norway contain Cl-rich amphibole (up to 3.5 wt percent Cl) and biotite (up to 1.5 wt percent Cl) that developed mostly during regional metamorphism at ~600°C and ~9 kb by replacement of older anhydrous granulite facies mineral assemblages. (Na,K)Cl halide solid solutions are closely associated spatially with amphiboles that have the highest measured Cl-contents. Rocks with Cl-rich amphiboles and biotites always have minerals that exhibit a wide range in OH/Cl; one sample from a shear zone contains virtually Cl-free amphibole within a few millimeters of Cl-rich amphibole coexisting with halide crystals. Textural evidence indicates that amphibole and biotite evolved from Cl-poor to Cl-rich compositions within individual samples; OH-rich, Cl-poor compositions are always much more abundant than Cl-rich ones. Cl-rich amphiboles and biotites exclusively occur in rocks that contain relict granulite facies minerals (pyroxene and/or olivine); samples in which no granulite facies minerals remain contain amphiboles and biotites without elevated Cl-contents. In one particular case, the restricted development of Clrich amphiboles and biotites within a shear zone and the absence of these minerals from undeformed lithologic equivalents outside the shear zone demomstrate that the amphibole and biotite developed by reaction between a preexisting granulite facies mineral assemblage and an aqueous fluid rather than by fluid-ansent metamorphism or by magmatic processes. We infer from this example that Cl-rich amphibole nad biotite with the same grani size and texture as in the shear zone developed throughout the Lofoten Islands by fluid-rock reaction. Mineralfluid equilibria indicate that the aqueous fluid was variable in composition ranging from XH2O (=[H2O/(H2O+Cl)] of 0.99 for equilibrium with the most Cl-poor amphiboles and biotites to 0.4-0.6 for equilibrium with the most Cl-rich minerals that coexist with salt. The most saline fluids correspond to NaCl equivalent concentrations of over 25 mol/l. The range in OH/Cl of amphiboles and biotite in individual samples and the restricted occurrence of Cl-rich minerals in rocks with relict pyroxene and/or olivine can be explained by a desiccation model in which small amounts of normal low-Cl crustal fluid infiltrates rocks with granulite facies minerals and is subsequently enriched in Cl by preferential consumption of H2O during the resulting hydration reaction. Saline fluids developed at the extremes of reaction progress and then produced the Cl-rich amphibole and biotite compositions coexisting with halide crystals. The desiccation model further explains variations in the whole-rock concentration of Cl in rocks from the Lofoten Islands, the absence of Cl-rich minerals from completely retrogressed granulites that lack olivine or pyroxene, the measured frequency distribution of amphibole and biotite compositions in individual samples, and the calculated evolution of fluid composition with reaction progress. Our results have implications for interpreting measurements of elevated electrical conductivity in the lower crust and for models of granulite genesis that appeal to fluids with low H2O activity. Amer. J. Science (1998), 298, 705-757

Photoassimilate partitioning in nodulated soybean I. 11C methodology

An established method using 11C for the in vivo measurement of photoassimilate partitioning within intact plants was applied to the characterization of Introduction partitioning of photoassimilate to soybean nodules. In the absence of mineral N, all primary N assimilation The method describes partitioning in terms of the in a nodulated legume occurs via an energetically expensmagnitude and stability of partitioning flows, i.e. sink

Sistemas de manejo do solo e seus efeitos sobre o rendimento do milho

Uma das metas da pesquisa em manejo de solos deve ser a definição de sistemas de produção adequados à produtividade das culturas, conservação e recuperação do solo. Nesse sentido, realizou-se este estudo que teve por objetivo avaliar o efeito da inclusão de leguminosas como culturas de cobertura, e da incorporação ou não de seus resíduos ao solo, sobre o rendimento do milho. Utilizou-se dois experimentos instalados na Estação Experimental Agronômica da UFRGS, Eldorado do Sul, RS. Esses experimentos, instalados há sete e nove anos, são constituídos de métodos de preparo (convencional, reduzido e plantio direto), sistemas de cultura (pousio/milho, aveia/milho, aveia+vica/milho, aveia+-v'iça/milho+caupi, vica+gorga/milho e lablabe+milho) e doses de N (0 e 120kg/ha). Os métodos de preparo, realizados na implantação da cultura do milho, não afetaram o seu rendimento. Os sistemas de cultura somente afetaram o rendimento do milho quando não foi aplicado N mineral. Nos diferentes sistemas de cultura, sem aplicação de N, o rendimento do milho variou entre l,46t/ha e 5,02 t/ha. As culturas de cobertura do solo apresentaram um efeito no rendimento do milho equivalente a aplicação de 4 a 90kg/ha de N. A associação de culturas de cobertura leguminosas ao sistema de plantio direto resultou em maiores rendimentos de milho e maior produção de resíduos vegetais, permitindo a economia em N mineral e podendo acelerar o processo de recuperação de solos degradados.

Calcic Paleosols: Their Use in Subsurface Stratigraphy

Analysis of well log data from Cenozoic basin fill of the Deer Lodge Valley, southwestern Montana, provides evidence for identifying paleosols and paleosol stacks in the subsurface. The paleosol stacks are continental sequence boundary markers and appear as several relatively thin, high-velocity/high-density zones within basin fill. Zone thickness ranges from 1 to 1.5 m; zones are stacked to thicknesses of up to 15 m. Density varies within the zones by as much as 0.6 g/cm3, and differs by as much as 0.9 g/cm3 from material immediately above these zones. Velocity differs by as much as 10 ft/ms from the overlying material and causes bright reflections on seismic sections. Synthetic seismograms are used to tie well log and seismic data. Basing our interpretation upon well log data and well cuttings analyses, we determined the high-velocity/high-density zones to be limestone. The pedogenic origin of the limestone is shown by (1) well cutting chips from the high-velocity/high-density zones that exhibit pedogenic features associated with calcic paleosols, (2) paleosol horizonation interpreted from well log analysis, (3) the absence of minerals normally associated with lacustrine deposits, and (4) comparison with surface paleosol exposures.