12033943 Perttu, Nils (Lulea University of Technology, Division Ore Geology and Applied Geophysics, Lulea, Sweden); Persson, Lena; Erlstrom, Mikael and Elming, Sten-Ake. Magnetic resonance sounding and radiomagnetotelluric measurements used to characterize a limestone aquifer in Gotland, Sweden: Journal of Hydrology, 424-425, p. 184-195, illus. incl. 1 table, geol. sketch map, 31 ref., March 6, 2012.
Almost all drinking water in Gotland is groundwater and is mainly found in karst limestone. However, the unpredictable location and geometry of the karst cracks and caverns makes it very difficult to estimate groundwater storage and movement, as well as contaminant transport. The aim of this study was to test the performance of different geophysical techniques like Magnetic Resonance Sounding (MRS), Radiomagnetotelluric (RMT), Vertical Electrical Sounding (VES) and Ground Penetrating Radar (GPR) to characterize aquifers in Gotland, in respect to geometry and storage as well as connectivity over a wider area. The investigated area is located on the south-eastern part of Gotland. The geology here is dominated by 50-60 m thick successions of limestone that gradually turn into marlstone. The use of multiple techniques has shown to give a more coherent interpretation. However, the shallow penetration depth of GPR and the lack of soil cover in some places of the investigated area limit the use of geoelectrical methods and GPR. With MRS, water are found down to 60 m in depth, with a maximum water content at depths of 20-30 m. This coincides with the most resistive sections of the limestone. The water content varies between 0% and 3%, with a relaxation time (T1MRS) less than 400 ms suggesting that the aquifer is hosted in small fractures, molds and vugs rather than larger karst fractures and caverns. Two potential aquifers were identified with MRS, possibly separated by marlstone. From modeling it can be seen that such boundary separating two aquifer apart can be more easily discriminated in the N/S-, than in the E/W direction. In summary, MRS is therefore the only method in this survey that can detect and determine the vertical and lateral distribution of water within the aquifer together with the total volume of free water. The RMT method has shown to be effective in characterizing the limestone/marl interface, but also to locate anomalous low resistive zones, possibly associated with salt water. RMT also helps to constrain the final MRS model by choosing a suitable regularization for the MRS 3D inversion. All together, the combination of MRS and RMT seems most efficient of the tested methods and therefore most promising for future groundwater explorations in geological environments like in eastern Gotland.
12035855 Andermann, Christoff (Université de Rennes, Géosciences Rennes, Rennes, France); Longuevergne, Laurent; Bonnet, Stéphane; Crave, Alain; Davy, Philippe and Gloaguen, Richard. Impact of transient groundwater storage on the discharge of Himalayan rivers: Nature Geoscience, 5(2), p. 127-132, illus. incl. 1 table, sketch map, 30 ref., February 2012. Supplemental information/data is available in the online version of this article; related article by Bookhagen, B., on p. 97-98.
12030359 Arthur, Emmanuel (Aarhus University, Department of Agroecology, Tjele, Denmark); Moldrup, Per; Schjonning, Per and de Jonge, Lis W. Linking particle and pore size distribution parameters to soil gas transport properties: Soil Science Society of America Journal, 76(1), p. 18-27, illus. incl. 2 tables, 44 ref., February 2012.
Accurate estimation of soil gas diffusivity (Dp/Do, the ratio of gas diffusion coefficients in soil and free air) and air permeability (ka) from basic texture and pore characteristics will be highly valuable for modeling soil gas transport and emission and their field-scale variations. From the topsoil of two Danish arable fields representing two natural clay gradients, Dp/Do and ka were measured at soil water matric potentials between -1 and -100 kPa on undisturbed soil cores. The Rosin-Rammler particle size distribution parameters a and b (characteristic particle size and degree of sorting, respectively) and the Campbell water retention parameter b were used to characterize particle and pore size distributions, respectively. Campbell b yielded a wide interval (4.6-26.2) and was highly correlated with a, b, and volumetric clay content. Both Dp/Do and ka followed simple power-law functions (PLFs) of air-filled porosity (a). The PLF tortuosity-connectivity factors (c) for Dp/Do and ka were both highly correlated with all basic soil characteristics, in the order of volumetric clay content = Campbell b > gravimetric clay content > a > b. The PLF water blockage factors (H) for Dp/Do and ka were also well (but relatively more weakly) correlated with the basic soil characteristics, again with the best correlations to volumetric clay content and b. As a first attempt at developing a simple Dp/Do model useful at the field scale, we extended the classical Buckingham Dp/Do model (ea2) by a scaling factor based on volumetric clay content. The scaled Buckingham model provided accurate predictions of Dp(ea)/Do across both natural clay gradients.
12030339 Huang, Jun-Wei (Geological Survey of Canada, Ottawa, ON, Canada) and Bellefleur, Gilles. Joint transmission and reflection traveltime tomography using the fast sweeping method and the adjoint-state technique: Geophysical Journal International, 188(2), p. 570-582, illus. incl. geol. sketch maps, 47 ref., February 2012.
We present a joint transmission and reflection traveltime tomography algorithm based on the Fast Sweeping Method and the adjoint-state technique. In contrast to classical ray based tomography, this algorithm utilizes a grid-based Eikonal equation solver to circumvent the non-linearity of conventional ray shooting and bending approaches in complex media. The adjoint-state technique is used to obtain the gradient of the objective function without the explicit estimation of the Fréchet derivative matrix, which is usually computationally prohibitive for large-scale problems. When combined with Huygens' Principle, the tomographic inversion can simultaneously use direct and reflected arrivals to optimize a final velocity model, further mitigate the ambiguity of the inverse problem and reveal deeper structures not visible to transmission tomography alone. In this paper, we describe the theoretical basis of our algorithm, evaluate its performance on synthetic models, and then apply it to a 20 km long 2-D seismic survey acquired in the Mackenzie Delta, Northwest Territories of Canada. The subsurface at that location is characterized by a thick permafrost (600 m) comprising high- and low-velocity areas associated with thermokarst lakes. Our results show the potential of the joint tomography in characterizing multi-scale heterogeneous velocity structures within the permafrost. Abstract Copyright (2011), RAS.
12030361 Kelleners, T. J. (University of Wyoming, Department of Renewable Resources, Laramie, WY) and Norton, J. B. Determining water retention in seasonally frozen soils using Hydra impedance sensors: Soil Science Society of America Journal, 76(1), p. 36-50, illus. incl. 3 tables, 40 ref., February 2012.
The soil freezing characteristic, defined as the relationship between freezing soil temperature and unfrozen water content, can be used to determine the soil water retention curve in situ. The objective of this study was to investigate whether freezing characteristics measured with Hydra impedance sensors (Stevens Water Monitoring Systems, Portland, OR) result in accurate depthwise soil water retention curves. Hydra sensors measuring the complex permittivity and soil temperature were installed at five depths at five sites in southeastern Wyoming and monitored for approximately 2 yr. A dielectric mixing model was calibrated using unfrozen soil data to predict the liquid water content and ice content in frozen soils. The total water potential in the frozen soils was calculated from the Hydra sensor soil temperature measurements using the Clapeyron equation. Soil water pressure heads were calculated from the total soil water head by subtracting the osmotic head. Comparison of the resulting Hydra sensor water retention data with depthwise laboratory retention data using a dew point potentiometer and a pressure plate extractor showed mixed results (coefficient of determination 0 ≤&eq; R2 ≤&eq; 0.94). The best results were obtained for the shallowest sensors at the five sites (0.74 ≤&eq; R2 ≤&eq; 0.93) because of the more significant and more prolonged soil freezing at these depths, resulting in relatively wide ranges for the calculated soil water pressure heads. Fitted curves for the Hydra sensor water retention data yielded unreliable parameters because of insufficient information on the wet end of the water retention curves.
12030362 Laegdsmand, Mette (Aarhus University, Department of Agroecology and Enviroment, Tjele, Denmark); Moldrup, Per and Schjonning, Per. Solute diffusivity in undisturbed soil; effects of soil water content and matric potential: Soil Science Society of America Journal, 76(1), p. 51-60, illus. incl. 6 tables, 34 ref., February 2012.
Solute diffusivity in soil plays a major role in many important processes with relation to plant growth and environmental issues. Soil solute diffusivity is affected by the volumetric water content as well as the morphological characteristics of water-filled pores. The solute diffusivity in intact soil samples from two different tillage treatments (soil from below the depth of a harrow treatment and soil from within a moldboard plowed plow layer) was estimated based on concentration profiles using a newly developed method. The method makes use of multiple tracers (two sets of counterdiffusing tracers) for a better determination of the diffusivity. The diffusivity was higher in the below-till soil than the plowed soil at the same soil water matric potential due to higher water content but also due to higher continuity and lower tortuosity of the soil pores. We measured identical solute diffusivities independent of the tracer set used. We analyzed the whole data set using Archie's law and found a linear relation between Archie's exponent and the logarithm of the soil water matric suction in centimeters of water (pF). An analysis of seven data sets from the literature showed that this was a general trend for soils with moderate to low clay contents.
12030440 Sun Jimin (Chinese Academy of Sciences, Institute of Geology and Geophysics, Beijing, China); Lu Tongyan; Zhang Zhang; Wang Xu and Liu Weiguo. Stepwise expansions of C4 biomass and enhanced seasonal precipitation and regional aridity during the Quaternary on the southern Chinese Loess Plateau: Quaternary Science Reviews, 34, p. 57-65, illus. incl. sketch map, 61 ref., February 21, 2012.
The expansion of C4 plants is one of the most prominent vegetation changes in the global ecosystem during the Cenozoic Era. Although C4 plant expansions in the latest Miocene have been widely reported, factors driving the expansions are still in debate, and the details of vegetation changes during the Quaternary have not been well studied. Here we present high-resolution carbon isotope time series of both organic matter and bulk carbonates, covering the past 2.58 Ma, derived from the loess-soil successions on the southern Chinese Loess Plateau. The organic matter d13C values indicate stepwise C4 plant expansions initiated at ~1.6 and at ~0.43 Ma, respectively. We conclude that such tectonic time scale C4 plant expansions are controlled by enhanced seasonality of precipitation (relatively more precipitation in the warm growing season) as well as regional aridity, and this long-term fluctuation superimposes on the orbital scale variations of C4 plants, while the latter appears phase-locked with cyclical changes of summer monsoon circulations.
12030437 Vandenberghe, J. (Vrije University of Amsterdam, Section of Climate Change and Landscape Dynamics, Amsterdam, Netherlands); Renssen, H.; Roche, D. M.; Goosse, H.; Velichko, A. A.; Gorbunov, A. and Levavasseur, G. Eurasian permafrost instability constrained by reduced sea-ice cover: Quaternary Science Reviews, 34, p. 16-23, illus., 51 ref., February 21, 2012.
In order to specify potentially causal relationships between climate, permafrost extent and sea-ice cover we apply a twofold research strategy: (1) we cover a large range of climate conditions varying from full glacial to the relatively warm climate projected for the end of the 21st Century, (2) we combine new proxy-based reconstructions of Eurasian permafrost extent during the LGM and climate model simulations. We find that that there is a linear relationship between the winter sea-ice extent in the North Atlantic and Arctic Oceans and the latitude of the southernmost permafrost limit in Eurasia. During the LGM, extensive sea-ice cover caused a zonal permafrost distribution with the southern margin extending W-E and reaching 47°N, contrasting with the present-day NW-SE trending margin (66°-52°N). We infer that under global warming scenarios projected by climate models for the 21st Century the Arctic sea-ice cover decline will cause widespread instability of, mainly discontinuous, permafrost in Eurasian lowlands.
12035583 Rinke, A. (Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany); Matthes, H.; Christensen, J. H.; Kuhry, P.; Romanovsky, V. E. and Dethloff, K. Arctic RCM simulations of temperature and precipitation derived indices relevant to future frozen ground conditions: Global and Planetary Change, 80-81, p. 136-148, sketch maps, 40 ref., January 2012.
A regional climate model with high horizontal resolution (25 km) is used to downscale 20-year-long time slices of present-day (1980-1999) and future (2046-2065, 2080-2099) Arctic climate, as simulated by the ECHAM5/MPI-OM general circulation model under the A1B emission scenario. Changes in simulated air temperature and derived indices at the end of the century indicate that significant impacts on permafrost conditions should be expected. But the magnitude of the change is regionally conditioned beyond what is obvious: Warm permafrost in the sporadic to discontinuous zone is threatened and may degrade or even complete thaw before the end of the century. A decrease in freezing and increase in thawing degree-days is interpreted as potential decrease in seasonal freeze depth and increase in active layer thickness (ALT). We show that for some regions increasing maximum summer temperature is associated with an increase of interannual temperature variability in summer, while in other regions decreased maximum summer temperatures are related to decreased variability. The occurrence of warm/cold summers and spells changes significantly in the future time slices using the present-day criteria for classification. Taken together this implies a regionally varying exposure to significant change in permafrost conditions. In addition to these aspects of the general warming trend that would promote an increase in ALT and a northward shift of the southern permafrost boundary, an analysis of the occurrence of warm summers and spells highlight some particularly vulnerable regions for permafrost degradation (e.g. West Siberian Plain, Laptev Sea coast, Canadian Archipelago), but also some less vulnerable regions (e.g. Mackenzie Mountains).
12033861 Czajkowski, Michael (Open University, Milton Keynes, United Kingdom) and Okulitch, Andrew V. An unusual stone circle, Chilcotin Range, British Columbia, Canada: Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre, 48(12), p. 1523-1529, illus. incl. sketch map, 14 ref., December 2011.
A unique circular feature of uncertain origin lies above the tree line on the eastern flanks of the Coast Range of British Columbia, Canada. It is composed of white, fractured, angular cobbles to boulders predominantly under 1 m across, arrayed in a slightly flattened circle nearly 50 m in diameter with the ring mostly about 4 m in width. The felsic granitoid lithology of the circle is unlike any in the immediate region, and no clasts of this composition occur within the circle. The debris rests on soliflucted soil containing rounded pebbles to cobbles of granodiorite that forms the regional lithology. The age of the circle is deglacial with post-glacial modification. Given the absence of similar lithologic units in the region and no obvious symbolic purpose for such a feature, an anthropogenic origin for the circle is improbable. Mechanisms for transporting the foreign rock unit to its final location, distributing fragments into a circle, and preserving it include flow of alpine and fringing continental ice masses, deglaciation, freeze-thaw cycles, and post-glacial solifluction and erosion. One large slab was either entrained within or fell onto a flowing glacier from some unknown outcrop at least 2 km from the site of the circle. During deglaciation, the insulating cap preserved the ice beneath it forming an isolated stagnant mass of ice. Freeze-thaw cycles likely affected the slab when it was on the surface of the ice, but it remained coherent, otherwise glacial flow or meltwater streams might have scattered loose clasts. Once the ice became stagnant, continued freeze-thaw cycles eventually created a rubble pile, which slid off the presumably symmetrical mass of ice to become arranged in a roughly circular ring. Having lost its protective cover, the ice melted and subsequent solifluction slightly modified the ring.
12035706 Farbrot, Herman (University of Oslo, Department of Geosciences, Oslo, Norway); Hipp, Tobias Florian; Etzelmuller, Bernd; Isaksen, Ketil; Odegard, Rune Strand; Schuler, Thomas Vikhamar and Humlum, Ole. Air and ground temperature variations observed along elevation and continentality gradients in Southern Norway: in In honour of Professor Charles Harris (Murton, J., editor), Permafrost and Periglacial Processes, 22(4), p. 343-360, illus. incl. 5 tables, geol. sketch maps, December 2011.
12035708 Hasler, Andreas (University of Zurich, Department of Geography, Zurich, Switzerland); Gruber, Stephan; Font, Marianne and Dubois, Anthony. Advective heat transport in frozen rock clefts; conceptual model, laboratory experiments and numerical simulation: in In honour of Professor Charles Harris (Murton, J., editor), Permafrost and Periglacial Processes, 22(4), p. 378-389, illus., 30 ref., December 2011.
12035704 Hilbich, Christin (University of Jena, Geographical Institute, Jena, Germany); Fuss, C. and Hauck, Christian. Automated time-lapse ERT for improved process analysis and monitoring of frozen ground: in In honour of Professor Charles Harris (Murton, J., editor), Permafrost and Periglacial Processes, 22(4), p. 306-319, illus. incl. 1 table, 30 ref., December 2011.
12035707 Isaksen, Ketil (Norwegian Meteorological Institute, Oslo, Norway); Odegard, Rune Strand; Etzelmuller, Bernd; Hilbich, Christin; Hauck, Christian; Farbrot, Herman; Eiken, Trond; Hygen, Hans Olav and Hipp, Tobias Florian. Degrading mountain permafrost in Southern Norway; spatial and temporal variability of mean ground temperatures, 1999-2009: in In honour of Professor Charles Harris (Murton, J., editor), Permafrost and Periglacial Processes, 22(4), p. 361-377, illus. incl. 1 table, 48 ref., December 2011.
12035765 Kuenene, B. T. (University of the Free State, Department of Soil, Crop and Climate Sciences, Bloemfontein, South Africa); Van Huyssteen, C. W.; Le Roux, P. A. L.; Hensley, M. and Everson, C. S. Facilitating interpretation of the Cathedral Peak VI catchment hydrograph using soil drainage curves: South African Journal of Geology, 114(3-4), p. 525-534, illus., 24 ref., December 2011.
It was hypothesized that, with regard to subsurface flow from the cathedral Peak VI catchment: (a) a defined change in the slope of the hydrograph during a prolonged almost rain free period reflects the onset of outflow from a particular water storage zone of the catchment; (b) reliable soil (upper vadose zone) drainage curve data can help to interpret outflow from that particular water storage zone. To test the hypothesis, measured hydrograph and soil water data from previous studies in the Cathedral Peak VI catchment were used. Drainage curves were derived for the main soils during the rain free autumn periods of four years 1991 to 1994 and the relevant hydrograph were subdivided into appropriate logical regions. The contribution of the soils (upper vadose zone) to streamflow was estimated using the soil drainage curves from selected sites together with the areas of the catchment that they represented. The estimations were compared to estimations done using data from measured streamflow values for the equivalent periods of the hydrographs. The results obtained by the two estimates were as follows, with measurement year, then hydrograph and soil drainage curve estimates (m3), respectively: 1991, 24841, 20061; 1992, 39048, 16528; 1993, 29967, 28448; 1994, 15703, 20809. Apart from the results for 1992, for which a logical explanation is provided, it is concluded that the hypothesis is valid.
12035709 Lantuit, Hugues (International Permafrost Association, International) and May, Inga. Report from the International Permafrost Association: in In honour of Professor Charles Harris (Murton, J., editor), Permafrost and Periglacial Processes, 22(4), p. 390-391, December 2011.
12035705 Lewkowicz, Antoni G. (University of Ottawa, Department of Geography, Ottawa, ON, Canada); Etzelmuller, Bernd and Smith, Sharon L. Characteristics of discontinuous permafrost based on ground temperature measurements and electrical resistivity tomography, southern Yukon, Canada: in In honour of Professor Charles Harris (Murton, J., editor), Permafrost and Periglacial Processes, 22(4), p. 320-342, illus. incl. 4 tables, geol. sketch map, December 2011.
Warm permafrost conditions (mean temperatures of -3°C to -0.1°C) were investigated in detail at 13 valley and mountain sites in the sporadic (10-50%) and extensive (50-90%) discontinuous permafrost zones in the southern half of the Yukon (60°N to 64°N), using a combination of ground temperature monitoring, electrical resistivity tomography (ERT), frost table probing and coring. Sites were selected to cover a wide range of substrates, vegetation types and ground ice contents. ERT profiling in the spring imaged both deep seasonal frost and perennially frozen ground. Deep active layers measured by probing at the end of summer were also detectable by ERT. Where ground temperatures indicated that the base of permafrost was at a depth of less than 25 m, vertical transitions in apparent resistivity were more sharply defined in coarse materials than in fine-grained deposits, probably because of differences in unfrozen moisture contents at temperatures just below 0°C. Apparent resistivity values related to excess ice fraction and ground temperatures were similar to those previously obtained in Mongolia and Iceland, but generally lower than in ice-rich rock glaciers in European studies. The observations revealed the complexity of site conditions where permafrost is discontinuous and the utility of ERT, in combination with other methods, to investigate permafrost thickness, spatial extent and ice content for infrastructure planning or climate change studies. Abstract Copyright (2010), John Wiley & Sons, Ltd.
12035701 Murton, J., editor. In honour of Professor Charles Harris: Permafrost and Periglacial Processes, 22(4), p. 273-391, illus., December 2011. Individual papers within scope are cited separately.
12035703 Ross, N. (University of Edinburgh, School of GeoSciences, Edinburgh, United Kingdom); Harris, C.; Brabham, P. J. and Sheppard, T. H. Internal structure and geological context of ramparted depressions, Llanpumsaint, Wales: in In honour of Professor Charles Harris (Murton, J., editor), Permafrost and Periglacial Processes, 22(4), p. 291-305, illus. incl. sketch map, 45 ref., December 2011.
In Europe, ramparted depressions have traditionally been interpreted as the relict forms of periglacial ground-ice mounds. In many cases, however, such interpretations have been based on limited subsurface evidence. We present detailed sedimentological and geophysical investigations of ramparted depressions from Llanpumsaint, Wales. These data are used to establish internal structure and to evaluate possible mechanisms for landform formation. Borehole and geophysical data have revealed a thick (~30 m) sequence of glaciolacustrine sediments beneath the study site. The geological context (drainage of a large proglacial lake) would have been conducive to the formation of: (i) permafrost-related ground-ice mounds, at times when exposed frost-susceptible glaciolacustrine sediments were subject to permafrost aggradation; and (ii) craters associated with the in-situ meltout of blocks of glacier ice grounded in the lake during periods of falling water levels. Rampart deformation structures are consistent with both models, but units of sand and gravel within the ramparts favor a hypothesis that these landforms represent the collapsed remains of ground-ice mounds. This study highlights the importance of recognizing and evaluating all possible (periglacial and non-periglacial) models for the development of ramparted depressions. We recommend that future studies carefully consider all possible mechanisms of formation, particularly where subsurface information is limited. Abstract Copyright (2010), John Wiley & Sons, Ltd.
12033387 Zhuang, Guangsheng (University of California Santa Cruz, Department of Earth and Planetary Sciences, Santa Cruz, CA); Hourigan, Jeremy K.; Koch, Paul L.; Ritts, Bradley D. and Kent-Corson, Malinda L. Isotopic constraints on intensified aridity in Central Asia around 12 Ma: Earth and Planetary Science Letters, 312(1-2), p. 152-163, illus. incl. geol. sketch maps, 93 ref., December 1, 2011.
The relationship between central Asian aridification and the evolution of the Himalayan-Tibetan orogen remains elusive. New isotopic data from pedogenic and lacustrine carbonates sampled from well-dated Neogene strata (15.7-1.8 Ma) in the northeastern Qaidam basin of the northern Tibetan Plateau identify a positive shift of ~ 2.5 ppm in d18O values from 12 Ma to 10.7 Ma. High values were maintained until ~ 3.3 Ma when d18O values drop by 1 ppm. The timing of the positive shift in d18O values is remarkably consistent with isotopic records from a vast region along and within the northern Tibetan Plateau. Isotopic, mineralogical, petrologic, and facies analyses suggest that diagenetic effects and detrital contamination are minimal. The positive shift in d18O values, as well as high d13C values from pedogenic carbonates (which are suggestive of low soil respiration rates), is interpreted to indicate intensified aridity in central Asia ca. 12 Ma. The recognition of intensified aridity is critical to understanding the climatic effects of the development of the Himalayan-Tibetan orogen. We attribute this climatic change in the central Asia to: (1) retreat of Paratethys from central Asia, strengthening the seasonal contrast and resulting in the loss of a nearby moisture source; (2) attainment of high elevations in the Himalayas and south-central Tibet, blocking moisture-bearing air masses from the Indian and Pacific oceans; and (3) enhanced isolation and outward growth of the northern Tibetan Plateau. The negative shift around 3.3 Ma might be related to the onset of Northern Hemisphere glaciation, intensification of the East Asia monsoon, and/or effects of orographic rain-out.
12032911 Fillion, Marie-Hélène (Université Laval, Département de Génie Civil, Quebec, PQ, Canada); Côté, Jean and Konrad, Jean-Marie. Thermal radiation and conduction properties of materials ranging from sand to rock-fill: Canadian Geotechnical Journal = Revue Canadienne de Géotechnique, 48(4), p. 532-542, illus. incl. 4 tables, 115 ref., April 2011.
This paper presents an experimental study on thermal radiation and the thermal conductivity of rock-fill materials using a 1 m ´ 1 m ´ 1 m heat transfer cell. Testing temperatures are applied by temperature-controlled fluid circulation at the top and bottom of the sample. Heat flux and temperature profiles are measured to establish the effective thermal conductivity le, which includes contributions from both conduction and radiation heat transfer mechanisms. The materials studied had an equivalent particle size (d10) ranging from 90 to 100 mm and porosity (n) ranging from 0.37 to 0.41. The experimental results showed that thermal radiation greatly affects the effective thermal conductivity of materials with le values ranging from 0.71 to 1.02 W·m-1·K-1, compared with a typical value of 0.36 W·m-1·K-1 for conduction alone. As expected, the effective thermal conductivity increased with particle size. An effective thermal conductivity model has been proposed, and predictions have been successfully compared with the experimental results. Radiation heat transfer becomes significant for d10 higher than 10 mm and predominant at values higher than 90 mm. The results of the study also suggest that the cooling potential of convection embankments used to preserve permafrost conditions may not be as efficient as expected because of ignored radiation effects.
12034572 Cheek, L. C. (Brown University, Department of Geological Sciences, Providence, RI); Pieters, C. M.; Boardman, Joseph W.; Clark, R. N.; Combe, Jean-Philippe; Head, J. W.; Isaacson, P. J.; McCord, Thomas B.; Moriarty, D.; Nettles, Jeffrey W.; Petro, Noah E.; Sunshine, J. M. and Taylor, L. A. Goldschmidt Crater and the Moon's north polar region; results from the Moon Mineralogy Mapper (M3): Journal of Geophysical Research, 116(E), Citation E00G02, illus. incl. 2 tables, 22 ref., 2011. Supplemental information/data is available in the online version of this article.
Soils within the impact crater Goldschmidt have been identified as spectrally distinct from the local highland material. High spatial and spectral resolution data from the Moon Mineralogy Mapper (M3) on the Chandrayaan-1 orbiter are used to examine the character of Goldschmidt crater in detail. Spectral parameters applied to a north polar mosaic of M3 data are used to discern large-scale compositional trends at the northern high latitudes, and spectra from three widely separated regions are compared to spectra from Goldschmidt. The results highlight the compositional diversity of the lunar nearside, in particular, where feldspathic soils with a low-Ca pyroxene component are pervasive, but exclusively feldspathic regions and small areas of basaltic composition are also observed. Additionally, we find that the relative strengths of the diagnostic OH/H2O absorption feature near 3000 nm are correlated with the mineralogy of the host material. On both global and local scales, the strongest hydrous absorptions occur on the more feldspathic surfaces. Thus, M3 data suggest that while the feldspathic soils within Goldschmidt crater are enhanced in OH/H2O compared to the relatively mafic nearside polar highlands, their hydration signatures are similar to those observed in the feldspathic highlands on the farside.
12035168 Ostapenko, Lyudmila Anatol'yevna (Yangeologiya, Batagay, Russian Federation); Aristov, Vasiliy Vasil'yevich; Ryzhov, Oleg Borisovich; Rikhonova, Nataliya Vladimirovna; Zadorozhnyy, Dmitriy Nikolayevich; Shirokov, Vasiliy Vladimirovich; Bogdanovich, Yuriy Ivanovich and Gerasimova, Valentina Nikolayevna. Usloviya formirovaniya zony okisleniya na mestorozhdenii Kimpiche (zapadnoye Verkhoyan'ye) [Formation of oxidation zone in the Kimpiche Deposit (western Verkhoyansk region)]: Otechestvennaya Geologiya, 2011(1), p. 43-58 (English sum.), illus. incl. 6 tables, 12 ref., 2011.
Major formative controls of the oxidation profile in general and individual supergenic processes are established, i.e., structural features of the deposit along with mineralogy of ores and host rocks. The supergenic profile was developed before and during the erosion stages under humid climate; formation of supergenic minerals kept on going with cooling of the climate and the onset of permafrost. Alkaline environment prevailed in the weathering profile, hence insignificant redistribution and transport of the ore-forming chemical elements and, consequently, practical absence of the oxidation profile within the deposit.
12032057 Van Hoesen, John G. (Green Mountain College, Department of Environmental Studies, Poultney, VT) and Orndorff, Richard L. The morphology and spatial distribution of late Quaternary periglacial landforms, Snake Range, Nevada; a GIS-based approach to prioritizing field sites: Journal of the Arizona-Nevada Academy of Science, 43(1), p. 48-60, illus. incl. 2 tables, geol. sketch maps, 45 ref., 2011.
We present new data describing relict periglacial landforms preserved in the interior Great Basin of the southwestern United States. This summary is significant because a thorough understanding of the occurrence and spatial distribution of these landforms is still lacking after 60 years of geomorphic studies in this region. This is largely because many land-forms are often un-recognized and because many mountains in the Great Basin are remote and offer poor access. To help address this knowledge gap, we use a GIS with high-resolution imagery and field mapping to identify and describe features that indicate a locally extensive periglacial environment existed in the Snake Range of east-central Nevada during the Late Quaternary. We also compare the location of these landforms with solar radiation models produced using ESRI's Solar Analyst to evaluate the efficacy of using solar modeling as means to predict suitable field sites for peri-glacial landforms. This simple modeling technique accurately identifies the location of known periglacial landforms in the Snake Range and therefore we believe it could be used to prioritize sites of interest throughout the Great Basin.
12034545 Bendle, James A. (University of Bristol, School of Chemistry, Organic Geochemistry Unit, Bristol Biogeochemistry Research Centre, Bristol, United Kingdom); Weijers, Johan W. H.; Maslin, Mark A.; Sinninghe Damste, Jaap S.; Schouten, Stefan; Hopmans, Ellen C.; Boot, Christopher S. and Pancost, Richard D. Major changes in glacial and Holocene terrestrial temperatures and sources of organic carbon recorded in the Amazon Fan by tetraether lipids: Geochemistry, Geophysics, Geosystems - G3, 11(12), Citation Q12007, illus. incl. 1 table, 62 ref., 2010.
The Amazon basin is a major component of the global carbon and hydrological cycles, a significant natural source of methane, and home to remarkable biodiversity and endemism. Reconstructing past climate changes in the Amazon basin is important for a better understanding of the effect of such changes on these critical functions of the basin. Using a novel biomarker proxy, based on the membrane lipids of soil bacteria with a new regional calibration, we present a reconstruction of changes in mean annual air temperatures for the Amazon catchment during the last 37 kyr B.P. Biomarkers were extracted from Ocean Drilling Program sediment core ODP942 recovered from the Amazon fan. The Amazon fan is a major depository for terrestrial sediments, with the advantage that the terrestrial material captured reflects a regional integration of the whole river catchment. The reconstructed tropical Amazonian temperatures were ~5°C cooler at the Last Glacial Maximum (~21°C) compared to modern values (~26°C). This is in agreement with previous estimates of tropical continental temperatures in the tropical Amazon basin and tropical Africa during the Last Glacial Maximum. Moreover, we also illustrate how the soil bacterial membrane lipid record reveals major changes in basin dynamics and sediment provenance during the glacial-Holocene transition, impacting the biomarker reconstructions from ~11 kyr onward.