September 2013 Permafrost Alert
The U.S. Permafrost Association, together with the American Geosciences Institute (AGI), is pleased to provide the following Permafrost Monthly Alerts (PMA). The AGI GeoRef service regularly scans the contents of over 3500 journals in 40 languages from the global geosciences literature, comprised of approximately 345 different sources. In addition to journals, special publications such as papers in proceedings and hard-to-find publications are provided. Each PMA represents a listing of the permafrost-related materials added to GeoRef during the previous month. Where available, a direct link to the publication is included, which provides access to the full document if you or your institution have a current online subscription.
Browse by Reference Type:
Serial | Conference
13083611 Gritsuk, I. I. (Russian Academy of Sciences, Institute for Water Problems, Moscow, Russian Federation); Debol'skaya, Ye. I.; Debol'skiy, V. K.; Maslikova, O. Ya. and Ponomarev, N. K. Vliyaniye dozhdevykh osadkov na deformatsii beregovogo sklona rusel rek v usloviyakh mnogoletnemerzlykh porod [Influence of rain on river bank deformation in the permafrost zone]: Led i Sneg = Ice and Snow, 119, p. 73-78 (English sum.), illus., 9 ref., 2012.
We studied in the lab the interaction of river runoff from frozen soil, simulating the upper, active-layer, changing the thermal (warning) and mechanical (impact of rain) external influences. We determined the time of thawing of ground and infiltration in soil, sediment transport along the lines under the influence of slope flows, caused by both natural thawing permafrost and storm flows. A mathematical model for predicting the dynamics of river channels in the permafrost under the influence of external factors is suggested.
13080988 Zech, Roland. A permafrost glacial hypothesis; permafrost carbon might help explaining the Pleistocene ice ages: Eiszeitalter und Gegenwart - Quarternary Science Journal, 61(1), p. 84-92, 63 ref., 2012.
Over the past several ~100 ka glacial-interglacial cycles, the concentration of atmospheric CO2 was closely coupled to global temperature, which indicates the importance of CO2 as a greenhouse gas. The reasons for changes in atmospheric CO2 have mainly been sought in the ocean, but remain elusive. Moreover, the mid-Pleistocene transition from the '41 ka world' during the early Pleistocene before ~0.7 Ma to the ~100 ka ice age cycles is poorly understood. The classical Milankovitch theory of summer insolation forcing at high northern latitudes can not fully explain the Pleistocene ice age rhythm. Based on the recent findings that the amount of soil organic carbon stored in high-latitude permafrost regions has been greatly underestimated and the simple logic that permafrost regions and respective carbon pools were likely much larger during glacials than during interglacials, a 'permafrost glacial hypothesis' is proposed: (i) Gradual sequestration of CO2 in permafrost soils during coolings and rapid release of CO2 and methane during terminations, respectively, provide important positive feedbacks for the climate. (ii) Integrated annual insolation at the southern and thus most sensitive permafrost boundary may act as a trigger for global climate changes. (iii) The mid-Pleistocene transition might be readily explained with permafrost extents reaching ~45°N during the long-term Pleistocene cooling, resulting in a transition from high-latitude obliquity (~41 ka) to mid-latitude eccentricity (~100 ka) forcing.
13077635 Bischoff, Juliane (Alfred Wegener Institute for Polar and Marine Research, Research Department Potsdam, Potsdam, Germany); Mangelsdorf, Kai; Gattinger, Andreas; Schloter, Michael; Kurchatova, Anna N.; Herzschuh, Ulrike and Wagner, Dirk. Response of methanogenic Archaea to late Pleistocene and Holocene climate changes in the Siberian Arctic: Global Biogeochemical Cycles, 27(2), p. 305-317, illus. incl. sketch map, 60 ref., April 2013.
In order to investigate the link between the methane dynamics in permafrost deposits and climate changes in the past, we studied the abundance, composition, and methane production of methanogenic communities in Late Pleistocene and Holocene sediments of the Siberian Arctic. We detected intervals of increased methane concentrations in Late Pleistocene and Holocene deposits along a 42 ka old permafrost sequence from Kurungnakh Island in the Lena Delta (northeast Siberia). Increased amounts of archaeal life markers (intact phospholipid ethers) and a high variety in genetic fingerprints detected by 16S ribosomal ribonucleic acid gene analyses of methanogenic archaea suggest presently living and presumably active methanogenic archaea in distinct layers predominantly in Holocene deposits, but also in deep frozen ground at 17 m depth. Potential methanogenic activity was confirmed by incubation experiments. By comparing methane concentrations, microbial incubation experiments, gene analysis of methanogens, and microbial life markers (intact phospholipid esters and ethers) to already partly degraded membrane lipids, such as archaeol and isoprenoid glycerol dialkyl glycerol tetraethers, we demonstrated that archaeol likely represents a signal of past methanogenic archaea. The archaeol signal was used to reconstruct the response of methanogenic communities to past temperature changes in the Siberian Arctic, and the data suggest higher methane emissions occurred during warm periods, particularly during an interval in the Late Pleistocene and during the Holocene. This new data on present and past methanogenic communities in the Siberian terrestrial permafrost imply that these microorganisms will respond to the predicted future temperature rise in the Arctic with increasing methane production, as demonstrated in previous warmer periods. Abstract Copyright (2012), . American Geophysical Union. All Rights Reserved.
13078641 Beylich, Achim A. (Geological Survey of Norway, Trondheim, Norway); Lamoureux, Scott F. and Decaulne, Arnelle. The SEDIBUD (sediment budgets in cold environments) programme; ongoing activities and selected key tasks for the coming years: in Sedimentary fluxes and budgets in natural and anthropogenically modified landscapes; effects of climate change and land use change on geomorphic processes (Beylich, Achim A., editor; et al.), Geomorphology, 167-168, p. 2-3, 11 ref., September 15, 2012.
Projected climate change in cold environments is expected to alter melt-season duration and intensity, along with the number of extreme rainfall events, total annual precipitation and the balance between snowfall and rainfall. In addition, changes to the thermal balance are expected to reduce the extent of permafrost and seasonal ground frost and increase active layer depths. The combined effects of these changes will alter surface environments in cold climate regions and change the fluxes of sediments, nutrients and solutes, but the absence of data, coordinated process monitoring and coordinated quantitative analysis to understand the sensitivity of the Earth surface environment are acute in cold climate environments. The International Association of Geomorphologists (I.A.G./A.I.G.) SEDIBUD (Sediment Budgets in Cold Environments) Programme has been formed to address this key knowledge gap and builds on the earlier European Science Foundation (ESF) SEDIFLUX (Sedimentary Source-to-Sink-Fluxes in Cold Environments) Network. Coordinated efforts are carried out to monitor, quantify, compare and model sedimentary fluxes and possible effects of predicted climate change in currently 44 selected SEDIBUD Key Test Sites (cold climate environment catchments) worldwide. Abstract Copyright (2012) Elsevier, B.V.
13078643 Saemundsson, Thosteinn (Natural Research Centre of Northwestern Iceland, Iceland); Arnalds, Olafur; Kneisel, Christof; Jonsson, Helgi P. and Decaulne, Arnelle. The Orravatnsrustir palsa site in central Iceland; palsas in an aeolian sedimentation environment: in Sedimentary fluxes and budgets in natural and anthropogenically modified landscapes; effects of climate change and land use change on geomorphic processes (Beylich, Achim A., editor; et al.), Geomorphology, 167-168, p. 13-20, illus. incl. 1 table, sketch maps, 46 ref., September 15, 2012.
The Orravatnsrustir palsa site, located north of the Hofsjokull glacier in Central Iceland, has well developed palsas located in a valley-like depression at 710-715 m a.s.l. and stands in remarkable contrast to the surrounding desert-like highland plateau. The purpose of this paper is to give an overview of the Orravatnsrustir palsa site, geographic distribution and geomorphic statistics related to size and permafrost thicknesses of the palsas, including recent changes. Icelandic palsas exhibit characteristics of both organic palsas and lithalsa (frozen mineral soil). They are subjected to intense aeolian deposition of volcanic materials. The palsas are often 40-200 cm high, with a 40-80 cm thick active layer and permafrost reaching more than 5 m depth. Measurements of the size of the palsas and the thickness of the active layer which started in 2001 indicate that their size is decreasing and the thickness of the active layer is increasing. These results are in agreement with the general warming trend which has occurred in Iceland during the last decade. Abstract Copyright (2012) Elsevier, B.V.
13081580 Bouchard, Frédéric (Institut National de la Recherche Scientifique, Centre Eau Terre Environnement, Quebec City, QC, Canada); Pienitz, Reinhard; Ortiz, Joseph D.; Francus, Pierre and Laurion, Isabelle. Palaeolimnological conditions inferred from fossil diatom assemblages and derivative spectral properties of sediments in thermokarst ponds of subarctic Quebec, Canada: Boreas, 42(3), p. 575-595, illus. incl. 3 tables, sketch map, 80 ref., July 2013. Supplemental information/data is available in the online version of this article.
Thermokarst ponds are widespread in arctic and subarctic regions, but little is known about their temporal evolution prior to human observations. This paper presents a pioneer biostratigraphic study conducted at a subarctic site with limnologically contrasted ponds located on the eastern shore of Hudson Bay, Canada. Fossil diatom and visible near infrared (VNIR) derivative spectral analyses were performed on short sediment cores, confirming the occurrence of three distinct stratigraphic facies as already inferred from an anterior sedimentological study: a lacustrine upper facies (UF) and a marine lower facies (LF), separated by an organic-rich/peat transitional zone (TZ). Diatoms were almost absent from LF, but increased significantly in both TZ and UF. Identified diatom taxa were mainly benthic species (e.g. genera Fragilaria, Pinnularia), and their down-core distribution appeared to be related to dissolved organic carbon (DOC) and possibly pH conditions. Diatom-inferred DOC showed a decreasing trend towards the surface (potentially associated with an increase in pH), inverse to the general trend in this region, suggesting the action of other mechanisms on DOC, such as exhaustion of external inputs from limited catchments and the role of discontinuous peat layers (former surfaces of permafrost mounds) during the initial stages of pond formation. These bryophilous substrates in aerophilic habitats probably controlled diatom community composition. The combination of diatom and VNIR data revealed similar trends between (i) opal (amorphous silica) and diatom abundances; (ii) eukaryotic/prokaryotic algae ratio and anoxia or hypoxia in bottom waters; and (iii) limonite (iron oxide) and redox conditions in surface sediments. These findings indicate that diatom community changes and pond limnological evolution in the recent past were controlled mainly by autogenic processes (e.g. local vegetation/soil development, peat accumulation and erosion), rather than by allogenic forcing mechanisms (e.g. precipitation and temperature, geochemical leaching of the surrounding glaciomarine sediments). Abstract Copyright (2012), The Boreas Collegium.
13083203 Lessovaia, Sofia (Saint Petersburg State University, Faculty of Geography and Geoecology, St. Petersburg, Russian Federation); Dultz, Stefan; Polekhovsky, Yurii; Krupskaya, Viktoria; Vigasina, Marina and Melchakova, Lubov. Rock control of pedogenic clay mineral formation in a shallow soil from serpentinous dunite in the Polar Urals, Russia: in Clays and soils (Churchman, Jock, editor; et al.), Applied Clay Science, 64, p. 4-11, illus. incl. 2 tables, 2 plates, 41 ref., August 2012.
The transformation of primary and secondary minerals in a recent shallow soil (Haplic Cryosol (Reductaquic)) from a highly weatherable ultrabasic rock (serpentinous dunite) of the mountainous tundra of the Polar Urals was determined. Primary and secondary mineral associations were analyzed in thin sections, by electron microscopy, X-ray diffraction, IR-spectroscopy, and thermal analysis. The susceptibility of the fresh rock for weathering was characterized by the micromorphology of the connective pores. Disintegration of the rock resulted in relatively high amounts of inherited olivine, serpentine, talc, and chlorite in the fine soil. Element release from fresh mineral surfaces exposed also in internal pore systems of rock fragments is a decisive factor for the appearance of secondary minerals in the fine soil. Secondary minerals are two smectites, saponite and nontronite, and vermiculite. Especially the silicates rich in Mg, olivine and serpentine with lower contents in the <1mm fraction of the soil horizons in comparison with the fresh rock, are the most probable sources for saponite. The source of nontronite is not fully understood. It is supposed that olivine and serpentine and/or pyroxenes that are allochthonous for serpentinous dunite and inherited from harzburgite affect their formation in the soil. Most probably vermiculite is the result of chlorite transformation. Content of smectites decreases in the upper horizons of the soil whereas in an opposite trend, vermiculite increases. Supposedly biota, especially moss and lichens, have a strong contribution to silicate weathering which leads to saponite and nontronite decomposition and chlorite transformation despite neutral to alkaline pH-values in the whole soil. Relatively high amounts of dithionite and oxalate soluble Fe indicate a marked release of Fe by silicate weathering. For element release freezing in the permafrost environment seems to have a decisive role by affecting pore systems in the rock and the soil skeleton fraction. Abstract Copyright (2012) Elsevier, B.V.
13080989 Grube, Alf. Zur periglaziären Bildung und Überformung rinnenartiger Strukturen im Jungmoränengebiet Süd-Holsteins [Periglacial formation and reshaping of channel-like structures in the young moraine area of Schleswig-Holstein]: Eiszeitalter und Gegenwart - Quarternary Science Journal, 61(1), p. 69-83, 22 ref., 2012.
The Bargfeld-Stegen sandur area (Schleswig-Holstein) north of Hamburg is characterized by an intense periglacial shaping. Channel-like features, hereinafter referred to as channels, up to 26 meters wide and 3.5 meters deep, as periglacial forms are incisive. Similar features can be observed in Itzehoe, Tangstedt (Norderstedt) and Schalkholz. Common features of these channels are: a usually shallow-convex cross section, an infill including re-deposited till, undercutting and other fluvial characteristics at the flanks, flat base eroded down to a boundary surface (permafrost), a diapir-like uplift of channel fillings in the upper channel parts and at the channel flanks, the parallel channel courses, sand-filled secondary channels and a linear progression of channels, preferably diagonally to the ice movement. The structures seem to appear mainly in slope positions in the marginal zones of the regional till-cover. Different forms of their generation have to be considered. They were probably mainly formed during the periglacial climate (Weichselian) by periglacial-fluvial processes (abluation) combined with solifluction.
13081714 Klemm, Juliane (Alfred Wegener Institute for Polar and Marine Research, Research Unit Potsdam, Potsdam, Germany); Herzschuh, Ulrike; Pisaric, Michael F. J.; Telford, Richard J.; Heim, Birgit and Pestryakova, Luidmila A. A pollen-climate transfer function from the tundra and taiga vegetation in Arctic Siberia and its applicability to a Holocene record: Palaeogeography, Palaeoclimatology, Palaeoecology, 386, p. 702-713, illus. incl. 2 tables, sketch maps, 110 ref., September 15, 2013.
This study aims to establish, evaluate, and apply a modern pollen-climate transfer function from the transition zone between arctic tundra and light-needled taiga in Arctic Siberia. Lacustrine samples (n=96) from the northern Siberian lowlands of Yakutia were collected along four north-to-south transects crossing the arctic forest line. Samples span a broad temperature and precipitation gradient (mean July temperature, TJuly: 7.5-18.7°C; mean annual precipitation, Pann: 114-315mm/yr). Redundancy analyses are used to examine the relationship between the modern pollen signal and corresponding vegetation types and climate. Performance of transfer functions for TJuly and Pann were cross-validated and tested for spatial autocorrelation effects. The root mean square errors of prediction are 1.67°C for TJuly and 40 mm/yr for Pann. A climate reconstruction based on fossil pollen spectra from a Siberian Arctic lake sediment core spanning the Holocene yielded cold conditions for the Late Glacial (1-2°C below present TJuly). Warm and moist conditions were reconstructed for the early to mid Holocene (2°C higher TJuly than present), and climate conditions similar to modern ones were reconstructed for the last 4000 years. In conclusion, our modern pollen data set fills the gap of existing regional calibration sets with regard to the underrepresented Siberian tundra-taiga transition zone. The Holocene climate reconstruction indicates that the temperature deviation from modern values was only moderate despite the assumed Arctic sensitivity to present climate change. Abstract Copyright (2013) Elsevier, B.V.
13077657 Zhu, Xudong (Purdue University, Department of Earth, Atmospheric, and Planetary Sciences, West Lafayette, IN); Zhuang, Qianlai; Qin, Zhangcai; Glagolev, Mikhail and Song, Lulu. Estimating wetland methane emissions from the northern high latitudes from 1990 to 2009 using artificial neural networks: Global Biogeochemical Cycles, 27(2), p. 592-604, illus. incl. 3 tables, 69 ref., April 2013.
Methane (CH4) emissions from wetland ecosystems in northern high latitudes provide a potentially positive feedback to global climate warming. Large uncertainties still remain in estimating wetland CH4 emisions at regional scales. Here we develop a statistical model of CH4 emissions using an artificial neural network (ANN) approach and field observations of CH4 fluxes. Six explanatory variables (air temperature, precipitation, water table depth, soil organic carbon, soil total porosity, and soil pH) are included in the development of ANN models, which are then extrapolated to the northern high latitudes to estimate monthly CH4 emissions from 1990 to 2009. We estimate that the annual wetland CH4 source from the northern high latitudes (north of 45°N) is 48.7 Tg CH4 yr-1 (1 Tg = 1012 g) with an uncertainty range of 44.0~53.7 Tg CH4 yr-1. The estimated wetland CH4 emissions show a large spatial variability over the northern high latitudes, due to variations in hydrology, climate, and soil conditions. Significant interannual and seasonal variations of wetland CH4 emissions exist in the past 2 decades, and the emissions in this period are most sensitive to variations in water table position. To improve future assessment of wetland CH4 dynamics in this region, research priorities should be directed to better characterizing hydrological processes of wetlands, including temporal dynamics of water table position and spatial dynamics of wetland areas. Abstract Copyright (2013), . American Geophysical Union. All Rights Reserved.
13078646 Gärtner-Roer, I. (University of Zurich, Department of Geography, Zurich, Switzerland). Sediment transfer rates of two active rock glaciers in the Swiss Alps: in Sedimentary fluxes and budgets in natural and anthropogenically modified landscapes; effects of climate change and land use change on geomorphic processes (Beylich, Achim A., editor; et al.), Geomorphology, 167-168, p. 45-50, illus. incl. 1 table, sketch map, 48 ref., September 15, 2012.
High mountain geosystems are characterized by an extensive transfer of mass and energy, reflected in its geomorphological processes shaping the landscape. Within the periglacial belt, rockglaciers represent important sediment storages and transport components. In this study, sediment transfer rates are quantified for two rockglaciers with different characteristics, based on a multi-method approach combining geomorphological mapping, DTM analyses, digital photogrammetry and geodetic survey. For the first time different velocity values, resulting from a kinematic monitoring over two decades, are included. Due to the different characteristics of the landforms (especially thickness and horizontal velocity), a wide range of sediment transfer rates results from this study: between 0.24 and 1.1 millio nt/a, with the maximum value for a rockglacier with a relatively small mass but high deformation rates. Abstract Copyright (2012) Elsevier, B.V.
13082065 Bowen, Gabriel J. (University of Utah, Department of Geology & Geophysics, Salt Lake City, UT). Up in smoke; a role for organic carbon feedbacks in Paleogene hyperthermals: Global and Planetary Change, 109, p. 18-29, illus., 94 ref., October 2013.
Sedimentary archives from the world's oceans and continents indicate that as the world warmed from the mild climate conditions of the mid-Paleocene to the extreme global warmth of the Early Eocene, a series of abrupt perturbations shifted the carbon isotope budget of the ocean/atmosphere/biosphere (exogenic) system. Consideration of the rates and magnitude of carbon isotope change, along with independent evidence for ocean acidification, dictates that these "hyperthermal" events involved the transfer of thousands of petagrams of reduced carbon to the actively cycling exogenic system. Careful study of stratigraphically resolved carbon isotope records spanning the hyperthermals, in particular the first and most prominent of them, the Paleocene-Eocene Thermal Maximum (PETM), has informed our understanding of carbon cycle perturbation during these events. Several important features of these records, however, remain difficult to explain with conventional ocean/atmosphere carbon cycle models, including divergence of carbon isotope records from marine and terrestrial systems, a prolonged interval of low d13C values during the 'body' of the PETM carbon isotope excursion (CIE), and rapid recovery of d13C values at the CIE termination. Here I use data from well-resolved, independently dated marine and terrestrial PETM carbon isotope records to characterize these distinctive and challenging features of the records and discuss their implications. I then propose a simple set of mechanisms, involving climatically-mediated increases in organic carbon respiration rates and CO2-driven changes in photosynthetic 13C discrimination triggered by an initial release of carbon from geological reservoirs, which produce patterns, magnitudes, and rates of carbon isotope change consistent with records from the event. If the proposed scenario is correct, it suggests that the land plants and soils may have first released, and then taken up, several thousand Pg of carbon during the early and late stages of the event, with concordant changes in rates of organic carbon burial in sediments. Full elaboration and rigorous evaluation of the proposed scenario will require additional work, but the initial results suggest that organic carbon feedbacks, similar in nature to those being explored in work on modern and future Earth systems, may have played a significant role in shaping global changes at the Paleocene-Eocene boundary. Abstract Copyright (2013) Elsevier, B.V.
13077547 Mejías, J. H. (Instituto de Investigaciones Agropecuarias, Centro Regional de Investigación Carillanca, Temuco, Chile); Alfaro, M. and Harsh, J. Approaching environmental phosphorus limits on a volcanic soil of southern Chile: Geoderma, 207-208, p. 49-57, illus. incl. 2 tables, 74 ref., October 2013.
Unexpected incidental phosphorus (P) losses from volcanic soils recently threatened water quality in Southern Chile. Such soils are generally thought of as P sinks and no rapid indicators exist that reliably predict the potential for these soils to release P to water supplies. In this study we propose a local buffering capacity indicator (BCp) already in use for agronomic purposes to determine a threshold BCp value to predict the onset of significant P loss. The BCp represents the amount of P required to increase the value of Olsen-P by 1 mg kg-1 at 0.2 m soil depth per hectare (kg P ha-1). Changes in BCp, and soil P variables were evaluated in a volcanic soil from the Osorno series in Southern Chile. The treated soil was incubated for 90 days with increasing P rates (0, 10, 25, 50, 100, 500 and 1000 mg P kg-1 soil). A segmented linear model was used to identify the BCp threshold value from the relationship between the BCp and water-soluble soil P (Pw). Significant changes in soil P status and P sorption parameters were evident only after the soil was treated with the highest P rates, denoting the high P sorption capacity of the soil. Ammonium oxalate extractable P (Pox), Olsen-P, Pw, and the degree of P saturation (DPS) increased with P rates higher than 500 mg kg-1. This was coincident with a significant decrease of the BCp value. For this particular soil, the segmented model gave a BCp threshold of 15.1 kg ha-1 (R2=0.96, P<0.05) below which Pw increased abruptly. This BCp was equivalent to an Olsen-P of 53.4 mg P kg-1, which is two times higher than the optimum agronomic value recommended for most crops and pastures of Southern Chile. Given that the BCp is already in widespread use as an agronomic indicator in this region, we show that it also has promise as an environmental indicator of a soil's susceptibility to soil P loss. Abstract Copyright (2013) Elsevier, B.V.
13082120 Vorren, Tore O. (University of Tromso, Department of Geology, Tromso, Norway); Vorren, Karl-Dag; Aasheim, Odd; Dahlgren, K. I. Torbjorn; Forwick, Matthias and Hassel, Kristian. Palaeoenvironment in northern Norway between 22.2 and 14.5 cal. ka BP: Boreas, 42(4), p. 876-895, illus. incl. strat. cols., 1 table, geol. sketch maps, 63 ref., October 2013.
The stratigraphy of lake Endletvatn on northern Andoya, northern Norway, has been revisited to improve the understanding of the palaeoenvironment in the region during the Last Glacial Maximum (LGM). Four high-quality cores were analysed with respect to various lithological parameters and macrofossil content, supplemented by 47 AMS radiocarbon dates. The sediments indicate a low-energy environment with a mean sedimentation rate of 0.5 mm a-1. We infer perennially frozen ground in the surroundings during the LGM. Climate proxies indicate a high arctic climate (i.e. July mean temperatures between 0 and 3°C) throughout most of the LGM. The warmest periods are marked by a rise in seed, moss and animal fossils, and often also by higher organic production in the lake. These periods took place from 21.4 to 20.1, from 18.8 to 18.1, around 17 and from 16.4 cal. ka BP onwards. The shifts between the different climatic regimes occurred rapidly - probably during one or two decades. The present data do not support recently published conclusions stating that Picea, Pinus and Betula pubescens grew on Andoya during parts of the LGM. The highest relative sea level after the final deglaciation on northern Andoya is bracketed between 36 and 38 m a.s.l. It occurred between 21.0 and 20.3 cal. ka BP, peaking around 20.7 cal. ka BP. The final deglaciation of the northern tip of Andoya occurred 22.2 cal. ka BP. Then the western margin of the Andfjorden ice stream receded to the Kjolhaugen Moraine and shortly thereafter to the Endleten Moraine. Our research confirms that northern Andoya is a key location for understanding the natural environment in northwestern Europe during the LGM. Abstract Copyright (2013), The Boreas Collegium.
13078168 Long, Michael (University of Dublin, School of Civil, Structural and Environmental Engineering, Dublin, Ireland) and Boylan, Noel. Predictions of settlement in peat soils: Quarterly Journal of Engineering Geology and Hydrogeology, 46(3), p. 303-322, illus., 63 ref., August 2013.
Predictions from laboratory tests of the compression behaviour of peat from 14 sites are compared with full-scale field loading at five sites. Data presented confirm the heterogeneous nature of the deposits. However, for typical engineering works, calculations based on laboratory test data are likely to give reasonable predictions of the magnitude of immediate and primary compression. Standard (20 mm thickness) samples may give misleading data on time for primary consolidation. Thicker samples (e.g. 50 mm) should be used. Sampling by conventional samplers, as used for mineral soils, can cause densification of the peat, resulting in underestimation of actual settlement. Block samples or sample tubes with serrated cutting edges are recommended for peat soils. It was found that the data presented follow the Ca/Cc law of compressibility. There is also is some evidence to suggest that the H2 scaling law may be applicable. Good correlations were found between vertical yield stress (pvy') and compression index (Cc) and index parameters such as water content (wi). Conventional staged construction with surcharge loading may be successfully applied to peat soils as long as adequate drainage exists to permit consolidation over reasonable time intervals.
13080012 Conway, Susan J. (Université de Nantes, Laboratoire de Planétologie et Géodynamique, Nantes, France) and Mangold, Nicolas. Evidence for Amazonian mid-latitude glaciation on Mars from impact crater asymmetry: Icarus, 225(1), p. 413-423, illus. incl. 2 tables, sketch map, 47 ref., July 2013.
13081454 Tfaily, Malak M. (Florida State University, Department of Chemistry and Biochemistry, Tallahassee, FL); Hamdan, Rasha; Corbett, Jane E.; Chanton, Jeffrey P.; Glaser, Paul H. and Cooper, William T. Investigating dissolved organic matter decomposition in northern peatlands using complimentary analytical techniques: Geochimica et Cosmochimica Acta, 112, p. 116-129, illus. incl. 1 table, 63 ref., July 1, 2013.
The chemical transformations that govern storage, degradation, and loss of organic matter in northern peatlands are poorly characterized, despite the significance of these peat deposits as pivotal reservoirs in the global carbon cycle. One of the most challenging problems concerns the character of dissolved organic matter (DOM) in peat porewaters, particularly higher-molecular weight compounds that may function either as non-reactive sinks or reactive intermediates for organic byproducts of microbial decay. The complexity of these large molecules has defied attempts to characterize their molecular structure in bulk samples with a high degree of precision. We therefore determined the composition and reactivity of DOM from representative bog and fen sites in the Glacial Lake Agassiz Peatlands (GLAP) in northern Minnesota, USA. We applied four complementary techniques: electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR MS), proton nuclear magnetic resonance spectroscopy (1H NMR), specific UV absorbance (SUVA) and excitation-emission matrix (EEM) fluorescence spectroscopy. We observed that the vast majority (>80%) of molecular formulas that appear in the surface bog DOM are also present at 2.9 m depth, indicating that much of DOM in the bog is resistant to microbial degradation. In contrast to bog samples, a considerable number of new compounds with low O/C and high H/C elemental ratios were observed in the 3m fen horizon relative to surface samples. These results indicate a more pronounced difference in the composition of surface and deep DOM in the fen. SUVA, determined at 254 nm, indicated significantly lower aromaticity in deep fen samples relative to deep bog samples. This trend was verified by 1H NMR. Aromatic and carbohydrate components represented up to 70% of deep bog DOM but comprised a much smaller proportion of deep fen DOM, which was dominated by functionalized and non-functionalized aliphatics. Molecular formula data determined by FT-ICR mass spectrometry were consistent with results from optical and NMR spectroscopy measurements and showed that compounds with low O/C and high H/C were generated with depth in the fen. Such compounds were absent in both surface fen and in surface and deep bog samples respectively, providing further evidence of qualitative and quantitative differences in the evolution of DOM in fens and bogs. These differences, attributed to either variations in source vegetation or environmental factors that render DOM more reactive in fen sites or less reactive in bog sites, have important implications for the response of peatlands to climate change, since climatic change leading to moister conditions may enhance the abundance of sedge-dominated fens and increase the pool of more labile soil carbon. Abstract Copyright (2013) Elsevier, B.V.
13081749 Kishtawal, C. M. (Purdue University, Department of Agronomy, West Lafayette, IN); Niyogi, Dev; Rajagopalan, Balaji; Rajeevan, M.; Jaiswal, N. and Mohanty, U. C. Enhancement of inland penetration of monsoon depressions in the Bay of Bengal due to prestorm ground wetness: Water Resources Research, 49(6), p. 3589-3600, illus., 54 ref., June 2013.
Observations of 408 monsoon low-pressure systems (MLPSs) including 196 monsoon depressions (MDs) that formed in the Bay of Bengal during the 1951-2007 period, and the gridded analysis of daily rainfall fields for the same period, were used to identify the association of antecedent rainfall (1 week average rainfall prior to the genesis of MLPS) with the genesis of MLPS and length of inland penetration by MDs. Prestorm rainfall is treated as a surrogate to prestorm ground wetness conditions due to unavailability of historical soil-moisture data over the monsoon region. These observations were analyzed using self-organizing maps (SOMs) to group nine different prestorm monsoon rainfall patterns into different transition states like active, active-to-break, break-to-active, break, etc. The analysis indicates that MLPS are four times more likely to form on a day during active monsoon state compared to break state. Analysis of MLPSs linked to each monsoon state represented by SOM nodes shows that MDs with higher inland penetration were associated with higher antecedent rainfall. On the other hand, there was no significant difference in low-level atmospheric circulation for MDs with shortest and longest inland penetration. Abstract Copyright (2013), . American Geophysical Union. All Rights Reserved.
13077651 Boyle, John F. (University of Liverpool, School of Environmental Sciences, Liverpool, United Kingdom); Chiverrell, Richard C.; Norton, Stephen A. and Plater, Andy J. A leaky model of long-term soil phosphorus dynamics: Global Biogeochemical Cycles, 27(2), p. 516-525, illus. incl. 3 tables, 31 ref., April 2013.
Soil phosphorus (P) leaks rapidly from newly formed land surfaces to upland rivers and lakes, surface water P concentrations peaking early before declining as soil apatite (Ca5(PO4)3(OH)) becomes depleted. We present lake sediment P profiles that record this leakage through the early Holocene. The results are entirely consistent with our re-analysis of published soil chronosequence data, but conflict with more recent quantitative interpretations of global soil P dynamics that identify far slower loss rates. P inherited from the bedrock on soil formation, long regarded as the major source for terrestrial ecosystems, only lasts ~104 years rather than the previously suggested 106 years, and thus is, globally, much less important in the long term than atmospheric supply. This changes the conceptualization of terrestrial P dynamics, with the "terminal steady state" of Walker and Syers (1976) being the norm not the exception, and with soil P export being little if at all controlled by biotic retention mechanisms. High early export of P from newly formed soil causes a peak in the productivity of terrestrial surface waters, before a decline as the soil P pool depletes. Globally, the 18 ´ 106 km2 of terrain exposed since the Last Glacial Maximum potentially produced a substantial surge in runoff P, with greatest impacts likely in high-latitude, restricted basin seas and maximal area of deglaciated terrain. Abstract Copyright (2013), . American Geophysical Union. All Rights Reserved.
13079673 Zwertvaegher, Ann (Ghent University, Department of Geology and Soil Science, Ghent, Belgium); Finke, Peter; de Reu, Jeroen; Vandenbohede, Alexander; Lebbe, Luc; Bats, Machteld; de Clercq, Wim; de Smedt, Philippe; Gelorini, Vanessa; Sergant, Joris; Antrop, Marc; Bourgeois, Jean; de Maeyer, Philippe; van Meirvenne, Marc; Verniers, Jacques and Crombé, Philippe. Reconstructing phreatic palaeogroundwater levels in a geoarchaeological context; a case study in Flanders, Belgium: Geoarchaeology, 28(2), p. 170-189, illus. incl. 5 tables, sketch maps, 70 ref., March 2013.
The complex debate on prehistoric settlement decisions is no longer tackled from a purely archaeological perspective but from a more landscape-oriented manner combined with archaeological evidence. Therefore, reconstruction of several components of the former landscape is needed. Here, we focus on the reconstruction of the groundwater table based on modeling. The depth of the phreatic aquifer influences, for example, soil formation processes and vegetation type. Furthermore, it directly influences settlement by the wetness of a site. Palaeogroundwater modeling of the phreatic aquifer was carried out to produce a series of full-coverage maps of the mean water table depth between 12.7 ka and the middle of the 20th century (1953) in Flanders, Belgium. The research focuses on the reconstruction of the input data and boundary conditions of the model and the model calibration. The model was calibrated for the 1924-1953 time period using drainage class maps. Archaeological site data and podzol occurrence data act as proxies for local drainage conditions over periods in the past. They also served as a control on the simulated phreatic palaeogroundwater levels. Model quality testing on an independent validation data set showed that the model predicts phreatic water table levels at the time of soil mapping well (mean error of 1.8 cm; root mean square error of 65.6 cm). Simulated hydrological conditions were in agreement with the occurrence of archaeological sites of Mesolithic to Roman age at 96% of the validation locations, and also with the occurrence of well-drained podzols at 97% of the validation locations. Abstract Copyright (2013), Wiley Periodicals, Inc.
13078648 Dixon, John C. (University of Arkansas, Department of Geosciences, Fayetville, AR); Campbell, Sean W. and Durham, Bill. Geologic nitrogen and climate change in the geochemical budget of Karkevagge, Swedish Lapland: in Sedimentary fluxes and budgets in natural and anthropogenically modified landscapes; effects of climate change and land use change on geomorphic processes (Beylich, Achim A., editor; et al.), Geomorphology, 167-168, p. 70-76, illus. incl. 2 tables, geol. sketch map, 37 ref., September 15, 2012.
While nitrogen is an essential nutrient for plant growth in the terrestrial environment and generally fixed by biological processes in soils, in Arctic and alpine environments N is a severely limited nutrient because of both climatic and soil constraints. It is widely believed that geologic nitrogen is such a small component of the nitrogen cycle that this source is generally not viewed as being a significant component. However, it has been estimated that in fact as much as 20% of the total nitrogen budget may be stored in geological materials and where N is severely limited such as in Arctic and alpine environments geologic N may in fact be a dominant source of N for biological processes. Nitrogen saturation may therefore have substantial impacts on geochemical cycles involving both soil and water chemistry. In order to determine the potential for the rocks and soils of Karkevagge to be significant sources of N samples of the principal rock units of the valley along with soil developed on a variety of rock types were sampled. Ammonia/ammonium contents were determined using ion chromatography. Ammonia/ammonium contents of the sampled rock materials display a wide range of abundances with marble containing a mean NH4 abundance of 4300 mg N kg, quartz schist 1600 mg N kg, biotite schist 4300 mg N kg, and garnet mica schist 4500 mg N kg. Soil ammonia/ammonium abundances were found to be 1600 mg N kg. N-pool abundances range from 2.5 kg m3 for marble to 8.7 for garnet mica schist. Soil N-pools were found to be 3.0 kg m3. The inorganic N present as ammonia/ammonium measured in bedrock represents substantial N-input into the geochemical budget. The N in bedrock originates from organically bound nitrogen associated with sediment or geothermal waters representing a mixture of sedimentary, mantle and meteoric sources. Nitrogen in the soil originates from the weathering of N-rich rocks, the presence of unweathered nitrate minerals or fluid inclusions released to the soil and ultimately to plants by assimilation by biota or nitrification. Geologic nitrogen in Karkevagge rocks and soils may represent a large and reactive pool with the potential for considerable impact on the geochemical system. To investigate the potential responses of nitrogen release, as well as other nutrients to increasing CO2 concentration scenarios, flow-through leaching experiments were conducted on crushed rock samples and soils from the study area. Leaching experiments revealed two to three fold increases in both N and K release with a tripling of carbon dioxide concentrations. Ammonium shows more rapid release than potassium which suggests substantial changes in nitrogen cycling with increasing CO2 enrichment of the atmosphere. Abstract Copyright (2012) Elsevier, B.V.
13081432 Smolyanitskiy, L. A. (Moscow State University of Transportation, Voronezh Division, Voronezh, Russian Federation). Kapillyarnoye uvlazhneniye gruntov zemlyanykh sooruzheniy [Capillary moistening of earthwork soils]: Vestnik Voronezskogo Gosudarstvennogo Universiteta. Geologiya, 2012(1), p. 229-233, illus., 2 ref., 2012.
The bulk earthen structures of a dam, dam, earthen cloth iron and highways are while in service subject to natural influences to atmospheric precipitation, at high waters, freezing in the winter period. Thus the humidity of a ground changes over a wide range, that results in change of durability and compressibility of a ground, soil heaving at negative temperatures of air. The specified factors cause deformations, and sometimes and loss of stability of structures. In given clause the conditions of humidifying of a ground are considered and the account maximum is offered its possible probable capillary humidifying.
13083614 Zolotarev, Ye. A. (Moscow State University, Department of Geography, Moscow, Russian Federation); Aleynikov, A. A. and Khar'kovets, Ye. G. Degradatsiya oledeneniya i formirovaniye katastroficheskikh seley v sovremennykh lednikovo-morennykh kompleksakh Priel'brus'ya [Glacier degradation and catastrophic mudflows within modern glacial-moraine systems of Elbrus]: Led i Sneg = Ice and Snow, 119, p. 99-108 (English sum.), illus. incl. 2 tables, 23 ref., 2012.
Mechanism of formation of the catastrophic mudflows in different glacial valleys of Elbrus region at the present stage of glacial degradation is described. The important role of the buried ice in the formation of catastrophic mudflows that affected Tyrnyauz in the XX century was revealed as a result of remote monitoring of changes in glacial-moraine complex of Kayarta river. The dynamics of glacial lakes in the Adyl-Su valley in the Bashkara Glacier region was described and probability of their breakthrough was estimated. The quantitative indicators of the dynamics of the landslide in the Kubasanty valley were obtained as a result of remote monitoring, and its influence on the formation of catastrophic mudflows is discovered. Various possible methods of catastrophic mudflows prevention not requiring expensive protective constructions are discussed.
Back to the Top
13077128 Blais-Stevens, Andrée (Geological Survey of Canada, Ottawa, ON, Canada); Kremer, Marian; Bonnaventure, Philip; Lipovsky, Panya; Smith, Sharon and Lewkowicz, Antoni G. Landslide susceptibility mapping in permafrost terrain along the Yukon Alaska highway corridor, southwestern Yukon, Canada [abstr.]: in Geological Society of America, 2012 annual meeting, Abstracts with Programs - Geological Society of America, 44(7), p. 344, November 2012. Meeting: Geological Society of America, 2012 annual meeting, Nov. 4-7, 2012, Charlotte, NC.
Slope stability in the permafrost terrain of northern Canada can greatly influence infrastructure design and performance. Several types of landslides and ground hazard features were identified for a proposed pipeline route along Yukon Alaska Highway Corridor (YAHC=950 km ´ 40 km). Some were directly related to permafrost conditions, such as, active layer detachment slides, retrogressive thaw flows, solifluction, thermo-karstic depressions, and rock glaciers. Landslide inventory and preliminary susceptibility maps of debris flows, rockfalls/rock slides, active layer detachment slides, and retrogressive thaw flows were produced. The inventory identified a total of 1743 landslides, or 1 landslide per 17 km2. These were debris slides (31%), debris flows (28%), rock slides (11%), rockfalls (4%), solifluction (8%), earth slides/flows (5%), thermo-karstic depressions, retrogressive thaw flows and active layer detachments (1%) and rock glaciers (6%). Landslide susceptibility modeling was based on a qualitative heuristic approach, which was split into four different mapping exercises reflecting the different parameters that trigger these landslides. Validation of the debris flow susceptibility map indicates that 69% of the debris flow deposits occur downstream from a high susceptibility zone and 28% from moderate zone. The rockfall/rock slide susceptibility map indicated that 64% of failures occur in high susceptibility zones and 20% in moderate zones. Thus, there is a good correlation between the landslide susceptibility maps and landslide inventory. Validation of active layer detachment slide and retrogressive thaw flow susceptibility maps was more difficult as these types of landslides are considered temporary because they disappear from the geological record in a short period of time. These are usually small and are re-vegetated rapidly, which makes them less easily identifiable on air-photos. Nonetheless, there is good correlation with the available inventory and the susceptibility maps.
13083554 Lewis, Gabriel (Williams College, Department of Geosciences, Williamstown, MA); Leopold, Matthias and Dethier, David P. Using geophysical techniques in the critical zone to determine the presence of permafrost [abstr.]: in Geological Society of America, 2012 annual meeting, Abstracts with Programs - Geological Society of America, 44(7), p. 460, November 2012. Meeting: Geological Society of America, 2012 annual meeting, Nov. 4-7, 2012, Charlotte, NC.
Electric Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR) are geophysical techniques utilized worldwide to study the evolution of alpine permafrost and ice lenses. Combining these techniques maximizes the accuracy of each method while reducing their inherent ambiguities and limitations. The alpine Green Lakes and 4th of July Valleys within the Colorado Front Range offer ideal locations to verify the existence of ice masses within rock glaciers, where they are predicted by many models. On nearby Niwot Ridge, geomorphological, hydrological, and GIS techniques have been used to calculate probabilities of permafrost at depth, but predictions have not previously been verified in the field. Permafrost and ice lenses beneath active solifluction lobes were also documented in several studies during the 1970's along Niwot Ridge. This study examines: (1) the results of 15 ERT lines totaling 765 meters within the Critical Zone, sited to test permafrost predictions in alpine zones; (2) soil temperature profiles and morphology in several pits excavated to saprolite along ERT lines; and (3) measurements of the 4th of July Rock Glacier's retreat during the past century including its implications for nearby permafrost. Analysis of seven ERT lines from elevations of 3500 to 3900 meters on Niwot Ridge demonstrates that these locations lack permanent ice lenses (resistivity of approximately 200-1000 kWm) beneath a surface layer of coarse, blocky debris (resistivity of ~ 20 kWm). Solifluction lobes, as well as nearby snow field areas may retain semi-permanent ice lenses that were considered permafrost features, but ice often melts out completely by late summer. The rock glaciers have experienced decades of retreat due to high-elevation warming and decreases in moisture supply (i.e. droughts during the winters of 2002-2003 and 2011-2012), resulting in partial melting of subsurface ice and deposition of a layer of rocks previously supported by ice. Better understanding of the present distribution of permafrost and active periglacial features may help predict changes to alpine landscapes as permafrost disappears as well as implications for the quantity of runoff from these areas in the future.
13081646 Soare, R. J. (Dawson College, Department of Geography, Montreal, QC, Canada); Conway, Susan J.; Pearce, Geoffrey D.; Dohm, J. M. and Grindrod, P. M. Possible crater-based pingos, paleolakes and periglacial landscapes at the high latitudes of Utopia Planitia, Mars: in Mars polar science V (Moersch, Jeffrey, editor; et al.), Icarus, 225(2), p. 971-981, illus. incl. 2 tables, sketch maps, 48 ref., August 2013. Meeting: Fifth international conference on Mars polar science and exploration, Sept. 12-16, 2011, Fairbanks, AK.
Closed-system pingos (CSPs) are perennial ice-cored mounds that evolve in relatively deep and continuous permafrost. They occur where thermokarst lakes either have lost or are losing their water by drainage or evaporation and by means of freeze-thaw cycling, permafrost aggradation and pore-water migration. The presence of CSPs on Mars, particularly on late-Amazonian Epoch terrain at near-polar latitudes, would indicate: (1) the antecedent occurrence of ponded water at the mound-formation sites; (2) freeze-thaw cycling of this water; and (3) boundary-conditions of pressure and temperature at or above the triple point of water much more recently and further to the north than has been thought possible. In 2005 we studied two crater-floor landscapes in northern Utopia Planitia and used MOC narrow-angle images to describe mounds within these landscapes that shared a suite of geological characteristics with CSPs on Earth. Here, we show the results of a circum-global search for similar crater-floor landscapes at latitudes >~55°N. The search incorporates all relevant MOC and HiRISE images released since 2005. In addition to the two periglacially suggestive crater-floor landscapes observed by us earlier, we have identified three other crater floors with similar landscapes. Interestingly, each of the five mound-bearing craters occur within a tight latitudinal-band (~64-69°N); this could be a marker of periglacial landscape-modification on a regional scale. Just to the north of the crater-based pingo-like mounds Conway et al. have identified large (km-scale) crater-based perennial ice-domes. They propose that the ice domes develop when regional polar-winds transport and precipitate icy material onto the floor of their host craters. Under a slightly different obliquity-solution ice domes could have accumulated at the lower latitudes where the putative CSPs have been observed. Subsequently, were temperatures to have migrated close to or at 0 °C the ice domes could have thawed, forming endogenic paleolakes. This region also contains a significant concentration of crater-floor polygons. The polygons are thought to have formed by desiccation (El Maarry et al. . J. Geophys. Res., 115 (E10006)) or thermal contraction (Soare et al. [2005a]. Icarus, 174 (373-382)); on Earth each of these processes is associated with the end-stage of lake evolution. On the basis of our enhanced image collection, a new map displaying the global distribution of mound-bearing craters and a two new digital-elevation models of a crater-floor with pingo-like mounds, we evaluate the CSP hypothesis anew. We also explore two alternative hypotheses: (1) the mounds are weathered central-uplift complexes; or (2) they are impact-related hydrothermal structures. However, we propose that the CSP hypothesis is much more robust than these alternatives, encompassing geomorphological, cartographical, stratigraphical and climatological observations, and less subject to inconsistencies.
13083900 Karlstrom, Eric T. (California State University Stanislaus, Geography, Turlock, CA). Magnitude of Quaternary temperature fluctuations inferred from relict paleosols and periglacial features, Waterton-Glacier Park area, Montana and Alberta [abstr.]: in Geological Society of America, Rocky Mountain Section, 65th annual meeting, Abstracts with Programs - Geological Society of America, 45(5), p. 39, April 2013. Meeting: Geological Society of America, Rocky Mountain Section, 65th annual meeting, May 15-17, 2013, Gunnison, CO.
Because particular kinds of soils and periglacial features form under particular climatic regimes, magnitude of past climate change may be estimated in areas where relict paleosols and periglacial features are not in equilibrium with the present climate. Relict (interglacial) paleosols in Quaternary sediments near Waterton-Glacier National Parks most resemble fersiallitic soils (Paleudalfs, Palustalfs, and Paleudolls) of the Southeastern U.S., where mean annual temperatures (MATs) are at least 6 to 8°C warmer and mean average precipitation (MAP) is at least 40 cm greater than those of the Waterton-Glacier Parks area today (MAT is ~4.2°C and MAP is ~50 cm). Relict periglacial features in this region, including ice-wedge casts, record much colder glacial conditions. Because ice-wedges form in continuous permafrost where MATs are -6°C or colder, occurrence of ice-wedge casts here suggests MATs were at least 10°C colder than present during glacial maxima. These data suggest: 1) MATs in this very continental region fluctuated from ~10-12°C or warmer during interglacial maxima to about -6°C or colder during glacial maxima, and 2) "equivalent latitude" shifted at least 8 to 11° southward during interglacial maxima and ~16° northward during glacial maxima. Distribution of Quaternary plant and animal fossils in mid-continental North America and Eurasia records similar and even greater fluctuations of average annual temperatures (at least 16-18°C or 29-32°F).
13076806 Schoderbek, David (ConocoPhillips, Anchorage, AK); Klein, Jim and Howard, James. Comparative formation evaluation methodologies for gas hydrate evaluation in Ignik Sikumi #1, Alaska North Slope [abstr.]: in 2012 AAPG annual convention & exhibition; abstracts volume; Directing the future of E&P; starring creative ideas and new technology, Abstracts: Annual Meeting - American Association of Petroleum Geologists, 2012, unpaginated, 2012. Meeting: 2012 AAPG annual convention & exhibition, April 22-25, 2012, Long Beach, CA.
Ignik Sikumi #1 was drilled in early 2011 on the Alaska North Slope for evaluation of CO2/CH4 exchange technology in methane-hydrate bearing sands. Hydrate saturation and water saturation are critical to exchange: excess water may react with injected CO2 to form CO2-hydrate, which may diminish reservoir permeability. Quantification and characterization of pore water is a primary focus of this petrophysical evaluation. High-porosity sandstones of the Tertiary Sagavanirktok Formation host North Slope gas hydrate deposits. Water-bearing sandstones are also present in Ignik Sikumi #1, well above the calculated base of the hydrate stability. Ignik Sikumi #1 was drilled vertically through permafrost to 1750 feet (MD), below which hydrate-bearing sediments were penetrated with chilled, oil-based mud. Openhole log suite includes gamma-ray, neutron porosity, high-resolution bulk density, compressional and shear sonic scanner, resistivity scanner, micro-resistivity imaging, and magnetic resonance tools. The interplay of different responses from different tools optimizes detection and quantitative evaluation of hydrate-bearing reservoirs. One method for evaluation of the gas-hydrate sands is a combination of density and magnetic resonance. Combining magnetic resonance with bulk density measurements allows determination of hydrate saturation without inference of connate water resistivity, one shortcoming of the Archie Equation. Sagavanirktok "Upper C" sandstone has average hydrate saturation of 75% and water saturation of 25%. The Archie Equation also successfully determined saturations, using density porosity calculated with fluid density equal to that of hydrates and Rw from nearby wet sands. A third, partially successful method was simultaneous solution using gamma-ray, neutron porosity, compressional transit time, and bulk density, to solve for hydrate volume. A fourth method utilizing compressional and shear wave velocities consistently underestimated hydrate saturation compared to the other methods. High-resolution density porosity and micro-resistivity were combined via the Archie Equation as a fifth water saturation calculation technique. Characterization of pore water as clay-bound, capillary-bound and free water is possible with magnetic resonance log measurements. Evaluation of relaxation time distributions and optimization of cutoff times indicates that of the water present in the pores (SWavg = 25%), 41% is mobile or "free" water.
URL: http://www.searchanddiscovery.com/abstracts/html/2012/90142ace/abstracts/scho.ht ...
13081630 Battler, Melissa M. (University of Western Ontario, Department of Earth Sciences, London, ON, Canada); Osinski, Gordon R. and Banerjee, Neil R. Mineralogy of saline perennial cold springs on Axel Heiberg Island, Nunavut, Canada and implications for spring deposits on Mars: in Terrestrial analogs for Mars; Mars Science Laboratory and beyond (Moersch, Jeffrey, editor; et al.), Icarus, 224(2), p. 364-381, illus. incl. 5 tables, sketch maps, 61 ref., June 2013. Meeting: Mars analogues workshop, March 5-6, 2011, The Woodlands, TX.
13081631 Battler, Melissa M. (University of Western Ontario, Department of Earth Sciences, London, ON, Canada); Osinski, Gordon R.; Lim, Darlene S. S.; Davila, Alfonso F.; Michel, Frederick A.; Craig, Michael A.; Izawa, Matthew R. M.; Leoni, Lisa; Slater, Gregory F.; Fairén, Alberto G.; Preston, Louisa J. and Banerjee, Neil R. Characterization of the acidic cold seep emplaced jarositic Golden Deposit, NWT, Canada, as an analogue for jarosite deposition on Mars: in Terrestrial analogs for Mars; Mars Science Laboratory and beyond (Moersch, Jeffrey, editor; et al.), Icarus, 224(2), p. 382-398, illus. incl. 4 tables, 74 ref., June 2013. Meeting: Mars analogues workshop, March 5-6, 2011, The Woodlands, TX.
13083522 Curry, B. Brandon (Illinois State Geological Survey, Prairie Research Institute, Champaign, IL) and Hajic, Edwin R. Large meltwater events associated with the Lake Michigan Lobe during the last deglaciation, Illinois, USA [abstr.]: in Geological Society of America, 2012 annual meeting, Abstracts with Programs - Geological Society of America, 44(7), p. 454, November 2012. Meeting: Geological Society of America, 2012 annual meeting, Nov. 4-7, 2012, Charlotte, NC.
Evidence of large discharge events in Illinois include lemniscate loops and moraine-breaching channels. The deglacial chronology of the Lake Michigan lobe indicates two temporal windows when meltwater was prevalent. The oldest window is 22.0 to 18.5 cal ka, and the floods associated with this period are known as the Kankakee Torrents. The second window is associated with erosion of the Chicago Outlet at about 14.7 cal ka. The period previous to the first window includes an advance phase of the Lake Michigan lobe beginning at 25.6 cal ka, culminating at the glacial maximum at 23.0 cal ka, and retreat north of Illinois by 22.0 cal ka. The radiocarbon chronology of fossils archived in two ice-walled lakes in northeastern Illinois indicate that the first temporal window was marked by extremely cold periglacial conditions that limited or halted summer melting of the active layer. An ice-walled lake plain near Woodstock, IL, (42.26°N, -88.41°W) has yielded 7 AMS ages that include two clusters, one from 21.9-21.5 cal ka, and the other 18.7-17.8 cal ka. The paucity of ages from about 22.0-18.5 cal ka is replicated at one additional site near Hampshire, IL, and also occurs spatially in bottom dates of ice-walled lake deposits throughout Illinois. Interestingly, the breaching of the Marseilles Moraine near Oswego, IL, occurred near the end of the temporal window at 18.82 cal ka. The combined evidence suggests that subglacial meltwater was stored during the early part of the temporal window as the toe of the Lake Michigan lobe froze year-round. Meltwater was released, perhaps catastrophically, during the later stages of the temporal window. We agree with early workers who indicated that meltwater contributions included those from the Lake Michigan, Huron-Erie, and Saginaw lobes. New radiocarbon ages from slackwater lake sediment deposited within the main trunk of the Illinois River valley near Havana, IL (40.34°N, -90.10°W) indicate at least two valley lake phases based on 12 AMS ages. The oldest phase dates from 18.05-17.57 cal ka, and the younger phase, 14.50-13.20 cal ka. Both lake phases were preceded by channelized scour events. There is little doubt the younger event is related to erosion of the Valparaiso Moraine via the Chicago Outlet. The older channel fill is consistent with late-stage discharge of the Kankakee Torrents.
13081637 Hansen, Gary B. (University of Washington, Department of Earth and Space Science, Seattle, WA). An examination of Mars' north seasonal polar cap using MGS; composition and infrared radiation balance: in Mars polar science V (Moersch, Jeffrey, editor; et al.), Icarus, 225(2), p. 869-880, illus. incl. sketch map, 50 ref., August 2013. Meeting: Fifth international conference on Mars polar science and exploration, Sept. 12-16, 2011, Fairbanks, AK.
A detailed analysis of data from one revolution of the Mars Global Surveyor (MGS) is presented. Approximately 80% of this revolution observes the mid-winter northern seasonal polar cap, which covers the surface to <60°N, and which is predominantly within polar night. The surface composition and temperature are determined through analysis of 6-50 mm infrared spectra from the Thermal Emission Spectrometer (TES). The infrared radiative balance, which is the entire heat balance in the polar night except for small subsurface and atmospheric advection terms, is calculated for the surface and atmospheric column. The primary constituent, CO2 ice, also dominates the infrared spectral properties by variations in its grain size and by admixtures of dust and water ice, which cause large variations in the 20-50 mm emissivity. This is modified by incomplete areal coverage, and clouds or hazes. This quantitative analysis reveals CO2 grain radii ranging from ~100 mm in isolated areas, to 1-5 mm in more widespread regions. The water ice content varies from none to about one part per thousand by mass, with a clear increase towards the periphery of the polar cap. The dust content is typically a few parts per thousand by mass, but is as much as an order of magnitude less abundant in "cold spot" regions, where the low emissivity of pure CO2 ice is revealed. This is the first quantitative analysis of thermal spectra of the seasonal polar cap and the first to estimate water ice content. Our models show that the cold spots represent cleaner, dust-free ice rather than finer grained ice than the background. Our guess is that the dust in cold spots is hidden in the center of the CO2 frost particles rather than not present. The fringes of the cap have more dust and water ice, and become patchy, with warmer water snow filling the gaps on the night side, and warmer bare soil on the day side. A low optical depth (<1 in the visible) water ice atmospheric haze is apparent on the night side, and appears with smaller optical depth on the day side. The infrared radiative balance at the surface is typically 20-25 W m-2 in the central polar cap, with ~25% dips in the regions of dust-free CO2. The atmospheric radiative terms are typically 1-3 W m-2.
13081645 Korteniemi, J. (University of California at Santa Cruz, Department of Earth and Planetary Sciences, Santa Cruz, CA) and Kreslavsky, M. A. Patterned ground in Martian high northern latitudes; morphology and age constraints: in Mars polar science V (Moersch, Jeffrey, editor; et al.), Icarus, 225(2), p. 960-970, illus. incl. 1 table, sketch map, 62 ref., August 2013. Meeting: Fifth international conference on Mars polar science and exploration, Sept. 12-16, 2011, Fairbanks, AK.
We performed a systematic survey of typical surface patterns and small (5-50 m) impact craters in a zone between 50° and 70° latitude in the Northern Lowlands of Mars. We found that small-scale (<10 m) polygonal pattern formed by narrow fractures is typical in the northern half of the studied zone. We interpret this pattern to be formed by active thermal contraction polygons associated with the present-day shallow ground ice. These fresh small polygons are superposed over a larger-scale (~15-30 m) polygonal network of smooth gentle troughs and mounds. The latter pattern extends southward from the shallow ground ice boundary to the southern edge of the study zone. We interpret this pattern to be a relic from different climate conditions in the geologically recent past (possibly, to the most recent periods of high obliquity of Mars spin axis). The population of small craters is sparse and indicates intensive resurfacing in the recent geological past. The retention age of 5-10 m diameter craters in the northern part of our study zone is surprisingly young, on the order of hundreds to thousands of years, which means that quick obliteration of such craters occurs under the present-day spin/orbit configuration of Mars. The crater obliteration time scale increases for larger craters and toward the southern edge of the study area.
13081648 Orloff, T. C. (University of California at Santa Cruz, Department of Earth and Planetary Sciences, Santa Cruz, CA); Kreslavsky, M. A. and Asphaug, E. I. Possible mechanism of boulder clustering on Mars: in Mars polar science V (Moersch, Jeffrey, editor; et al.), Icarus, 225(2), p. 992-999, illus., 42 ref., August 2013. Meeting: Fifth international conference on Mars polar science and exploration, Sept. 12-16, 2011, Fairbanks, AK.
Whatever causes small-scale polygonal patterned ground (diameter < ~20 m) to form pervasively in the northern plains of Mars, appears to also cause boulders to cluster at polygon margins. Assuming that these polygons are caused by the seasonal thermal contraction and expansion of ice in the near-surface to meters of depth, we propose a mechanism that ratchets boulders towards the edges in seasonal cycles on present day Mars. During the contraction (cooling) phase, a CO2 frost layer embeds the boulders. Buffered by condensation and sublimation, the solid CO2 is isothermal and does not contract; we propose that it locks the boulders in place while the H2O ice in the near surface continues cooling and contracts beneath them. In spring/summer seasons when the frost sublimates and heating of the surface begins, the boulders freely move with the expanding near surface ice. We show that over many seasons this process would lead to progressive boulder movement towards polygon edges, with an estimated rate of boulder migration ~0.1 mm/yr under present Mars conditions.
13081642 Stroble, Shannon T. (Tufts University, Department of Chemistry, Medford, MA); McElhoney, Kyle M. and Kounaves, Samuel P. Comparison of the Phoenix Mars Lander WCL soil analyses with Antarctic dry valley soils, Mars meteorite EETA 79001 sawdust, and a Mars simulant: in Mars polar science V (Moersch, Jeffrey, editor; et al.), Icarus, 225(2), p. 933-939, illus. incl. 5 tables, 24 ref., August 2013. Meeting: Fifth international conference on Mars polar science and exploration, Sept. 12-16, 2011, Fairbanks, AK.
The results of the Mars Phoenix Lander's Wet Chemistry Laboratory (WCL) for the analyses of the soluble ionic species present in the soil at the northern polar plains of Mars are compared to soil from the Antarctic Dry Valleys (ADVs), martian meteorite EETA79001 sawdust, and a Mars simulant. The ADV soil was compared to the Phoenix site by averaging the samples at analogous 0-5 cm depths and also all the samples from the pavement to the ice-table. Results from each analysis reveal similar ion concentrations ranging plus or minus one order-of-magnitude for all ions except perchlorate (ClO-4), which was three orders-of-magnitude greater in the Phoenix soil. The pH and solution electrical conductivity were also found to be similar for the ADV and Mars soils. The ADV profiles confirm that ClO4- gradients are sensitive indicators for the presence and form of liquid H2O on both Earth and Mars. The Phoenix and meteorite samples contained similar species and ratios but the meteorite concentrations were on average ~4% of those for the Phoenix soil. The only exception was the ~16% higher level of Ca2+ in the meteorite due to the CaCO3 druse. The ADV results imply that the Phoenix site is significantly more arid than University Valley, and has been for a greater period of time, as evidenced by the lack of salt gradients and the age of the soils. A Mars simulant was also formulated according to a MINEQL equilibrium model of the WCL results, and its analysis provides confidence that the soluble composition and parent salts at the Phoenix site are reasonably constrained. Overall, comparison of these samples of soil and sawdust indicates that not only does the martian meteorite EETA79001 contain similar soluble ionic species as the martian soil from the northern polar plains, but also that the soils from the ADV are similar to both, thus strengthening the argument for the ADV as a suitable terrestrial Mars analog environment.
13083797 Aanes, Colin George (Fort Lewis College, Durango, CO); Dott, Cynthia E. and Gianniny, Gary L. Limited riparian aquifer recharge due to drought and dam management along the Dolores River, Colorado [abstr.]: in Geological Society of America, Rocky Mountain Section, 65th annual meeting, Abstracts with Programs - Geological Society of America, 45(5), p. 1, May 2013. Meeting: Geological Society of America, Rocky Mountain Section, 65th annual meeting, May 15-17, 2013, Gunnison, CO.
Here we document the combined impact of record low snowmelt runoff, small dam releases, and weak monsoons of the 2012 water-year on riparian aquifers along the Dolores River in SW Colorado. Flows (approximately 2600 Cubic Feet per Second (CFS)) are typically released from McPhee Reservoir into the Dolores River to simulate snow melt high flows. During 2012, flows of 35 to 70 CFS were released due to the low snowpack in alpine regions. In this study, transects of piezometers were set up in 2010, at three study sites along the Dolores River; Upper Dolores Wildlife Area, Lone Dome Wildlife Area, and Big Gypsum Valley. Tipping rain gage stations were added in 2011, and in 2012 the installation of low cost stream gages provided onsite stream flow data. 2012 piezometer data show a significant decrease in groundwater levels compared to 2010-2011, due to low stream flows and evapotranspiration. Because of exceptionally low dam releases, and record high temperatures, piezometers located shoreward in the point bar system went dry by early June of 2012 for the first time in three years, showing no sign of recharge through the monsoon season regardless of duration or magnitude of rainfall events. Soil moisture probes located at 10 cm and 50 cm below the ground surface show water absorption into soil during longer duration precipitation events at 10 cm, but not 50 cm. This is attributed to low hydraulic conductivity and evapotranspiration. Throughout 2012 and this entire study, piezometer data show stream flow and associated bank recharge as the dominant influence of riparian aquifer recharge. This is highlighted by the fact that piezometers farther than 15m from the stream showed no response from monsoon rain events in 2012, regardless of their duration or magnitude. If the drought of 2012 is an indicator of future climate variability, the health of riparian ecosystems which rely on ground water, will require careful water management.
13083823 Cox, K.D. (Fort Lewis College, Department of Geosciences, Durango, CO); Kean, Jason W.; Coe, Jeffrey A.; Smith, Joel B.; McCoy, Scott W. and Kenny, Ray. Controls on rockfall production; Chalk Cliffs, Buena Vista, CO [abstr.]: in Geological Society of America, Rocky Mountain Section, 65th annual meeting, Abstracts with Programs - Geological Society of America, 45(5), p. 5-6, May 2013. Meeting: Geological Society of America, Rocky Mountain Section, 65th annual meeting, May 15-17, 2013, Gunnison, CO.
Chalk Cliffs, located 13 km southwest of Buena Vista, Colorado, are highly weathered, sparsely vegetated cliffs of quartz monzonite. Rockfall from the cliffs accumulates in channels below and provides material for frequent debris flows (~3 per year). The purpose of this study was to quantify the rates and controls on rockfall as part of a broader effort to understand debris-flow processes at Chalk Cliffs. Rockfall sediment accumulation and accompanying meteorological conditions were continuously monitored from November, 2011 to May, 2012. Data include measurements of: 1) air temperature; 2) rock temperature on a south-facing bedrock slope at 9 depths between 0 and 42 cm; 3) water volume from snow melt and rainfall; 4) wind speed; and 5) rockfall accumulation behind a 246-cm wide by 40-cm high fence. Daily rockfall volumes are estimated by digitizing photographs (3 per day) of the rockfall deposits retained by the fence. These daily estimates of rockfall volume are constrained by more precise volume measurements made at three-month intervals by stereo photogrammetry and by weighing all the accumulated sediment (D50 = 2 cm). Over the course of the monitoring period 330 kg (0.12 m3) of sediment accumulated behind the fence. This volume of sediment corresponds to an average of 5 mm of surface erosion in the 22 m2 source area. Temperature measurements show that the mean air temperature during this time was slightly above freezing (1.5 degree C), and that only the top 5 cm of the rock frequently spent time in the frost-cracking window (-3 to -10 degree C). Daily observations of rockfall show that the sediment came in pulses coinciding primarily with times when moisture was available from melting snow and the near-surface rock temperature was in the frost-cracking window. Smaller finer-grained pulses of sediment were also added during days with high winds (gusts > ~10 m/s). It is hoped that continued monitoring will help constrain a rockfall generation model for the site, which can, in turn, be used to investigate the long-term interplay between sediment supply from rockfall and sediment export by debris flows at Chalk Cliffs.
13083484 DiPietro, Lyndsay (Baylor University, Department of Geology, Waco, TX); Driese, Steven G.; Stinchcomb, Gary E.; Graf, K. E.; Goebel, T.; Younie, A. M. and Gillispie, T. E. First Americans archaeology and climate; soil chemistry and its applications for geoarchaeology in central Alaska [abstr.]: in Geological Society of America, 2012 annual meeting, Abstracts with Programs - Geological Society of America, 44(7), p. 304, November 2012. Meeting: Geological Society of America, 2012 annual meeting, Nov. 4-7, 2012, Charlotte, NC.
Understanding the effects of Quaternary climate events in central Alaska is crucial for addressing some of the most pressing research questions in First Americans archaeology. Differences in lithic technologies throughout the latest Pleistocene and earliest Holocene have been attributed to any one of a number of things, climate change included, but few conclusive, site-specific climate data are currently in use. Much of the work conducted in this area pre-dates modern geochemical techniques and, as a result, climate reconstructions are generally based on sedimentology and regional-or-larger-scale pollen analysis. Recent advances in paleopedology and sedimentary geochemistry now allow for a much more comprehensive and local-scale understanding of climate. This study employs such data at three central Alaskan archaeological sites: Owl Ridge, Dry Creek, and Linda's Point. Soil micromorphology was employed to identify paleosol horizons within the stratigraphic sequences at each site. Soil magnetic susceptibility, d13C of soil organic matter (SOM) and whole soil chemistry were then used to assess changes in paleoprecipitation, paleotemperature and vegetation at each site in an attempt to correlate technology changes at these sites with major climatic shifts. This study serves a twofold purpose: to gather climate data relevant to the archaeology of the peopling of the Americas and to test a loess-calibrated variant of the CALMAG paleoprecipitation proxy newly developed using the Baylor University Paleosol Informatics Cloud (BU-PIC) database. The CALMAG proxy estimates paleoprecipitation (MAP) by using (Al2O3)/ (Al2O3+CaO+MgO) in a paleosol. ICP-MS and ICP-AES elemental weight percentages were calculated for buried B horizons at each site. Data suggest that paleoprecipitation ranged from 570-730 mm/yr at Owl Ridge and 822-1193 mm/yr at Dry Creek. On average, these values are higher than modern precipitation at these sites (~400 mm/yr) and suggest a wetter climate during the latest Pleistocene and early Holocene than exists today. d13C values of SOM at Owl Ridge indicate dominance of C3 vegetation in the late Holocene but with possible inputs of C4 plants during drier periods in the mid- to early Holocene and latest Pleistocene.
13081140 Hyland, Ethan (University of Michigan, Department of Earth and Environmental Sciences, Ann Arbor, MI); Zalmout, Iyad S.; Gingerich, Philip D.; Alsobhi, Saleh A.; Al-Masari, Abdo M.; Nadrah, Ayman O. and Sheldon, Nathan D. Oligocene characteristics of Afro-Arabian habitats; new evidence from paleosols of the Shumaysi Formation, western Saudi Arabia [abstr.]: in Geological Society of America, 2012 annual meeting, Abstracts with Programs - Geological Society of America, 44(7), p. 415, November 2012. Meeting: Geological Society of America, 2012 annual meeting, Nov. 4-7, 2012, Charlotte, NC.
Recent investigation of terrestrial sediments from the upper part of the Shumaysi Formation, exposed along the Red Sea coast at Harrat Al Ujayfa, western Saudi Arabia, led to the discovery of new vertebrate fossil localities. These localities have yielded a terrestrial mammalian fauna which includes hyraxes, embrithopods, proboscideans, artiodactyls, and primates. Primate Saadanius hijazensis is of particular interest because it is an advanced stem catarrhine that shares a tubular ectotympanic with crown catarrhines, and therefore is likely close to the common ancestry of Old World monkeys, apes, and humans. Despite the significant body of research on the stratigraphy of Afro-Arabian Paleogene sites, little work has been done to characterize the environmental contexts of the Arabian subcontinent during the Oligocene. New work has been undertaken in the magnetostratigraphy, paleopedology, geochemistry, and phytolith biostratigraphy of the Harrat Al Ujayfa (the type locality of Saadanius hijazensis), where the Shumaysi Formation exposes a 73-meter section of fluvially deposited siltstones and sandstones with significant evidence of pedogenesis. High-resolution magnetostratigraphic sampling through the formation indicates that the section was deposited during the latest early or early late Oligocene (latest Rupelian to early Chattian, roughly 30-25 Ma). Field identification of paleosols indicate a suite that includes primarily Alfisols and Ultisols, most of which exhibit significant redoximorphic features and Bt horizons. Together these indicate a floodplain paleoenvironment with significant soil development, consistent with humid, forested conditions. Trends from carbon isotope stratigraphy showing lighter d13C values, whole rock geochemical results indicating moderate mean annual temperatures and higher precipitation, and phytolith assemblage compositions that record primarily forest habitats all indicate environmental continuity and the extension of these habitats across Afro-Arabia during this time period. The upper Shumaysi Formation accommodated the widespread expansion of ecosystems that dominated a large landmass during a time when Africa and Arabia were contiguous, with forest habitats similar to those recorded in the earliest Oligocene in Egypt and Oman.
13081138 Murphy, Laura R. (Kansas Geological Survey, Lawrence, KS); Hurst, Stance C.; Holliday, Vance T.; Johnson, Eileen; Sanderson, Bridget and Winsborough, Barbara. The late Quaternary plant communities of the Caprock Canyonlands ecotone; multiple proxy paleoenvironmental data from two draws on the eastern escarpment of the Southern High Plains of Texas, USA [abstr.]: in Geological Society of America, 2012 annual meeting, Abstracts with Programs - Geological Society of America, 44(7), p. 415, November 2012. Meeting: Geological Society of America, 2012 annual meeting, Nov. 4-7, 2012, Charlotte, NC.
The Caprock Canyonlands are an ecotone and physiographic boundary in northwest Texas, USA, between the Southern High Plains to the west and the Central Lowlands to the east. The canyonlands are defined by the steep Ogallala caprock escarpment, remnant mesas, and alluvial outwashes, and have undergone significant periods of erosion during the late Quaternary. In stark contrast to the flat, featureless Southern High Plains surface, the canyonlands contain abundant springs, lithic resources, shelter, and plant and animal food sources that attracted hunter-gatherer groups. New pedologic, lithologic, and multiple proxy paleoenvironmental data are presented from the upper reaches of two draws on the edge of the caprock escarpment: Spring Creek and Middle Creek. Grain-size, stable carbon isotope, and microbotanical data, as well as radiocarbon ages determined on soil organic matter, are presented. Both the upper reaches of Middle and Spring Creeks contain a late Pleistocene through middle Holocene soil and sediment record that has otherwise been removed downstream. At Middle Creek, buried soils in lacustrine and colluvial deposits ranging from ~11,000-2800 14C yr B.P. (uncalibrated) contain well-preserved phytolith and diatom assemblages. Microbotanical analyses and stable carbon isotope values of soil organic matter suggest a cool/moist environment at the Pleistocene-Holocene transition, followed by a slight increase in aridity with seasonal wetting and drying of a marsh or shallow lake. The most abundant diatom species, Diadesmis gallica, likely thrived under a thick moss covering near the edge of a shallow lake under a cooler climate than today. At Spring Creek, a series of laterally-inset fills span ~22,000-3000 14C yr B.P. (uncalibrated). Stable carbon isotope results from upper Spring Creek indicate that the C4 photosynthetic pathway emerged during the Last Glacial Maximum, potentially under low atmospheric pCO2, but a C3 and mixed plant community persisted in Holocene microenvironments from seasonal moisture availability. The results of the high-resolution paleoenvironmental data set from soils and sediments are providing additional context for the geomorphic and archaeological record that will be compared to adjacent regions.
13083477 Nordt, Lee C. (Baylor University, Department of Geology, Waco, TX); Waters, Michael R.; Forman, Steven L.; Bousman, C. Britt and Driese, Steven G. Abrupt eco-climate transitions during pre-Clovis occupation in the South-Central U.S. [abstr.]: in Geological Society of America, 2012 annual meeting, Abstracts with Programs - Geological Society of America, 44(7), p. 302-303, November 2012. Meeting: Geological Society of America, 2012 annual meeting, Nov. 4-7, 2012, Charlotte, NC.
Discovery of the Debra Friedken pre-Clovis site along Buttermilk Creek in central Texas has led to renewed interest in eco-climate environments during the late Pleistocene. For the 20 ka to 10 ka interval we compiled terrestrial records for the south-central U.S. from bog pollen, stable C isotopes of buried soils, speleothems, nobCCle gases of groundwater, and time slices of temperature and rainfall from general circulation models. We coupled these terrestrial data with marine isotopic records from the Gulf of Mexico (GOM) to reconstruct an evolving eco-climate record of the region. The warming trend that followed the last glacial maximum began ~17 ka and was accompanied by a mosaic of spreading C4 grasslands and woodlands. The largest and most significant meltwater pulse entered the GOM between ~15.5 and 13.0 ka (mwp-1a), apparently in response to Bolling-Allerod warming in high latitudes. This event reversed the deglacial warming trend in the region as rainfall decreased and mixed C3/C4 grasslands emerged at the expense of woodlands. During the Younger Dryas, temperatures increased again as meltwaters in the GOM were redirected to the St. Lawrence Seaway and Arctic Ocean. C4 grasslands and a mosaic of woodlands again emerged. Climate conditions during the terminal Pleistocene in the South-Central U.S. were chaotic and non-analog because of lower sea level, rapidly rising summer insolation, greater seasonality, lower pCO2, and meltwater pulses. It is during the major meltwater pulse in the GOM (mwp-1a), however, that pre-Clovis people occupied Buttermilk Creek in central Texas. Winter rains emanating from a dominance of westerly air flow accompanied by warm and dry summers indicate that occupation occurred in a climate unlike today. The Clovis, and then Folsom people inhabited the region during the rapid Bolling-Allerod to Younger Dryas transition when meltwater was diverting to the North Atlantic forcing higher temperatures, summer monsoonal rainfall, and possibly the mass extinction of megafauna. This investigation shows that more work is needed to better understand the influence of shifting eco-climates on potential settlement patterns and subsistence strategies during the peopling of the Americas.
13083483 Sauer, Daniela (University of Technology, Institute of Geography, Dresden, Germany); Al-Sharif, Riyad; Zwanzig, Lisa; Brückner, Helmut; Scarciglia, Fabio and Stahr, Karl. Buried steppe soils in S Italy; a record of last glacial environments [abstr.]: in Geological Society of America, 2012 annual meeting, Abstracts with Programs - Geological Society of America, 44(7), p. 303-304, November 2012. Meeting: Geological Society of America, 2012 annual meeting, Nov. 4-7, 2012, Charlotte, NC.
We present here a Last Glacial alluvial fan in Calabria (S Italy), exhibiting several alternating sedimentation and soil formation phases. The paleosols represent Chernozem- and Phaeozem-like soils that very likely formed in steppe to forest steppe environments under continental climatic conditions. The same environmental conditions that are reflected in the paleosols have been reconstructed based on pollen records from Lago Grande di Monticchio. The latter indicate temperate deciduous forest from 87.98 to 82.73 ka; vegetation fluctuation from 82.73 to 59.00 ka, then Artemisia steppe; alternation between steppe (stadials) and wooded steppe (interstadials) from 59.00 to 25.90 ka; and again open steppe from 25.90 to 14.30 ka (LGM) (Brauer et al., 2007). Organic matter of the two uppermost Lazzaro paleosols has been 14C-dated to 26.7-28.7 and 28.8-30.3 cal ka BP. Thus, the formation of these soils falls into a period for which the lacustrine record indicates an alternation between steppe and wooded steppe. It is still an open question whether the sedimentation that interrupted the ecologically stable times of soil formation was activated by fluctuations in climate and vegetation cover or by tectonics. The fact that pedogenesis falls into a period of frequent environmental oscillations suggests that the phases of sedimentation are to a certain degree driven by changes in climate and vegetation cover. More data on additional soil-sediment profiles are required to check if paleopedological, lacustrine and marine records can be correlated to obtain an integral reconstruction of paleo-climate, -vegetation, -geomorphodynamics and -pedogenesis in the region. The soils were analyzed for texture, SOC, carbonates, Fed, total elemental composition and micromorphology. Fed values reflect pedogenetic cycles in the alluvial fan more clearly than SOC contents, which are not as high in the paleosols as might be expected according to their dark color. We conclude that Chernozem- and Phaeozem-like soils developed during the Last Glacial period in south Italy in steppe and forest steppe environments. These soils have been preserved only where they had been buried before the climate shifted again to Mediterranean type. Otherwise SOM of the thick mollic A horizons decomposed, and the soils turned into mediterranean-type soils.
13081131 Witter, Robert C. (U. S. Geological Survey, Anchorage, AK); Engelhart, Simon E.; Briggs, Richard W.; Koehler, Rich D. and Gelfenbaum, Guy. Little strain accumulation and release on the Alaska-Aleutian megathrust beneath the Shumagin Islands in the last 3400 years? [abstr.]: in Geological Society of America, 2012 annual meeting, Abstracts with Programs - Geological Society of America, 44(7), p. 413, November 2012. Meeting: Geological Society of America, 2012 annual meeting, Nov. 4-7, 2012, Charlotte, NC.
Russian accounts of a strong earthquake followed by a tsunami in 1788 imply rupture of the Alaska-Aleutian megathrust beneath the Shumagin Islands, Alaska. Geodetic observations in the Shumagin archipelago are consistent with a partially locked plate interface near the trench. Motivated by reports of uplifted marine terraces and features resembling raised shorelines on satellite imagery, we investigated Simeonof Island (120 km northwest of the Aleutian Trench) for evidence of tsunami deposits and relative sea-level (RSL) change related to the earthquake deformation cycle. Field work at 8 sites included descriptions of soil pits, outcrops, and 75 sediment cores along the island's northwest coast. Freshwater peat, 0.5--2-m thick, occurs in thermokarst lake basins and stream valleys in lower elevations. Organic silt and tephra, <2-m thick, uniformly drapes stepped bedrock topography. Topographic profiles, soil pits, and 14C ages from basal silts suggest that the stepped landscape probably has a glacial, rather than marine, origin. A 14C age on basal peat limits glacial retreat to before 9.9 ka. Subsequently, late Holocene RSL rise and/or coastal erosion breached lakes near the coast forming tidal lagoons. At two sites, freshwater peat overlies sand inferred to be marine based on diatoms and d13C values of detrital algae. Interbedded peat-sand contacts suggest lagoons gradually reverted to fresh bogs behind barriers; their elevations and 14C ages imply stable or slowly rising (<0.2 m/ka) RSL since ~3.4 ka. We infer storms rather than tsunamis deposited thin sand layers of limited extent that interrupt peat at elevations below high tide. The absence of raised marine terraces on Simeonof and drowned coasts of neighboring islands suggest that sea-level rise since the mid Holocene has outpaced any net tectonic and/or isostatic uplift. We found no late Holocene evidence on Simeonof for sudden tectonic uplift, subsidence, or tsunami deposits. Therefore, if the megathrust below Simeonof has ruptured since 3.4 ka then vertical displacements were too small or too infrequent to perturb a record of stable or slowly-rising RSL. Our explanation accounts for the apparent lack of geological evidence for the 1788 earthquake and tsunami and implies little cyclic strain accumulation and release on the megathrust below Simeonof Island.
13080894 Kapralova, Veronika (Russian Academy of Sciences, Sergeev Institute of Environmental Geoscience, Russian Federation). Remote sensing and mathematical morphology of landscape application for studying thermokarst processes [abstr.]: in 34th international geological congress; abstracts, International Geological Congress, Abstracts = Congrès Géologique International, Résumés, 34, p. 2515, 2012. compact disc. Meeting: 34th international geological congress, Aug. 5-10, 2012, Brisbane, Queensl., Australia.
In our work we use a method of mathematical morphology of a landscape -- a branch of landscape science, investigating quantitative laws of landscape mosaics and methods of the mathematical analysis of these mosaics. Theoretical basis of mathematical morphology of a landscape is formed by mathematical models of morphological structures -- the quantitative dependences describing basic proper ties of morphological structures. Canonical initial mathematical models play a special role in mathematical morphology of a landscape. They deal with the patterns developed in uniform conditions at constancy of major factors of landscape differentiation and developed under unique process. The equations of the mathematical model of a morphological pattern forthermokarst lake plains were used for the data analysis and forecast constructions. They represent combination of the probabilistic mathematical relations reflecting the most essential geometrical features of the pattern. The researches have also big practical value because with the help of this model it is possible to give the forecast of risks for linear, areal, and point objects.
13079143 Kenzler, Michael (University of Greifswald, Institute of Geography and Geology, Greifswald, Germany); Meng, Stefan and Hüneke, Heiko. The MIS 3 at the cliffs of NW Jasmund (SW Baltic Sea Coast) [abstr.]: in GeoHannover 2012; GeoRohstoffe für das 21. Jahrhundert; Kurzfassungen der Vorträge und Poster (Kümpel, Hans-Joachim, editor; et al.), Schriftenreihe der Deutschen Gesellschaft für Geowissenschaften, 80, p. 317, illus., 3 ref., 2012. Meeting: GeoHannover 2012; GeoRohstoffe für das 21. Jahrhundert, Oct. 1-3, 2012, Hanover, Germany.
13080915 Park, Ji-Hwan (Seoul National University, Department of Energy Systems Engineering, South Korea); Hyun, Chang-Uk and Park, Hyeong-Dong. Detection of pore structure change of rock during freeze-thaw weathering [abstr.]: in 34th international geological congress; abstracts, International Geological Congress, Abstracts = Congrès Géologique International, Résumés, 34, p. 2536, 2012. compact disc. Meeting: 34th international geological congress, Aug. 5-10, 2012, Brisbane, Queensl., Australia.
Freeze-thaw is primary causes of rock weathering in cold regions, and it can cause engineering problems in many fields such as construction of building, railway, pipeline, cultural heritage and so on. When the water inside rock pores or cracks freezes, it expands about 9 percent by volume and acts stress to surrounding rock. Therefore, the repetition of this mechanism will deteriorate the physical proper ties of rock. In this study, the environment around King Sejong Station of Korea, Antarctica was simulated in laboratory for the evaluation of freeze-thaw weathering of the rock. Basalt, diorite and lapilli tuff were used as rock specimens and temperature was varied from -20°C to +10°C, which were major rock types and air temperature of the station. X-ray computed tomography (CT) was used to extract three dimensional structure of rock and identify porosity change, and scanning electron microscope (SEM) was used to detect the change on the rock surface in mineralogical scale. Because micro X-ray CT and SEM have better than 7 m spatial resolution, it can detect the minutest details and extract accurate porosity of the sample. X-ray CT is also appropriate for continuous observation of the same sample, because it is non-destructive method. After implementation of 50 cycles of artificial freeze-thaw weathering, the pore structures were changed and the porosities were increased linearly as weathering progresses for all the specimens. The change of tuff specimens was remarkable compared to that of basalt and diorite specimens, because of its relatively high initial porosity and low tensile strength.
Back to the Top
© American Geosciences Institute