Home About us Contact
|
Home About us Contact | ||
|
|
||
Rock Surface (rock + surface)
Selected AbstractsProduction of oxalates In Vitro by Microbes Isolated from Rock Surfaces with prehistoric paints in the Lower Pecos Region, TexasGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 1 2008Darren Hess Calcium oxalate-rich rock coatings are ubiquitous on limestone inside dry rock shelters and under bluff overhangs along canyon walls in southwestern Texas. Prehistoric pictographs occur in more than 250 such sites, and the ancient paints are encapsulated within the natural rock coating. Previous studies suggest lichens were the source of the oxalate; however, we report here that microbes cultured and isolated from samples of the coating produce oxalate in vitro. Twenty different bacteria species have been identified in samples from eight different sites, with Bacillus the most common genus, represented by five species. HPLC analyses of inoculated R2B medium after eight months of bacterial growth revealed the presence of oxalate ions in the solid phase of the growth medium. © 2008 Wiley Periodicals, Inc. [source] Processes controlling rapid temperature variations on rock surfaces,EARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2010Jamie L. Molaro Abstract In arid environments, thermal oscillations are an important source of rock weathering. Measurements of temperature have been made on the surface of rocks in a desert environment at a sampling interval of 0·375,s, with simultaneous measurements of wind speed, air temperature, and incoming shortwave radiation. Over timescales of hours, the temperature of the rock surface was determined primarily by shortwave radiation and air temperature, while rapid temperature variations, high dT/dt, at intervals of seconds or less, were determined by wind speed. The maximum values of temperature change and time spent above 2°C,min,1 increased at high measurement rates and were much higher than previously reported. The maximum recorded value of dT/dt was 137°C,min,1 and the average percentage time spent above 2°C,min,1 was ,70 ± 13%. Maximum values of dT/dt did not correlate with the maximum values of time spent above 2°C,min,1. Simultaneous measurements of two thermocouples 5·5,cm apart on a single rock surface had similar temperature and dT/dt values, but were not correlated at sampling intervals of less than 10,s. It is suggested that this is resulting from rapid fluctuations due to small spatial and timescale wind effects that are averaged out when data is taken at longer sampling intervals, ,10,s or greater. Published in 2010 by John Wiley & Sons, Ltd. [source] Rock albedo and monitoring of thermal conditions in respect of weathering: some expected and some unexpected resultsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 7 2005Kevin Hall Abstract Broadly speaking, there is, at least within geomorphic circles, a general acceptance that rocks with low albedos will warm both faster and to higher temperatures than rocks with high albedos, reflectivity influencing radiative warming. Upon this foundation are built notions of weathering in respect of the resulting thermal differences, both at the grain scale and at the scale of rock masses. Here, a series of paving bricks painted in 20 per cent reflectivity intervals from black through to white were used to monitor albedo-influenced temperatures at a site in northern Canada in an attempt to test this premise. Temperatures were collected, for five months, for the rock surface and the base of the rock, the blocks being set within a mass of local sediment. Resulting thermal data did indeed show that the dark bricks were warmer than the white but only when their temperatures were equal to or cooler than the air temperature. As brick temperature exceeded that of the air, so the dark and light bricks moved to parity; indeed, the white bricks frequently became warmer than the dark. It is argued that this ,negating' of the albedo influence on heating is a result of the necessity of the bricks, both white and black, to convect heat away to the surrounding cooler air; the darker brick, being hotter, initially convects faster than the white as a product of the temperature difference between the two media. Thus, where the bricks become significantly hotter than the air, they lose energy to that air and so their respective temperatures become closer, the albedo influence being superceded by the requirement to equilibrate with the surrounding air. It is argued that this finding will have importance to our understanding of weathering in general and to our perceptions of weathering differences between different lithologies. Copyright © 2005 John Wiley & Sons, Ltd. [source] Rock thermal data at the grain scale: applicability to granular disintegration in cold environmentsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2003Kevin Hall Abstract Consideration of the mechanisms associated with the granular disintegration of rock has been limited by available data. In most instances, both the size of the transducer and the nature of the study have negated any applicability of the resulting data to the understanding of grain-to-grain separation within rock. The application of microthermocouples (,0·15 mm diameter) and high-frequency logging (20 s intervals) at a taffoni site on southern Alexander Island and from a rock outcrop on Adelaide Island (Antarctica) provide new data pertaining to the thermal conditions, at the grain scale, of the rock surface. The results show that thermal changes (,T/t) can be very high, with values of 22 °C min,1 being recorded. Although available data indicate that there can be differences in frequency and magnitude of ,uctuations as a function of aspect, all aspects experienced some large magnitude (,2 °C min,1) ,uctuations. Further, in many instances, large thermal changes in more than one direction could occur within 1 min or in subsequent minutes. These data suggest that the surface grains experience rapidly changing stress ,elds that may, with time, effect fatigue at the grain boundaries; albedo differences between grains and the resulting thermal variations are thought to exacerbate this. The available data failed to show any indication of water freezing (an exotherm) and thus it is suggested that microgelivation may not play as large a role in granular breakdown as is often postulated for cold regions, and that in this dry, Antarctic region thermal stress may play a signi,cant role. Copyright © 2003 John Wiley & Sons, Ltd. [source] Chemical modification of pyroclastic rock by hot water: an experimental investigation of mass transport at the fluid,solid interfaceGEOFLUIDS (ELECTRONIC), Issue 1 2009J. HARA Abstract Hydrothermal water,(pyroclastic) rock interactions were examined using flow-through experiments to deduce the effect of mass transport phenomena on the reaction process. A series of experiments were conducted over the temperature range 75,250°C, with a constant temperature for each experiment, and at saturated vapour pressure, to estimate the apparent rate constants as a function of temperature. Based on the chemistry of analysed solutions, the water,rock interaction in the experiments was controlled by diffusion from the reaction surface and by the existence of a surface layer at the rock,fluid interface, which regulated the chemical reaction rate. The reaction progress depended to a high degree on flow velocity and temperature conditions, with element abundances in the fluid significantly affected by these factors. Mass transport coefficients for diffusion from the rock surface to the bulk solution have been estimated. Ca is selectively depleted under lower temperature conditions (T < 150°C), whereas Na is greatly depleted under higher temperature conditions (T > 150°C), and K reaction rates are increased when flow velocity increases. Using these conditions, specific alkali and alkali earth cations were selectively leached from mineral surfaces. The ,surface layer' comprised a 0.5,1.8 mm boundary film on the solution side (the thickness of this layer has no dependence on chemical character) and a reaction layer. The reaction layer was composed of a Si, Al-rich cation-leached layer, whose thickness was dependent on temperature, flow velocity and reaction length. The reaction layer varied in thickness from about 10,4 to 10,7 mm under high temperature/low fluid velocity and low temperature/high fluid velocity conditions, respectively. [source] AN EVALUATION OF SURFACE HARDNESS OF NATURAL AND MODIFIED ROCKS USING SCHMIDT HAMMER: STUDY FROM NORTHWESTERN HIMALAYA, INDIAGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 3 2009VIKRAM GUPTA ABSTRACT. Four rock types (quartz mica gneiss, schist, quartzite and calc-silicate) located in the Satluj and Alaknanda valleys were used to test whether a Schmidt hammer can be used to distinguish rock surfaces affected by various natural and man-induced processes like manual smoothing of rock surfaces by grindstone, surface weathering, deep weathering, fluvial polishing and blasting during road construction. Surfaces polished by fluvial process yielded the highest Schmidt hammer rebound (R-) values and the blast-affected surfaces yielded the lowest R-values for the same rock type. Variations in R-value also reflect the degree of weathering of the rock surfaces. It has been further observed that, for all the rock types, the strength of relationship between R-values for the treated surfaces (manual smoothing of rock surface by grindstone) and the unconfined compressive strength (UCS) is higher than for the fresh natural surfaces. [source] ROCK-SURFACE TEMPERATURES OF BASALT IN THE DRAKENSBERG ALPINE ENVIRONMENT, LESOTHOGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 3 2007STEFAN GRAB ABSTRACT. Rock temperature data are presented for a variety of topographic localities at a high Drakensberg site. The objective is to investigate the spatiotemporal variations of surface rock temperatures in high Drakensberg basalt. The temperature results are then used to discuss possible implications for thermal stress fatigue and frost-induced weathering. TinytalkÔ data loggers and probes were used for rock-surface temperature recording. Long-term measurements were recorded over 12 months from May 2002 to April 2003, at a 1-hour logging interval and rock depth of 1 cm for a highaltitude (3300 m a.s.l.) interfluve and fracture site. Whilst the north-facing rock surface experiences negligible hours below ,3°C, the south-facing rock surface and interfluve sites are subjected to considerable periods below ,3°C, which falls within the ,frost cracking window'. It is concluded that the substantial contrasts of recorded rock thermal parameters over small spatial scales between various topographic settings, highlight that site-specific measurements across the broader scale are required for an adequate evaluation of regional weathering and its associated landform development. [source] Rates Of Postglacial rock weathering on glacially scoured outcrops (Abisko,Riksgränsen area, 68°N)GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 3-4 2002Françoise André, Marie Ice,polished quartz veins, feldspar phenocrysts and quartzite layers were used as reference surfaces to assess the impact of Postglacial rock weathering in Lapland (68°N). Over 3200 measurements were carried out on roches moutonées and glaciofluvially scoured outcrops distributed within three study areas covering 8 km2. Inferred weathering rates demonstrate that 10,000 years of Holocene weathering did not significantly modify the geometry of Weichselian rock surfaces. However, rates of general surface lowering range from 1 to 25, depending on the rock type, with average values at 0.2 mm ka,1 for homogeneous crystalline rocks (irrespective of their acidity and grain size), 1 mm ka,1 for biotite,rich crystalline rocks, and 5 mm ka,1 for carbonate sedimentary rocks. Accelerated rates were recorded in weathering pits and along joints with values up to ten times higher than on the rest of the rock surface. Comparisons with cold and temperate areas suggest that solution rates of carbonate rocks are highly dependent on climate conditions, whilst granular disintegration of crystalline rocks operates at the same rate whatever the environment. It probably means that microgelivation is not efficient on ice,polished crystalline outcrops even under harsh climate conditions, and that granular disintegration proceeds under various climates from the same ubiquitous combination of biochemical processes. Last, the weathering state of Late,Weichselian roches moutonées can be usefully compared to that of Preglacial tors of the nearby Kiruna area. [source] Polymer-acid solutions: Their use for the enhancement of oil reservoir stimulationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Mohammed M. Amro Abstract A reduction in permeability occurring around the wellbore resulting from drilling, completion and/or workover fluids increases the flow resistance to the petroleum reservoir fluids and is defined as formation damage. Acidizing process removes near-wellbore damage and enhances hydrocarbon production from producing wells. This study investigates the effect of adding polymer as a retarding agent to acid solutions to slow and control the reaction in matrix acidizing treatment of carbonate rocks. Two different polymers, polyacrylamide (PAA) and polysaccharide (xanthan) and two different acids, acetic acid and formic acid, were used through this study. The results revealed that the presence of PAA did not change the viscosity of the acid solution significantly, while the viscosity of xanthan-acid solutions was decreased with increasing the acid concentration. Additionally, the reaction of polymer-acid solutions with the rock material was monitored under microscope. Original rock samples obtained from Saudi reservoirs containing mainly carbonate were used in the reaction. The PAA-acid solution did not show any decrease in the reaction rate compared to that of acid solution. Thus, the PAA solution applied in this study is not recommended as a retarder. However, xanthan-acid solutions showed a significant decrease in the reaction time. Therefore, xanthan was selected to perform further investigations in Rotating Disk Reactor at different pressures. Scanning electronic microscopy (SEM) was conducted on pretreated and posttreated rock samples. This provides the opportunity to perform a detailed description of the rock surface and facilitates the identification of the changes occurring due to polymer-acid treatment. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] FIELD STUDY OF ALGAL RECRUITMENT BY CLEARING EXPERIMENT IN PING CHAU, HONG KONG SAR, CHINAJOURNAL OF PHYCOLOGY, Issue 2000S. L. Kong Recruitment, the entry of new individuals into a population, was investigated by a clearing experiment along the shore of A Ma Wan (AMW) in Ping Chau, Hong Kong SAR, China. Two types of clearing, with all the existing vegetation removed (cleared) and with the top 2 to three mm of the rock surface removed (hammered), were carried out monthly in AMW from November 1997 to June 1999. Observations were made one month after clearing and on a monthly basis thereafter. The number of algal species present on the cleared areas and their percentage cover were recorded. The experimental results showed that more algal species were recruited during March and April in 1998 (n=10) but in 1999, the number of species was found higher in February and March (n=8). Species richness dropped after May (more obvious in 1998), indicating that recruitment greatly declined in summer. A tuft complex composed of several filamentous algal species dominated over the others in all clearing areas (coverage mostly over 90%) but recruits of Caulerpa peltata, Colpomenia sinuosa, Enteromorpha sp., Hypnea charoides, Padina spp., Sargassum sp., Spyridia filamentosa, Ulva sp., etc. also were observed during the study period. Generally, there were no significant differences in terms of species richness and composition of the recruits between the two treatments (cleared vs. hammered) as well as with the controls. This implied that algae in AMW were more likely to be recruited de novo from elsewhere rather than regenerated from remnants of the previous year's growth. [source] Physical modelling of bedrock brecciation by ice segregation in permafrostPERMAFROST AND PERIGLACIAL PROCESSES, Issue 3 2001J. B. Murton Abstract The lower half of a large block of moist chalk was maintained at subzero temperatures while the upper half was cyclically frozen and thawed, simulating 19 seasonal temperature cycles in an active layer above permafrost. During the experiment, the rock surface heaved vertically by at least 34.7 mm. Sixty-one percent of the heave occurred during freezing periods, and is attributed primarily to ice segregation accompanying upward freezing from the permafrost table during the early stages of simulated winters. Thirty-nine percent of the heave occurred during thawing periods, and is attributed to ice segregation in the frozen rock beneath the thaw front during the mid to late stages of simulated summers. By the end of the experiment, the middle horizon of the chalk, representing the upper part of the simulated permafrost and the basal part of the active layer, had become strongly brecciated and rich in segregated ice. The style of brecciation has similarities with that in perennially-frozen limestone, sandstone and shale in Svalbard and Canada, and chalk frozen during Quaternary cold stages in France and England. These similarities suggest that ice segregation during perennial and seasonal freezing is an important process of weathering and coarse-sediment supply in areas of frost-susceptible bedrock. Copyright © 2001 John Wiley & Sons, Ltd. RÉSUMÉ La moitié inférieure d'un gros bloc de craie humide a été maintenue à des températures inférieures à zéro degré (maintien d'un pergélisol) pendant que sa moitié supérieure était soumise alternativement au gel et au dégel, simulant ainsi 19 cycles saisonniers dans la couche active. Pendant l'expérience, la surface de la roche s'est soulevée verticalement de 34,7 mm. Soixante et un % du gonflement a été acquis pendant les périodes de gel simulant les hivers et attribué essentiellement à la ségrégation de glace accompagnant un gel à partir du sommet du pergélisol au début de ces périodes. Trente neuf % du gonflement a été enregistré pendant le milieu et la fin des périodes de dégel simulant les étés. Ceci est considéré comme le résultat de regels en-dessous du niveau atteint par le front de dégel. A la fin de l'expérience, la partie médiane du bloc, correspondant au sommet du pergélisol et à la base de la couche active, est apparue très fragmentée et riche en glace de ségrégation. Le type de fragmentation offre des aspects semblables à ceux qu'on observe dans les calcaires, grès et schistes gelés en permanence du Svalbard et du Canada et les craies soumises aux gels des stades froids du Quaternaire en France et en Angleterre. Cela suggère que la ségrégation de la glace pendant les périodes de gel permanent ou saisonnier est un important processus de fragmentation des roches et de fourniture de sédiments grossiers dans les régions où les roches sont sensibles au gel. Copyright © 2001 John Wiley & Sons, Ltd. [source] Processes controlling rapid temperature variations on rock surfaces,EARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2010Jamie L. Molaro Abstract In arid environments, thermal oscillations are an important source of rock weathering. Measurements of temperature have been made on the surface of rocks in a desert environment at a sampling interval of 0·375,s, with simultaneous measurements of wind speed, air temperature, and incoming shortwave radiation. Over timescales of hours, the temperature of the rock surface was determined primarily by shortwave radiation and air temperature, while rapid temperature variations, high dT/dt, at intervals of seconds or less, were determined by wind speed. The maximum values of temperature change and time spent above 2°C,min,1 increased at high measurement rates and were much higher than previously reported. The maximum recorded value of dT/dt was 137°C,min,1 and the average percentage time spent above 2°C,min,1 was ,70 ± 13%. Maximum values of dT/dt did not correlate with the maximum values of time spent above 2°C,min,1. Simultaneous measurements of two thermocouples 5·5,cm apart on a single rock surface had similar temperature and dT/dt values, but were not correlated at sampling intervals of less than 10,s. It is suggested that this is resulting from rapid fluctuations due to small spatial and timescale wind effects that are averaged out when data is taken at longer sampling intervals, ,10,s or greater. Published in 2010 by John Wiley & Sons, Ltd. [source] Long-term landscape evolution: linking tectonics and surface processesEARTH SURFACE PROCESSES AND LANDFORMS, Issue 3 2007Paul Bishop Abstract Research in landscape evolution over millions to tens of millions of years slowed considerably in the mid-20th century, when Davisian and other approaches to geomorphology were replaced by functional, morphometric and ultimately process-based approaches. Hack's scheme of dynamic equilibrium in landscape evolution was perhaps the major theoretical contribution to long-term landscape evolution between the 1950s and about 1990, but it essentially ,looked back' to Davis for its springboard to a viewpoint contrary to that of Davis, as did less widely known schemes, such as Crickmay's hypothesis of unequal activity. Since about 1990, the field of long-term landscape evolution has blossomed again, stimulated by the plate tectonics revolution and its re-forging of the link between tectonics and topography, and by the development of numerical models that explore the links between tectonic processes and surface processes. This numerical modelling of landscape evolution has been built around formulation of bedrock river processes and slope processes, and has mostly focused on high-elevation passive continental margins and convergent zones; these models now routinely include flexural and denudational isostasy. Major breakthroughs in analytical and geochronological techniques have been of profound relevance to all of the above. Low-temperature thermochronology, and in particular apatite fission track analysis and (U,Th)/He analysis in apatite, have enabled rates of rock uplift and denudational exhumation from relatively shallow crustal depths (up to about 4 km) to be determined directly from, in effect, rock hand specimens. In a few situations, (U,Th)/He analysis has been used to determine the antiquity of major, long-wavelength topography. Cosmogenic isotope analysis has enabled the determination of the ,ages' of bedrock and sedimentary surfaces, and/or the rates of denudation of these surfaces. These latter advances represent in some ways a ,holy grail' in geomorphology in that they enable determination of ,dates and rates' of geomorphological processes directly from rock surfaces. The increasing availability of analytical techniques such as cosmogenic isotope analysis should mean that much larger data sets become possible and lead to more sophisticated analyses, such as probability density functions (PDFs) of cosmogenic ages and even of cosmogenic isotope concentrations (CICs). PDFs of isotope concentrations must be a function of catchment area geomorphology (including tectonics) and it is at least theoretically possible to infer aspects of source area geomorphology and geomorphological processes from PDFs of CICs in sediments (,detrital CICs'). Thus it may be possible to use PDFs of detrital CICs in basin sediments as a tool to infer aspects of the sediments' source area geomorphology and tectonics, complementing the standard sedimentological textural and compositional approaches to such issues. One of the most stimulating of recent conceptual advances has followed the considerations of the relationships between tectonics, climate and surface processes and especially the recognition of the importance of denudational isostasy in driving rock uplift (i.e. in driving tectonics and crustal processes). Attention has been focused very directly on surface processes and on the ways in which they may ,drive' rock uplift and thus even influence sub-surface crustal conditions, such as pressure and temperature. Consequently, the broader geoscience communities are looking to geomorphologists to provide more detailed information on rates and processes of bedrock channel incision, as well as on catchment responses to such bedrock channel processes. More sophisticated numerical models of processes in bedrock channels and on their flanking hillslopes are required. In current numerical models of long-term evolution of hillslopes and interfluves, for example, the simple dependency on slope of both the fluvial and hillslope components of these models means that a Davisian-type of landscape evolution characterized by slope lowering is inevitably ,confirmed' by the models. In numerical modelling, the next advances will require better parameterized algorithms for hillslope processes, and more sophisticated formulations of bedrock channel incision processes, incorporating, for example, the effects of sediment shielding of the bed. Such increasing sophistication must be matched by careful assessment and testing of model outputs using pre-established criteria and tests. Confirmation by these more sophisticated Davisian-type numerical models of slope lowering under conditions of tectonic stability (no active rock uplift), and of constant slope angle and steady-state landscape under conditions of ongoing rock uplift, will indicate that the Davis and Hack models are not mutually exclusive. A Hack-type model (or a variant of it, incorporating slope adjustment to rock strength rather than to regolith strength) will apply to active settings where there is sufficient stream power and/or sediment flux for channels to incise at the rate of rock uplift. Post-orogenic settings of decreased (or zero) active rock uplift would be characterized by a Davisian scheme of declining slope angles and non-steady-state (or transient) landscapes. Such post-orogenic landscapes deserve much more attention than they have received of late, not least because the intriguing questions they pose about the preservation of ancient landscapes were hinted at in passing in the 1960s and have recently re-surfaced. As we begin to ask again some of the grand questions that lay at the heart of geomorphology in its earliest days, large-scale geomorphology is on the threshold of another ,golden' era to match that of the first half of the 20th century, when cyclical approaches underpinned virtually all geomorphological work. Copyright © 2007 John Wiley & Sons, Ltd. [source] Two-hourly surface change on supra-tidal rock (Marengo, Victoria, Australia)EARTH SURFACE PROCESSES AND LANDFORMS, Issue 1 2007Lluís Gómez-Pujol Abstract A traversing micro-erosion meter was used to measure rock surface micro-topography over 40 cm2 on a supra-tidal cliff face from early morning to late evening in late spring. From 06:00 hours to 22:00 hours the relative heights of 188 coordinates were obtained using the meter at 2-hour intervals, resulting in a data set of 1607 readings. Monitoring shows that rock surfaces are dynamic entities, with significant rise and fall relative to the first measurement at shorter timescales than previously reported. The maximum positive rise between readings was 0·261 mm and lowering was 0·126 mm. The pattern of change did not relate as expected to environmental variables such as temperature or insolation. Rather, the surface showed greater surface change in the early morning and late afternoon. It is hypothesized that this pattern relates to the expansion and contraction of lichen thalli as moisture is absorbed during higher humidity in the morning and late afternoon. The implications of these results for weathering studies are considered. Copyright © 2006 John Wiley & Sons, Ltd. [source] Phylogenetic 16S rRNA analysis reveals the presence of complex and partly unknown bacterial communities in Tito Bustillo cave, Spain, and on its Palaeolithic paintingsENVIRONMENTAL MICROBIOLOGY, Issue 7 2002Claudia Schabereiter-Gurtner Summary Tito Bustillo cave (Ribadesella, Spain) contains valuable Palaeolithic paintings, which date back 15 000,20 000 years. Since 1969, the cave has been open to the public. Rock wall surfaces, spelaeothems and soils are covered by apparent biofilms of phototrophic microorganisms, which develop under artificial lighting. In addition, rock surfaces present conspicuous bacterial growth in the form of round colonies of different colours and about 1,2 mm in diameter. Even the famous Paintings Panel shows some evident microbial growth. In the present study, bacterial communities on the paintings and on the rock surfaces near the paintings were analysed by culture-independent techniques, including polymerase chain reaction (PCR) amplification of bacterial 16S rRNA genes (16S rDNA), phylogenetic sequence analyses and genetic community fingerprinting by denaturing gradient gel electrophoresis (DGGE). DGGE fingerprints showed complex bacterial community patterns. Forty-one clones matching DGGE bands of the community fingerprints were sequenced, representing about 39% of DNA fragments in the DGGE patterns. Phylogenetic sequence analyses revealed a high number of phylogenetically novel 16S rDNA sequence types and a high diversity of putatively chemotrophic and heterotrophic bacteria. Sequences were phylogenetically most closely related to the Proteobacteria (20 clones), green non-sulphur bacteria (three clones), Planctomycetales order (one clone), Cytophaga,Flexibacter, Bacteroides division (one clone) and the Actinobacteria (four clones). Furthermore, we report the presence of members of the Acidobacterium division (12 clones) in a karstic hypogean environment. Members of this phylum have not so far been detected in these particular environments. [source] AN EVALUATION OF SURFACE HARDNESS OF NATURAL AND MODIFIED ROCKS USING SCHMIDT HAMMER: STUDY FROM NORTHWESTERN HIMALAYA, INDIAGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 3 2009VIKRAM GUPTA ABSTRACT. Four rock types (quartz mica gneiss, schist, quartzite and calc-silicate) located in the Satluj and Alaknanda valleys were used to test whether a Schmidt hammer can be used to distinguish rock surfaces affected by various natural and man-induced processes like manual smoothing of rock surfaces by grindstone, surface weathering, deep weathering, fluvial polishing and blasting during road construction. Surfaces polished by fluvial process yielded the highest Schmidt hammer rebound (R-) values and the blast-affected surfaces yielded the lowest R-values for the same rock type. Variations in R-value also reflect the degree of weathering of the rock surfaces. It has been further observed that, for all the rock types, the strength of relationship between R-values for the treated surfaces (manual smoothing of rock surface by grindstone) and the unconfined compressive strength (UCS) is higher than for the fresh natural surfaces. [source] Rates Of Postglacial rock weathering on glacially scoured outcrops (Abisko,Riksgränsen area, 68°N)GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 3-4 2002Françoise André, Marie Ice,polished quartz veins, feldspar phenocrysts and quartzite layers were used as reference surfaces to assess the impact of Postglacial rock weathering in Lapland (68°N). Over 3200 measurements were carried out on roches moutonées and glaciofluvially scoured outcrops distributed within three study areas covering 8 km2. Inferred weathering rates demonstrate that 10,000 years of Holocene weathering did not significantly modify the geometry of Weichselian rock surfaces. However, rates of general surface lowering range from 1 to 25, depending on the rock type, with average values at 0.2 mm ka,1 for homogeneous crystalline rocks (irrespective of their acidity and grain size), 1 mm ka,1 for biotite,rich crystalline rocks, and 5 mm ka,1 for carbonate sedimentary rocks. Accelerated rates were recorded in weathering pits and along joints with values up to ten times higher than on the rest of the rock surface. Comparisons with cold and temperate areas suggest that solution rates of carbonate rocks are highly dependent on climate conditions, whilst granular disintegration of crystalline rocks operates at the same rate whatever the environment. It probably means that microgelivation is not efficient on ice,polished crystalline outcrops even under harsh climate conditions, and that granular disintegration proceeds under various climates from the same ubiquitous combination of biochemical processes. Last, the weathering state of Late,Weichselian roches moutonées can be usefully compared to that of Preglacial tors of the nearby Kiruna area. [source] Biology and taxonomy of encrusting alcyoniid soft corals in the northeastern Pacific Ocean with descriptions of two new genera (Cnidaria, Anthozoa, Octocorallia)INVERTEBRATE BIOLOGY, Issue 2 2003Catherine S. McFadden Abstract. In this paper we summarize current knowledge of the distribution, ecology, and reproductive biology of 4 encrusting species in the soft coral family Alcyoniidae, with descriptions of 2 new genera and 2 new species. The new genus Discophyton is erected for Alcyonium rudyi, a species common in the lower intertidal of exposed rocky headlands from Vancouver Island, British Columbia, Canada south to Point Lobos, California, USA. Discophyton rudyi n. gen. & n. comb. propagates extensively by clonal fission, giving rise to characteristic aggregations of small, regularly spaced, disc-shaped colonies. We describe 2 new species and place them in a new genus, Thrombophyton. Thrombophyton coronatum n. gen. & n. sp. forms irregularly shaped, membranous colonies on rock surfaces; it occurs subtidally along the southern California coast from the Palos Verdes Peninsula to San Diego and on the California Islands. Thrombophyton trachydermum n. gen. & n. sp. has a similar, membranous growth form; it occurs both intertidally and subtidally on Vancouver Island, British Columbia, Canada, and in the San Juan Archipelago, Washington, and intertidally in central California, USA. Alcyonium pacificum, reported for the first time from North American waters, occurs in subtidal kelp beds around the Aleutian islands of Attu and Adak; its mushroom-shaped colonies are raised above the substrate on a short stalk. D. rudyi, T. trachydermum, and A. pacificum are all gonochores that reproduce in late summer; in contrast, T. coronatum appears to reproduce in the spring. D. rudyi and T. coronatum brood larvae internally to a late planula stage. A key to species is presented for all shallow-water soft corals known to occur in the northeastern Pacific Ocean. [source] Surface exposure dating of the Great Aletsch Glacier Egesen moraine system, western Swiss Alps, using the cosmogenic nuclide 10BeJOURNAL OF QUATERNARY SCIENCE, Issue 5 2004Meredith A. Kelly Abstract Egesen moraines throughout the Alps mark a glacial advance that has been correlated with the Younger Dryas cold period. Using the surface exposure dating method, in particular the measurement of the cosmogenic nuclide 10Be in rock surfaces, we attained four ages for boulders on a prominent Egesen moraine of Great Aletsch Glacier, in the western Swiss Alps. The 10Be dates range from 10,460±1100 to 9040±1020,yr ago. Three 10Be dates between 9630±810 and 9040±1020,yr ago are based upon samples from the surfaces of granite boulders. Two 10Be dates, 10,460±1100 and 9910±970,yr ago, are based upon a sample from a quartz vein at the surface of a schist boulder. In consideration of the numerous factors that can influence apparently young 10Be dates and the scatter within the data, we interpret the weighted mean of four boulder ages, 9640±430,yr (including the weighted mean of two 10Be dates of the quartz vein), as a minimum age of deposition of the moraine. All 10Be dates from the Great Aletsch Glacier Egesen moraine are consistent with radiocarbon dates of nearby bog-bottom organic sediments, which provide minimum ages of deglaciation from the moraine. The 10Be dates from boulders on the Great Aletsch Glacier Egesen moraine also are similar to 10Be dates from Egesen moraines of Vadret Lagrev Glacier on Julier Pass, in the eastern Swiss Alps. Both the morphology of the Great Aletsch Glacier Egesen moraine and the comparison with 10Be dates from the inner Vadret Lagrev Egesen moraine support the hypothesis that the climatic cooling that occurred during the Younger Dryas cold episode influenced the glacial advance that deposited the Great Aletsch Glacier Egesen moraine. Because of the large size and slow response time of Great Aletsch Glacier, we suggest that the Great Aletsch Glacier Egesen moraine was formed during the last glacial advance of the multiphased Egesen cold period, the Kromer stage, during the Preboreal chron. Copyright © 2004 John Wiley & Sons, Ltd. [source] Mycosporine-glutamicol-glucoside: a natural UV-absorbing secondary metabolite of rock-inhabiting microcolonial fungiRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2003Marc Volkmann Microcolonial ascomycetes are known to inhabit bare rock surfaces in cold and hot deserts and thus are habitually exposed to high levels of solar radiation. Several of these stress-tolerant fungal isolates, cultivated in the laboratory under daylight illumination, were studied for the presence of effective UV-radiation protection substances. Liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) analyses allowed for efficient separation and structure clarification of two mycosporines. It was demonstrated that both mycosporine-glutamicol-glucoside and mycosporine-glutaminol-glucoside are natural and constitutive secondary metabolites of microcolonial fungi. The function and relation of these substances in the fungal cell are discussed. Copyright © 2003 John Wiley & Sons, Ltd. [source] The evolutionary ecology of detritus feeding in the larvae of freshwater DipteraBIOLOGICAL REVIEWS, Issue 1 2009Athol J. McLachlan Abstract Detritus (dead organic matter), largely of terrestrial origin, is superabundant in inland waters but because of its indigestible nature, would appear to be a poor food source for animals. Yet this unpromising material is widely used as food and indeed can be viewed as a defining characteristic of the freshwater environment. We here explore the relationships among animals, detritus and its associated micro-organism decomposers, taking a functional approach. We pose questions about interrelationships and attempt to arrive at new insights by disentangling them from an adaptive point of view. To do this we have been careful in selecting the habitats for detailed consideration. Rain pools on rock surfaces in tropical Africa and pools on peat moorland in the UK were chosen. Both examples have a relatively simple community structure and hence offer the prospect of achieving our aim. As model organisms for study we focus principally on the aquatic stages of selected holometabolous insects; that is, selected genera of the universally common midges, Ceratopogonidae and Chironomidae. We approach these case studies from an evolutionary ecology perspective and see detritus as a simple template upon which a beautiful complex of adaptations can evolve. [source] 10Be dating of Younger Dryas Salpausselkä I formation in FinlandBOREAS, Issue 4 2000SILVIO TSCHUDI Boulders of the Younger Dryas Salpausselkä I (Ss I) formation west of Lahti, southern Finland, were sampled for surface exposure dating. The 10Be concentrations, determined by accelerator mass spectrometry, yield minimum exposure ages of 11 930 ± 950, 11 220 ± 890, 11 050 ± 910 and 11 540 ± 990 years, using recently published production rates scaled for latitude and elevation. This includes a correction to the production rate resulting from postglacial uplift of the Fennoscandian lithosphere (i.e. changing elevation) during the time of exposure. The error-weighted mean exposure age of 11 420 ± 470 years of the analysed boulders agrees with previous varve dates of Ss I, which range from 11 680 to 11 430 calendar years BP. However, erosion has to be taken into account as a process affecting rock surfaces and therefore influencing exposure ages. Available information suggests an erosion rate of 5 mm/kyr, which increases the error-weighted mean exposure age to a value of 11 610 ± 470 years. Within the errors, the formation of Ss I in the Vesala area west of Lahti falls into the Younger Dryas time bracket, as defined by the GRIP and GISP 2 ice core (Greenland). [source] | |||||||||||||||||||