Geological mysteries of the Plain of Jars begin to unravel     

Jeremy Baldock  & Julie Van Den Bergh 《Geology Today》2009,25(4):145-150

The Plain of Jars in north-eastern Laos is home to over 2000 stone jars varying in size from 100 kg to over 30 tonnes. The jars were probably made between 1500 and 2500 years ago; however, who by is not known, as the indigenous people have only lived in the area for 1000 years. Local legend speaks of these jars being used to store Lao-Lao or rice whisky; research indicates that these jars were part of loca funerary rites. There are currently 60 known jar sites, where anywhere between one and 350 individual jars are recorded. The jars are constructed from a variety of lithologies although a few basic rules to selecting suitable rocks have been observed. This study outlines which rock types have been used and how the characteristics of the rock mass controlled the jar makers' selection.  相似文献   

Causes of systematic over‐ or underestimation of low streamflows by use of index‐streamgage approaches in the United States     

Ken Eng  Julie E. Kiang  Yin‐Yu Chen  Daren M. Carlisle  Gregory E. Granato 《水文研究》2011,25(14):2211-2220

Low‐flow characteristics can be estimated by multiple linear regressions or the index‐streamgage approach. The latter transfers streamflow information from a hydrologically similar, continuously gaged basin (‘index streamgage’) to one with a very limited streamflow record, but often results in biased estimates. The application of the index‐streamgage approach can be generalized into three steps: (1) selection of streamflow information of interest, (2) definition of hydrologic similarity and selection of index streamgage, and (3) application of an information‐transfer approach. Here, we explore the effects of (1) the range of streamflow values, (2) the areal density of streamgages, and (3) index‐streamgage selection criteria on the bias of three information‐transfer approaches on estimates of the 7‐day, 10‐year minimum streamflow (Q_{7, 10}). The three information‐transfer approaches considered are maintenance of variance extension, base‐flow correlation, and ratio of measured to concurrent gaged streamflow (Q‐ratio invariance). Our results for 1120 streamgages throughout the United States suggest that only a small portion of the total bias in estimated streamflow values is explained by the areal density of the streamgages and the hydrologic similarity between the two basins. However, restricting the range of streamflow values used in the index‐streamgage approach reduces the bias of estimated Q_{7, 10} values substantially. Importantly, estimated Q_{7, 10} values are heavily biased when the observed Q_{7, 10} values are near zero. Results of the analysis also showed that Q_{7, 10} estimates from two of the three index‐streamgage approaches have lower root‐mean‐square error values than estimates derived from multiple regressions for the large regions considered in this study. Published in 2011 by John Wiley & Sons, Ltd.  相似文献   

Evidence of multidecadal climate variability and the Atlantic Multidecadal Oscillation from a Gulf of Mexico sea-surface temperature-proxy record   总被引：1，自引：1，他引：0  

Richard Z. Poore  Kristine L. DeLong  Julie N. Richey  Terrence M. Quinn 《Geo-Marine Letters》2009,29(6):477-484

A comparison of a Mg/Ca-based sea-surface temperature (SST)-anomaly record from the northern Gulf of Mexico, a calculated index of variability in observed North Atlantic SST known as the Atlantic Multidecadal Oscillation (AMO), and a tree-ring reconstruction of the AMO contain similar patterns of variation over the last 110 years. Thus, the multidecadal variability observed in the instrumental record is present in the tree-ring and Mg/Ca proxy data. Frequency analysis of the Gulf of Mexico SST record and the tree-ring AMO reconstruction from 1550 to 1990 found similar multidecadal-scale periodicities (~30–60 years). This multidecadal periodicity is about half the observed (60–80 years) variability identified in the AMO for the 20th century. The historical records of hurricane landfalls reveal increased landfalls in the Gulf Coast region during time intervals when the AMO index is positive (warmer SST), and decreased landfalls when the AMO index is negative (cooler SST). Thus, we conclude that alternating intervals of high and low hurricane landfall occurrences may continue on multidecadal timescales along the northern Gulf Coast. However, given the short length of the instrumental record, the actual frequency and stability of the AMO are uncertain, and additional AMO proxy records are needed to establish the character of multidecadal-scale SST variability in the North Atlantic.  相似文献   

Observed and simulated water and energy budget components at SCAN sites in the lower Mississippi Basin     

Gabriëlle J. M. De Lannoy  Julie Ufford  Alok K. Sahoo  Paul Dirmeyer  Paul R. Houser 《水文研究》2011,25(4):634-649

Land surface models are typically constrained by one or a few observed variables, while assuming that the internal water and energy partitioning is sensitive to those observed variables and realistic enough to simulate unobserved variables. To verify these assumptions, in situ soil climate analysis network (SCAN) observations in the Lower Mississippi Basin (2002–2008) are analysed to quantify water and energy budget components and they are compared to Community Land Model (CLM3·5) simulations. The local soil texture is identified as a major indicator for water storage characteristics and the Normalized Difference Vegetation Index shows potential as a drought indicator in summer months. Both observations and simulations indicate a regime where, except in some summer months, evapotranspiration controls soil moisture. CLM simulations with different soil texture assignments show discharge sensitivity to soil moisture, but almost no impact on evapotranspiration and other energy balance components. The observed and simulated water budgets show a similar partitioning. However, the SCAN observed water balance does not close because of precipitation measurement errors, unobserved irrigation, lack of specific storage change measurements and errors in the computed actual evapotranspiration. The simulated heat flux partitioning differs from that ‘observed’, with a larger (resp. smaller) fraction of net radiation being used by latent (resp. sensible) heat flux, and unobserved freeze and thaw events. The comparison between observations and model simulations suggests that a consistent observation collection for multiple variables would be needed to constrain and improve the full set of land surface variable estimates. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Plagioclase zonation styles in hornblende gabbro inclusions from Little Glass Mountain,Medicine Lake volcano,California: implications for fractionation mechanisms and the formation of composition gaps     

J. G. Brophy  Michael J. Dorais  Julie Donnelly-Nolan  Bradley S. Singer 《Contributions to Mineralogy and Petrology》1996,126(1-2):121-136

The rhyolite of Little Glass Mountain (73–74% SiO₂) is a single eruptive unit that contains inclusions of quenched andesite liquid (54–61% SiO₂) and partially crystalline cumulate hornblende gabbro (53–55% SiO₂). Based on previous studies, the quenched andesite inclusions and host rhyolite lava are related to one another through fractional crystallization and represent an example of a fractionation-generated composition gap. The hornblende gabbros represent the cumulate residue associated with the rhyolite-producing and composition gap-forming fractionation event. This study combines textural (Nomarski Differential Interference Contrast, NDIC, imaging), major element (An content) and trace element (Mg, Fe, Sr, K, Ti, Ba) data on the style of zonation of plagioclase crystals from representative andesite and gabbro inclusions, to assess the physical environment in which the fractionation event and composition gap formation took place. The andesite inclusions (54–61% SiO₂) are sparsely phyric with phenocrysts of plagioclase, augite and Fe-oxide±olivine, +/–orthopyroxene, +/–hornblende set within a glassy to crystalline matrix. The gabbro cumulates (53–55% SiO₂) consist of an interconnected framework of plagioclase, augite, olivine, orthopyroxene, hornblende and Fe-oxide along with highly vesicular interstitial glass (70–74% SiO₂). The gabbros record a two-stage crystallization history of plagioclase+olivine+augite (Stage I) followed by plagioclase+orthopyroxene+ hornblende+Fe-oxide (Stage II). Texturally, the plagioclase crystals in the andesite inclusions are characterized by complex, fine-scale oscillatory zonation and abundant dissolution surfaces. Compositionally (An content) the crystals are essentially unzoned from core-to-rim. These features indicate growth within a dynamic (convecting?), reservoir of andesite magma. In contrast, the plagioclase crystals in the gabbros are texturally smooth and featureless with strong normal zonation from An₇₄ at the core to around An₃₀. K, and Ba abundances increase and Mg abundances decrease steadily towards the rim. Ti, Fe, and Sr abundances increase and then decrease towards the rim. The trace element variations are fully consistent with the two-stage crystallization sequence inferred from the gabbro mineralogy. These results indicate progressive closed-system in situ crystallization in a quiescent magmatic boundary layer environment located along the margins of the andesite magma body. The fractional crystallization that generated the host rhyolite lava is one of inward solidification of a crystallizing boundary layer followed by melt extraction and accumulation of highly evolved interstitial liquid. This mechanism explains the formation of the composition gap between parental andesite and rhyolite magma compositions.  相似文献   

Intraspecific Interactions and Risk of Predation for Dyspanopeus sayi (Decapoda: Xanthidae) Living on Polychaete (Filograna implexa,Serpulidae) Colonies*     

Kenneth L. Heck  Julie Anne Hambrook 《Marine Ecology》1991,12(3):243-250

Abstract. Along the Atlantic coast of the United States, the mud crab Dyspanopeus sayi frequently occurs in crevices and depressions within aggregated calcareous tubes (termed “heads”) of the serpulid polychaete Filograna implexa. In New Jersey, U.S.A., waters, crab number was significantly correlated with the logarithm of worm tube colony volume. Laboratory experiments suggested that crabs compete for shelter within worm colonies. Additional laboratory experiments indicated that colony occupancy greatly decreased the risk of predation by blue crabs (Callinectes sapidus), and field tethering experiments also demonstrated that colony occupancy significantly decreased predation risk. Thus, the consequence of holding space on worm tube heads is a greatly increased probability of survival.  相似文献   

Ichthyoplankton distribution and abundance off the west coast of Ireland     

O'Brien  Barry; Fives  Julie M. 《ICES Journal of Marine Science》1995,52(2):233-245

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Seasonal factors affecting egg production and viability of eggs of Acartia tonsa Dana from East Lagoon, Galveston, Texas     

Julie Weills Ambler 《Estuarine, Coastal and Shelf Science》1985,20(6):743-760

Egg production and hatching success were determined between March 1981 and March 1982 for the copepod Acartia tonsa Dana from East Lagoon, Galveston, Texas. During three-day experiments in the laboratory, field collected females were fed diets of (1) natural particles collected over the water column, (2) some modification of this and (3) the diatom Thalassiosira weissflogii. The latter served to isolate the effects of temperature and salinity from the effects of the natural particle diets on egg production. Specific rates of egg production, i.e. μg egg biomass/μg body biomass/time, were consistently higher per unit carbon than nitrogen.The influence of seasonal factors on egg production was compared. Salinity was inversely correlated with egg production, but had less effect than temperature. Positive correlations with temperature were always higher for specific rates per unit nitrogen than carbon. At 15°C, females produced 0·25 of their body carbon (or nitrogen) as eggs per day, whereas at 28°C, they produced at least their own biomass as eggs per day (up to 1·80). These high rates of A. tonsa were probably due to its reproductive biology and adaptation to the subtropical habitat as well as the high temperatures and food concentrations. The correlation between specific egg production rate and temperature was less with the natural particle diets than with the unialgal diet. This indicated that the quantity or quality of natural particle assemblages in East Lagoon influenced egg production. Egg viability was highest in the spring, but was not related to diet or the percentage of females with spermatophores.  相似文献   

Bacterioplanktonic abundance,productivity and petroleum hydrocarbon biodegradation in marinas and other coastal waters in North Carolina,USA     

Piehler MF  Maloney JS  Paerl HW 《Marine environmental research》2002,54(2):157-168

The purpose of this study was to assess the differences in the abundance and activity of the bacterioplankton at sites with varied boating activity, and to determine the response of the communities to additional petroleum pollution. Three sites, including two marinas and a site on Bogue Sound in coastal North Carolina, were selected for monthly experiments. Seasonal patterns of bacterioplanktonic abundance and diesel fuel biodegradation for each site were examined, and possible correlations with intensity of boating activities were explored. Bacterioplanktonic communities at the three sites in this study were more similar in their structure and biodegradation potential than would have been expected from previous studies. We found no differences in the abundance and biodegradation potential of theses communities at the three sites, and only a slightly elevated number of hydrocarbon degraders at one of the marinas. Patterns of biodegradation were more closely related to total bacterial abundance, rather than number of petroleum hydrocarbon degraders. There was a strong seasonal pattern in bacterial abundance and biodegradation at all three sites. The bacterioplanktonic Community at all sites responded similarly to additions of diesel fuel. Bacterial abundance and productivity were both elevated to some extent, and number of petroleum hydrocarbon degraders changed relatively little. These data indicate that marinas may not profoundly after the bacterioplankton and that coastal waters often have resident bacterial communities capable of degrading petroleum hydrocarbon pollution.  相似文献   

Protection, Pollution Prevention and Control of Environment in Construction Stage     

Julie Q. Shang 《Marine Georesources & Geotechnology》2003,21(3):227-235

The proposed Taiwan Strait Tunnel will raise numerous challenges for environmental professionals. The environmental issues must be incorporated in the preliminary study, planning, design, and construction of the works and be addressed consistently throughout all phases of the project. In this article, the environmental issues that will be encountered in the construction stage are discussed, including environmental impact assessment, environmental monitoring, and specific environmental issues during construction such as spoil handling, air quality and noise control, drainage, and health and safety. The experience and practice of handling environmental issues during the construction English Channel Tunnel are reviewed throughout the discussion.  相似文献