A New Theropod Dinosaur from the Middle Jurassic of Lufeng, Yunnan, China     

WU Xiao-chun  Philip J.CURRIE  DONG Zhiming  PAN Shigang  WANG Tao 《《地质学报》英文版》2009,83(1)

A new theropod dinosaur,Shidaisaurusjinae gen.et sp.nov.,has been described on the basis of an incomplete skeleton.The specimen was found near the base of the Upper Lufeng Formation(early Middle Jurassic)in Yunnan,China.It is the first theropod dinosaur from the Middle Jurassic of Yunnan.Shidaisaurus jinae is distinguishable from other Jurassic theropods by certain features from the braincase,axis,and pelvic girdle.The absence of any pleurocoels in the axis or in any anterior dorsal vertebrae suggests that the new Lufeng theropod is relatively primitive and more plesiomorphic than most of the Middle to Late Jurassic theropods from China.Most Chinese taxa of Jurassic theropod dinosaurs have not been well described;a further detailed study will be necessary for us to determine their phylogenetic relationships with Shidaisaurus jinae.  相似文献   

Monitoring hydraulic processes with automated time-lapse electrical resistivity tomography (ALERT)     

Oliver Kuras  Jonathan D. Pritchard  Philip I. Meldrum  Jonathan E. Chambers  Paul B. Wilkinson  Richard D. Ogilvy  Gary P. Wealthall 《Comptes Rendus Geoscience》2009,341(10-11):868-885

Hydraulic processes in porous media can be monitored in a minimally invasive fashion by time-lapse electrical resistivity tomography (ERT). The permanent installation of specifically designed ERT instrumentation, telemetry and information technology (IT) infrastructure enables automation of data collection, transfer, processing, management and interpretation. Such an approach gives rise to a dramatic increase in temporal resolution, thus providing new insight into rapidly occurring subsurface processes. In this paper, we discuss a practical implementation of automated time-lapse ERT. We present the results of a recent study in which we used controlled hydraulic experiments in two test cells at reduced field scale to explore the limiting conditions for process monitoring with cross-borehole ERT measurements. The first experiment used three adjacent boreholes to monitor rapidly rising and falling water levels. For the second experiment, we injected a saline tracer into a homogeneous flow field in freshwater-saturated sand; the dynamics of the plume were then monitored with 2D measurements across a 9-borehole fence and 3D measurements across a 3 × 3 grid of boreholes. We investigated different strategies for practical data acquisition and show that simple re-ordering of ERT measurement schemes can help harmonise data collection with the nature of the monitored process. The methodology of automated time-lapse ERT was found to perform well in different monitoring scenarios (2D/3D plus time) at time scales associated with realistic subsurface processes. The limiting factor is the finite amount of time needed for the acquisition of sufficiently comprehensive datasets. We found that, given the complexity of our monitoring scenarios, typical frame rates of at least 1.5–3 images per hour were possible without compromising image quality.  相似文献   

Morphotectonic evolution of Parduni Basin: An intradun piggyback basin in western Doon valley,NW Outer Himalaya     

G. Philip  N. S. Virdi  N. Suresh 《Journal of the Geological Society of India》2009,74(2):189-199

During the course of mapping of active faults in the northwestern Outer Himalaya (using CORONA photographs, multispectral satellite data of Indian Remote Sensing satellite (IRS) and aerial photographs) we have identified an isolated basin of Quaternary and Holocene sediments resting unconformably on Siwaliks, around Parduni, in the northwestern Dehra Dun (Doon) valley. The region around Parduni is tectonically very complex and is traversed by active thrust faults to its north and south and strike slip faults to its east and west. The uplift and southward shift along the strike slip faults on both sides and the Markanda thrust edging to its south, the Parduni has developed as an intradun basin and now remains isolated from the main Doon valley. Based on the OSL age data widespread deposition of Quaternary alluvial fan sediments, the dun gravels, is inferred to have initiated around 34 ka BP in the western part of the Doon valley, while the sedimentation in the Parduni Basin started only around 27 ka BP, which more or less ceased around 20 ka. The southward movement of the Parduni Basin as a piggyback basin is ongoing with recent alluvial deposits covering the dun gravels tectonically overlain by the Siwalik sandstone and mudstones in the hanging wall of the Markanda thrust. The present communication discusses the development and evolution of the Parduni Basin vis-à-vis the configuration of the Doon valley in the northwestern Outer Himalaya and the prevalence of tectonics expressed or demonstrated in the active Himalayan Front.  相似文献   

Comparing fire-history interpretations based on area, number and estimated volume of macroscopic charcoal in lake sediments     

Adam A. Ali  Philip E. Higuera  Yves Bergeron  Christopher Carcaillet   《Quaternary Research》2009,72(3):462-468

Sedimentary charcoal particles from lakes are commonly used to investigate fire history. Fire-history reconstructions are based on measuring the surface area or counting the number of charcoal fragments in adjacent samples. Recently, the volume of charcoal particles was advised as a more accurate method for quantifying past charcoal production. Large charcoal datasets, used to synthesize global fire history, include these different types of charcoal measurements and implicitly assume that they provide comparable fire-history information. However, no study has demonstrated that this assumption is valid. Here we compare fire-frequency reconstructions based on measurements of charcoal area and number, and estimates of charcoal volume from two lake sediment records from the eastern Canadian boreal forest. Results indicate that the three proxies provide comparable fire-history interpretations when using a locally defined threshold to identify fire events.  相似文献   

Naturally acidic surface and ground waters draining porphyry-related mineralized areas of the Southern Rocky Mountains,Colorado and New Mexico     

Philip L. Verplanck  D. Kirk Nordstrom  Dana J. Bove  Geoffrey S. Plumlee  Robert L. Runkel 《Applied Geochemistry》2009

Acidic, metal-rich waters produced by the oxidative weathering and resulting leaching of major and trace elements from pyritic rocks can adversely affect water quality in receiving streams and riparian ecosystems. Five study areas in the southern Rocky Mountains with naturally acidic waters associated with porphyry mineralization were studied to document variations in water chemistry and processes that control the chemical variations. Study areas include the Upper Animas River watershed, East Alpine Gulch, Mount Emmons, and Handcart Gulch in Colorado and the Red River in New Mexico. Although host-rock lithologies in all these areas range from Precambrian gneisses to Cretaceous sedimentary units to Tertiary volcanic complexes, the mineralization is Tertiary in age and associated with intermediate to felsic composition, porphyritic plutons. Pyrite is ubiquitous, ranging from ∼1 to >5 vol.%. Springs and headwater streams have pH values as low as 2.6, SO₄ up to 3700 mg/L and high dissolved metal concentrations (for example: Fe up to 400 mg/L; Cu up to 3.5 mg/L; and Zn up to 14.4 mg/L). Intensity of hydrothermal alteration and presence of sulfides are the primary controls of water chemistry of these naturally acidic waters. Subbasins underlain by intensely hydrothermally altered lithologies are poorly vegetated and quite susceptible to storm-induced surface runoff. Within the Red River study area, results from a storm runoff study documented downstream changes in river chemistry: pH decreased from 7.80 to 4.83, alkalinity decreased from 49.4 to <1 mg/L, SO₄ increased from 162 to 314 mg/L, dissolved Fe increased from to 0.011 to 0.596 mg/L, and dissolved Zn increased from 0.056 to 0.607 mg/L. Compared to mine drainage in the same study areas, the chemistry of naturally acidic waters tends to overlap but not reach the extreme concentrations of metals and acidity as some mine waters. The chemistry of waters draining these mineralized but unmined areas can be used to estimate premining conditions at sites with similar geologic and hydrologic conditions. For example, the US Geological Survey was asked to estimate premining ground-water chemistry at the Questa Mo mine, and the proximal analog approach was used because a mineralized but unmined area was located adjacent to the mine property. By comparing and contrasting water chemistry from different porphyry mineralized areas, this study not only documents the range in concentrations of constituents of interest but also provides insight into the primary controls of water chemistry.  相似文献   

Fractionation of the platinum-group elments and Re during crystallization of basalt in Kilauea Iki Lava Lake, Hawaii     

Lynnette Pitcher  Rosalind T. Helz  Richard J. Walker  Philip Piccoli 《Chemical Geology》2009,260(3-4):196-210

Kilauea Iki lava lake formed during the 1959 summit eruption of Kilauea Volcano, then crystallized and differentiated over a period of 35 years. It offers an opportunity to evaluate the fractionation behavior of trace elements in a uniquely well-documented basaltic system. A suite of 14 core samples recovered from 1967 to 1981 has been analyzed for 5 platinum-group elements (PGE: Ir, Os, Ru, Pt, Pd), plus Re. These samples have MgO ranging from 2.4 to 26.9 wt.%, with temperatures prior to quench ranging from 1140 °C to ambient (110 °C). Five eruption samples were also analyzed.Osmium and Ru concentrations vary by nearly four orders of magnitude (0.0006–1.40 ppb for Os and 0.0006–2.01 ppb for Ru) and are positively correlated with MgO content. These elements behaved compatibly during crystallization, mostly likely being concentrated in trace phases (alloy or sulfide) present in olivine phenocrysts or included chromite. Iridium also correlates positively with MgO, although less strongly than Os and Ru. The somewhat poorer correlation for Ir, compared with Os and Ru, may reflect variable loss of Ir as volatile IrF₆ in some of the most magnesian samples.Rhenium is negatively correlated with MgO, behaving as an incompatible trace element. Its behavior in the lava lake is complicated by apparent volatile loss of Re, as suggested by a decrease in Re concentration with time of quenching for lake samples vs. eruption samples. Platinum and Pd concentrations are negatively, albeit weakly, correlated with MgO, so these elements were modestly incompatible during crystallization of the major silicate phases. Palladium contents peaked before precipitation of immiscible sulfide liquid, however, and decline sharply in the most differentiated samples. In contrast, Pt appears to have been unaffected by sulfide precipitation. Microprobe data confirm that Pd entered the sulfide liquid before Re, and that Pt is not strongly chalcophile in this system. Occasional high Pt values in both eruption and lava lake samples suggest the presence of unevenly distributed, unidentified Pt-rich trace phases in some Kilauea Iki materials.Estimated mineral (olivine + chromite)/melt D values for Os, Ir, Ru and Pt for equilibrium crystallization for samples from ~ 7 to 27 wt.% MgO are 26, 8.2, 19 and 0.55, respectively. These Os, Ir and Ru estimates are somewhat higher than previous estimates for similar systems. If fractional crystallization is instead assumed, D values are much more similar.Results confirm many prior observations in other mafic systems that olivine (together with included phases) has a major effect on absolute and relative abundances of Re and the PGE. The relatively linear correlations between these elements and MgO potentially permit accurate estimation of the concentrations of these elements in the primary melts of comparable systems, especially in instances where the MgO content of the primary melt is well constrained.  相似文献   

Biodegradability of trimethylbenzene isomers under the strictly anaerobic conditions in groundwater contaminated by gasoline     

Yu Dao Chen  Lai Gui  James F. Barker  Yaping Jiang 《Environmental Geology》2009,56(6):1123-1128

Trimethylbenzene (TMB), as a constituent of gasoline, is often expected to be used as a conservative tracer in anaerobic BTEX-contaminated groundwater site to correct for attenuation due to dispersion, dilution and sorption along a flow path. To evaluate the suitability of using TMB as a tracer and to better understand biodegradability of TMB in contaminated groundwater by gasoline under anaerobic conditions, laboratory microcosms were conducted with mixed nitrate/iron/sulfate electron-acceptor amendments, using aquifer materials collected from Canadian Forces Base (CFB), Borden, Ontario, Canada. The results showed that under denitrifying conditions, biodegradation of 1,3,5-TMB, 1,2,4-TMB and 1,2,3-TMB were relatively slow and after 204 days of incubation approximately 27, 24, and 16% of the initial concentrations, respectively, were degraded in the microcosms. Under sulfate-reducing conditions, TMB isomers were recalcitrant. In contrast, significant biodegradation of TMB was observed under iron-reducing conditions. 1,3,5-TMB, 1,2,4-TMB and 1,2,3-TMB were degraded to 44, 47, and 24% of initial concentrations with first-order biodegradation rate constants of 0.003, 0.006 and 0.013 d⁻¹, respectively. This study indicates that TMB biodegradation is insignificant under nitrate and sulfate-reducing conditions but significant under iron-reducing conditions. Therefore, the use of TMB as a tracer for interpreting removal of other biodegradable gasoline constituents such as BTEX requires caution, especially in the presence of iron-reducing conditions.  相似文献   

Downwelling and upwelling regimes: Connections between surface fronts and abyssal circulation     

Carol Anne Clayson  Maria Luneva  Philip Cunningham   《Dynamics of Atmospheres and Oceans》2008,45(3-4):165

Recent observations in the Sea of Japan show evidence of convection to a depth of roughly 1000 m in the winter of 2000, situated along the polar front. Numerical simulations have shown that this deep mixing is associated with both ageostrophic frontal circulations and pre-existing larger-scale downwelling regimes. The downwelling regimes appear to be a result of interactions between frontal meandering and deep circulation in this basin over bottom topography anomalies. The coupling between the frontal dynamics and the deep circulation are explored by analogy to atmospheric frontal circulations through the semigeostrophic Sawyer–Eliassen equation, solved numerically for the case of the Sea of Japan. As in the atmospheric case, a vertical coupling between the upper and lower circulations can produce a localized region of downwelling that can be conducive to deeper mixing than that forced solely from surface fluxes.  相似文献   

MARCI and MOC observations of the atmosphere and surface cap in the north polar region of Mars     

Bruce A. Cantor  Philip B. James 《Icarus》2010,208(1):61-81

We used MGS-MOC and MRO-MARCI daily mapping images of the North Polar Region of Mars from 16 August 2005 (L_s = 270°) to 21 May 2009 (L_s = 270°), covering portions of three consecutive martian years (MY 27-MY 29), to observe the seasonal behavior of the polar ice cap and atmospheric phenomena. The rate of cap regression was similar in MY 28 and MY 29, but was advanced by 3.5° of L_s (∼7-8 sols) in MY 29. The spatial and temporal behaviors of dust and condensate clouds were similar in the two years and generally in accord with prior years. Dust storms (>100 km²) were observed in all seasons, with peak activity occurring at L_s = 10-20° from 50°N to 70°N and at L_s = 135-140° from 70°N to 90°N. The most active quadrant was 0-90°W in MY 28, shifting to 180-270°W in MY 29. The majority of regional storms in both years developed in longitudes from 10°W to 60°W. During late summer the larger storms obscure the North Polar Region in a cloud of dust that transitions to north polar hood condensate clouds around autumnal equinox.Changes in the distribution of perennial ice deposits, especially in Olympia Planum, were observed between the 2 years, with the MY 29 ice distribution being the most extensive observed to date. Modeling suggests that the small, bright ice patches on the residual cap are not the result of slope or elevation effects. Rather we suggest that they are the result of local meteorological effects on ice deposition. The annual darkening and brightening of peripheral areas of the residual cap around summer solstice can be explained by the sublimation of a brighter frost layer revealing an underlying darker, ice rich layer that itself either sublimes to reveal brighter material below or acts as a cold trap, attracting condensation of water vapor that brightens the surface. An alternative explanation invokes transport and deposition of dust on the surface from the cap interior, and later removal of that dust. The decrease in cap albedo and accompanying increase in near surface atmospheric stability may be related to the annual minimum of polar storm activity near northern summer solstice.  相似文献   

A 5 million year record of compositional variations in mantle sources to magmatism on Santiago, southern Cape Verde archipelago     

Abigail K. Barker  Paul M. Holm  David W. Peate  Joel A. Baker 《Contributions to Mineralogy and Petrology》2010,160(1):133-154

High-precision Pb isotope data and Sr–Nd–Hf isotope data are presented together with major and trace element data for samples spanning the 4.6 Ma history of volcanism at Santiago, in the southern Cape Verde islands. Pb isotope data confirm the positive Δ8/4 signature of the southern islands indicating that the north–south compositional heterogeneity in the Cape Verde archipelago has persisted for at least 4.6 Ma. The Santiago volcanics show distinct compositional differences between the old, intermediate and young volcanics, and suggest greater involvement of an enriched mantle (EM1)-like source over time. Isotopic variations in the Santiago volcanics indicate convergence towards a homogeneous EM1-like end-member and distinct temporal variations in the FOZO-like end-member. Santiago and Santo Antão (a northern island, Holm et al. 2006), show a simultaneous decrease in ²⁰⁸Pb/²⁰⁴Pb of the high ²⁰⁶Pb/²⁰⁴Pb FOZO-like source with time. Such systematic archipelago-wide variations in the FOZO-like component suggest that this component is more likely to be present as a coherent package of recycled ocean crust rather than as multiple small heterogeneities dispersed in the upwelling mantle. The temporal variations in ²⁰⁸Pb/²⁰⁴Pb reflect minor lateral variations in Th/U of this recycled ocean crust package entering the melting zone beneath the islands. The location of the EM1-like component is more equivocal. A shallow lithospheric location is possible, but this would require a coincidence between spatial compositional variations in the lithosphere (EM1 is spatially restricted to the southern islands) and flow lines in the upwelling mantle revealed by seismic anisotropy. Therefore, we favour a deeper asthenospheric mantle source for the EM1-like source.  相似文献