Preliminary Estimation of Paleoproductivity via TOC and Habitat Types： Which Method Is More Reliable？ -A Case Study on the Ordovician-Silurian Transitional Black Shales of the Upper Yangtze Platform, South China     

苏文博  王永标  Bradley  D  Cramer  AxelMunnecke  李志明  傅力浦 《中国地质大学学报(英文版)》2008,19(5):534-548

New total organic carbon (TOC) data from the two Ordovician-Silurian transitional graptolite-bearing black shale intervals, the Wnfeng (五峰) Formation and the Longmaxi (龙马溪) Formation in Central Guizhou (贵州) and West Hubei (湖北), respectively, as well as previously reported TOC data from the same intervals in other places on the Yangtze platform of South China, have been used to produce an initial estimate of the primary paleoproductivity via a conventional inverse method (i.e., Rpp-inverse). The values of the Rpp-inverse are estimated to be 32 (43-21) gC/(m2·a) (Wufeng Formation) and 21 (27-16) gC/(m2·a) (Longmaxi Formation). Also, simultaneously, the habitat types (i.e., HT; cf., BA: benthic assemblage) and their temporal and spatial changes have been documented from the same succession, and an initial estimate of the primary paleoproductivity has been produced using a forward method (i.e., Rpp.forward). Being bounded mainly by the peritidai to inner-shelf environment shelly-facies or mixed-facies successions with BAI to BA3 faunas both at the top and the base, which indicates the habitat types from HT Ⅱ1 to HT Ⅲ2, the biohabitat type of the two graptolite-bearing black shale intervals can be limited to HT Ⅲ to HT Ⅳ, corresponding to the inner shelf to the outer shelf, with depths from roughly 60 m to 200-300 m. Based on the current data from the South China Sea and the southern part of the East China Sea, values of Rpp-forward should be about 100 to 400 gC/(m2·a). The difference in the results via the two methods suggests that paleoproductivity estimates from the geological strata need to be made cautiously, with particular attention paid to the paleogeographic setting, oxic-anoxic conditions, as also the preservation factor of organic carbon.  相似文献   

Refinement of Phosphorus Determination in Quartz by LA‐ICP‐MS through Defining New Reference Material Values     

Axel Müller  Michael Wiedenbeck  Belinda Flem  Henrik Schiellerup 《Geostandards and Geoanalytical Research》2008,32(3):361-376

The aim of this study was to improve the quality of laser ablation inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) determination of phosphorus in crystalline quartz. Over the last decade, the Geological Survey of Norway has routinely performed trace element determinations on quartz from both operating and potential quartz deposits by LA‐ICP‐MS. The determined phosphorus concentrations were, with but few exceptions, consistently within the range of 10 to 30 μg g^?1, results that seemed to be both too high and too consistent. The multi‐material calibration curve obtained from a suite of reference materials (NIST SRM 610, 612, 614, 1830, BAM No. 1 amorphous SiO₂ glass) did not define a precise regression line. Published phosphorus concentrations for the reference materials are poorly constrained and the observed dispersions along the multi‐material calibration curve suggest that some of the reference values may be inaccurate. Furthermore, the calibration curve did not pass through the origin of the [(cps ³¹P/cps ³⁰Si) · cone. Si] vs. P concentration diagram; thus, in addition to the uncertainties of the literature values of phosphorus, it is difficult to define the calibration curve. Three reference materials (NIST SRM 614, 1830, synthetic quartz KORTH) were sent for phosphorus accelerator implantation, providing an independent and accurate (± 3%) approach for determining phosphorus concentrations in crystalline quartz. The intrinsic phosphorus concentrations of the three implanted samples plus those for NIST SRM 610 and 612 were determined by secondary ion mass spectrometry (SIMS), yielding new phosphorus values for NIST SRM 610, 612, 614 and 1830. Using these new values resulted in a better defined LA‐ICP‐MS calibration curve. However, the source of the ICP‐MS related background could not be defined, such that it must still be empirically corrected for.  相似文献   

On the relation between the synodic and sidereal rotation period of the Sun     

Axel D. Wittmann 《Solar physics》1996,168(1):211-213

It is pointed out that by taking Kepler's second law into account, the sidereal correction, i.e., the correction to be added to the observed synodic rotation rate of the Sun in order to get the sidereal rate, can be calculated more directly than described in a recent paper by Roa et al. (1995).  相似文献   

CCD-Doppler measurements of solar differential rotation     

Axel D. Wittmann 《Solar physics》1996,167(1-2):441-444

Using the AT1 CCD camera at the Echelle spectrograph of the GCT at Tenerife, solar Doppler rotation measurements in the photospheric lines Fe I 6301.5 Å and 6302.5 Å and in the chromospheric line Na-D₂ 5890.0 Å have been made. The line shifts measured at different heliographic latitudes around the limb were corrected for observer motion and converted into sidereal rotation rates. At the equator the observed chromospheric rotation rate is about 8 % larger than the photospheric rate, and the average observed Doppler rotation rate is not very much different from the mean rotation rates deduced from all published tracer works and all published Doppler works. Near the poles (where tracer methods rely on extrapolation) both the chromospheric and the photospheric rotation rate are slightly smaller than the all Doppler rate and are considerably smaller than the extrapolated all tracer rate. If all previous measurements of solar rotation are taken into account, a surface rotation law with lower error bounds than previously possible can be derived.  相似文献   

Population growth and urbanization in Latin America     

Axel Borsdorf 《GeoJournal》1991,2(1):47-60

The population of Latin America will be increasing by 130 % between 1970 and the year 2000. Due to excessive rural exodus the urban population grows almost twice as fast as the rural does. The urbanization of the subcontinent must be regarded as being the dominant spatial process in Latin America. It results in fundamental changes of the structure and the way of life of the population as well as in the size and character of the settlements.Three case studies (Popayán/Colombia, Sucre/Bolivia and Santiago/Chile) show that a process of westernization can be observed within the analogous to their size, in the course of which the compact structure of the colonial town pattern is succeeded by a sectorially or cellularly arranged cityorganism.From today's point of view a definite judgement on urbanization as a relevant phenomenon of development cannot yet be made. It can be stated, however, that the southern countries of Latin America which have been urbanized the most show distinct signs of a social and economic take off.  相似文献   

Comparison of stomach contents of haddock (Melanogrammus aeglefinus) from the 1981 and 1991 North Sea International Stomach Sampling Projects     

Adlerstein  Sara A.; Temming  Axel; Mergardt  Nils 《ICES Journal of Marine Science》2002,59(3):497-515

  相似文献   

The REBENT monitoring network, a spatially integrated, acoustic approach to surveying nearshore macrobenthic habitats: application to the Bay of Concarneau (South Brittany, France)     

Ehrhold  Axel; Hamon  Dominique; Guillaumont  Brigitte 《ICES Journal of Marine Science》2006,63(9):1604-1615

  相似文献   

Textural evidence of magma decompression, devolatilization and disequilibrium quenching: an example from the Western Krušné hory/Erzgebirge granite pluton     

Miroslav Štemprok  David Dolejš  Axel Müller  Reimar Seltmann 《Contributions to Mineralogy and Petrology》2008,155(1):93-109

We report new occurrences of “two-phase” granitic textures from the Western Krušné hory/Erzgebirge pluton (central Europe) and use crystal-size distribution data and thermodynamic modeling to interpret their crystallization conditions. The two-phase texture consists of (1) early phenocrysts of quartz, plagioclase, K-feldspar and biotite, (2) medium-grained matrix of the same phases and (3) interstitial channels and patches of a late-stage, very fine-grained matrix. The porphyritic two-mica microgranites, which host two-phase textures, occur as minor intrusions in early low-F biotite granites or as marginal parts of evolved high-F Li-mica granites. Measurements of the crystal-size distribution of quartz revealed three grain populations: (1) early phenocrysts (0.5–3.0 mm) showing partial resorption by residual melt, (2) a medium-grained population of the equigranular rock matrix (0.05–0.50 mm) that experienced minor coarsening by subsolidus annealing and (3) a fine-grained population (<0.03 mm) in the interstitial channels and patches formed during rapid devolatilization; this quartz group shows no or poor grain coarsening. All samples exhibit similar fraction of the fine-grained population (44–52%) but proportions of phenocrysts to medium-grained matrix vary significantly. Thermodynamic modeling of liquidus equilibria and experimental data in the hydrous haplogranite system require: (1) ascent of a granitic suspension (15–25% phenocrysts) under H₂O-undersaturated conditions at 25–45 bar/°C and a cooling rate of 40 J/(g kbar) in order to produce partial resorption of quartz phenocrysts and continued growth of feldspar phenocrysts, followed by (2) emplacement as discrete intrusions or bodies along pluton roof accompanied by sudden devolatilization. At the onset of matrix nucleation, disequilibrium undercooling of 70–85°C was inferred from the presence of micrographic intergrowths of quartz and K-feldspar. The two-phase granites in the Western Krušné hory/Erzgebirge pluton and in the Southeast Asian batholith form compositionally narrow groups with high-silica and moderate volatile enrichments but they differ in peraluminosity and phosphorus concentrations. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

The impact of errors in polar motion and nutation on UT1 determinations from VLBI Intensive observations   总被引：2，自引：2，他引：0  

Axel Nothnagel  Dorothee Schnell 《Journal of Geodesy》2008,82(12):863-869

The earth’s phase of rotation, expressed as Universal Time UT1, is the most variable component of the earth’s rotation. Continuous monitoring of this quantity is realised through daily single-baseline VLBI observations which are interleaved with VLBI network observations. The accuracy of these single-baseline observations is established mainly through statistically determined standard deviations of the adjustment process although the results of these measurements are prone to systematic errors. The two major effects are caused by inaccuracies in the polar motion and nutation angles introduced as a priori values which propagate into the UT1 results. In this paper, we analyse the transfer of these components into UT1 depending on the two VLBI baselines being used for short duration UT1 monitoring. We develop transfer functions of the errors in polar motion and nutation into the UT1 estimates. Maximum values reach 30 [μs per milliarcsecond] which is quite large considering that observations of nutation offsets w.r.t. the state-of-the-art nutation model show deviations of as much as one milliarcsecond.  相似文献   

Predictors of national CO2 emissions: do international commitments matter?     

Axel Franzen  Sebastian Mader 《Climatic change》2016,138(3-4):491-504

  相似文献