Characterization of coal maceral concentrates by curie-point pyrolysis mass spectrometry

A set of 30 maceral concentrates consisting of 5 exinites (sporinites), 14 vitrinites and 11 inertinites (fusinites and semifusinites) was analyzed by Curie-point pyrolysis mass spectrometry in combination with computerized multivariate statistical analysis techniques. Seventeen samples, representing sink/flotation concentrates of 7 different coals, were obtained through the British National Coal Board, whereas the remaining samples represent cesium-chloride density-gradient centrifugation fractions of two different U.S. coals prepared at the University of Utah.It is found that vitrinites, (semi)fusinites and, to some extent, sporinites show qualitatively similar rank-related changes, such as a decrease in dihydroxybenzene signals and an increase in napthalene signals with increasing rank. In fact, the overall pyrolysis MS patterns of inertinities show a close similarity to those of vitrinites of corresponding carbon content (as obtained from higher rank coals).Notwithstanding these similarities, however, the presence of basic differences in maceral structure is indicated by relatively minor but characteristic peak series in the liptinite (sporinite) as well as inertinite samples. Whereas inertinite spectra show relatively pronounced peak series at the high mass end of the spectrum which can be tentatively identified as representative of polynuclear aromatic compounds, sporinites are characterized by series of branched aliphatic and/or alicyclic polyenic hydrocarbons, possibly representing isoprenoids and related biomarker compounds.     

Assessment of a shell bank and associated substrates as nursery habitat of postsettlement red snapper

Trawl surveys were conducted in 2000 and 2001 to examine patterns of distribution and abundance of postsettlement red snapper (Lutjanus campechanus) on a shell bank, Freeport Rocks Bathymetric High (FRBH), in the northwestern Gulf of Mexico. In addition, otolith-based methods were used to determine age, hatch-date, growth and mortality of new recruits associated with FRBH. Date and region were significant factors affecting density of red snapper in 2000. Peak densities of red snapper were observed in July and August, and mean density among habitat types (shell bank, inshore mud, offshore mud) was similar (range: 50–52 ind hectare⁻¹) in 2000. Alternatively, a habitat effect was detected during a limited survey conducted in 2001, with density higher on the shell bank than inshore or offshore mud habitat. Postsettlement red snapper were first detected at approximately 16 mm standard length, and individuals less than 20 mm were present in all habitats. Estimated ages of red snapper ranged from 26 to 121 d, with new settlers (≤20 mm) typically less than 28 d. Predicted hatch dates ranged from early April to mid August with a single peak occurring from late May to early June. Growth rate for the April–May cohort (0.817 mm d⁻¹) was similar to the June–July cohort (0.830 mm d⁻¹). Habitat-specific differences in growth were observed, and rates were highest for individuals from the inshore habitat (0.881 mm d⁻¹). Mortality rates (Z) during the early post-settlement period were approximated using catch curves, and early life mortality of red snapper was 12.1% d⁻¹ (Z=0.129). While the difference in mortality between cohorts was negligible, a habitat-specific difference in mortality was observed. Mortality rate of red snapper inhabiting the inshore mud habitat (Z=0.045, 4.4% d⁻¹) was lower than rates observed for individuals on the shell bank (Z=0.120, 11.9% d⁻¹) or offshore (Z=0.099, 9.3% d⁻¹) habitat. Individuals residing in the inshore habitat had significantly higher growth rates and significantly lower mortality rates, suggesting that recruitment potential was higher for these individuals.     

The accuracy of surface elevations in forward global barotropic and baroclinic tide models

This paper examines the accuracy of surface elevations in a forward global numerical model of 10 tidal constituents. Both one-layer and two-layer simulations are performed. As far as the authors are aware, the two-layer simulations and the simulations in a companion paper (Deep-Sea Research II, 51 (2004) 3043) represent the first published global numerical solutions for baroclinic tides. Self-consistent forward solutions for the global tide are achieved with a convergent iteration procedure for the self-attraction and loading term. Energies are too large, and elevation accuracies are poor, unless substantial abyssal drag is present. Reasonably accurate tidal elevations can be obtained with a spatially uniform bulk drag c_d or horizontal viscosity K_H, but only if these are inordinately large. More plausible schemes concentrate drag over rough topography. The topographic drag scheme used here is based on an exact analytical solution for arbitrary small-amplitude terrain, and supplemented by dimensional analysis to account for drag due to flow-splitting and low-level turbulence as well as that due to breaking of radiating waves. The scheme is augmented by a multiplicative factor tuned to minimize elevation discrepancies with respect to the TOPEX/POSEIDON (T/P)-constrained GOT99.2 model. The multiplicative factor may account for undersampled small spatial scales in bathymetric datasets. An optimally tuned multi-constituent one-layer simulation has an RMS elevation discrepancy of 9.54 cm with respect to GOT99.2, in waters deeper than 1000 m and over latitudes covered by T/P (66N to 66S). The surface elevation discrepancy decreases to 8.90 cm (92 percent of the height variance captured) in the optimally tuned two-layer solution. The improvement in accuracy is not due to the direct surface elevation signature of internal tides, which is of small amplitude, but to a shift in the barotropic tide induced by baroclinicity. Elevations are also more accurate in the two-layer model when pelagic tide gauges are used as the benchmark, and when the T/P-constrained TPXO6.2 model is used as a benchmark in deep waters south of 66S. For Antarctic diurnal tides, the improvement in forward model elevation accuracy with baroclinicity is substantial. The optimal multiplicative factor in the two-layer case is nearly the same as in the one-layer case, against initial expectations that the explicit resolution of low-mode conversion would allow less parameterized drag. In the optimally tuned two-layer M₂ solution, local values of the ratio of temporally averaged squared upper layer speed to squared lower layer speed often exceed 10.     

Chemical depletion of sediment under the Greenland Ice Sheet

The chemical composition of sediment sampled from a network of ice boreholes contacting the bed of the ablation zone of the Greenland Ice Sheet is compared to the composition of intact bedrock clasts. This sediment is enriched in silica and depleted in reactive cations compared to the underlying bedrock. In order to test whether these differences result from grain size biases either in sample collection or due to natural sorting, sediment samples were analyzed by grain size aliquots. Enrichment of silicon and depletion of cations is consistent across grain size classes and the compositions of bedrock and subglacial sediment are statistically separate. The difference in composition between subglacial sediment and rock aligns closely with the composition of dissolved solutes in waters sampled from the same field sites and is dissimilar to the composition of the sites' suspended sediment. This implies that chemical weathering rather than disproportionate physical removal of friable minerals is responsible for the compositional differences between rock and sediment. Mass balance analysis implies 3–10% of the sediment's mass is lost to solute dissolution, with approximately double that amount precipitated as clay minerals (a large portion of which may have been physically expelled). This result implies that temperate ice sheet subglacial environments may be more chemically active than previously realized. Copyright © 2016 John Wiley & Sons, Ltd.     

Coordinated Ocean-ice Reference Experiments (COREs)

Coordinated Ocean-ice Reference Experiments (COREs) are presented as a tool to explore the behaviour of global ocean-ice models under forcing from a common atmospheric dataset. We highlight issues arising when designing coupled global ocean and sea ice experiments, such as difficulties formulating a consistent forcing methodology and experimental protocol. Particular focus is given to the hydrological forcing, the details of which are key to realizing simulations with stable meridional overturning circulations.The atmospheric forcing from [Large, W., Yeager, S., 2004. Diurnal to decadal global forcing for ocean and sea-ice models: the data sets and flux climatologies. NCAR Technical Note: NCAR/TN-460+STR. CGD Division of the National Center for Atmospheric Research] was developed for coupled-ocean and sea ice models. We found it to be suitable for our purposes, even though its evaluation originally focussed more on the ocean than on the sea-ice. Simulations with this atmospheric forcing are presented from seven global ocean-ice models using the CORE-I design (repeating annual cycle of atmospheric forcing for 500 years). These simulations test the hypothesis that global ocean-ice models run under the same atmospheric state produce qualitatively similar simulations. The validity of this hypothesis is shown to depend on the chosen diagnostic. The CORE simulations provide feedback to the fidelity of the atmospheric forcing and model configuration, with identification of biases promoting avenues for forcing dataset and/or model development.     

关于奥陶系最上部赫南特(Hirnantian)亚阶全球层型的建议

在对鄂西宜昌王家湾和分乡、黔北桐梓红花园、黔东北松桃陆地坪 4条剖面的相关地层和主要门类化石做了新的无间断采集和重新鉴定笔石和腕足动物这两个重要化石门类的基础上 ,发现奥陶纪最末期—志留纪最早期的完整笔石序列与腕足动物等新的化石材料 ,初步了解奥陶纪末集群灭绝后生物幸存的基本特征。经过选择 ,特推荐宜昌王家湾公路旁穿越奥陶 -志留纪界线地层剖面作为建立国际赫南特亚阶的首位候选 (leading candidate)层型 ,并推荐桐梓红花园相关剖面作为辅助候选 (auxiliary candidate)层型。对建立全球赫南特亚阶界线层型的基本条件和国外相关剖面的优缺点作了分析。本文所识别的赫南特亚阶相当于两个笔石带 :下部 N ormalograptus ex-traordinarius- N.ojsuensis带和上部 N.persculptus带。典型的 H irnantia动物群的整体地质历程为奥陶纪最末期 ,相当于 N ormalograptus extraordinarius- N.ojsuensis带和 N.persculptus带的一部分。     

奥陶系上统赫南特阶全球层型剖面和点位的建立

赫南特阶(上奥陶统)的全球界线层型剖面和点位确立在中国宜昌王家湾北剖面观音桥层底界之下0.39m处。该剖面位于中国湖北省宜昌市以北42km处的王家湾村,经纬度为30°58′56″N、111°25′10″E。赫南特阶底界的GSSP点位以笔石Normalograptusextraordinarius的首次出现层位(FAD)为标志。碳同位素在此层位显示的正漂移以及N.ojsuensis的首现可作为第二标志。赫南特阶始于自Diceratograptusmirus亚带开始的全球生物大灭绝事件的主幕之后。王家湾北剖面出露完整,沉积和生物序列连续,笔石和壳相动物化石丰富并保存良好,王家湾北、王家湾南和王家湾小河边剖面都发育了合适的沉积相和生物相并具有广泛对比的潜力。该地区地质构造简单,岩石未经历较强的变质作用,且交通便利。王家湾小河边剖面尤其适合进行化学地层学研究和同位素年龄的测定。建立赫南特阶底界的全球界线层型剖面和点位的提案报告于2004年10月被国际地层委员会奥陶系分会通过,经补充完善后,于2006年2月被国际地层委员会通过,同年5月被国际地科联正式批准。