新疆准噶尔古生代洋盆闭合时限——来自卡拉麦里地区石炭纪碎屑锆石U-Pb年代学的约束

新疆准噶尔古生代洋盆闭合时限对中亚造山带古生代构造格局及演化研究具有重要意义。东准噶尔卡拉麦里断裂带南缘广泛出露石炭纪陆相粗碎屑岩系,沉积相分析表明其形成于扇三角洲沉积环境。依据区域地层对比、岩石组合特征及地层接触关系,将其重新厘定为山梁砾石组。选择西段滴水泉和东段双井子2个地区的山梁砾石组剖面进行地层对比,并在2个剖面底部采集粗砂岩样品进行LA-ICP-MS锆石U-Pb年龄测定,获得最年轻的碎屑锆石年龄分别为349±4Ma和355±3Ma,代表山梁砾石组沉积时代晚于349Ma,应为早石炭世早期。碎屑锆石年龄分布特征及砾石成分表明,其物源主要来自断裂带北侧的泥盆纪火山岩。在分析前人资料的基础上,认为山梁砾石组碎屑岩系是卡拉麦里造山带强烈隆升造山过程的沉积学响应,形成于前陆盆地,限定了准噶尔古生代洋盆闭合时限在早石炭世早期之前。     

Longitudinal and temporal patterns of benthic coarse particulate organic matter in the Agüera stream (northern Spain)

Benthic coarse particulate organic matter (CPOM) was studied between November 92 and December 93 at four sites along the longitudinal gradient of the Agüera stream system (Northern Spain). CPOM was sorted in four main categories: leaves (several species), fruits and seeds, twigs and debris. Headwater site showed higher densities of total CPOM, leaves and twigs than downstream reaches, but no regular longitudinal pattern of change was noticed. The ranges of mean CPOM standing stock at the sampling sites were 20.5–74.1 g AFDW m^–2 (site B), 9.9–47.7 g AFDW m^–2 (site 5), 4.3–21.4g AFDW m^–2 (site 7) and 9.8–37.9 g AFDW m^–2 (site 9). The particulate matter at downstream sites was in a more advanced stage of breakdown probably as a result of processing and transport from upstream reaches. Leaves species composition of benthic CPOM clearly reflected the type of riparian vegetation at each site. The timing of inputs and the hydrologic regime appeared to act together influencing temporal dynamics of benthic CPOM. A gradual temporal change in species composition of benthic leaf litter was observed under natural mature deciduous forest: first alder, later chestnut and finally oak.     

黄河宁蒙河段粗泥沙重矿物特征及其指示意义

近年来,黄河上游宁夏-内蒙古河段（简称宁蒙河段）河道淤积日益严重,辨识该河段的粗泥沙来源已成为该河段开发与治理的前提。重矿物耐磨蚀、稳定性强,能较多地保留其母岩的特征,因此常被用于物源示踪分析。对黄河宁蒙河段河道27个样品点的粗泥沙重矿物特征进行分析研究,表明该河段粗泥沙重矿物以性质不稳定的角闪石、较稳定的绿帘石、赤褐铁矿为主,稳定矿物除刚玉、钛铁矿外,锆石、金红石、黄铁矿、电气石含量极少。稳定系数法计算结果表明在河东沙地河段、乌兰布和沙漠河段以及十大孔兑河段之间稳定系数最低,几乎接近于0,说明在这3个地区河道粗泥沙源于附近沙源不同形式的汇入。本研究区ZTR指数极低,平均只有0.0071,说明黄河宁蒙河段泥沙重矿物成熟度低,淤积的泥沙并未经过长途的搬运堆积,而是来自当地沙源的汇入。相关系数法给出了3种不同性质的矿物组合类型,分别指示了不同的母岩类型和物源环境。     

焊接土工格栅土中锚固强度的影响因素

选择3种不同规格的焊接土工格栅,完成了格栅在粗颗粒土中的一系列拉拔试验。根据试验结果和土工格栅与土的相互作用机理,分析了各种格栅在土中的锚固强度及其影响因素。结果表明:在网格尺寸相同的情况下,节点剥离强度越大,则土中锚固强度越高;焊接土工格栅的节点剥离强度是其土中锚固强度的控制指标,但非唯一影响因素,网格尺寸和填土性质也对格栅土中锚固阻力的发挥具有重要影响。     

Downstream fining in contrasting reaches of the sand‐bedded Yellow River

Compared to downstream fining of a gravel‐bedded river, little field evidence exists to support the process of downstream fining in large, fine sand‐bedded rivers. In fact, the typically unimodal bed sediments of these rivers are thought to produce equal mobility of coarse and fine grains that may discourage downstream fining. To investigate this topic, we drilled 200 sediment cores in the channel beds of two fine‐grained sand‐bedded reaches of the Yellow River (a desert reach and a lower reach) and identified a fine surface layer (FSL) developed over a coarse subsurface layer (CSL) in the 3‐m‐thick bed deposits. In both reaches downstream, the thickness of the FSL increased, while that of the CSL decreased. Comparison of the depth‐averaged median grain sizes of the CSL and the FSL separately in both reaches shows a distinct downstream fining dependence to the median grain size, which indicates that at a large scale of 600‐800 km, the CSL shows a significant downstream fining, but the FSL shows no significant trends in downstream variations in grain size. This result shows that fine sediment supply (<0·08 mm median grain size) from upstream, combined with lateral fine sediment inputs from tributaries and bank erosion, can cause a rapid fining of the downstream channel bed surface and can develop the FSL layer. However, in the desert reach, lateral coarse sediment supply (>0·08 mm median grain size) from wind‐borne sediments and cross‐desert tributaries can interrupt the FSL and coarsen the channel bed surface locally. Copyright © 2011 John Wiley & Sons, Ltd.     

Moisture characteristics and their point pedotransfer functions for coarse‐textured tropical soils differing in structural degradation status

The effect of soil structure on hydraulic pedotransfer functions (PTFs) in tropical soils with similar mineralogy and texture has not been well documented. Structurally contrasting soils from representative locations in southeastern Nigeria were analyzed for moisture retention at 0, 6, 10, 33, 100, 300 and 1500 kPa among other properties. They were grouped by depth (topsoils or subsoils) and also by their structural degradation status into low‐ and high‐stability soils, corresponding to organic matter (OM):[silt + clay] of <7.5 and >7.5%, respectively. Soil depth and structural stability influenced the soil moisture characteristic curves. The data were fitted to three tropical point PTFs, but none of them proved appropriate for predicting moisture retention in the soils. We therefore derived new ones using multiple linear stepwise regressions before and after the dataset grouping and compared their performances by means of cross‐validation. Moisture retention in the soils (sand content, 73.2–93.8%) could not be calibrated from texture and OM concentration alone, until when bulk density, total porosity and microporosity were included among the regressors. Microporosity's role was particularly outstanding at all matric potentials but the 1500 kPa. The ensuing PTFs represent a good fit for the soil moisture retention data. The two grouping strategies resulted in lower SE of the estimates in some cases, but this did not enhance the performances of the concerned PTFs. At the 1500 kPa, however, the PTF incorporating all datasets performed better than separate PTFs for topsoils/subsoils but worse than the one for high‐stability soils. Information on soil structure can therefore benefit PTF derivation for kaolinite‐dominated, coarse‐textured tropical soils at all the matric potentials considered. Copyright © 2012 John Wiley & Sons, Ltd.     

青海省民和黄土的粒度组成及气候含义

对位于青藏高原东北缘的青海省民和黄土采样和粒度分析结果的研究表明，民和黄土的粒度远大于兰州等地黄土的粒度。民和黄土（粒径＞30μm和＞50μm的粗颗粒组分）分别指示了冬季风强度变化和青藏高原阶段性隆升所激发产生的黄土物源区作用。高原表面的寒冻风化物和冰碛物等给民和黄土提供了可观的粗物质补给。高原隆升以及其它区域性构造变动使黄土物源区呈现多样性特征。     

频域波动方程的多重网格法

针对差分法求解过程中细网格计算所需时间和空间要求高以及在粗网格上计算又达不到所要求的精度等问题，利用粗网格上的残差校正特性消除迭代误差的低频分量，同时利用细网格上的松弛光滑特性消除迭代误差的高频分量，采用不同疏密的网格距消除不同频率范围内的误差分量，将多重网格方法成功应用于频域波动方程的求解，并给出了实际算例。算例中，分别用Gauss-Seidel迭代法和多重网格法求其数值解，并绘出效果图；比较得出多重网格方法具有精度高、收敛速度快和易于实现的特性，更适合于高维波动问题的求解。     

Properties of coarse particles in suspended particulate matter of the North Yellow Sea during summer

Fine particles in seawater commonly form large porous aggregates. Aggregate density and settling velocity determine the behavior of this suspended particulate matter(SPM) within the water column.However, few studies of aggregate particles over a continental shelf have been undertaken. In our case study, properties of aggregate particles, including size and composition, over the continental shelf of the North Yellow Sea were investigated. During a scienti?c cruise in July 2016, in situ ef fective particle size distributions of SPM at 10 stations were measured, while temperature and turbidity measurements and samples of water were obtained from surface, middle, and bottom layers. Dispersed and inorganic particle size distributions were determined in the laboratory. The in situ SPM was divided into(1) small particles(<32 μm),(2) medium particles(32–256 μm) and(3) large particles(>256 μm). Large particles and medium particles dominated the total volume concentrations(VCs) of in situ SPM. After dispersion, the VCs of medium particles decreased to low values(<0.1 μL/L). The VCs of large particles in the surface and middle layers also decreased markedly, although they had higher peak values(0.1–1 μL/L). This suggests that almost all in situ medium particles and some large particles were aggregated, while other large particles were single particles. Correlation analysis showed that primary particles <32 μm in?uenced the formation of these aggregates. Microscopic examination revealed that these aggregates consisted of both organic and inorganic ?ne particles, while large particles were mucus-bound organic aggregates or individual plankton.The vertical distribution of coarser particles was clearly related to water strati?cation. Generally, medium aggregate particles were dominant in SPM of the bottom layer. A thermocline blocked resuspension of?ne material into upper layers, yielding low VCs of medium-sized aggregate particles in the surface layer.Abundant large biogenic particles were present in both surface and middle layers.