RECORD OF BLOCK ROTATION AND MAGNETIC FIELD REVERSALS IN THE TETHYAN HIMALAYA (HIDDEN VALLEY, CENTRAL NEPAL)

RECORD OF BLOCK ROTATION AND MAGNETIC FIELD REVERSALS IN THE TETHYAN HIMALAYA (HIDDEN VALLEY, CENTRAL NEPAL)     

A PRELIMINARY REPORT OF ARCHAEOLOGICAL INVESTIGATIONS ON THE SINO-TIBETAN BORDER OF SZECHWAN§

INTRODUCTION During the year 1930-31, while holding a schularship from the Harvard-Yenching Institute, I received permission from the Institute to engage in ethnological and anthropological research on behalf of the University Museum     

广西百朗地下河水和沉积物中有机氯农药的分布特征

为了解典型岩溶地区广西乐业百朗地下河表层水和沉积物中有机氯农药的分布特征,采集地下河不同断面的水和沉积物样品,利用气相色谱仪测定了19种有机氯农药。结果表明:(1)百朗地下河表层水中19种有机氯农药总量(∑OCPs)浓度为1.95～71.45ng/L,HCHs和DDTs浓度分别为未检出至58.40ng/L和未检出至0.44ng/L;(2)沉积物中∑OCPs浓度为0.75～14.85ng/g,HCHs和DDTs浓度分别为0.11～3.52ng/g和0.03～2.90ng/g;(3)地下河表层水和沉积物中有机氯农药的分布与吸附作用、环境温度以及和地下河连通的天坑的底部的土壤侵蚀有关,即因温差作用,大气沉降的有机氯农药易富集在天坑底部(“冷陷阱效应”),并在土壤侵蚀作用下向水体移动,使地下河沉积物中有机氯农药浓度升高;(4)百朗地下河出口沉积物吸附系数最低,但水中有机氯农药浓度较高且种类最多,推测可能是地下河沉积物中因有机氯农药被释放而引起二次污染;(5)表层沉积物中大多数断面的异狄氏剂浓度及乐业县城附近断面的DDTs和DDD浓度在风险评估低值与风险评估中值之间,表明百朗地下河处于较低的生态风险水平;(6)目前,流域部分断面尚有新的γ-HCH(林丹)和DDTs农药输入。由于有机氯农药长期累积,可能对地下河生态系统造成危害,应采取防治措施。      

钻孔应变仪的固体潮标定——消除小尺度不均匀性的影响

通过对Pion Flat观测点的Gladwin钻孔张量应变仪(BTSM)进行固体潮标定得到的应变数据,我们对地应变进行了估算并分析。小尺度地质上的不均匀性是通过远场面应变/剪应变的交互耦合方法考察面应变/剪应变时所要考虑的因素之一。一种将交互耦合引入应变仪标定的方法由此而生。以同一位置激光应变仪(LSM)观测的固体潮应变为参考,我们发现用交互耦合方法对BTSM标定消除了钻孔固体潮观测值应变中近30%的系统误差。这种标定将钻孔应变和激光应变的测量精度(大约1km)准确地联系在一起了。这种标定技术为短基线应变测量中面临的主要问题(构造应变不能表征小尺度的非均匀性)提供了解决方法。这种方法在断层滑移的残余应变测量中可能减少50%甚至更高的误差,并允许增加滑移机制的约束条件。我们发现就目前仪器而得出的固体潮应变的理论估计值来进行交互耦合标定还不够精确。将理论固体潮与激光应变仪(LSM)观测的固体潮进行比照发现,至少有一半的误差产生于对海洋负荷潮的估计。     

Heavy metal concentrations in soils and plants in the vicinity of Arufu lead-zinc mine,Middle Benue Trough,Nigeria

This study focused on the influence of base metal mining on heavy metal levels in soils and plants in the vicinity of Arufu lead-zinc mine, Nigeria. Soil samples (0-15 cm depth) and plant samples were collected from cul-tivated farmlands in and around the mine, the unmineralized site and a nearby forest (the control site). The samples were analyzed for heavy metals (Fe, Zn, Mn, Cu, Pb, Cr and Cd) by Atomic Absorption Spectrophotometry (AAS). The physical properties of soils (pH and LOI) were also measured. Results showed that soils from cultivated farm-lands have neutral pH values (6.5-7.5), and low organic matter contents (10%). Levels of Zn, Pb and Cd in culti-vated soils were higher than the concentrations obtained from the control site. These heavy metals are most probably sourced from mining and agricultural activities in the study area. Heavy metal concentrations measured in plant parts decreased in the order of rice leavescassava tuberspeelings. In the same plant species, metal levels decreased in the order of ZnFeMnCuPbCrCd. Most heavy metals were found in plant parts at average concentrations normally observed in plants grown in uncontaminated soil, however, elevated concentrations of Pb and Cd were found in a few cassava samples close to the mine dump. A stepwise linear regression analysis identified soil metal contents, pH and LOI as some of the factors influencing soil-plant metal uptake.     

Application of soft computing techniques for shallow foundation reliability in geotechnical engineering

This research focuses on the application of three soft computing techniques including Minimax Probability Machine Regression(MPMR),Particle Swarm Optimization based Artificial Neural Network(ANN-PSO)and Particle Swarm Optimization based Adaptive Network Fuzzy Inference System(ANFIS-PSO)to study the shallow foundation reliability based on settlement criteria.Soil is a heterogeneous medium and the involvement of its attributes for geotechnical behaviour in soil-foundation system makes the prediction of settlement of shallow a complex engineering problem.This study explores the feasibility of soft computing techniques against the deterministic approach.The settlement of shallow foundation depends on the parametersγ(unit weight),e0(void ratio)and CC(compression index).These soil parameters are taken as input variables while the settlement of shallow foundation as output.To assess the performance of models,different performance indices i.e.RMSE,VAF,R^2,Bias Factor,MAPE,LMI,U(95),RSR,NS,RPD,etc.were used.From the analysis of results,it was found that MPMR model outperformed PSO-ANFIS and PSO-ANN.Therefore,MPMR can be used as a reliable soft computing technique for non-linear problems for settlement of shallow foundations on soils.     

Improved prediction of clay soil expansion using machine learning algorithms and meta-heuristic dichotomous ensemble classifiers

Soil swelling-related disaster is considered as one of the most devastating geo-hazards in modern history.Hence,proper determination of a soil’s ability to expand is very vital for achieving a secure and safe ground for infrastructures.Accordingly,this study has provided a novel and intelligent approach that enables an improved estimation of swelling by using kernelised machines(Bayesian linear regression(BLR)&bayes point machine(BPM)support vector machine(SVM)and deep-support vector machine(D-SVM));(multiple linear regressor(REG),logistic regressor(LR)and artificial neural network(ANN)),tree-based algorithms such as decision forest(RDF)&boosted trees(BDT).Also,and for the first time,meta-heuristic classifiers incorporating the techniques of voting(VE)and stacking(SE)were utilised.Different independent scenarios of explanatory features’combination that influence soil behaviour in swelling were investigated.Preliminary results indicated BLR as possessing the highest amount of deviation from the predictor variable(the actual swell-strain).REG and BLR performed slightly better than ANN while the meta-heuristic learners(VE and SE)produced the best overall performance(greatest R2 value of 0.94 and RMSE of 0.06%exhibited by VE).CEC,plasticity index and moisture content were the features considered to have the highest level of importance.Kernelized binary classifiers(SVM,D-SVM and BPM)gave better accuracy(average accuracy and recall rate of 0.93 and 0.60)compared to ANN,LR and RDF.Sensitivity-driven diagnostic test indicated that the meta-heuristic models’best performance occurred when ML training was conducted using k-fold validation technique.Finally,it is recommended that the concepts developed herein be deployed during the preliminary phases of a geotechnical or geological site characterisation by using the best performing meta-heuristic models via their background coding resource.     

Geochronology and Geochemistry of the Magmatic Rocks from Zedong Ophiolite, Eastern Yarlung-Zangbo Suture Zone, Tibet

The Yarlung Zangbo suture zone extends more than2000 km along southern Tibet and marks the boundary between the Indian subcontinent and Eurasia.The Zedong terrane has been not suggested to represent the vestige of such an intra-oceanic arc developed within the Neo-Tethys Ocean,as a result of the northward subduction of the Neo-Tethys Ocean during the Late Jurassic.In this study,we present detailed geochemical and geochronological data of various types of magmatic rocks widely exposed in the Zedong terrane to constrain the formation age and tectonic setting of the Zedong terrane.We found that the Zedong volcanic rocks belong to high K2O calc-alkaline series,whereas the diabase and gabbro plotted in the low-K calcalkline.The basalt rocks are highly enriched in LREE and LILE,but strongly depleted in HFSE,indicating they were derived from a metasomatized mantle.Both gabbros and diabase have similar N-MORB geochemistry indicates that the cumulates were produced from MOR setting.Zircons from four samples,including the basalt rocks(158-161Ma)are older than the gabbro(131 Ma),certificate the gabbro are as the vein intrude into the basalt rocks.This suggests that the volcanic eruption and plutonic emplacement were coevally developed in the Zedonghave similar positiveεHf(t)values(+2.0 to+15.6)and(+8.6 to+18.4),indicating they were stemmed from similarly depleted mantle sources,same with the gabbro and granitic rocks from the Gangdese arc.Therefore,we proposed that the basalt rocks in the Zedong terrane were formed through partial melting of the mantle wedge metasomatized by slab-released fluids/melts.A part of hydrous basalts were underplated in the thickened lower crust beneath the Zedong terrane,which gave rise to the cumulate and granitic rocks.This suggests that the Zedong terrane represents a slice of the active continental margin developed on the southern margin of the Lhasa terrane as a result of the northward subduction of the Neo-Tethys Ocean during the Late Jurassic,although a possible intra-oceanic arc setting cannot be excluded.