Factors Influencing Variability in Groundwater Monitoring Data Sets     

T.E. McHugh  L.M. Beckley  C.Y. Liu  C.J. Newell 《Ground Water Monitoring & Remediation》2011,31(2):92-101

“Random” variability in groundwater monitoring data sets reduces the ability to identify long‐term concentration trends. This, in turn, increases the time and cost required to evaluate the effectiveness of natural attenuation and other groundwater remedies. To better understand the factors influencing variability in groundwater monitoring results, we have analyzed three large groundwater monitoring data sets. For the three data sets, the long‐term trend in contaminant concentration in each well accounted for an average of 30% to 40% of the overall variation in contaminant concentration. Understanding the causes of the remaining variability would support the development of improved groundwater monitoring methods. All three data sets show large differences in the temporal monitoring records between individual wells (e.g., coefficient of variation for monitoring results from individual wells ranges from 0.08 to 4.6) indicating that well and aquifer factors are more important contributors to variability than sample collection and analysis factors. However, the depth to groundwater (R² = 0.020) and distance between water level and screened interval (R² = 0.049) accounted for only a portion of the differences in variability between wells and other aquifer characteristics evaluated and were not correlated with the observed variability in monitoring results. Unidentified factors were apparently much more important contributors to variability than these factors. The monitoring data sets exhibited two distinct timescales for variability: Time‐independent variability that was apparent even when wells were re‐sampled within a few days and a long‐term variability likely associated with the long‐term concentration trend. The observation of time‐independent variability suggests that frequent monitoring of contaminated monitoring wells serves primarily to characterize sources of variability unrelated to the long‐term trend of primary interest.  相似文献   

Timing of basin inversion on the Isle of Wight: New evidence from geophysical log correlation, seismic sections and lateral facies change in the Palaeogene Headon Hill Formation     

Andrew J. Newell  David J. Evans 《Proceedings of the Geologists' Association. Geologists' Association》2011,122(5):868-882

Paleogene thickness patterns across the Bouldnor Syncline and Porchfield Anticline in the northwestern Isle of Wight have been deduced using outcrop information, borehole correlation, gamma-ray logs and seismic reflection data. The thickness patterns provide evidence for an early phase of basin inversion at around the Bartonian-Priabonian boundary (Late Eocene) in the Isle of Wight. Paleogene strata older than the Becton Sand Formation show little evidence for significant lateral changes in thickness, even though the boreholes are located at various structural positions around the Bouldnor Syncline and Porchfield Anticline. In contrast, both seismic reflection and borehole data provide evidence for marked thinning of Paleogene strata onto the Porchfield Anticline at around the level of the Becton Sand Formation and basal Headon Hill Formation (Totland Bay Member) which probably results from an episode of basin inversion and growth folding. The inversion event was relatively minor and short-lived and continues to point toward the main phase of the basin inversion being late Oligocene or younger. However, it still has important implications for understanding structural control on sedimentation patterns in the Headon Hill Formation, with the migration of sandy channelised depositional systems into the axis of the Bouldnor Syncline, and the sequence stratigraphic significance of the important Bartonian-Priabonian regression event, which may related to tectonics rather than global sea-level change.  相似文献   

Contaminant plume classification system based on mass discharge   总被引：1，自引：0，他引：1  

Newell CJ  Farhat SK  Adamson DT  Looney BB 《Ground water》2011,49(6):914-919

Estimation of mass discharge has become an increasingly valuable analysis technique at sites with contaminated groundwater plumes. We propose a simple plume magnitude classification system based on mass discharge comprised of 10 separate magnitude categories, such as a "Mag 7 plume." This system can be a useful tool for scientists, engineers, regulators, and stakeholders to better communicate site conceptual models, prioritize sites, evaluate plumes both spatially and temporally, and determine potential impacts.  相似文献   

Chalk thickness trends and the role of tectonic processes in the Upper Cretaceous of southern England     

Andrew J. Newell  Mark A. Woods  Andrew R. Farrant  Helen Smith  Richard B. Haslam 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(5):610-628

A series of six thickness maps created at a formation scale for the Chalk of the Southern and Transitional Chalk provinces of SE England reinforce the difficulty in determining the controls on Chalk deposition. However, at the broad scale, they do appear to show that thickness patterns in the Cenomanian to Turonian chalks of the West Melbury Marly Chalk, the Zig Zag Chalk and the Holywell Nodular Chalk show correspondence with the underlying Mesozoic extensional basin structure. The major exception to this is the south Dorset area which was uplifted in the Early Cretaceous as an eastern extension to the Cornubian Ridge. The younger New Pit Chalk and Lewes Nodular Chalk show a switch toward thicker successions on the London Platform and thinner, more uniform successions across the Mesozoic basins to the south. This change may indicate some initial basin inversion starting in the mid Turonian which caused a shift in the main locus of Chalk deposition toward East Anglia. The work potentially suggests multiple control-modes shaping the geometry of Chalk deposits, involving an interplay of: 1) long-lived basin-defining faults and structural blocks acting to shape large-scale thickness trends through differential compaction and interaction with relative sea level change; 2) smaller scale structures that may function to more effectively dissipate stress created by intra-Cretaceous tectonic events, producing more localised/sub-regional thickness and facies variations; 3) early basin inversion reflecting the broader basin-scale response to intra-Cretaceous tectonics, potentially responsible for regional shifts in patterns of sedimentation.  相似文献   

徐家围子断陷构造地质特征研究新进展   总被引：14，自引：1，他引：13  

张元高  陈树民  张尔华  姜传金 《岩石学报》2010,26(1):142-148

在徐家围子断陷深层连片三维地震精细解释的基础上,结合前人的研究成果,系统的刻画了深大断裂的性质、产状和时空分布规律。从区域构造应力场着手,详细剖析了徐家围子断陷的构造地质特征,重新构建了深大断裂体系。依据剖面特征和断陷的地质结构,首次在徐家围子断陷内解释出两条深大走滑断裂带,发现深大走滑断裂控制了营城组火山岩的形成和分布。明确了徐家围子断陷"两凹夹一隆、东西分带、南北分块"构造格局的动态演化过程及其控制因素。详细剖析了断陷期地层的沉积发育过程、后期改造过程以及现今赋存特征。为庆深气田火山岩储层分布规律预测奠定了基础。  相似文献   

徐家围子断陷深层结构形成与演化的探讨   总被引：10，自引：1，他引：9  

张尔华  姜传金  张元高  李自安  冯肖宇  吴杰 《岩石学报》2010,26(1):149-157

徐家围子断陷是松辽盆地北部深层最重要的含气断陷。本文根据最新地震和钻井资料综合研究成果,结合前人研究认识,探讨了徐家围子断陷的形成与演化,认为徐家围子断陷在区域构造位置上处于东北地区松辽盆地的北部,处于松辽盆地区域莫霍面隆起的西斜坡上,特定的位置决定了其形成演化的各个阶段受东北地区区域板块构造运动的控制,与松辽盆地的形成与演化具有一定的关系。徐家围子断陷形成与演化可以划分为5个阶段,是太平洋构造域板块间的相互作用和深部热力作用发育演化的结果,这种过程造就了现今南北分块、东西分带、凹隆相间、构造复杂和沉积岩与火山岩并存的地质结构。徐家围子断陷深层现今构造格局受控于近NW向的徐中断裂、近SN向的徐西断裂、近NW向的徐东断裂带和四组近NE向的断裂。本次研究,对以往无法解释的很多地质现象给予了很好的解释,得出了一些崭新的认识,也从宏观上为寻找天然气资源给予了有力指导。  相似文献   

塔里木西克尔基性麻粒岩捕虏体的发现及其地质意义   总被引：2，自引：1，他引：1  

田伟  魏春景  陈咪咪  张贵宾 《岩石学报》2010,26(2):573-583

在塔里木西部新生代碧玄岩中新发现了基性麻粒岩捕虏体。其原生矿物组合为Cpx+Opx+Pl (An=30~50)+Sp+Ilm+Tim,次生矿物组合为Ol+Pl (An>50)+alkaline feldspar+glass。原生矿物组合的温度和压力分别为1005~1059℃ 和 0.6~1.1GPa; 次生矿物组合形成于近等温减压过程和固相线上熔融以及之后的近地表快速冷却。这些麻粒岩捕虏体代表了早期底侵到塔里木板块下地壳的幔源岩浆。  相似文献   

东昆仑牦牛山组流纹岩锆石U-Pb年龄及构造意义   总被引：13，自引：4，他引：9  

陆露  吴珍汉  胡道功  Patrick J BAROSH  郝爽  周春景 《岩石学报》2010,26(4):1150-1158

东昆仑水泥厂地区造山后火山-沉积盆地内形成的牦牛山组磨拉石建造不整合覆盖在前泥盆系地层之上,其形成时代的研究对限定东昆仑早古生代洋盆关闭的时间具有重要意义。应用激光烧蚀多接收器电感耦合等离子体质谱仪(LAMC-ICPMS)方法,对火山-沉积盆地内牦牛山组不同层位的流纹岩夹层进行了精确的锆石U-Pb定年研究。结果表明,盆地北缘牦牛山组底砾岩之上的流纹岩(B743-2)中岩浆锆石~(206)Pb/~(238)U年龄平均值为423.2±1.8Ma,盆地西缘牦牛山组底砾岩之上的流纹岩(B820-1)中岩浆锆石~(206)Pb/~(238)U年龄平均值为408.2±2.4Ma,盆地西缘和南缘牦牛山组中上部碎屑岩中流纹岩夹层(B705-1和B656-1)的岩浆锆石~(206)Pb/~(238)U年龄平均值分别为404.9±4.8Ma和399.6±2.8Ma。它们代表了牦牛山组不同层位火山岩的形成年龄,由此可以限定水泥厂地区牦牛山组形成时间为400～423Ma。上述年代学结果较为精确地限定了东昆仑早古生代洋盆关闭的构造年代。流纹岩中2486～920Ma元古代继承锆石的发现,说明东昆仑南的变质基底和扬子板块变质基底类似,是晋宁期0.9～1.0Ga罗迪尼亚超大陆形成时发育起来的。  相似文献   

Bacterial response to presence of eukaryote inhibitors in water from a coastal marine environment     

S.Y. Newell  B.F. Sherr  E.B. Sherr  R.D. Fallon 《Marine environmental research》1983,10(3):147-157

A method involving chemical (cycloheximide, thiram) inhibition of protozoan bacterivores was applied in an attempt to estimate marine bacterioplanktonic growth rates. The inhibitors were capable of preventing growth of marine protozoan bacterivores at concentrations which did not inhibit growth of marine bacterial assemblages. Use of the predator-inhibition method with incubated water samples from a nearshore marine environment indicated that protozoan grazing control of the size of bacterial standing crop was quite variable with time and site. The apparent degree of control ranged from non-existent to complete. As a means of estimating bacterial generation times, the predator-inhibition method gave results more closely aligned with those of a dividing-cells technique than a [³H]thymidine technique.  相似文献   

Wellsite,Laboratory, and Mathematical Techniques for Determining Sorbed Gas Content of Coals and Gas Shales Utilizing Well Cuttings     

K. David Newell 《Natural Resources Research》2007,16(1):55-66

Drill cuttings can be used for desorption analyses but with more uncertainty than desorption analyses done with cores. Drill cuttings are not recommended to take the place of core, but in some circumstances, desorption work with cuttings can provide a timely and economic supplement to that of cores. The mixed lithologic nature of drill cuttings is primarily the source of uncertainty in their analysis for gas content, for it is unclear how to apportion the gas generated from both the coal and the dark-colored shale that is mixed in usually with the coal. In the Western Interior Basin Coal Basin in eastern Kansas (Pennsylvanian-age coals), dark-colored shales with normal (∼100 API units) gamma-ray levels seem to give off minimal amounts of gas on the order of less than five standard cubic feet per ton (scf/ton). In some cuttings analyses this rule of thumb for gas content of the shale is adequate for inferring the gas content of coals, but shales with high-gamma-ray values (>150 API units) may yield several times this amount of gas. The uncertainty in desorption analysis of drill cuttings can be depicted graphically on a diagram identified as a “lithologic component sensitivity analysis diagram.” Comparison of cuttings desorption results from nearby wells on this diagram, can sometimes yield an unique solution for the gas content of both a dark shale and coal mixed in a cuttings sample. A mathematical solution, based on equating the dry, ash-free gas-contents of the admixed coal and dark-colored shale, also yields results that are correlative to data from nearby cores.  相似文献