Groundwater facie analysis in the upper Cross River basin,southeast Nigeria     

Stephen N. Ukpai  Paulinus N. Nnabo  Hilary N. Eze 《Environmental Earth Sciences》2016,75(20):1345

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Slab behavior beneath Eastern Asia from full waveform tomography     

Stephen P. Gran  Kai Tao  Fenglin Niu 《《地质学报》英文版》2018,92(Z1):328-328

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Statistical analyses of Global U-Pb Database 2017     

Stephen J.Puetz  Carlos E.Ganade  Udo Zimmermann  Glenn Borchardt 《地学前缘(英文版)》2018,9(1):121-145

The method of obtaining zircon samples affects estimation of the global U-Pb age distribution.Researchers typically collect zircons via convenience sampling and cluster sampling.When using these techniques,weight adjustments proportional to the areas of the sampled regions improve upon unweighted estimates.Here,grid-area and modern sediment methods are used to weight the samples from a new database of 418,967 U-Pb ages.Preliminary tests involve two age models.Model-1 uses the most precise U-Pb ages as the best ages.Model-2 uses the~(206)Pb/~(238)U age as the best age if it is less than a1000 Ma cutoff,otherwise it uses the~(207)Pb/~(206)Pb age as the best age.A correlation analysis between the Model-1 and Model-2 ages indicates nearly identical distributions for both models.However,after applying acceptance criteria to include only the most precise analyses with minimal discordance,a histogram of the rejected samples shows excessive rejection of the Model-2 analyses around the1000 Ma cutoff point.Because of the excessive rejection rate for Model-2,we select Model-1 as the preferred model.After eliminating all rejected samples,the remaining analyses use only Model-1 ages for five rock-type subsets of the database:igneous,meta-igneous,sedimentary,meta-sedimentary,and modern sediments.Next,time-series plots,cross-correlation analyses,and spectral analyses determine the degree of alignment among the time-series and their periodicity.For all rock types,the U-Pb age distributions are similar for ages older than 500 Ma,but align poorly for ages younger than 500 Ma.The similarities(500 Ma)and differences(500 Ma)highlight how reductionism from a detailed database enhances understanding of time-dependent sequences,such as erosion,detrital transport mechanisms,lithification,and metamorphism.Time-series analyses and spectral analyses of the age distributions predominantly indicate a synchronous period-tripling sequence of~91-Myr,~273-Myr,and~819-Myr among the various rock types.  相似文献   

Is UN Sustainable Development Goal 15 relevant to governing the intimate land-use/groundwater linkage?     

Foster  Stephen 《Hydrogeology Journal》2018,26(4):979-982

Hydrogeology Journal - The close link between land use and groundwater has long been recognised, but not widely translated into integrated policy and management practices. Common understanding is...  相似文献   

Impact of irrigated agriculture on groundwater-recharge salinity: a major sustainability concern in semi-arid regions     

Stephen Foster  Antonio Pulido-Bosch  Ángela Vallejos  Luis Molina  Armando Llop  Alan M. MacDonald 《Hydrogeology Journal》2018,26(8):2781-2791

Intensive irrigated agriculture substantially modifies the hydrological cycle and often has major environmental impacts. The article focuses upon a specific concern—the tendency for progressive long-term increases in the salinity of groundwater recharge derived from irrigated permeable soils and replenishment of unconfined aquifers in more arid regions. This process has received only scant attention in the water-resource literature and has not been considered by agricultural science. This work makes an original contribution by analysing, from scientific principles, how the salinisation of groundwater recharge arises and identifies the factors affecting its severity. If not proactively managed, the process eventually will impact irrigation waterwell salinity, the productivity of agriculture itself, and can even lead to land abandonment. The types of management measure required for mitigation are discussed through three detailed case histories of areas with high-value groundwater-irrigated agriculture (in Spain, Argentina and Pakistan), which provide a long-term perspective on the evolution of the problem over various decades.  相似文献   

The First Hop: Use of Beaufort Sea Deltas by Hatch-Year Semipalmated Sandpipers     

Roy T. Churchwell  Steve Kendall  Stephen C. Brown  Arny L. Blanchard  Tuula E. Hollmen  Abby N. Powell 《Estuaries and Coasts》2018,41(1):280-292

River deltas along Alaska’s Beaufort Sea coast are used by hatch-year semipalmated sandpipers (Calidris pusilla) after leaving their terrestrial natal sites, but the drivers of their use of these stopover sites on the first “hop” of fall migration are unknown. We quantified sandpiper temporal distribution and abundance as related to food resources at three river deltas during the beginning of their fall migration (post-breeding period) to compare the habitat quality among these deltas. We conducted population counts, sampled invertebrates, and captured birds to collect blood samples from individuals for triglyceride and stable isotope analyses to determine fattening rates and diet. Patterns of sandpiper and invertebrate abundance were complex and varied among deltas and within seasons. River deltas were used by sandpipers from late July to late August, and peak sandpiper counts ranged from 1000 to 4000 individuals, of which 98% were hatch-year semipalmated sandpipers. Isotopic signatures from blood plasma samples indicated that birds switched from a diet of upland tundra to delta invertebrate taxa as the migration season progressed, suggesting a dependence on delta invertebrates. Despite differences in diet among deltas, we found no differences in fattening rates of juvenile sandpipers as indicated by triglyceride levels. The number of sandpipers was positively associated with abundance of Amphipoda and Oligochaeta at the Jago and Okpilak-Hulahula deltas; an isotopic mixing model indicated that sandpipers consumed Amphipoda and Oligochaeta at Jago, mostly Chironomidae at Okpilak-Hulahula and Spionidae at Canning. Regardless of the difference in sandpiper diets at the Beaufort Sea deltas, their similar fattening rates throughout the season indicate that all of these stopover sites provide a critical food resource for hatch-year sandpipers beginning their first migration.  相似文献   

The Pebbles on the Beach: A Spotter’s Guide by Clarence Ellis,new edition,Faber & Faber,London (2018). xiii+218 pp., Pbk., ISBN: 978-0-571-34793-3. £9.99     

Stephen K. Donovan 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(6):798-799

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Anthropocene: A Very Short Introduction,Erle C. Ellis,Oxford University Press,Oxford (2018). xxii+183 pp., Pbk., ISBN: 978-0-19-879298-7. £7.99.     

Stephen K. Donovan 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(5):693

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Fossils of Folkestone,Kent, Philip Hadland,Siri Scientific Press,Manchester (2018). 148 pp., Pbk,ISBN: 978-0-9957496-5-8, £15.00     

Stephen K. Donovan 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(4):581

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Reading the Rocks: How Victorian Geologists Discovered the Secret of Life,Brenda Maddox,Bloomsbury, London (2017), xii+254 pp., Hbk., ISBN: 978-1-4088-7958-0. UK£20.00     

Stephen K. Donovan 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(1):92

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