Deformations and Structural Evolution of Mesozoic Complexes in Western Chukotka     

B. G. Golionko  E. V. Vatrushkina  V. E. Verzhbitskii  S. D. Sokolov  M. I. Tuchkova 《Geotectonics》2018,52(1):56-72

Detailed structural investigations have been carried out in the Pevek district to specify tectonic evolution of the Chukotka mesozoids. The earliest south-verging folds F1 formed in Triassic rocks at the first deformation stage DI. These structures are overlapped by the northern-verging folds F₂ and overthrusts pertain to the second deformation stage DII. Folding structures F₁ and F₂ were deformed by shear folds F₃, completing stage DII. The DI and DII structures are complicated by roughly NS-trending normal faults marking deformation stage DIII. It has been established that DI is related to the onset of opening of the Amerasian Basin in the Early Jurassic, or, alternatively, to the later accretion of the Kulpolnei ensimatic arc toward the Chukotka microcontinent. DII marks the collision of Siberia and the Chukotka microcontinent in the Late Neocomian. Normal faulting under the roughly E–W-trending extension during DIII is likely related to rift opening of the Podvodnikov and Makarov–Toll basins in the deep Amerasian Basin. Formation of the Okhotsk–Chukotka volcanoplutonic belt completed the structural evolution of the studied region.  相似文献   

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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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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School vulnerability to disaster: examination of school closure,demographic, and exposure factors in Hurricane Ike’s wind swath     

A.-M. Esnard  B. S. Lai  C. Wyczalkowski  N. Malmin  H. J. Shah 《Natural Hazards》2018,90(2):513-535

Damage and destruction to schools from climate-related disasters can have significant and lasting impacts on curriculum and educational programs, educational attainment, and future income-earning potential of affected students. As such, assessing the potential impact of hazards is crucial to the ability of individuals, households, and communities to respond to natural disasters, extreme events, and economic crises. Yet, few studies have focused on assessing the vulnerability of schools in coastal regions of the USA. Using Hurricane Ike’s tropical storm wind swath in the State of Texas as our study area, we: (1) assessed the spatial distribution patterns of school closures and (2) tested the relationship between school closure and vulnerability factors (namely physical exposure and school demographics) using zero-inflated negative binomial regression models. The regression results show that higher probabilities of hurricane strikes, more urbanized school districts, and school districts located in coastal counties on the right side of Ike’s path have significant positive associations with an increase in the number of school closure days. Socioeconomic characteristics were not significantly associated with the number of days closed, with the exception of proportion of Hispanic youth in schools, a result which is not supported by the social vulnerability literature. At a practical level, understanding how hurricanes may adversely impact schools is important for developing appropriate preparedness, mitigation, recovery, and adaptation strategies. For example, school districts on the right side of the hurricane track can plan in advance for potential damage and destruction. The ability of a community to respond to future natural disasters, extreme events, and economic crises depends in part on mitigating these adverse effects.  相似文献   

Benthic and Plankton Foraminifers in Hydrothermally Active Zones of the Mid-Atlantic Ridge (MAR)     

T.?A.?KhusidEmail author  N.?S.?Os’kina  N.?P.?Lukashina  I.?F.?Gablina  N.?V.?Libina  A.?G.?Matul 《Stratigraphy and Geological Correlation》2018,26(1):109-120

Comparison of benthic foraminiferal assemblages from the core obtained within the Peterburgskoe ore field (Mid-Atlantic Ridge) and from the core taken five kilometers away from the ore field revealed evident differences in their composition, in the appearance of their shells, and also in the benthic–plankton species ratio. It was noted that the foraminiferal assemblage from the ore-bearing sediments of the Petersburg field was characterized by a higher relative content of benthic species and a large number of chemically altered and broken shells. The first occurrence of the species Osangularia umbonifera, which is able to exist in lowoxygen and CaCO₃-undersaturated bottom waters at the boundary of biogenic sediments surrounding the ore field and in the ore-bearing sediments, was established. In the core section sampled beyond the ore field, the composition of foraminiferal assemblages differs insignificantly from typical oceanic ones.  相似文献   

Influence of the sediment delivery ratio index on the analysis of silting and break risk in the Plasencia reservoir (Central System,Spain)     

Sánchez  Y.  Martínez-Graña  A.  Santos-Francés  F.  Yenes  M. 《Natural Hazards》2018,90(3):1407-1426

The random forest method was used to generate susceptibility maps for debris flows, rock slides, and active layer detachment slides in the Donjek River area within the Yukon Alaska Highway Corridor, based on an inventory of landslides compiled by the Geological Survey of Canada in collaboration with the Yukon Geological Survey. The aim of this study is to develop data-driven landslide susceptibility models which can provide information on risk assessment to existing and planned infrastructure. The factors contributing to slope failure used in the models include slope angle, slope aspect, plan and profile curvatures, bedrock geology, surficial geology, proximity to faults, permafrost distribution, vegetation distribution, wetness index, and proximity to drainage system. A total of 83 debris flow deposits, 181 active layer detachment slides, and 104 rock slides were compiled in the landslide inventory. The samples representing the landslide free zones were randomly selected. The ratio of landslide/landslide free zones was set to 1:1 and 1:2 to examine the results of different sample ratios on the classification. Two-thirds of the samples for each landslide type were used in the classification, and the remaining 1/3 were used to evaluate the results. In addition to the classification maps, probability maps were also created, which served as the susceptibility maps for debris flows, rock slides, and active layer detachment slides. Success and prediction rate curves created to evaluate the performance of the resulting models indicate a high performance of the random forest in landslide susceptibility modelling.  相似文献   

Biostratigraphy and Sedimentary Settings of the Middle Devonian Succession of the Yuryung-Tumus Peninsula,Khatanga Gulf of the Laptev Sea     

N. V. Sennikov  T. A. Shcherbanenko  I. V. Varaksina  N. G. Izokh  E. S. Sobolev  A. Yu. Yazikov 《Stratigraphy and Geological Correlation》2018,26(3):267-282

The age of the Paleozoic sedimentary successions of the Yuryung-Tumus Peninsula in the Khatanga Gulf is determined as Middle Devonian, late Eifelian, and the beginning of the early Givetian on the basis of the study of brachiopods, ammonoids, nautiloids, bactritoids, gastropods, and conodonts, and in the terminology of the standard conodont succession, these deposits are not older than the late Eifelian Tortodus kockelianus Zone, but include the terminal Eifelian Polygnathus ensensis Zone and the first Givetian Polygnathus hemiansatus Zone and are no younger than the beginning of the early Givetian Polygnathus varcus Zone. The Middle Devonian sedimentary successions of the Yuryung-Tumus Peninsula show the level of the global sedimentary Ka?ak Event. The areas of distribution of the Devonian sedimentary deposits in the Yuryung-Tumus Peninsula in the Khatanga Gulf should be considered as one of the fragments of the regional geological structures of a remote (isolated?) region of the Taymyr Fold System rather than a component of the structures of the northern Siberian Platform.  相似文献   

Rethinking flood risk communication     

E. Rollason  L. J. Bracken  R. J. Hardy  A. R. G. Large 《Natural Hazards》2018,92(3):1665-1686

Flooding is a serious hazard across Europe, with over 200 major floods documented in the last two decades. Over this period, flood management has evolved, with a greater responsibility now placed on at-risk communities to understand their risk and take protective action to develop flood resilience. Consequently, communicating flood risk has become an increasingly central part of developing flood resilience. However, research suggests that current risk communications have not resulted in the intended increase in awareness, or behavioural change. This paper explores how current risk communications are used by those at risk, what information users desire and how best this should be presented. We explore these questions through a multi-method participatory experiment, working together with a competency group of local participants in the town of Corbridge, Northumberland, the UK. Our research demonstrates that current risk communications fail to meet user needs for information in the period before a flood event, leaving users unsure of what will happen, or how best to respond. We show that participants want information on when and how a flooding may occur (flood dynamics), so that they can understand their risk and feel in control of their decisions on how to respond. We also present four prototypes which translate these information needs into new approaches to communicating flood risk. Developed by the research participants, these proposals meet their information needs, increase their flood literacy and develop their response capacity. The findings of the research have implications for how we design and develop future flood communications, but also for how we envisage the role of flood communications in developing resilience at a community level.  相似文献   

Magmatic Evolution of Changbaishan Tianchi Volcano,China–North Korea: Evidence from Mineral-Hosted Melt and Fluid Inclusions     

O. A. Andreeva  V. V. Yarmolyuk  I. A. Andreeva  S. E. Borisovskiy 《Petrology》2018,26(5):515-545

Data on mineral-hosted melt, fluid, and crystalline inclusions were used to study the composition and evolution of melts that produced rocks of Changbaishan Tianchi volcano, China–North Korea, and estimate their crystallization parameters. The melts crystallized within broad ranges of temperature (1220–700°C) and pressure (3100–1000 bar), at a drastic change in the redox potential: Δ log \(f_{O_2}\) from NNO + 0.92 to +1.42 for the basalt melts, NNO –1.61 to –2.09 for the trachybasaltic andesite melts, NNO –2.63 to –1.89 for the comendite melts, and NNO –1.55 to –3.15 for the pantellerite melts. The paper reports estimates of the compositions of melts that produced the continuous rock series from trachybasalt to comendite and pantellerite. In terms of trace-element concentrations, all of the mafic melts are comparable with OIB magmas. The silicic melts are strongly enriched in trace elements and REE. The most strongly enriched melts contain concentrations of certain elements almost as high as in ores of these elements. The paper reports data on H2O concentrations in melts of different composition. It is demonstrated that the variations in the H₂O concentrations were controlled by magma degassing. Data are reported on the Sr and Nd composition of the rocks. The deviations in the Sr isotopic composition are proportional to the ⁸⁷Sr/⁸⁶Sr ratio and could be produced in a melt with a high enough ⁸⁷Sr/⁸⁶Sr ratio during a geologically fairly brief time period. The evolution of melts that produced rocks of the volcano was controlled by crystallization differentiation of the parental basalt magmas at insignificant involvement of melt mixing and liquid immiscibility of silicate and sulfide melts. The alkaline salic rocks were generated in shallow-sitting (13–3.5 km) magmatic chambers in which the melts underwent profound differentiation that gave rise to pantellerites and comendites strongly enriched in trace elements (Th, Nb, Ta, Zr, and REE). Data on the composition of the magmas and parameters of their derivation are used to develop a generalized petrologic–geodynamic model for the origin of Changbaishan Tianchi volcano.  相似文献   

Origin of complex zoning in olivine from diverse,diamondiferous kimberlites and tectonic settings: Ekati (Canada), Alto Paranaiba (Brazil) and Kaalvallei (South Africa)     

Lim  Emilie  Giuliani  Andrea  Phillips  David  Goemann  Karsten 《Mineralogy and Petrology》2018,112(2):539-554

Olivine in kimberlites can provide unique insights into magma petrogenesis, because it is the most abundant xenocrystic phase and a stable magmatic product over most of the liquid line of descent. In this study we examined the petrography and chemistry of olivine in kimberlites from different tectonic settings, including the Slave craton, Canada (Ekati: Grizzly, Koala), the Brasilia mobile belt (Limpeza-18, Tres Ranchos-04), and the Kaapvaal craton, South Africa (Kaalvallei: Samada, New Robinson). Olivine cores display a wide range of compositions (e.g., Mg# = 78–95). The similarity in olivine composition, resorption of core zones and inclusions of mantle-derived phases, indicates that most olivine cores originated from the disaggregation of mantle peridotites, including kimberlite-metasomatised lithologies (i.e. sheared lherzolites and megacrysts). Olivine rims typically show a restricted range of Mg#, with decreasing Ni and increasing Mn and Ca contents, a characteristic of kimberlitic olivine worldwide. The rims host inclusions of groundmass minerals, which implies crystallisation just before and/or during emplacement. There is a direct correlation between olivine rim composition and groundmass mineralogy, whereby high Mg/Fe rims are associated with carbonate-rich kimberlites, and lower Mg/Fe rims are correlated with increased phlogopite and Fe-bearing oxide mineral abundances. There are no differences in olivine composition between explosive (Grizzly) and hypabyssal (Koala) kimberlites. Olivine in kimberlites also displays transitional zones and less common internal zones, between cores and rims. The diffuse transitional zones exhibit intermediate compositions between cores and rims, attributed to partial re-equilibration of xenocrystic cores with the ascending kimberlite melt. In contrast, internal zones form discrete layers with resorbed margins and restricted Mg# values, but variable Ni, Mn and Ca concentrations, which indicates a discrete crystallization event from precursor kimberlite melts at mantle depths. Overall, olivine exhibits broadly analogous zoning in kimberlites worldwide. Variable compositions for individual zones relate to different parental melt compositions rather than variations in tectonic setting or emplacement mechanism.

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