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151.
152.
Jean‐Len Léticée Mélody Philippon Jean‐Jacques Cornée Philippe Münch Lyvane De Min Mélanie Noury Auran Randrianasolo Jean‐Frédéric Lebrun 《地学学报》2017,29(4):245-252
In this study, we investigate the Lesser Antilles forearc basin, focusing on the late Pliocene to Pleistocene sedimentary archives in order to track the occurrence of extreme events triggered by enhanced subduction‐related tectono‐volcanic activity. We identify late Piacenzian deposits covering a major regional erosional surface, displaying sedimentary dykes and large marine boulders embedded in a mixed continental–marine matrix, characteristic of tsunamites. We interpret this episode of platform emersion and the successive cataclysmic deposits as resulting from enhanced tectonic activity at the interface of the subduction zone, synchronous with the initiation of the Lesser Antilles volcanic arc. We then discuss the implications in terms of the mechanical behaviour of the Lesser Antilles subduction zone. 相似文献
153.
Corbiniano Silva Luiz Claudio Gomes Pimentel Luiz Landau Paulo Fernando Lavalle Heilbron Filho Fabiana Guimarães Resende Gobbo Pryscila de Jesus de Sousa 《Environmental Earth Sciences》2017,76(3):133
Accidents in nuclear power plants are problems of great complexity, mainly due to their consequences, such as the population evacuation from the enterprise influence area. The decision-making and emergency plans must be well articulated and require good local geographic space knowledge and the interactions of their environments. This study is a contribution to the emergency plans for the Almirante Álvaro Alberto Nuclear Power Plant, currently the only nuclear complex in Brazil, located in Angra dos Reis, Rio de Janeiro. The study confirmed the region’s main geoenvironmental aspects as winds and rainfall, landslides and population density were evaluated as important elements in the local emergency process. Their integrated analysis supported scenario identification and critical regional points and highlighted population evacuation escape routes. These important results characterized the support to local emergency management actions and guidelines. Furthermore, the geographic information systems was configured as an integrated spatial and temporal analysis platform to associate meteorological, geological/geomorphological and socio-economic data, playing a key role to support the evacuation planning in the event of nuclear power plant accidents. 相似文献
154.
da Silva Richarde Marques Santos Celso Augusto Guimarães Silva Jorge Flávio Casé Braga da Costa Silva Alexandro Medeiros Brasil Neto Reginaldo Moura 《Natural Hazards》2020,104(2):1953-1954
Natural Hazards - The article “Spatial distribution and estimation of rainfall trends and erosivity in the Epitácio Pessoa reservoir catchment, Paraíba, Brazil”, written by da... 相似文献
155.
The Sea to Sky Corridor has experienced hundreds of historic and prehistoric landslides. The most common types of historical
landslides are rock falls and debris flows, which are relatively small in volume but can be damaging. These types of failures
are more common in the southern part of the corridor, between Horseshoe Bay and Porteau, where infrastructure has been built
in close proximity to steep slopes. Farther north, fewer landslides have been reported historically, but those that have been
recorded are usually large and date to prehistoric time (e.g., Cheekye fan and Mystery Creek rock avalanche). As part of a
Geological Survey of Canada surficial geology and landslide inventory mapping study, Mystery Creek rock avalanche, near Whistler,
British Columbia, was sampled for 36Cl dating. Samples were collected from three large flat boulders of quartz diorite in the rock avalanche deposit to test a
correlation with the previously reported radiocarbon age of 800 ± 100 years BP on charcoal. One sample revealed a mean age
of 2,400 years and the other two, 4,300 and 4,800 years, respectively. These new results point to four possible interpretations:
(1) Mystery Creek landslide is about 800 years old; (2) Based on the overlapping 2σ uncertainties, the rock avalanche took
place between 2,200 and 3,600 years ago; (3) The rock avalanche deposit is 2,400 years old and the other two blocks are too
old; and (4) The rock avalanche is between 4,300 and 4,800 years old. Although there is strength in numbers and it is likely
that the age varies between 4,300 and 4,800 years, we favor the second interpretation where the age range is broader and statistically
significant for all three samples. Moreover, at this time, we favor discounting the radiocarbon age based on a greater number
of samples analyzed for 36Cl analysis and lack of detailed information on the charcoal sampling. The causes and triggers of the Mystery Creek rock avalanche
remain unknown, but direct glacial debuttressing can be ruled out. Some of the causes are likely a combination of the regional
tectonic setting which produced preferential planes of weakness reflected in the trend of major faults, headscarp, and reverse
scarps. Yearly cycles of freezing and thawing are considered a plausible cause based on present-day climate records. Finally,
a large earthquake still remains a possible trigger because of the active tectonic setting and the presence of potentially
contemporaneous landslides in the same area. Mystery Creek rock avalanche and other historic and pre-historic landslides contributed
to validation of a heuristic rock fall/rock slide/rock avalanche susceptibility mapping study, in which their headscarps correlated
well with medium-high to high susceptibility zones. In terms of hazard assessment, Mystery Creek rock avalanche, although
pre-historic in age, occurred in present-day climatic and geological conditions. This poses a threat to infrastructure such
as the Sea to Sky Highway, railway, and power line. 相似文献
156.
Installation of a vertical slurry wall around an Italian quarry lake: complications arising and simulation of the effects on groundwater flow 总被引:1,自引:0,他引:1
Slurry walls are non-structural barriers that are constructed underground to impede groundwater flow or manage groundwater
control problems. The study area is in the Piemonte plain (Italy), close to the River Po. Quarrying works carried out below
the piezometric surface created two big quarry lakes. The local groundwater system is characterized by a lower semi-confined
aquifer, which is overlain by a semi-permeable bed of clayey peat (aquitard) and an upper unconfined aquifer. Locally, the
peat fades away and the granulometry of this horizon becomes silty sandy. A planned enlargement of the quarry will increase
the size and depth of the quarry lakes. So the aquitard bed between the two aquifers will be damaged, creating a mixing rate
of groundwater. Such a procedure would not be compatible with the presence of two municipal wells upstream from the quarries.
Consequently, the installation of a vertical diaphragm (slurry wall) is recommended to separate the aquifers and to act as
a filter for the groundwater flowing from the unconfined to the semi-confined aquifer. To predict the consequences caused
by the installation of the vertical diaphragm separating the unconfined aquifer and the semi-confined one, a specifically
adjusted finite-difference model was used. The model showed a maximum rising of the water table equal to 12 cm, just upstream
of the diaphragm and for a distance of about 100 m, and a maximum lowering of 2 cm just downstream of the diaphragm. However,
the slurry wall would not cause any change in the piezometric head in the area where there are municipal wells and, hence,
will not have any negative effect on the functionality of the municipal wells. Moreover, the migration of water from the unconfined
aquifer through the vertical diaphragm will stimulate a series of attenuation and auto-depuration processes of eventual contaminants.
These processes are due to the higher crossing time that the groundwater flow takes to go through the vertical barrier (t
a = 96.5 days, whereas for the horizontal semi-permeable layer t
a = 9.6 days). So, the vertical diaphragm can be a resolutive element, representing a mediation and separation factor between
the unconfined and the semi-confined aquifers along the border of the quarrying areas, and a protective barrier for the water
quality of the quarry lake and the semi-confined aquifer. 相似文献
157.
Isabel Margarida Horta Ribeiro Antunes Ana Margarida Ribeiro Neiva João Manuel Farinha Ramos Paulo Bravo Silva Maria Manuela Vinha Guerreiro Silva Fernando Corfu 《Chemie der Erde / Geochemistry》2013
In the Segura area, Variscan S-type granites, aplite veins and lepidolite-subtype granitic aplite-pegmatite veins intruded the Cambrian schist-metagraywacke complex. The granites are syn D3. Aplite veins also intruded the granites. Two-mica granite and muscovite granite have similar ages of 311.0 ± 0.5 Ma and 312.9 ± 2.0 Ma but are not genetically related, as indicated by their geochemical characteristics and (87Sr/86Sr)311 values. They correspond to distinct pulses of magma derived by partial melting of heterogeneous metapelitic rocks. Major and trace elements suggest fractionation trends for: (a) muscovite granite and aplite veins; (b) two-mica granite and lepidolite-subtype aplite-pegmatite veins, but with a gap in most of these trends. Least square analysis for major elements, and modeling of trace elements, indicate that the aplite veins were derived from the muscovite granite magma by fractional crystallization of quartz, plagioclase, K-feldspar and ilmenite. This is supported by the similar (87Sr/86Sr)311 and δ18O values and the behavior of P2O5 in K-feldspar and albite. The decrease in (87Sr/86Sr)311 and strong increase (1.6‰) in δ18O from two-mica granite to lepidolite-subtype aplite-pegmatite veins, and the behaviors of Ca, Mn and F of hydroxylapatite indicate that these veins are not related to the two-mica granite. 相似文献
158.
新疆巴什布拉克地区有机地球化学特征及其对铀成矿的控制 总被引:1,自引:0,他引:1
巴什布拉克铀矿床是新疆典型的与地沥青有关的砂岩型铀矿床。研究该矿床油气有机质来源、演化程度及后期降解过程,有助于深入解读原生红层在油气二次还原条件下的铀富集机理。本文针对该区铀矿化与油气密切相关的特点,采集了钻孔中具明显油浸的铀矿化砂岩和砾岩进行提取物分析。通过对提取物氯仿沥青“A”及其族组成和饱和烃气相色谱分析可见,有机质正构烷烃主峰碳为C17、C18、C20、C24和C25;(C21+C22)/(C28+C29)为0.58~12.17;Pr/Ph为0.40~1.47;Ts/Tm为1.3~16.1,高含量的系列重排藿烷化合物和“V”型甾烷分布,显示该区油气有机质主要来源于中下侏罗统湖相沉积。OEP为1.04~1.14,深部样品的OEP<1.0;C-21/C+22为0.18~2.11,指示局部烃源岩可能受到热改造提前进入生油门限,导致矿区深部浸入的油气有机质演化程度较高。早期浸入的油气有机质饱和烃气相色谱基线呈上飘“鼓包”状突出,Pr/nC17为0.6~0.9,Ph/nC18为0.8~11.98,表明受到氧化和微生物降解作用,在此过程中铀发生沉淀和富集。铀矿化主要受油气氧化和降解产物地沥青分布范围控制。 相似文献
159.
Silvia Barredo Farid Chemale Claudia Marsicano Janaína N. Ávila Eduardo G. Ottone Victor A. Ramos 《Gondwana Research》2012,21(2-3):624-636
Extensional processes that followed the Gondwanan Orogeny rise to the development of a series of rift basins along the continental margin over older accreted Eopaleozoic terranes. Stratigraphic, structural, paleontological, and isotopic studies are presented in this work in order to constrain the ages of the sedimentary infilling and to analyze the tectosedimentary evolution of one of the Cuyo basin depocenters, known as Rincón Blanco. This asymmetrical half-graben was filled by continental sediments under a strong tectonic control. The infilling was strongly controlled by tectonics which in term produced distinctive features along the whole sedimentary sequence. Using a combination of lithological and structural data the infilling was subdivided into packages of genetically linked units bounded by regional extended surfaces. Several tuffs and acid volcanic rocks have been collected across the whole section of the Rincon Blanco sub-basin for SHRIMP and LA-MC-ICPMS U–Pb zircon dating. The ages obtained range from 246.4 ± 1.1 Ma to 230.3 ± 1.5 Ma which is the time elapsed for the deposition of three tectono-sequence units separated by regional unconformities and mainly constrained to the Middle Triassic. They are interpreted as a result of a reactivation of the extensional system that has evolved along strike as segments of faults that linked together and/or as laterally propagating faults. Regional correlation with coeval rift basins permits to establish north-south propagation in the extensional regime along the western margin of SW Gondwana. This trending started in the lowermost Triassic and extended until the latest Triassic. Two of them were precisely correlated with Cerro Puntudo and Cacheuta half-graben systems. The new data indicate that the three sequences were mostly deposited during the Middle Triassic (246 to 230 Ma), with no evidence of sedimentation during Norian and Rhaetian, which is in conflict with some previous biostratigraphic studies. 相似文献
160.
Groundwater in the Cambrian–Vendian aquifer system has a strongly depleted stable isotope composition (δ18O values of about −22‰) and a low radiocarbon concentration, which suggests that the water is of glacial origin from the last Ice Age. The aim of this paper was to elucidate the timing of infiltration of glacial waters and to understand the geochemical evolution of this groundwater. The composition of the dissolved inorganic C (DIC) in Cambrian–Vendian groundwater is influenced by complex reactions and isotope exchange processes between water, organic materials and rock matrix. The δ13C composition of dissolved inorganic C in Cambrian–Vendian water also indicates a bacterial modification of the isotope system. The corrected radiocarbon ages of groundwater are between 14,000 and 27,000 radiocarbon years, which is coeval with the advance of the Weichselian Glacier in the area. 相似文献