从构造热事件探讨湖南志留纪沉积时限兼论盆地演化特征          下载免费PDF全文

刘南  高翔  艾国梁  贺良 《地质找矿论丛》2017,32(3):428-433

湖南地区志留纪的沉积时限一直以来争议颇多,笔者通过对该区沉积特征及层序地层、构造运动分析发现:小溪峪组属于一套有障壁海岸浅海细碎屑沉积,是海水由南东向北西退却期的沉积响应,属于早期高水位体系域;泥盆系云台观组属一套海侵型的海相陆源碎屑岩沉积,从野外的界面特征分析云台观组为一套开阔海岸受波浪作用明显的以石英砂为主体的沉积物,属于广西运动之后由东南向北西形成的海侵过程的沉积响应。小溪峪组与云台观组二者所属沉积盆地环境和演化不同,其界面属于Ⅰ型层序界面,不整合接触。广西运动导致的江南造山带的隆起在430Ma左右结束,志留纪沉积盆地应大部分消亡,由此认为志留纪沉积盆地接受的沉积物时间也应在相对应时段中,小溪峪组在湖南地区不存在晚志留纪沉积物。  相似文献   

Foraging strategy of little auks under divergent conditions on feeding grounds     

Katarzyna Wojczulanis-Jakubas  Dariusz Jakubas  Nina J. Karnovsky  & Wojciech Walkusz 《Polar research》2010,29(1):22-29

A dual foraging strategy (long versus short trips) has been described for some species of seabirds, such as petrels, albatrosses (Procellariiformes) and penguins (Sphenisciphormes). Such a strategy has recently been reported for little auks ( Alle alle ) from the central coast of west Spitsbergen, Svalbard. This has been explained as a response to poor trophic conditions close to the breeding colony, and better conditions further away (150 km). In the present study, we investigated the foraging strategy of little auks in Hornsund, southern Spitsbergen, during two seasons with contrasting oceanographic conditions. During 2004, foraging conditions for little auks were good: cold Arctic waters rich in profitable high-energy food were dominant in their feeding grounds. Conversely, during 2006 there was a great influx of warm Atlantic water in the feeding area, inducing poor foraging conditions. In both seasons we examined the pattern of foraging trip lengths automatically with a video camera (both adults from four nests in each year), and by direct non-stop observation of 20–54 individually marked birds. Our results showed that the dual strategy and the ratio of short and long trips were consistent, regardless of the conditions in the feeding grounds. This suggests that the strategy is inherent and may be crucial for the self-maintenance of adults.  相似文献   

Impact of climate change on floodplain inundation and hydrological connectivity between wetlands and rivers in a tropical river catchment   总被引：1，自引：0，他引：1       下载免费PDF全文

Fazlul Karim  Cuan Petheram  Steve Marvanek  Catherine Ticehurst  Jim Wallace  Masud Hasan 《水文研究》2016,30(10):1574-1593

  相似文献   

Comparison of precipitation extremes estimation using parametric and nonparametric methods     

Jan Holešovský  Michal Fusek  Vít Blachut  Jaroslav Michálek 《水文科学杂志》2013,58(13):2376-2386

  相似文献   

Intensity–duration–frequency curves exploiting neighbouring extreme precipitation data     

András Bárdossy  Geoffrey Pegram 《水文科学杂志》2013,58(11):1593-1604

ABSTRACT

Records of precipitation extremes are essential for hydrological design. In urban hydrology, intensity–duration–frequency curves are typically estimated from observation records. However, conventional approaches seldom consider the areal extent of events. If they do, duration-dependent area reduction factors are used, but precipitation is measured at only a few locations. Due to the high spatial variability of precipitation, it is relatively unlikely that a gauged observation network will capture the extremes that occur during a precipitation event. Therefore, the area reduction approach cannot be regarded as the reduction of an observed maximum. To investigate precipitation extremes, spatial aspects need to be considered using different approaches. Here, we both address the conventional practice of area reduction and consider a within-area chance of increased precipitation, defined as the maximum precipitation intensity observed in a cluster within a selected domain. The results show that (1) the risk of urban flooding is routinely underestimated in current design practice, and (2) traditional calculations underestimate extremes by as much as 30–50%. We show how they can be revised sensibly.  相似文献   

Appropriate monitoring techniques using bomb tritium and other geochemical parameters in hydrogeological investigations     

BONIFACE C. E. EGBOKA 《水文科学杂志》2013,58(2):207-224

ABSTRACT

A critical review of earlier uses of bomb tritium spotlights problems in its applications that may result in erroneous interpretations. The old monitoring technique using boreholes causes mixing of groundwaters of different age zones. In this study, the mixing problem is overcome by using modern monitoring devices of multi-level samplers and bundle piezometers that yield groundwater samples of small volumes at closely-spaced intervals. The old method may be used to determine recharge and discharge areas of aquifers and used where pollution poses no serious threat. Otherwise, the major pumpage of the aquifer distorts and reverses flow directions, causes mixing of different waters and may spread the pollutants. The disadvantages of the modern method include its restricted use in shallow aquifers and porous media.  相似文献   

OPERATING A LIMESTONE AQUIFER AS A RESERVOIR FOR A WATER SUPPLY SYSTEM     

Y. HARPAZ  J. SCHWRZ 《水文科学杂志》2013,58(1):78-90

Abstract

An aquifer can be used not only as water source but also as a regulating reservoir linked to a water supply system, planning the operation of such reservoirs calls for a good knowledge of the characteristics and limitations of the aquifer, an estimate of its natural replenishment and outflows, as weil as the determination of a programme for pumping and artificial recharge.

A limestone aquifer of karstic nature, heavily exploited and artificially recharged, has been studied recently with respect to its storage capacity and responses to a planned scheme of operations established for the national water supply systems.

The physical characteristics of this aquifer, its inflows, outflows and dynamic behaviour, were first determined by geological and hydrological investigations. The dynamic model obtained was then verified and improved by use of a resistor-capacitor electric analog constructed for this purpose. Later on, several operational alternatives were tested on the same analog. An optimization analysis was performed on a simplified single cell model representing the aquifer system. The methodology of such integrational operation is discussed in light of the results obtained.  相似文献   

Snow effects on alpine vegetation in the Qinghai-Tibetan Plateau   总被引：1，自引：0，他引：1  

《International Journal of Digital Earth》2013,6(1):58-75

Understanding the relationships between snow and vegetation is important for interpretation of the responses of alpine ecosystems to climate changes. The Qinghai-Tibetan Plateau is regarded as an ideal area due to its undisturbed features with low population and relatively high snow cover. We used 500 m Moderate Resolution Imaging Spectroradiometer (MODIS) datasets during 2001–2010 to examine the snow–vegetation relationships, specifically, (1) the influence of snow melting date on vegetation green-up date and (2) the effects of snow cover duration on vegetation greenness. The results showed that the alpine vegetation responded strongly to snow phenology (i.e., snow melting date and snow cover duration) over large areas of the Qinghai-Tibetan Plateau. Snow melting date and vegetation green-up date were significantly correlated (p < 0.1) in 39.9% of meadow areas (accounting for 26.2% of vegetated areas) and 36.7% of steppe areas (28.1% of vegetated areas). Vegetation growth was influenced by different seasonal snow cover durations (SCDs) in different regions. Generally, the December–February and March–May SCDs played a significantly role in vegetation growth, both positively and negatively, depending on different water source regions. Snow's positive impact on vegetation was larger than the negative impact.  相似文献   

An analysis of intra-event precipitation variability for the United States (1980–2010)     

David M. Brommer  Randall S. Cerveny  Robert C. Balling Jr 《自然地理学》2013,34(6):456-470

Hourly precipitation data were collected from 143 first-order US weather stations during the period from 1980 to 2009 to assess the internal distribution of precipitation events lasting at least three hours. A total of 46,595 individual precipitation events were identified and evaluated using the mean, standard deviation, skewness, kurtosis, and the number of peaks occurring within an event. Mean event duration is longest along the West and Northwest coasts, the Mid-South, the Mid-Atlantic, and the Northeast; while shorter-duration events are more frequent in the Rocky Mountains, the Southwest, and the Great Plains. Mean event precipitation and standard deviation are greatest along the Gulf Coast and decrease inland. Precipitation events are positively skewed, indicating that more precipitation tends to occur earlier in the event. The most positively-skewed events are also located in regions flanking the Gulf of Mexico, while less-skewed events are common in the Northwest and Rocky Mountain regions. Event kurtosis is negative throughout the entire USA, with the highest negative values generally west of the Front Range, where cyclonic development and transition produce more evenly distributed precipitation within storms. Intra-event precipitation maxima were also evaluated, with western Florida and the desert Southwest having the greatest number per event.  相似文献   

Wave separation for the great Sumatra-Andaman earthquake with regional seismic array     

Chunyan Zhang  Sidao Ni  Key Lab of Intelligent Computing  Signal Processing of Ministry of Education  School of Mathematics  Anhui University  Hefei  China Key Laboratory of Dynamic Geodesy 《地震学报(英文版)》2011,(1):127-132

We analyzed the seismic waveforms from the December 26,2004 Sumatra-Andaman earthquake recorded at broadband seismic stations in western Europe.Previous studies involving of the beam-forming technique and high frequency analysis suggest that the earthquake ruptured with a duration of around 500 s.This very long duration makes P wave overlap with later arrivals such as PP wave,which follows P in about 200 s.Since P waves are crucial for modeling earthquake processes,we propose an iterative method to separate...  相似文献