The Main Ostrava Whetstone: composition, sedimentary processes, palaeogeography and geochronology of a major Mississippian volcaniclastic unit of the Upper Silesian Basin (Poland and Czech Republic)     

Jakub Jirásek  Lada Hýlová  Martin Sivek  Janusz Jureczka  Karel Martínek  Ivana Sýkorová  Mark Schmitz 《International Journal of Earth Sciences》2013,102(4):989-1006

The Main Ostrava Whetstone (MOW) is an important lithostratigraphic horizon of the Late Carboniferous sedimentary fill of the late Palaeozoic foreland Upper Silesian Basin. It is the largest and best-identified volcanogenic horizon in the basin, reaching thicknesses of 15.3 m and occupying an area of ca 2,973 km² and a volume after lithification of 9.24 km³. It consists of volcanic materials transported to the basin probably by an aeolian process. Just after sedimentation, these materials were redeposited a short distance away in a shallow water environment. Granularity corresponds to a range from argillaceous siltstones to fine-grained sandstones. The components are dominated by glass shards replaced by clay minerals (mixed illite–smectite structures) in addition to quartz of volcanogenic and terrigenous origins. Sanidine and a plagioclase close to albite are also present. The sedimentary structures, micro-structures and composition of the MOW indicate variable and dynamic hydrodynamic conditions. The MOW represents a series of flooding events, which could be connected with unusual rainfall. Such major flooding events were most likely induced by volcanic eruptions. The available drill-core log data were used to construct a digital model of the whetstone, which showed an east–west zonality in the thicknesses, with the majority being synsedimentary. CA-TIMS U–Pb dating the volcanogenic zircons yields an age of 327.35 ± 0.15 Ma. The source location of the volcanogenic material is not clear; however, it is presumed to have been located in the west of the Upper Silesian Basin.  相似文献   

Relationships between the North Atlantic Oscillation index and temperatures in Europe in global climate models     

Romana Beranová  Jan Kyselý 《Studia Geophysica et Geodaetica》2013,57(1):138-153

The study evaluates relationships between the North Atlantic Oscillation (NAO) index and winter temperatures (including indices of extremes) over Europe in an ensemble of transient simulations of current global climate models (GCMs). We focus on identification of areas in which the NAO index is linked to winter temperatures and temperature extremes in simulations of the recent climate (1961–2000), and evaluate how these relationships change in climate change scenarios for the late 21st century (2071–2100). Most GCMs are able to reproduce main features of the observed links. The NAO index is more important for cold than warm extremes, which is also reproduced by the GCMs. However, all GCMs underestimate the magnitude of the NAO influence on cold extremes when averaged over northern and western Europe. For future scenarios, the links between the NAO and temperatures are mostly analogous to those in the recent climate, except for one GCM (CM3) in which the influence of the NAO on temperature almost disappears over whole Europe. This suggests that future scenarios from this particular GCM should be evaluated with caution. The NAO index is found to represent a useful covariate that explains an important fraction of variability of cold extremes in winter, and its incorporation into extreme value models for daily temperatures (and their possible changes under climate change) may improve performance of these models and reliability of estimates of extremes and their uncertainty.  相似文献   

The Amazon River headstream area in the Cordillera Chila,Peru: hydrographic,hydrological and glaciological conditions     

Bohumír Janský  Zbyněk Engel  Jan Kocum  Luděk Šefrna  Julius Česák 《水文科学杂志》2013,58(1):138-151

Abstract

The source of the world's largest river has fascinated scientists and adventurers for a long time. Extensive studies have been undertaken in the unexplored Llogueta River valley, Cordillera Chila, to identify the main stream of the Amazon River. Analysis of the Lloqueta River network and measurements of its hydrographic and hydrometric characteristics are presented in this study. On the basis of the acquired data, the northern hillside of the Cordillera Chila massif, concretely the basins of four mountainous courses—the Carhuasanta, Apacheta, Ccaccansa and Sillanque rivers—should be regarded as the headwaters territory of the Amazon River. Factors influencing the river system—glaciers and soils—were examined for each catchment. Glacier retreat in the last 50 years has left perennial snowfields only in the highest part of the study area, resulting in modification of the headwater runoff regimes. Preliminary results are afforded by the continual automatic water-level monitoring of the Lloqueta River since June 2008. Our investigations have determined that all types of soil in the area could be classified into two main categories: hydromorphic soils or poorly developed cryic soils.

Citation Janský, B., Engel, Z., Kocum, J., ?efrna, L. & ?esák, J. (2011) The Amazon River headstream area in the Cordillera Chila, Peru: hydrographical, hydrological and glaciological conditions. Hydrol. Sci. J. 56(1), 138–151.  相似文献   

Geochemical evidence for peat bog contribution to the streamflow generation process: case study of the Vltava River headwaters,Czech Republic     

Jan Kocum  Filip Oulehle  Bohumír Janský  František Bůzek  Jakub Hruška  Lukáš Vlček 《水文科学杂志》2013,58(14):2579-2589

ABSTRACT

A geochemical approach using stable oxygen isotopes was used to understand streamflow generation processes in the highly peaty catchment of the Rokytka Brook in the headwaters of the Vltava River, Czech Republic. The contribution of water from peat bog areas to the total surface runoff was assessed using a hydrological time series, as well as geochemical, hydrochemical and isotope-hydrological approaches for unit hydrogram separation by means of anion deficiency. Using data from the hydrological year 2008, the role of an existing peat bog in the runoff formation dynamics of the Rokytka Brook catchment was determined, and the hydrological cycle was described and assessed using stable ¹⁸O/¹⁶O isotopes. The research findings strongly support the fact that peatland areas within the studied catchment do not significantly communicate hydraulically with surface streams, and their hydrological function in this region is insignificant.