Flood disaster in Taihu Basin,China: causal chain and policy option analyses     

Wang Liang  Cai Yongli  Chen Hongquan  Dag Daler  Zhao Jingmin  Yang Juan 《Environmental Earth Sciences》2011,63(5):1119-1124

Taihu Lake is at the densely populated region of the eastern coast of China. Taihu Basin is one of the most developed regions of China. The frequency of flood disaster in Taihu Basin has been increasing in the recent years, resulting in more drowned areas and economic loss. It is shown that flood disaster is the most serious problems in Taihu Lake and Taihu Basin. Mitigation of flood problems and return to sustainability has now been given high attention and are prioritized in the Chinese national policies. This paper describes the state of the flood disaster in the Taihu Basin, examines the root causes for flood disaster, demonstrates by examples how these analyses known as transboundary diagnostic analysis can be used to develop policy options that can help predict and reduce the flood disaster based on past and current measures and policy.  相似文献   

Drag force on a vegetation field due to long-crested and short-crested nonlinear random waves     

Dag Myrhaug  Lars Erik Holmedal 《Coastal Engineering》2011

This paper provides a practical method for estimating the drag force on a vegetation field exposed to long-crested (2D) and short-crested (3D) nonlinear random waves. This is achieved by using a simple drag formula together with an empirical drag coefficient given by Mendez et al. (1999), in conjunction with a stochastic approach. Here the waves are assumed to be a stationary narrow-band random process. Effects of nonlinear waves are included by adopting the Forristall (2000) wave crest height distribution representing both 2D and 3D random waves.  相似文献   

Dynamic Versus flexural Controls of Late Cretaceous Western Interior Basin, USA     

LIU Shaofeng  Dag NUMMEDAL  LIU Lijun 《《地质学报》英文版》2013,87(Z1):572-573

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Fluid inclusions as a tool to constrain the preservation conditions of sub-seafloor cryptoendoliths     

M. Ivarsson  C. Broman  S. Lindblom  N.G. Holm 《Planetary and Space Science》2009,57(4):477-490

The combination of fluid inclusion analyses and microfossil analyses is an excellent method to study the preservation process of deep sub-seafloor microorganisms. By studying fluid inclusions in the same mineral phases as microfossils, it is possible to reconstruct the conditions that prevailed when the microorganisms where entombed and to put them in a geological and environmental context.This study has been performed on carbonate and gypsum veins in drilled basalt samples from three seamounts belonging to the Emperor Seamounts in the Pacific Ocean: Detroit, Nintoku and Koko Seamounts. The study show that variations in salt composition (MgCl₂, NaCl, KCl and CaCl₂) and salinity (2.1 and 10.5 eq. wt% NaCl) of the hydrothermal fluids do not have an influence on the occurrence of microfossils throughout the samples. The microorganisms were trapped and entombed at minimum temperatures of ∼130 °C which implies that the microorganisms could have existed at temperatures of ∼130 °C for shorter periods of time. The microorganisms were entrapped at shallow-marine to submarine conditions and the entrapment of the microorganisms occurred relatively late compared to the volcanic activity.  相似文献   

Five centuries of Stockholm winter/spring temperatures reconstructed from documentary evidence and instrumental observations   总被引：1，自引：0，他引：1  

Lotta Leijonhufvud  Rob Wilson  Anders Moberg  Johan Söderberg  Dag Retsö  Ulrica Söderlind 《Climatic change》2010,101(1-2):109-141

Historical documentary sources, reflecting different port activities in Stockholm, are utilised to derive a 500-year winter/spring temperature reconstruction for the region. These documentary sources reflect sea ice conditions in the harbour inlet and those series that overlap with the instrumental data correlate well with winter/spring temperatures. By refining dendroclimatological methods, the time-series were composited to a mean series and calibrated (1756–1841; r ²?=?66%) against Stockholm January–April temperatures. Strong verification was confirmed (1842–1892; r ²?=?60%; RE/CE?=?0.55). By including the instrumental data, the quantified (QUAN) reconstruction indicates that recent two decades have been the warmest period for the last 500 years. Coldest conditions occurred during the 16th/17th and early 19th centuries. An independent qualitative (QUAL) historical index was also derived for the Stockholm region. Comparison between QUAN and QUAL shows good coherence at inter-annual time-scales, but QUAL distinctly appears to lack low frequency information. Comparison is also made to other winter temperature based annually resolved records for the Baltic region. Between proxy coherence is generally good although it decreases going back in time with the 1500–1550 period being the weakest period—possibly reflecting data quality issues in the different reconstructions.  相似文献   

Composition and properties of glacigenic sediments in the southwestern Barents Sea     

Joar Sættem  Leif Rise  Dag Arne Westgaard 《Marine Georesources & Geotechnology》2013,31(3-4):229-255

Abstract

The composition and properties of glacigenic sediments in the southwestern Barents Sea are described based on data from 33 shallow boreholes (< 143 m below seabed) and 11 seabed cores (<4.2m below seabed). The cores are tied into a regional seismostratigraphic framework, illustrating the relationships between different boreholes.

A massive, muddy diamicton (silty, sandy clay with scattered gravel) is found in nearly all cores. Average clay content (<2 pm) of this lithology is about 38%, but varies between about 25% and 50%. Short intervals of finely laminated, waterlain sediments or gravelly sand are cored in a few occasions. A high content of sand and gravel in the cores from near the Norwegian coast shows an influence of sediment input from the mainland, while material eroded from sedimentary rocks dominates farther offshore.

The data presented on physical properties include undisturbed and remolded undrained shear strength, natural water content, bulk density, compressional sound velocity (P waves), Atterberg consistency limits, effective preconsolidation pressure, and consolidation coefficient.

Prediction of overconsolidation from seismic mapping of erosional surfaces is confirmed by the borehole cores. High compaction is found both in Weichselian and older deposits, with a general increase in compaction toward the east as well as toward shallower water. Cores that are “underconsolidated” at their present burial depth are also reported.

The average compressional sound velocity is about 1780 m/s for the borehole cores, 1550 m/s for the seabed cores, and increases with increasing shear strength and consolidation. Both horizontal and vertical sound velocities are measured in several cores, and although the data have a considerable scatter, a slightly aniso‐tropic sound velocity is indicated.  相似文献   

Geochronological,stable isotopes and fluid inclusion constraints for a premetamorphic development of the intrusive-hosted Björkdal Au deposit,northern Sweden     

K. Billström  C. Broman  E. Jonsson  C. Recio  A. J. Boyce  P. Torssander 《International Journal of Earth Sciences》2009,98(5):1027-1052

The Björkdal gold deposit, bound to a quartz vein system which is mainly hosted by a quartz-monzodioritic intrusion, is situated at the easternmost part of the 1.9 Ga Skellefte base metal district in the Fennoscandian shield. Three fluid stages may be distinguished, referred to as a “barren” stage, a main gold stage, and a remobilization stage, respectively. From oxygen and hydrogen isotope evidence, it is argued that fluids of different origins (magmatic and surface waters) penetrated the ore zone at the inferred stages, but regional metamorphic fluids appear essentially only to have redistributed elements. Early quartz veining took place during a pre-metamorphic stage at ca. 1.88 Ga, as evidenced by unradiogenic galena data and an Sm–Nd scheelite errorchron of 1,915 ± 32 Ma (MSWD = 0.25). Temporarily, the main ore-forming stage was closely related to the first barren stage and took place during a major uplift event close to 1.88 Ga. Although other source rocks cannot be totally ruled out, available isotope data (O, S, Sr and Pb) are seemingly consistent with the view that these elements, and by inference other ore elements, were derived from the host intrusion.  相似文献   

Book reviews     

W. Krumbein  U. Förstner  E. Plate  John Lewin  Georg Matthess  E. Löffler  Dag Nummedal  A. Zaporozec  G. Kunkel  Pierre Biays  Karl W. Butzer  J. Humlum  Gunnar Alexandersson  W. R. Stanley  Ernst Löffler  Åke Hillefors  Yrjö Vasari  E. M. Yates 《GeoJournal》1979,3(5):499-508

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Magmatic-hydrothermal fluids in the Pahtohavare Cu-Au deposit in greenstone at Kiruna,Sweden     

S. Lindblom  C. Broman  O. Martinsson 《Mineralium Deposita》1996,31(4):307-318

The Proterozoic Pahtohavare Cu-Au deposit is located in the greenstone belt near Kiruna, northern Sweden. The greenstone consists of mafic volcanic rocks with pillow lavas, mafic sills and albitized rocks, including tuffites, black schists and mafic sills, together with carbonates and mineralized zones. Mineralization occurs as impregnations, epigenetic quartz-rich breccias and fracture fillings with pyrite, chalcopyrite, pyrrhotite and gold in a complex tectonic environment. Fluid inclusions indicate an early formation of quartz and pyrite at temperatures initially near 500°C and a pressure of 2–2.4 kbar from a supersaturated aqueous solution of magmatic origin. In addition to halite cubes, daughter minerals of sylvite, calcite, hematite, graphite and two unknown phases are found. The main stage of chalcopyrite and gold deposition is characterized by aqueous fluids of variable salinity (up to 30 eq. wt.% NaCl including CaCl₂), at temperatures below 350°C and pressures between 1 and 2 kbar. A minor CO₂ phase with some N, accompanies this stage. Gold was transported as a chloride complex which destabilized due to an increase in pH (as a consequence of the CO₂ loss) as well as cooling and dilution of the solution. The ore deposition occurred as a result of mixing with a low salinity aqueous solution during tectonic fracturing with pressure fluctuations and CO₂ unmixing. Late oxidation of ores was caused by low to moderately saline (3 to 13 eq. wt.% NaCl) low temperature aqueous solutions.  相似文献   

Heat generation versus depth of crystallization for Norwegian monzonitic rocks     

Dag E. Ormaasen  Gunnar Raade 《Earth and Planetary Science Letters》1978,39(1):145-150

Thorium, U and K analyses by γ-ray spectrometry of monzonitic intrusives from Lofoten-Vesterålen (ca. 1800 m.y.), Bjerkreim-Sogndal (ca. 1000 m.y.) and the Oslo region (ca. 275 m.y.) are used to calculate values of radioactive heat generation. A strong negative correlation between heat generation and depth of crystallization is demonstrated, indicating that the chemical zoning of the continental crust with respect to Th and U is of a rather regional and regular character, and was probably firmly established at least 1800 m.y. ago. The K contents, in contrast to Th and U, show an increase with depths of crystallization for these rocks. This may be explained by considerations of the pressure dependence of the partition coefficients for these elements between minerals and magma, and the importance of a fluid phase as a transport medium for the incompatible elements Th and U. A positive correlation between K content and age of intrusion is discussed on a tentative basis.  相似文献