安徽黄山地区侏罗纪—白垩纪层序地层学特征   总被引：5，自引：0，他引：5  

余心起  王德恩 《现代地质》2001,15(1):27-34

通过 1∶ 5万区域地质调查工作对屯溪—休宁盆地、歙县洪琴盆地、绩溪华阳盆地、祁门盆地各类陆相沉积建造的沉积环境、沉积相、陆相沉积体系域进行了分析描述 ,将侏罗纪—白垩纪地层划分为四级地层层序 ,在层序地层学分析的基础上 ,建立了初步的红盆地层格架  相似文献   

淮安芒硝资源开发现状与发展对策     

高德云  李有才等 《江苏地质》2001,25(1):50-53

淮安芒硝资料的开发利用已使基我国东部新崛起的开采与加工基地，但问题也随之逐渐显现出来，主要是缺乏通盘规划、盲目扩大生产规模、污染环境以及勘查和基础设施跟不上等。就以上问题，作者对淮安芒硝开发提出了相应的对策与建议。  相似文献   

超细白云石矿粉润湿接触角的测定   总被引：9，自引：0，他引：9  

艾德生  李庆丰等 《岩矿测试》2001,20(2):97-99

根据Washburn方程，采用毛细管上升法，自行设计了简单的实验装置。提出了相对润湿接触角的概念，测定了3个超细CaCO3粉体在水中的润湿接触角。  相似文献   

Trials for the construction of a cement solidified retaining structure in a domestic landfill site using deep soil mixing     

M. S. De Silva  N. J. O'Riordan  L. N. Parry 《Engineering Geology》2001,60(1-4):49-60

This paper describes the trials undertaken within a domestic landfill site to assess the feasibility of constructing a cement solidified retaining structure using deep soil mixing. The trials consisted of individual columns extending to the full depth of the landfill, each using different concrete mixes and mixing auger configurations to assess the most successful combinations to achieve full depth, followed by the construction of two trial blocks incorporating several different concrete mixes. The trial blocks were constructed to evaluate the most effective concrete and auger combinations required to construct the retaining structure which if built would be approximately 150 m in length, 15 m deep and 10 m wide.

Grout cube strength has been measured during column installation and post construction the columns were exhumed and core samples taken for laboratory analysis of compressive strength, permeability, freeze/thaw and long-term immersion tests.

The trials have met with only moderate success and indicate that a combination of depth and a difficult substrate as is likely to be encountered in older landfills will severely hinder the process of column installation. No amount of previous characterisation can determine the conditions likely to be encountered at a particular location in such a heterogeneous material.

It is suggested that the calculation of likely success rate for column installation and construction of a large retaining structure can be based on the failure rate of cable percussion boreholes during site investigation. If the failure is greater than 15% the technique is unlikely to be viable.  相似文献   

Mössbauer study of synthetic Mg0.22Fe0.78SiO3 clinopyroxene     

S. G. Eeckhout  E. De Grave  C. A. McCammon  R. Vochten 《Mineralogy and Petrology》2001,73(4):235-245

Summary  Transmission M?ssbauer spectra of synthetic Ca-free P2₁/c Mg_0.22Fe_0.78SiO₃ clinopyroxene were collected at temperatures in the range 4.2 to 745 K and in an external magnetic field of 60 kOe at 180 K. The magnetic order-disorder transition temperature was determined by M?ssbauer thermoscanning to be 21 ± 3 K. Above this temperature, all M?ssbauer spectra consist of a superposition of two doublets, respectively produced by Fe²⁺ ions at an almost regular octahedral M1 site and at a more distorted octahedral M2 site. The temperature variation of the Fe²⁺ center shifts were analyzed using the Debye model for the lattice vibrations. The characteristic M?ssbauer temperatures were found to be 356 K ± 35 K for M1 and 333 K ± 25 K for M2. From the external field (60 kOe) M?ssbauer spectrum recorded at 180 K, the principal component V _zz of the electric field gradient (EFG) was determined to be positive for both sites but precise values for the magnitudes of the asymmetry parameters η of the EFG could not be determined. The temperature variations of the M1 and M2 quadrupole splittings ΔE _Q(T ) are consistent with the higher distortion of the M2 octahedra. Using the crystal-field model to interpret ΔE _Q(T ), the energy gaps δ₁ and δ₂ of the first excited electronic states within the ⁵D orbital term were estimated to be 410 ± 50 cm⁻¹ and 730 ± 50 cm⁻¹ for M1, and δ₁ = 1050 ± 75 cm⁻¹ for M2. Received May 29, 2000;/revised version accepted July 13, 2001  相似文献   

Grain size reduction by dynamic recrystallization: can it result in major rheological weakening?     

J. De Bresser  J. Ter Heege  C. Spiers 《International Journal of Earth Sciences》2001,90(1):28-45

It is widely believed that grain size reduction by dynamic recrystallization can lead to major rheological weakening and associated strain localization by bringing about a switch from grain size insensitive dislocation creep to grain size sensitive diffusion creep. Recently, however, we advanced the hypothesis that, rather than a switch, dynamic recrystallization leads to a balance between grain size reduction and grain growth processes set up in the neighborhood of the boundary between the dislocation creep field and the diffusion creep field. In this paper, we compare the predictions implied by our hypothesis with those of other models for dynamic recrystallization. We also evaluate the full range of models against experimental data on a variety of materials. We conclude that a temperature dependence of the relationship between recrystallized grain size and flow stress cannot be neglected a priori. This should be taken into account when estimating natural flow stresses using experimentally calibrated recrystallized grain size piezometers. We also demonstrate experimental support for the field boundary hypothesis. This support implies that significant weakening by grain size reduction in localized shear zones is possible only if caused by a process other than dynamic recrystallization (such as syntectonic reaction or cataclasis) or if grain growth is inhibited.  相似文献   

Potential Tsunami Hazard Associated with the Kerepehi Fault,Firth of Thames,New Zealand     

Chick  L. M.  De Lange  W. P.  Healy  T. R. 《Natural Hazards》2001,24(3):309-318

Geophysical data have identified four submarine segments of the Kerepehi Fault, roughly bisecting a back-arc rift (Hauraki Rift). These segments have been traced through the shallow waters of the Firth of Thames, which lies at the southern end of the Hauraki Gulf, New Zealand. No historical or paleotsunami data are available to assess the tsunami hazard of these fault segments.Analysis of the fault geometry, combined with paleoseismic data for three further terrestrial segments of the Fault, suggest Most Credible Earthquake (MCE) moment magnitudes of 6.5–7.1. Due to the presence of thick deposits of soft sediment, and thesemi-confined nature of the Firth, the MCE events are considered capable of generating tsunami or tsunami-like waves. Two numerical models (finite element and finite difference), and an empirical method proposed by Abe (1995), were used to predict maximum tsunami wave heights. The numerical models also modelled the tsunami propagation.The MCE events were found not to represent a major threat to the large metropolitan centre of Auckland City (New Zealand's largest population centre). However, the waves were a threat to small coastal communities around the Firth, including the township of Thames, and 35,000 ha of low-lying land along the southern shores of the Firth of Thames.The Abe method was found to provide a quick and useful method of assessing the regional tsunami height. However, for sources in water depths < 25 m the Abe method predicted heights 2–4 times larger than the numerical models. Since the numerical models were not intended for simulating tsunami generation in such shallow water, the Abe results are probably a good guide to the maximum wave heights.  相似文献   

New constraints on the pyroclastic eruptive history of the Campanian volcanic Plain (Italy)   总被引：2，自引：0，他引：2  

B. De Vivo  G. Rolandi  P. B. Gans  A. Calvert  W. A. Bohrson  F. J. Spera  H. E. Belkin 《Mineralogy and Petrology》2001,73(1-3):47-65

Summary The ∼ 150 km³ (DRE) trachytic Campanian Ignimbrite, which is situated north-west of Naples, Italy, is one of the largest eruptions in the Mediterranean region in the last 200 ky. Despite centuries of investigation, the age and eruptive history of the Campanian Ignimbrite is still debated, as is the chronology of other significant volcanic events of the Campanian Plain within the last 200–300 ky. New ⁴⁰Ar/³⁹Ar geochronology defines the age of the Campanian Ignimbrite at 39.28 ± 0.11 ka, about 2 ky older than the previous best estimate. Based on the distribution of the Campanian Ignimbrite and associated uppermost proximal lithic and polyclastic breccias, we suggest that the Campanian Ignimbrite magma was emitted from fissures activated along neotectonic Apennine faults rather than from ring fractures defining a Campi Flegrei caldera. Significantly, new volcanological, geochronological, and geochemical data distinguish previously unrecognized ignimbrite deposits in the Campanian Plain, accurately dated between 157 and 205 ka. These ages, coupled with a xenocrystic sanidine component > 315 ka, extend the volcanic history of this region by over 200 ky. Recent work also identifies a pyroclastic deposit, dated at 18.0 ka, outside of the topographic Campi Flegrei basin, expanding the spatial distribution of post-Campanian Ignimbrite deposits. These new discoveries emphasize the importance of continued investigation of the ages, distribution, volumes, and eruption dynamics of volcanic events associated with the Campanian Plain. Such information is critical for accurate assessment of the volcanic hazards associated with potentially large-volume explosive eruptions in close proximity to the densely populated Neapolitan region. Received August 1, 2000; accepted November 2, 2000  相似文献   

Numerical model simulations of boundary-layer dynamics during winter conditions     

D. Melas  T. Persson  H. De Bruin  S.-E. Gryning  E. Batchvarova  C. Zerefos 《Theoretical and Applied Climatology》2001,70(1-4):105-116

Summary  A mesoscale numerical model, incorporating a land-surface scheme based on Deardorffs’ approach, is used to study the diurnal variation of the boundary layer structure and surface fluxes during four consecutive days with air temperatures well below zero, snow covered ground and changing synoptic forcing. Model results are evaluated against in-situ measurements performed during the WINTEX field campaign held in Sodankyl?, Northern Finland in March 1997. The results show that the land-surface parameterization employed in the mesoscale model is not able to reproduce the magnitude of the daytime sensible heat fluxes and especially the pronounced maximum observed in the afternoon. Additional model simulations indicate that this drawback is to a large extent removed by the implementation of a shading factor in the original Deardorff scheme. The shading factor, as discussed in Gryning et al. (2001), accounts for the fact that in areas with sparse vegetation and low solar angles, both typical for the northern boreal forests in wintertime, absorption of direct solar radiation is due to an apparent vegetation cover which is much greater than the actual one (defined as the portion of the ground covered by vegetation projected vertically). Moreover, the observed asymmetry in the diurnal variation of the sensible heat flux indicates that there might be a significant heat storage in the vegetation. The implementation of an objective heat storage scheme in the mesoscale model explains part of the observed diurnal variation of the sensible heat flux. Received November 12, 1999 Revised October 4, 2000  相似文献   

International Association of Geomorphologists Newsletter No. 18 (3/2001)     

Paul Williams  Selma Simes De Castro  Janet Hooke  Wang Ying  Vít Vilímek  Karl‐Heinz Schmidt  Anto Raukas  Tsuguo Sunamura  Algimantas Cesnulevicios  Irasema Alcntara‐Ayala  James P. Terry  Milos Stankoviansky  Carol P. Harden 《地球表面变化过程与地形》2001,26(12):1353-1360

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