Meiobenthic Organisms as Indicators of Mixing Processes in the Baltic Surface Sediments*     

Janusz Pempkowiak  Joanna Kozuch  Maria Szymelfenig 《Marine Ecology》1996,17(1-3):175-179

Abstract. Two sediment cores were collected in the southern Baltic Sea and sliced into 1.0cm-thick layers. Sediments of each layer were analysed for activities of ²¹⁰Pb, ¹³⁷Cs, ¹³⁴Cs and for the density of meiobenthic organisms (meiofauna). Zones with the rapid mixing occur in the uppermost layers (0–3 cm) of the cores based on ^I34Cs profiles. The extent and density of meiofauna confirmed the rapid mixing and revealed layers with slow mixing (4–8 cm). Sedimentation rates were derived from ²¹⁰Pb profiles below the mixing zones (1.21 and 1.72 mm a-^I) and were confumed by ¹³⁷Cs distribution. Of twenty-one major meiofauna taxa commonly found in the Baltic sediments, three were present in the cores.  相似文献   

格列菲列岛的地质地球物理研究     

CHOI Suckwon  Woo Youngkyun  Koo Minho  Suh Mancheol  郝天珧  王谦身 《地球物理学进展》2003,18(2):283-286

本文是中、韩国际合作项目“黄海地质地球物理场特征研究”的一部分 .具体研究了格列菲列岛的基础地质问题及地球物理场特征 .格列菲列岛是由三个小岛组成的位于黄海中部的一组群岛 ,位于朝鲜半岛布格重力异常正值区 ,莫霍面埋深在 2 9km左右 .三个岛屿主要由安山集块岩构成 .安山集块岩是由大小不同的火成岩碎块和熔岩混合而成 .火成岩的碎块成分主要为石英岩、片岩、片麻岩、玄武岩、安山岩和流纹岩 .主要节理方向为NE10°～NE2 0°,倾角近乎垂直 ;另一组节理为NW70°～NW80° ,倾角也近垂直 .本研究为我们了解这个地区的基础地质情况 ,岩石物性和随后进行的黄海海域典型剖面的地球物理物性反演工作以及地质模型的建立 ,打下重要基础 .  相似文献   

Towards an Interpretation of Historical Droughts in Northern Nigeria     

Aondover Tarhule  Ming-Ko Woo 《Climatic change》1997,37(4):601-616

Both historical information on sub-Saharan droughts/famines and measured rainfall data from northern Nigeria were analysed. Their parallel existence since 1905 allows famine chronologies to be quantified from the rainfall series. It is found that the most disruptive historical famines occurred when the cumulative deficit of rainfall fell below 1.3 times the standard deviation of long-term mean annual rainfall for a particular place. Thus defined, rainfall droughts matched approximately 90% of the famine events chronicled for northern Nigeria. An attempt is made to utilise information obtained from this matching of events to interpret droughts which occurred before scientific measurements. Difficulties inherent in such interpretation are discussed.  相似文献   

Constraints of Housing Age and Migration on Residential Mobility     

Dowell Myers  S. Simon Choi  Seong Woo Lee 《The Professional geographer》1997,49(1):14-28

This paper investigates the role of housing age in constraining residential mobility, measured as the percent of households that have moved into their homes in the past 15 months. The leading explanation for why mobility rates differ so much among regions of the United States has been the overall level of growth. The present analysis shows that the growth effect operates through both the newness of population (migration) and the newness of housing available for occupancy by all local residents. The posited explanation for this housing age effect is that progressively older units contain increasingly settled occupants, yielding fewer opportunities for in-movers in areas with older housing. It is empirically demonstrated that households in older housing have lower likelihood of recent mobility even after controlling for age, tenure, migration status, and state location of residence. The analysis reveals the temporal interdependency of mobility, migration, person age, and housing age.  相似文献   

Seismic hazard assessment in the Ionian Islands based on observed macroseismic intensities     

Joanna E. Papoulia  Dario Slejko 《Natural Hazards》1996,14(2-3):179-187

Catalogues of actual observed intensities are constructed for three towns in the Ionian Islands. They are used for seismic hazard assessment and the results are compared with those obtained by standard approaches; that is, by statistics applied to the data computed from epicentral parameters. The results show that seismic hazard is better assessed using observed rather than computed data, but preparation of the local catalogue presents non-trivial difficulties.  相似文献   

The solar wind and the Sun–Earth link     

Prof.  Shadia Rifia Habbal Dr  Richard Woo 《Astronomy& Geophysics》2004,45(4):4.38-4.43

Plasma streams out from the Sun in the form of the solar wind. Shadia Rifai Habbal and Richard Woo examine the workings of this enigmatic link between the Earth and the Sun.  相似文献   

Aeolian abrasion and modes of fine particle production from natural red dune sands: an experimental study   总被引：3，自引：0，他引：3  

Joanna E. Bullard  Grant H. McTainsh†  Christa Pudmenzky† 《Sedimentology》2004,51(5):1103-1125

A series of experiments was conducted to determine the potential for aeolian abrasion of natural dune sands to produce fine particles (< 125 µm) by (1) the release of resident fines; (2) spalling, chipping and breakage of particles; and (3) the removal of grain surface coatings. Parent samples were obtained from the surfaces of four active continental dunes and abraded using a glass ‘test tube’ chamber for up to 120 h. The fine particles produced by this abrasion process were trapped at varying time intervals and subject to detailed particle‐size analyses using a Coulter Multisizer. The abrasion of untreated parent samples produced fine particles in one of two main size classes, < 10 µm and > 50 µm, but when the parent sample was sieved to exclude particles < 250 µm, relatively more material in the range 10–50 µm was produced. For unsieved parent samples, the size range associated with the dominant mode varied according to the length of the abrasion time. The coarsest mode (> 63 µm) was dominant during the first 16 h of abrasion, then became less significant and is thought to be associated with the release of resident fines into suspension. The finest mode (< 10 µm) was absent or very weak during the first 16 h of abrasion, then became more significant and, in some instances, dominated the distribution as abrasion continued. Removal of grain surface coatings is the main source of fine material < 10 µm, and this may be a significant source of fine material in areas where sands are dominated by subrounded and rounded particles. By comparison with previous studies of aeolian particle abrasion, these natural dune sands produced very low quantities of fine material (by weight), but their spatial extent makes them potentially a significant source of dust‐sized particles at the global scale.  相似文献   

Determination of the elastic modulus set of foliated rocks from ultrasonic velocity measurements   总被引：2，自引：0，他引：2  

Insun Song  Mancheol Suh  Yong-Kyun Woo  Tianyao Hao 《Engineering Geology》2004,72(3-4):293-308

Ultrasonic measurements of compressional and shear wave velocities under hydrostatic pressure up to 70 MPa were carried out on cylindrical specimens cored across and along the foliation planes. Our measurements revealed that the foliation of the metamorphic rocks induces a clear velocity anisotropy between two orthogonal directions; faster along the foliation plane and slower across the plane in most rock types. All velocity components monotonically increase with the confining pressure, probably due to the closure of microcracks distributed in rock specimens. We determined the complete set of dynamic moduli of foliated metamorphic rocks with two assumptions; transverse isotropy due to the foliation and ellipsoidal seismic energy propagation from a point source. The calculated elastic moduli referring to different directions could be valuable for the design of various engineering structures in planar textured rock mass.  相似文献   

Tectonic elements with South China affinity in the Korean Peninsula: new Early Jurassic palaeomagnetic data   总被引：1，自引：0，他引：1  

Koji Uno  Tae Woo Chang  Kuniyuki Furukawa 《Geophysical Journal International》2004,158(2):446-456

  相似文献   

Dust production and the release of iron oxides resulting from the aeolian abrasion of natural dune sands     

Joanna E. Bullard  Kevin White 《地球表面变化过程与地形》2005,30(1):95-106

Global dust trajectories indicate that signi?cant quantities of aeolian‐transported iron oxides originate in contemporary dryland areas. One potential source is the iron‐rich clay coatings that characterize many sand‐sized particles in desert dune?elds. This paper uses laboratory experiments to determine the rate at which these coatings can be removed from dune sands by aeolian abrasion. The coatings impart a red colour to the grains to which previous researchers have assigned variable geomorphological signi?cance. The quantities of iron removed during a 120 hour abrasion experiment are small (99 mg kg^?1) and dif?cult to detect by eye; however, high resolution spectroscopy clearly indicates that ferric oxides are released during abrasion and the re?ectance of the particles alters. One of the products of aeolian abrasion is ?ne particles (<10 µm diameter) with the potential for long distance transport. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献