Significance of pot and gutter casts in a Middle Triassic carbonate platform, Betic Cordillera, southern Spain   总被引：3，自引：0，他引：3  

A. Pérez-López 《Sedimentology》2001,48(6):1371-1388

Pot casts and gutter casts are described for the first time in the lower part of the Majanillos Formation, a Middle Triassic carbonate unit located in the External Zones of the Betic Cordillera (southern Spain). Their identification, as well as their relation to tempestites, enables the better interpretation of the depositional environments and the shoreline-to-offshore facies transition on the Anisian muddy carbonate ramp of the southern Iberian Massif. The Majanillos Formation contains three members, which become progressively more marly towards the top. Well-preserved pot and gutter casts and thin intercalations of calcarenite, which are interpreted as tempestites, are abundant in the lowest member. Above the pot and gutter casts, thicker calcarenite beds, which locally contain hummocky cross-stratification, predominate. Bioturbated nodular limestones are prevalent at the top of the member. The remaining succession, which records a long-term Triassic transgressive cycle, consists mostly of fine-grained limestones deposited in very shallow-marine environments. Calcarenitic sediments only accumulated within potholes and gutters in the nearshore. They developed during storms when strong currents transported sediment to the outer shelf, where it was deposited as tempestite beds. Pot and gutter casts characterize sedimentation in the bypass zone. It is concluded that storm deposits provide important constraints for the interpretation of palaeobathymetry; it is proposed that gutter casts display a trend of increasing width/thickness ratios towards the outer shelf. The identification of these structures in marine successions elsewhere should prove useful in the interpretation of depositional environments.  相似文献   

康定,东川两地段强震活动对比及在川滇强震预测中的意义     

黄圣睦 《地震研究》1993,16(3):239-245

本文提出了具有相似活动构造背景的强震多发段康定段和东川段。对两者历史强震迁移和与川滇大地震的紧密联系,作了较有说服力的多次震例证明,因而本文所论及的有关活动特征在川滇未来强震预测中有一定参考价值。  相似文献   

二维地震勘探变观量板图及其应用   总被引：1，自引：0，他引：1  

WANG Li-bin ZHANG Hai-ying REN Ri-chun LIU Hai-tao GAO Yuan Geophysical Prospecting Company of Coal Geology in Jilin Province  Changchun  China 《吉林大学学报(地球科学版)》2006,(Z2)

在以炸药为震源的二维地震勘探野外资料采集施工中,需要避开各种不能钻井放炮的障碍物,根据勘查区设计任务书的施工参数,可以画出变观量板图。变观量板图具有快速变观的作用,野外所遇到的不同距离的障碍物可以通过变观避开,给施工提供方便,变观量板图具有实际应用价值。  相似文献   

Micro-sequential contour blasting—how does it influence the surrounding rock mass?     

Agne P. Rustan 《Engineering Geology》1998,49(3-4):303-313

The optimal delay time between the contour holes in rock blasting has been studied by theoretical and empirical research in Sweden, regarding ground vibrations, increase in crack frequency, radial crack length and finally overbreak (half cast factor). The model test presented in this paper concerns controlled contour blasting in tunnelling and the full-scale blasts concern tunnelling, road cutting, and dimensional stone quarrying. The results indicate that the microsequential contour blasting technique (contour holes fired in sequence and with a delay in the order of 1–2 ms) is superior to simultaneous initiation both regarding blast-induced ground vibrations and crack frequency increase in the rock mass. Both these evaluation methods reflects the conditions deeper in the remaining rock mass. Simultaneous initiation, however, is superior to micro-sequential contour blasting both regarding the half cast factor and the length of radial cracks emanating from the blastholes. These two parameters are more related to the surface conditions after blasting. The industrial applications of this new knowledge are the use of micro-sequential contour blasting when ground vibrations are of greater concern than the contour, for example, in trench blasting or quarrying in urban areas, and the use of simultaneous initiation when an even rock surface is of high priority.  相似文献   

Some aspects of cast blasting techniques for dam construction     

G. R. Adhikari  R. N. Gupta 《Geotechnical and Geological Engineering》1989,7(4):301-313

Summary A proposal is under consideration to construct a dam on an experimental basis by a cast (or directional) blasting technique, DBT. The dam site is located at Bharari Khad, a tributary of the Sutlaz river in Himachal Pradesh. Site investigations have been completed and a large scale blast has been designed for construction of the experimental dam.The paper describes the basic design concept of DBT and application of throw and caving methods for construction of dams. The preliminary tests required to design the blasting pattern are detailed. The technique has a great potential because it reduces construction cost and time particularly in inaccessible mountain regions.  相似文献   

High-West and Low-East Distribution Patterns of Chlorophyll a, Primary Productivity and Diatoms in the Subarctic North Pacific Surface Waters, Midwinter 1996   总被引：1，自引：0，他引：1  

Akihiro Shiomoto  Hiroki Asami 《Journal of Oceanography》1999,55(4):493-503

We have determined chlorophyll a (Chla) concentration, primary productivity, cell density and species composition of diatoms, and the number of microzooplankton at the surface in the subarctic North Pacific in January 1996. The wet weight of copepods obtained by vertical tows from 150 m to the surface was also measured during the cruise. Chla concentration and primary productivity tended to be higher in the region west of 180°, the western subarctic North Pacific (WSNP), than east of 180°, the eastern subarctic North Pacific (ESNP). The same results were observed for the total diatom cell densities and for the genera Thalassiosira and Denticulopsis. Significant linear relationships were observed between the Thalassiosira cell density and Chla concentration and primary productivity, indicating that Thalassiosira contributes to the high-WSNP and low-ESNP distribution patterns of Chla concentration and primary productivity. Moreover, naked ciliate abundance tended to be lower in the WSNP than in the ESNP, whereas copepod biomass showed an inverse trend. Significantly negative Spearman rank correlations were found between the Thalassiosira cell density and the number of naked ciliates and between the number of naked ciliates and the wet weight of copepods. These results indicate that copepod grazing indirectly controls Thalassiosira cell density via predation on the naked ciliates. We conclude that the high copepod biomass in the WSNP is a factor controlling the high-WSNP and low-ESNP Thalassiosira abundance and hence Chla concentration and primary productivity patterns.  相似文献   

A preliminary discussion on the bio-metallogenesis of TI deposits in the low-temperature minerogenetic province of southwestern China     

Zhang Zhong  Zhang BaoGui  Hu Jing  Yao LinBo  Tian YiFu 《中国科学D辑(英文版)》2007,50(3):359-370

Starting with the research status of bio-metallogenesis of TI deposits and their geology, this work deals with the geological background of TI enrichment and mineralization and the mechanism of bio-metallogenesis of TI deposits, as exemplified by TI deposits in the low-temperature minerogenetic province. This research on the bio-metallogenesis of TI deposits is focused on the correlations between bio-enrichment and TI, the enrichment of TI in micro-paleo-animals in rocks and ores, bio-fossil casts in TI-rich ores, the involvement of bio-sulfur in minerogenesis and the enrichment of bio-genetic organic carbon in TI ores. Thallium deposits have experienced two ore-forming stages: syngenetic bio-enrichment and epigenetic hydrothermal reworking (or transformation). Owing to the intense epigenetic hydrothermal reworking, almost no bio-residues remain in syngenetically bio-enriched TI ores, thereby the TI deposits display the characteristics of hydrothermally reoworked deposits. Supported by the National Natural Science Foundation of China (Grant No. 40372047)  相似文献   

采用"二次剪球"法处理堵管事故的实践     

高卫国  吕尚顺 《福建地质》2001,20(3):141-143

在灌注桩施工过程中,常遇见有堵管事故发生,若能及时采用“二次剪球”法进行孔内接桩,就能稳妥地解决灌注桩施工中遇到的堵管事故。使工程保质保量,顺利完成。  相似文献   

蒸馏海水淡化产品水对铸铁材质腐蚀研究   总被引：1，自引：0，他引：1  

王晓玲  徐克  苏立永  张乾 《海洋技术学报》2011,30(1):99-102

分析了多级闪蒸海水淡化产品水水质特点,研究了淡化水对铸铁管网的腐蚀影响.利用稳定指数法、失重法、电化学分析和腐蚀产物的XRD检测等方法开展了实验研究.实验结果显示了淡化水对铸铁试片的腐蚀程度及淡化水对铸铁腐蚀产物的类型,可为淡化水进入市政管网提供参考.  相似文献   

对铬铁磨球组织选择的理论探讨     

张兰英 《广东海洋大学学报》1997,(2)

通过对磨球运动、受力状况和磨损机制及其影响因素的分析，提出了对磨球使用性能的要求；应用材料科学基本理论，重点探讨了铝铁磨球组织选择的方法、原则和依据。结论是：根据磨球的工况条件，准确判断磨球的磨损机制是合理选择磨球组织的前提。  相似文献