Neoproterozoic SHRIMP U–Pb zircon ages of silica-rich Dokhan Volcanics in the North Eastern Desert,Egypt     

Christoph Breitkreuz  Hassan Eliwa  Ibrahim Khalaf  Khaled El Gameel  Benjamin Bühler  Sergei Sergeev  Alexander Larionov  Mamoru Murata 《Precambrian Research》2010

Chronology of Neoproterozoic volcanosedimentary successions remains controversial for many regions of the Arabian–Nubian Shield, including the Dokhan Volcanics of NE Egypt. New U–Pb zircon SHRIMP ages have been obtained for 10 silica-rich ignimbrites and two subvolcanic dacitic bodies, mapped as Dokhan Volcanics, from the North Eastern Desert of Egypt. Crystallization ages range between 592 ± 5 and 630 ± 6 Ma (Early Ediacaran). Apparently, the late consolidation of the Arabian–Nubian Shield was accompanied by the evolution of isolated volcanic centres and basin systems which developed during a period of approx. 40 Ma, independently in space and time and probably under changing tectonic regimes. The obtained age data together with other previously published reliable ages for Dokhan Volcanics suggest two main pulses of volcanic activity: 630–623 Ma and 618–592 Ma. Five samples contain inherited zircons, with ages of 669, 715–746, 847 and 1530 Ma, supporting models that North Eastern Desert crust is mainly juvenile Neoproterozoic crust.  相似文献   

Active tectonics and strain partitioning along dextral fault system in Central Iran: Analysis of geomorphological observations and geophysical data in the Kashan region     

Farshad Jamali  Khaled Hessami  Manoochehr Ghorashi 《Journal of Asian Earth Sciences》2011,40(4):1015-1025

This paper uses high-resolution images and field investigations, in conjunction with seismic reflection data, to constrain active structural deformation in the Kashan region of Central Iran. Offset stream beds and Qanats indicate right-lateral strike slip motion at a rate of about 2 mm/yr along the NW–SE trending Qom-Zefreh fault zone which has long been recognized as one of the major faults in Central Iran. However, the pattern of drainage systems across the active growing folds including deep incision of stream beds and deflected streams indicate uplift at depth on thrust faults dipping SW beneath the anticlines. Therefore, our studies in the Kashan region indicate that deformation occurs within Central Iran which is often considered to behave as a non-deforming block within the Arabia–Eurasia collision zone. The fact that the active Qom-Zefreh strike-slip fault runs parallel to the active folds, which overlie blind thrust faults, suggests that oblique motion of Arabia with respect to Eurasia is partitioned in this part of Central Iran.  相似文献   

Assessing mariculture water quality with the structural and functional characteristics of a ciliate community     

�����  �����  ������ 《中国海洋湖沼学报》2011,29(1):128-135

Ciliated protozoa play important roles in micro-ecosystems, especially in marine biotopes. However, few studies have been carried out on the periphytic, or aufwuch, forms in mariculture waters so far. In this study, we sampled periphytic ciliate communities in two closed mariculture ponds (ponds CP1 and CP2) and a natural seawater reservoir (pond RP) using a glass slide method to evaluate their colonizing processes and general ecological features, as well as their application as water quality indicators. We analyzed species compositions, structural parameters (species number, richness, diversity, evenness, abundance and dBP) and functional parameters (G, Seq and T90%). Pond RP was characterized by higher levels of structural parameters (except for abundance and dBP) and more equal proportion of the major taxonomic groups. The values of Seq were significantly higher in pond RP and similar in both pond CP1 and CP2. It was also demonstrated that environmental factors, including NO2-H, NO3-H, NH3-H, soluble reactive phosphate, temperature and pH, were the first principal factors affecting the communities. Among them, temperature and chemical factors were all significantly and negatively correlated with species number (P<0.01), richness (P<0.01), diversity (P<0.01), and positive correlated with abundance (P<0.01). Opposite correlations between pH and structural parameters were observed. This study showed that there were significant differences in species composition, structural parameters and functional parameters of the periphytic ciliate communities among the ponds, which were in agreement with the water quality. Results of this study confirmed the periphytic ciliate communities to be useful bioindicators of water quality in intensive mariculture waters.  相似文献   

Population dynamics of marine ciliate Euplotes vannus (Protozoa, Ciliophora) in different artificial seawaters     

�����  ����׳  ����  ��ɺ 《中国海洋湖沼学报》2011,29(1):109-117

To study population dynamics of marine ciliates in different artificial seawaters (ASW), the population growth dynamics of a common marine ciliate Euplotes vannus were investigated using beef extract media and rice media for five types of ASW and natural seawater (NSW). The results show that: (1) the population growth rate was in the order of NSW>Flack ASW>Nakamula ASW>Schmadz ASW>Oshima ASW>Subow ASW and was considerably higher in rice media than in beef extract media (apart from Subow ASW); (2) the maximum density of E. vannus in stationary phase in each treatment was ranked as Flack ASW>Nakamula ASW>Schmadz ASW>NSW>Oshima ASW>Subow ASW, and was again higher in rice media than in beef extract media (except for Subow ASW); (3) the exponential and stationary phases were longer in rice media than in beef extract media; (4) strains of E. vannus that had been domesticated for >1 year in ASW grew significantly slower, with lower maximum density and longer stationary phase than those isolated and maintained in NSW. It was demonstrated that: (1) E. vannus may grow well in Flack, Nakamula and Schmads ASW compared with NSW (mainly in terms of growth rate); and (2) Oshima ASW is the preferred choice for stock cultures of E. vannus, but the ASWs Flack, Nakamula and Schmadz are preferred for mass culture. These findings suggest that these three ASWs are effective for the cultivation of marine protozoa for experimental studies on ecology, toxicology and molecular biology.  相似文献   

Phylogenetic relationships within the genus Aspidisca (Protozoa, Ciliophora, Euplotida) revealed by ITS1-5.8S-ITS2 region sequences     

�ƽ�  ������  ����  ��΢�� 《中国海洋湖沼学报》2011,29(2):277-283

The internal transcribed spacer regions (ITS1 and ITS2) and 5.8S rRNA genes were sequenced in six populations of four Aspidisca species, namely A. leptaspis, A. orthopogon, A. magna and A. aculeata. Phylogenetic trees were constructed by means of Bayesian inference (BI), Maximum Parsimony (MP), Neighbor-Joining (NJ), and Maximum Likelihood (ML) to assess the inter- and intra-species relationships within the genus Aspidisca. All trees show similar topologies with stable supports and indicate that: (1) four well known groups, i.e., Oligotrichia, Stichotrichia, Choreotrichia and Hypotrichia, are distinctly outlined within the class Spirotrichea, and all are monophyletic other than Hypotrichia; (2) members of Aspidisca can be distinguished well, based on the ITS1-5.8S-ITS2 region sequences, and A. leptaspis and A. magna shared a closer relationship than other species; (3) Aspidisca and Euplotes branch early in the subclass Hypotrichia. To compare the phylogenetic relationships based on different genes, SSU rRNA trees were also constructed with nearly the same species inclusion, which revealed different topologies of inter-species, inter-genera and inter-subclasses.  相似文献   

Selection of the best fit flood frequency distribution and parameter estimation procedure: a case study for Tasmania in Australia   总被引：1，自引：1，他引：0  

Khaled Haddad  Ataur Rahman 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(3):415-428

Selection of a flood frequency distribution and associated parameter estimation procedure is an important step in flood frequency analysis. This is however a difficult task due to problems in selecting the best fit distribution from a large number of candidate distributions and parameter estimation procedures available in the literature. This paper presents a case study with flood data from Tasmania in Australia, which examines four model selection criteria: Akaike Information Criterion (AIC), Akaike Information Criterion—second order variant (AIC_c), Bayesian Information Criterion (BIC) and a modified Anderson–Darling Criterion (ADC). It has been found from the Monte Carlo simulation that ADC is more successful in recognizing the parent distribution correctly than the AIC and BIC when the parent is a three-parameter distribution. On the other hand, AIC and BIC are better in recognizing the parent distribution correctly when the parent is a two-parameter distribution. From the seven different probability distributions examined for Tasmania, it has been found that two-parameter distributions are preferable to three-parameter ones for Tasmania, with Log Normal appears to be the best selection. The paper also evaluates three most widely used parameter estimation procedures for the Log Normal distribution: method of moments (MOM), method of maximum likelihood (MLE) and Bayesian Markov Chain Monte Carlo method (BAY). It has been found that the BAY procedure provides better parameter estimates for the Log Normal distribution, which results in flood quantile estimates with smaller bias and standard error as compared to the MOM and MLE. The findings from this study would be useful in flood frequency analyses in other Australian states and other countries in particular, when selecting an appropriate probability distribution from a number of alternatives.  相似文献   

Molecular phylogeny and species separation of five morphologically similar Holosticha-complex ciliates (Protozoa, Ciliophora) using ARDRA riboprinting and multigene sequence data     

高凤  伊珍珍  龚骏  宋微波 《中国海洋湖沼学报》2010,28(3):542-548

  相似文献   

Temporal population dynamics of dinoflagellate Prorocentrum minimum in a semi-enclosed mariculture pond and its relationship to environmental factors and protozoan grazers     

许恒龙  朱明壮  姜勇 《中国海洋湖沼学报》2010,28(1):75-81

The ecological processes and interrelationships between protists, either autotrophic or heterotrophic, and environmental factors in mariculture ponds are largely unknown. This study investigated the temporal dynamics of potentially harmful dinoflagellate, Prorocentrum minimum (Pavillard) Schiller, and its relationship to physico-chemical factors and protozoan grazers over a complete cycle in a semi-enclosed shrimp-farming pond near Qingdao, Northern China. P. minimum occurred frequently in low numbers from June to August, followed by a sharp increase from the middle of August, reaching a single maximum peak value of 2.2×10⁵ cells L⁻¹ in October. Temporal variation in abundance was positively correlated with dissolved nitrogen, but showed a significant inverse relationship to abundance of the dominant ciliates, Tintinnopsis lohmanni and Askenasia stellaris. The results provide statistical evidence that the number of P. minimum increased with increasing nitrogen, and the suppression or shortening of algal bloom may be associated with protozoan grazers, such as Tintinnopsis lohmanni, in mariculture ponds.  相似文献   

Estuarine Habitat Assessment for Construction of a Submarine Transmission Line     

Amr Z. Hamouda  Khaled M. Abdel-Salam 《Surveys in Geophysics》2010,31(4):449-463

The present paper describes a submarine survey using the acoustic discrimination system QTC VIEW (Series V) as an exploratory tool to adjust final route alignment of a new pipeline. By using acoustic sound survey as an exploratory tool described in this paper to adjust final route alignment of a new pipeline to minimize the environmental impact caused and ultimately to avoid any mitigation measures. The transmission pipeline extended from the shore line of Abu-Qir Bay, on the Mediterranean Sea in Egypt, out to 70 nautical miles at sea (60 m water depth). Four main surface sediment types were defined in the study area, namely fine sand, silty sand, silt and clay. Results of the acoustic classification revealed four acoustic classes. The first acoustic class corresponded to fine sand, absence of shell debris and very poor habitats characteristics. The second acoustic class is predominant in the study area and corresponds to the region occupied by silt. It is also characterized by intermediate diversity of macrobenthic invertebrate community which is mainly characterized by polychaeta. The third acoustic class is characterized by silt to silty clay. It is characterized by a high diversity of macrobenthic invertebrate community which is mainly polychaeta with an intermediate diversity of gastropoda and bivalvia. The final acoustic class is characterized by clay and high occurrence of shell debris of gastropoda, bivalvia and polychaeta.  相似文献   

Azimuthal anisotropy analysis of walkaround vertical seismic profiling vertical seismic profiling: a case study from Saudi Arabia     

Khaled Al Dulaijan  John C. Owusu  Douglass C. Weber 《Geophysical Prospecting》2012,60(6):1082-1094

Understanding fracture orientations is important for optimal field development of fractured reservoirs because fractures can act as conduits for fluid flow. This is especially true for unconventional reservoirs (e.g., tight gas sands and shale gas). Using walkaround Vertical Seismic Profiling (VSP) technology presents a unique opportunity to identify seismic azimuthal anisotropy for use in mapping potential fracture zones and their orientation around a borehole. Saudi Aramco recently completed the acquisition, processing and analysis of a walkaround VSP survey through an unconventional tight gas sand reservoir to help characterize fractures. In this paper, we present the results of the seismic azimuthal anisotropy analysis using seismic traveltime, shear‐wave splitting and amplitude attenuation. The azimuthal anisotropy results are compared to the fracture orientations derived from dipole sonic and image logs. The image log interpretation suggests that an orthorhombic fracture system is present. VSP data show that the P‐wave traveltime anisotropy direction is NE to SW. This is consistent with the cemented fractures from the image log interpretation. The seismic amplitude attenuation anisotropy direction is NW to SE. This is consistent with one of the two orientations obtained using transverse to radial amplitude ratio analysis, with the dipole sonic and with open fracture directions interpreted from image log data.  相似文献