Magnetic anomaly maps of the Trans-European Suture Zone (TESZ) highlight the contrast between the highly magnetic crust of Baltica and the less magnetic terranes to the SW of the suture. Although the TESZ is imaged on gravity maps, anomalies related to postcollisional rifting and reactivated rift structures tend to dominate.
Seismic and potential field data have been used to construct 2
-D crustal models along three profiles crossing the Baltica–Avalonia suture in the southern North Sea (SNS). The first of these models lies along a transect assembled from reflection line GECO SNST 83-07 and refraction profile EUGENO-S 2; the other two models are coincident with MONA LISA profiles 1 and 2. Additional structural information and density information for the cover sequence is available from released wells, while magnetic susceptibility values are compatible with values measured from borehole core samples.
Magnetic anomalies related to the suture are interpreted as due to magnetic Baltican basement of the Ringkøbing-Fyn High dipping SW beneath nonmagnetic Avalonian basement underlying the western part of the SNS. Low-amplitude, long-wavelength magnetic anomalies occurring outboard of the suture are interpreted as due to a mid-crustal magnetic body, possibly a buried magmatic complex. This might represent the ‘missing’ arc related to inferred southward subduction of the Tornquist Sea, or an exotic element emplaced during the collision between Avalonia and Baltica. The present model supports an imbricated structure within Baltica as indicated by the latest reprocessing of the MONA LISA seismic data. 相似文献
The reservoir quality of Jurassic and Triassic fluvial and lacustrine-deltaic sandstones of the Yanchang Oil Field in the
Ordos Basin is strongly influenced by the burial history and facies-related diagenetic events. The fluvial sandstones have
a higher average porosity (14.8%) and a higher permeability (12.7 × 10−3 μm2) than those of the deltaic sandstones (9.8% and 5.8 ×10−3) μm2, respectively). The burial compaction, which resulted in 15% and 20% porosity loss for Jurassic and Triassic sandstones,
respectively, is the main factor causing the loss of porosity both for the Jurassic and Triassic sandstones. Among the cements,
carbonate is the main one that reduced the reservoir quality of the sandstones. The organic acidic fluid derived from organic
matter in the source rocks, the inorganic fluid from rock-water reaction during the late diagenesis, and meteoric waters during
the epidiagenesis resulted in the formation of dissolution porosity, which is the main reason for the enhancement of reservoir-quality. 相似文献
Rapid population growth in the upper Blue Nile basin has led to fast land-use changes from natural forest to agricultural land.This resulted in speeding up the soil erosion process in the highlands and increasing sedimentation further downstream in reservoirs and irrigation canals.At present,several dams are planned across the Blue Nile River in Ethiopia and the Grand Ethiopian Renaissance Dam is currently under construction near the border with Sudan.This will be the largest hydroelectric power plant in Africa.The objective of this paper is to quantify the river flows and sediment loads along the Blue Nile River network.The Soil and Water Assessment Tool was used to estimate the water flows from un-gauged sub-basins.To assess model performance,the estimated sediment loads were compared to the measured ones at selected locations.For the gauged sub-basins,water flows and sediment loads were derived from the available flow and sediment data.To fill in knowledge gaps,this study included a field survey in which new data on suspended solids and flow discharge were collected along the Blue Nile and on a number of tributaries.The comparison between the results of this study and previous estimates of the sediment load of the Blue Nile River at El Deim,near the Ethiopian Sudanese border,show that the sediment budgets have the right order of magnitude,although some uncertainties remain.This gives confidence in the results of this study providing the first sediment balance of the entire Blue Nile catchment at the sub-basin scale. 相似文献
The Three Gorges Reservoir (TGR) is suffering from unexpected fine sediment deposition, to better understand the fine sediment transport processes, field measurements were conducted at the Zhongxian and Fengjie reaches. A method based on the sediment diffusion equation was proposed to measure the settling velocities using the Acoustic Doppler Velocimeter (ADV). The backscatter acoustic intensities (BSI) received from the ADV were calibrated against the sediment concentrations measured via water sampling, suggesting a linear relationship in double logarithmic coordinate system. The instantaneous sediment concentration was calculated using the derived relationship, and then the settling velocity was obtained through the proposed procedure. The settling velocities of the fine particles in the TGR were found to vary with the water depth. Most of the effective settling velocities were within the range of 0.1–10 mm/s, which were larger than those of the primary particles, indicating that the flocculation was likely to occur in the TGR. Additionally, it is suggested that the turbulent motion played an important role in the flocculation in the TGR. 相似文献