Sedimentary Basins in the Western White Nile, Sudan, as Indicated by a Gravity Survey  

作　　者：Mohammed I A Wang Jiaying Liu Tianyou Department of Geophysics, China University of Geosciences, Wuhan 430074 Farwa A G Department of Geology, Faculty of Science, University of Khartoum, Sudan 

出　　处：《Journal of China University of Geosciences》2002年第3期289-296,共8页中国地质大学学报（英文版）

摘　　要：An academic geophysical research as a regional gravity survey was made during1994 in the Western White Nile to infer the shallow crustal structures in the area. The result ofthe survey was compiled as a Bouguer anomaly map with a contour interval of 2 X 10^(-5)m/s^2. It isfound that the negative residual anomalies are related to the Upper Cretaceous sediments (NubianSandstone Formation) filling all depressions in the Basement complex surface while the positiveresidual anomalies are attributed to the relatively shallow or outcropping Basement rocks and thesteep gravity gradients are resulting from the sharp contacts between the sedimentary infill and theBasement rocks. To define the geological structures in the area, 9 profiles were studied. For eachof the profiles, measured and computed Bouguer gravity anomalies, crustal density model, subsurfacegeology evaluation were performed. A G-model computer program was applied in the gravity modeling,which is based on the line-integral method of gravity computation. A geological/structural map wasproposed showing inferred sedimentary basins, faulting troughs and uplifted Basement block andtectonic trends. The basins are believed to be fault-controlled which developed by extensionaltectonics (pull-apart mechanism). As for the mechanism and cause of faulting, the area is consideredas a part of the Central Sudan rift system which had been subjected to several tectonic eventssince Early Cambrian to Tertiary times which resulted in the formation of several fracture systemsassociated with block subsidence, rifting and basin formation.An academic geophysical research as a regional gravity survey was made during1994 in the Western White Nile to infer the shallow crustal structures in the area. The result ofthe survey was compiled as a Bouguer anomaly map with a contour interval of 2 X 10^(-5)m/s^2. It isfound that the negative residual anomalies are related to the Upper Cretaceous sediments (NubianSandstone Formation) filling all depressions in the Basement complex surface while the positiveresidual anomalies are attributed to the relatively shallow or outcropping Basement rocks and thesteep gravity gradients are resulting from the sharp contacts between the sedimentary infill and theBasement rocks. To define the geological structures in the area, 9 profiles were studied. For eachof the profiles, measured and computed Bouguer gravity anomalies, crustal density model, subsurfacegeology evaluation were performed. A G-model computer program was applied in the gravity modeling,which is based on the line-integral method of gravity computation. A geological/structural map wasproposed showing inferred sedimentary basins, faulting troughs and uplifted Basement block andtectonic trends. The basins are believed to be fault-controlled which developed by extensionaltectonics (pull-apart mechanism). As for the mechanism and cause of faulting, the area is consideredas a part of the Central Sudan rift system which had been subjected to several tectonic eventssince Early Cambrian to Tertiary times which resulted in the formation of several fracture systemsassociated with block subsidence, rifting and basin formation.

关 键 词：bouguer anomaly residual anomaly basin fault PULL-APART rift-system 

分 类 号：P223[天文地球—大地测量学与测量工程]