The Study Of Structure And Gravitational And Magnetic Fields In Cesar Basin

The Cesar basin is a back-arc foreland basin which located between Santa Marta hill in the northern Colombia and Sierra de Perija mountain. Cesar basin is located between south American plate and the Caribbean plate. The Caribbean plate which is dextral strike-slip subducted the south American plate. The basin has experienced a number of tectonic movement and sedimentary evolution lead to the fault system is more develop and more igneous rocks which control the distribution of oil and gas. There is no uniform understanding fault system and igneous distribution of the Cesar Basin in domestic. To research the fault system, structural feature, development characteristics of igneous rock of this basin, can provide the basic information for the the later stages of the exploration, and have great significance for overseas oil and gas exploration.Comprehensive study of gravity and magnetic data is discussed combined with geological data on the basin. Then deduced the fault structure system and structural feature of the study area. In order to study the magnetic bodies distribution characteristics of the Cesar basin at the low magnetic latitudes. The computing formula of the apparent divergence of the magnetic anomalies is deduced form the principle of the field divergence, combining with the pseudo-gravity anomalies to determine the distribution of the magnetic body in the basin. The main results achieved and conclusions are as follows.1The Bouguer gravity anomaly in basin reflect as uplift in the north-west and depression in north and south. Local gravity and magnetic anomalies reflect distribution of the sedimentary layer and the development of the local geologic body. The center and the eastN the west boundary of local gravity and magnetic anomaly is more developed.2Cesar basin is a complex structure and fracture development which main faults strike is NE(NNE) and NW. The NW-trending faults cut the NE-trending faults, in addition, the NE(NNE)control the boundaries of tectonic unit,and the NW-trending fault size is relatively small.3The theoretical mode has to proved that the plane distribution of the magnetic bodies with the apparent divergence of the magnetic anomalies and two second vertical derivative of the pseudo-gravity anomalies correlation. At the same time proved the effectiveness of this method.4The Cesar basin development magnetic body strike NNE-trending was distributed ineastern boundary、western boundary、tectonic uplift and the area where faults developed. Themagnetic body is not developed in the south of the Karen-bock in the basin.5Cesar basin is divided into four tectonic units, there are northern uplift, northerndepression, central uplift and southern depression. Deposition of the southern depression isthicker than other tectonic units.