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航磁测量已经证实在利比里亚岸外的陆架上存在几个磁性基底深度超过五公里的盆地。需要对176百万年到192百万年(侏罗纪)侵入到古生代(?)岩层中的磁性辉绿岩和陆上的上复年轻岩层区分“磁性基底”与基底。几条依据测线指出古生代岩层的厚度不到一公里,这意味着辉绿岩的影响并不对基底深度的估算产生巨大误差。根据盆地到大陆斜坡边缘盆地内的年轻沉积岩下面的磁性资料可以判明是岩脉或与其相当的喷出物。磁性资料也圈出了内陆的第二条辉绿岩岩脉带,这条岩脉带平行于海岸,纵贯全国,长达90公里。年轻岩脉的侵入可能和非州与南美开始分裂漂移相一致,与岩脉相伴的磁力异常带平行出现并且延入大西洋的磁力异常带。磁场组构(magnetic fabrit)北东方向的明显错断,在接近西径9°位置和海岸相交。它向东南与Eburnean时代的岩石(约二十亿年)共生,向北西和利比里亚时代(约二十七亿年)的岩石共生。从内陆东北到沿岸区西南的磁场组构方向变化可以圈定陆上利比里亚时代岩石与西径约9°20′西北沿岸区的Pan—African时代(约五亿五千万年)岩层间的界线。一到二公里垂直位移的北—北西和西—北西向的断层组错断了岸上的白垩纪沉积岩,而且可以追踪到近海盆地内。陆架下伏磁性基底的几公里垂直位移显示了整个海岸和大陆架的断块形式。在沿岸区的两个盆地上都有负布格异常;一个负布格异常位于蒙罗维亚(Monrovia)西南的盆地上——好像一条海廊——表明白垩纪或年轻的沉积岩也充填了这些盆地。从塞拉勒窝内到象牙海岸区域有50到60毫伽的正布格异常。这个异常与蒙罗维亚地区的铁镁质变粒岩有关系,异常梯度陡急完全是因为陆缘地壳增厚缘故,也可能和盆地伴生的构造活动有关。在利比里亚整个海岸基底岩石上的多数正异常中,要算利比里亚岸上盆地的花岗片麻岩上的正异常唯有明显错断。三个地震反射剖面证实对近海沉积岩实测剖面的解释。一系列事实表明,构造活动期大概距现今以前约二十七亿年,二十亿年和五亿五千万年;那时,深部地壳岩石的上升和出露;古生代沉积物的沉积;内陆地带辉绿岩岩脉的侵入;176—192百万年的古老岩脉和岩床侵入并伴随发生非州与南、北美的分离;沿海岸和大陆架的断块以及活动的海底扩张发生;白垩纪和第三纪(?)时期的盆地充填;扩张海底上的玄武质喷溢和大陆架与大陆斜坡上的沉积作用。
Aeromagnetic surveys have confirmed the presence of several basins in the continental shelf outside Liberia with depths of more than five kilometers. There is a need to distinguish between “magnetic substrates” and substrates from magnetic diabase that intruded into Paleozoic (176) to 192 million (Jurassic) formations and overlying young overburden formations on land. Several lines indicate that Paleozoic rock formations are less than one kilometer in thickness, which means that the diabase’s effect does not result in a huge error in the estimation of the depth of the basement. According to the magnetic data below the young sedimentary rocks in the basins to the marginal basins of the continental slope, they can be identified as dikes or their equivalent. Magnetic data also enclose an inland second diabase vein, which runs parallel to the coast and runs through the country for 90 kilometers. Intrusive young veins may coincide with the onset of splitting drift in the non-state and South America, with the magnetic anomaly associated with the dikes parallel and extending into the Atlantic magnetic anomaly. Magnetic field (magnetic fabrit) north-east direction of the obvious wrong, close to the 9 o’clock position and the coast of the intersection. It symbioses southeast with rocks of the Eburnean era (about two billion years) and coexists with rocks of the North West and Liberian (about 2.7 billion years). Changes in the magnetic field orientation from the northeast to the southwest of the littoral zone can delineate the boundaries between the Lurian rocks and the Pan-African era (about 550 million years) of the northwestern coast about 9 ° 20’N . The north-northwest and west-northwest faults, one to two kilometers vertically displaced, dislocate Cretaceous sediments on the shore and can be traced into the offshore basin. A few kilometers of vertical displacement of the underlying magnetic substrate show the form of fault blocks along the entire coast and continental shelf. There is a negative Bouguer anomaly on both basins in the littoral zone; a negative Bougainvillea is located in the basin to the southwest of Monrovia - an ocean-like porch - indicating that Cretaceous or young sedimentary rocks were also filled These basins. There are 50 to 60 milliamp positive Bragg anomalies from within the Sierra Leone to the Ivory Coast. This anomaly is related to the granitic magmatic granulites in Monrovia. The abrupt gradient of the anomaly is entirely due to the thickening of continental margins and may also be related to tectonic activities associated with the basin. For most of the positive anomalies on the rocks along the entire coast of Liberia, only the positive anomaly on the granitic gneiss in the littoral basins of Liberia is only clearly faulty. Three seismic reflection profiles confirm the interpretation of the measured profile of offshore sediments. A series of facts show that the period of tectonic activity is about 2.7 billion years ago, two billion years and 550 million years ago. At that time, the rising and exhumation of deep crustal rocks; the deposition of Paleozoic sediments; Intrusion of diabase dykes in the continental belt; invasion of ancient dykes and bedrock from 176-192 million years with accompanying detachment of non-states to South and North America; fault block along the coast and continental shelf and active seabed expansion; Cretaceous And filling of the basin during the Tertiary (?) Period; basaltic spurting on the expanding ocean floor and sedimentation on continental shelf and continental slopes.