TRENDS OF STRUCTURES IN THE SOKOTO BASIN OF NORTH-WESTERN NIGERIA FROM THE INTERPRETATION OF AEROMAGNETIC ANOMALIES.

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dc.contributor.authorISHAKU, ROGER KENYUY
dc.date.accessioned2017-02-09T08:09:47Z
dc.date.available2017-02-09T08:09:47Z
dc.date.issued2000-03
dc.descriptionA thesis submitted to the Ahmadu Bello University,Zaria , in partial fulfilment of the requirements for the award of the Degree of Master of Science in Applied Geophysics.Department of Physics Faculty of Science Ahmadu Bello University Zaria, Nigeriaen_US
dc.description.abstractThe total magnetic field data for the Sokoto Basin was obtained from aeromagnetic maps each of size 55 km x 55 km within the Basin. A qualitative study of the structural trends in the total field map reveals an alignment of anomalous zones in approximately linear patterns oriented in the N-S, NNE-SSW and NW-SE directions. The residual field map and the regional field were obtained by the method of polynomial fitting using the least square technique. The residual anomalies in the study area change little from the anomalies of the observed total field The residual field was further analyzed by computing the zero contours of the second vertical derivative. These zero contours delineate the magnetic boundaries in the subsurface structures. The elongation of these contours are mostly in the NE-SW and E-W directions, though broken off at shorter distances in some sections. The method of crosscorrelatidn was used to determine the structural trends and alignments for the twenty maps covering the area of study. The main trends for most of the maps are in the ENE-WSW and E-W directions with a moderately high degree of correlation over data values in the northern section of the area as opposed to the southwestern section where a low degree of correlation is common. Spectral analysis of the residual magnetic field over forty eight overlapping blocks of size 55 km x 55 km was carried out. Two prominent magnetic layers were detected. The results reveal that the depths to the first layer vary from V 0 . 9 km to 2 .2 km with an average depth of 1.4 km. The second layer depths vary from 2.2 km to 6.9 km with an average depth of 4.3 km. The third layer magnetic sources are not uniformly distributed. The first magnetic layer is attributed to magnetic rocks intruded on the basement surface. The second magnetic sources are considered to arise from magnetic rocks within the basement which could include fractures and faults. The depths to the basement map show that the magnetic basement beneath the sediments in the basin is generally -V shallow with the highest depth of 2.2 km recorded in the northwest corner of the study area. There are a series of ridges and troughs on the basement surface suggesting that the subsurface rocks must have undergone gentle folding. All the analyses carried out in the study confirm the fact that major structures are oriented in the NE-SW directions. However minor features could be trending in different directions as indicated in a few sections in the crosscorrelat.ion analyses.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/8672
dc.language.isoenen_US
dc.subjectTRENDS,en_US
dc.subjectSTRUCTURES,en_US
dc.subjectSOKOTO BASIN,en_US
dc.subjectNORTH-WESTERN NIGERIA,en_US
dc.subjectINTERPRETATION,en_US
dc.subjectAEROMAGNETIC ANOMALIES,en_US
dc.titleTRENDS OF STRUCTURES IN THE SOKOTO BASIN OF NORTH-WESTERN NIGERIA FROM THE INTERPRETATION OF AEROMAGNETIC ANOMALIES.en_US
dc.typeThesisen_US
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