This research was intended to assess the effectiveness of the surface electrical resistivity and the magnetometer methods in delineating geological fault structures in Guyana. This project was conducted in the Takutu Basin, region #9, Lethem.
A grid of dimension 7km by ~2km was set up at the project area located south-east of Good hope with coordinates, E 222,715.57, N 423,187.77 going in an easterly direction. A total of 14 section lines were conducted within this grid at 500m apart. The total area that was covered during this research is 18.35km2 (4534.37Acres).
The ground magnetics survey proves to be one of the best geophysical methods in identifying the fault bonding the northern side of the Takutu Graben. MapInfo v11.5 and Microsoft Excel were two of the softwares used in processing and representing the magnetic readings during this project.
The resistivity method was not successful as the magnetic method in identifying this fault. This was due to the field constrains encountered during the geophysical survey. The wet ground conditions were the main problem that was encountered during the entire project. Due to the persistent rainfalls during the entire project, the survey method was forced to be changed from constant spread traverse to expanding spread traverse survey.
IPI2win - 1D software of VES profile lines was used for the interpretation of the resistivity data. Two (2) layers were interpreted and an average depth of 25m (82ft) was determined from the resistivity survey. However, it was found too shallow to intercept the different lithologies on either side of the graben i.e. volcanic rocks on the north side and sedimentary rocks on the south side of the fault. As a result no lateral change was observed or estimated in the subsurface geology.
Constant spread traverse technique was the ideal method of observing any lateral changes of the lithologies when passing from volcanic rocks to sedimentary rocks in the graben. Expanding spread traverse is also a useful method of detecting geological structures but it required an idea of the fault location and a wider electrode spacing than was used in the field in order to achieve a deeper penetration into the different lithologies.