Authors : Christopher Baiyegunhi, Oswald Gwavava, Kuiwu Liu and Temitope L. Baiyegunhi
Abstract: The South-Eastern Karoo Basin has several dolerite intrusions that possibly introduced heat into the basin and resulted in the large scale conversion of oil to gas. To date, the geometry of these dolerites and variations in electrical resistivity of the purported shale gas hosting Ecca Group is poorly documented despite over 30 years of research in the area. In this study, we investigate the variations in resistivity of the Ecca Group, estimate the average depths to magnetic signatures and produce gravity models that unravel the basin architecture and how dolerite intrusions are interconnected at depth. The magnetic map shows some ring-like or circular structures which coincide with dolerites that were mapped in the field. Depth slicing revealed that the dolerites are pervasive in the study area, extending up to 5400 m. The Bouguer anomaly map shows gravity values increasing from inland to coastal areas. The gravity models revealed that the dolerites form a network of interconnected sills, dykes and inclined sheets at depth. The subsurface apparent resistivity of the Ecca Group varies between 2 Ωm and 557000 Ωm. The pseudosections show that the lower Ecca Group rocks are generally characterised by low resistivity compared to the upper Ecca Group rocks
Christopher Baiyegunhi, Oswald Gwavava, Kuiwu Liu and Temitope L. Baiyegunhi, 2019. An Integrated Geophysical Approach to Mapping and Modelling the Karoo Dolerite Intrusions in the South-Eastern Karoo Basin of South Africa. Journal of Engineering and Applied Sciences, 14: 1885-1911.