A preliminary geophysical investigation involving high-resolution shallow seismic reflection was conducted at an abandoned coal mine site located in the outskirt of Johannesburg. The main objective of the study was to compare the vertical resolution of two vertical geophone types, in order to choose the appropriate geophone type that will be suitable for subsurface delineation of dolerite sills that are commonly associated with coal deposits in South Africa. Two vertical geophones with different resonant frequencies of 48 Hz and 100 Hz were compared during the investigation. The acquisition geometry and the data processing sequence were the same for the data acquired with the two geophone types along with a profile where a borehole had confirmed the presence of an intrusive dolerite sill. The results of the investigation show that both geophone types have a similar vertical resolution as they are both able to resolve the intrusive dolerite sill which is about 13 m in thickness.