Petrographical and geophysical investigations of the sandstones and mudstones in Alice, Eastern Cape Province, South Africa: Implications for groundwater potential

The potentiality for the aquifers' storability in Alice, comprising of rocks of the Beaufort Group, Karoo Supergroup, was examined using a combined method. This investigation is based on SEM+EDX analysis, petrographic study, and porosity and density determination. The SEM+EDX and petrographic studies showed that the rocks are fractured, porous, and contain minerals like quartz, feldspar, lithics, mica, kaolinite, calcite, and illite. The primary diagenetic processes that affect the groundwater storage of the rocks are cementation by authigenic minerals, minerals replacement, dissolution of minerals, and recrystallization. The existence of fractured and dissolution pores improves the groundwater storage capacity. Ten rock samples were selected for density and porosity measurements. The porosity result shows that mudstone has the highest porosity value of 2.56 %, while sandstone has the lowest porosity of 0.85 %. This is due to numerous pore spaces within the mudstone than the sandstone. The density of the mudstone ranges from 2.5763 – 2.6978 g/cm³, while the density of the sandstone ranges from 2.5908 – 2.6820 g/cm³. The secondary porosity is the main porosity for the reservoir rocks. The pores and fractures observed in the rocks act as channels for groundwater, which influence the aquifers' storability in the study area. The techniques used in this research efficiently understand the factors that control the aquifers' storability to assist with groundwater exploration.