Among the most important thermal parameters of the rocks and their composing minerals is the
Geothermal Gradient. Geothermal gradient plays an important role in expressing the subsurface thermal
conditions in any area. After carrying out the required corrections for the thermal data in hand, it was used
for estimating and illustrating the Geothermal Gradient variations with depth. Using such results, an
attempt was carried out to use such variations to identify the subsurface lithologic compositional
variations in the study area based on the thermal characteristics of the different subsurface lithologies.Four
main subsurface units were identified and mapped within the Nile Delta.