RE:Millions of Elephants died in Kavango over millions of yearsOil and gas comes from algae and zooplankton, processed under heat and pressure; Diagenesis and catagenesis form hydrocarbons. Dead animals only turn into fossils.
Your argument and conclusions aren't accurate, and do not suggest a deposit of commercial hydrocarbons. Although there are hopefully very large deposits of commercial hydrocarbons in the Kavango... only time will tell.