The geology of Tunisia is defined by the tectonics of North Africa, with large highlands like the Atlas Mountains as well as basins such as the Tunisian Trough. Geologists have identified rock units in the country as much as a quarter-billion years old, although most units date to the Mesozoic and Cenozoic, in the past 250 million years. Tunisia has a small but active mining industry and a significant oil and natural gas sector.