Shandong is part of the eastern block of the North China Craton, which means it consists of crystalline and metamorphic rocks. Since the Mesozoic, Shandong has undergone a crustal thinning which is typically a sign for a forming divergent rim. In Africa this caused the Great Rift, a graben system. Here it caused a thinning and resulted in extensive volcanism during the Tertiary. But the province also has some overlying sedimentary rocks which are karstified and/or rich in fossils. The Zhucheng area in southeastern Shandong is famous for many dinosaur fossils including Tyrannosaurus and Ankylosaurus. Shandong has extensive oil fields, especially the Shengli Oil Field (Victory Oilfield) in the Dongying area in the Yellow River delta. As a result it is one of China's richest provinces.