However, by the Campanian and the Maastrichtian, the Nkporo Formation records shale, mudstone, limestone and sandstones formed in an offshore environment. In other parts of Nigeria, the Owelli Sandstone, Enugu Shale and Asata Shale formed around the same time in shallow water environments. Other formations of similar age include the ammonite-bearing coals of Mamu Formation and the Nsukka Formation, both from the Maastrichtian.