| Popis: |
It is possible to correlate the late Campanian and early Maastrichtian marine strata of Nigeria using the ranges of species of the ammonite genus Libycoceras. The earliest outcropping Campanian strata in southern Nigeria contain Libycoceras afikpoense Reyment which occurs in the Zone of Bostrychoceras polyplocum. L. crossense Zaborski succeeds L. afikpoense, while L. dandense (Howarth) appears to straddle the Campanian-Maastrichtian boundary. In the Iullemmeden Basin, however, L. ismaeli (Zittel), a species closest to L. afikpoense, persists throughout the Maastrichtian. The genus Sphenodiscus is of lesser use in Nigeria, ranging in age from Upper Campanian to Maastrichtian with only limited morphological change. |
