MAASTRICHTIAN STAGE

also spelled Maestrichtian, uppermost of six main divisions in the Upper Cretaceous Series, representing all those rocks on a global basis deposited during the Maastrichtian Age (74.5 to 66.4 million years ago). The stage's name is derived from the city of Maastricht in the southeastern Netherlands, whose surrounding area serves as the classic type district for rocks of this age. The Maastrichtian Stage is extensively represented by chalk formations in northern Europe and in England, for example, the Trimingham Chalk and part of the Norwich Chalk. No global stratotype section and point (GSSP) for the base of the stage has been approved. However, the first appearance of the fossil ammonite Hoploscaphites constrictus is often taken as the base of this stage. The biozones of the calcareous microfossils Micula mura, Lithraphidites quadratus, and Broinsonia parca and of the planktonic foraminifera Abathomphasus mayaroensis/Racemigulembelina fructicosa are also considered to indicate rocks of the stage. The Maastrichtian Stage overlies the Campanian Stage and is itself overlain by the Danian Stage of the Tertiary System.