ABSTRACT
BACKGROUND: THE CENOZOIC ERA The end of the Cretaceous Period, which was also the end of the Mesozoic Era, was marked by a massextinction event which saw the end of the dinosaurs and pterosaurs on land, and ammonites and marine reptiles in the sea. In the succeeding Cenozoic Era, which consists of the Palaeogene, Neogene (together these are commonly referred to as the Tertiary) and Quaternary periods, animals and plants assumed a more modern appearance. Mammals and birds replaced dinosaurs and pterosaurs as the dominant vertebrates on land. After the Cretaceous Period, the great many ecological niches left empty by the extinction of the dinosaurs became filled by mammals and birds in an adaptive radiation. By the middle of the Eocene Epoch (the middle epoch of the Palaeogene Period), nearly all of the orders of mammals and major groups of birds had evolved, and there were also present some mammal groups which have since become extinct. At this time, there were no high Alps, nor North Atlantic, and Europe and North America were still connected by land bridges in the vicinity of the Faeroes. There were marine basins in the North Sea, northern France, the Low Countries and Denmark area, and a complex of islands and basins over much of the rest of Europe. Volcanism was common, some associated with the opening of the Atlantic Ocean, and also along old fracture zones such as the Rhine Rift Valley (graben). Grube Messel (which translates to ‘Messel Pit’ – it was an oil shale open pit until its closure and subsequent conservation as a World Heritage Site in 1995) was situated where
the Rhine Graben cut across the Central European Island, and in this down-warping of the Earth’s crust an extensive series of lakes was formed. Grube Messel represents a crater lake within the rift valley.
