Stage 2 | Roskilde - Nyborg / From the age of the dinosaurs to the age of the mammals

The largest part of the more than 12 km thick pile of sedimentary rocks that forms the Danish subsurface can only be reached by deep drillings. But sediments that formed in the last ~100 million years can occasionally also be seen at the Danish surface. The geological map of Denmark (see figure below), on which the ‘young’ sediments and soils of the last 1 million year or so are not shown, reveals that the sedimentary rocks that are close to the surface in Denmark becomes younger from north and east to southwest. On these geological maps is a broad band indicated with a ‘Danian’ age. And the Danian contains a special story.

Early Danian: the extinction of the dinosaurs

The geological timescale is subdivided in intervals based on fossils. Every interval has a combination of fossils that only occurred then, and that allows to date sedimentary rocks. The ‘Danian’ is named after Denmark and is the first time interval of the Cenozoic, which followed directly upon the last interval of the Cretaceous period known as the ‘Maastrichtian’, named after Maastricht in the south of the Netherlands. And the transition from the Maastrichtian to the Danian, 66 million years ago was one of the biggest changes in the history of life: the extinction of the dinosaurs and the impact of the Chicxulub meteorite in the Gulf of Mexico.

During today’s stage, the riders will start in the Cretaceous, in the world of Mosasaurs, T-Rexes, and Triceratopses, but also ammonites. During the day, they will pass catastrophic mass-extinction and enter the barren, almost inhabitable world of the early Danian. After the Chicxulub meteorite impact, an ‘impact winter’ followed, during which the earth was dark and cold, plants had difficulty growing, and 75% of life perished. In the same period, but unrelated to the impact, there were enormous volcanic eruptions that covered 20% of India below a thick pile of lava, which made life even harder. The dinosaurs did not survive this hell, but from their decedents, the birds developed. And mammals saw their opportunity and started to flourish.

The white cliffs of Denmark

This Earth catastrophe is extensively studied in rocks at the Danish coast, not far from the start of today’s stage. The white cliffs of Stevns Klint (see figure) contain the famous transition of limestones that are rich in fossils, through a thin clay layer rich in the metal iridium that is not common on earth but abundant in meteorites and that is recognized across the globa as a trace of the meteorite impact. And what follows are limestones poor in fossils and poor in fossil diversity. These days, the Danian is extensively studied to learn how life recovers from a catastrophe…because humanity’s influence on earth is threatening to cause another one.

I am a geologist and I study plate tectonics and the driving mechanisms in the Earth’s mantle, mountain building processes, and the geography of the geological past. I enjoy geological fieldworks all over the world, and translating the results to science and to a broad public. Read more about Douwe.

Douwe van Hinsbergen