Stage 1 | Paris - Paris / The warm Eocene, escargot for dinner

Todays stage will bring the peloton over the Champs Élisées, through Paris. In this stage, from the center of the Paris Basin to the edge, we arrive in this stage in the Eocene (56–33.7 million years ago). The Eocene was warm, so warm that the sea level was 60m higher than today. Why? Because it was too hot for polar ice: all the water that is now stored in the polar caps was added to the ocean water in the Eocene. The Paris Basin was therefore a shallow inland sea at that time. A bit like the North Sea, with an opening to the ocean in the northeast. The oldest part of the Eocene is characterized by a climate warming towards a heat record. Peak heat was reached around 50 million years ago. At that time, Antarctica had Palm, Macadamia and Baobabtrees on the coast, hippos walked on the land masses around the North Pole and it was really blistering hot at the equator. In the Paris basin it was also warm, but also wet, it rained heavily, so that thick packages of sediments were dumped into the basin via rivers. As a result, the basin sometimes filled up completely with the sediments supplied by the rivers.

The Eocene geological epoch was first defined in the Paris Basin

The term "Eocene" comes from Greek, and means "Beginning of the New Age." The term was coined in 1833 by geological hero Charles Lyell (1797–1875), who divided the Tertiary (a longer unit of geologic time) into the Eocene, Miocene and Pliocene. He did this on the basis of the degree of similarity of molusc fossils (fossil cochleas) in the rock layers in this Basin, with the modern moluscs. He saw that the older the rock layers, the fewer species that still crawl around today are in those layers. In fact, geologists still use the subdivisions of Lyell as a time indication today.

The Eocene is further subdivided into shorter time periods, each with their own fossils. The part of the Eocene that is exposed within Paris, the white limestones on which the city was built, has been named after Paris: the Lutetian. The ‘snails’ that are found in the Lutetian of Paris can be up to half a meter long! These animals were probably exceptionally slow creatures. The riders today will make for a lot more fireworks than the Lutetian inhabitants of Paris.

I study climate and ocean conditions on and around Antarctica, during the Earths most recent 100 million years. Specifically, I study sediment cores to reconstruct the onset and development of the Antarctic circumpolar current around, and the ice sheet on Antarctica. Check the Geo-TdF-team-2022.

Peter Bijl