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128 km |
Hills |
Permian period; the last part of the Paleozoic era |
After five days of time-traveling through the Paris Basin, the riders are now sinking into the deeper rock record of the Vosges massif. Today’s ride will bring the peloton through rocks that were deposited in the Permian period, the last part of the Paleozoic era, between 299 and 252 million years ago. And of all the periods that are visited by the Tour de France Femmes, the Permian was probably the least hospitable.
A desert icehouse
Imagine: you’d be riding through the vast interior of the supercontinent Pangea. A Tour de Pangea would bring you from Antarctica to Siberia, and none of it would have been easy cruising. The Permian climate was cold, and dry. A vast icecap covered Antarctica, southern 
Africa, most of South America, and also Siberia. In the equatorial area, where the Vosges were located in the Permian, the interior of Pangea was bone-dry, and you’d find yourself in a colder, but probably still unpleasantly hot Sahara-on-steroids. Almost everywhere in Europe and North America, thick packages of red desert sandstones are found, formed in dunes or sabkhas. But in the Vosges, where we are today, the Permian was rich in explosive volcanism. Dry, dusty, explosive. Terrible conditions for a bike ride.
Permian critters - safe in the desert
Imagine you tried to get in the break-away during this stage, and after your acceleration you find yourself… all alone. Under normal circumstances that would already make for a tough day. But in the Permian, you’d be looking over your shoulder every minute. The lush rainforests of the Carboniferous? Dead and buried. No hope for shelter there, you’d have to wait for tomorrow’s stage. No, the dry Permian lands were occupied by ferns and conifers. Had you escaped in the Carboniferous, land animals were mostly amphibians: they need water to lay their eggs so the desert would have been pretty safe for you. But by Permian times, evolution had figured out a way to reproduce under land conditions: 
amniotes developed. Amniotes, which include you and me, are a clade of organisms that include birds, reptiles, and mammals, who developed a membrane around their eggs that prevent drying-out. So they could invade the dry lands. So you better watch out for Dimetrodon, the top predator, more than five meters long, with an enormous sail on its back and ferocious teeth.
Life in the Permian was good for insects! Following the lush forests of the Carboniferous, oxygen levels were high, and insects could grow BIG. Is that a helicopter you hear above you? Nope. Its Meganisopter, a primitive ancestor of the dragonflies, with a body of 47 cm and a wingspan of 75 cm. If they started bugging you, you’d have little trouble to speed up.
The end of a rough period was even worse
The cold period of the Permian was ended with two global warming spikes. A first one, not too devastating yet, occurred around 260 million years ago, when the Emeishan flood basalts 
erupted in South China. Kilometers-thick piles of basalt lavas poured out over an area of 0.3 million square kilometers. But the Siberian traps, 252 million years ago, were the final nail in the coffin. They covered an area of 7 million square kilometers, caused a doubling of atmospheric CO2 and other greenhouse gasses, causing a global temperature rise of as much as 5°C. And the Siberian lavas rose up through thick layers of rock salt, producing gases that may have destroyed much of the ozone layer. The result? 95% of all marine species went extinct, including the trilobites that had roamed the ocean for nearly 300 million years. 70% of all land life perished. Even many of the insects perished, the only mass extinction of insects that is known so far. It would take life 30 million years to recover. You may want to push your pedals a bit harder to get this stage over and done with!
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 a broad public. Check our complete team.
Douwe van Hinsbergen