Can dinotes from the late chalk tell something about the atmosphere more than 66 million years ago? Yes, Writing German paleontologists This week in magazine Pnas: Oxygen isotopes in the tooth enamel can in principle be reconstructed how high the CO2-was concentration.
In the paleo climatology, all kinds of ‘thermometers’ or proxies are used to obtain information about the former climate, from ice cream cores and deep sea ediment to pollen grains and fossil mosquito larvae. For example, scientists hope to find out how hot or cold it was, how much precipitation fell or what the precise composition was of the atmosphere.
In the tooth enamel of vertebrate animals, the oxygenisotope would 17O can play that role, the researchers write in the Pnas-Publicication. When inhalation, the oxygen isotopes end up in the body fluid and eventually end up in the teeth.
What 17O Makes so interesting is that the ratio in relation to other oxygen isotopes is directly linked to CO2-Concentration and the gross primary production (BPP), or the total amount of biomass produced in an ecosystem (mainly through photosynthesis). But the effect of the two is precisely the opposite. The more co2 the atmosphere is all the stronger the so -called isotopenanomaly of 17O, or the different relationship compared to normal. Conversely, that anomaly becomes smaller with increasing BPP (that has, very concisely, to do with the isotope composition of the oxygen that is released during the raised photosynthesis).
Diverse dinos types
The German paleontologists first of all investigated how high the co is based on various fossil dinotes2-Concentration in the late Jura (around 145 million years ago) and the late chalk (around 66 million years ago) was assuming that the gross primary production was the same as that of today. The teeth investigated came from various dinosaur species ranging from the Camarasaurus and the Giraffatitan to the Tyrannosaurus and the Edmontosaurus. This brought the researchers for the late Jura to a concentration that was about four times higher than just before the industrial revolution. For the late chalk it was a 2.5 times higher concentration.
In itself, those values were reasonably similar to the CO2-values obtained thanks to other paleo climatic proxies. But the assumption that the production of organic material at the time was exactly the same size as now is a bit short and so the authors also tried the opposite trick: based on already well -known co2-Data they reconstructed the gross primary production. This brought them to a productivity that was 20 to 120 percent higher than the current BPP.
Changes in the oxygen isotope ratios could therefore not only indicate changing atmospheric concentrations, but also on changing productivity. Bad luck if you only want to know something about co2but interesting for those who want to speculate more targeted about organic production in the distant past.