Permian-Triassic Transition • Pangaea, the interior of which was desert. • Low atmospheric oxygen (~12% recovering to ~16%) • No early coal deposits; recovery took ~30 MY • Atmospheric CO2 6X pre-industrial levels • Mean global temperature 3oC higher than today • Lystrosaurus, the most common land vertebrate
The Triassic Period • Named by Friedrich August von Alberti in 1834. The name refers to the 3-parted geological sequence as observed in Germany • 252-201 MYA • Appearance of early crocodilians, pterosaurs, dinosaurs, and mammals. • Modern coral reefs appeared; marine reptiles (Sauropterygia) • Forests recovered by the Middle Triassic (mainly conifers and some seed ferns) • Pangaea began to pull apart
The Jurassic Period • A. Brongniart (1829) named it after the Jura Mountains • 201-145 MYA • Atmospheric oxygen levels rose to an average of 26% • CO2 7X pre-industrial levels • Mean global temperature 3oC higher than today
End Jurassic Extinction event • Minor extinction • Loss of stegosaurids, and largest of the sauropods on land • Marine reptiles, ammonoids, and some bivalves disappeared in the oceans. • No explanation for the extinction.
The Cretaceous Period140 Ma • Jean-Baptiste-Julien Omalius d’Halloy (1822) named for the extensive chalk deposits of western Europe (creta is Latin for chalk) • 145.5-66 MYA • Atmospheric oxygen levels rose to an average of 30% • CO2 6X pre-industrial levels • Mean global temperature 4oC higher than today
Figure 1 from Jan de Boer, Eppinga, Wassen, and Dekker. 2012. A critical transition in leaf evolution facilitated the Cretaceous angiosperm revolution. Nature Communications 3(1221): DOI: 10.1038/ncomms2217
The End Cretaceous Mass Extinction • 75% of plant and animal species became extinct • Uneven in effects: marine plankton, large animals, particularly large tetrapods, filter-feeders, and large marine predators were hit hardest • Loss of forests and immediate decline in photosynthesis caused collapse of ecosystems • Small animals, stream dwellers,and burrowing animals fared better