Cretaceous
The Cretaceous is a geologic period an seestem that spans 79 million years frae the end o the Jurassic Period 145 million years ago (Mya) tae the beginnin o the Paleogene Period 66 Mya.
| Cretaceous Period 145–66 million years aby | |
| Mean atmospheric O 2 content ower period duration | c. 30 vol % (150 % o modren level) |
| Mean atmospheric CO 2 content ower period duration | c. 1700 ppm (6 times pre-industrial level) |
| Mean surface temperatur ower period duration | c. 18 °C (4 °C abuin modren level) |
Key events in the Cretaceous -140 — – -130 — – -120 — – -110 — – -100 — – -90 — – -80 — – -70 — – An approximate timescale of key Cretaceous events. Axis scale: millions of years ago. | |
It is the last period o the Mesozoic Era, an the langest period o the Phanerozoic Eon. The Cretaceous Period is uisually abbreviatit K, for its German translation Kreide (cauk, creta in Laitin).
The Cretaceous wis a period wi a relatively wairm climate, resultin in heich eustatic sea levels that creatit numerous shallae inland seas. Thir oceans an seas war populatit wi now-extinct marine reptiles, ammonites an rudists, while dinosaurs conteena'd tae dominate on laund. In this time, new groups o mammals an birds, as weel as flouerin plants, appeared.
The Cretaceous (alang wi the Mesozoic) endit wi the Cretaceous–Paleogene extinction event, a muckle mass extinction in that mony groups, includin non-avian dinosaurs, pterosaurs an muckle marine reptiles dee'd oot. The end o the Cretaceous is defined bi the abrupt Cretaceous–Paleogene boondary (K–Pg boondary), a geologic seegnatur associatit wi the mass extinction that lies atween the Mesozoic an Cenozoic eras.
References
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