Introduction to the Cretaceous System: regional studies

The Cretaceous System was first established by Jean Baptiste Julien d'Omalius d'Halloy based on his geological mapping of France and the adjacent areas of the Low Countries and Northern Italy. His map, which was published in 1822, has a legend with a rock unit identified as ‘Terrain Crétacé’ and that was the birth of the Cretaceous System that we still use today. Unlike many of the other geological systems, there was no definitive publication, only an account about the generation of the map. The Cretaceous, as currently defined, occupies the interval of time from 145 to 66 Ma, making it one of the longest in the Phanerozoic. The Cretaceous includes both icehouse and greenhouse (even hothouse) conditions and much of the time is characterized by exceptionally high sea-levels. These have provided us with widespread deposits of Cretaceous age, from the Arctic to the Antarctic, and all latitudes between. The range of sediments, both marine and terrestrial, is also a backdrop to a range of faunas and floras, some of which are widespread while others are endemic as a result of the Cretaceous dispersion of the continents.