What is Cretaceous ?
Cretaceous is a masculine noun. The term comes from the Latin cretaceus , meaning “relating to chalk or clay”.
The meaning of Cretaceous is a geological period of the Mesozoic Era , between about 145 and 65 million years ago, characterized by the expansion of fauna and flora and the complete domination of dinosaurs on the planet.
In addition to the Cretaceous period, the Mesozoic Era is made up of two other periods: the Triassic and the Jurassic. The Cretaceous, in fact, is considered the end of the Mesozoic Era and the beginning of the Cenozoic Era.
The Cretaceous Period was also marked by intense movements of tectonic plates, due to the separation of the immense continent called Pangea into two megacontinents (two huge blocks of land surface): Gondwana and Laurasia. In this period in question, the intense movement of the plates was especially related to those linked to the fragmentation of Gondwana.
On the continents, this period was dominated by reptiles – several species of dinosaurs –, but the flora began to change, giving rise and rapid flowering of a large number of flowers and fruits (angiosperms).
The average climate of the plant softened during the Cretaceous Period, becoming similar to a tropical temperate climate. In that time, the forests became more intense and constant, giving greater richness in the biodiversity of the flora.
It was at the end of the Cretaceous that a strong biotic crisis took place, with an extinction of several dominant groups during the Mesozoic Era. Groups of microorganisms, invertebrates and vertebrates, especially dinosaurs, were the hardest hit. With these extinctions, many environments remained unoccupied, giving freedom to mammals – who lived in the shadow of dinosaurs – to occupy these environments.
It should be noted that the Cretaceous Period is further divided into two main periods.
The Lower Cretaceous begins the Cretaceous Period (between 145 and 100 million years ago), with particularities.
Features of the Lower Cretaceous
Beginning of the separation of continents, with the formation of Gondwana and Laurasia,
Proliferation of new species of flora and fauna,
Emergence of various species of birds,
Appearance of the first species of placental mammals.
That is, the Lower Cretaceous was marked by geological characteristics and flora.
In Brazil, the Lower Cretaceous Period stands out for the Santana Formation, located in Ceará, where it has numerous fossils of fish and pterosaurs.
The Upper Cretaceou marks the end of the Cretaceous Period and the farewell to the dinosaurs, between 100 and 65 million years ago.
In the Upper Cretaceous, a crisis occurred that caused the extinction of about 50% of the species that lived on the planet at that time. According to scholars, the impact of a large meteor was the cause of this overwhelming destruction and alterations on the planet.
Other theories suggest that the biotic crisis was caused by increased volcanic activity.
Regardless, this was the end of the dinosaurs and the step into the new era, the Cenozoic.
Features of the Upper Cretaceous
Development and diversification of fauna (amphibians, molluscs, insects, etc.), with total dominance of dinosaurs,
Strong geological activity, especially from earthquakes due to collisions of tectonic plates,
Beginning of formation of carbon and oil reserves in sedimentary basins,
Formation of large mountain ranges from the movement and shock between tectonic plates,
Increase in the number of bird and mammal species,
Greater warming of the Earth’s climate – the poles also turned out to be composed of rainforests,
Proliferation of thousands of species of flowering and fruiting plants (angiosperms),
Emergence of several species of fish with greater complexiy, such as, for example, sharks,
Extinction of dinosaurs.
Until today, dinosaurs were the largest animals that ever existed on the face of the Earth and the greatest predators of the Mesozoic Era.