Throughout the era of Mesozoic we find 3 periods: the Triassic, Jurassic and Cretaceous. Today we are going to focus on talking about the Cretaceous period. It is a division of the time scale corresponding to the geological time being the third and last period of the Mesozoic. It began approximately 145 million years ago and ended approximately 65 million years ago. This period is divided into two halves known as the Lower Cretaceous and the Upper Cretaceous. This is one of the longest periods within the Phanerozoic eon.
In this article we are going to tell you everything you need to know about the Cretaceous period.
Key features 
This period has its name coming from the Latin in eta which means chalk. This name is based on the strata located in the Parisian Basin in France. In this period life in the seas and on land appeared as a mixture of whole modern forms and archaic forms. It lasts for about 80 million years approximately, being the longest period of the Phanerozoic eon.
As is the case with most of the geological eras we have studied, the beginning of this period is quite uncertain, with a few million years more or less. All the beginnings and ends of geological periods are determined by some major global event, whether due to changes in climate, flora, fauna, or geology. The dating of the end of this period is relatively precise with respect to the beginning. This is because if it coincides with one of the geological layers that has a strong presence of iridium and that seems to coincide with the fall of a meteorite in what now corresponds to the Yucatan Peninsula and the Gulf of Mexico.
This is the famous meteorite that could end up causing a mass extinction that occurred at the end of this period in which much of all fauna disappeared, including dinosaurs. This is the most important event that declares the end of the Mesozoic era. It is after the Jurassic and before the Paleocene.
Cretaceous geology
In the mid-Cretaceous period, more than half of the world's oil reserves that we have today were formed. Most of the most famous concentrations are located around the Persian Gulf and in the region between the Gulf of Mexico and the coast of Venezuela.
Throughout this period, sea levels were continuously rising due to rising global temperatures. This growth brought sea levels to the highest levels ever recorded in the history of our planet. Many areas that were previously desert became flooded plains. Sea levels reached such a point that only 18% of the earth's surface was above water level. Today we have 29% of the emerged land area.
The supercontinent known as Pangea divided throughout the entire Mesozoic era to give rise to the continents we know today. The positions they held back then were substantially different. At the beginning of the Cretaceous there were already two supercontinents known as Laurasia and Gondwana. These two great land masses were separated by the Sea of Thetis. At the end of this period the continents began to acquire the forms that are most similar to the current ones. The progressive separation of the continents was caused by the action of the continental drift and accompanied by the formation of wide platforms and reefs.
The fault system that existed in the inner Jurassic had separated Europe, Africa, and the North American continent. However, these land masses remained close to each other. India and Madagascar were moving away from the East African coast. One of the most important episodes of massive volcanism occurred between the late Cretaceous and the early Paleocene in India. On the other hand, Antarctica and Australia were still together and they were moving away from South America drifting towards the east.
All these movements created new marine routes such as the primitive North and South Atlantic as well, the Caribbean Sea and the Indian Ocean. While the Atlantic Ocean was expanding, the orogenies that had formed during the Jurassic continued from the North American mountain range while the Nevada orogeny was followed by other orogenies such as the Laramide.
Cretaceous climate
Temperatures during this period rose until they reached their peak approximately 100 million years ago. At that time, there was virtually no ice at the poles. Sediments found from this period show that tropical ocean surface temperatures must have been between 9 and 12 degrees Celsius, warmer than today. Temperatures in the deep ocean must have been even 15 and 20 degrees higher.
The planet should not have been much warmer than during the Triassic or Jurassic, but it is true that the temperature gradient that exists between the poles and the Equator should have been smoother. This smoother temperature gradient caused the planet's air currents to subside and contributed to reducing ocean currents. Therefore, there were many oceans that were more stagnant than they are today.
Once the Cretaceous period ended, average temperatures began to a slow descent that was accelerating progressively and in the last millions of years the annual average decreased from 20 degrees to 10 degrees.
Flora and fauna
The effect that caused the Earth to divide into 12 or more isolated landmasses favored the development of endemic fauna and flora. In these populations, they formed their own isolation on the island continents of the Upper Cretaceous and evolved to generate much of the biodiversity of both terrestrial and marine life that we know today.
Good report but with many writing and writing errors.