Within the Mesozoic era there are 3 periods that separate different events that have marked a beginning and an end both at a geological and biological level. The first period is the Triassic and today we are going to focus on the second period of the Mesozoic. It is about the Jurassic. It is a division of the geological timescale that began approximately 199 million years ago and ended approximately 145 million years ago. As with most geologic eras, both the beginning and the end of the periods are not entirely accurate.
In this article we are going to tell you all the characteristics, geology, climate, flora and fauna of the Jurassic.
Key features
This is a period of time in which several important global events have occurred. It follows the Triassic and precedes the Cretaceous. The name Jurassic comes from the carbonate sedimentary formations that occurred in the European region of Jura, located in the Alps. Hence the name Jurassic. Throughout this period, one of the main characteristics is the dominance of large dinosaurs, which are so well known thanks to various films, being an important part of the Jurassic fauna. During this period, the supercontinent Pangaea also split into the continents of Laurasia and Gondwana. For more information on the dinosaurs of this era, you can consult the . In addition, this period is fundamental for the study of the three geological periods of the Mesozoic.
Jurassic geology
This geological period is divided primarily into Lower, Middle, and Upper. These are the well-known epochs within a period. They have been given the names Lias, Dogger, and Malm. During the Jurassic, sea level underwent various minor changes, but only in the interior. Already in the Late Jurassic, some more rapid fluctuations in time could be observed, leading to a rise in sea level, causing the flooding of large areas in North America and Europe.
During this period, we can identify two biogeographic provinces located in what we now know as Europe. One is known as Tethys in the south, and the other is boreal in the north. All coral reefs had to be restricted, for the most part, to the Tethys province. The transition that existed between the two provinces was located in what is now the Iberian Peninsula. The geological record of the Jurassic period is quite good, especially in Western Europe, where the major climate transitions. In this part of the continent, extensive marine sequences were found, indicating a time when much of the continent was submerged beneath shallow tropical seas. Due to the fame of these submerged areas, the Jurassic Coast and the Holzmaden and Solnhofen Lagerstätten are known as World Heritage Sites. If you'd like to learn more about the characteristics of the Triassic, you can consult the related content.
Jurassic climate
During this period, plants accustomed to a warmer climate spread across almost the entire Earth's surface. These plants were able to extend up to 60 degrees latitude. Both the flora belonging to the southern Gondwana rift and northern Siberia included numerous groups of ferns that were able to withstand fairly severe frosts. Today, modern relatives of these ferns are unable to tolerate frost or low temperatures frequently.
All of this, due to the high temperatures, meant that Jurassic landscapes were richer in vegetation than those of the Triassic. Abundant vegetation was especially present at higher latitudes. Since the climate was quite warm and humid, it allowed the spread of all the jungles, rainforests, and forests that formed many of the typical landscapes in Jurassic films. Thus, forests also began to spread across the Earth's surface, with prominent families such as pine-like conifers and araucaria trees, accompanied by various types of ferns and palm trees.
Flora and fauna
During the Jurassic period, flora was quite important globally, especially at high latitudes. Not only were terrestrial forests filled with conifers and ferns abundant, but ginkgo and horsetail were also present. During this period, plants with inflorescences had not yet appeared. We recall that, until this point, the most widespread plants globally belonged to the group of gymnosperms, that is, those without flowers.
The differential distribution of flora across the entire terrestrial range is a faithful reflection of the separation that existed between the equatorial and northern zones. The development of these distinct types was caused by the existence of numerous marine barriers between the northern and southern parts. These marine barriers were conditioned by a greater temperature gradient that ran from the poles to the equator. These thermal gradients were not as pronounced as they are today, although there is no evidence of polar ice during the Jurassic. This further supports the hypothesis that high temperatures were responsible for the spread of this type of plant.
The flora that was far from the Equator corresponded to the plants of temperate zones, and all these Jurassic landscapes were called Cycadophyta. The forests of ginkgos and conifers gave the whole landscape, where the most dangerous dinosaurs were already present. Despite their modernity, plants with true flowers were still absent. The same was true for hardwood trees. These details are crucial to understanding evolution during the Mesozoic period.
As for fauna, dinosaurs spread globally during this period, being the animals that predominated on the planet for the remainder of the period.
I hope that with this information you can learn more about the Jurassic.