Who among us does not know the famous series of blockbusters by Steven Spielberg "Jurassic Park," where one of the main characters is a Tyrannosaurus rex, cloned from a drop of blood of a prehistoric mosquito. However, to be precise, this predator and its similarly sized neighbors existed in the Cretaceous period, which followed directly after the Jurassic. So who lived in the Jurassic period, which lasted from 195 to 135 million years ago?
🔍Geologists divide the Jurassic period into 3 time groups.
The name YURA is the name of a mountain range in Northern Switzerland. The word itself means something like "forest mountains" in Old Swiss. Two hundred years ago, geologists transferred this name to similar layers of Swabian and Franconian Alps in Germany.
More details about the Jurassic periods, their geology, and their use by humans today can be said as follows.
Black Jura or Liassic can reach sediment layers up to 200 meters thick. This layer contains many oil-bearing sands from which gasoline can be produced, but currently, it is not economically viable. Brown Jura or Dogger can also reach sediment thicknesses of up to 200 meters. Its main components are oxides and hydroxides of metals, hence the brown color realized in limestone and sandstone. Until 1950, this material was enriched and iron ore was extracted from it.
White Jura or Malm can reach thicknesses of up to 500 meters, and its components are primarily dolomites and limestones. In the area of the Franconian foothills of the Alps, there used to be a shallow prehistoric sea (lagoon), where a huge number of diverse inhabitants lived, many of which can often be found preserved in stone. These include ammonites, belemnites, various prehistoric sponges, corals, algae, crustaceans, fish, and starfish.
It is precisely this variety of natural patterns from fragments, and if lucky, full-sized remains of ancient world inhabitants that the Jurassic marble is famous for, which is actually Jurassic marbled limestone.
This stone is layered and is mined using an open-pit method, where the top layer of black soil is removed and then the rock is exposed by blasting. After that, using special equipment, blocks of relatively regular shape are cut or hydraulically pressed from the rock at various sites, which are then sent for processing at stone processing enterprises. Typically, this business is conducted by companies that have one or more own quarries, a license for extraction, and their own stone processing facility. This chain allows for the most efficient selection and sorting of stone and its quality processing into a final product. There are companies that have been engaged in this for several decades and know Jurassic limestone through generations of employees. Such knowledge is a guarantee of quality and durability of the stone, as it is impossible to give an absolutely accurate forecast for a material produced by nature through laboratory testing. Statistics accumulated over years, decades, and even centuries provide answers about which stone will be durable on the facade and which carries hidden problems and cannot be used. One simple fact that can be observed after winter is the damage caused by the low frost resistance of some layers of Jurassic stone. Even with the naked eye, it is visible how a particular layer has survived the winter in the quarry.
For the climate of Russia, and primarily its central part, where transitions through "0°C" in late autumn and early spring are registered very frequently almost every year, it should be noted that frost resistance is one of the main factors affecting the durability of a building's facade.