What is Historical Geology?

Also known as "earth history", it is a science that studies the history of the earth, but it is mainly a comprehensive geological discipline that studies the history and laws of crustal development. The study of geohistory is mainly based on the studies of paleontology, stratigraphy, geochronology, and paleogeography; it is also a major branch of geology. The main contents are: study the evolution of paleontology from lower to higher levels to determine the chronological sequence of rock formations (including sedimentary deposits) and their division and contrast; analysis of ancient sedimentary facies and reconstruction of paleogeography, and division of paleogeographic regions Problems; the history of the development of the crust's geological structure, and the history of magmatic activities and metamorphism related to tectonic changes. Comprehensively analyze the interdependent and mutually restrictive relationships of the above aspects, and comprehensively summarize the general laws of crustal evolution. This comprehensive geological discipline provides the theoretical knowledge required for how quickly and efficiently to conduct regional geological surveys, mineral censuses and exploration. In recent years, due to advances in marine geology and geophysics, not only the continental crust but also the occurrence and development of the marine crust has been studied. So the content is richer and more comprehensive. In theory, activity theory (including continental drift, polar shift, ocean floor expansion, plate tectonics, etc.) replaced fixed theory. ^[1]

Historical geology In the middle of the 18th century, JG Lehmann (1756) in Germany and G. Arduino (1759) in Italy divided stratified rocks into primitive, second, and third layers. In 1787, German geological and mineralogist AG Werner summarized the strata into primordial, transitional, overburden, and alluvial layers, which roughly corresponded to the Precambrian, Paleozoic, Mesozoic, and Cenozoic, respectively. From the 1820s to the 1980s, A. Bronnia in France, RI Mocson in the United Kingdom, WD Cornibil, A. Sedgwick, and C. Leyle successively divided the Paleozoic and Mesozoic into periods, The Tertiary is divided into worlds. American JD Danner (1872) and SF Emmons (1887) proposed the Archean and Proterozoic, respectively. Generally formed a more complete geological time representative, similar to modern use (see geochronology).

Historical geology is also an important branch of geology. It mainly studies the development history and regularity of the lithosphere, that is, the crust and part of the upper mantle. Its specific research content includes the history of sedimentary (stratigraphic) development, biological evolution, and tectonic movement. It comes from the rich data accumulated in regional geological surveys, mapping and mineral census exploration practices, and its research results in turn guide these efforts.

Although ancient humans had knowledge about strata and fossils, the formation of the discipline system of geohistory originated mainly in Britain, France, Germany, Italy and other countries in Europe in the 18th and 19th centuries, especially Britain and France.

In the middle of the 18th century, some geologists and biologists in France investigated a large number of fossils and strata in the Paris Basin. They divided the boundaries of the coastal and deep-sea facies that reflect the geographical environment with special sedimentary rocks and biofossils. The stratigraphic sequence of the basin is systematically studied. Later, some scholars systematically studied the strata and fossils of the Villare Mountains, and proposed that there are five sequences from old to new. These have become the basic method of geohistory to restore the past environment by using the properties of fossils and sediments.

The main contents of historical geology research:

The research scope of modern geohistory has been extended to the Ocean and North and South Arctic regions in space; it dates back to the prehistoric period of geology 4 billion years ago; it has penetrated deeper into the upper mantle and the core-mantle relationship. Geohistory has gradually expanded into the discipline of the entire earth history. The research methods and methods of geohistory should involve many branches of geological sciences, as well as relevant disciplines of geophysics. The catastrophic or new catastrophe view of geological evolution in thought, and the concept of stage theory derived from it have been paid more and more attention. Geohistory will develop towards a multi-disciplinary and more comprehensive branch of disciplines.

The first is the dispute between Seismicism and Igneousism, which occurred at the end of the 18th century. The focus of the debate lies in the theory of rock formation. One is represented by the German scientist Abraham G. Werner, who emphasizes the role of water in the formation of rocks; the other is represented by the Scottish scientist James Hutton, who The role of fire. It is known today that rocks are mainly composed of three types. In addition to sedimentary rocks in which water is the main and magmatic rocks in which fire is the main, there is also a type of metamorphic rocks. Both the hydro- and igneous processes play important roles in rock formation.

The second is the dispute between catastrophe theory and gradual change theory (also known as uniform change theory), which occurred in the early 19th century. Scholars who hold the view of catastrophe theory believe that there have been many major disasters in the history of the earth, which caused the extinction of old species and the re-creation of new species. Scholars with a gradualist view believe that the driving force for species evolution comes from the long-term accumulation of weak geological effects in the evolution of the earth, and can occur without relying on large-scale disasters.

The third controversy is the controversy between set theory and activity theory. The doctrine of fixed theory holds that the position of the earth's crust is always invariant, and its movement mode is mainly vertical movement. The traditional theory of floor trough and platform is a kind of fixed theory. The activity theory holds that the crustal movement is mainly horizontal movement. Although vertical movement exists, it is derived from the horizontal movement process (such as the crustal uplift at the horizontal squeeze of two plots). With the development of plate tectonic theory, activity theory is gradually recognized by scholars. ^[3]