What is stratigraphic division and correlation? What are the methods of division and comparison, and what are their principles?

Stratigraphic division and correlation are actually two tasks, including stratigraphic division and stratigraphic correlation.

Stratigraphic division: the work of dividing the strata in the stratigraphic section of an area and establishing stratigraphic sequence.

In stratigraphic division, the most important traditional principles are Stena's three laws (overlapping law, primitive horizontal law and primitive lateral continuity law), Walter's phase law and biological sequence law. Firstly, the lithostratigraphic correlation is carried out according to the lithology of different sections that need to be compared, and the stratigraphic framework is established, and then the biota and chronostratigraphic framework are established according to the fossils in the strata. Geochemical methods can determine the age of strata rocks and give more accurate new and old strata and age values. Of course, there are different methods of modern stratigraphy, such as event stratigraphy, magnetic stratigraphy and sequence stratigraphy, and they also have their own principles for stratigraphic division.

Stratigraphic correlation: according to the characteristics of lithology and paleontology fossils, the stratigraphic units in different regions are compared and studied.

The main methods of stratigraphic division and correlation are stratigraphic sequence method, lithostratigraphic method, fossil sequence method, structural method and isotopic geological age method. Biological sequence method is one of the most reliable stratigraphic correlation methods, and the strata containing the same fossils have roughly the same age. Stratigraphic correlation can also be made according to lithology, magnetism and global events in modern stratigraphy, and also according to logging curves in petroleum exploration.