The taxa of the fossils are used to determine the age of the strata
The concept of stratigraphy comes from the Latin word stratum , translatable as “bed” . The analysis of strata , which can be social, archaeological or of another type, is called stratigraphy.
Stratified sedimentary rocks
The idea of stratum, meanwhile, refers to levels or layers . In general, the term stratigraphy refers to the area of geology that is oriented towards the investigation of stratified sedimentary rocks .
This discipline examines the characteristics and arrangement of stratified units in rocks, generating information about the events that took place in a specific geological period. Stratigraphy also refers to the serial arrangement adopted by the sedimentary rocks or strata of an area.
The expert in stratigraphy, known as a stratigrapher , studies sedimentary processes (that is, those that lead to the development of sedimentary rocks). When the successive sedimentary processes that occurred in geological time are considered, a stratigraphic record can be established.
It should be noted that stratigraphy is governed by several principles , detectable in all the geological processes of its concern.
Principles in geology
The principle of uniformitarianism , also called actualism , states that throughout the history of our planet the laws that regulate the processes of geology have always been the same. Regarding the principle of the succession of events , it postulates that every event that affects a rock (such as a dam or a fault, among others) is inevitably subsequent to it.
According to the principle of superposition , the lower levels of the strata are older than the upper ones, since the latter are deposited on top of the former. There is also the principle of original horizontality and lateral continuity , according to which the deposition of strata always occurs in a horizontal or subhorizontal sense , with a limitation given by a pair of planes that exhibit lateral continuity. He adds that the age of all those that extend horizontally is the same and that only an external force can make them change orientation.
Finally we can talk about the principle of faunal succession , which is also called correlation . He states that fossils from strata deposited at different times are also fossils, due to the nature of biological evolution , which is inevitable. Similar to one of the characteristics of horizontality, layers that have fossils of the same taxon have the same age.
Archaeological stratigraphy
The notion of stratigraphy is important in the field of archaeology , where it refers to the superposition of strata in a specific region. The stratigraphy indicates that the upper layers are more modern, so the age increases as excavation is carried out. This discipline is based on the principles of geological stratigraphy.
Stratification is very useful during an excavation
In the context of an excavation, the process that serves to analyze the stratigraphies of all types that have been sedimented in a given site , it is of great importance to respect an order during the extraction of earth so as not to confuse the data of each layer, which In addition to the time, they include the place, orientation and context, so that it is possible to make a valid study of them. When this work is completed, a sequence is constructed with all the ordered samples, which is known as the relative chronology of the site .
A fundamental work of stratigraphy was Principles of Geology , a book published in 1833 and written by Charles Lyell . In any case, the Scottish geologist James Hutton had already made a fundamental contribution in 1785 to carry out the dating of certain strata, based on the fact that fossils from each era served to distinguish them.