The concept from stratigraphy comes from the Latin word stratum, translatable as “bed”. Stratigraphy is called strata analysis, which can be social, archaeological or otherwise.
Stratified sedimentary rocks
The idea of stratum, meanwhile, refers to levels or layers. Usually the term stratigraphy refers to the area of the geology that is oriented to investigation of stratified sedimentary rocks.
This discipline examines the characteristics and arrangement of stratified units that rocks have, generating information about the events that took place in a specific geological period. Stratigraphy also refers to the serial arrangement adopted by sedimentary rocks or strata in an area.
The stratigraphic expert, known as stratigrapher, study the sedimentary processes (that is, those that lead to the development of sedimentary rocks). When the successive sedimentary processes that occurred in a weather geological, you can establish a stratigraphic record.
It should be noted that the stratigraphy is governed by several beginning, detectable in all the geological processes of its concern.
Principles in geology
The principle of uniformity, also called of actualism, affirms that throughout the history of our planet the laws that regulate the processes of geology have always been the same. With respect to principle of the succession of events, postulates that every event that affects a rock (such as a dike or a fault, among others) is inevitably subsequent to it.
According to superposition principle, the lower levels of the strata are older than the upper ones, since the latter are deposited on the former. There is also the principle of original horizontality and lateral continuity, according to which the deposition of the strata always occurs in sense horizontal or subhorizontal, with a limitation given by a pair of planes exhibiting 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 their orientation.
Finally we can talk about principle of faunal succession, which is also called of correlation. He affirms that the fossils of the strata deposited at different times are also fossils, because of the nature of the evolution biological, which is unavoidable. Similar to one of the characteristics of horizontality, the layers that have fossils of the same taxon are the same age.
The notion of stratigraphy is important in the field of archeology, where he mentions the superposition of the strata in a specific region. The stratigraphy indicates that the upper layers are more modern, with which the antiquity increases as it is excavated. This discipline is based on the principles of geological stratigraphy.
In the context of an excavation, the process used to analyze stratigraphies of all kinds that have settled in a certain place, 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 include the place, the orientation and the context, so that it is possible to make a valid study of them. . When this work is finished, a sequence with all the ordered samples is constructed 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. Anyway, already the Scottish geologist James hutton had made a fundamental contribution in 1785 to carry out the dating of certain strata, based on the fact that the fossils of each era served to distinguish them.