In this section, you will obtain the complete text of the geology lecture notes of The Principle of Stratigraphy.
In his book entitled "The Principle of Stratigraphy" published in 1913, Amadeus William Grabau defined stratigraphy as "it is the inorganic side of historical geology or the evolution of the earth through successive geological ages in a rocky framework or lithosphere" , Krumbein and Sloss (1951) claimed that stratigraphy can be viewed today as the integrative science that combines data from almost all other branches of earth sciences and results in historical geology. Waller (1960) defines stratigraphy as the branch of geology that dealing with the study of geology - an interpretation of stratified and sedimentary rocks and the identification, description, sequences (both horizontal and vertical), mapping and correlation of stratigraphic rock units. The word "stratified" includes stratified metamorphic rocks e as well as volcanic rocks.
Over the past six decades, a vast amount of data on the geology of the subsurface, primarily from oil, coal exploration and production, oceanographic, and water studies, has contributed significantly to understanding the stratigraphy of many regions of the earth's inland and coastline.
Sedimentary and fossil rocks which contain the fundamental materials for understanding stratigraphic concepts The study of today's sediments, their formation and distribution is essential for understanding the principle of stratigraphy, interpretation ancient sedimentary rocks and establish the stratigraphy of the discs.
Components of Stratigraphy :
The subject of stratigraphy can be divided into two main parts,
Physical stratigraphy and
Biostratigraphy.
Principles :
The Earth's stratigraphic column was built over a few hundred years, mainly from the 18th century onwards and was based on many principles.
1. Earlier catastrophic theories of Earth history
2. The principle of superposition of strata
3. The principle of uniformitarianism
4. Walther’s law concerning sedimentary facies
5. Principle of faunal succession.
1. Earlier catastrophic theories of Earth history :
Within the earlier a part of the nineteenth century, the opinions or the reasons of your time distribution of organisms were greatly influenced by Cuvier, a French vertebrate paleontologist, Associate in Nursingd his followers. per Cuvier, every major amount of time was terminated by a world-wide catastrophe that tired all life. He believed that animals and plants were then reestablished in changed type by an act of Creation at the start of the succeeding period, that inside each period of time, the varied animals and plants were unchanged, that new forms were introduced at wide separate times.
Herodotus, a Greek philosopher, deduced properly within the fourth century B.C. that fossils were remains of ancient ocean creatures which the rocks containing them were shaped below the sea. His concepts became lost for over 2000 years, suppressed by non secular beliefs. As late as in the seventeenth century, some scientists in UK believed that Earth was 6000 years old, that fossils are relics on Noah’s flood or the work of the devil and that geologic history in an exceedingly series of deluges that killed all life, and followed by the special creation of latest fauna.
2. The principle of superposition of strata :
Nicolas Steno (163887) recognized a sequence of lithological events in the mountains of western Italy. He recognized that older rocks were covered with younger rocks, devised stratigraphic laws to explain the organic origin of fossils, and attempted to explain nonconformities, folds, and faults. His principle of layering states that "If one set of rocks is on top of another, the upper series formed after the lower series, unless it can be shown that the beds were due to tectonic action.''
3. The principle of uniformitarianism :
This principle, established by James Hutton (172697), is the fundamental concept of geology. He suggests that the process that is working now has also worked in the past and has produced similar results. More simply, he asserts that "the present is the key to the past", it is not necessary that the different processes have worked at the same pace or with the same intensity. It is possible that a process that worked in the past is not seen today, or that the entire current process has not worked in exactly the same way in the past. Organic materials can be gradually changed in shape and character due to the influence of organic evolution as geological time advances. The degree of correlation between the old process and the current process decreases as the time interval increases.
It is a very close relationship between sedimentation and stratigraphy. The study of recent sediments and their process of formation and distribution makes it possible to establish the principles of interpretations of ancient sedimentary rocks. Stratigraphic documentation is the result of the continuity of sedimentary processes over geological time.
4. Walther's law concerning sedimentary facies :
Johannes Walter (1894) stated that "different deposits of the same facies, area and similitude the sum of rocks of area of different facies formed next to each other in space, but in the crustal profile, we see them on top of each other. It is a basic statement of great importance that only areas of facies and facies can be superimposed, in the first place, which can be observed side by side at the present moment.
Middleton (1973) evoked this concept as follows: “A convenient vertical sequence of facies has been generated from a lateral sequence of environment. This law is one of the basic assumptions of facies analysis and has been demonstrated in many sedimentary environments. which sub-environments sprawl out on top of each other.
5. The principle of faunal succession :
In the last years of the 18th century, William Smith, an English engineer, recognized distinctive traces in rocks such as gypsum and carboniferous strata in very remote areas. He observed that each group contained a particular assemblage of fossils quite distinctive from the top of the upper and lower layers.
Smith was able to apparently correlate similar sedimentary rocks based on the similarity of the fossils. He also noted that there was the same succession of fossil assemblages from the oldest to the youngest strata in all parts of England. He examined that each of the fossil sequences belonged to a specific turn in geological history. That the rocks formed during this period probably contain the same fossils. This is called the principle of faunal succession and has been found to be very useful in correlating rocks that are found in widely separated fossils from they contain.
The above principles combined with the mapping of rocks in the field lead to an understanding of the gradual evolution of the Earth and its history. Attempts to establish the actual geological dates using radioactive isotopes of certain elements led to the calculation of the age of the rocks. These methods are called radiometric dating methods and have been found to be particularly useful in determining the stratigraphic positions of non-fossil-bearing rocks.
Through a detailed study of lithological features, paleontological features (fossil content), order of overlap and structural features of the strata, supported by absolute dating of the rocks, it is possible to establish the local and regional stratigraphy. of a zone and to correlate the stratigraphic sequences even between very distant zones.