Stratigraphy enables us to understand the details of geography, climate, glaciations, orogeny, epeirogeny, and how the various factors affected the evolution and migration of plants and animals. It is, therefore, an important field in explain various environmental effects and how they shaped our present. Stratigraphy deals with different periods of geological past by revealing their details from the beginning to the present period. This provides a unique challenge to overcome. Radiometric reading will indicate the age of the grain sands as opposed to the unit of sandstone. For example, grains of sand that constitute a sandstone are older than the larger piece of sandstone. A sample taken from the stratum may indicate the age and period of the parent rock instead of the sample itself. The problem arises when attempting to find the absolute age of materials from which the strata are formed. Geologists also face a major pitfall when it comes to establishing the age of the strata using radiometric dating. Additionally, the change in thickness of stratum extends towards the edges where it merges with other deposits. The geologist will find it difficult to establish neat lines that define the stratum. Under such circumstances, part of the earth’s crust may shift over an adjacent section. The stratigraphic record may be difficult to read in the case where an earthquake disturbance has taken place. As such the study may be rendered inaccurate. In a case where erosion has occurred, it may be difficult to come up with an accurate stratigraphic record due to disturbance and unconformity.
It is on the geologist to use accurate judgment to determine whether erosion and other geological forces have affected the stratum. There are many challenges and pitfalls that the geologist can encounter in the study of sedimentary deposits.įirst, layers can be less than an inch deep and some can be many feet deep. There is plenty of room for error when undertaking this kind of study. To accurately study rock layers deposited on the earth, the strata must be undisturbed and unadulterated. This principle establishes that horizontal layers stretch laterally until they thin to a negligible thickness at the edge of their basin of deposition. Oldest layers are found at the bottom and youngest layers at the top in undisturbed strata. The common types of deformation of horizontal layers include folding and faulting. However, external forces may lead to deformation. At the time of deposition, sedimentary layers assume a horizontal inclination. On tilted surfaces, the bed of sediments will tend to take a horizontal position while corresponding to the contours of the basin or depression.
Law of Original Horizontalityĭue to gravitational settling, layers of sediment deposits are arranged in a horizontal manner. Stratigraphic records also preserve major geological events and details pertaining to orogenies (mountain-building), climatic fluctuation, and eustatically-driven sequences.Īs a result, Steno came up with three fundamental principles of stratigraphy, commonly known as Steno’s laws. This, therefore, informs that rock layers indicate a chronological history of the earth and its past life. He concluded that rock layers (strata) are deposited with the upper layers being younger and the lower layers older. Steno established, through observation, that rock layers may not be chaotic as they seem. The laws of stratigraphy were pioneered by Danish geologist, Nicholas Steno, who is also considered the father of stratigraphy. When excavating, techniques used are based on the principles of stratigraphy. Since stratigraphy establishes that sedimentation occurs according to uniform principles, it is easier for archaeologists to draw up conclusions. Stratigraphy is an important field of modern archaeology. Layered rocks may result from successive lava flows or from the formation of extrusive igneous rocks. Stratigraphy is a science that primarily deals with the study of layered sedimentary rocks (called strata) but may also include layered igneous rocks. It is a branch of geology that deals with the correlation, interpretation, and description of stratified sediments and rocks that are found on or below the surface of the earth. The study of stratified rocks is known as stratigraphy. What Is Stratigraphy? Through stratigraphic analyses, scientists and geologists are provided with valuable clues about the age of the earth and its history.
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