Stratigraphy is a branch of geology that deals with the study of rock layers, beds , or strata singular: stratum. It is a discipline that correlates rocks and time, helping us understand how, why, and when a certain configuration of strata came to be. In the 17th century, a Catholic priest named Nicolaus Steno formulated the guiding principles of stratigraphy:. In the 19th century, an English geologist named William Smith applied these principles and produced the first geological map of Britain. Since then, he was regarded as the Father of English Geology.
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Geochronology is the science of determining the age of rocks , fossils , and sediments using signatures inherent in the rocks themselves. Absolute geochronology can be accomplished through radioactive isotopes , whereas relative geochronology is provided by tools such as palaeomagnetism and stable isotope ratios. By combining multiple geochronological and biostratigraphic indicators the precision of the recovered age can be improved. Geochronology is different in application from biostratigraphy, which is the science of assigning sedimentary rocks to a known geological period via describing, cataloging and comparing fossil floral and faunal assemblages.
Authors: O'Brien , Michael J. It is difficult for today's students of archaeology to imagine an era when chronometric dating methods were unavailable. However, even a casual perusal of the large body of literature that arose during the first half of the twentieth century reveals a battery of clever methods used to determine the relative ages of archaeological phenomena, often with considerable precision. Stratigraphic excavation is perhaps the best known of the various relative-dating methods used by prehistorians. Although there are several techniques of using artifacts from superposed strata to measure time, these are rarely if ever differentiated.
Stratigraphy is a term used by archaeologists and geoarchaeologists to refer to the natural and cultural soil layers that make up an archaeological deposit. Geologists and archaeologists alike have noted that the earth is made up of layers of rock and soil that were created by natural occurrences—the deaths of animals and climatic events such as floods, glaciers , and volcanic eruptions—and by cultural ones such as midden trash deposits and building events. Archaeologists map the cultural and natural layers that they see in a site to better understand the processes that created the site and the changes that occurred over time. Modern principles of stratigraphic analysis were worked out by several geologists including Georges Cuvier and Lyell in the 18th and 19th centuries.