Stratigraphy
ALTERNATIVE NAME/S: Stratigraphy has three related subfields: lithostratigraphy (lithologic stratigraphy), biostratigraphy (biologic stratigraphy), and chronostratigraphy (stratigraphy by age).
DETAILS/DESCRIPTION:
Stratigraphy is a branch of geology concerned with layered, or stratified, rocks. These layers reflect a sequence of events that may include deposition of material, erosion, catastrophic events such as shifting of major blocks of the earth's surface, local disturbances such as mining activities, and so forth.
The object is to achieve an understanding of what happened in a given area over a period of time to create the appearance and structures displayed today. Using basic principles such as the Law of Superposition and the Law of Original Horizontality helps stratigraphers make sense of complex formations.
Modern stratigraphy was founded in the early 1800s. Previous observers noted that many rock formations were arranged in layers, but determining the relationship between layers in different parts of the country or to the proper order of layers in sequences which had been disturbed after they were laid down seemed impossible.
When William Smith* (1769-1839), a geologist and canal-site surveyor, made a systematic study of the geological strata of England, Scotland and Wales, he found that certain fossils occurred only in certain layers. These fossils could be used to provide an estimate of the relative age of different layers and their relationship to each other, even in widely separated locations. In 1814, Smith produced a large, accurate map of geological strata entitled A Delineation of the Strata of England and Wales with Part of Scotland. This map was the first of its kind and has provided a model for subsequent geological maps.
ONELINER: Stratigraphy is the branch of geology concerned with layered, or stratified, rocks.
OTHER CONNECTIONS: None
BIBLIOGRAPHY:
Janes, J. Robert, Geology and the New Global Tectonics, Toronto: Gage, 1980.
"Smith, William." Columbia Encyclopedia, 6th Edition. New York: Columbia University Press, 2002. New York: Bartleby.com, 2002. <http://www.bartleby.com> 30 December 2003.
"Stratigraphy." Columbia Encyclopedia, 6th Edition. New York: Columbia University Press, 2002. New York: Bartleby.com, 2002. <http://www.bartleby.com> 30 December 2003.