The Collaborative International Dictionary
Stratigraphy \Stra*tig"ra*phy\, n. [Stratum + -graphy.] That branch of geology which treats of the arrangement and succession of strata.
Douglas Harper's Etymology Dictionary
Wiktionary
n. 1 (context geology English) The study of rock layers and the layering process (stratification). 2 (context archaeology English) the layering of deposits, with newer remains overlaying older ones, forming a chronology of the site.
Wikipedia
Stratigraphy is a branch of geology which studies rock layers ( strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy includes two related subfields: lithologic stratigraphy or lithostratigraphy, and biologic stratigraphy or biostratigraphy.
Stratigraphy is a key concept to modern archaeological theory and practice. Modern excavation techniques are based on stratigraphic principles. The concept derives from the geological use of the idea that sedimentation takes place according to uniform principles. When archaeological finds are below the surface of the ground (as is most commonly the case), the identification of the context of each find is vital in enabling the archaeologist to draw conclusions about the site and about the nature and date of its occupation. It is the archaeologist's role to attempt to discover what contexts exist and how they came to be created. Archaeological stratification or sequence is the dynamic superimposition of single units of stratigraphy, or contexts.
Contexts are single events or actions that leave discrete, detectable traces in the archaeological sequence or stratigraphy. They can be deposits (such as the back-fill of a ditch), structures (such as walls), or "zero thickness surfaciques," better known as " cuts." Cuts represent actions that remove other solid contexts such as fills, deposits, and walls. An example would be a ditch "cut" through earlier deposits. Stratigraphic relationships are the relationships created between contexts in time, representing the chronological order they were created. One example would be a ditch and the back-fill of said ditch. The temporal relationship of "the fill" context to the ditch "cut" context is such that "the fill" occurred later in the sequence; you have to dig a ditch before you can back-fill it. A relationship that is later in the sequence is sometimes referred to as "higher" in the sequence, and a relationship that is earlier, "lower," though this does not refer necessarily to the physical location of the context. It is more useful to think of "higher" as it relates to the context's position in a Harris matrix, a two-dimensional representation of a site's formation in space and time.
Usage examples of "stratigraphy".
And he compared the findings of stratigraphy, palaeontology and physical geography to identify three separate eras with three distinct forms of life.
After we had recorded the excavated half of the bisected posthole in relation to the other stratigraphy, Meg had removed the remaining part of the posthole as well, in the hopes of recovering an artifacta hand-wrought nail perhaps, or even better, a button or piece of pottery that could be more closely datedbut had come up with nothing.