stratigraphy

from WordNet (r) 3.0 (2006)

stratigraphy
    n 1: the branch of geology that studies the arrangement and
         succession of strata

from The Collaborative International Dictionary of English v.0.48

Stratigraphy \Stra*tig"ra*phy\, n. [Stratum + -graphy.]
   That branch of geology which treats of the arrangement and
   succession of strata.
   [1913 Webster]