1. n. [Geology]

The migration of shoreline into a basin during progradation due to a fall in relative sea level. Deposition during a regression can juxtapose shallow-water sediments atop deep-water sediments.

Antonyms: transgression

See: basin,  condensed section,  eustasy,  progradation,  sequence stratigraphy,  systems tract

2. n. [Reservoir Characterization]

The statistical fitting of trend lines to a dataset. Many regression methods are available, including linear, iterative, multiple and polynomial. If there is a 'good' fit to the data, then the variables are often assumed to be dependent.