A fundamental thesis of seismic stratigraphy is that seismic reflections follow impedance contrasts that coincide with stratal surfaces, which are surfaces where depositional processes occur at a fixed moment in geologic time. This stratal-surface concept is used herein to image a narrow (width--300 ft), thin, fluvial channel system that is embedded within a seismic reflection peak. The peak reflects from a large (about 2- x 2-mi) area where nonchannel facies dominate its waveshape. The targeted channel facies are confined to an interval that vertically spans less than 30 ft.