The seismic reflection process expresses the interbedding of sediments as a pattern of seismic cycles which

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parallel time-stratigraphic bedding surfaces. Changes in rock stratigraphy, that is, lithology and facies, are expressed as changes in seismic parameters such as amplitude and interval velocity; these changes may occur within time-stratigraphic units, or may transgress the pattern of time-stratigraphic zones. Seismic stratigraphy is limited by the resolution of the seismic system and is somewhat complicated by the need to exclude unwanted signals, such as coherent noise patterns. Nevertheless, high-resolution seismic sections are the most powerful tool available to modern stratigraphers.

Two studies document the relation of bedding surfaces to seismic reflections. Well log correlations, seismic sections, a seismic model study, and a synthetic seismogram study document time-stratigraphic and rock-stratigraphic relations in Oligocene-Miocene strata in a South American basin. The second study involves a seismic line shot in the western United States across a series of wells spaced about 1 mi apart. Lateral facies changes within interfingering Cretaceous marine and nonmarine sediments demonstrate the continuity of time-stratigraphic surfaces and of reflections across major facies changes.

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