Stratifications and reflections

Abstract

The term 'stratification' is used to denote the layered arrangement within sedimentary sequences. According to the International Stratigraphic Guide (Isse 1976), 'a geologic stratum is a layer (a generally tabular body) of rock characterised by certain unifying characters, properties, or attributes that distinguish it from adjacent layers'. From the point of view of reflection seismology, only stratification manifested by changes of acoustic properties is important because only such a stratification may influence the reflection seismic response. Acoustic properties within a layer may be either constant or variabie, the variation being either parallel to stratification, or perpendicular to it. Both types of variation might be present simultaneously resulting in an oblique variation. A boundary between two strata is expressed by more or less abrupt changes of acoustic properties and represents a reflector. The reflection seismic response is influenced by stratification in two ways: by the properties of individual reflectors, and by the properties of stratified systems. This paper's aim is to discuss, from the interpreter's point of view, the influence of both individual reflectors and stratified systems on the reflection seismic response.