THE SEISMIC EXPRESSION OF REAL AND APPARENT BURIED TOPOGRAPHY

Subaerial, and in some case submarine, erosional processes sometimes leave a depositional surface which is not plane. During any subsequent transgression and sedimentation, remnant relief on the old surface may be preserved, particularly where depositional rates during the early period of the transgression are high, and the environment energy of deposition is relatively low. As well as in circumstances involving normal clatic sediments, similar situtions can arise in the inundation of a volcanic surface including relief features like vents, fissures and mounds, or of a karstified surface‐carbonate unit. Apparent, or “false” buried topography can be produced by a wide range of geological processes. The difference between such features and those of true buried topography is that at the time of transgression, the latter formed part of the contempory Earth surface, whilst in the case of the false features, the surface at which they were formed was already buried beneath varying depths of sediment. Attention has been directed in recent years to the potential importance of buried topographic features in hydrocarbon exploration. From this viewpoint, the difference between true and false features of this type may be trivial in some cases, but important in others, usually because of the details of the sedimentological processes involved.