Sunday, March 29, 2015

Shale Sequences

In basinal clay or shale sequences, deposition is predominantly from suspension load. Conditions of slow but variable, and not necessarily continous, sediment accumulation typify such sequences.

Often deposition of clay-sized grains is interrupted by "rare event" deposits (turbidite flows induced by storms, earthquakes, etc) . Bed thickness in this type of sequence generally ranges from a few millimeters to a few tens of centimeters with the exceptional bed being more than a meter thick.

In view of the thin-bedded nature of this type of sequence, seismic reflections from this depositional setting are almost always an interference response from several acoustic-impedance boundaries. The reflections will follow the attitude of the bedding planes. Since bedding planes in this type of environmental typically parallel time lines, the seismic reflections will not be precise time lines, but will certainly parallel them.

Reference : Practical Seismic Interpretation, Michael E. Badley.

No comments:

Post a Comment