Tuesday, March 31, 2015

Clays and Silts in Seismic Reflection

Clays and silts include sediments settled from suspension, whatever the depositional environment. Such sediments tend to be thin bedded and produce closely spaced reflections (relative to other reflection spacings for a particular seismic section).

If the depositional area is extensive, the reflections generally show moderate to good continuity.

Amplitudes tend to be moderate to poor, but is very dependent on bed spacing (interference effects) and lithology. Divergent reflection patterns are diagnostic of fine-grained sediments , as they indicate deposition under conditions where subsidence and sedimentation rates are of similiar magnitude.

Not uncommonly, acoustic impedance contrasts are so low that the interval appears reflection free. Alternatively, destructive interference by beds of a thickness 1/30 wavelenght or less, can also produce reflection free intervals. Chaotic reflection patterns can result from deep-sea current activity or slumping, and from flowage due to loading, elevated pore pressure, or slope instability.


Reference : Practical Seismic Interpretation, Michael E. Badley 

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