S. Jaunich, 1983. "The South-Western African Continental Margin, Velocity Anomalies", Seismic Expression of Structural Styles: A Picture and Work Atlas. Volume 1–The Layered Earth, Volume 2–Tectonics Of Extensional Provinces, & Volume 3–Tectonics Of Compressional Provinces, A. W. Bally
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For a complete discussion of the horizons present in this area of the margin, see the Jaunich paper (Part I) and composite seismic line, two chapters prior to this one.
This velocity anomaly is causing severe disturbances in the shallow horizons. Deeper horizons show a marked pull-up of 200 to 300 msecs (section 8a).
Processing tests were done stacking near, middle, and far traces separately (see sections 8b, 8c, and 8d respectively). The anomaly appears wider and flatter with the latter stack (40 to 60 traces) visible, especially on the lower horizons. This proves that an anomalously high velocity body is situated at shallow levels.
It probably is a shallow-submarine channel with compacted sandstone infill.