Erosional troughs in deep-sea carbonates and their relationship to basement structure


A detailed survey of a small area in the eastern equatorial Pacific with the Marine Physical Laboratory's Deep-Tow instrument package reveals erosionally excavated troughs in an area of relatively rapid accumulation of carbonate. The troughs lie on top of a basement high implying a relationship between the troughs and the basement feature. Differential accumulation and compaction may explain the origin of the troughs. Sediment deposited around the basement high preferentially accumulates on gentle slopes and in troughs. This results in a thick sequence of sediment on the flanks of the basement high and a thin sequence above on top of the hill. Unstable sediment masses and differential compaction generate a tensile-stress field above the peak of the basement high which causes slumping and faulting. The steep slopes generated by faulting and slumping may then serve to intensify tidal currents or act as spillways and locally generate increased turbulence. This increased turbulence results in local erosion by dissolution.

A trough will form above a basement high, however, only when a combination of (1) basement steepness, (2) high sedimentation rate, (3) sediment thickness, and (4) sediment erodibility are present.


Center for Coastal and Ocean Mapping Affiliate

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Marine Geology

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Copyright © 1981 Published by Elsevier B.V.