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Water-transfer cylindrical structures in the Late Proterozoic eolian sandstones in the Taoudeni Basin, West Africa

Abstract:

Vertical cylindrical structures have already been described in literature but none in periglacial eolian dune deposits. Two types of vertical cylindrical structures have been observed in the Late Precambrian of western Mali. Type 1 exhibits concentric laminae in subhorizontal transversal section, and a cone-in-cone internal organization. In Type 2, laminations inherited from the parent sediments are partially preserved. The two types are early post-depositional cylindrical features. Both were caused by upward fluid flow responsible for liquefaction-fluidization and entire (Type 1) or partial (Type 2) remobilization of eolian cross-stratification. In a proposed hypothetical reconstruction scheme, a local overpressure caused by an unknown external impulse creates liquefaction cells which evolve either in an upward explosive way (Type 2) or in an upward moving liquefaction front (Type 1). © 1990.