Abstract

Incomplete and composite internal moulds, formed by the partial filling of shells by the enclosing sediments at the time of burial, contain a plane, the plane of composition, which shows the horizontal plane at the time the partial filling of the shell hardened. An angular relationship between the common plane parallel to all the planes of composition and the horizontal plane indicates tilting of the formation. Angular relationships between planes of composition indicate a reworking of the sediments. An angular relationship between the common plane and the bedding plane indicates primary structure.

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