Abstract

Early Proterozoic rocks of widely separated areas contain corrugated, spindle-shaped structures, which formerly were considered to be of organic origin. New evidence indicates that some of these structures have formed by both upward and downward injection of silt into fissures in a muddy sediment. The fissures are interpreted as shrinkage cracks formed beneath the sediment–water interface and may possibly indicate the presence of saline waters.

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