The origin and occurrence of subaqueous sedimentary cracks

Video of a micro-CT scan through a hand-sample showing molar tooth cracks from the Monteville Formation, South Africa (<i>c</i>. 2.6 Ga). These ptygmatic to linear cracks occur in swarms in finer carbonate-clay beds of the formation and are filled with very finely crystalline calcite spar. The field of view is about 5 cm across.