Polygonal fault networks in fine-grained sediments - an alternative to the syneresis mechanism

Polygonal fault networks have previously been identified in fine-grained sediments in several passively subsiding sedimentary basins worldwide. In the absence of tectonic activity, the lack of any preferential strike orientation clearly indicates that the faults developed due to compaction. Since faulting generally does not accompany passive subsidence, it has been proposed that some shrinkage process associated with the colloidal nature of these sediments must have been responsible for horizontal contraction of the bedding. A simpler explanation, consistent with the Mohr-Coulomb theory of shear failure and with laboratory measurements of residual shear strength, is that the coefficient of friction in the fine-grained sediments is exceptionally low.