Mechanisms of dilatant en échelon crack formation in bedded chalk

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Abstract

This study focuses on various styles of dilatant out-of-plane en échelon cracks, which are associated with bed restricted burial joints, that cut slightly deformed sediments in the Beer Sheva syncline. There is a positive linear fit of en échelon crack length to layer thickness (R2 = 0.928) in fringes which were formed by discontinuous breakdowns in joints. Lithological properties influence the breakdown process. The breakdown of joints into en échelon cracks in chalk beds is influenced by both local conditions and remote stresses. There are two distinct cases of opposite senses of segment rotation in a single fringe: first, in a curved fringe; and, second, in a straight fringe. The former can best be assigned to local deviations of the minimum principal direction from perpendicularity to the parent joint, whereas the latter appears to reflect changes in remote stresses. Two of the three sets of en échelon segmentation which were distinguished in the Beer Sheva syncline are correlated with two distinct tectonic associations. The KIII/KI ratio increases from the layer centre towards the layer boundaries, and this is the driving motivation for both the gradual increase of barb overlap from the centre towards the layer boundaries, and the en échelon segmentation along the layer boundaries.

Original languageEnglish
Pages (from-to)1375-1392
Number of pages18
JournalJournal of Structural Geology
Volume19
Issue number11
DOIs
StatePublished - 1 Jan 1997

ASJC Scopus subject areas

  • Geology

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