Single-layer burial joints vs single-layer uplift joints in Eocene chalk from the Beer Sheva syncline in Israel

The single-layer (s.l.) joints that occur in the Lower Eocene chalks near Beer Sheva, Israel, developed during the burial history of the rock, whereas the s.l. joints in adjacent Middle Eocene chalks developed during the uplift stage. Characteristically, s.l. burial joints occur in orthogonal cross-fold and strike sets, and as conjugate sets. They precede normal faults and multi-layer joints, and they do not exhibit strike rotation, en échelon segmentation or fracture interaction with each other. These joints are generally closed, and during subsidence older beds fracture first. On the other hand, s.l. uplift joints do not occur in orthogonal or conjugate sets. They are post strike-slip faulting, contemporaneous with multi-layer joints, and exhibit strike rotation, en échelon segmentation and often interact with each other. They are occasionally opened up to several millimetres, and during uplift younger beds fracture first.