Jointing in chalk: The relation to lithology, bedding thickness, drainage pattern, tectonic stress and cavern openings (Eocene, Bet Guvrin Syncline, Central Israel)

In the area of the Bet Guvrin syncline (central Israel), composed mainly of Eocene chalk, series of joint measurements were conducted, and four, almost consistent, sets of joints were traced. Outcrops of sub-horizontal to horizontal layers are divided into: a lower hard well-bedded unit built of chalk, chalky limestone, silicified beds and concretions of flint, and an upper massive soft unit built of homogeneous chalk, marly in places. The difference in joint density between the lower unit to the upper one is remarkable. The higher the limestone content and the increase in bedding planes, the higher the joint density measured. A good agreement was also found between the joint bearings and the drainage pattern. The study of joint systems, their characteristics and control is of prime importance while planning the use of an underground space.