On the genesis of discordant dolostone bodies in the northeastern Negev, Israel

Two types of dolostone occurrences are found in the Turonian sequence of the northeastern Negev: layered dolostones which are found interbedded with limestones, and irregular bodies of dolostones of different shapes and sizes. The dolomite formations of these two types are quite different: the bedded one is early diagenetic, whereas the irregular dolostone is clearly late epigenetic in origin. Based on carbon and oxygen-isotopic composition and trace-element content (Sr 2+ and Na +), one may conclude that the irregular dolostones were formed from solution depleted in 18O, Sr 2+ and Na + relative to the solution from which the bedded dolostone was formed. Whereas the bedded dolostones represent a marine (probably slightly evaporated) environment, the irregular dolostone formed either from upward migration of Mg-rich warm formation water or in the interface zone between seawater and fresh water.