₂₃₈U‐series disequilibrium in the Upper Cretaceous oil shales of Israel as the primary source for the Dead Sea's ₂₂₆Ra anomaly

The Dead Sea contains an anomalously high concentration of soluble radium, which is considerably in excess of its radiogenic parent uranium. Mass balance calculations demonstrated that the radium is brought to the Dead Sea by springs and shallow underground seepages. The primary source from which this radium‐excess is derived has not been identified previously. Using a combination of alpha‐spectrometry, delayed neutron activation (DNA), and gamma‐ray spectrometric analyses, it was found that the extensive oil shales within the Dead Sea watershed exhibit exceptional loss of radium. It is only the coastal hot springs and saline groundwater that have traversed the oil shales that exhibit radium‐excess. Thus, it is demonstrated that a significant portion of the radium‐excess of the Dead Sea brines is derived from the Upper Cretaceous oil shales.