J. Kronfeld

Radium contamination in the Nizzana-1 water well, Negev Desert, Israel

In a search for fresh groundwater reserves in the northwestern Negev Desert of Israel, the Nizzana-1 water well drilled into the Judea Group aquifer encountered water that exhibits an anomalously high 226 Ra activity of 2.4 Bq/l, along with 133 Bq/l 222 Rn. The exploited well water is a mixture of the original Judea Group aquifer water and the underlying more saline artesian water of the Kurnub Group (or Nubian Sandstone) aquifer that is currently intruding via faults. Both aquifers elsewhere contain intrinsically low radioactivity. A study of the sedimentary sequence transected by the borehole revealed that much of the bituminous sequence of the Mount Scopus Group of Upper Cretaceous age is substantially depleted in 226 Ra. During its ascent, the Nubian Sandstone water flushes the moderately uranium enriched bituminous sediments, selectively leaching radium and/or receiving alpharecoil additions of radium. These bituminous chalks and marls are regionally widespread. It is thus suggested that radium should be monitored where faulting allows for inter-aquiferial connections across uranium enriched bituminous sections. # 2003 Elsevier Ltd. All rights reserved.

The interaction of two major old water bodies and its implication for the exploitation of groundwater in the multiple aquifer system of the central and northern Negev, Israel

Abstract In the Beer Sheva region of the Negev desert, the only significant fresh groundwater is contained within the Judea Group carbonate aquifer. It is found that this aquifer holds two distinctly different old water bodies. One such groundwater body has evolved in equilibrium with the carbonate aquifer rocks after being recharged during the Holocene in the Hebron Mountains north of the study area. At present, modern recharge, as denoted by the tritium and radiocarbon contents, is very minor. A subtle ‘piston effect’ generated by contemporary replenishment is discussed in representative hydrographs in Beer Sheva wells. Another groundwater body identified in the Judea Group aquifer derives from the underlying Kurnub Group aquifer. The regional artesian Kurnub Group aquifer (Nubian Sandstone) contains an older and brackish groundwater body which has been recharged in Sinai during Pleistocene pluvials. Faulting in the Beer Sheva region facilitated hydrologic contact between the two aquifers. Exploitation of the Judea Group has released confining pressures and resulted in the intrusion of Kurnub Group water into the overlying Judea Group carbonate aquifer. This process is most significant in those wells drilled close to major faults where salinity increases with pumping. The intruding water originating from the Kurnub Group sandstone aquifer has not yet equilibrated chemically with the carbonate host. The low pH and high temperatures that have been encountered indicate continuing and very recent intrusion. In the Beer Sheva area, in the absence of direct significant modern recharge (as determined from tritium and 14 C values), all waters should be considered as paleowaters that are being mined. A complete revision of the hydrologic concept by which the multiple aquifer system can be exploited is required, to take into account the fact that the fresh Judea Group groundwater is actually an old (Holocene) water body intruded by brackish and older (Pleistocene) water along fault zones.

Radium precipitation and extreme 238U-series disequilibrium along the Dead Sea coast, Israel

Abstract Very intense gamma-ray emissions produced by nuclides in the 238 U-decay series were measured in active and relict spring deposits along the Dead Sea coast. Precipitates of Ra near sites of modern springs provide a local source of Rn to coexisting waters. Relict spring deposits, representing prior Dead Sea levels, contain high concentrations of Ra. The Ra in both cases has been derived from the Dead Sea waters (or from the Dead Sea in combination with a Ra component from the primary spring water) and coprecipitated with hydrous oxides of Mn and Fe. The metal oxides precipitated in response to the mixing of the fresher spring waters with the Dead Sea brine.

Epigenetic dolomitization and iron mineralization along faults and their possible relation to the paleohydrology of southern Israel

Abstract Iron mineralization occurs in carbonate rocks of the Cretaceous Judea Group in northern Sinai and the Negev. This mineralization, along with strong enrichment of trace metals, fills fissures and veins. The mineralization is not directly emplaced into the Judea Group limestones but rather within epigenetic dolomites or ankerites which postdate the country rocks. The epigenetic phenomena are narrowly restricted to regional tectonic lineaments. The association of mineralization phenomena with tectonic zones of high permeability suggests that fluid transfer between two distinctly different geochemical environments was the main mineral emplacing agent. Epigenetic dolomitization initially resulted from upflow of old Mg-rich brines along the fault face. During later stages, the residual CaCl 2 brines flowing through the underlying Paleozoic-Mesozoic clastic rocks accumulated Fe and trace metals by leaching of volcanic intrusions. The introduction, via faulting, of these pressurized, acidic, low Eh, metal-bearing brines into the overlying aerated and alkaline carbonate surroundings led to precipitation of Fe which in turn scavenged the trace metals. The Mg-rich brines developed during the Cambrian-Lower Cretaceous mostly continental time-interval. The episodic expulsion of pressurized dolomitizing and metal-bearing brines was related to various stages of tectonic and igneous activity occuring during the Early Miocene-Pleistocene.

Evaluating the rate of migration of an uranium deposition front within the Uitenhage Aquifer

The solubility of uranium in groundwater is very sensitive to changes in redox conditions. Many secondary (sandstonetype) uranium deposits have been formed when soluble U has precipitated after encountering reducing conditions in the subsurface. In the groundwater of the Uitenhage Aquifer (Cape Province, South Africa), 238 U-series isotopes were used to assist in studying the history of the reducing barrier. Uranium isotopes were used to determine the present position of the barrier. Radium and radon were used to evaluate the path of migration that the front of the oxygen depletion zone has taken over the past 10 5 years. During this time the reducing barrier has moved, leaving in its wake a trail of U in various stages of secular equilibrium with its daughter 230 Th. The 226 Ra daughter of 230 Th is not very mobile. Its growth upon the aquifer wall is reflected in the Rn content of the water. This in turn, due to the relatively great age of the water, indicates the extent of the 230 Th ingrowth (from precipitated U) that took place before the barrier migrated.

Comparative isotope study of two short sediment cores from the Dead Sea

Abstract Two short sediment cores from the Dead Sea have been analyzed for the following isotopes: 18O, 13C, 137Cs, 210Pb, U, Th and 40K. In the northerly core, taken from the Jordan River discharge area, the δ13C and δ18O of the carbonates is quite homogeneous and very similar to that found in the suspended material of the inflow. In the southerly core, taken nearshore in the central part of the lake, the stable-isotope composition of the carbonates is depth-variable and generally more enriched in both isotopes. The carbonates of this core are derived from two main sources: allogenic carbonates with an isotopic composition similar to that of the northerly core and endogenic aragonite from the Dead Sea, which is relatively more enriched in both isotopes. 137Cs and 210Pb are used to show that near the Jordan River inflow sedimentation rates are higher by an order of magnitude over the nearshore central region. The first systematic measurements of U and Th in Dead Sea sediments are presented; the values are found to be within the range encountered in sedimentary environments.

Iron-rich veins related to structural lineaments, and the search for base metals in Israel

Abstract Iron-rich veins are associated with tectonic features in Israel and adjacent lands. These iron-bearing veins within otherwise metal-poor sedimentary rocks are commonly accompanied by significant enrichments of other metals such as Mo, Zn, As, V, Ni, Mn, Pb and U. Restriction of these mineralized veins to well delineated tectonic zones suggests the need for re-evaluation of the mineral resource potential of the area. A conceptual geochemical model to guide exploration is provided.

Late Holocene climatic change in the Balkans: Speleothem isotopic data from Serbia

A detailed profile of the stable isotopes of carbon and oxygen was obtained from a speleothem (stalagmite) from the Ceremosjna Cave in eastern Serbia. The stalagmite is a low magnesian calcite that did not show any evidence of diagenetic alteration. It was precipitated under isotopic equilibrium conditions from dripping water. The age and rate of deposition was derived from six internally consistent radiocarbon dates. The initial (super 14) C activity was determined to be approximately 80 pMC. The stalagmite appears to preserve a continuous record of calcite deposition from approximately 2300 BP until the present. Oxygen isotopic data, based upon 100 samples, are used to derive the first paleotemperature record for Serbia. A regression analysis of the all the data indicates that over the period of time that the speleothem was deposited there was a general trend of lowering of the average temperature. Superimposed upon this are significant long-term temperature fluctuations. These can be divided into four broader climatic groupings. Going from the oldest times to the present, there are two warm periods separated by a period when the temperatures fell below the temperature trend line. However, the absolute temperatures were generally above those of the more recent period that is generally characterized by the coolest climatic conditions.

Major Recent tectonic uplift in Iskenderun Bay, Turkey.

Radiocarbon dating was carried out in the sediment profiles of four marine sediment cores taken from Iskenderun Bay, Turkey. The bay is quite shallow in the present day, and a previous tectonic study had considered that the bay floor might have been subsiding. However, this cannot be so, for the (super 14) C ages would thereby lead to the apparent paradox of normal marine sedimentation having taken place during times when glacio-eustatic sea level lowering would have exposed the bay floor. Rather, we conclude that the floor of Iskenderun Bay on the whole has been experiencing rapid uplift since the end of the Last Glacial, due to a combination of tectonic factors linked to the compression between the Anatolian and African plates.

14C and 234u-excess dating of groundwater in the Haifa Bay region, Israel

Radiocarbon activities and uranium isotopic disequilibria were measured in water samples from both the sandy Pleistocene coastal aquifer and within the upper Cretaceous Judea Group carbonate aquifer of northwestern Israel. The samples in both aquifers exhibit a decrease in (super 14) C activity that is concomitant to the growth in (super 234) U-excess. This suggests that under specific conditions, (super 234) U-excess dating of groundwater can be used to corroborate (super 14) C dates, while offering the possibility of extending the range of dating of groundwater beyond that of (super 14) C.