tivity on the carmel faul

terrain (see ch. 1.4- Geological setting of Carmel region), yet no direct evidence of
slope movement in the area of Denya Cave was found to date. Landslides were
documented mostly on the northeastern slopes of the Carmel.
The elimination of these points allows for the working hypothesis that earthquakes
caused the observed damage to speleothems in Denya Cave.
1.3 Dating of Speleothems
In the 238 U radioactive decay-series a state of secular equilibrium between parent and
daughter nuclides is established in any naturally occurring material that has remained
undisturbed for several million years because the half-life of the parent isotope is much greater
than that of the intermediate daughters in the decay chain. The decay-series in secondary
deposits formed from the dissolution and subsequent precipitation of such material, however,
will be in a state of disequilibrium at time of formation, with either an excess or deficiency of
intermediate nuclides because of fractionation processes. The extent to which it has returned to
secular equilibrium in a closed system from an initial state of disequilibrium can be expressed
by a straightforward function of time using the decay constants if the following criteria are
satisfied: (1) intermediate and daughter decay products at time of formation were absent, or if
present, can be corrected for; (2) no gain or loss of the parent nuclide or daughter products
occurred since the time of formation (Richards and Dorale, 2003).
U-series dating of speleothems is based on the extreme fractionation of the parent 238 U
isotope from its long-lived daughter 230 Th in the hydrosphere. The average abundances of U
and Th in the earth’s continental crust are 1.7 and 8.5 µg/g respectively (Wedepohl, 1995).
Their relative abundances in the hydrosphere are different principally because of their differing
solubility in surface and near surface environments (Richards and Dorale, 2003).
U is readily mobilized in the meteoric environment, principally as the highly soluble
Uranyl ion (UO 2+ 2 ). The long-lived daughter product Th exists in a +4 oxidation state and is
readily hydrolyzed and either precipitated or absorbed on detrital particulates. It can therefore
be readily transported with the result that waters feeding secondary calcite deposits will
generally have negligible Th concentrations. In a closed system, the extent to which 230 Th/ 238 U
ac<strong>tivity</strong> (a) ratios have returned to unity is a function of time (t).
Calcite speleothems can be dated accurately by U-series disequilibrium techniques under
specific conditions: (1) when the system remained closed to the addition or removal of U or Th
nuclides to the lattice; (2) when the deposit is younger than ~500,000y; (3) when there is a
sequential stratigraphic layering along the growth axis; (4) when there is no initial Th in the
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