I became involved with the introduction of a newly developed Fission Track (FT) method to date thermal and tectonic events. FT is a radiometric dating technique based on analyses of damage tracks produced during the spontaneous decay of 238U in common accessory minerals. Whereas the age of deposition of the parent Ghareb and Taqiya sedimentary rocks of the Mottled Zone (Haturim) complex is fairly well known (75-65 ma), the age of the thermal event that metamorphosed these rocks was unknown at the early 70’s. Apatite was the only uranium –bearing mineral that was both abundant and large enough to date with FI. We dated the Mottled Zone to the late Miocene, 13.6+- 2.0 Ma, but Yeshu raised the question if this age determined at one quarry out of five separate basins was synchronous all over the area, or represented one area only. Later Ar/Ar dating revealed the latter proposal to be correct with older ages of 16 Ma and younger ages of 2.3-4 Ma.
Yeshu was also a pioneer in seeing the advantages of using the ion microprobe in oxygen isotopic studies of speleothems. Working at UCLA where techniques of measuring δ18O of carbonates had been developed, he was able to determine a temporal resolution ranging from ∼1 to 25 years on samples from the Soreq Cave. Later, working on the ion probe at UW Madison we found it necessary to obtain high-resolution images of the speleothems laminae using confocal microscopy. This work revealed that the seasonal patterns existing today were established about 6000 years ago and are different from those in glacial samples. This type of research is now expanding looking into larger questions i.e., hydrological conditions, the impact of freshwater input into the Mediterranean and the extent of summer monsoon rainfall during the last interglacial.