A useful way to approach the problem of tectonic activity in an arid region is through study of the history of movement of faults and fractures and of the young alluvial material they displace. Easily datable materials are scarce in these deposits, but carbonates such as caliche, calcrete, travertine, calcite vein, and tufa are common. Several types of these carbonates from the Nevada Test Site area in the southern Great Basin have been collected and dated by the uranium-series method. A variety of geologic settings are represented. The carbonate samples were subjected to a complex treatment process, and the resulting preparations were counted on an alpha spectrometer. Some of the samples from obviously closed systems yielded reasonable ages; others gave only a minimum age for a material or event. Many of the ages obtained agree well with estimates of age determined from dated volcanic units, fault-scarp morphology, and displaced alluvial units. Among the significant ages obtained were three dates of greater than 400,000 years on calcite-filling fractures above and below the water table in an exploratory drill hole for a possible candidate nuclear waste repository site at Yucca Mountain. Another date on calcrete from immediately below the youngest basalt in the region gave an age of 345,000 years, which agrees extremely well with the K-Ar age determined for the basalt of about 300,000 years. Undisturbed travertine that fills faults in several areas gave ages from about 75,000 years to greater than 700,000 years. Soil caliche and calcretes slightly displaced or broken by repeated movement on faults gave minimum ages in the range from more than 5,000 to more than about 25,000 years.

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The radiation chemistry of selected transition metal chelates of glycine and alanine has been investigated in the solid state. Ammonia was released in greatest yield upon dissolution of the cesium-137 r-irradiated samples and COZ was the chief gaseous product measured from the crystalline samples. Reliability of the COZ determinations after dissolution made this product the best basis of comparison between the chelates and their parent amino acid. G(C02) values were: glycine, 1.02; cadmium diglycinate monohydrate, 0.21; zinc diglycinate monohydrate, 0.28; cobalt triglycinate dihydrate, 0.32; nickel diglycinate dihydrate, 0.34; copper diglycinate monohydrate, 0.45; alanine, 0.89; nickel alaninate dihydrate, 0.21 ; zinc alaninate monohydrate, 0.53; and copper alaninate monohydrate, 0.99. G(NH8) values were: glycine, 4.3; alanine, 3.3; copper diglycinate monohydrate, 1 .O; and cadmium diglycinate monohydrate, 0.8. Qualitative and quantitative similarities between the chelates and their parent amino acid indicate similar decomposition mechanisms in agreement with the scheme proposed earlier by Tolbert.

where plans are to construct the storage facility in rock salt beds of the Permian Salado Formation. Detailed surface and subsurface geology at the site and of the surrounding area has been discussed previously Powers and others, 1978).A basic concern for waste repositories in salt beds is their high solu- Rosholt and others (1966) and demonstrated that a process of isotopic evolution of uranium and thorium occurs in most types of sediments, altered volcanic ashes and deeply buried granites provided that some ground water is allowed to migrate through the porous zones of these materials during their geologic history. Often the analyses of the isotopes of the 238 234 230 232 U-U-Th-Th system yield an estimated age for the time of deposition (uranium-trend age estimate) over the range of the method from 2,000 to about 800,000 years ago . Accordingly, it was felt that a preliminary study of salt dissolution residue samples near the WIPP site 1 may yield insight into the dissolution processes and/or it may provide a uranium-trend age estimate for the most recent salt dissolution that produced clay residuum and bands of gypsum. The application of uranium trend dating in the investigation of the age of surficial deposits in the area east of Carlsbad, New Mexico, is included in Part II of this report. All of the dissolution residues (samples A through G, permitted not only quantitative determinations of % recovery but also unambiguous peak energy assignment. Sample solutions were added to a previously prepared and conditioned Dowex 1-X8 ion exchange column in the Cl" form. This solution was evaporated to dryness and the solid dissolved in 6F HC1 solution, after which the treatment was identical to that indicated above.Discs were counted for about 10,000 counts in an Ortec alpha spectrometer. RESULTSResults of the analyses are presented in Table 1 U -U from which the uranium-trend date may be calculated. These 238U uranium-trend plots of the solution residue samples at WIPP-25 are presented in Figure 1. The sample points, except for sample A, yield a linear relation-^ ship on the uranium-trend plots. This linear relationship indicates that the solution residue unit between 179.9 and 183.1 m represents a salt dissolution process for which the calculated uranium-trend date of the residual matter is older than 700,000 years. DISCUSSIONThe results of this study show that the uranium trend dating technique appears to be applicable to date salt dissolution residues. The observed data scatter enable one to obtain a minimum age, in this case, for that section of the core analyzed. No present day dissolution activity is indicated in the interval sampled. Indicated stability for such a long period of time resulting from this study utilizing independent chemical methodology, is in agreement with the work of Bachman, (1974).