The climatic and hydrologic history of southern Nevada during the late Quaternary

Phase II Groundwater Flow Model of Corrective Action Unit 98: Frenchman Flat, Nevada Test Site, Nye County, Nevada, Rev. No.: 0

“…The corrected groundwater ages calculated using the 14 C dilution factors q DIC and q δ13C are listed in Table 8 The apparent absence of significant post-Pleistocene recharge in Frenchman Flat is consistent with paleo-climate interpretations from pack-rat midden data (Forester et al, 1999;Spaulding and Graumlich, 1986) and from regional spring-discharge deposits (Forester et al, 1999;Quade et al, 1995) which indicate that increasing aridity had caused plant communities to change and springs to cease flowing in nearby basins by 9,000 to 10,000 years before present.…”

“…The middens (or nests) are built in layers by successive generations of pack-rats using plant material from nearby areas that is cemented with rat urine that dries and hardens to consolidate the midden. The plant assemblages preserved in the middens have been carbon-dated, and the environmental conditions existing at different times in the southern Great Basin have been estimated based on the precipitation amounts, seasonality, and temperature ranges required by (or tolerated by) their modern plant equivalents (Spaulding, 1985;Forester et al, 1999). In addition to providing an archive of paleoclimatic conditions, pack-rat middens have also been used to estimate the variability in 36 Cl deposition within the Great Basin (Plummer et al, 1997).…”

Future Climate Analysis

“…The chronologies are based on a mass sedimentaccumulation model, calibrated by radiocarbon ages at the top of the core, and the Bishop Ash at the base of the core (see discussions in Forester et al 1999, CRWMS M&O 1998. In this basin, as in most basins, sediment accumulation rates are not expected to be constant over long periods of time, so a chronology derived from an age model should be viewed as an age estimate, at best.…”

“…The Owens Lake chronology shown in Figure 11 is provided here for reference only and is not used in the analysis documented in this AMR. Forester et al (1999) and CRWMS M&O (1998, p. 4.2-18 to 4.2-22) discuss the relation between diatom and ostracode species, Owens paleolake chemistry, and climate. Briefly, during interglacial climates, when, at least on a seasonal basis, Owens River base flow is common, the lake becomes both saline and alkaline, that is, its solute chemistry is characterized by a high alk/calcium ratio.…”

Future Climate Analysis

“…The Owens Lake chronology shown in Figure 11 is provided here for reference only and is not used in the analysis documented in this AMR. Forester et al (1999) and CRWMS M&O (1998, p. 4.2-18 to 4.2-22) discuss the relation between diatom and ostracode species, Owens paleolake chemistry, and climate. Briefly, during interglacial climates, when, at least on a seasonal basis, Owens River base flow is common, the lake becomes both saline and alkaline, that is, its solute chemistry is characterized by a high alkkalcium ratio.…”