| OCR Text |
Show Boundary of Great Basin Fig. 1. Map of western Great Basin showing location of lake basins discussed in text. Dotted regions indicate extent of Pleistocene- age lakes. a function of the outflow: inf! ow ratio. When the residence time of water in a lake basin approaches zero, the 5180 of the lake approaches the 5180 value of inflow ( caicite precipitated from a 15° C Great Basin lake in which the outflow: inflow ratio approaches unity would have a 5180 value of - 15 % o relative to the standard mean ocean water [ SMOW standard]). Under steady- state conditions, the S180 value of a hydrologically closed Great Basin lake would be highly enriched ( caicite precipitated from a 15° C lake would have an 8180 value of ~ 30 % o). Between 52.5 and 15.5 kyr, 5180 values determined on the total inorganic carbon fraction of Owens Lake sediment ( Fig. 2) are often low (< 22 % o), indicating that Owens Lake overflowed frequently. Isotopic values are very low between 40 and 30 kyr, reflecting a climate that was extremely wet. Before and after this interval, 8180 values often reflect drier climates; for example, between 52.5 and 40 kyr there are several 8180 maxima that denote brief periods of intermittent closure ( C^ Cs). A hiatus in sedimentation between ~ 15.5 and 13.7 kyr marks a time when Owens Lake receded below the core site. An abrupt decrease in S180 at 13.3 kyr culminated in extremely low S180 values at 13.0 kyr, demonstrating a profound abrupt increase in wetness. Magnetic susceptibility ( x) of Owens Lake sediment provides evidence for the timing of glaciation in the Sierra Nevadas that border the Owens Lake basin. For example, values of % are large during the Tioga glaciation ( Fig. 2). The x of Owens Lake sediment derives from the postdepositional alteration of detrital iron- bearing minerals ( e. g., |
