rank: NA

scope: climate

rank: NA

scope: climate

rank: NA

scope: climate

rank: NA

scope: climate

rank: NA

scope: climate

rank: NA

scope: climate

basis: The oxygen isotope composition of ostracod carapaces depends primarily on the d18O composition of the water and the tempera- ture at which carbonates precipitate (Craig, 1965; Stuiver, 1970). In tropical, closed-basin lakes within seasonally dry climates, the d18O value of lake water is controlled primarily by the evaporation to precipitation ratio (E/P) of the lake (Fontes and Gonfiantini, 1967; Gasse et al., 1990). During periods of increased (decreased) E/P ratios, the d18O value of lake water will go up (down) as kinetic fractionation processes lead to an increase (decrease) in concen- trations of 18O relative to 16O. Assuming that long-term tempera- ture changes in the tropics are less likely to affect d18O values in the lake than are changes in the E/P ratio (Covich and Stuiver, 1974; Curtis and Hodell, 1993), the d18O value of ostracod carapaces should indicate variations in the E/P ratio of the lake.

direction: negative

interpDirection: increase

scope: climate

variable: effectivePrecipitation

variableDetail: lake water

variableGroup: E/P

scope: climate

scope: climate

basis: The oxygen isotope composition of ostracod carapaces depends primarily on the d18O composition of the water and the tempera- ture at which carbonates precipitate (Craig, 1965; Stuiver, 1970). In tropical, closed-basin lakes within seasonally dry climates, the d18O value of lake water is controlled primarily by the evaporation to precipitation ratio (E/P) of the lake (Fontes and Gonfiantini, 1967; Gasse et al., 1990). During periods of increased (decreased) E/P ratios, the d18O value of lake water will go up (down) as kinetic fractionation processes lead to an increase (decrease) in concen- trations of 18O relative to 16O. Assuming that long-term tempera- ture changes in the tropics are less likely to affect d18O values in the lake than are changes in the E/P ratio (Covich and Stuiver, 1974; Curtis and Hodell, 1993), the d18O value of ostracod carapaces should indicate variations in the E/P ratio of the lake.

direction: negative

inferredMaterial: lake water

integrationTimeUncertaintyType: chronology; hydrology; seasonality; habitat; vital effects

integrationTimeUnits: years

rank: 1

scope: isotope

variable: effectivePrecipitation

variableGroup: EffectiveMoisture

variableGroupDirection: negative

variableGroupOriginal: P_E

scope: isotope

scope: isotope