rank: NA

scope: climate

rank: NA

scope: climate

rank: NA

scope: climate

rank: NA

scope: climate

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: If the d18O signal is controlled mainly by E/P, then the variation in d18O during the late Holocene suggests repeated multi-decadal wet/dry cycles that are superimposed upon longer-term, millennial patterns of abundant rainfall and drought.

direction: negative

interpDirection: increase

scope: climate

variable: effectivePrecipitation

variableGroup: E/P

scope: climate

scope: climate

basis: Mean lake water was enriched in 18O by evaporation and was 3.6? greater than mean rainwater.

direction: negative

equilibriumEvidence: Calculated 18O values for aragonite and calcite, precipitated in equilibrium with modern lake water (18Owater = + 2.6‰) at a mean annual temperature of 25 C, yield values of 0.92‰ and 0.78‰, respectively (Craig, 1965; Grossman & Ku, 1981). These theoretical values are close to mean values (0.85‰, 0.47‰, and 0.39‰) for recent samples of Cochliopina sp., Pyrgophorus sp., and C. ilosvayi, respectively. This suggests that all three taxa precipitate carbonate near equilibrium with the water in which they live.

inferredMaterial: lake water

integrationTimeUncertaintyType: Chonology; multiple potential controls on d18O

integrationTimeUnits: years

rank: 1

scope: isotope

variable: effectivePrecipitation

variableGroup: EffectiveMoisture

variableGroupDirection: negative

variableGroupOriginal: P_E

basis: Interpretation of early Holocene (9000 until 7300 14C yrBP) oxygen isotopic results in terms of E/P is at odds with the strong evidence for moist conditions based on the presence of extensive lowland forest. The discrepancy between early Holocene pollen and 18Oresults in the PetenItza core can be reconciled if lakewater 18O is assumed to have been controlled by both regional climate and the changing surface area/volume ratio of the filling lake

equilibriumEvidence: Calculated 18O values for aragonite and calcite, precipitated in equilibrium with modern lake water (18Owater = + 2.6‰) at a mean annual temperature of 25 C, yield values of 0.92‰ and 0.78‰, respectively (Craig, 1965; Grossman & Ku, 1981). These theoretical values are close to mean values (0.85‰, 0.47‰, and 0.39‰) for recent samples of Cochliopina sp., Pyrgophorus sp., and C. ilosvayi, respectively. This suggests that all three taxa precipitate carbonate near equilibrium with the water in which they live.

inferredMaterial: lake water

integrationTimeUncertaintyType: Chonology; multiple potential controls on d18O

integrationTimeUnits: years

rank: 2

scope: isotope

variable: hydrologicBalance

variableGroup: area/volume ratio

equilibriumEvidence: Calculated 18O values for aragonite and calcite, precipitated in equilibrium with modern lake water (18Owater = + 2.6‰) at a mean annual temperature of 25 C, yield values of 0.92‰ and 0.78‰, respectively (Craig, 1965; Grossman & Ku, 1981). These theoretical values are close to mean values (0.85‰, 0.47‰, and 0.39‰) for recent samples of Cochliopina sp., Pyrgophorus sp., and C. ilosvayi, respectively. This suggests that all three taxa precipitate carbonate near equilibrium with the water in which they live.

inferredMaterial: lake water

integrationTimeUncertaintyType: Chonology; multiple potential controls on d18O

integrationTimeUnits: years

rank: 3

scope: isotope

variable: temperature

variableGroup: Temperature

variableGroupDirection: negative

variableGroupOriginal: T

variableOriginal: Temperature