Ostracode assemblages in modern African lakes reflect water chemistry variations and so are potentially useful as paleochemical indicators. The water chemistry ranges of 33 modern ostracode taxa have been evaluated for five parameters: total conductivity (K20), Na+, Ca2+, Cl- and alkalinity (CO32- + HCO3-). Strong correlations exist for distribution patterns of ostracodes across all of these parameters except Ca2+. Four, somewhat arbitrary, Ostracode Range Assemblages can be defined, based upon increasing alkalinity and salinity, and named for characteristic taxa. These are: Range I, the Sternocypris assemblage (K20 < 500 μmho) Range II, the Mecynocypria assemblage (K20 = 500-1500 μmho) Range III, the Gomphocythere assemblage (K20 = 1500-4000 μmho) Range IV, the Limnocythere assemblage (K20 > 4000 μmho). An application of the ostracode typology to the fossil record, using a core from Lake Nakuru (Kenya) as an example, suggests a fluctuating alkaline lake prior to about 10,000 yr. B.P., followed by fresh-water conditions until about 8000 yr. B.P. and finally a return to higher alkalinity throughout the remainder of the Holocene. Since the core has also been studied for paleochemical interpretation based upon diatoms, an independent verification of the technique is possible. The two interpretations agree through 80% of the core, suggesting a good reliability for the method.
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Earth-Surface Processes