. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 104 ANNALS OF THE SOUTH AFRICAN MUSEUM salinity, coastal marine environment (FA 4). This passes upward via a high-salinity marine fauna (Cyprideis remanei with allochthonous Paracypris westfordensis, FA 1) into a freshwater assemblage with Sarscypridopsis reni- formis and Heterocypris capensis (FA 5 and FA 2, respectively). Immediately above (in sample 40), the fauna indicates a reversion to more marine conditions with a flood of Cyprideis remanei, rare C. draaihoekensis and abundant, presumed alloch
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 104 ANNALS OF THE SOUTH AFRICAN MUSEUM salinity, coastal marine environment (FA 4). This passes upward via a high-salinity marine fauna (Cyprideis remanei with allochthonous Paracypris westfordensis, FA 1) into a freshwater assemblage with Sarscypridopsis reni- formis and Heterocypris capensis (FA 5 and FA 2, respectively). Immediately above (in sample 40), the fauna indicates a reversion to more marine conditions with a flood of Cyprideis remanei, rare C. draaihoekensis and abundant, presumed allochthonous, Paracypris westfordensis (FA 1). Overlying sediments indicate a second transition to a freshwater environ- ment. Sample 41 has a mixture of high-salinity marine and freshwater faunas (FA 1, 2, 5), suggesting deposition in a vlei subjected to significant marine infil- tration, and this passes upwards into m of clays and sands with freshwater assemblages dominated by FA 2 {Heterocypris capensis and Sarscypridopsis aculeata) throughout, but with FA 5 (S. reniformis) relatively more important in the lower part. The low number of valves (2) in the uppermost sample (sample 48) precludes any confident interpretation of the fauna. The salinity fluctuations are schematically shown on the curve in Figure 17. Ostracod abundances fluctuate considerably throughout these faunal changes (Fig. 18). Generally we found 200 valves/10 g), and in sample 40 with a high-salinity marine fauna (Cyprideis remanei, > 500 valves/10 g), there are sudden increases in the numbers of a particular species. Only in sample 41 (mixed marine and fresh- water) did we recover > 100 valves/10 g, with no domination by one species. OSTRACOD ASSEMBLAGES Freshwater GYPSUM QUARRY DRAAIHOEK. periodic marine flooding, evaporation to dryness and freshwater input ?" Time Fig. 17. Schematic representation of cyclical salinity changes at Draaihoek (solid line) and the Gypsum Quarry (dashed line). Dots in
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