Late Quaternary palaeohydrological changes in the large playa Lake Frome in central Australia, recorded from the Mg/Ca and Sr/Ca in ostracod valves and biotic remains

Late Quaternary evolution of a playa margin at Lake Frome, South Australia

“…Our sedimentary, microfossil and chronological data indicate two lake events separated by an interval of weathering and subaerial exposure, which is not evident in the beach ridge data Cohen et al, 2011). However, a lacustrine phase followed by significant pedogenesis is also documented in the basal part of sedimentary cores from the centre of Lake Frome (Bowler et al, 1986;De Deckker et al, 2011). By correlation to our Unit 1b, this may suggest MIS5d ages for the basal weathered sediments in these cores followed by an episode of subaerial exposure in MIS5c, but more detailed chronological data are required to confirm this scenario.…”

“…The Lake Frome catchment encompasses an area of around 63,000 km 2 with approximately half of this area corresponding to ephemeral creeks draining the eastern Flinders Ranges to the west of the lake De Deckker et al, 2011). The larger creeks such as Munyallina, Balcanoona and Big John Creeks have headwaters in the Flinders Ranges, where average rainfall is higher (~300 mm/a) than in the surrounding plains (100-300 mm/a).…”

“…1c; (Draper and Jensen, 1976). Even though lakes farther north (Lakes Gregory, Blanche and Callabonna) received water from Strzelecki Creek at that time (De Deckker et al, 2011) which at least partly overtopped the Salt Creek sill (Fig. 1c), water held in Lake Frome in 1974 mostly resulted from a combination of runoff from the Flinders Ranges and groundwater discharge .…”

“…Microfossil content was dominated by Ostracoda (phylum; Arthropoda, sub-phylum; Crustacea) which were found to be present in the sediment. Valves of all genera present were picked and identified following existing studies on macrofossils in South Australian salt lakes (De Deckker, 1983;De Deckker, 1988a;De Deckker, 1988b;De Deckker et al, 2011). The number of valves, life stage details and the state of preservation of the valves were noted.…”

“…Occasional discontinuous beds of sand, granules and pebbles in this unit point to some degree of variations in lake level and/or a source of coarse sediment in relatively close proximity. Microfossils in Unit 1a are only described from one sample -possibly due to the oxidised character of the sediment and poor ostracod preservation -showing dominantly juvenile Diacypris spinosa valves which are commonly found in waters far below 20‰ salinity levels (De Deckker, 1981;De Deckker et al, 2011). In addition, charophyte oogonia are present in Unit 1a (Fig.…”