Water chemistry of the coastal saline lakes of the Clifton-Preston Lakeland system, south-western Australia, and its influence on stromatolite formation

Abstract

The water chemistry of Lake Clifton, the adjacent lakes and the regional ground water was investigated to aid in the elucidation of the factors responsible for the restriction of living stromatolites to Lake Clifton. The ionic composition of water in the lakes is proportionally similar to sea water, but the ground water is enriched in calcium and bicarbonate and is of lower salinity (1-2 g I^-1). The salinities of the lakes ranged from 7 to 369 g l^-1 during 1984 but, in contrast to the other lakes, Clifton remained less saline than sea water throughout the year. Ground waters from an unconfined aquifer on the eastern shore made a large contribution to the annual lake water budget of Lake Clifton, maintaining lake water salinity at less than 35 g l^-1 and modifying the chemical composition of the sediment-water interface where stromatolites form. Living, lithified stromatolites occur along the eastern shore of Lake Clifton. They are formed by a benthic microbial community rich in Scytonema. The Stromatolites co-exist with an abundant metazoan fauna, but do not appear to be limited by grazing. Clearly defined zones of ground-water intrusion were found along the eastern foreshore and areas of differential ground-water discharge were associated with morphologically distinctive stromatolites. Occurrence of stromatolites and regions of ground-water discharge in Lake Clifton are consistently associated. It is suggested that the intruding ground waters in Lake Clifton provide a chemical environment conducive to the formation of calcified stromatolites.