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Details van artikel 2 van 13 gevonden artikelen
| Titel: |
Controls and effects of continental brine formation in a supratidal ephemeral lake in the semi-arid environment of Spencer Gulf, South Australia |
| Auteur: |
Chambers, L. A. Ferguson, J. Burne, R. V. |
| Verschenen in: |
Australian journal of earth sciences |
| Paginering: | Jaargang 37 (1990) nr. 1 pagina's 71-84 |
| Jaar: |
1990-03 |
| Inhoud: |
Ephemeral saline lakes form along the eastern shore of Spencer Gulf where beach ridges isolate areas of the high supratidal zone. The region is semi-arid with rainfall averaging about 320 mm/year and with an evaporation rate of 2000 mm/year. Lacustrine sediments in the lake studied contain abundant discoidal gypsum with a calculated δ34S value of +14.9‰ indicative of precipitation from non-marine, porewater sulphate (δ34S, +13.4‰). Sulphur, deuterium and oxygen isotope distributions and distinctive K/Br and Mg/K ion ratios indicate that groundwaters from landward of and within the lake are non-marine in origin. The marine-terrestrial groundwater interface is mobile; after heavy rains, continental-derived brines flow seaward as far as the high intertidal zone. Within the lake, seasonal changes result in alternate desiccation and flooding by mildly acidic and oxidizing waters. The consequent variability in salinity and redox conditions is inimical to sustained biological activity or sulphide preservation. During dry periods, a halite crust forms on the surface and as anaerobic conditions and bacterial sulphate reduction are established iron sulphides (δ34S, - 18.0 to - 35.3‰) precipitate in the vadose sediments. However when water table levels rise, cyanobacteria colonize wetted surface sediments and the iron sulphides become oxidized. Mobilization of Zn indicates that metals can be transported in the oxidized brines, but such an environment would not favour their preservation as sulphides. The lake is most notable for its gypsum formation and can be differentiated from other well documented sites in that both the water and the sulphate ions have continental signatures despite the proximity to marine-influenced zones. These coastal, gypsiferous, ephemeral lakes are more akin to a continental playa but with some aeolian influences, and thus extend the spectrum of coastal sabkha-like environments, particularly as a consequence of the semi-arid climate. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 2 van 13 gevonden artikelen
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