Browsing by Author "Devriendt, D"

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    A 50 ka hydrological record from northern Australia inferred from the chemistry of ostracod valves: implications for the Australian monsoon
    (18th INQUA Congress, 2011-07-21) Devriendt, D; Chivas, AR; Cendón, DI
    Most continuous records of environmental changes on continents over the last glacial cycle derive from the study of lake sediments. Such records are uncommon in Australia since lakes rarely remained permanent features over long periods of time. During most of the last glacial cycle, the largest lake on the Australian continent was located in the centre of the Carpentaria basin, an area covered by the sea today. The well preserved lacustrine sequence underlying the modern marine sediment of the Gulf of Carpentaria has been studied extensively in the past with the main phases of environmental changes with regard to marine versus non-marine conditions being well established. However, palaeoclimatic inferences during the lacustrine phase have remained challenging due to periodic marine influences, strong seasonality and the poor preservation of the lacustrine sequence at sites away from the depocentre of the basin. The elemental (Ca/Na/Mg/Sr/Ba/Mn/Fe/U) and isotopic (δ18O and δ13C) compositions of ostracod valves from the Gulf of Carpentaria lacustrine sequence provide a new palaeohydrological record for northern Australia covering the period 64-14 ka. In particular, inferences on the contributions of potential water sources to the palaeolake and their variations through time are drawn by comparing the ostracod Na/Sr/Ba relative concentrations to the chemical signatures of the rivers draining the modern Carpentaria basin. Wide climatic variations were recorded by the ostracod chemical and isotopic composition and reflect the changing state of the Australian monsoon through time. The monsoon appears weaker/absent during the LGM, although irregular precipitation patterns during this time provoked the oscillations of the palaeolake water-level. Immediately after the LGM, the monsoon progressively developed over northern Australia until 14 ka BP. This causes the rivers from the far south of the basin to reconnect with the palaeolake.