Miocene foraminifera from the Finniss Clay and Cadell Marl, western MurrayBasin: taxonomic and taphonomic contrasts and their environmental significance

Sandwiched between Miocene limestones of the Mannum Formation and Morgan Li mestone in the western Murray Basin, the Finniss Clay and Cadell Marl conta in different foraminiferal faunas with varying taphonomic grades. At the Ma nnum Pumping Station section, the Finniss Clay fauna has a low diversity, f requent shallow-water forms, and a poor taphonomic grade. In what was the d eeper part of the basin at Waikerie, a diverse fauna with well-preserved sm all species is recorded in sediments equivalent to the Finniss Clay. In con trast, the Cadell Marl from various localities comprises a well-preserved a nd diverse biofacies with both shallow and deeper water taxa. These contras ts suggest different depositional environments: shallower acid warm during deposition of the Finniss Clay and nutrient-rich, dysaerobic and deeper wat er during deposition of the Cadell Marl. The shallowing event indicated by faunas from the Finniss Clay was due to falling sea level dose to the early /middle Miocene boundary, whereas the Cadell fauna appears to reflect the g lobal carbon buildup at the peak of the Monterey carbon excursion during th e Miocene climatic optimum, about 16 million years ago.