MIOCENE CLIMATIC OSCILLATION RECORDED IN THE LAKES ENTRANCE OIL SHAFT, SOUTHERN AUSTRALIA - BENTHIC FORAMINIFERAL RESPONSE ON A MIDLATITUDEMARGIN

The Lakes Entrance oil shaft section in east Gippsland, southeastern A ustralia, spans most of the second-order rise and fall in sea level an d climate known as the Miocene oscillation. For this section, we have established time series of taxic changes and relative abundances of be nthic foraminifera. Metrics reflecting the Miocene oscillation are cha nges in the profiles of inner, middle and outer neritic species, infau na and epifauna, and first and last appearances of species, as well as the numerous intervening comings and goings. A paleodepth curve is de rived from shifts in the dominance of ecological groups. The inferred pattern of transgression/regression shows good agreement with third-or der sequences. The pattern of first and last appearances shows three l evels of particular interest. Two major changes are close by correlati on to second-order sequence boundaries, early in the early Miocene and at the middle/late Miocene boundary respectively. Whereas the plankto nic succession peaks in all measures at the Miocene optimum, the equiv alent but muted benthic peaking leads it by some 2 m.y., peaking at th e beginning of the Monterey carbon excursion. Thus the neritic record is more in tune with the deep-ocean record than with the plankton, and we suggest that fluctuations in nutrient supply had their major impac t on the rising side (early Miocene) of the Miocene oscillation.