Phosphatic nodule beds in Victoria and the late Miocene–Pliocene eustatic event

Abstract

CONTINENTAL evidence of the late Miocene expansion of the Antarctic ice cap and eustatic fall of sea level is still scarce. Here, phosphatic nodule beds in Victoria, Australia and other parts of the world are correlated with these events and with each other. Sedimentological and palaeontological evidence associates the Victorian beds with the late Miocene regressive phase and not with the succeeding early Pliocene phase of deposition. A fauna including whalebone, crabs and the nautiloid Aturia, accompanies the phosphatic nodules. The unusual abundance of phosphatic nodule deposits in the late Miocene is attributed to the contemporaneous evaporation, in the Mediterranean, of phosphate-deficient surface water derived from the North Atlantic, which created an enrichment in phosphate in the world ocean, of which the oversaturation surplus was precipitated. A further association of the phosphatic nodule beds with areas of upwelling is postulated to account for their discontinuous occurrence.