The first record of a Maastrichtian ammonite from the Perth Basin,Western Australia,and its biostratigraphical significance

The first known ammonite from the Maastrichtian of the Perth Basin, a single, incomplete specimen of Grossouvrites gemmatus (Huppé, 1854), is described from core material from the Lancelin No. 1 borehole. Foraminiferal and nannoplankton evidence date the ammonite as middle Maastrichtian; its age is also assessed on the basis of dinoflagellate assemblages from this section, but these give a less precise dating. The position of the ammonite with respect to a mid-Maastrichtian disconformity, which probably extended along much of the Western Australian margin is discussed.