Magnetic polarity stratigraphy of the Fisherman's Cliff and Bone Gulch vertebrate fossil faunas from the Murray Basin, New South Wales, Australia

The Fisherman's Cliff and Bone Gulch Local Faunas are the second and third oldest mammalian fossil assemblages known in the Murray Basin of southeastern Australia. The determination of well constrained ages for these two faunas has been plagued by a lack of diagnostic microfossils or material suitable for isotopic age determinations. Based on previous paleomagnetic data 1,2] the ages of the Fisherman's Cliff and Bone Gulch local faunas were assigned to the Gauss and lower Matuyama Chrons, respectively. However, these dates were not tested by direct magnetostratigraphic studies at either locality. In order to make direct correlations, 22 paleomagnetic and five paleomagnetic sites, respectively, were collected from Fisherman's Cliff and Bone Gulch. Results indicate that the Fisherman's Cliff Local Fauna occurs within a zone of normal magnetic polarity whilst the Bone Gulch Local Fauna occurs within a zone of reversed polarity. By correlation to the Chowilla section, these zones are interpreted to represent the Gauss and lower Matuyama Chrons and ages of 2.47–2.92 and 1.88–2.47 Myr are indicated for the Fisherman's Cliff and Bone Gulch Local Faunas, respectively.