The Cambrian Series 2, Stage 4, Emu Bay Shale Konservat-Lagerstäette, Kangaroo Island, South Australia: geology, depositional environment and biota

The lower Cambrian (Cambrian Series 2, Stage 4) Emu Bay Shale Konservat-Lagerstäette from the north coast of Kangaroo Island, South Australia, is by far the best preserved and taxonomically diverse Burgess Shale-type fauna in Australia. It occurs mainly within dark grey to black laminated mudstone in the basal 10 metres of the Emu Bay Shale, the base of which is a sequence boundary. Interbedded structureless fine sandstone horizons up to 20 cm thick are interpreted as mass flow or storm deposits; there is evidence of syndepositional faulting and rapid deposition. The sediments were derived from an uplifted Precambrian land mass a short distance to the northwest. There is no sign of bioturbation thus suggesting anoxic conditions immediately below the sediment-water boundary. The abundance of fossils and trace element geochemical data indicate that the overlying water column was oxic with a sharp redox boundary at the sediment-water interface that was possibly maintained by mat-forming cyanophytes thus suggesting clear, relatively shallow water. There were at least two preservational pathways: pyritization and phosphatization. The trilobites Estaingia bilobata and Redlichia takooensis (up to 25 cm long) dominate the fossil assemblage of over 50 taxa. Other trilobites are rare and represent vagrants. Recent work includes descriptions of the bivalved arthropods Isoxys and Tuzoia, two new nektaspid arthropods (Emucaris, Kangacaris), a new leanchoiliid megacheiran arthropod (Oestokerkus) and a new palaeoscolecid. Other fossils include Myoscolex, demosponges, a vetulicolian, an odontogriphid, hyoliths, brachiopods, numerous problematic taxa, and well preserved eyes of an unknown arthropod plus those of Anomalocaris.