EARLY CRETACEOUS VOLCANO-SEDIMENTARY SUCCESSIONS ALONG THE EASTERN AUSTRALIAN CONTINENTAL MARGIN: IMPLICATIONS FOR THE BREAK-UP OF EASTERN GONDWANA

Abstract We report on three large volume Early Cretaceous volcanic and sedimentary provinces: the Whitsunday Volcanic Province and Great Artesian Basin system, both of northeastern Australia, and the Otway/Gippsland basin system along the southeastern margin of Australia. The Whitsunday Volcanic Province is part of a mafic to silicic, high-K calc-alkaline pyroclastic volcanic belt that extends for more than 900 km along the central and southern Queensland coast. Estimated extrusive volumes are >10 5 km 3 . Volcanic and intrusive activity shows a broad range of ages from 132 to 95 Ma, but ages are dominated by an event between ∼120 and 105 Ma. Contemporaneous with volcanism in the Whitsunday Volcanic Province, sedimentary basins in interior and eastern Queensland were receiving large volumes (>10 6 km 3 ) of volcanogenic sediment. The Otway and Gippsland basins 1500 km to the south, were initiated by the break-up of Antarctica and Australia. These basins contain >4×10 5 km 3 of Aptian–Albian extrabasinal volcanogenic sediment supplied from the east. This volcanogenic sedimentation post-dates rift-related volcanism within the basin system. These three provinces are each significant for: (1) the accumulation of large volumes of volcanic and/or coeval volcanic-derived material; (2) the compositional similarity between phenocryst and detrital plagioclase, augite and hornblende; and (3) age data recording a major volcanic episode between 125 and 105 Ma. A causal relationship between volcanism in the Whitsunday Volcanic Province and volcaniclastic sedimentation in the Otway/Gippsland and Great Artesian basin systems is therefore suggested. We propose these provinces record volcanism related to the break-up of eastern continental Gondwana and the formation of the modern eastern Australian passive margin. The scale and volume of volcanic products, coupled temporally with emplacements of oceanic plateaux in the Southwest Pacific, demonstrate that this volcanic event along the present eastern Australian plate margin should be considered as another Early Cretaceous large igneous province.