Palaeogeographical significance of some aspects of Palaeogene and Early Neogene stratigraphy and tectonics of the Timor Sea region
Abstract New evidence from Timor and the Ashmore Reef offshore well suggest that the Palaeogene and Early Neogene geological history of Timor was very different from that of the Sahul Shelf and northern Australia. Recently published correlations between Timor, Ashmore Reef and Australia are disputed and another solution is proposed. Lower Miocene limestones, whose status is critical to the understanding of Timor's Cenozoic tectonic and stratigraphical history, are shown by unambigous field evidence to be autochthonous. This allows a pre-Miocene major orogenic phase in Timor to be confirmed. On the basis of new stratigraphical evidence a mechanism is proposed to explain the development of the Lower Miocene autochthonous “fatus”, which relates their origin partly to lateral facies changes in the Lower Miocene and partly to their subsequent mode of erosion by the emplacement of the Bobonaro olistostrome. New evidence is given in support of an earlier contention, recently challenged by Veevers (1969), that a Timor trough separating the Sahul Shelf from Timor has existed since the Early Eocene. Utilising recent information from a deep offshore well at Ashmore Reef and recently published drift rates for the Indian Ocean-Australian plate and palaeomagnetic laeolatitudes for Australia a series of palaeogeographical maps for the Timor Sea region have been drawn.