Introducing the Sylvester Graben, a ?Neoproterozoic depocenter on the eastern flank of the Toko Syncline, southern Georgina Basin, Queensland

Abstract

Regional 2D seismic lines acquired in 2013 along the eastern edge of the Toko Syncline in Queensland have imaged a complexly faulted, northwest–southeast trending graben below subcropping Cambrian carbonates. At its deepest, this depocenter contains some 3,500 m of sediments that are inferred to be of Neoproterozoic age, if not older at depth. Surface outcrops of this succession are mapped as the Sylvester Sandstone. Shallow core holes confirm that the uppermost ~1,000 m of sediments are of fluvioglacial, glacio lacustrine and glacial origin, overlain by a thin carbonate of Lower Cambrian age based on the occurrence of archaeocyathids. Unconformably underlying this succession is an internally reflective sedimentary section that is up to 2,500 m which has not been drilled to date. Although the localised development of Neoproterozoic depocenters below Cambrian carbonates in the Toko Syncline has been inferred previously based on vintage seismic and gravity data, such features were not imaged as clearly as on the newly acquired seismic. Inferred sediments in this faulted graben may be correlatives of the Neoproterozoic succession in the Amadeus Basin and could be prospective for hydrocarbons as well as ore deposits.