Holocene Sea Level transgression in carbonate sediments, Torres Strait

Torres Strait, a shallow continental shelf seaway, with a number of reef and island fringed passages, separates Australia from Papua New Guinea. The Strait offers challenging opportunities for geological research into variation in depositional environments, and at the same time, it has been a biogeographical boundary and cultural filter. The collection and analysis of vibrocoring and shallow seismic profiling was undertaken to better understand the Quaternary development of the region. The distinct morphologic features that have been recognised in the shallow seismic sections, provided evidence of repeated history of emergence, subaerial exposure, and fluvial and marine sedimentation. On the basis of grain composition and geomorphic relations, four facies associations are recognisable in the area: (1) Late Pleistocene Terrigenous Clay (A); (2) Transgressive Marine Units (8); (3) Holocene Marine Sediments (C); and (4) Holocene Terrigenous Facies (D). Radiocarbon dates have been derived from Holocene Marine (C) and Transgressive (8) units to obtain a time frame for the late Quaternary geological history. SEM results, pollen analysis and petrographic observations led to several ideas regarding depositional environment, provenance and transport processes. The sedimentary environments within the Torres Strait shelf have been influenced by a number of factors, among which are: subaerial exposure, rapid transgression, climate, prevailing oceanographic factors, shelf bathymetry, carbonate production and the quantity of terrigenous sediment being transported to the shelf. The diversity of sedimentary conditions, together with the extent of inter-reef sediments (Great North East Channel) and estuarine/deltaic deposits (Fly River Delta/Estuary), have caused an evolution of a mixed carbonate siliciclastic shelf system.