Late Pleistocene history of turbidite sedimentation in a submarine canyon off the northern Great Barrier Reef, Australia

Cores from slopes east of the Great Barrier Reef (GBR) challenge traditional models for sedimentation on tropical mixed siliciclastic-carbonate margins. However, satisfactory explanations of sediment accumulation on this archetypal margin that include both hemipelagic and turbidite sedimentation remain elusive, as submarine canyons and their role in delivering coarse-grained turbidite deposits, are poorly understood. Towards addressing this problem we investigated the shelf and canyon system bordering the northern Ribbon Reefs and reconstructed the history of turbidite deposition since the Late Pleistocene. High-resolution bathymetric and seismic data show a large paleo-channel system that crosses the shelf before connecting with the canyons via the inter-reef passages between the Ribbon Reefs. High-resolution bathymetry of the canyon axis reveals a complex and active system of channels, sand waves, and local submarine landslides. Multi-proxy examination of three cores from down the axis of the canyon system reveals 18 turbidites and debrites, interlayered with hemipelagic muds, that are derived from a mix of shallow and deep sources. Twenty radiocarbon ages indicate that siliciclastic-dominated and mixed turbidites only occur prior to 31 ka during Marine Isotope Stage (MIS) 3, while carbonate-dominated turbidites are well established by 11 ka in MIS1 until as recently as 1.2 ka. The apparent lack of siliciclastic-dominated turbidites and presence of only a few carbonate-dominated turbidites during the MIS2 lowstand are not consistent with generic models of margin sedimentation but might also reflect a gap in the turbidite record. These data suggest that turbidite sedimentation in the Ribbon Reef canyons, probably reflects the complex relationship between the prolonged period (> 25 ka) of MIS3 millennial sea level changes and local factors such as the shelf, inter-reef passage depth, canyon morphology and different sediment sources. On this basis we predict that the spatial and temporal patterns of turbidite sedimentation could vary considerably along the length of the GBR margin.

Pay roll voucher #13 from the Engineer Department of Port Dalhousie and Thorold Railway Extension for the Northern Division for the month of April, 1857 approved by F. Shanly, chief engineer and W.G. Thompson, assistant engineer, April 27, 1857

Pay roll voucher #13 from the Engineer Department of Port Dalhousie and Thorold Railway Extension for the Northern Division for the month of April, 1857 approved by F. Shanly, chief engineer and W.G. Thompson, assistant engineer, April 27, 1857.

Pay roll voucher # 17 from the Engineer Department of Port Dalhousie and Thorold Railway Extension, for the Northern Division for the month of May, 1857, approved by F. Shanly, chief engineer and W.G. Thompson, assistant engineer, May 27, 1857

Pay roll voucher # 17 from the Engineer Department of Port Dalhousie and Thorold Railway Extension, for the Northern Division for the month of May, 1857, approved by F. Shanly, chief engineer and W.G. Thompson, assistant engineer, May 27, 1857.

Voucher from the Engineer Department of Port Dalhousie and Thorold Railway Extension for W.G. Thompson for the Northern Division. There are attached notes from the Welland Railway Company to John Mitchell for putting up shelves; to William Waud, staff; and to William Martin to repair the office (copy), June 10, 1857

Voucher from the Engineer Department of Port Dalhousie and Thorold Railway Extension for W.G. Thompson for the Northern Division. There are attached notes from the Welland Railway Company to John Mitchell for putting up shelves; to William Waud, staff; and to William Martin to repair the office (copy), June 10, 1857.

Pay roll voucher #20 from the Engineer Department of Port Dalhousie and Thorold Railway Extension, for the Northern Division approved by F. Shanly, chief engineer and W.G. Thompson, assistant engineer (copy) June 1857

Pay roll voucher #20 from the Engineer Department of Port Dalhousie and Thorold Railway Extension, for the Northern Division approved by F. Shanly, chief engineer and W.G. Thompson, assistant engineer (copy) June 1857.

Pay roll voucher #25 from the Engineer Department of Port Dalhousie and Thorold Railway Extension, for the Northern Division, for the month of July, 1857 approved by F. Shanly, chief engineer and W. G. Thompson (copy), July 30, 1857

Pay roll voucher #25 from the Engineer Department of Port Dalhousie and Thorold Railway Extension, for the Northern Division, for the month of July, 1857 approved by F. Shanly, chief engineer and W. G. Thompson (copy), July 30, 1857.

Pay roll voucher #32 from the Engineer Department of the Welland Railway for the Northern Division for the month of September

Pay roll voucher #32 from the Engineer Department of the Welland Railway for the Northern Division for the month of September, Oct. 2, 1857.

Pay roll voucher #36 from the Engineer Department of the Welland Railway for the Northern Division for the month of October

Pay roll voucher #36 from the Engineer Department of the Welland Railway for the Northern Division for the month of October, Nov. 3, 1857.

Pay roll voucher #43 from the Engineer Department of the Welland Railway for the Northern Division for the month of December

Pay roll voucher #43 from the Engineer Department of the Welland Railway for the Northern Division for the month of December, Dec. 30, 1857.

Iron Mountain Route Railway schedule: the great through line St. Louis, Arkansas and Texas to the Hot Springs of Arkansas

Iron Mountain Route Railway schedule: the great through line St. Louis, Arkansas and Texas to the Hot Springs of Arkansas.