2020 11 AUSTRALIA ICE AGE GEOLOGY OF THE GREAT BARRIER REEF #IceAgeGBR 11/22/20 - 12/17/2020 Queensland University of Technology, James Brisbane, Australia Cook University, University of Sydney, University of Dr. Mardi McNeil Queensland, Geoscience Australia, AusSeabed. Dr. Jody Webster Expedition Objectives The upper continental slope and shelf edge of the southern Great Barrier Reef was largely unknown and poorly mapped Mapping Expedition prior to the Ice Age Geology of the Great Barrier Reef (GBR). The goal of the expedition was to explore ancient undersea features The expedition systematically mapped in the southern extent of the GBR that formed during the last the shelf edge and upper continental Ice Age, when sea level was almost 120m lower than it is today. slope at the Capricorn-Bunker Reefs, While once an exposed part of the Australian coastline, these Capricorn Channel, and Swain Reefs in features submerged, or ‘drowned,’ as glaciers and ice sheets the southern extent of the GBR. melted creating rising sea levels flooding Australia’s continental shelf. R/V Falkor’s team utilized high-resolution multibeam sonar Ice Age Geology to search for these past shorelines, drowned reefs, pinnacles, and The research team searched shelf-edge terraces, as well as ancient river channels and deltas. for geologic features that were submerged when sea level rose The expedition completed the most comprehensive systematic after the last Ice Age. These geologic multibeam mapping of the southern extent of the GBR along the features include pinnacles, terraces, shelf-edge and upper continental slope. river channels, and reefs. The science team mapped more than 400 kilometers of Measure Atmospheric Particles submerged shoreline, and systematically mapped the 50 to A supplementary project was conducted 120 meter depth range. The maps revealed the drowned reef for the Reef Restoration and Adaptation terraces, pinnacles, beaches and shorelines, river channels and program measuring atmospheric deltas that the science team expected to see. This depth range aerosol particles for a potential cloud- is significant because it contains geologically and ecologically seeding program designed to shade significant submerged features that formed between 10,000- and cool the GBR. 20,000 years ago when sea level was 120 meters lower than today. REPORT IMPACT 12 Sediment sampling is an important part of the study. Finding ooids in such deep water helps the science team to learn about the ancient geological makeup of the Great Barrier. 30 01 13,046 days at CTD km2 sea cast mapped UNDERSTANDING THE MEASURING PAST STORMS GBR’S HISTORY The data analysis and results The shape of the submerged will inform new models of the coastlines, in particular the paleo- growth and evolution of the shorelines and beach ridges, will southern GBR from 20,000 years be used to inform the timing and ago to the present. magnitude of past storm events. FUTURE RESEARCH PROTECTING THE FUTURE PROPOSALS OF THE GBR The mapping data will be The atmospheric aerosol data used to develop proposals for will be used to inform a feasibility geophysical surveys and the study on cloud brightening for collection of core samples to shading and cooling the GBR as better understand the GBR. part of the Reef Restoration and Adaptation Program. MODELING THE PAST DATA FOR MANAGEMENT Future analyses of physical All of the data is collected in samples will inform revised sea collaboration with Geoscience level curves for the southern Australia and the Great Barrier GBR, as well as paleoclimate and Reef Marine Park Authority, and paleoceanographic models. will be used in future management decisions of the GBR. .