Ocean currents and glaciation: the depositional history South of Iceland based on sedimentphysical facies analysis and downhole-logging data

Supervisory Team:

• Katharina Hochmuth
• Jo Whittaker

Brief project description:

The development of oceanic gateways is a crucial factor in the global ocean current system, by manifesting ocean current pathways, enhancing heat transport across the globe and blocking previous established routes. The opening of closing of an oceanic gateway can lead to dramatic changes in the global climate. For example, the opening of the Tasman Gateway manifesting the Antarctic glaciation, or the closure of the Panama Gateway initiating glaciation in the Northern hemisphere. One of these gateways is the Greenland-Iceland-Scotland Ridge (GISR) in the North Atlantic Ocean. This bathymetric barrier between the North Atlantic and the Nordic Seas has been emplaced by the volcanic activity of the Iceland Mantle Plume. It regulates the inflow of cold and dense water from the Arctic Ocean to the Atlantic and therefore into the global ocean circulation as part of the North Atlantic Deep Water (NADW). This winter, the International Ocean Discovery Program (IODP) Exp. 395 “Reykjanes Ridge: Mantle Convection and Climate” drilled three sediment drift sites south of Iceland, which record the behaviour of the oceanic gateway at high resolution.

In this project, we will use the collected physical properties data on the sediment cores, as well as the collected downhole-logging data to investigate the sedimentation regime at the central sediment drift complex, the Bjørn Drift. The sediments recovered at Bjørn Drift range from 13 Ma old carbonates to various flavours of silty clay and iceberg rafted debris. The sediments chronicle the global transition from a Mid-Miocene (13 Ma) warm climate to colder climates with the onset of glaciation in Greenland (~10 - 8 Ma) and the ultimate establishment of a large icesheet in the Northern hemisphere in the Pleistocene (2.58 Ma). This variable lithology makes the two drill sites at Bjørn Drift (U1554 and U1562) prime targets for establishing a sedimentphysical-based stratigraphy exploring the changes in sedimentation behaviour based on regional to global climatic and tectonic occurrences. By using the sedimentphysical parameters collected on the cores as well as the downhole-logging, we will explore different manifestations of sedimentation changes and use industry-standard software packages for enhanced analysis techniques.

Key questions of the project:

• What is the sedimentphysical manifestation of observed sedimentary facies at multiple scales?
• How can we “predict” unrecovered strata in the succession?
• How does the sedimentation at Bjørn Drift react to climatic and tectonic changes such as the establishment of Northern hemisphere glaciation and the activity of the Iceland Mantle Plume?

Skills students will develop during this research project:

• Analysis of sediment-physical and downhole logging data sets
• Use of industry-standard software
• Contribution to a large international scientific ocean drilling project
• Data presentation, analytical and writing skills