Extending sea loch sedimentary records: OSL dating of shallow marine systems

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Much of our geological understanding of the land surface is due to the application of dating techniques that constrain how the land surface has evolved through time. Sea lochs (fiords) are unique in that they trap sediments efficiently and therefore capture the interactions of land and sea (the land-ocean system), and how those interactions change through time due to climatic fluctuations. This project will demonstrate that luminescence dating techniques can be applied to date ancient sea loch sediments, and that the technique can be a complementary tool to 14C (or other techniques applied to marine sediments). Luminescence dating techniques have advantages over radiocarbon dating, because the age range is longer (from decades to greater than 200,000 years for quartz) than radiocarbon (50,000 years) and it can be applied to almost all sediments. This permits us to extend the sea loch chronology where organic matter is poorly preserved, and where preserved, sediments that are older than 50,000 years in age. Both of these aspects permit land-ocean interactions to be recorded, dated and investigated. The response rates of the land system to deglacation over the last ~ 20 ka is an active area of research, and luminescence dating has the potential to provide a sea loch chronology of the land surface response over that tme period when little orgnic matter is available for 14C. Since luminescence dating also reflects the sediment's transport history, there is additional sedimentary information that can be resolved using this technique. Our project comprises of 3 parts: we will first compare a published radiocarbon chronology from sediment cores collected in Loch Sunart to a new luminescence chronology developed as part of this project. We will extend the luminescence chronology to sediments recording deglacation over the last 20 ka, to demonstrate that this technqiue has the potential to be used to date sediments beyond the limits of radiocarbon. The second part of our research will involve some fundamental experiments on characterisitics that affect luminescnece dating, namely sediment sensitivity and bleaching during transport. These experiments will be conducted on modern sediments collected from Loch Sunart. The final part of the research involves the environmental radiation dose rate of sediments which is required measurement for luminecence dating. We will explore how uranium disequilibium is affected by different sediment lithologies and water contents in sea loch environments, and what adjustments are required to correct for these influences on dose rate over time. As marine datasets grow in number and resolution, we need to build chronologies of the sediment archive accumulating around our coastline in order to understand rates of coastal change, and to advance our understanding of the rich archaeological record that has been drowned by changing sea levels during the Late Quaternary. In addition, with the marine renewables industries growth sediment dating techniques are required to date drowned archaeological sites, and constrain the rates of movement of offshore sand systems. Dating is an imperative for understanding rates of change and OSL dating has the advantage of being widely applied to almost all sediments and environmments, is not reliant on the availability of organic matter, and has the potential to date sediments as old as 200-400 ka (quartz) or a million years (feldspar).