Sack Lunch Seminar (SLS)

In situ cosmogenic nuclides are produced in surface materials exposed to cosmic radiation - cover a landscape with ice and production ceases; erode down into a landscape and nuclide concentrations quickly decrease. We used these simple observations to explore a new proxy for reconstructing past ice sheet variability- the 10Be concentration of sand in marine sediments adjacent to glaciated continents, which should reflect the exposure and erosion history on land before the sediment was deposited in the deep sea.
This talk will present cosmogenic nuclide records from two Ocean Drilling Program cores off east Greenland and the ANDRILL-1B core next to the East Antarctic Ice Sheet spanning the past 8 Myr, as well as 10Be measurements on contemporary sediments emanating from the southern Greenland Ice Sheet today. Notable features of the Greenland record include a 50-fold long-term decline in 10Be concentration reflecting late Cenozoic ice-sheet growth, pronounced 10Be dips coincident with major ice-rafted debris pulses, considerable variability during the early Pleistocene, and low concentrations indistinguishable from contemporary sediments throughout the past 1 Myr. The Antarctic record, on the other hand, exhibits very low 10Be concentrations over its entire length, suggesting little to no subaerial exposure of land where the sediment was sourced from during the past 8 Myr.