Glacial Advances and Retreats in Tectonic Southeast Alaska During the Little Ice Age and Last Glacial Maximum: Preliminary Results from EW0408

In glacially dominated environments climate is linked directly to the earth processes of erosion and sediment deposition with some of the smallest time lags of any geological process. A cruise on the R/V Maurice Ewing that combines high-resolution seismic reflection surveys with ultra-high resolution chirp, EM1002 swath mapping, jumbo piston-coring, multicoring, multi-sensor track logging, and CTD/water sampling from Aug. to Sept., 2004, examined these processes in 30 sites throughout the fjords and continental shelf of tectonically-active southeast Alaska. Geophysical imaging of shelf depocenters and fjord sub-basins allows for tracking of Last Glacial Maximum (LGM) and Little Ice Age (LIA) ice streaming (advances) and glacial retreats. Glacial advances through ice streaming can be tracked by the presence of terminal and lateral morainal banks and extensive deposystems. We present patterns of ice streaming and the resulting sediments from the Lynn Canal/Glacier Bay systems, the Malaspina/ Hubbard glaciers, the Bering glacier, and the glaciers within Prince William Sound. Patterns of convergent and divergent ice flow result in differing deposition patterns and are sometimes reflected in modern shelf topography in features such as shelf valleys and banks. Glacial retreat can be incredibly rapid with the Glacier Bay systems retreating 100 km in \u3c 250 years. The dominant pattern of glacial retreat both for the LIA and LGM retreats are a series of sub-basins imaged within the structurally-controlled fjords showing an episodic retreat style with the greatest volumes of sediments being deposited ice proximally, and the amount of post-glacial drape being dependent on time since the retreat. Rates of sediment deposition are extreme; for example, the second sub-basin of Muir Inlet has accumulated 65 m of paraglacial sediment in the 45 years since direct glacial influence