Constraining the history of post-glacial sea-level rise using high-resolution seismic imaging of seafloor sediments in Fiordland, New Zealand
Following the rapid retreat of local glaciers after the Last Glacial Maximum, most of the modern fjords of southwestern New Zealand were isolated from the Tasman Sea by bedrock and moraine sills, because sea level at that time was about 120 m lower than it is today. The isolated lake basins were subsequently inundated with seawater when post-glacial sea-level rise, which continued until about 6500 years ago, overtopped the sills. A record of the lacustrine-to-marine environmental transition is preserved in fjord basin sediments and has been identified in several fjords with high-resolution (boomer and CHIRP) seismic data and paleoenvironmental analysis of sediment cores. Seismic data can be used to constrain the maximum sill depth and microfossil assemblages are used to track the lacustrine-to-marine transition. Together these datasets – from a relatively tectonically stable region – are used to refine the detailed history of post-glacial global sea-level rise.