he sea bed and actually be able to trace the channel system. And most importantly, the very fine deposits that settle within it during both this period of time it was active and also during the transgression itself.
Skip to 2 minutes and 6 secondsSo if we switch the swath bathymetry off, we can actually see the seismic lines that are penetrating beneath the sea bed surface underneath the actual sandbank. If we look at a window just focused on one of these seismic lines and we zoom in, we can actually see the ancient paleo channel buried beneath the actual sandbank itself and preserving very fine grain sediments, including potentially organics and peat, which can give us lots of information about the environment. It can give us a date. And in really exceptional circumstances it can actually preserve archaeological materials.
Marine geophysics for submerged landscape investigations
This video gives two contrasting examples of submerged landscapes imaged via a range of marine geophysical instruments.
The first is from the Bristol Channel, a system starved of sediment so ancient pre-transgression (sea-level flooding) land surfaces are still visible on the sea bed. Consequently, they can be imaged by swath bathymetry and other high resolution bathymetric techniques to allow us to produce an accurate terrain model of the area. The regional model shown in the video is actually produced by integrating a range of datasets (work done by the UKHO) to give a map at a 20 x 30 m bin resolution. In places higher resolution datasets (swath), as well as some sub-bottom data and cores, have enabled more detailed study of some of the buried sections of this land surface. Burial has resulted in preserved fine grained deposits, including peats, which has not only enabled us to date when this land surface was last exposed (just under 10,000 years ago), but also to provide a more detailed understanding of the palaeo-environment and even some potential indicators of human activity.
The second example is from the Thames estuary, where a large scale river system has been buried underneath a large sandbank. Here very high spatial resolution, swath bathymetry and sub-bottom profile (boomer) data has been acquired, as part of a large windfarm project, and from which a full 3D reconstruction of the channel system and the deposits it contains can be made. This system has again been cored, and sediments dated, but in this case the channels have evolved over multiple lowstands (periods of time when sea level was lower) over almost the last million years. These landscapes are therefore potentially contiguous with the deposits that contain the oldest evidence of hominin occupation in the British Isles (indeed North of the Alps) which are found on the adjacent Suffolk and Norfolk coast.
© University of Southampton, 2017