of the Holocene and last interglacial episodes of transgression. These are specifically important since they have been profoundly influential in governing the present configuration of our coastal plains, coasts, and shelves. The longer-term processes included in the graph are the tectonics of crustal movement at the coastal interface, processes such as continental margin subsidence, changes in basin configuration, and global tectonics that govern the degree of continental freeboard and the fundamental timing of shelf evolution.
The second axis of Figure 4 shows the spatial scales of sedimentary features involved in research investigations. This list is only suggestive of the range of scales and is not an exhaustive account of the many sedimentary bodies found at the ocean margin. At the smallest scale are the sediment particles, obviously important in studies of sediment transport, but also important in the record of grain-size distributions of particles within the resulting deposits that reflect the transport processes. Accumulations of sediment grains form sand ripples or the bars that are an important part of the overall beach morphology, or the large-scale sand waves found in some shelf environments. These morphological features combine to form the entirety of deltas, estuaries, barrier islands, and the present-day shelf. Recorded within the sediments of the margins are ancient shelves, stranded sand bodies, fossil reef tracts, and a stratigraphic record of former changes in sea level.
To a degree, individual research efforts can be placed within the temporal-spatial scale of the accompanying graph. These tend to congregate along the 45° zone shown. For instance, investigations of sediment-transport processes focus on the time scales of waves and currents and down to the scale of turbulent fluctuations, while considering the movement of sediment grains and the effects of sand ripples on that transport. Other investigators document the response of beach morphology to the occurrence of storms, or the formation and migration of sand waves on the continental shelf where sediment transport is due to tidal currents. Yet another group of investigators is focusing on the effects of sea-level change, with the impacts ranging from the present-day changes in coastlines and estuaries to the long-term record within the stratigraphy of the continental margin. The unique ratio of morphologic and dynamic integration that constitutes research on the shelf and shoreface falls within this "morphodynamical corridor."
There is a notable lack of continuity and overlap among separate groups that study discrete morphodynamical ranges. A challenge to our science is to improve the linkage among these research subdisciplines. We must learn to talk to one another more often, and more effectively. Any one investi