In any discussion of the evolution of a river basin, the history of sealevel
change is important since river gradients and delta developments are
strongly influenced by local sea level. Also, sea level provides a reference
for inferring past vertical tectonic stability from the geological record.
Hence it is appropriate that the discussion on the Tiber basin starts with sea
level change along the Tyrrhenian coast during the Holocene.
The past evidence for sea level comes from inferences of the position of
the sea surface with respect to the present. Hence it is a relative measure; a
function of both the changing position of the ocean surface and of the land
surface or an integrated measure of changes in ocean volume, land movement
and redistribution of water within the ocean basins. The observation
therefore contains information on all the processes that change these surfaces:
on geophysical, glaciological and oceanographic processes
