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ARTICLE IN PRESS
1580 K. Lambeck et al. / Quaternary Science Reviews 23 (2004) 1567–1598
Interglacial (the age is based on palynological analyses)
beach sands were identified at À120 m (Amorosi et al.,
1999) indicating a subsidence rate of 1 mm yrÀ1.
Bondesan et al. (1995) established a long-term sub-
sidence rate of B1.1 mm yrÀ1 for the Padana Plain of
the Po delta and Kent et al. (2002) found MIS 5.5
deposits at À79 m within a core drilled near Venice,
giving a subsidence rate of 0.6970.06 mm yrÀ1. Further
to the east, near Trieste, the MIS 5.5 levels have been
reported at BÀ20 m (Pirazzoli, pers. comm.) giving an
average subsidence rate of B0.15 mm yrÀ1. Thus there is
no simple spatial pattern for the subsidence within and
along the coast of the North Adriatic Sea other than
that the rates decrease with distance from the Po Delta.
Offshore subsidence rates can be expected to be less than
the coastal values because the rates of sediment
deposition are much less than in the now-onshore part
of the Po Delta itself. In the absence of specific evidence B0 m elevation) to 5.5 ka cal. BP (the mean of 7 ages
from the core sites we assume a value of zero and use the
comparison of the data with the model predictions to
test this hypothesis.
26. Conselice: An inland core from the alluvial Po
Plain at Conselice reached Holocene marine sediment
and indicates that between 6 and 7 ka BP the coastline
occurred more than 26 km inland from its present
position. This data set provides an interesting recon-
struction of local sea-level rise. Two samples (Preti,
1999) define sea level below À9.8 m at 6.7 ka and above
À9.0 m at 5.9 ka. The subsidence for this locality, based
on the core of Amorosi et al. (1999) discussed above, is
assumed to be 1.070.25 mm yrÀ1.
27. Caorle lagoon; 28. Tagliamento Lagoon; 29. Grado
Lagoon: Several cores have been drilled in different
lagoons between Venice and Trieste in which lagoonal
shells and marsh deposits have been identified. Radio-
carbon analyses indicate ages from 0.9 to 9 ka cal. BP at
elevations of À0.90 to À8.30 m (Marocco, 1991, 1989;
Galassi and Marocco, 1999). Shell species have not
always been identified but, because most of the sea-level
markers are based on the peat or marsh horizons, we
assume here that they are associated with lagoonal
environments. Because of this uncertainty positional
error bars of73 m are adopted. Pirazzoli (1998) noted
that because Pleistocene emerged shorelines are lacking
for this region, the possibility for slow tectonic
subsidence should not be ignored. From the evidence
discussed above we have assumed a linear gradient
in the subsidence rate from 0.7 mm yrÀ1 near Venice
to 0.15 mm yrÀ1 near Trieste, giving 0.45, 0.37,
0.28 mm yrÀ1 for the subsidence at Caorle, Tagliamento
and Grado lagoons, respectively. Nominal precision
estimates of 70.2 mm yrÀ1 have been adopted for all
sites.
30. Aquileia: This is a Roman epoch town from the
first half of first century AD and the sea-level marker is
from its fluvial harbour connected to sea level. The
upper surface of paving stones of the quay is now close
to modern water level and the relative sea level at time of
construction must have been 0.8 m lower than today
(Pirazzoli, 1998). Recent research (including scuba-dive
transects) in the adjacent Trieste limestone cliffs by
Antonioli confirms the absence of older sea levels higher
than present. A well-developed submerged marine notch
has been found at À2.2 m at localities between Trieste
and the Croatia coast that appears to be of Holocene
age and this is consistent with subsidence for this section
of the coast. For the present we adopt the above linear
interpolation to give À0.2870.2 mm yrÀ1 for Aquileia.
31. Djerba (Tunisia): Because a diagnostic feature of
the models for the prediction of sea level during the
Holocene is the gradient of isobases orthogonal to the
former ice sheet margins we have included one site from
Tunisia as a further test of the validity of the models.
The evidence is from Holocene deposits on Djerba
island (Gabe"s Gulf) at 0 and 1 m above present sea level
(Jedoui et al., 1998). Ages and elevations for the
individual shells sampled are not given but they range
from 1.8 ka cal. BP (based on the mean of two ages at
between 0.4 and 1.0 m elevation). The shells are not
from lagoonal species and not all shells appear to be in
their in situ position, they suggest that sea levels for the
southern Tunisia coast may have been higher than
present-day level. Since the MIS 5.5 highstand has been
identified here by silici-clastic units of up to 3 m
elevation overlain by carbonate-rich deposits containing
Strombus bubonis up to 5 m above present sea level
(Jedoui et al., 2003), the coast appears to be tectonically
stable and the observations may provide a useful check
on predictions of the north–south isostatic sea-level
gradient.
4. Predicted sea-level change data
Local measurements of sea-level change provide the
temporal variation of the relative position of the sea
surface and the adjacent land. They contain, therefore,
information on both the vertical movement of the land
and the vertical displacement of the ocean surface. The
latter results from change in ocean volume, change in
geometry of the ocean basins, and redistribution of
water within the basins. On the time scale of the glacial
cycles the primary reason for the regional fluctuations in
sea level within the Mediterranean basin is the exchange
of mass between the ice sheets and the oceans as climate
oscillates between cold and warm conditions. The
resulting pattern of change is complex because of the
deformation of the Earth under the changing surface
load of ice and water and the associated gravitational
changes. These are the glacio-hydro-isostatic effects. In
the case of the Italian coast the principal glacio-isostatic