ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

ANNALISA AMATO
Estimating Pleistocene tectonic uplift rates in the
South-Eastern Apennines (Italy)
from erosional landsurfaces and marine terraces
Dipartimento di Scienze della Terra, Universita di Napoli
Federico II, largo S. Marcellino, 80138 Napoli, Italy
The Southern Apennines are part of an arc-shaped Eastverging
thrust system whose activity occurred mainly
between Late Miocene and Early Pleistocene and whose
last phases of thrusting are well recorded along the outer
front of the chain. In this paper a tentative reconstruction
of the Southeastern Apennines tectonic uplift during Pleistocene
time is made using two main sets of data. Those regarding
the Early Pleistocene time interval refer to the
erosionallandsurfaces that were cut on thrusts and imbricates
of the chain front and were uplifted during the very
last phases of compression. The second group of data
come from a stair of ten orders of Middle to Late Pleistocene
marine terraces cut on both the deformed units of
the chain and the uplifted sedimentary infilling of the last
foredeep. This second set of data accounts with more detail
for the vertical movements occurred after the end of
thrusting.
By analysing their spatial and altimetric distribution and
their relationships with Pleistocene piggy-back basin sediments,
the erosionallandsurfaces relics have been ascribed
to two main generations modelled during the middle and
the late parts of Early Pleistocene, respectively.
The flight of marine terraces analysed here is up to 450 m
a.s.l. high and covers a period starting from the beginning
of the Middle Pleistocene untill the end of the Late Pleistocene.
The terraces are not regularly distributed since
their number, extension, and elevation vary from place to
place. In particular, proceeding from North to South (i.e,
from the outer foredeep toward the chain) the terraces increase
in number and become narrower, while the intervening
scarps become higher and steeper. The correlations
among terraces of different sections are based upon three
marker terraces, which are well preserved and almost continuous
along the whole coastal segment. Chronological
data as well as correlations with glacio-eustatic highstands
suggested by the oxygen-isotopic record are used to infer
the age of each order of marine terraces, while the elevation
data refer to the inner edge of each abrasion platform.
The chronological and altimetrical data sets regarding both
erosionallandsurfaces and marine terraces have been plotted
on time-elevation diagrams. Then, the derivative of
these curves are calculated in order to analyse how the
uplift rates vary during the Pleistocene. From this analysis
it emerges that at the time scale of the whole Pleistocene a
generally increasing trend of the uplift rate occurs, which
can be estimated in about 0.25 mm/a.
Beyond this basic long term tendency, a more variable tectonic
behaviour can be noted at least in the Middle and
Late Pleistocene times. For this span of time, in fact, the
50
more numerous available data allows to appreciate fluctuations
of the uplift rate between the two limit values of 0.55
mm/a around 0.500 Ma, and 0.92 mm/a around 0.125 Ma.
Furthermore, during this period the uplift rates are sistematically
higher on the chain than on the foredeep. However,
this tendency seems to stop at 0.055 Ma, since the marine
terrace related to the isotopic stage 3.3 stands at the
constant elevation of 20 m a.s.l. along the whole coastal
sector here considered.
ANNALISA AMATO & NICOLETTA SANTANGELO
Watershed migration in the Southern Apennines Chain:
tectonic-erosion interactions in recent orogen
Dipartimento di Scienze della Terra, Universita di Napoli Federico II,
largo S. Marcellino 10, 80138 Napoli, Italy
The Southern Apenines Chain is an asymmetric wedge that
accreted onto a NE-wards retreating subduction slab (roll
back of the Apulia foreland) between about 14 and 1 Ma.
While the chain was accreting and migrating a back arc basin
(seat of the present Tyrrhenian sea) opened gradually
to the SW side of the wedge. As a consequence of this evolution
the chain discloses an asymmetrical cross profile
with a steep southwestern slope which carries evidences of
the youngest phases of back-rifting, and a northeastern slope
that, on the contrary, appears more gentle and dominated
by features of compressive tectonics.
Due to the young age of the orogenic events, the hydrographic
network of the Southern Apennines still retains some
characters that permit to reconstruct how the tectonic
history of the wedge influenced the evolution of its drainage
system. The main peculiarity of the river network of the
Southern Apennines are: 1) an asymmetric development of
the drainage in the opposite slopes of the chain; 2) the widespread
presence of superimposed gorges in the western
side and of antecedent gorges in the eastern side; 3) the
concentration of the main intramontane pleistocene lacustrine
basin in the western slope too; 4) a decoupling of the
main watershed from the ideal highest summit line which
rests many kilometers to the SW of the watershed.
A large scale analysis of the areal and altimetrical distributions
of erosional landsurfaces of different ages, coupled
with data related to the geomorphological evolution of the
main rivers valleys, allowed to recognize that the main watershed
has been migrating eastwards during Pliocene­
Quaternary times. This migration is the consequence of several
factors which help the tyrrhenian rivers capture the
adriatic ones and progressively cause the main watershed
to shift towards the East. The main important among them
are: i) the progressive emersion of the chain; ii) the asymmetric
cross-profile of the chain; iii) the increase of the
longitudinal gradient of the tyrrhenian rivers caused by the
rifting of the back-arc basin; iiii) the strong subsidence of