local
project:
Based
on the introduction above, the main objective (task 1)
of the research will be to evidence stratigraphic events
at the Mediterranean scale. This will allow the reconstruction
of a high-resolution stratigraphic framework for the Late
Messinian (post-evaporitic interval, Lago Mare, Upper
evaporitic, spanning from 5.6 to 5.33 Ma).
However other task will concur to reach the principal
objectives that are as follows:
Task 2 Role of the Tortonian-Messinian structural phase
in the Mediterranean evaporitic events.
Task 3 Origin of the wide intra-Messinian erosional surface
and related re-sedimented products.
Task 4 Chronology and modality of the transition from
iperaline to ipoaline conditions.
Task 5 Climatic control on the high frequency cyclical
development of the depositional continental systems in
the post -evaporitic phase.
Task 6 Areal and Chronological assessment of the marine
influxes in the LagoMare continental basins and related
paleoceanographic implications.
Task 7 Upper Messinian evaporitic phases depostional and
diagenetic history.
Task 8 Regional synthesis of the Mio-Pliocene transition.
Our research unit will operate basically on stratigraphy.
It thus will support all the other units. In addition
our unit have a particular interest in three points of
the research:
a) Chronology and modality of the transition from iperaline
to ipoaline conditions
b) Areal and Chronological assessment of the marine influxes
in the LagoMare continental basins and related paleoceanographic
implications.
c) The Miocene Pliocene boundary. Despite the fact that
the interval object of our research is characterized by
the lacking of the classical stratigraphic markers, it
will be necessary to evidence sedimentary successions
in order to verify the occurrence of the considered stratigraphic
boundaries (in particular the Mio-Pliocene Boundary) that
are clearly defined by the biostratigraphic point of view
(re-enter of marine species). In this context the support
of a stratigraphic team well be essential to reach the
objective. The research unit infact consists of calcareous
nannofossils and foraminifers specialists having a long
experience in the field and able to interface to the other
research units.
Phases of the research and methodologies applied In order
to reach the objectives we plan to split the work in some
phases. The first phase will consist in a selection of
the existing data focusing our interest on the the Mio-Pliocene
boundary and on the available data regarding marine influxes
in the LagoMare formation.
Phase 2
A following step will see our unit active in the field
in order to evidence and locate sedimentary successions
potentially useful for the study. Our main study area
will be the northern Apennine and the marche basin. Furthermore
we will contribute to the study of the stratigraphic succession
of: Tuscany Extensional basins and Tirrenic basins in
synergy with unit 1 and 7 Sicily compressional basins
(Caltanissetta, Ciminna, Belice etc)in synergy with unit
2 Bacino Terziario Piemontese (BTP) and Spain (Vera Basin)
in synergy with unit 6 In addition, potential area of
comparison will be the Apenninic Foredeep, Cyprus, Morocco.
Phase 3
This phase will consist in the measurement and the detailed
sampling of the stratigraphic successions. We plan a closely
spaced sampling, in order to achieve the best precision
as possible and to underline any potential influx.
Phase 4
As for the analytical approach, the methodologies will
consist in the classical procedures of the paleontological
and stratigraphic research.
In particular the use on nannofossils (minute skeletal
rests of unicellular planktic organisms, constituting
the bulk of the oceanic sediments since the early Jurassic)
potentially are the ideal biostratigraphic tool for this
study. The wide distribution and fast evolution in addition
to the abundance in sediments make them useful for correlation
over long distances. One of the main peculiarities of
this fossilgroup is the fast processing methodology used
for routine analyses (smear slides) and the fact that
very little material is needed in order to study the assemblages.
This peculiarity will be basic in order to make a closely
spaced sampling to detect possible marine influxes in
the continental sediments.
After having evidenced the open marine interval we plan
to integrate the study with the analyses of the planktic
and benthic foraminifers. In fact Foraminifers are protozoan
with a calcareous or agglutinating test living in a wide
variety of brackish and marine environments. Those are
planktic or benthic. The integrated study of the fossil
foraminifer assemblage and in particular the paleoecological
preferences of the single species allow to reconstruct
the paleoenvironmental conditions. In fact while the planktic
assemblage analyses offer the possibility to reconstruct
the structure of the water column, the benthic assemblage
study represent a useful tool to evidence changes at the
water-sediment interface and to deduce also the variation
of the paleodepth.
Subsequently, biostratigraphic analysis will be performed
by means of calcareous nannofossils. Analisys will be
diversified depending on the task.
a) iperaline to ipoaline transition and c)Miocene-Pliocene
transition.
In both cases the study will apply to sections containing
marine sediments in order to assess the time of this transition.
In those marine sediments quantitative analysis will be
performed. The methodology adopted will consist of counting
the specimens present in the fossil assemblage. Counting
of at least 300 specimens in the whole association, to
identify appearances and disappearances of the index forms,
will be carried out during this operation. Concerning
particular groups (es. Discoaster, Sphenoliths, Elicoliths),
the counting will be carried out on a fixed number of
specimens belonging to the same taxa. A further method
will be necessary to identify the Messinian/Pliocene related
events. In this case, because of the little abundance
of the index forms (Amaurolithus, Ceratolithus), the analysis
will consist of a counting on a prefixed area, i.e. on
a certain number of fields of view. Usually, the number
of fields is at least 1000.
b) In order to evidence possible marine influxes in fresh
water sediments, at first qualitative analysis (presence/absence
of autochthonous forms) will be performed on smear slides.
The sampling will be necessary closely spaced, to identify
extremely thin levels as well. In this way, the presence
of these levels and their possible regularity will be
evidenced. Once the marine interval is shown, an integrate
analysis, both on calcareous nannofossils and planktic
and benthic foraminifera will be possible. Analyses will
have, in this case, a paleoecological and paleoceanographic
aim. We plan to perform a quantitative analysis on a fixed
number of specimens of the assemblages, both for foraminifera
and calcareous
nannofossils. In this case the settling-technique will
be adopted to prepare calcareous nannofossils samples.
This technique provides the advantage of a uniform dispersion
of a fixed quantity of sediment over the slide. At least
300-500 specimens per sample will be counted.
Concerning particular calcareous nannofossils groups (es
Rhabdosphaera, Helicosphaera), the counting will be carried
out on a prefixed number of specimens belonging to the
same taxa.
So it will be possible to obtain data related to the assemblage
and to reconstruct the paleoceanographic conditions in
which the sedimentation took place.
The results obtained will be converted in num/mm2 to get
data on the paleoproductivity of these taxa. As for foraminifera,
the analysis will be performed counting about 300 specimens
for a fixed quantity of dry sediment. In this way it will
be possible to work out the number of foraminifera per
gram of dry sediment, that can be used as productivity
index.
Some authors use the plankton/benhtos ratio to estimate
of thepaleodepth. When the ratio gets to zero, are used
some "transfer functions", which provide an
estimate of the paleodepth for every studied assemblage,
knowing the average depth of living benthic forms. The
study of the living benthic assemblages has moreover underlined
the chance to define species clusters typical of a marine
environment, sites with important fluvial fluxes and transition
zones.
Then, the study at a specific level of the benthic assemblage
allows determining the environment in which this assemblage
formed and evolved.
Obviously, the integration with proxies obtained by other
fields of research (paleontology and geochemistry) will
be very important to achieve realistic informations about
sedimentation conditions during these events.
Final aims of this research will be:
· Contribution to the stratigraphy of the iperaline
to ipoaline transition
· Contribution to Miocene/Pliocene boundary biostratigraphy
· Paleoecological characterization of the Miocene/Pliocene
boundary
· Identification of possible marine influxes in continental
sediments (Lago Mare) and their eventual ciclycity
· Paleoecological characterization using foraminifera
and calcareous nannofossils and possible paleoceanographic
implications of
the marine influxes in continental sediments (Lago Mare)
