The National Project addresses to the multidisciplinary study of sedimentary successions, the age of which spans from the intra-Messinian erosional surface (5.6 Ma) to the base of Pliocene (5.33 Ma).
The main areas of investigation are: foreland and wedge-top basins of the central Apennines (Laga, Maiella and “bacini minori marchigiani”), hinterland basins of Tuscany and Latium (Volterra, Radicondoli, Val d'Elsa and Mondragone basins), northern Tyrrhenian basins (Corsica, Punta Ala and Viareggio basins, eastern margin of Corsica and Sardinia), thrust-top basin of Sicily (Caltanissetta, Ciminna and Belice basins), Tertiary Piedmont Basin (eastern part and Monferrato), satellite basins of the Betic Cordillera of South Spain (Sorbas, Nijar e Vera). Further investigations will be carried out in Cyprus, Crete and Malta.
The results will be compared with other sectors of the Mediterranean, such as the northern Apennines and Po Plain, the continental Greece (Ptolemais), Spain (Valencia, Guadalquivir), and Morocco, which have been already studied by the personnel of the Operative Units.
The project of this Operative Unit (OU) focuses on the multidisciplinary study of some of these areas, and also the Unit’s members will provide their expertise to working groups in all the other areas, in order to successfully develop the tasks of the National Project:
-- task 1 – reconstruction of a high-resolution stratigraphic framework of the late Messinian on the base of the chronology of Mediterranean-scale, highly traceable events;
-- task 2 – role of the Tortonian-Messinian tectonics in the origin of the Messinian events of the Mediterranean;
-- task 3 – origin of the widely diffused, intra-Messinian erosional surface and associated sedimentary deposits;
-- task 4 – age and manner of the transition from hyperhaline to hypohaline conditions;
-- task 5 – climatic control on high-frequency cyclicity of the continental deposits of the post-evaporitic stage;
-- task 6 – age, distribution, and paleogeographic meaning of the episodic marine ingressions in the Lago Mare basins;
-- task 7 – depositional characters and diagenesis of the evaporitic facies of the upper Messinian;
-- task 8 – regional synthesis of the Mio-Pliocene transition.
TASK1
The main goal of this OU is the stratigraphic study of some basins in the central Apennines (Laga and “bacini minori marchigiani”) and in the Betic Cordillera and the correlation with the stratigraphy of the other investigated areas.
The Laga basin will be investigated in greater detail. Some litho-stratigraphic characters of the northern part of the Laga basin have been recently defined and are of the greatest importance as to the aim of the Task1: 1) almost all the stratigraphic sections show an ash layer, which can be correlated with a similar horizon in the whole Periadriatic area; 2) an erosive unconformity marks the separation of the post-evaporitic succession in two sequences, which can be correlated with the Tetto and Colombacci Formations respectively by lithological, sedimentological and paleontological observations (Bassetti et al., 1999); and 3) the upper, coarse-grained sequence is arranged in three thinning and fining upward cycles, which are a distinctive character of the upper post-evaporitic sequence in the Apennines and Sicily.
The effort of this OU focusses on to confirm these observation, to extend them as far as the southern edge of the Laga basin, to MIUR - BANDO 2003 - 10 -
PARTE II Ministero dell Istruzione, dell Università e della Ricerca, perform the correlations with the shallow water deposits of northern Marche and Emilia-Romagna sectors of the Apennines and with the turbiditic successions buried beneath the Po-Plain, and to calibrate the physical stratigraphy with chronological data.
As far as the satellite basins of the Betic Cordillera are concerned, their depositional sequences and stratigraphic units can tentatively be correlated with the ones of the Apennines. The main goal of the OU will be, of course, to confirm this correlation. Here too, the post-evaporitic interval lacks a good biostratigraphic resolution, as well as the isolated physiography of the basins makes the local and regional-scale correlation difficult to be done (Krijgsman et al., 2001). However, the sedimentary successions are complete and high frequency sedimentary cycles are easy to be outlined in field. Cyclostratigraphy can be a reliable tool in dating and correlating at a global scale the stratigraphic record on the base of paleontological, geochemical and paleoenvironmental markers.
The goals of the task 1 cannot therefore be achieved without detailed biostratigraphic and chronostratigraphic studies, integrated by mineralogical and geochemical studies. The biostratigraphic framework will be reconstructed by integrated study of foraminifers and palynomorphs. The study of the palynomorphs, due to their wide and almost ubiquitous diffusion, ensures correlations among marine, lacustrine and continental deposits. This is particularly important in reasons of the extreme variability of the depositional environment of the upper Messinian basins. Moreover, levels of high concentration of organic matter have been recognized in the post-evaporitic deposits in several areas of the Mediterranean. These levels can be recognized and characterized by geochemical and minero-petrographic studies, and can therefore be traced in different sections as useful stratigraphic markers.
The interaction with the OUs 1, 3 and 6 is already planned, with special regard to the magnetostratigraphic, biostratigraphic and paleoecological studies. On the other hand, the experts of this Unit will not only work on the sections of central Apennines and Betic Cordillera, but they will also participate to the field and/or laboratory studies in the other areas defined above, or, at least, to contribute at the phase of sovra-regional correlation.
From the stratigraphic and sedimentological study of the basins and the comparison with the seismic profiles we aspect to outline the geometries of the depositional units in the Laga basin and to correlate these units with the ones in the rest of the Po Plain-Adriatic side of the Apennines and the Tuscan and Tyrrhenian basins. The age of the unconformities and their effect on the geometries of the basin infill are keys in order to correlate these surfaces at the regional and Mediterranean scale. This correlation will be extended to all the other areas of investigation with the collaboration of the other OUs. The field data will be integrated by subsurface data (seismic sections and borehole data), which are already available. Other data will be available from collaboration with ENI-AGIP.
TASK 2
As the structural studies are concerned, the definition of the role of the Messinian tectonics in the origin of the Messinian events (task 2) cannot be kept apart from the studies on the origin of the intra-Messinian erosional surface (task 3). The efforts of the OU address to outline the geodynamical conditions of Adriatic sideof the central Apennines during the post-evaporitic stage and to compare the structural evolution of these areas with the northernmost part of the Apennines, the Po-Plain and the Tuscan and Tyrrhenian basins. These results will be achieved through the definition of the dominant tectonic style and the study of the
interaction among the tectonic structures and the evolution of sedimentary basins. It should be noted that a synsedimentary activation of normal faults has been recently pointed out in the post-evaporitic Laga Fm. and related to peripheral bulging (Tavarnelli et al., 1999; Scisciani et al., 2000). This is of particular interest because it contrasts with the contractional style of synsedimentary tectonics recognized in the Po-Plain side of the northern Apennines foredeep.
The definition of the sedimentary bodies and unconformities from field data and seismic reflection profiles (task 1) is of course the
base for the structural studies. The tectonic structures will be mapped through remote sensing and field surveying. The continuation in depth of the structures will be reconstructed by subsurface data and computer-aided construction, validation and retrodeformation of geological cross sections (2Dmove and 3Dmove software). We will concentrate also on field study of the deformation of wet, non-consolidated sediments in the Gessoso-solfifera Fm and the post-evaporitic clastic units. Similar studies have been of the greatest importance for the interpretations of the structural style of the Emilia-Romagna foredeep and wedge-top basins.
The OU will also be involved in macro- and meso-scopic scale structural study devoted to understand the effective role of the compressive structures (folds and thrusts) in the deposits of the Tuscan basins. The presence and the regional meaning of these structures are debated and imply different perspectives of the structural evolution and different geodynamical framework for the entire northern Apennines. This study will be done in close cooperation with the OUs 1, 4 and 7.
Lastly, a common effort of all the OUs will be to outline seriated geological cross sections along two-three transects running from the Tyrrhenian area to the Po Plain-Adriatic foredeep. We will collaborate to realize balanced geological cross section through field and subsurface data, which are either already available (northern Apennines chain, Po Plain, Emilia-Romagna sector of the Apennines margin) or will come from the achievement of this project. Thus, the goal of the National Project is not only to correlate the stratigraphy and geometry of the sedimentary bodies, but also to define the geometry and age of activation of the tectonic structures and their interaction in term of kinematic balance across the Tyrrhenian-Apennines system.
TASK 4
As to the task 4, the vertical changes in paleoecology and paleobiology and geochemical, mineralogical and magnetic properties of rocks along stratigraphic sections can give important informationabout the transition from hyperhaline to hypohaline conditions.
The OU will participate to these studies in the central Apennines and Betic Cordillera basins and all the other areas of the National Project. The changes in paleobiology and paleoecology, pointed out by integrated studies of the associations of molluscs, foraminifers and palynomorphs, can trace important variations in the quality of water and in the basin environment at the hyperhaline-hypohaline transition.
The studies of dinoflagellate cysts can directly give information on salinity rate and temperature of the water masses. More general paleoclimatic indication, such as atmosphere temperature and humidity, can arise from the study of pollen grains and spores.
The horizons of high concentration of organic matter are the sedimentary record of environmental changes, which are often connected to global paleo-oceanographic events. Thus, the investigations on these levels can be useful in this task too. Moreover, the studyofthe organic matter can give information on the amount and quality of the biomes. Mineralogical studies of these organic matter-rich horizons (XRF, XRD, thermal analyses and EGA spectrometry), with particular regard to sulphate and sulphide, help to define the reduction-oxidation conditions.
TASK 5 AND 6
Tasks 5 and 6 are strongly related. The experts of this OU will participate to the stratigraphic and sedimentological studies in all the different areas of the National Project. First, the physical stratigraphy will be investigated to recognize cyclical patterns. The results will be correlated at a regional and Mediterranean scale. In particular, it should be confirmed the correspondence among the sedimentary cycles and the astronomical (precessional) cycles, which has already been pointed out in the foredeep basins of the Po-Plain side of the northern Apennines. Our goal, together with the other OUs, is to extend this correlation to the central Apennines and Betic Cordillera basinsand to the other zone of the National Project.
The paleobiological and paleoecological studies, pointed out above for the task 4, will be important for these tasks too. XRD analyses can give information on the transition between marine and non-marine conditions through the semi-quantitative definition of the magnesium content of the biogenic calcite.
TASK 7
We propose to reconstruct the depositional history of the upper Messinian evaporitic units (“superiori” (upper) evaporites) throughout a systematic study of their sedimentologic, petrographic and isotopic features. The study will focus on different areas (Sicily, Tuscany, Spain) in close collaboration with the other OUs, which will give fundamental contributes in sampling and in the sedimentological studies.
In particular, the OU will study the isotope compositions of the sulphates (sulphur and strontium) and carbonates (oxygen, carbon and strontium) of the successions in order to determine the marine vs. continental inputsto the basins and to investigate the nature of the isolation of the various sub-basins. Local geochemical studies of samples from Mediterranean sites carried out over the last years, show that the lower evaporites exhibit the signature of the Messinian ocean normal marine water, whereas the upper evaporites (Sicily) reflect deposition from a water body isolated from the open ocean (Dinelli et al., 1999; Keogh & Butler, 1999). Such conditions can be considered fully equivalent to the late Messinian brackish-water environment (Lago-mare).
Moreover, microthermometric analyses on fluid inclusions in gypsum crystals will carry out to determine the paleosalinity and paleotemperature of precipitation evolution in the evaporite formation.
These studies will contribute to our understanding of the origin and significance of the “upper” evaporites, to define the paleogeographic and hydrologic characteristics of the Mediterranean sub-basins and supply significant suggestions on the timing of their isolation from the ocean.
Part of the isotopic analyses (strontium, oxygen, carbon) will be done through collaborations with ENI-AGIP, the Louisiana State University and the Università La Sapienza of Rome. The isotopic analyses on sulphur and, in part, strontium would be financed with this program.
TASK 8
This OU will study the Mio-Pliocene boundary in the Laga zone and in the basins of the Betic Cordillera. In Spain and in the southernmost part of the Laga basin (Abruzzi area) it is possible to study the transition from hypohaline to normal-marine conditions, in reason of the continuity of the sedimentary record. Here, the multidisciplinary effort of the OUs 1, 3 and 6 and of our OU addresses to define the age and the sedimentological and paleoenvironmental characters of the hypohaline-marine transition. As to the ages are concerned, the magnetostratigraphic and biostratigraphic characters of the first (lowest) Pliocene deposits will be studied in order to recognize some stratigraphic markers, such as the base of the Threva polarity interval and the five bio-events of the lower Pliocene. This will give us a great potential of correlation with all the other areas of investigations and the sections already studied.
The Mio-Pliocene boundary is not cropping out in the northern part of the Laga basin (Marche region). Here, an erosive unconformity cuts the upper part of the Messinian deposits and marks the base of a transgressive body of Pliocene calcarenites. This area is not suitable for the aim of this task, but to define the age of the top of the Messinian deposits and of the Pliocene transgression can be of the greatest interest in order to achieve the goals of the tasks 1 and 2.

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