1,720,986 research outputs found
Studio per la definizione del quadro conoscitivo del litorale pisano di base all’attuazione del piano provinciale d’interventi di difesa costiera ed alle relative campagne di monitoraggio programmato: Report II
No full textConvenzione tra la Provincia di Pisa ed il Dipartimento di
scienze della terra dell’Università’ degli studi di pisa per una ricerca dal titolo: studio per la definizione del quadro conoscitiv
Provenance of modern littoral sands of Pisa coast (Tuscany, Italy)
No full textThe studies concern ing longshore drift carried out on Pisa coast go back to the
end of Seventies and are antecedent to the construction of most part of the
coastal defence systems. The subsequent construction of protection structures
has probably modified coastal dynamics.
Therefore, through an agreement between Provincia an d University of Pisa a
multidisciplinary study has been pianned in order to define and widen the
knowledge about the Pisa coasta zone. O ne of these regards the study of
provenance of littoral sands by compositional analysis.
The Pisa coastal area, about 26 km long, belongs to the physiographic unit
comprised between Punta Bianca and Livornesi Mounts and is mainly made by
sand beaches fed from north to south by Magra, Serchio, Arno and Scolmatore
rivers. The last three and particu larly the Arno River feed the pisa n coast even
if in an insufficient way. Beginning from the second half of the nineteenth
century the Arno delta underwent rapid erosion because of severa l factors,
which strongly changed sedimentary budgets.
The petrography of recent sands from the Pisa coast is used to determine their
provenance and thus how their longshore transport and distribution occur.
In respect to previous works the step of sampling has been increased a long
transects norma l to the shore up to the 10 m isobath in order to a better
estimati o n of longshore behaviour.
The modal analysis has allowed us to recognize two petrographic provinces,
from north to the south, which reflect distinct provenances. The northern
province includes lithoquartzose sands, fed largely by the Arno River and, in
small quantities, by the Serchio River. The southern province consists of
quartzolithic sands, less quartzose than sands belonging to the former
province. The moda l analysis and the petrographical characterization of the latter indicate a northward sediment drift. These sands are perhaps supplied
from Secche della Mel oria and/or from Scolmatore River.
Detrital modes of the sands a long transects show some compositional changes .
within a few of these, which may indicate a major complexity in longshore
transport and distribution.
Besides, in arder to evaluate whether the provenance of sands has changed
their characteristics both in space and time, during the last 3000 yr B. P, the
compositional study of sands forming the coastal dune was a Iso carried aut,
sin ce coastal dune alignment represents the position of an ancient shorelin
Fault array evolution in extensional basins: insights from statistical analysis of gravel deposits in the Cecina River (Tuscany, Italy)
No full textTwo statistical analyses of gravel clasts from the Lower Pleistocene deposits in the Lower Cecina Valley (Tuscany, ITA) have been combined to unravel changes in the palaeo-drainage system. Data from 16 outcrops were collected and 6400 clasts described. Facies analysis, micro-palaeontology and macro-palaeontology and petrographic characteristics of the gravel deposits have highlighted the presence of three allostratigraphic units. Clast lithology is the main discriminator among these units. Cluster and principal component analyses of the 6400 clasts have improved understanding of the stratigraphy of the Lower Pleistocene deposits and constrain the re-routing of the lower palaeo-Cecina River from a supposedly south-east to north-west direction to the present east to west direction. Short rivers feeding small fan deltas represented by the oldest allostratigraphic units were abandoned in the Lower Pleistocene, when the re-routing of the Cecina River caused the capture of these streams. This evolution suggests a change in the tectonic regime of the area. The fan deltas developed on the hanging wall of normal faults sub-parallel to the coast; a change to a transtensile tectonic regime caused the deviation of the main river channel toward the present coast and the formation of a pull-apart basin, which is now exploited by the Cecina River. This study illustrates the value of lithological analyses of gravel deposits for understanding the tectonic evolution of an area
Statistical analysis of gravel deposits: a powerfull tool for reconstructing changes in landscape evolution
No full textrnformat1on about the geomorph1c-sedimentary landscape evolution in response
to tecton1cs an d/or relat1ve sea-level changes. The Lower Pleistocene deposits
croppmg aut 1n the Lower Cec1na Valley are a useful means far reconstructing
past changes m the supply area because they represent an ancient coastal
zone. When marine sediments are reworked and conglomeratic layers are
d1scont1nuous the clast litholog1cal analys1s becomes an invaluable tool to
determine stratigraphic correlations between outcrops. Grave l deposits are
part1cular powerfully far th1s arm because they reflect the lithologies cropping
out m the anc1ent dramage area s. Three gravel layers have bee n recognized in
the study area, belong1ng to three d1fferent Allostratigraphic Units (AUs) and
clearly d1splaced by tectonics. Two statistica l analyses of gravel clasts,
mtegrated by facres and paleontolagical data, from the Lower Pleistocene
deposits in the Lower Cecina Valley {Tuscany, Italy) have been combined to
unravel changes in the palaeo-drainage system. Data from sixteen outcrops
were collected and 6400 clasts described. Although facies analysis,
mrcrofmacro-palaeontology and petrographic characteristics of the gravel
depos1ts have h1ghllghted the presence of three Aus, clast lithology difference
has resulted to be the mai n discriminator in their identificati an. Cluster and
principal component analyses of the 6400 clasts have permitted to i m prove the
stratrgraphy of the Lower Plerstocene depos1ts and to constrain the re-routing
ofthe_lower palaeo-Cecina River from a supposedly SE-NW to the present E-W
drrect1on. The dramage systems in zone characterized by the presence of
half-grabens with intrabasin transfer zones tends to intersect the main tectonic
lineaments in arder to cut the footwall and pass to the hanging-wall basins. By
contrast,_ when transfer zones are not present the drainage system tends to
arrange 1tself parai lei to the depression of the half-graben and remains in the
hanging-wall, like the major river of the Tuscany. The absence of deltaic
depos1ts related to the dra1nage system of the paleo-Cecina River in the
outsk1rt of the study area confrrm that during the beginning of the Early
Pleistocene the river flowed northward. The diversion of the paleo-Cecina River
took piace dunng the Early Pleistocene when a strike-slip fault started to create
the Lower Cecina Valley
Definizione del quadro conoscitivo del litorale pisano di base all’attuazione del piano provinciale d’interventi di difesa costiera ed alle relative campagne di monitoraggio programmato. Report Finale
No full textConvenzione Provincia di Pisa-Università di Pisa per uno studio dal titolo "definizione del quadro conoscitivo del litorale pisano di base all’attuazione del piano provinciale d’interventi di difesa costiera ed alle relative campagne di monitoraggio programmato. Responsabile Giovanni Sart
Studio per la definizione del quadro conoscitivo del litorale pisano di base all’attuazione del piano provinciale d’interventi di difesa costiera ed alle relative campagne di monitoraggio programmato: Report I
No full textConvenzione tra la provincia di Pisa ed il Dipartimento di
Scienze della Terra dell’Università’ degli studi di pisa per una ricerca dal titolo: studio per la definizione del quadro conoscitivo
del litorale pisano di base all’attuazione del
piano provinciale d’interventi di difesa costiera ed
alle relative campagne di monitoraggio
programmato (responsabile Giovanni Sarti
Attività di studio e ricerca a supporto degli interventi sperimentali di recupero, protezione e monitoraggio del sistema dunale: Fase C: carta di sintesi alla scala 1:50000 del tratto costiero e analisi composizionale e granulometrica delle sabbie di duna. Note illustrative
No full textClimatic changes during the deposition of "Arctica Islandica Clays andnSands" fm (Lower Pleistocene): evidences from the lower Cecina Valley (Tuscany, Italy)
No full textThe Lower Cecina valley is part of a neogenic extensional basin, located
in southern Tuscany. I t is mainly lengthened in E-W direction an d
yielded by extensional tectonics which interested the whole occidental side
of the Apenines since upper Tortonian.
In the study area, comprised between Riparbella and Casale Marittimo,
outcrops a remarkable thickness of Lower to Middle Pleistocene deposits
that lye in unconformity whether ofiolitic rock or Pliocenic deposits.
The "Arctica islandica clays and sands" fm represents the older of the
litostratigraphic units recognized on the basis of geologica! survey and facies
analysis. It is organized in a transgressive-regressive cycle recording
the transition from an upper-lower shoreface to a fluvio-influenced depositional
environment.
The transgressive sands contain a lot of micro- and macrofossils between
which two of climatic significance as the bivalve Arctica islandica
and the coral referable to Cladocora caespitosa species. The two taxa are
placed at different stratigraphic positions. In fact, while ali the specimen of
Arctica islandica were founded at the base of the Fm, in the first 5 m, beds
of Cladocora caespitosa occur upwards. Arctica islandica lives today over
65° oflatitude with a temperature ranging between 4°C and 13°C and thus
its presence, in the deposits lying immediately over the transgression surface,
witness cold temperature. The present-day distribution of Cladocora
caespitosa is instead ranging between l5°C and 22°C of average temperature
and prefers sites exposed to fine sediments and alluvial inputs. Thus a
phase of warming seems to have occurred during the deposition of the
"Arctica Islandica clays and sands" fm and the Cladocora caespitosa beds
can be related to the maximum flooding conditions at the end of the transgressive
phase
I depositi Del Pleistocene inferiore della Bassa val Di Cecina (Toscana, Italia): ricostruzione stratigrafico-deposizionale e proposta di suddivisione in unità allostratigrafiche
No full textIn the area comprised between the villages of Riparbella and Casale Marittimo (lower Cecina Valley, Tuscany, Italy) a large amount of
Pleistocene deposits outcrops. Through a detailed geological survey integrated with facies analysis five litostratigraphic units, grouped
in three Allostratigraphic Units (UA), have been detected. The oldest (UA7), lower pleistocenic in age, is formed by two litostratigraphic
units (“Conglomerati delle Ginepraie” and “Sabbie ed argille ad Arctica islandica”) showing latero-vertical relationships and are organized
in a transgressive-regressive cycle. The “Conglomerati delle Ginepraie” are arranged in a fining upwards trend and were deposited
in small coalescent deltaic environments. Three depositional facies are recognized within the “Sabbie ed argille ad Arctica islandica”
recording a fining-coarsening and deepening shallowing upward trend. The UA7 lies in unconformity above pre-quaternary deposits.
The second (UA6), lower pleistocenic in age, is also constituted by two heteropic and transgressive litostratigraphic units
(“Conglomerati delle Lame” and “Arenarie e Sabbie di Montescudaio”) lying in angular unconformity on the UA7. The “Conglomerati
delle Lame”, showing a well developed imbrication, were deposited in a foreshore to upper shoreface depositional environment. The
“Arenarie e Sabbie di Montescudaio” are characterized by a high to low planar-cross stratification and sometimes by overturned stratification
and were deposited in a shallow marine environment. The regressive phase of this UA is not preserved due to erosive processes.
The youngest unit (UA4, “Conglomerati di Serra all’Olio”), was instead deposited in fluvial-braided environment and lies in angular
unconformity on the others UA. The middle pleistocenic age of this unit has been inferred on the basis of its stratigraphic position. This
stratigraphic reconstruction strongly conflict from previous interpretations. Important climatic and geological remarks derive from the
finding of two taxa (Arctica islandica and the coral Cladocora caespitosa) at different stratigraphic positions within the oldest unit
(“Sabbie ed argille ad Arctica islandica”). The Arctica islandica testifying cold temperatures (4°C to 13°C) characterizes the first 5
meters of the unit, while beds of Cladocora caespitosa (15°C to 22°C the temperature range of this coral) only occur upwards. We
retain that the deposition of the “Sabbie ed argille ad Arctica islandica” takes place during a warming phase and that the development
of Cladocora caespitosa beds could be related to the maximum flooding conditions at the end of the transgressive phase. This interpretation
leads to some notable chronostratigraphic implications
A threefold research aimed at the reconstruction of an artificial dune (Migliarino-San Rossore-Massaciuccoli National Park, Pisa, Tuscany, Italy): preliminary data
No full textThis research has been carried aut through a collaboration between the Department of Earth
Sciences of the University of Pisa and the Province of Pisa within the BeachMed project. lt has
worked aut a better morpho-sedimentologic definition of a beach-ridge dune system primarily
aimed at the reconstruction of an artificial dune in front of the Presidential House. The study area
belongs to the Pisan coast and extends far about 23 km. lt nearly coincides with the boundaries of
the Migliarino - San Rossore - Massaciuccoli National Park, and is exactly comprised between
Torre del Lago Puccini (Lucca) to the north and Tirrenia (Pisa) to the south; the landward limit of
the area corresponds to the last outcropping beach-dune alignment. This huge dune system has
formed due to the progradation of the Arno River delta during the last 2000 years and at present is
subjected to strong erosion processes.
A multidisciplinary approach has been used in this work. A detailed morpho-sedimentologic
survey (1 :2000) has allowed to group the dune systems into steady, semimobile and frontal dunes.
Dunes which are no more subjected to processes that have previously led to their formation are
called "steady'': they are fixed and characterized by arboreous vegetation. Dunes which can beat
times subjected to erosion and accretion processes and are characterized by shrubbery are called
"semimobile". "Frontal" dunes are active and covered with typical psammophile vegetation.
Moreover, a series of sampling has been conducted far a more accurate sedimentologic
definition of the area. Grain-size analyses have provided the granulometric range most suitable to
the dynamics processes that affect this sector of the coast. First of ali, five transects have been
traced and samples have been taken starting from the beachface to the oldest outcropping beachdune
alignment. On the beach, the beachface, the berms and the backshore have been sampled;
on the frontal dunes, the stoss-side, the crest and the lee-side; and on the steady and semimobile
dunes, the crest and the interdune areas. The transects have been traced by significant locations,
like updrift and downdrift of the Arno and Serchio rivers, and close to the Morto Vecchio River.
Data processing has showed i) a decrease in grain-size moving towards the oldest dunes and ii) a
slightly coarser grain-size of the crest dune sands in respect to the interdune deposits. These
trends are further confirmed by sand vs silt plots.
At last, provenance data derive from the petrographic analysis of a selected group of
samples previously collected for the grain-size analysis and few more from Arno and Serchio
rivers. The petrographic analysis has showed compositional variations within each transect, most
notably the decrease in calcium carbonate moving towards the oldest outcropping beach-dune
alignment. Preliminary data demonstrate that Arno River has represented the major source of
sediments.
In conclusion, this study has produced a better knowledge about this beach-dune system,
and it has even provided useful data on how to improve and optimize any coastal protection
structure local authorities might decide to set up
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