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A new delphinid record (Odontoceti, Cetacea) from the Early Pliocene of Tuscany (Central Italy): systematics and biostratigraphic considerations
No full textA new partial delphinid skeleton (Cetacea, Odontoceti), from Pliocene sediments of Tuscany (Italy) consists of a fragmentary skull, ear bones, mandible, some vertebrae and rib fragments. The specimen is related to the Pliocene "Stenella" giulii, a species known from four specimens collected in the Pisa hills in the second half of 19th Century. "Stenella" giulii is here referred to the new genus Etruridelphis. Differences between Etruridelphis and all the extant Stenella spp. include: i) larger size of skull ii) wider and flatter premaxillae on the rostrum iii) narrower superior process of the periotic and iv) lower processus muscularis of the malleus. The dolphin is from a 25 m thick section for which foraminifera indicate an Early Pliocene outer shelf or upper slope environment (slightly before 3.98 Ma). The dolphin horizon, 13 meters above the base of the section produces Globorotalia margaritae and G. puncticulata, indicating the MP1 3 zone (Zanclean). Previous biostratigraphic analyses on other Etruridelphis specimens confirm that E. giulii is Early and Middle Pliocene in age
Benthic ostracoda and foraminifera from the North Adriatic Sea (Italy, Mediterranean Sea): A proxy for the depositional characterisation of river-influenced shelves
Full text linkWe investigated the distribution of ostracoda and benthic foraminifera from the shallow (<40 m water depth) river-influenced North Adriatic shelf. Combining faunal and environmental data from a sub-set of literature databases (Breman, 1975; Jorissen, 1988), we recognised the main environmental drivers for ostracoda (grain-size and bathymetry) and benthic foraminifera (organic matter concentration). Integrating these benthic groups, we identified five depositional settings dependent on the relative position from the main source of riverine material: the Po River. Near the Po Delta, where high fluxes of sediment occur, taxa tolerant to organic-rich muddy substrates and oxygen deficiency are abundant (Palmoconcha turbida, Leptocythere ramosa, Ammonia tepida, Ammonia parkinsoniana, Nonionella turgida). Downdrift of the delta, ostracoda discriminate between shallow sandy substrates (Semicytherura incongruens, Xestoleberis spp.) subject to longshore currents and deeper clayey environments (S. incongruens, Palmoconcha turbida), whereas benthic foraminifera are monotonous being represented by taxa tolerant to moderate organic matter concentrations (A. parkinsoniana, A. tepida, Aubignyna perlucida). The mud-loving Cytheridea neapolitana and Bulimina denudata, tolerating high organic matter fluxes, characterise the 20–40 m deep mud-belt subject to the major accumulation of riverine material. Updrift, sandy substrates with low organic matter are typified by S. incongruens, Pontocythere turbida and Milioloidea. Out of the fluvial influence (water depth > 20 m), diversified meiofaunal assemblages occur with ostracoda discriminating sediment-starved areas enriched in sand. Our results demonstrate that the combined use of ostracoda and benthic foraminifera represents a powerful tool for the depositional characterisation of river-influenced shelves and to achieve detailed palaeogeographical reconstructions from shallow marine successions
Facies architecture and Latest Pleistocene-Holocene depositional hystory of the Po Delta (Comacchio area), Italy
No full textIntegrated sedimentological and micropaleontological study of 16 cores and 137 piezocone penetration tests, approximately 40 m deep, in the Comacchio area enables the documentation of the depositional history of southeastern Po Plain in the last 30 ka, in response to fluctuating sea level. Sedimentation within an alluvial plain was the dominant feature across the entire study area during the pronounced sea level fall that culminated in the Last Glacial Maximum. Thin lowstand fluvial sediments form the lower part of a shallow incised valley above the Last Glacial Maximum unconformity, whereas a characteristic paleosol separates the last glacial alluvial plain deposits from the overlying postglacial deposits in the interfluves. Transgressive and highstand deposits show a well-developed stacking pattern of retrogradational (coastal plain and estuarine) and progradational (deltaic) facies. Detailed reconstruction of transgressive paleogeography shows evolutionary features that can be useful for refined interpretation of coeval and ancient analogs. At relatively early stages of transgression (10.5-9 ka B. P.), sedimentation in a coastal plain was restricted to the incised valley, whereas nondeposition and pedogenesis took place on the interfluves. With rising sea level (9-6 ka B. P.), a wave-dominated, barred estuary developed in the former topographic low. At peak transgression, after filling up of the estuarine systems with coastal, back-barrier sediments, wide areas outside the valleys were flooded, aggradation extended onto the interfluve unconformity, and a shallow marine depositional environment developed across most of the study area. The depositional history during the subsequent highstand phase was dominated by progradation of the early Po Delta and reflects the complex interplay between high-frequency sea level fluctuations, climate, subsidence, and autocyclic processes
A depositional model for seismo-turbidites in confined basins based on Ionian Sea deposits
Full text linkThis study investigates Ionian Sea seismo-turbidite (ST) deposits that we interpret to be triggered by major historic earthquakes and tsunamis in the Calabrian Arc. ST beds can be correlated with the AD 1908 Mw 7.24 Messina, AD 1693 Mw 7.41 Catania, and AD 1169 Mw 6.6 Eastern Sicily earthquakes while two previously unknown turbidites might have been generated by the AD 1818 Mw 6.23 Catania and AD 1542 Mw 6.77 Siracusa earthquakes.
Textural, micropaleontological, geochemical and mineralogical signatures of STs reveal cyclic patterns of STa, STb, STc and STd sedimentary units for each earthquake with an associated tsunami. The STa unit contains multiple ST stacks with different mineralogy, geochemistry foraminiferal assemblages and sedimentary structures that are deposited from synchronous multiple slope failures and turbidity currents. The STb homogenite graded mud unit overlying the STa unit is deposited by the waning flows of the multiple turbidity currents that are trapped in the
Ionian Sea confined basin. The STc laminated and marine-sourced unit results from seiching of the confined water mass that appears to be generated by earthquake ruptures combined with tsunami waves. The STd unit is a tsunamite cap deposited by the slow settling suspension cloud created by tsunami wave backwash erosion of the shoreline and continental shelf. This tsunami process interpretation is based on the textural gradation of the upper unit and a more continental source of the tsunamite cap which includes C/N >10 and the presence of inner shelf foraminifera with a lack of abyssal species. This interpretation is in agreement with the lack of a tsunamite cap for the turbidite likely linked to the AD 1542 historic earthquake that is not associated with a tsunami. The new sedimentologic criteria identifies the final seiche and tsunamite cap deposits of STs and provides a model that can now be tested in other locations to better understand the different depositional processes of seismo-turbidites in confined basins
Stratigraphic architecture of Late Quaternary deposits in the Piombino coastal plain (western Tuscany) as revealed by subsurface data
No full textIntegrated sedimentological and micropalaeontological analysis of a 105 m long core (Vignarca) from the Piombino alluvial plain, in western Tuscany, provides evidence for a Late Quaternary transgressive event within a monotonous vertical succession of alluvial plain deposits. This transgressive pulsation, recorded in the core at about 20 m depth and assigned to > 43 ka on the basis of radiocarbon dating, is documented at Vignarca (3 km landward of present shoreline), through identification of a lagoonal/bay facies association, about 3 m thick, bearing a diagnostic brackish-water microfauna. Pollen data show a close relationship betwee n initial transgression and the development of mixed Mediterranean and broadleaved forest vegetation, indicating that transgression took place at the onset of a warm (interglacial) period, replacing the previous cold-climate (late glacial) vegetation. Comparison of pollen spectra from core Vignarca with coeval pollen series from the Mediterranean area suggests an age attribution of this transgressive episode to the Tyrrhenian (OIS 5e) transgressive event
An integrated approach to aquifer characterization from Lower Arno plain, (Tuscany, Italy)
No full textPaleogeographic and paleoclimatic evolution of the Po plain from 150-KY core records
No full textIntegrated sedimento logica! and micropaleontological (foraminifera, ostracods, pollen) analyses
of eight continuously-cored boreholes, 150 to 270 m deep, reveal the depositional history and the
paleoclimatic evolution of southeastern Po Plain· (northern ltaly) during the last 150 ky.
Facies analysis, carried out through identification of 20 facies associations and 12 microfossil
assemblages, and detailed stratigraphic correlations across severa! tens of km show a cyclic stacking
pattern of facies (including continental, littoral and shallow-marine deposits ), which defines two
fom1h-order sequences deposited during the last two glacial-interglacial cycles. Two prominent
stratigraphic markers, corresponding to wedge-shaped coastal sand bodies, are recorded between 0-
30m and l 00-125m core depths. These bodies were deposited during the twç> major transgressive
pulsations and subsequent sea-level highstands of the las t 150 ky, assigned to the Tyrrhenian ( oxygen
isotope substage Se) and the Holocene, respectively.
Stratigraphic architecture of both cycles shows similar patterns of còastal evolution withchanging
sea leve!. Hiatal surfaces, characterized by basinward shifts of facies and paleosol
development, mark sequence boundaries, overlain by alluvial plain deposits. The transgressive
deposits invariably reflect the onset of a coastal plain and the landward migration of barrier-lagoonestuary
systems, whereas highstand deposition was characterized by extensive delta and strandplain
progradation.
The key surfaces for sequence-stratigraphic interpretation are identified readily by lithofacies
changes and/or important variations in the micropalaeontologic associations. The transgressive
surfaces are considerably easier to identify than the other key surfaces and display diagnostic pollen .
signatures. Pollen assemblages in the transgressive (TST) and highstand (HST) deposits of both
Tyrrhenian and Holocene age indicate warm periods, characterized by the development of interglacial
mixed deciduous broad-leaved forests. A characteristic four-steps evolution of vegetation is
recognized in the TST and HST of three long~cored pollen seri es, providing evidence for synchronous
changes in climatic conditions between glacial-to-interglacial and interglacial-to-glacial transitions.
By contrast, abrupt shifts to very Jow pollen concentrations and pollen spectra dominateci by Pinus and
non-arborea! pollen types at the base of stratigraphic intervals dominated by alluvial deposits (fallingstage
and lowstand systems tracts), are interpreted to reflect the onset of glacial periods.
The good match between facies architecture, pollen distribution and global sea-level evolution
strongly suggests that late Quaternary sedimentation in the Po Basin developed under a predominantly
glac~o-eustatic contro!. Stratigraphic architecture of the Po Basin thus can provi de a useful analog for
interpretation and correlation in the stratigraphic record of very rapid glacio-eustatic (fourth-order)
cycles with frequencies of about l OOky
Glacio-eustaic signature in Late Quaternary deposits of northern Italy
No full textlntegrated sedimentological and micropaleontological
(foraminifera, ostracods, pollens) analyses of 11 continuosly-cored
boreholes, 150 to 270 m deep, reveal the depositional history of
the Po Plain (northern ltaly) during the late Middle PleistoceneHolocene.
Facies analysis and detailed stratigraphic correlations
across severa l tens of km show a cyclic stacking pattern of facies,
including continental, paralic and shallow-marine deposits. In
landward direction, marginai marine deposits are replaced by
alluvial sediments, showing regular alternations of coarse-grained
(fluvial channel) and fine-grained (floodplain) deposits.
Two rnajor transgressive pulsations, marked at relatively
seaward locations by the onset of littoral and deltaic
sedimentation, with landward transition to delta plain and then
floodplain deposits, are recorded in the uppermost 120 m and
correspond to two prominent stratigraphic markers. These
transgressive episodes, that were characterized by the
development of interglacial mixed deciduous broad-leaved forests,
can confidently be attributed to the past two interglacial events
(oxygen isotope stages 1 and 5e). In contrast, abrupt shifts to
alluvial sedimentation dominated by Pinus and non-arborea!
pollen types are interpreted to reflect the onset of glacial periods.
The good match between facies architecture, pollen
distribution and global sea-level evolution strongly suggests that
sedimentation in the Po Basin developed under a predominantly
glacio-eustatic contrai. Subsidence exerted an important contrai in
determining changes in accommodation
Anatomy of an incised-valley fill from Late Quaternary depists of western Tuscany, Italy
No full textThe Late Quaternary succession of the Italian Tyrrhenian coast contains several
paleovalleys, formed as a response to the last Quaternary sea-level fall. One
paleovalley, cut by the Arno River in the Pisa area (Western Tuscany), exhibits 30 m
of incision, is approximately 5 km wide, and can be traced landwards for
approximately 20 km. At seaward locations, post-glacial sediments attain a thickness
of about 60 m. A significantly thinner (17 m) succession of Holocene deposits is
recorded on the interfluves. A chronologic control for the study succession is ensured
by radiocarbon dating.
Two distinct phases of incised-valley fill (IVF), fluvial and estuarine, forming a
fining-upward succession with gravel-sand channel deposits overlain by heterolithic
facies, are distinguished below the Holocene shoreface ravinement surface. These,
corresponding to the lowstand systems tract and to the early transgressive systems
tract (TST), respectively, are overlain by a suite of transgressive barrier and offshoretransition
deposits (late TST), which are overlain by prograding prodelta, delta front
and delta plain sediments (highstand systems tract).
Detailed pollen data document an abrupt change in vegetation type at the
fluvial/estuarine transition. Lowstand deposits in the lowermost IVF show evidence of
a cold-climate vegetation, suggesting that fluvial deposition took place during the Last
Glacial Maximum. A close relationship is observed between initial transgression and
the development of mixed, broad-leaved woodland, indicating that deposition in a
wave-dominated estuary occurred at the onset of the ensuing warm (interglacial)
period. The close match between the vertical stacking pattern of facies and pollen
distribution suggests that sedimentation in the Arno Basin was driven predominantly
by combined eustatic sea-level changes and climatic variations.
Identification of the unconformity at the base of the incised valley (sequence
boundary) from core data is equivocal, due to superposition of lowstand fluvial
deposits on similar, poorly-preserved alluvial sediments formed during the previous
phase of falling sea-level, between 125 ky and 20 ky BP. By contrast, the
transgressive surface has a distinctive facies and pollen signature and appear as the
most readily identifiable surface within the valley fill for sequence-stratigraphic
interpretation. Micropaleontological (benthic foraminifer and ostracod) data allow to
refine the overall scheme of facies architecture, and enable precise positioning of the
maximum flooding surface within an apparently monotonous, clay-dominated
succession
Stratigraphic architecture and aquifer system in the eastern Valdarno Basin, Tuscany
No full textDeveloping a realistic model of high-resolution stratigraphy from the subsurface of modern alluvial and
coastal plains is an important first step toward a successful three-dimensional representation of aquifers and
aquifer systems. An integrated (stratigraphic, sedimentological and micropalaeontological) study of six cores,
100-115 m long, from the eastern Valdarno Basin, Tuscany, enables the detailed reconstruction of Pliocene to
Quaternary subsurface architecture between Pontedera and S. Croce sull’Arno. Pollen data from lagoonal sediments
and strontium isotope dating of shallow-marine deposits provide the basis for the construction of a reliable chronologic framework for the study succession.
Stratigraphic correlations, based upon detailed facies analysis, show a varied facies architecture in the study
area. Beneath the Holocene succession, which is about 40 m thick and consists of alluvial deposits resting onto
transgressive swamp clays, pre-Holocene deposits display remarkably different characteristics from Pontedera
toward the basin margin, likely as a result of tectonic activity due to a normal fault running parallel to the
Apenninic chain. In the Pontedera area, a thick succession of Pleistocene alluvial deposits, showing a cyclic
alternation of fluvial-channel (gravel/sand) and floodplain (clay) facies associations is the dominant stratigraphic
feature. By contrast, lower-middle Pliocene deposits, characterized by alternating coastal and shallow-marine
deposits, with very subordinate alluvial facies, are recorded at shallow depths, west of S. Croce.
A significantly improved stratigraphic architecture in the uppermost 100 m enables detailed reconstruction of
aquifers geometry in the eastern Valdarno Basin. With respect to previous work, documenting the presence of
one aquifer only, a multilayered confined aquifer, made up of five aquifer systems ranging in age from Middle
Pliocene to Holocene, is identified in this study. Lenticular and sheet-like geometries of these aquifer systems
are reconstructed, as a function of the alluvial versus littoral origin of their constituent deposits. According to the
geological framework, the Pliocene to Quaternary sands cropping out on the Pisa Hills are likely to represent the
meteoric-water recharge area for the aquifers of the eastern Valdarno Basi
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