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Sequenze deposizionali del Pleistocene medio nella valle del Fiume Crati presso Tarsia (Calabria).
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Sequenze deposizionali del Pleistocene medio nella valle del Fiume Crati presso Tarsia (Calabria).
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Paleogeographic 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
Stratigraphic architecture of the Salento coast from Capo d'Otranto to S.Maria di Leuca (Apulia, southern Italy)
No full textGlacio-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
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
Stratigraphic architecture of the Salento coast from Capo d'Otranto to S.Maria di Leuca (Apulia, southern Italy)
No full textThe Cretaceous to Quaternary succession of the Apulia Platform cropping out on the eastern coast of the Salento Peninsula shows a special stratigraphic architecture. Whereas on the platform top, i.e. on the Salento Peninsula proper, the succession is at most a few tens of metres thick and is punctuated by unconformities, on the margin and slope of the platform, along the present-day eastern coast of the peninsula, several carbonate systems are laterally disposed and grafted one upon the other. Three of these systems are clinostratified and include well developed reef tracts of Priabonian, early Chattian and early Messinian age. The geologic conclusion of our study is that, since the Late Cretaceous, the eastern coast of the Salento Peninsula grossly coincided with the margin of the Apulia Platform. This paleogeographic element acted as a foreland horst and registered important geodynamic events related to the growth of the adjacent Hellenide and Apennine thrust belts. During the last 60 m.y., the horst carapace was constantly near sea level and sediments were mainly accommodated and preserved on the deep margin and slope of the platform.The Cretaceous to Quaternary succession of the Apulia Platform cropping out on the eastern coast of the Salento Peninsula shows a special stratigraphic architecture. Whereas on the platform top, i.e. on the Salento Peninsula proper, the succession is at most a few tens of metres thick and is punctuated by unconformities, on the margin and slope of the platform, along the present-day eastern coast of the peninsula, several carbonate systems are laterally disposed and grafted one upon the other. Three of these systems are clinostratified and include well developed reef tracts of Priabonian, early Chattian and early Messinian age. The geologic conclusion of our study is that, since the Late Cretaceous, the eastern coast of the Salento Peninsula grossly coincided with the margin of the Apulia Platform. This paleogeographic element acted as a foreland horst and registered important geodynamic events related to the growth of the adjacent Hellenide and Apennine thrust belts. During the last 6..
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