1,721,037 research outputs found
The Crosia-Calopezzati basin (Cosenza, Calabria): a paradigm of coastal to open-marine correlation
No full textThe Geologic Time Scale and the Italian Stratigraphic Record
No full textThe construction of the Geologic Time Scale (GTS) is a
titanic scientific challenge that has been under way for
two centuries and will require much dedicated effort in
the future. Italy preserves a paramount stratigraphic
record of Mesozoic and Cenozoic marine sediments that
have been significant in the development of the modern
GTS. The Italian stratigraphic record has been historically important in introducing and defining the standard
Chronostratigraphic Units (CUs) of the Neogene and
Quaternary. Pelagic successions from Northern Apennines and Southern Alps have been used in the seventies
for integrating the late Cretaceous-Paleogene Geomagnetic Polarity Time Scale (GPTS) with planktonic
microfossil biostratigraphy and standard CUs. This was
a major contribution to the construction of a new generation of GTS based on integrated magnetobiochronology. The middle Miocene to early Pleistocene marine record from Sicily and southern Italy has been fundamental for establishing the recently developed Astronomical Time Scale (ATS). In prospect, there are many potentials still to be exploited in the Italian marine stratigraphic record for implementing the GTS by defining GSSPs of various CUs, improving magnetobiochronology and extending downwards the ATS
Climatic Modulation of Timing of Systems-Tract Development with Respect to Sea-Level Changes (Middle Pleistocene of Crotone, Calabria, Southern Italy)
No full textClimate change has traditionally played a secondary role in the literature behind eustasy and tectonics, with eustasy regarded as the main controlling factor in development of sedimentary sequences. Here, we emphasize the role of the interaction of climate-modulated sediment supply and sea-level change, particularly its potential impact on sequence development.
We discuss a case history from the lower–middle Pleistocene of the highly subsiding Valle di Manche shelf area (Crotone Basin, Calabria, southern Italy), where a stack of cyclothems spanning from late Marine Isotope Stage (MIS) 22 to full MIS 18 preserves a full record of eustatic cycles, glacials included. Tectonics certainly played a critical role in the creation of local accommodation, ultimately controlling the preservation of an almost complete sedimentary record. However, its role as a factor controlling the sediment flux on Milankovian scale can be ruled out. Direct comparisons between data concerning δ18O, pollen, and physical stratigraphy demonstrate that climate-induced changes in sediment load caused significant deviations from the predicted timing and magnitude of the responses to sea-level changes in the traditional sequence model. A phase lag occurred in the timing of systems tracts, leading to a significant delay of one-quarter of a sea-level cycle. Specifically, climate-driven sediment discharge during sea-level rise triggered progradation of shelf-margin wedges, which should thus be considered lowstand in their architecture and "transgressive" in their timing. This was generated by a shift toward drier conditions, leading to extensive deforestation and consequent lowering of the threshold for slope erosion and mass-wasting processes in the source area.
Due to the reduced extent of the transfer zone, sedimentary signals were conveyed rapidly from source to sink with little apparent attenuation, suggesting that the Milankovitch-scale climate changes can lead to rapid source-to-sink responses on tectonically active margins fed by high-gradient, short-headed streams. The studied case history demonstrates that the impact of Milankovitch-scale climatic forcing on sediment supply in an icehouse world can be more supluential than sediment redistribution due to corresponding sea-level fluctuations.
These findings emphasize that a reconstruction of the timing of systems-tract development with respect to sea-level changes based on a sequence-stratigraphic approach may be misleading, whenever independent chronological and climatic constraints are not available
Palaeocologic signatures of fossil assemblages in a candidate GSSP section of the Middle Pleistocene Stage at San Mauro Marchesato (Crotone, Southern Italy)
No full textMarine ostracod turnover tracks orbitally forced palaeoenvironmental changes at the Lower-Middle Pleistocene transition: the case study of the Valle di Manche section (Calabria, southern Italy)
No full textOstracods, small crustaceans living in almost every aquatic depositional setting, are widely used in palaeoenvironmental reconstructions due to their well-known ecological sensitivity. A close connection between the composition of ostracod fauna and the Milankovitch climate-eustatic variability has been documented in several Plio-Pleistocene marine sections of the Central Mediterranean area. The Valle di Manche section (VdM; Calabria, southern Italy), one of the suitable candidates to host the Global Stratotype Section and Point (GSSP) of the Ionian Stage-Middle Pleistocene, represents an ideal venue where to investigateostracodturnoverinrelationtoorbitallyforcedpalaeoenvironmentalchanges,beingfirmlyconstrained in time and well documented by a number of independent climatic proxy. A high-resolution, quantitative analysis of the ostracod fauna has been undertaken on the middle part of the VdM, ca. 30 m-thick and showing two T-R cycles developed at the Lower-Middle Pleistocene transition (late MIS 21 to early MIS 18). Within each cycle, a relatively thin, fining-upward transgressive muddy unit is overlain by gradually coarsening upward and more expanded regressive silty to sand packages. A total of 40 samples have been selected to characterise the whole spectrum of lithofacies and detect highfrequency palaeoenvironmental variations especially within homogeneous clayey stratigraphic intervals. Taxa typical of circalittoral (>70/100 m) depths (e.g., Bosquetina dentata, Cytherella vulgatella, Cytheropteron monoceros, Pterygocythereis ceratoptera and Krithe species), commonly accompanied by the lower circalittoralbathyal species Henryhowella sarsii, occur within the fine-grained units developed during the full interglacials of MIS 21 and MIS 19. Furthermore, ostracod assemblages document that the oxygen availability at the sea floor changed during MIS 19. In contrast, a less-diversified ostracod fauna dominated by Aurila convexa, a species preferring vegetated sandy substrates in the upper circalittoral zone, characterises coarser glacial deposits. Atop the sandy successions A. convexa is partially replaced by Semicytherura ruggierii, suggesting a further decrease in palaeobathymetry and, possibly, an increase in riverine influence. Within each T-R cycle vertical changes in ostracod fauna track both an overall deepening-shallowing upward trendandhigh-frequencyvariationsinstratalstackingpatterns,allowingthepreciseidentificationofkeysequence stratigraphic surfaces: Transgressive Surface (TS) and Maximum Flooding Surface (MFS). The former, which is marked by a sharp increase in Krithe, Cytherella and Cytheropteron species, develops during the late d18O glacial termination. The MFS, invariably highlighted by concomitant highest and lowest percentages of H. sarsii and A. convexa respectively, matches the lightest d18O values recorded by foraminifers and corresponding to full interglacial conditions. Within the MIS 19 muddy unit, the MFS is identified few decimeters above the Pitagora ash layer, a prominent bed close to the Matuyama-Brunhes geomagnetic reversal
Chronology of the Pliocene succession in the Strongoli area (Crotone, southern Italy): disentangling tectonics from glacioeustasy
No full textChronology of the Middle-Upper Pliocene succession in the Strongoli area: constraints on the geological evolution of the Crotone Basin (Southern Italy).
No full textThe aim of this study is to reconstruct the evolution of the Strongoli area, a critical sector of the Crotone Basin (Calabria, Southern Italy), where a thick Middle-Upper Pliocene marine succession is present. The Strongoli succession shows prominent changes in the sedimentary environment that are partly forced by tectonics. Major tectonostratigraphic events have been recognized that might correlate with spreading pulses in the back-arc Tyrrhenian Sea. In particular, we demonstrate that a dramatic basinal collapse at c. 2.3 Ma correlates with the so-called 'Calabrian transgression' Auctorum and is close in age to the oceanization of the Marsili Basin
A revision of the stratigraphy and geology of the south-western part of the Crotone Basin (South Italy)
No full textThe Crotone Basin, located on a stack of nappes piled up during
the late Paleogene-Neogene, formed in the late Neogene to Quaternary
as a forearc basin of the Ionian arc-trench system. The process of slab
rollback caused rapid trench migration, resulting in an extensional-transtensional
regime persisting most of the time in the forearc area.
The late Neogene tectonic evolution was strongly influenced by a NW-directed fault system, interpreted as basement wrench faults
leading to partitioning of the basin into separate sub-basins subject
to differential subsidence and mutual displacements. Major
sequences identified in the area are regarded as tectono-stratigraphic
sequences (TSS). The first of them was laid down in the late
Serravallian (?) – Tortonian – early Messinian, during the basin
opening stage and is bounded at the top by an erosional unconformity,
which may be correlated with the well-known intra-Messinian
event of the Mediterranean Salinity Crisis. The second TSS, of middle
to late Messinian age, is characterized by strongly syntectonic
deposits mostly derived from cannibalization of the lower Messinian
succession, first infilling extensional troughs, then involved in an
episode of sinistral transpression along the NW-trending fault system,
which generated local overthrusts, sealed by a late Messinian
erosional unconformity. The Messinian tectonics probably reflects
the interplay between the processes linked to the kinematics of the
Calabria block and those triggered by the Salinity Crisis. The erosional
unconformity is overlain by widespread coarse fluvial conglomerates,
which are the first onlapping term of the third TSS, represented
by uppermost Messinian to lower Zanclean deposits, laid
down in an extensional-transtensional regime. This TSS was closed
by an important late Zanclean episode of dextral transpression along
the NW-trending fault system, leading to inversion of the former
basins, and limited SW-verging thrusts on fault-restraining bends.
The unconformity sealing the structures has a clear expression in the
northern, marginal part of the Crotone Basin and correlates downbasin
with a conformable surface. The fourth TSS is characterized
by a long-lasting phase dominated by extension-transtension, leading
to high subsidence rate during the latest Zanclean to Early Plei -
stocene, and accommodating a thick succession of slope mudstones
including clusters of diatomaceous bands mostly in the D. tamalis
and D. brouweri Zones. In the northern part of the Crotone Basin
two phases of drowning separated by an uplift pulse at ca. 2.55 Ma
can be recognized, the second of which was a dramatic collapse,
between 2.3 and 2.1 Ma. The fifth TSS is bounded at the base by an
unconformity at the transition between «large» and «small» Gephyrocapsa
Zones, i.e. at around 1.1-1.2 Ma, correlating basinwards
with a conformable surface. The unconformity is erosional and
locally angular in the marginal part of the basin, where it seals structures
generated by a contractional event documented also elsewhere
in the Calabria block. This event, which is accompanied by a strikeslip
component, is inferred to be coeval to the Lower Pleistocene
important transpressional episode along the Pollino shear system,
which led to release of the Calabria block from the southern Apennines.
The fifth TSS is characterized by resumed dextral transtension
in the Middle Pleistocene along right-stepping NW-trending
faults. This episode generated minor pull-apart sub-basins, showing
spectacular growth structures in their infilling successions, which
developed with shoaling trend up to inferred Marine Isotope Stages
9-8. The onset of shoaling trend was diachronous, being remarkably
younger in the southern sub-basin. In the late Middle Pleistocene to
Recent times extensional tectonics was dominating, accompanied by
local gravity gliding towards the Ionian Sea, arguably triggered by
increase in topographic gradient following hinterland uplift, and
implying the activation of a linked, thin-skinned extensional and
contractional NE- to NNE-directed fault system, with detachment
surface possibly soling into Messinian evaporitic-mudstone deposits.
It is concluded that the geologic evolution of the investigated forearc
area was characterized by an alternation of long-lived stages of
extension-transtension expressed by prolonged subsidence preceded
by uplift pulses, and short-lived episodes of contraction-transpression.
Major drowning episodes in the forearc area are thought to be
coeval to the main phases of spreading in the Tyrrhenian basi
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