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Late Quaternary incised and infilled landforms in the shelf of the northern Adriatic Sea (Italy)
No full textThe northern Adriatic shelf is punctuated by the presence of several incised and filled features that have been
revealed by the offshore seismic and stratigraphic surveys carried out in the last decades. In this study we
analyzed an area located in the northern Adriatic shelf, 30 km offshore of the Venice Lagoon and between 29 and
34m below the mean sea level, where the most impressive examples were identified. By integrating the interpretation
of about 3000 km of high-resolution seismic profiles (CHIRP) with sediment cores, paleontological
analyses and radiocarbon dates, it was possible to distinguish between two generations of incised features. The
older generation (Nadia) is represented by a fluvial incised valley that reaches a depth of up to 30m and was
formed and infilled during the LGM marine lowstand, probably between ca. 26 and 24 ka cal BP. The peculiar
horizontal layering displayed by the infilling is characteristic of a low-energy environment. This suggest that,
after its formation, the valley was first occupied by a swampy environment, which was then gradually filled-up
with sediments received from nearby riverine systems. Differently, the younger generation (Attila) consists of a
set of tidal inlets and channels with a maximum depth of 20 m, which are the legacy of a transgressive lagoon
environment. The tidal nature of these features is confirmed by the geometry and paleontological content of
their infilling and by their overall morphological and morphometric characteristics. The transgressive lagoon
where these channels developed probably existed for just few centuries in the Early Holocene (ca.
10–9 ka cal BP). This period likely coincides with a temporary deceleration or stasis of the sea-level rise rate. This
work presents new results for the paleogeographic and paleoenvironmental reconstruction of the northern
Adriatic area, covering a period that spans from the middle LGM to the beginning of the Holocene
Vertically stacked Gilbert-type deltas of Ventimiglia (NW Italy): The Pliocene record of an overfilled Messinian incised valley
No full textOverfilled incised valleys develop when the rate of sediment supply outpaces the rate of accommodation. An overfilled incised valley presents simple or compound valley-fill architecture, depending on the depth of the valley incision, compared with the height reached by the following sea-level rise.
The Ventimiglia incised valley, exposed on the Ligurian coast, north-western Mediterranean margin, presents a spectacular example of compound incised-valley fill, developed in perennial “overfill” conditions. The valley was subaerially incised during the Messinian Salinity Crisis and rapidly flooded by the sea at the beginning of Pliocene, then filled by eleven coarse-grained Gilbert-type deltas during Early–Middle Pliocene time.
The basal Messinian unconformity is locally paved with subaerial scree breccias and bioclastic shallowmarine sandstones, and blanketed by bathyal marls. These deposits record the lowstand, transgressive and early-highstand systems tracts of the first valley-fill sequence. The subsequent progradation of Gilbert-type deltas occurred in four stages, or depositional sequences, separated by transgressive marine-marl intervals.
Within each depositional sequence, the deltaic bodies display offlapping architecture, recording falling shoreline trajectory, downward shifts in facies, and overall forced regression. The water depth and accommodation in the inundated coastal valley was gradually decreasing with time. The reduced accommodation allowed the youngest deltas to prograde out to the shelf edge, triggering mass collapses and subsequent filling into the newly created slump scars. Some of the deltas probably acted as “canyon perched deltas” and supplied sediment to the deep-water slope and floor of the Ligurian Basin.
The vertical stacking of Gilbert-type deltas is usually attributed, in tectonically active basins, to fault-related subsidence pulses. In Ventimiglia, the accommodation was created by high-frequency eustatic sea-level rises that, probably accompanied by climate controlled reductions in sediment supply, temporarily outpaced uplift, leading to the development of multiple cycles of infill
Climatic patterns revealed by pollen and oxygen isotope records across the Brunhes-Matuyama boundary in Central Mediterranean (Southern Italy)
No full textUltra high-resolution marine record of paleoenvironmental changes in the last 5000 years
No full textReading natural subsidence of Venice during the latest 40 MY from the sedimentary record.
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Preboreal climatic oscillations recorded by pollen and foraminifera in the Southern Adriatic Sea
No full textCore SA03-1 from the southern Adriatic Sea (EC-Eurostrataform project) provides new information about climate changes and palaeocirculation in the Adriatic region during the last deglaciation. The results of an integrated study based on pollen and foraminifera records of the part of the core spanning the late Pleistocene–early Holocene transition (including the late Younger Dryas, the Preboreal and the beginning of the Boreal) are presented. The major vegetation changes and the short-term oscillations occurred during the early Holocene warming in the southern Adriatic basin on the basis of a high-resolution pollen record are documented. Vegetation changes are correlated to short-term oscillations detected in the foraminifera record during the same interval. The two independent terrestrial and marine proxies indicate at least three short-term cold and dry oscillations occurring at 11.2–11, 10.8–10.4 and 10 cal ka BP, according to the age–depth model adopted in this study. Finally, adopting an event-stratigraphy approach, the comparison of these results with two western Mediterranean records of Preboreal short-term oscillations suggest the occurrence of synchronous bio-events in the Mediterranean basin
Holocene salt marsh plant communities in the North Adriatic coastal plain (Italy) as reflected by pollen, NPP and plant macrofossil analyses
No full textIn this work we investigate the development of a
salt marsh environment during the Holocene marine transgression in the North Adriatic coast (North Italy) near the pre-Roman and Roman towns of Cittanova and Concordia Sagittaria. Pollen, plant macrofossils, non-pollen palynomorphs
(NPPs) and foraminifers are analysed in cores and archaeological excavations to indicate the development of salt marsh plant communities. Other independent proxies (foraminifers, plant macrofossils, molluscs) confirm the ecological interpretation based on pollen records. The relevance of NPPs as indicators of salt marsh environment is evaluated. Linings of foraminifers are the most frequent NPP type, recorded in 85% of the brackish sediments. They may tentatively be referred to the genus Ammonia, a very common benthonic genus in the present lagoons of the North Adriatic Sea. Radiocarbon dates available from previous work allow the salt marsh development to be dated in the sector from the east of the Lagoon of Venice to the Lagoon of Caorle. Near Cittanova, salt marshes developed before 6700 yrs cal. B.P. At Concordia Sagittaria, the first evidence dates from ca. 6700 yrs cal. B.P. and a phase of freshwater conditions is recorded in the sediments of ca. 4500 yrs cal. B.P
Subsidence pattern in the central Adriatic and its influence on sediment architecture during the last 400 kyr
No full textThe western Adriatic margin (eastern Mediterranean), part of the Apennine foreland, is characterized by a differentiated tectonic setting, showing high subsidence rates (up to 1 mm/yr) in the northern area and tectonic uplift (on the order of 0.3–0.5 mm/yr) in the southern part corresponding with the so‐called Apulia swell. The central Adriatic marks the transition between these two areas. To calculate subsidence values, the stratigraphy of the central Adriatic has been investigated through the borehole PRAD1.2 (European project Profiles across Mediterranean Sedimentary Systems), the first continuous Quaternary marine record in the Adriatic basin (71.2 m long) reaching the top of Marine Isotope Stage 11 (MIS 11). Subsidence calculations were performed first by applying the backstripping procedure to PRAD1.2, in order to investigate the contribution of sediment load and tectonic driving forces to subsidence. Despite the large error bars, mostly caused by the uncertainties in paleowater depth reconstructions, the values obtained demonstrate that tectonics is the main driver for subsidence in this area. In order to better estimate the subsidence rates, an independent approach is introduced, based on the correlation of the present‐day burial depth of past shorelines deposited during the main glacial lowstands, from MIS 2 to MIS 10. The average subsidence rate of about 0.3 mm/yr appears greater than the average sediment supply rate (0.15 mm/yr), and this fact explains the overall backstepping of the 100 kyr regressive depositional sequences on the margin. The results obtained help to improve the understanding of the regional tectonics and can be used for quantitative reconstruction of Quaternary sea level changes in the Adriatic region. In general, the paper shows that even a short (71 m) borehole across a relatively short time span (340 kyr) can be useful for subsidence calculations, provided that a high‐resolution definition of its stratigraphy is available and a correlation can be drawn with the geomorphologic proxies such as paleoshoreline deposits
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