1,720,974 research outputs found
Surface uplift and sea level change: constraints from Late Pleistocene paleoshorelines
Full text linkThe aims of this PhD research project are both a reconstruction of the surface
uplift of the Tyrrhenian coastal side of the southern Apennines in the Middle-Late
Pleistocene time span and a field data acquisition on Relative Sea Level (RSL)
indicators in order to better constrain the sea level change for the western sector of
the Mediterranean. The field study has been based on detail scale morphotectonic
and stratigraphic analyses, which have been carried out by geomorphological
analyses on topographic maps and Digital Elevation Models (DEM), on two key
areas of the Tyrrhenian coast: the Campania Plain margin and the Basilicatanorthern
Calabria area. The morphostratigraphical analyses have been integrated
by new U-series dating of calcite deposits (speleothems and a calcite vein) and
coral C. caespitosa samples. The main topics and results can be summarised as
follows:
A study of formerly known and new outcrops of marine terraces has
been carried out in the NE margin of the Campania Plain (Fellino
Mt.), a Quaternary coastal graben located in the Tyrrhenian side of
the southern Apennines;
• Raised paleoshorelines assigned to two raised paleoshorelines
(labelled T1 and T2) were detected along Fellino Mt. at variable
elevation;
• The synchronous correlation method, based on U-series dating on a
calcite vein post-dating the age of T2 terrace, allow relating the T2
and T1 identified paleoshoreline to MIS 9 and MIS 7 respectively;
• Structural data collection allow defining the geometry and kinematics
of the main Quaternary structures filling, hence, the existing gap
along the borders of the Campania plain. The study reports the first
field evidence of Quaternary extensional tectonics affecting the Campania Plain borders. The identified paleoshorelines are displaced
by a major extensional fault zone c. E-W oriented (namely Polvica
Fault), and several faults c. N-S and NW-SE oriented with less
displacements;
• The uplift fault-related rate of the Polvica Fault, the throw rate and
the Earthquake Recurrence Interval (ERI) have been estimated in c.
02-06 mm/y range, 0.4 mm/y and c. 1100 y respectively. The uplift
rate is characterised by a spatially variation along the strike of the
Polvica Fault;
A flight of paleoshorelines up to c. 60 m a.s.l. located along the
Tyrrhenian sector of the Basilicata - northern Calabria has been
investigated by detailed geomorphological-stratigraphical analyses.
The flight of paleoshorelines has been constrained in the early 1990s
with AAR and U-series dating but the new U-series dating provided
in this study has allowed the reconstruction of a chronological
framework for the analysed sea level markers. The U- series dating
have been performed on C. caespitosa corals and calcite concretions,
either predating or postdating the paleoshorelines. In particular, the
U-series dating allow correlating the T1 terrace at 5 m a.s.l. to the
MIS 6e, the T2 at c. 16 m to MIS 5c, the T3 terrace at c 22 m a.s.l. to
MIS 5a, the T4 terrace at 35 m .s.l. to the MIS 5e and the higher T5
terrace to MIS 7. The new findings shed light on the Quaternary
evolution of the Basilicata area – northern Calabria;
• A Relative sea level (RSL) curve during the Middle-Late Pleistocene
time span for the northern Calabria-Basilicata Tyrrhenian sector has
been constructed;
A mean uplift rate of 0.235 ± 0.01 mm/y since the Last Interglacial
has been evaluated. The uplift rate is one order of magnitude larger
than estimation based on former dating;
• The new data provide new constraints to both the long term evolution
of the Tyrrhenian margin of the southern Apennines and the late
Quaternary sea level fluctuations in the western Mediterranean. The
elevation of MIS 5a, 5c and 6e peaks and the time span of 5a have
been evaluated. Such elevations may better constrain ice sheets
volume variation during the late Quaternary.
• The geomorphological reconstruction has demonstrated that a mere
sequential correlation may be misleading in the interpretation of
flights of marine terraces, and indicates that multiple age controls are
crucial to unravelling the complex interaction between uplift and sea
level fluctuations in uplifted coastal areas;
A review of MIS 5 paleoshorelines along the western Mediterranean
(Spain, France, Italy, Istria, Kvarner and Dalmatia, Algeria and
Morocco) has been compiled in the framework of the Word Atlas of
Last Interglacial Shorelines (WALIS)
Last Interglacial sea-level proxies in the western Mediterranean
Full text linkWe describe a database of Last Interglacial (Marine Isotopic Stage 5) sea-level proxies for the western Mediterranean region. The database was compiled reviewing the information reported in 199 published studies and contains 396 sea-level data points (sea-level index points and marine- or terrestrial-limiting points) and 401 associated dated samples. The database follows the standardized WALIS template and is available as Cerrone et al. (2021b, 10.5281/zenodo.5341661)
Integrated geomorphological and structural analysis of coastal cliffs: The case study of Capo Faro Promontory, NE Salina, Aeolian Islands, Italy
No full textThe captivating Capo Faro Estate, nestled on a flat terrain just beyond the steep edge of a coastal cliff, stands out as a prestigious vineyard and residential area in Capo Faro Promontory at Salina (Aeolian Islands, southern Italy). A thorough investigation of the promontory's geomorphological features has been carried out. To enhance the understanding of potential hazards affecting the area, field activities have been supplemented by remote sensing analysis involving both nadir and off-nadir unmanned aerial vehicle flights. Notably, the coastal cliff has been found to undergo rapid retreat, leading to landslides. Consequently, a detailed field survey was conducted to examine the stratigraphy and structure of the cliff area. By employing a high-resolution Digital Elevation Model, detailed bathymetric-topographic profiles were derived along the coastal stretch adjacent to the cliff, enabling an assessment of the thickness of volcanic deposits and the development of a geological model. Moreover, the stability of the rock wall has been evaluated by characterizing the primary discontinuities within the rock mass and analyzing their structural implications. The obtained results underscore the fundamental role of such research in facilitating the formulation of effective risk mitigation measures
Sea-level oscillations within the last interglacial: Insights from coral reef stratigraphic forward modelling
Full text linkUnderstanding past sea-level variations is essential to constrain future patterns of sea-level rise in response to warmer climate conditions. Due to good preservation and the possibility to use various geochemical methods to date fossil sea-level index points, the Last Interglacial (Marine Isotope Stage, MIS, 5e, 130–116 ka) is often regarded as one of the best climate analogs for a future warmer climate. MIS 5e coastal stratigraphic sequences, such as fossil coral reefs, are characterized by abrupt shifts in their geological facies, steps within the reef topography or backstepped morphologies, which have been often interpreted as proxies for abrupt sea-level fluctuations within the interglacial. However, the observational evidence and magnitude of such abrupt changes are controversial. Here, we run nearly 50 thousand simulations of a 2D kinematic reef model that can reproduce coral reef growth and demise through time. Our aim is to investigate the parameters of space, the sea-level scenarios, and the processes which multiple-stepped MIS 5e fossil reefs form. As inputs to the model, we use both published and synthetic sea-level histories (17 sea-level curves, with different sea-level oscillation patterns), and a wide range of reef growth and marine erosion rates, and bedrock foundation slopes. Our results show that the only sea-level history that could explain the generation of an emerged MIS 5e backstepped reef is a first sea-level peak followed by an abrupt rise in sea level and a second short-term peak. Any other multiple-stepped stratigraphy can be explained by the interplay between reef growth, marine erosion, and bedrock slope
Last Interglacial sea-level proxies in the western Mediterranean
Full text linkWe describe a database of Last Interglacial (Marine Isotopic Stage 5) sea-level proxies for the western Mediterranean region. The database was compiled reviewing the information reported in 199 published studies and contains 396 sea-level data points (sea-level index points and marine- or terrestrial-limiting points) and 401 associated dated samples. The database follows the standardized WALIS template and is available as Cerrone et al. (2021b, https://doi.org/10.5281/zenodo.5341661)
Fluvial responses to Holocene climatically induced coastline migration in the Iguape River estuary (Southeast Brazil)
No full textRivers represent intricate geomorphological systems that exhibit sensitivity to even
subtle base-level changes. This study examines the geomorphological response of
Ribeira de Iguape River, located along the southern coast of S ̃ao Paulo state, Brazil,
to hydrological changes and coastline migration resulting from Holocene climate
pulses. Using a multidisciplinary approach, including geomorphological and stratigraphical
analyses, optically stimulated luminescence dating, grain-size analyses,
interpretation of satellite images, mapping and reassessment of previous studies, we
investigated the potential impacts of these geomorphological dynamics on the river
system. Our study reveals two distinct orders of low fluvial terraces, typically
inserted no more than 10 m above the average channel discharge, which are geochronologically
correlated with the low marine terraces that document the former
coastline position at the river mouth, as previously identified in other studies. Such
findings indicate a deposition phase when the coastline was stabilised on the inner
continent in the Medieval Warm Period, as well as an erosion phase when the coastline
migrated seaward during the Little Ice Age. This research contributes to improving
our understanding of how rivers can respond to base-level changes and provides
valuable insights into the dynamic interactions between river systems and coastal
environments
Spatio-temporal reconstruction of the post-glacial sea-level evolution in the Ross Sea, Antarctica
Full text linkThe complex interactions between the redistribution of water mass in the ocean basins due to continental ice sheet growth and decay, and the attendant Glacio-Isostatic Adjustment (GIA) process play a major role in controlling Relative Sea-Level (RSL) variability since the Last Glacial Maximum (LGM). In near-field regions (e.g., areas covered by the major ice-sheet at the LGM), the rate of GIA uplift during deglaciation often exceeded the rate of RSL rise from an increase in ocean volume due to the melting of land-based ice.
Here, we assembled a database of new and previously published RSL collected along the coasts of the Ross Sea (Antarctica). The set of 14C radiocarbon dates was obtained from samples of Adelie penguin guano remains and shells found on raised beaches and collected during several Antarctic expeditions conducted in the framework of the Italian Programme of Antarctic Researches (PNRA). We further revisited about 300 radiocarbon dates available in literature following the standards of the latest International Geoscience Programme (IGCP) protocols on sea-level studies. All these dates were also recalibrated according to the latest calibration curve
We thus produce a new set of 65 RSL data points which have been classified in i) Sea Level Index Points (SLIP), when the relationship between the sample and the tidal level is clearly known (e.g., raised beaches), ii) marine and iii) terrestrial limiting points which indicate the upper and the lower threshold for the former sea-level position, respectively.
In order to reconstruct the RSL trend in the last thousands of years, a critical interpretation of the dated materials has been carried out. For example, data show that the penguin guano and remains from ornithogenic soil on top of beaches and on abrasion platforms significantly rejuvenated the age actual age of the beach ridges.
We finally applied on the new dataset a spatio-temporal empirical model to reconstruct magnitudes and rates of RSL change (with associated uncertainty) from SLIPs along the Ross Sea area. The model output shows a continuous RSL drop of about 25 m last ~7 ka BP. This drop was generally characterized by average rates comprised between ~2 to ~4 mm/y. An episodic increase of the RSL falling rates, up to ~6 mm/y was found at ~4 ka BP, likely related to a local increase of the GIA contribution
This study, based on a robust number of radiocarbon dated coastal deposits, will allow to better define the recent Antarctic ice-sheet fluctuation and to contribute in the tuning of the GIA models in this key sector of the World’s coastlines
Reoccupation of late Quaternary relative sea level indicators in a tectonically quasi-stable coastal area in Southern Italy (Cilento headland): Insights into the Last Interglacial stillstands
Full text linkA geomorphological-stratigraphical study, integrated with a modelling approach, has been employed to constrain the age of relative sea-level indicators (RSLi) along the quasi-stable Mt. Bulgheria coast in the southern Apennines, located on the eastern margin of the Tyrrhenian Sea. Focusing on the geological evidence of late Quaternary sea-level fluctuations within the 0 to 12 m above sea level (a.s.l.) elevation range, we describe RSLi along ca. 8 km of coastline and constrain their elevation, including those of previously undated RSLi in the same area. The reassessment of field data was needed to address the phenomenon of the reoccupation of older RSLi by younger ones. The approach employs the synchronous correlation method, integrating highstand peak elevations
from global sea-level curves and a calibrated uplift rate value, derived from the correlation of RSLi-2 (currently at 8 ± 1 m a.s.l.) with Marine Isotope Stage (MIS) 9c, as suggested by recent findings.
Overall, four RSLi are identified in the investigated coastal zone: RSLi-1 (11 ± 1 m a.s.l.), correlated with MIS 11; RSLi-2 (8 ± 1 m a.s.l.), correlated with MIS 9c and reoccupied during the first MIS 5e peak; RSLi-3 (4 ± 0.5 m a.s.l.) formed during an earlier, undefined stage and reoccupied during MIS 5e; RSLi-4 (2.5 ± 0.5 m a.s.l.) also assigned to MIS 5e. Notably, two cases of reoccupation of older RSLi by younger ones are here reported.
By testing multiple global sea-level curves, we derived a range of possible uplift rates for the chronologically constrained RSLi-2. Consequently, assuming a constant uplift rate throughout the final part of the Middle Pleistocene, we sought the optimal match between all observed RSLi and predicted elevation of palaeo sea levels during past highstands.
The preferred best fit was obtained using a composite eustatic curve from Waelbroeck et al. (2002) and Kopp et al. (2013, for within the MIS5e), and a constant uplift rate of 0.009 mm/yr. Our modelling of MIS 5e (Last Interglacial) identifies three sea-level stillstands and a rapid drop in sea level following the first and higheststillstand. Our results emphasize the importance of the reoccupation problem in sea-level reconstruction studies, especially for RSLi located in regions that are tectonically stable or with relatively low rates of crustal vertical movements. In such contexts, the sea level during younger interglacials may reach or exceed the elevations of older interglacials, reusing or modifying existing RSLi and complicating the identification of which sea-level stand created a specific shoreline feature. The calibrated model supports scenarios where MIS 5e, MIS 9c and MIS 11 had higher peaks than the Holocene (so far). Finally, this work challenges the assumption that RSL indicators ranging between 5 and 8 m a.s.l. in stable regions were exclusively formed during MIS 5e, emphasising
the need for precise age constraints in these interpretations
Late Quaternary uplift and sea level fluctuations along the Tyrrhenian margin of Basilicata - northern Calabria (southern Italy): New constraints from raised paleoshorelines
No full textNew analyses of marine terraces in the Tyrrhenian Sea margin of Basilicata - northern Calabria (southern Italy) have been carried out. In the study area, c. 25 km in length, an impressive flight of marine terraces occurs, with the highest terraces reaching ~160 m a.s.l. Detailed geomorphological-stratigraphical analyses on remnants of paleoshorelines located within 60 m a.s.l. have shown that the rocky coast of the investigated coastal stretch has been affected by multiple relative sea-level fluctuations, during which reworking of older shorelines has occurred. Dating of the coral Cladocora caespitosa and speleothems, either predating or postdating single paleoshorelines, has allowed the construction of a chronological framework for the identified relative sea-level markers, and their correlation with MIS 7, MIS 6e and distinct peaks of MIS 5. A mean uplift rate of c. 0.25 mm/y since the Last Interglacial has been quantified, one order of magnitude larger than previous estimates. The uplift rate value has been used to infer the elevations of MIS 5a, 5c and 6e sea level peaks, which are higher than those reported in most sea level curves worldwide, although consistent with several findings from the western Mediterranean. Our results demonstrate that a mere sequential correlation may be misleading in the interpretation of flights of marine terraces and indicates that multiple age controls are crucial to unravelling the complex interaction between uplift and sea-level fluctuations in uplifted coastal areas. The reconstructed MIS 5a, 5c and 6e sea level paleo-elevations, besides contributing to the assessment of late Quaternary sea-level fluctuations in the Mediterranean Sea, may contribute to constrain coeval ice sheets volume variations
- …
