The Middle Pleistocene–Holocene Sardinian stratigraphy has been revised to identify the roles played by sea and climate changes in controlling sedimentation. The succession, dated through Optically ...Stimulated Luminescence (quartz, K-feldspar) and 14C (the most recent) was grouped into eight major stratigraphic units mainly represented by coastal dunes, shallow marine, and alluvial systems. These units range in age from MIS 8 (300 ka) to MIS1 (6 ka).
Little information is available for the period between MIS 8 and 6. The available data, however, allow some comments on climate changes over the last 125 ka. The last interglacial (MIS 5) is subdivided into five substages (e–a). MIS5e (Eemian) is considered the climate optimum of this interglacial, sea level was 4–6 m higher than today, and climate conditions were warmer and more humid. MIS 5c is the second high stand peak. Sea level was about 1.5 m above the modern level, and paleoclimatic and paleogeographic conditions were similar to the present. During MIS 4, at the beginning of the glacial phase, a climatic deterioration occurred. Temperatures dropped by 6C° relative to MIS 5e in about 5 ka, and sea level fell about 60 m. This led to a progressive disruption of inland vegetation cover and to repeated valley slope denudation. The sea-level fall created the accommodation space for fan development in sheltered and cliffed areas, where debris flows developed and filled almost completely the terminal parts of the narrow coastal valleys/coves. In wider areas, however, coastal dune fields developed. Contemporaneous presence of alluvial fan and dune systems is associated with the local morphology that could mitigate or amplify moist conditions within a generally arid environment.
During MIS 3, several climate fluctuations occurred (wet/arid, D/O-H events). However, the shallow Sardinian shelf was continuously sufficiently exposed to become the source area of bioclastic sands. These sands were blown inland, and formed extensive dunefield systems. Dunes dominated the west coasts of Sardinia under cold and relatively dry conditions. In some areas, these dunefield systems were eventually almost completely dismantled and reworked into water-flow dominated alluvial fans by catastrophic rainfall events. Thus, the local climate quickly switched from arid to humid conditions. No record of the last Glacial Maximum deposits, MIS 2, was observed along the NW Sardinian coast. During the Holocene transgression (MIS1) coastal dune systems developed and progressively migrated inland, and temperature rose to reach the present-day condition.
This study was conducted in the Middle Branch of Bue Marino Cave (Sardinia, Italy) to reconstruct paleoecological conditions during the Holocene through microfaunal proxies in seven surface sediment ...samples and a short sediment core (BMD-2018, 18 cm), all collected in 2018 and another core sampled in 2021 (BMD-2021, 28 cm). The first attempt at dating cave sediment through luminescence was conducted on BMD-2021; the derived age was 6.04 ± 0.47 ka at 18 cm depth. Although continuous sedimentation and constant rates are not probable in the cave, this indicates that the sedimentary record dates to the early times after the Holocene flooding of the cave by the sea. Benthic foraminifera and grain size were analyzed in all surface samples and core BMD-2018, while only benthic foraminifera were studied in BMD-2021. The recent foraminiferal assemblages, studied from an ecological point of view, were applied as modern analog to reconstruct the paleoecological conditions in sediment cores. Significant changes in the sedimentary environment were excluded; the two cores showed a similar foraminiferal turnover at a similar depth, from an older assemblage with prevailing indifferent Ammonia inflata to a younger one with prevailing opportunist Eggerelloides advena. This turnover was attributed to changes in the amount and/or quality of available nutrients. Based on these results, this event is likely related to possibly attributable to the effects of climate changes that occurred in the Holocene. However, more extensive studies are necessary to better understand the effects of the climatic/environmental events in the Late-Holocene in the caves. Although it represents a first attempt at paleoenvironmental reconstruction based on sediments from a Mediterranean marine cave, this study demonstrated that benthic foraminifera are refined paleoenvironmental proxies and that the integrated approach with the luminescence dating produces reliable results for studying the effects of global changes in these environments.
The study area is located in NW Sardinia Island (Italy), Mediterranean Sea. Sardinia is considered stable since the late Pliocene with a negligible subsidence of about 0.01 mm/y. It is therefore ...normally used to reconstruct the Pleistocene and Holocene sea level curves. Our research focusses on the sea-facing city of Alghero that from 1353 to 1720 was under the Spanish government. During this time, the city was renovated and new buildings edified. Dimension stones were quarried all around Alghero both in the nearby inland and along the coast. Coastal quarries were considered the most suitable for both rock quality and the easiest way to transport the quarried material by boat. The quarried rocks are late Pleistocene dune and beach sandstones deposited from the 132 ka (Marine Isotopic Stage—MIS5) to about 65 ka (MIS4). Sandstones crop out from few cm to 3 m above the present sea level and underwent several consolidation processes related to loading and marine weathering. This latter favoured dissolution and circulation of calcium carbonate which cemented the rocks. It is reported that the Spanish were looking for these “marine” sandstones for their high geotechnical characteristics. Different rules were adopted through time for the size of the dimension stones and this has allowed us to establish a quarry exploitation chronology. For example, “40 × 60 × 20” cm was the size of the dimension stones used for the Alghero Cathedral dated at 1505–1593. Nowadays most of the coastal Spanish quarry floors are 30 centimetres below mean sea level (tidal range is 30 cm). Accordingly, we infer that relative sea level from 1830 AD (and of the Little Ice Age) rose in about 200 years to the present level at the rate of about 1.4 mm/y. Considering that relative sea level rise during the Medieval warm period was of 0.6 mm/y over a period of about 400 years, we may deduce that human influence was strong enough to lead to a relative sea-level rise faster and in shorter time.
Purpose
Loess in Northern Italy has been usually considered deposited during the MIS 4-2 period, which corresponds to the last Pleistocene glacial cycle. In particular, no absolute dating evidenced ...loess depositions older than ca. 89 ka. We investigated two strongly rubified soil profiles in the southern margin of the Alpine range in Lombardy to prove their aeolian origin and age of formation.
Methods
We analysed the granulometry of all genetic horizons of these strongly rubified soils, and a total of 8 samples were collected for luminescence dating purpose.
Results
Most of the analysed soil horizons were dominated by silt and were characterized by the s-shaped granulometric curve, typical of loess materials. A particularly high clay content evidenced a strong weathering degree. A deep horizon was particularly clay rich, and it was interpreted as a typical Terra-Rossa horizon. Luminescence dates increased with depth, reaching 122 ka for the deepest loess layer and 453 ka (minimum age) for the Terra-Rossa horizon.
Conclusions
The deepest observed loess layer represents the oldest quantitatively dated aeolian deposition in Northern Italy up to now.
The shallow-marine to coastal deposits of Alghero have been dated using the Optically Stimulated Luminescence (OSL) method, and studied to define the palaeoenvironmental evolution of coastal areas in ...northwest Sardinia. Dating, coupled with sedimentological and stratigraphical analyses, allowed the subdivision of the succession in four unconformity-bounded units (U2, U3a, U3b, U4). Unit U2 of penultimate glacial stage (MIS 6; ca. 150
ka) is composed of dune deposits formed intermittently along rocky coastal areas under strong wind conditions. Subunit U3a is composed of cliff-bounded gravelly dominated pocket beach deposits, commonly highly fossiliferous, and is assigned to the interglacial MIS 5e (ca. 125
ka). Subunit U3b is characterized by sandy beach to coastal systems of the isotopic sub-stage MIS 5c (ca. 100
ka). The unconformity between U3b and U4 marks the initiation of last glacial regression (MIS 5a/4; ca. 77
ka) during which shelf areas were exposed and small incised valleys developed. Along the valley flanks, colluvial or sheetflood sediments were deposited and, in the central part thick reddish paleosols formed. Valleys were eventually filled by thick aeolian dune deposits (MIS 4–3) indicating persistent inland sand transport. Around Alghero, coastal carbonate-rich dunes preferentially formed and migrated inland during lowstand and falling stages when the climate is relatively cold, vegetation is quite open, winds are fairly strong and sediment supply from exposed shelf areas is high.
The Alghero Bay is a coastal area of high economic value because of the presence of one of the most popular beaches of Sardinia (San Giovanni, Maria Pia, Le Bombarde, Lazzaretto). The organisms ...living in the meadow of Posidonia oceanica, which densely cover the offshore areas of the bay, represent the most important source of sediments to these beaches. For this reason, a detailed mapping of the local seabed features and distribution of P. oceanica constitutes an important tool for the coastal managing of the area. The integrated use of several methodologies, such as Side Scan Sonar, Remote Operating Vehicle, Drone and direct sediment sampling has allowed us to realize a very detailed seafloor map of the Alghero Bay.
The relict beach deposit of the Cala Mosca marine terrace is considered an important section of Marine Isotopic Stage (MIS) 5e (ca. 125 ka) sea-level highstands. Analysis of the stratigraphy and ...sediments of the deposit indicates the presence of a composite marine terrace comprising two superimposed marine units, luminescence dated to the MIS 5e (137 ± 7, 134 ± 7 ka) and MIS 5c (92 ± 6 ka) substages. The stratigraphic superimposition of the two highstands, both placed ~5 m above present sea level, agrees with other areas along the Sardinia coasts. The evident superimposition of two sea-level highstands and development of the composite terrace cannot be accounted solely by high-frequency sea-level oscillation that occurred within MIS 5 for the Mediterranean Sea. This suggests controversial, but significant, regional versus local tectonic activity occurred during the Late Pleistocene.
Intertidal coralline red algal build-ups (Lithophyllum byssoides rims or ridges) are considered precise sea level markers and mostly used for Holocene sea level history. Several well-preserved ...patches of relict red algal ridges crop out along the north-west Sardinian coast (Mediterranean Sea, Italy) and have great potential in reconstructing the late Pleistocene sea level history of the western Mediterranean. The aim of this paper is to determine the sedimentary characteristics of the relict Lithophyllum byssoides build-ups cropping out along the Sardinian NW coast and to demonstrate how these can be used as past sea-level indicators. To establish a chronological framework for these deposits, luminescence dating (both quartz OSL and K-feldspar pIRIR290) has been applied and allows for the Lithophyllum byssoides ridge formation to be assigned to Marine Isotopic Stage (MIS) 5e (132–112 ka). The studied relict ridges confirmed that MIS 5e sea-level was at least at 4 m above present, well matching the widely accepted last interglacial global sea-level curves. Hence, fossil Lithophyllum byssoides ridges can be used as stratigraphic and chronologic indicators of late Pleistocene sea-level. Moreover, the study has underlined that Lithophyllum byssoides may grow: (1) in sheltered places along high cliffy coasts forming bench-like structures, and (2) in high-energy environments on wave cut platforms around fallen blocks or potholes, first as isolated mounds and then merging to form reef-like structures.
•Sedimentary characteristics of the relict Lithophyllum byssoides build-ups cropping out along the Sardinian NW coast•Use of Lithophyllum byssoides build-ups as past sea-level indicators•Dating of the relict Lithophyllum byssoides ridge using luminescence (both quartz OSL and K-feldspar pIRIR290)•Fossil Lithophyllum byssoides ridges can be used as stratigraphic and chronologic indicators of late Pleistocene sea level.
Mapping and luminescence aging of raised marine terraces and aeolian ridges along an ∼90 km coastal stretch in southwestern Sicily provide the first quantitative assessment of vertical tectonic ...deformation in this region, which spans the frontal part of an active thrust belt. We recognized a staircase of eleven terraces and nine related aeolian ridges. The elevation profile of terraces parallel to the coast shows a >90 km long bell-shaped pattern, onto which shorter-wavelength (∼10 km long) undulations are superimposed. Luminescence ages from terraced beach deposits and aeolian sediments constrain the position of paleoshorelines formed during MIS 5e, 7a and 7c, with a maximum uplift rate of ∼0.75 mm/a, and indicate a late Middle-Late Pleistocene (80–400 ka) age for the sequence of terraces. The elevation of Lower Pleistocene morpho-depositional markers points that uplift may have occurred at similar rates at the beginning of the Early Pleistocene, but almost zeroed between ∼1.5 and 0.4 Ma before the recent renewal. The uneven elevation of Middle-Upper Pleistocene paleoshorelines observed moving along the coast documents that uplift embeds both a regional and a local component. The regional, symmetric bell-shaped uplift is related to involvement in the thrust belt of thicker crustal portions of the northern African continental margin. The short-wavelength undulations represent the local component and correspond to actively growing bedrock folds. The present study contributes to unravel the different spatial and temporal scales of deformation processes at a collisional margin.
•We mapped eleven raised terraces and nine aeolian ridges in southwestern Sicily.•Luminescence ages indicate terraces and dunes formed in the last ∼400 ka.•Terraces display a ∼100 km long bell-shaped elevation profile with minor undulations.•Uplift rates up to ∼0.75 mm/a reflect both frontal thrust belt motion and fold growth.•Rapid Earliest and Middle-Late Pleistocene uplift separated by tectonic quiescence.
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