A review of 917 relative sea-level (RSL) data-points has resulted in the first quality-controlled database constraining the Holocene sea-level histories of the western Mediterranean Sea (Spain, ...France, Italy, Slovenia, Croatia, Malta and Tunisia). We reviewed and standardized the geological RSL data-points using a new multi-proxy methodology based on: (1) modern taxa assemblages in Mediterranean lagoons and marshes; (2) beachrock characteristics (cement fabric and chemistry, sedimentary structures); and (3) the modern distribution of Mediterranean fixed biological indicators. These RSL data-points were coupled with the large number of archaeological RSL indicators available for the western Mediterranean. We assessed the spatial variability of RSL histories for 22 regions and compared these with the ICE-5G (VM2) GIA model. In the western Mediterranean, RSL rose continuously for the whole Holocene with a sudden slowdown at ~7.5kaBP and a further deceleration during the last ~4.0kaBP, after which time observed RSL changes are mainly related to variability in isostatic adjustment. The sole exception is southern Tunisia, where data show evidence of a mid-Holocene high-stand compatible with the isostatic impacts of the melting history of the remote Antarctic ice sheet.
Our results indicate that late-Holocene sea-level rise was significantly slower than the current one. First estimates of GIA contribution indicate that, at least in the northwestern sector, it accounts at least for the 25–30% of the ongoing sea-level rise recorded by Mediterranean tidal gauges. Such contribution is less constrained at lower latitudes due to the lower quality of the late Holocene index points. Future applications of spatio-temporal statistical techniques are required to better quantify the gradient of the isostatic contribution and to provide improved context for the assessment of 20th century acceleration of Mediterranean sea-level rise.
Beachrocks represent a significant paleo-environmental proxy because they can record both the vertical and the horizontal evolution of the shoreline. They have often been used to assess Holocene ...shoreline evolution and crustally induced Relative Sea-Level (RSL) changes in the Mediterranean Sea. In this paper, we used submerged beachrocks from Paros and Naxos Islands (Aegean Sea, Greece) to reconstruct the shoreline modification and provide new insights on the RSL evolution in central Cyclades. Paros and Naxos Islands are of great importance in terms of archaeological evidence of coastal occupation. However, the evolution of their coastlines was seldom explored. In this study, we coupled detailed underwater surveys, analysis of aerial photogrammetry, microstratigraphic analysis and luminescence dating to study beachrock outcrops found down to about 6m below the present sea-level. We, then, spatially and chronologically constrained some major palaeogeographical changes of a number of coastal sectors of the two islands. Furthermore, the multiple analyses of beachrocks, sediment coring and archaeological data suggested that RSL rose by at least 3.8m in the last 4.0ka and that RSL variation in the last 2.0ka did not exceed 2m with respect to the present mean sea level.
•Submerged beachrocks of Paros and Naxos Islands (Cyclades) were studied in detail.•Submerged beachrocks in Paros and Naxos Islands reach maximum depth of −6.3m.•Palaeogeographical changes of the coastal zone were assessed through the submerged beachrocks.•Luminescence dating constrains beachrocks age between 1.00±0.16ka and 4.48±0.78ka.•Relative sea level has risen by at least 3.8m in the last 4.0ka.
Evidence of catastrophic mega-block deposition is presented for the Algerian coast from Tipaza to Dellys. The region is prone to large earthquakes, several of which are inferred to be tsunamigenic in ...origin, as attests the 2003 Zemmouri earthquake (Mw 6.8). It is argued here that several former tsunamis have resulted in the detachment of large boulders from the nearshore zone and their deposition inland. The estimated size, weight (volumetric mass) and distance from the shoreline of more than 100 boulders has enabled estimates to be made of the nature of the hydrodynamic waves responsible for their transport. The boulders weigh up to 200 tons and are scattered along ∼
150 km of rocky headlands and pocket beaches, in isolated or grouped elements, from the subtidal to supratidal zones. Boulders covered by biogenic incrustations show morphological features which suggest detached, reversed and reworked pieces. Statistical and hydrodynamic analyses indicate that large boulder transport requires either ∼
30-m-high waves or 5 to 10-m-high waves for catastrophic storm or tsunami events, respectively. Bio-indicators allow us to date two inferred tsunamis as having struck the Algerian coastline between AD 400–600 and ∼
AD 1700.
In Northern Dobrogea, north of the Dunavăţ promontory, the Roman fortress of Halmyris was founded in the late 1st century AD on a Getic settlement dating to the middle of the 1st millennium BC, ...probably associated with a Greek emporium of the Classical and Hellenistic periods. At the time of the foundation of Halmyris, the Danube delta had already prograded several kilometres to the east leading to the progressive retreat of the sea and the formation of a deltaic plain characterised by numerous lakes and river channels. Here, we present the results of a multiproxy study combining sedimentology and palaeoecology to (1) understand the evolution of fluvial landscapes around Halmyris since ca. 8000 years BP and (2) identify the fluvial palaeoenvironments close to the city in Getic/Greek and Roman times, in order to locate and characterise the waterfront and the harbour. Our overriding objective was to improve understanding of human–environment relations in river delta settings. We demonstrate that Halmyris, protected by the Danubian floods due to its location on a palaeo-cliff top, had direct access to the river. A secondary channel of the Saint George, flowing north of the site, has been elucidated between the 7th century BC and the 7th century AD and could have been used as a natural harbour.
Major uplifts of late Quaternary marine terraces are visible along the coastline of the Tell Atlas of Algeria located along the Africa–Eurasia convergent plate boundary. The active tectonics of this ...region is associated with large shallow earthquakes (M
≥
6.5), numerous thrust mechanisms and surface fault-related fold. We conducted a detailed levelling survey of late Pleistocene and Holocene marine notches in the Algiers region that experienced 0.50
m coastal uplift during the 2003 Zemmouri earthquake (Mw 6.8). East of Algiers, Holocene marine indicators show three pre-2003 main notch levels formed in the last 21.9
ka. West of Algiers on the Sahel anticline, the levelling of uplifted marine terraces shows a distinct staircase morphology with successive notches that document the incremental folding uplift during the late Pleistocene and Holocene. The timing of successive uplifts related to past coseismic movements along this coastal region indicates episodic activity during the late Holocene. Modelling of surface deformation in the Zemmouri earthquake area implies a 50-km-long, 20-km-wide, NE–SW trending, SE dipping fault rupture and an average 1.3
m coseismic slip at depth. Further west, the 70-km-long Sahel fold is subdivided in 3 sub-segments and shows ~
0.84–1.2
mm/yr uplift rate in the last 120–140
ka. The homogeneous Holocene uplift of marine terraces and the anticline dimensions imply the possible occurrence of large earthquakes with Mw
≥
7 in the past. The surface deformation and related successive uplifts are modelled to infer the size and characteristics of probable future earthquakes and their seismic hazard implications for the Algiers region.
► We study the Quaternary marine terraces of Algiers region. The uplift rate is ~
1
mm/yr (140
ka) and Mw
≥
7 potential. ► The timing of successive coseismic uplifts along this coastal region indicates episodic activity during late Holocene. ► The surface deformation and successive uplifts are modelled to infer the characteristics of probable future earthquakes.
The Chabahar Strandplain (CHS) stretches along the Chabahar bay at a width of more than 5 km along the northern coast of the Gulf of Oman and SE Iran; an area that has been subjected to tectonic ...uplift as a part of the Makran accretionary prism. The CHS comprises of beach ridges, inter-ridge swales, sand dunes, tidal channels and fluvial deposits. We present the first documentation of the spatial distribution and the internal architecture of the CHS based on topographic surveys, sediment percussive coring, trenching and ground penetrating radar (GPR) transects. Radiocarbon dating on marine shells from foreshore deposits of 8 representative beach ridges yielded ages between 4800 and 270 cal. years BP at respective distances of 4800 to 670 m from the present shoreline. We interpret the boundary between the foreshore (beach) and the foredune deposits as indicator of past sea levels by analogy to present shore processes. This boundary is readily recognizable in sediment profiles from cores and trenches as well as GPR reflectors. Based on the age model and depositional features, we estimate relative sea level fall of up to 15 m over the past 4800 years. Considering that the eustatic sea level changes for this period are negligible for the Makran coast, this relative sea level fall is related to tectonic uplift across the coastal Makran. The elevation of palaeo-shorelines with similar ages decrease from east to west of the CHS, which suggest that alongshore variations in uplift rates are likely related to different movements of coastal fault blocks.
•Spatial distribution and internal architecture of Chabahar strandplain documented•Beach ridges age between 4800 at 5 km and 270 cal. years BP at 670 m from shoreline.•The boundary between beach and foredune deposits is the indicator of past sea level.•Relative sea level has fall up to 15 m in the past 4800 years due to tectonic uplift.
The Danube delta is one of the few large deltas in the world the evolution of which has involved numerous and varied episodes within a complex framework of interactivity between river sediment ...supply, allochthonous sediments supplied by longshore currents, marine dispersing forces, vertical movements (neotectonics, sediment compaction) and sea level. The resulting complex morphology comprises diversified landscapes varying from labyrinthic net of channels and lakes (fluvial delta) to massive tracts of monotonous reed marshes, large lagoons divided by barriers, or beach-ridge plains accommodating large transgressive dunefields (maritime delta). Whilst previous studies have focused on various sectors of the Danube delta, the current paper proposes for the first time an integral reconstruction of delta evolution based on existing and new sedimentological and morphological analyses and absolute ages (AMS 14C and OSL), enabling a comprehensive synthesis in terms of both evolutionary phases and growth patterns. A chronological framework was established for all the deltaic lobes and beach-ridge plains, highlighting the relationship between formation timespan, growth rates, and the resultant morphology.
This work unveils the early stage of delta formation, including the reconstruction of delta front advancement into Danube Bay (Old Danube lobe: prior to 7.5–5.5ka) and initial spit/barrier development (6.7/6.5–5.8ka). Inception of the bayhead delta started >1000yr before the relative stabilization of sea level and of the initial spit formation. The original fluvial delta plain topography is now buried at a depth of 4–6m depth below the present topography (representing the current stage of fluvial aggradation), as a result of subsidence and sea-level rise.
Regarding the maritime delta, six large open-coast lobes developed in the last six millennia, of which four were formed by the Sf. Gheorghe branch, attesting the long uninterrupted activity of this branch, whereas the other two were created respectively by the Sulina and the Chilia branches. The evolution of each lobe is derived from successive (chronological) shoreline positions and discussed in relation with changes in Danube discharge. Special attention has been paid to their growth stages and progradation rates. For the southern delta, we bring in new arguments for an active southern distributary (the Dunavăţ, derived from the Sf. Gheorghe branch) that formed successive open-coast lobes between 2.6 and 1.3ka. Additionally, we discuss the effects of modern anthropogenically-driven fluvial sediment reduction on the morphology and morphodynamics of the active lobes of the Danube.
•A new evolutionary scenario for the fluvial delta and initial spit is proposed.•Initial topography of fluvial delta is buried at 4–6m due to subsidence and SLR.•All open coast lobes were reconstructed in detail.•Wave reworking of lobes, subsidence and neotectonics affected southern delta.•The open coast Chilia lobe started as an open outlet since 0.9ka.
Understanding deltaic resilience in the face of Holocene climate change and human impacts is an important challenge for the earth sciences in characterizing the full range of present and future ...wetland responses to global warming. Here, we report an 8000-year mass balance record from the Nile Delta to reconstruct when and how this sedimentary basin has responded to past hydrological shifts. In a global Holocene context, the long-term decrease in Nile Delta accretion rates is consistent with insolation-driven changes in the 'monsoon pacemaker', attested throughout the mid-latitude tropics. Following the early to mid-Holocene growth of the Nile's deltaic plain, sediment losses and pronounced erosion are first recorded after ~4000 years ago, the corollaries of falling sediment supply and an intensification of anthropogenic impacts from the Pharaonic period onwards. Against the backcloth of the Saharan 'depeopling', reduced river flow underpinned by a weakening of monsoonal precipitation appears to have been particularly conducive to the expansion of human activities on the delta by exposing productive floodplain lands for occupation and irrigation agriculture. The reconstruction suggests that the Nile Delta has a particularly long history of vulnerability to extreme events (e.g. floods and storms) and sea-level rise, although the present sediment-starved system does not have a direct Holocene analogue. This study highlights the importance of the world's deltas as sensitive archives to investigate Holocene geosystem responses to climate change, risks and hazards, and societal interaction.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The western Makran subduction zone is capable of producing considerable tsunami run-up heights that penetrate up to 5 km inland. In this study, we show how climate change has affected urbanization ...along the tsunami-prone Makran coastline during the past 35 years. To address this issue, we have employed climate data, satellite altimeter radar, geomorphology and historical shoreline changes in order to shed light on the factors leading to a decline in access to freshwater resources and also rapid urbanization. We furthermore consider the interactions between environmental changes and human-induced coastal and catchment modifications in increasing socioeconomic vulnerabilities of littoral areas. The results of this study show that agricultural and freshwater management methods along the Chabahar coastal plain date back to at least 1808 CE, when wetter climate conditions characterized the area. Severe climate changes have been pronounced since 2000. Within this context, the majority of agricultural lands have been abandoned due to increasing drought intensity and duration. Decreasing cultivation and limited access to freshwater resources have led to extensive urbanization particularly for the two cities of Konarak and Chabahar. Enhanced soil erosion, increasing summer monsoon wind speed, sea-level rise and the growing number of strong storm events are some of the climate change-related hazards for high to very high socially vulnerable zones. In addition to environmental risks, poor urban planning has increased damage to coastal infrastructures such as ports and desalination plants. Furthermore, industrial and urban growth in the northwest of the Makran could further enhance socioeconomic damage by earthquakes and tsunamis.
The Nile valley accommodates the world's longest river and shaped the development of numerous complex societies, providing a reliable source of water for farming and linking populations to ...sub-Saharan Africa and the Mediterranean Sea. Its fertile delta lay at the heart of ancient Egyptian civilization, however little is known of its morpho-sedimentary response to basin-wide changes in Holocene hydrology. Here, we present two well-resolved records from the Nile delta (based on ∼320 radiocarbon dates) to reconstruct the timing and rhythm of catchment-scale modifications during the past 8000 years. On the orbital timescale, we demonstrate that Nilotic hydrology and sedimentation have responded to low-latitude insolation forcing while, on sub-millennial timescales, many of the major phases of deltaic modification were mediated by climate events linked to El Niño Southern Oscillation-type (ENSO) variability.
► Timing and rhythm of Nile modifications reconstructed for the past 8000 years. ► Nilotic hydrology and sedimentation have responded to low-latitude insolation forcing. ► On sub-millennial timescales, deltaic modification was mediated by ENSO variability. ► Deltas are key archives to understand the interplay between climate forcings and human occupation.
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