Keywords:
Geoarchaeology, Palaeoenvironmental, Palaeo-Sediments, Landslide and Tectonic Movments, Roman Anchor, Greek harbour, Holocene Sea level change, Ras Hawala, Ras Alam El-Rum, Palaeo- tsunami, Graias Gony harbour, Egypt.
Abstract:
Graias Gony is submerged harbour in Ras Alam El-Rom area as a part of the NW coast of Egypt. Some geoarchaeological remains were discovered by Underwater Archaeology 20- 23rd October survey in the eastern side of Ras Alam El-Rum coastline on the NW coast of Egypt, East of Matruh city with extension about 16.9 km, SW Ras Alam El-Rom, in the same location of the above submerged harbours were described by another early writers.
The geomorphological characteristics were studied for all locations but the coastline were changed from the Roman period up to recent time by coastal erosion and other geomorphic processes in addition to the Holocene sea level change.
It was mentioned by Claude Ptolmee, who named it the Geographer Ptolemios, in his book in the year 150 AD in a list of ports in the Mediterranean Sea (Abd El Maguid. 2001). This port is one of the largest ports located on NW coast of Egypt and was recently named Rumaila harbour in reference to the type of coastal rock deposits spread in it along with The sandy sediments diminished greatly, which prompted the Bedouins to give it this name. The researcher found clear evidence showing sea level changes in this harbour, the most important of which are Notches and submerged platforms. I studied the geomorphological characteristics for their location, noting that coastal erosion, other geomorphic processes, and the Holocene Sea level change have altered the coastline from the Greek and Roman periods to the present. Alternating Quaternary limestone, part of an eroded carbonate coastal ridge, occupies the study area. We observed geomorphic coastal landforms along the shore, such as multi-level marine notches, platforms, and caves. These features were created at the Holocene relative sea level. We also observed solution microlandforms such as holes, channels, pits, and residual pinnacles. Sea water sculpted these features on carbonate rocks.
How to cite: Moustafa, S., Torab, M., and Elsadany, A.: Geoarchaeological indicators of sea level change during the Roman period in Graias Gony submerged Roman harbour site between Ras Hawala and Ras Alam El-Rum areas, NW coast of Egypt Using the diagram PADM, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-570, https://doi.org/10.5194/egusphere-egu25-570, 2025.
The development of the NW German coast is characterised by the sea level rise since the beginning of the Holocene and a resulting general retrogradational shift of the coastline. Extreme events, i.e. storm surges, have also contributed to these changes and should not be underestimated.
The palaeo-coast was un-diked and thus the morphological conditions and sedimentary processes differed fundamentally from those observed at the present-day coast. It can be assumed, that prehistoric storm surges therefore had different effects on the coastal environment at the time. Sedimentological records of such events are documented along the East Frisian North Sea coast and the Ems-Dollard estuary. However, the short-term and long-term effects of storm surges on the palaeo-coast remain poorly understood. How far and how strong did the water inundate the hinterland? Did they trigger transgressions, which have been originally correlated to increased sea level rise? Are there regions particularly vulnerable to erosion and if yes, what are the geological preconditions?
In the scope of the multidisciplinary project “CoastAdapt”, we approach these questions by focusing on mm to cm thick clastic seams within peat horizons of the Holocene coastal sediments. Such deposits can only be formed during severe storms when the water reaches the fens of the hinterland or in a peat cliff situation. In the latter case the upper part of the peat is being uplifted, fine-grained clastic material is deposited, and eventually preserved within the peat when the upper part is settling again after the storm. Therefore, these clastic seams are a well detectable archive of storm surge history along the coast.
Here, we present first results of the spatial distribution of these storm surge layers for different time segments based on comprehensive analyses of borehole archive data together with updated sea level rise data for the NW German coast. Furthermore, we present preliminary considerations regarding the potential influence of geological conditions that may have facilitated the inundation by storm surges.
How to cite: Bruns, I., Bungenstock, F., and Karle, M.: Prehistoric storm surges during the Holocene – triggers for long-term changes of the NW German coast?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4112, https://doi.org/10.5194/egusphere-egu25-4112, 2025.
This study wants to evaluate the paleo-landscape evolution since the MIS 5 of Cilento coastal sector (Tyrrhenian Sea) by means of an innovative methodology that combines traditional geostatistical techniques with machine learning applied to paleo sea-level markers (SLMs), including SLIPs, TLPs, and MLPs, integrated with morphometric DTM analysis.
The study area is the Cilento coastal sector located along the Tyrrhenian coast of Southern Italy. This area preserves several features witnessing sea-level fluctuations but, despite the area having been intensely studied since 1940, no comprehensive database encompassing the local paleo sea-level evidence existed prior to this research. The area has been chosen due to its tectonic stability, which ensures consistent correlations to the same age of the markers having the same altimetric position.
The initial phase involved collecting and updating data from the Campanian Natural Cavities Inventory (Russo et al., 2005) and conducting extensive field surveys. This effort resulted in the PALEOScape geodatabase (Sorrentino et al., 2023), where data were classified using new indexes: the Environmental Index Point (EIP) and Environmental Limiting Point (ELP), reflecting varying levels of uncertainty in paleo-shoreline positions. Subsequently, morphometric DTM analysis and spatial queries overlaid the geodatabase, generating a Random Forest dataset trained on 500 records. This methodology was validated with two levels of validation: a first level of statistical analysis on the training dataset, and a second level across four deeply surveyed coastal areas serving as ground truth. The accuracy of the resulting models ranged from 0.7 to 1. In this way, a prediction value was obtained even where no markers are present.
The approach enabled extensive paleoenvironmental reconstructions for the Cilento region during the Last Interglacial Period, modelling scenarios at both high and low sea-level stands. These findings provide an evolutionary model of coastal changes, demonstrating the utility of integrating traditional and advanced techniques for robust paleoenvironmental analysis.
In conclusion, this work offers a novel framework for large-scale paleo-coastal reconstructions, facilitating the evaluation of shoreline evolution and its implications for past human activities and future coastal management.
How to cite: Sorrentino, A., Mattei, G., Pappone, G., and Aucelli, P. P. C.: Paleo-seascape reconstructions along the Cilento coasts (Tyrrhenian sea) by innovative AI approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10719, https://doi.org/10.5194/egusphere-egu25-10719, 2025.
The last glacial period hugely affected the modern landscape of high latitude regions of the Northern Hemisphere, as continents and surrounding shelves were covered by massive ice sheets. Deglaciation of these ice masses during the late Pleistocene resulted in isostatic rebounds in response to unloading. In many regions the initial uplift changed to isostatic subsidence in response to the movement of the collapsing forebulge margin and hydro-isostatic loading. As a consequence, many modern coastal regions nowadays still experience subsidence, which in many cases is accompanied by a rise in relative sea level (RSL). The timing and impact of a retreating ice sheet on the continental shelf environments, and the potential effects on local seal level is, however, still poorly understood in many regions of North America. In addition, the effects of short-lived climatic events on ice dynamics such as the Younger Dryas are still debated. In this study we provide new information on the dynamics of deglaciation and sedimentation along the outer margin of the Laurentide Ice Sheet in the southern Gulf of St. Lawrence off Prince Edward Island, located on the eastern Canadian Continental Shelf. Here, many questions remain as to the sedimentary processes following the Last Glacial Maximum (LGM) and, in particular, the influence of the Younger Dryas on the deglaciation and sedimentation. Using information from sub-bottom profiles, sediment cores and multibeam bathymetry from the Gulf of St. Lawrence, we were able to determine geological processes that affected sedimentation and used this new information to reconstruct the deglaciation history and RSL changes since the LGM. This study demonstrates that the bedrock morphology was shaped during the last glacial period, with the Younger Dryas cooling event having a particularly significant impact on sedimentation processes in the southern Gulf of St. Lawrence. Paleo-basins and channels, likely glacially excavated, were completely filled with late Pleistocene glaciolacustrine to marine sediments. Most of these sediments were deposited during the early Younger Dryas, with sedimentation rates as high as 1 cm a-1, which were likely a consequence of readvancing ice masses. We further observe an erosional truncation on top of the Younger Dryas sediment package, which presumably indicates a drop in RSL before the Holocene. The new paleo-environmental reconstruction of the region not only sheds light on the potential impact of short-lived climatic events during deglaciation but also reduces uncertainties in our knowledge about past sea level changes.
How to cite: Maselli, V., Schulten, I., King, E., Asioli, A., Schmidt, M., Hensen, C., Müller, T. H., Micallef, A., Berndt, C., Brown, C. J., Cordoba-Ramirez, F., Elger, J., Hölz, S., Kotliarov, A., Kurylyk, B., Michael, H., Robert, K., Yu, S., and Nedimovic, M.: Impact of ice sheet dynamics and short-lived climate oscillations on the late Quaternary stratigraphy and paleo-environments of the Gulf of St. Lawrence off Prince Edward Island (Canada), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10484, https://doi.org/10.5194/egusphere-egu25-10484, 2025.
Sediment accumulation rates can be notoriously hard to measure over geomorphic timescales in coastal systems. Anthropogenic metals, if their provenance can be constrained, can act as tracers and help to build a much more detailed understanding of these processes on decadal/century timescales. Past industrial activity and the history of warfare along the coast of Normandy, France has been the subject of intense study due to its significance to historians, having been the site of the largest naval invasion in history during World War II. Previous publications attribute much of the anthropogenic metal on these beaches to the battle and related events, and this detailed sedimentological study across the five main landing sites shows consistent presence of anthropogenic metal based on approximately 300 samples collected from 16 surface transects and 21 sediment cores. Along with characterization of metals, sediment size distribution was quantified for each of the samples.
Sediment size varies significantly across all five sampled beaches, ranging from very fine to very coarse sand and pebbles. Grain size distribution shows consistent trends however, with all surface transects showing an abrupt decrease in grain size at the transition from the backshore to the foreshore. For all but one locality (Sword Beach, which is near the mouth of the Orne River and has a higher average grain size), surface samples taken below the high tide mark are dominated by fine to very fine sands (greater than 80%). Sample grain size distribution changes very little within the active foreshore, showing a higher degree of sorting and textural maturity when compared with coarser and more poorly sorted samples from above the high tide line. This clear break in mean sediment size and sorting is mimicked by distribution of anthropogenic metals, with a pronounced increase in concentration of these metals below the high tide mark, where system energy is greatest.
While the high tide line (foreshore/backshore transition) marks a pronounced shift in both grain size and metal concentration based on surface samples, abrupt transitions in grain size and metals concentration do not align in the same way at depth. Samples show a clear and abrupt increase in grain size at ~15 cm for all but Sword Beach (~45 cm), but there is little to no obvious change in metals concentration at this level. Rather, there is an abrupt decrease in metals concentration deeper, at ~45 cm depth. This decoupling of grain size and metals concentration suggests that metal concentration in the cores is potentially a function of time rather than depositional energy and processes. If much of this material is attributed to the invasion of Normandy in 1944, this suggests an approximate sediment accumulation rate of ~ 0.57cm/year. If metals can be partially attributed to earlier industrial activity, such as the opening of the Société Métallurgique de Normandie in 1912, net annual sediment gain is slightly lower. Ongoing work promises to better constrain sedimentary processes along the Normandy coast and other analogous coastlines both in the present and ancient geologic records.
How to cite: Hudson, S., Laycock, D., Pemberton, E., Burridge, G., Grover, C., Ramirez, K., Tatum, O., and Robinson, J.: Using the ‘War Sands’ of World War II as Tracers of Geomorphic Processes and Rates – Sedimentology on the 80th Anniversary of the Allied Invasion of Normandy, France, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16461, https://doi.org/10.5194/egusphere-egu25-16461, 2025.
Coastlines in eastern Canada are dominantly paraglacial, meaning that the geomorphology and morphodynamics of the coasts are largely governed by the presence of glacigenic deposits related to the Laurentide Ice Sheet. These deposits act as antecedent topography and sediment sources for these coastal systems. Chedabucto Bay (Nova Scotia, Canada) is site to uniquely preserved drowned barrier beach features, which are hypothesised to form through shoreline retreat and barrier overstepping. In this process, relative sea-level (RSL) rise forces the barrier to migrate landward, then, when the conditions allow, to be preserved in place. Due to the nature of these paraglacial beaches to organize into coarse clastic barriers, they are quite resistant to shoreline migration through wave action thus have a bias towards overstepping when compared with sandier systems. This high degree of preservation is useful for reconstructing the post-glacial sea-level history as these features are good indicators of past RSL. Here we investigate the external morphology and internal architecture of modern and drowned barrier-beach systems by using ground-penetrating radar and LiDAR, for the former, and multibeam bathymetry and seismic reflection data, for the latter, to study their differences. Offshore seismic mapping has revealed buried barrier-beach systems at ~46 metres below present-day sea level and former paleo-estuaries dated to have formed by 10.51 ka cal BP. Preliminary morphometric analysis of drowned barrier systems indicate maximum berm heights of ~5 m from toe of slope, which is comparable to those observed in the modern system. The height of the modern barrier systems varies alongshore depending on beach aspect and the dominant direction of currents and waves (drift-aligned versus swash aligned systems). Recently surveyed paraglacial barrier elevation data along northern Chedabucto Bay show a ~3 metre difference in maximum berm crest elevation between swash and drift aligned systems. With this we emphasize the need to differentiate the expected indicative range for these relict paraglacial RSL indicators based on surficial morphology and internal geometries known from modern systems. The results of this work will help inform and guide science and policy on managing shoreline retreat through overstepping and help in characterizing sediment type distribution in coastal-shallow marine paraglacial environments.
How to cite: Greaves, C., Eamer, J. B. R., and Maselli, V.: Past relative sea-level indicators in coarse-grained paraglacial coastal systems from Eastern Canada, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13747, https://doi.org/10.5194/egusphere-egu25-13747, 2025.
The global transgression following the Last Glacial Maximum (LGM) greatly impacted vast areas of previously subaerially exposed continental shelves. When modeling paleocoastlines related to the post-LGM transgression present-day bathymetry is most commonly used as input. This study demonstrates the considerable errors that result from such an approach and highlights the importance of using realistic paleobathymetry for modeling past land-sea extent. Additionally, it presents some new insights on the Holocene transgression in the Gulf of Trieste. The results of this study were recently published in Novak (2024).
Modeling was conducted in the Gulf of Trieste (northern Adriatic Sea) where the Late Quaternary stratigraphy and sea-level history are relatively well known. Two elevation datasets were used as input data: present-day bathymetry from the EMODNET Bathymetry consortium (2022) and pre-transgressional topography from Trobec et al. (2018). The paleocoastline was modelled at several water levels between 30 and 20 meters below present-day sea level. The two elevation datasets were flooded with the “Simulate Water Level Rise/Flooding” tool in the Global Mapper GIS software. Higher sea-levels during storms and high tides were accounted for with an added increase of 1 m to the water-levels. The sea-level curve from Kaniewski et al. (2021) was used to chronographically constrain the paleocoastlines.
The modeling results on both datasets demonstrate a striking disparity, especially at the initial phases of the transgression. The largest difference is evident for -25 m: the sea barely enters the gulf when flooding the present-day bathymetry, however roughly half of the gulf is already flooded then using the paleotopographic elevation model. In this case, the differences in the maximum extent of both coastlines amounts to more than 25 kilometers NE and approximately 10 kilometers NW. Such large discrepancies have significant implications for paleoreconstruction studies. As sea-level is increased the differences in the paleocoastline positions gradually reduce until they drop below 5 km.
Additional deeper sea levels were modelled on the paletopographic dataset in order to try to better understand the dynamics of the transgression. Results show that the sea started to enter the Gulf of Trieste after it rose above -29 m a.s.l. This is corroborated by so-far published sea-level data. After sea level reached this elevation approximately half of present-day gulf was abruptly flooded. The predominant transgression direction was towards the northeast and later oriented towards the northwest. The transgression was probably controlled by the regional paleotopography which resulted from the sedimentary activity of the Southernalpine megafan systems.
REFERENCES:
EMODnet Bathymetry Consortium, 2022. EMODnet Digital Bathymetry (DTM 2022). https://doi.org/10.12770/ff3aff8a-cff1-44a3-a2c8-1910bf109f85
Kaniewski, D. et al., 2021. Coastal submersions in the north-eastern Adriatic during the last 5200 years. Global and Planetary Change 204, 103570. https://doi.org/10.1016/j.gloplacha.2021.103570
Novak, A., 2024. Paleocoastline modelling – What a difference a few meters of sediment make? Quaternary International 706, 49–59. https://doi.org/10.1016/j.quaint.2024.07.005
Trobec, A. et al., 2018. Thickness of marine Holocene sediment in the Gulf of Trieste (northern Adriatic Sea). Earth System Science Data 10, 1077–1092. https://doi.org/10.5194/essd-10-1077-2018
How to cite: Novak, A.: Modelling the Holocene marine transgression in the Gulf of Trieste (northern Adriatic Sea): The importance of paleotopography in paleoreconstructions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17898, https://doi.org/10.5194/egusphere-egu25-17898, 2025.
Sea level rise is a worldwide phenomenon affecting most of the coastal areas of the Mediterranean. Delta plains are among the most vulnerable coastal areas to sea level fluctuations, mainly due to their low relief and their unconsolidated sediments which are commonly developed extensively along their deltaic setting. This makes river deltas one of the best cases for assessing a number of implications associated with the anticipated future sea-level rise.
Kalamas River, one of the longest rivers in Greece, has a delta plain which covers an area of around 70 km2 and has been extensively influenced by sea level fluctuations during Holocene. The greater area of the plain can be considered both economically and socially important, as it hosts significant farming activities, protected wetland habitats and is also surrounded by well-developed urban areas. Examination of aerial photographs and satellite images, taken in various years, revealed that the old southern mouths of the river has been facing severe inundation problems due to sea level rise, while the northern currently active mouths appears to have been progradating towards the sea.
This study deals with the geomorphological investigation and paleoenvironmental reconstruction of the delta plain of Kalamas river, based on a multidisciplinary approach, including mineralogical, sedimentological and geochemical analysis as well as absolute dating of twenty six core sediments, collected from four different boreholes along the delta plain. The derived data were incorporated into different chronological-palaeoenvironmental simulation models to reconstruct the evolution of the delta plain during the Holocene, but also predicts changes for future sea level rise scenarios. Digital mapping of the evolutionary changes (including future scenarios) taken place in the plain are then depicted using GIS.
This study revealed that geomorphological changes in the delta plain are directly associated with human interferences (construction of a dam, modifications of channels as well as river diversion). Delta progradation is mainly observed in the greater area of the currently active river mouths, while the older (currently inactive) mouths are now retreating. It could be suggested that the predicted sea level rise will greatly affect the delta plain (especially its current shoreline), causing extensive adverse socio-economic and environmental impacts.
This research was supported by the project “ Study, forecasting and modeling of the effects of climate change on the deltaic coastline of Kalamas River” (MIS 5006050) funded by NSRF 2014-2020.
How to cite: Kazantzaki, M., Filippaki, E., Tsakalos, E., Bassiakos, Y., and Christodoulakis, I.: Palaeoenvironmental reconstruction of Kalamas river delta plain-NW Greece, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20259, https://doi.org/10.5194/egusphere-egu25-20259, 2025.
Delaware Bay is one of the largest estuaries along the eastern coast of North America. The coastal geomorphology is controlled by modern processes and the ancestral landscape. Paleogeomorphology includes fluvial landforms of lower Delaware River valley that drained across the coastal plain to the edge of the continental shelf, Pleistocene dune fields and other periglacial features. The estuary has been developing since the early Holocene and continues to present due to relative sea level (RLS) caused by eustatic changes, isostasy, and local processes. Marine transgression inundated Delaware River converting ancestral drainage network into embayment and lagoons fringed by salt marshes. Associated with continued sea-level rise and widening of the estuary, increase in fetch caused the transition from tidal wetlands and mudflats to barrier beaches in the lower Delaware Bay. Paleo-environmental reconstructions document the coastal system response to natural changes should be considered in analysis of landscape response to climate change.
The Delaware Bay region has been occupied by humans since the Paleoindian period (~ 12,000-8,000 BP), was characterized as one of the most culturally diverse in colonial America and is today the location of several vibrant coastal communities.
Although some of the Paleoindian and later archaeological record has already been submerged due to SLR, numerous remaining cultural resources hold invaluable cultural resources and scientific information. Paleo-landscape reconstructions are critical to discover, document, and conserve buried archaeological sites as well as above ground historical resources.
Recent acceleration in the rate of sea-level rise is threatening the Delaware Bay coastal ecosystems, cultural resources, and living communities.
We used lidar and high-resolution drone imagery to map the modern coastal landscape, salt-marsh sediments as proxies for sea-level reconstructions, and stratigraphic relationships to reconstruct paleo-landscapes, and the chronology of abrupt or gradual environmental changes that impact coastal landscape. We used GIS-based paleo-landscape models to identify priority locations for systematic cultural resources survey and applied probabilistic SLR projections and SLOSH model to predict the impacts of future RSL and storm surges on the coastal landscape.
How to cite: Nikitina, D., Wholey, H., and Kim, Y. H.: Paleo-landscape reconstruction and future predictions of impact of SLR and storm surges in Delaware Bay, USA. , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21292, https://doi.org/10.5194/egusphere-egu25-21292, 2025.
This study investigates the Holocene Relative Sea Level (RSL) fluctuations and their impacts on coastal landscapes in the Fondi Coastal Plain. This typical low-lying coastal area, spanning approximately 95 square kilometers along the Central Tyrrhenian Sea in Italy, is characterized by significant portions of its surface lying below mean sea level. This geomorphological configuration makes the plain particularly sensitive to sea-level changes and associated processes, including flooding and sedimentary dynamics.
The Upper Pleistocene to Holocene geomorphological evolution of this plain derives from a complex interplay between tectonic subsidence, glacio-eustatic sea level change, and sedimentary inputs coming from surrounding carbonate reliefs.
The research integrates a comprehensive geodatabase of RSL markers with new high-resolution stratigraphic, sedimentological, paleoecological, and geochronological datasets, alongside reinterpreted previous data. Overall data provide morphostratigraphic and geochronological constraints to the late Upper Pleistocene to Holocene evolution of the Fondi Plain coastal areas.
Two boreholes were drilled in the area according to the PRIN 2022 GAIA project goals. Sedimentological analysis, radiocarbon dating (¹⁴C), and Optically Stimulated Luminescence (OSL) dating allowed to reconstruct the main moments of coastal flooding and progradation/aggradation since the Late Pleistocene.
In detail, concerning the Holocene, the coastal evolution was influenced by an initial rapid rise from approximately −19 m MSL to −5 m MSL between 9 and 7 ka BP, followed since the mid-Holocene by a deceleration up to near present-day level.
Lagoonal environments in the new core, constrained approximately between 7 Ka to 4 Ka, testify a substantial stability of the coast. This behaviour was confirmed also by new Roman geoarchaeological SLIP data along the coast running from Fondi to Formia, indicating a relative sea level positions during the 1st century CE at approximately -0.55 ± 0.29 m MSL. These findings align with regional GIA models, confirming tectonic stability and subsidence rates of approximately 0.03 mm/yr over the past 2.0 ka.
These findings contribute to the coastal vulnerability analysis related to sea level rise induced by climate change.
How to cite: Gionta, A., Aiello, G., Amodio, S., Barra, D., Parisi, R., Mattei, G., Valente, E., and Aucelli, P. P. C.: Coastal Responses to Holocene Sea Level Rise in the Fondi Plain (Central Italy) by means of new borehole and geomorphologic data. , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19290, https://doi.org/10.5194/egusphere-egu25-19290, 2025.
During the last glacial period (ca. 120 ka to 11.7 ka), the North Sea region was surrounded by ice sheets covering the British Isles (British-Irish Ice Sheet; BIIS) and Scandinavia (Fennoscandian Ice Sheet; FIS). At times of maximum expansion, these ice masses even coalesced over the North Sea, which had largely emerged due to global glacio-eustatic sea-level lowering. There is some limited sedimentological evidence suggesting that a proglacial lake existed in this emerged southern North Sea basin south of the ice margin. Because of the assumed importance of proglacial lakes in this area, also during older glaciations for their role in e.g. the opening of the Dover Strait, many attempts have been made to define the extent of these lakes. These hypothesised reconstructions have often ignored the effect of glacio-isostasy. In this study, the bedrock deformation in the North Sea basin resulting from the load of the surrounding ice sheets throughout the last glacial period was modelled by using different ice-sheet reconstructions as input. The modelling was performed by relying on a simple but proven model that considers the two most important involved layers, the lithosphere and the asthenosphere. The results indicate that during the peak glacial phases of the last glacial period – MIS 2 and MIS 4 – the area directly south of the ice margin in the North Sea basin was deeply depressed, up to almost 100 m of subsidence. The combination of this bedrock deformation together with the already present low-lying topography in the Oyster Ground region created an enlarged basin that could have been filled with water to develop a proglacial lake with a volume of up to 3 000 km3. This basin would only have been completely inundated if sufficient water was delivered to it, but the extensive supply from rivers such as the Elbe and glacial meltwater make this condition not unlikely. It seems implausible that a proglacial lake would have extended beyond our suggested limits, as a larger lake would have spilled over a relatively low topographic barrier into the Axial Channel and further towards the Dover Strait. After disconnection of the BIIS and FIS over the North Sea, the remainder of the lake water likely drained towards the north, potentially as a high-volume Glacial Lake Outburst Flood (GLOF).
Beyond the zone of bedrock subsidence, glacio-isostasy also induced a small region of uplift surrounding the depressed area, i.e. the flexural forebulge. Within the region of interest for this study, the area of maximal uplift was situated at the present-day Netherlands. This forebulge likely slightly tilted this relatively flat area, contributing to the southward shift of the Rhine river course during MIS 3, as was already suggested in previous studies.
Our modelling results provide additional support for the hypothesis that glacio-isostasy has had a profound impact on the hydrology and drainage patterns in the southern North Sea basin, during periods of maximum glaciation.
How to cite: Bertels, R. and De Batist, M.: Impact of glacio-isostasy on topography, hydrology and drainage patterns in the southern North Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1210, https://doi.org/10.5194/egusphere-egu25-1210, 2025.
Although wave erosion mediated by salt weathering due to seawater supply and solar radiation has been suggested to be the main factor in the growth of tafoni-like depressions in the seawater splash zone, there are no quantitative measurements of salt deposition or deposition distribution. In this study, we analyzed the distribution of salt deposition on the rock surface by mapping the deposition and adhesion of salts and examined the relationship between the distribution of salt deposition and the growth of depressions. The study area is the Yayoi Bridge over Aoshima, Miyazaki Prefecture, Japan. The bridge was built in 1951 and the piers are made of blocks of the same sandstone as the bedrock of Aoshima. There are 144 sandstone blocks forming the wall, set in 11 layers. The layers are numbered from the bottom to the top, with the lowest being the 1st layer and the highest being the 11th layer. Continuous studies on the formation of tafoni-like depressions have been conducted here since 1970s. In this study, the spectral reflectances of rock surfaces were measured using a portable spectrometer. The results showed that the effect of salt on the Original Reflectance (OR), which was processed by Continuum Removal (CR), and Normalized Difference Spectral Index (NDSI), was remarkable. The salt distribution on the south face of the piers was estimated to be thicker in layers 4 to 6 and thinner in layers 8 to 11. The CR-treated values showed a positive correlation (0.55) with depression volume, while NDSI showed a negative correlation (−0.52), suggesting that salt accretion distribution, or salt weathering, is the main cause of weathering of the sandstone blocks. In addition, a comparison of depression depths at 20, 38, 50, and 73 years after completion showed a decreasing trend in the overall rate of increase, but a high rate of increase was still observed in certain layers. The main reason for this is that the potential for salt weathering is still high in the deeper part of the depression, which continues to expand. In the future, it is desirable to develop a measurement method that can acquire salt distribution more simply and efficiently using a camera or other equipment.
How to cite: Sato, K., Wakasa, S., Aoki, H., and Kurihara, J.: Formation of tafoni-like depressions and salt accretion distribution in the seawater splash zone, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3903, https://doi.org/10.5194/egusphere-egu25-3903, 2025.
Understanding long-term relative sea-level (RSL) changes and coastal dynamics in geologically stable areas is vital to decoding the interplay of natural processes and human adaptations. This multidisciplinary research explores the connection between mid-to-late Holocene sea-level shifts and tectonic influences along the mid-Tyrrhenian coastline, spanning the Fondi and Garigliano coastal plains.
During the Roman era, the city of Formia emerged as a pivotal observation point for the Tyrrhenian Sea, functioning as a major commercial hub with extensive urban development along its shores. Nowadays, this is testified by numerous archaeological remnants perfectly preserved along the coastal area.
To reconstruct the morpho-evolution of the coastline and RSL changes during the mid-to-late Holocene, a geodatabase comprising 52 sea-level markers (SLMs) was created. These markers were derived from direct geoarchaeological assessments, stratigraphic and paleoecological analyses of new borehole data, and existing stratigraphic studies. Radiocarbon dating of three peat samples yielded fresh RSL insights, ranging from 7.62 ± 47 ka BP to 1.00 ± 51 ka BP. The dataset shows that between 9.0 and 8.0 ka BP, the sea level rose from -19 m to -6.5 m at a rate of approximately 15.6 mm/year, eventually decelerating to 0.8 mm/year and stabilizing near present-day levels. During the 1st century BC, the local sea level is estimated to have reached no higher than -0.55 ± 0.29 m.
The analysis of these SLMs supports the notion of tectonic stability in the region over the past 2.0 ka. This conclusion aligns with RSL data falling within the glacial isostatic adjustment (GIA) signal, and the calculated average vertical ground movement rates of -0.017 ± 0.23 mm/year.
Additionally, by integrating data from bibliographic sources, new geoarchaeological surveys, and geomorphological investigations, the study identifies significant coastal changes over the last 2.0 ka. These transformations are largely marked by coastal progradation, driven by a combination of natural forces and human interventions.
How to cite: Caporizzo, C., Gionta, A., Mattei, G., Vacchi, M., Aiello, G., Barra, D., Parisi, R., Corrado, G., Pappone, G., and Aucelli, P. P. C.: Holocene Coastal Dynamics and Relative Sea-Level Variations along the Mid-Tyrrhenian Coastline, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4382, https://doi.org/10.5194/egusphere-egu25-4382, 2025.
Southern and southeastern Spain has experienced an outstanding coastal landscape change since the middle Holocene, when most of the lower reaches of fluvial valleys were drowned by the mid-Holocene sea level highstand. Since then, many of the main rivers have seen how their mouths evolved from open estuaries discharging into wide embayments to broad wetlands isolated from the open sea by the growths of spit bar systems.
The silting up of these estuaries led to the development of flat lowland areas where geological processes such as floodings, earthquakes and tsunamis affected historic and prehistoric coastal settlements inducing severe landscape changes, that triggered abrupt abandonments of sites and important population changes. Multiple geoarchaeological data support this complex interaction among coastal changes and ancient populations from at least Late Bronze times including Phoenician and Roman settlements in the Atlantic and Mediterranean Iberian littorals.
Good examples of this evolution are, among many others, the present marshlands at the Guadalquivir (Atlantic) and Segura (Mediterranean) river mouths. Historical descriptions show that during roman times (1st century BCE) the present Guadalquivir marshland (Doñana National Park) was an ancient embayment (Lacus Ligustinus) that was progressively closed by the growth of large spit-bars since roman times. Geological and historical data indicate the occurrence of several islets downstream Sevilla and the initial filling of the ancient bay by a prograding delta-like environment. A severe tsunami event (218-90 BCE) reshaped the geometry of the littoral spit bar system inducing important coastal changes and site abandonments. Progressive growth of the closing spit bars, and coeval fluvial dynamics accelerated by the strong deforestation suffered in Spain in the 19th century, caused the continuous infilling of these embayments.
The evolution of the coastal landscape at the Segura River mouth (Lower Segura Depression) is quite similar, with a Segura River mouth evolving from a mid-Holocene estuary to a delta environment that grew into a broad brackish lagoon isolated from the open sea by spit bar systems (Sinus Ilicitanus) during Phoenician to Roman times. This lagoon environment persisted till the dawn of the 17th century CE when it was anthropically infilled for the agricultural improvement of the zone. These reclaimed lowlands suffered destructive earthquakes during Phoenician, Roman, Muslim and modern times. The first documented event affected a littoral Phoenician settlement (7th century BCE) and the last destructive one was the 1829 AD Torrevieja earthquake with multiple liquefaction cases inland and coastal uplift of centimetric scale (10-15 cm). Both events have triggered the destruction, abandonment and relocation of several localities.
In both cases, these lowland coastal areas have been recurrently affected by severe flash-flood events, storm-surges, tsunamis and large earthquakes. The massive urbanization and tourism improvement of these zones, before modern practices of land planning and management, imprint to these coastal zones an important multi-hazard nature to be considered by policy makers for future land-use planning.
Acknowledgements: This is a contribution to IAG Working Group on Coastal Geoarchaeology; supported by the Spanish Research Project I+D+i PID2021-123510OB-I00 (QTECIBERIA-USAL) funded by the MICIN AEI/10.13039/501100011033/.
How to cite: Bardají, T., Silva, P. G., Prados-Martínez, F., Élez, J., Giner, J. L., and Sánchez-Sánchez, Y.: Paleo-landscape evolution and abrupt changes in Spanish coastal settings: insights into hazard analyses and risk management., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6077, https://doi.org/10.5194/egusphere-egu25-6077, 2025.
This research aims to reconstruct the sea-level oscillations that occurred since the Late Pleistocene along the western coast of Laconia, a tectonically active region located in SE Peloponnese. This area exhibits a prominent marine terrace sequence, which serves as a key marker for understanding regional landscape evolution during Marine Isotope Stage 5 (MIS 5). Additionally, some geoarchaeological evidence witnesses the Holocene coastal morphology. According to previous studies, the uplift of this area can be considered a signal of the subduction of the African lithosphere beneath the Eurasian plate.
To analyse the terrace system, a combination of direct and indirect survey techniques was employed across eight sites. Firstly, the marine terraces were extensively identified and mapped by GIS and machine learning analysis, then detailed field-mapping and DGPS mtechniques were carried out in some strategic points along the entire coastal sector. Optically Stimulated Luminescence (OSL) dating is going to be performed on a caprock sample, whose elevation is consistent with the one of a terrace order investigated in previous studies in order to corroborate their MIS 5 dating. Lastly, remote sensing and aerial imagery interpretation were utilized to detect the seabed morphology for the analysis of Holocene trends.
The results underline three MIS 5 high stands at 8 ± 2, 16-24 ± 2, and 40-50 ± 2 m asl, widely documented by well-shaped terraces along the whole region.
Furthermore, the submerged prehistoric settlement remains of Pavlopetri and Plytra at different depths demonstrate Holocene sea-level stands testifying a local subsidence, whose occurrence is supported also by the presence of three submerged beachrocks in the Bay of Vatika (Pizarro et al. 2012).
The findings from geomorphological analysis confirm a homogeneous long-term tectonic behaviour in the entire emerged coastal area, providing a broader regional context for the terrace system evolution, while the geoarchaeological analysis suggests recent local subsidence in specific submerged sectors.
The proposed methodology provides a robust framework for the paleo-landscape and sea-level reconstruction since MIS 5 at a regional scale through a comprehensive analysis of terrace distribution and submerged archaeological remains by integrating new technology, GIS and AI analyses.
How to cite: Mattei, G., Sorrentino, A., Tsanakas, K., Aucelli, P. P. C., and Karymbalis, E.: Long-term evolution of western Laconia Peninsula through an integrated geomorphological and geoarchaeological analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12726, https://doi.org/10.5194/egusphere-egu25-12726, 2025.
