Marine Geology最新文献

{"title":"Closure of Khor Al Balid and Khor Rori harbours/estuaries with coastal uplift and aridity in the 12th – 15th c. CE and evidence for an extreme overwash event in the 18th – 19th c. CE: Implications for ancient port sites in southern Oman","authors":"Riley E. Steele ,&nbsp;Eduard G. Reinhardt ,&nbsp;Joe Boyce ,&nbsp;Jeremy J. Gabriel ,&nbsp;Tom Vosmer","doi":"10.1016/j.margeo.2024.107282","DOIUrl":"https://doi.org/10.1016/j.margeo.2024.107282","url":null,"abstract":"<div><p>Ancient maritime trading ports along the southern coast of Oman have been the target of archaeological excavations for several decades. Though historical chronologies are well-researched, information from a paleoenvironmental perspective is lacking and can provide a more complete understanding of site development. This study investigates the timing of coastal sand barrier accumulation in the natural harbours at Khor Al Balid and Khor Rori, which had considerable effects on the populations at the ancient cities of al–Balīd and Sumhuram, respectively. Six cores from Khor Al Balid and four cores from Khor Rori were analyzed using sedimentological, microfossil (foraminifera and testate amoebae), geochemical (μXRF), and radiocarbon dating methods. Marine proxies (e.g., <em>Amphistegina</em> spp., <em>C. pseudolobatulus</em>, <em>E. limbatum</em>, Sr, Ca/Si) and lagoon proxies (e.g., <em>T. macrescens</em>, <em>T. inflata</em>, <em>C. constricta</em> and <em>C. aculeata</em>, Ti/Ca, Fe/Ca) were used to identify Marine Sand, Brackish Lagoon/Marsh, and Freshwater facies. Results indicate that the eastern arm of Khor Al Balid closed off from the sea around the 12th century CE and that the western arm closed around the 15th century CE. Siltation of harbours and the formation of sand barriers may have contributed towards site abandonment. Previous archaeological findings suggest that al-Balīd was able to continue with maritime trade activities along the southern seaside edge of the city for several centuries after siltation of Khor Al Balid, possibly with the help of dredging. An extreme overwash event was recorded in almost all cores across both sampling sites, suggesting that a very large cyclone or a tsunami hit the southern Oman coast sometime around the 18th–19th century CE. This event, as well as continuous coastal sand accumulation, may have contributed to the decline and abandonment of Khor Al Balid and highlights the impacts that large storm/wave events have on archaeological site preservation.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140543618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatio-temporal patterns of intense tropical cyclones in the Western North Pacific over the past 1600 years","authors":"Liang Zhou ,&nbsp;Rumeng Hao ,&nbsp;Mingchen Li ,&nbsp;Yan Su ,&nbsp;Shu Gao ,&nbsp;Yang Yang ,&nbsp;Zhixiong Shen ,&nbsp;Jianjun Jia ,&nbsp;YaPing Wang","doi":"10.1016/j.margeo.2024.107283","DOIUrl":"https://doi.org/10.1016/j.margeo.2024.107283","url":null,"abstract":"<div><p>There are concerns that intense tropical cyclones (TCs) are expected to become more frequent and powerful in warming climates. However, the long-term trend of TC activities, the spatiotemporal variability of such trends across different latitudes of the Western North Pacific (WNP), and the drives of the variability remain unclear. Here, we present a reconstruction of a 1600-year paleo-TCs activity using a sediment core taken in Li’an Lagoon located in southeastern Hainan Island, South China Sea. We used muti-dating methods (²¹⁰Pb and AMS ¹⁴C dating) for age control and muti-proxy analysis (XRF geochemical element scanning and grain size analysis) for identifying periods of frequent intense TC activities. Based on an updated compilation of basin-wide paleo-TC records, we confirm that there exists a seesaw pattern of intense TC frequency between low and middle latitude in the WNP. Comparing with global and regional paleoclimate proxies, we propose that the basin-wide latitudinal TC activity variation in the WNP can be linked to the migration of Western Pacific Subtropical High (WPSH) and its associated high-latitude forcings (e.g., NAO) and low-latitude internal variability forcings (i.e., El Niño Southern Oscillation, sea surface temperature (SST)). More intense TC will occur at low latitudes in the future, though with less frequency.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140551154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Suspended particulate matter dynamics at the interface between an estuary and its adjacent coastal sea: Unravelling the impact of tides, waves and river discharge from 2015 to 2022 in situ high-frequency observations","authors":"Romaric Verney ,&nbsp;David Le Berre ,&nbsp;Michel Repecaud ,&nbsp;Alan Bocher ,&nbsp;Tanguy Bescond ,&nbsp;Coline Poppeschi ,&nbsp;Florent Grasso","doi":"10.1016/j.margeo.2024.107281","DOIUrl":"https://doi.org/10.1016/j.margeo.2024.107281","url":null,"abstract":"<div><p>Suspended particulate matter (SPM) dynamics and exchange fluxes at the interface between a macrotidal estuary and its adjacent coastal sea were investigated from long-term high-frequency in situ observations. Optical and acoustic measurements were coupled to calculate SPM concentration over the whole water column using an existing acoustic inversion algorithm. A method was developed to distribute over the water column the surface and bottom calibrated equivalent particle diameters based on complementary ship-based surveys. Surface and bottom SPM show similar patterns in response to main forcings (tide, river discharge and waves), but present significantly higher concentrations near the bed. Increasing tidal ranges were responsible for higher tidal-median SPM concentrations, with spring/neap SPMC ratio varying from 2 to 3. This increase is driven by local resuspension during flood phase at the bottom, and low salinity turbid water flushed out from the estuary from mid-ebb to low tide at the surface. Increasing river discharge implies a downward shift of the estuarine turbidity maximum from the inner estuary to the mouth, and yields a 2-fold increase in both surface and bottom tidal-median concentration. Waves generated strong resuspension, with the highest SPM concentration recorded both at the surface and near the bed. Analysing SPM residual fluxes highlighted large up-estuary fluxes from low to moderate tidal ranges (below 6 m), and exporting seaward fluxes for higher tidal ranges, due to stronger mixing during spring tides. High river discharge enhanced stratification at the mouth and strengthened density circulation and up-estuary residual bottom circulation, resulting in larger up-estuary fluxes for all tidal ranges. Larger SPM concentrations along the tidal cycle during wave events yield high exporting fluxes.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140546373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mangrove development on a remote volcanic island in the South Atlantic","authors":"José Tasso Felix Guimarães ,&nbsp;Gabriel Negreiros Salomão ,&nbsp;Prafulla Kumar Sahoo ,&nbsp;Márcio Sousa da Silva ,&nbsp;Wilson Nascimento Júnior ,&nbsp;Pedro Walfir Martins e Souza Neto ,&nbsp;Hortencia Maria Barbosa de Assis ,&nbsp;Luiza Santos Reis ,&nbsp;Ana Maria Góes ,&nbsp;Paulo César Giannini ,&nbsp;Rodolfo José Angulo ,&nbsp;Marcelo Rollnic ,&nbsp;Pedro Walfir Martins e Souza Filho","doi":"10.1016/j.margeo.2024.107280","DOIUrl":"https://doi.org/10.1016/j.margeo.2024.107280","url":null,"abstract":"<div><p>Sueste Bay, in the Fernando de Noronha archipelago (FNA), contains the only mangrove area among the oceanic islands of the South Atlantic. This work aims to reconstruct this mangrove's evolution during the Holocene based on a morphostratigraphic study integrated with palynological and multi-elemental geochemical data, temporally calibrated with radiocarbon dating. The data obtained indicated that, around 8000 to 7000 cal yr BP, well-developed <em>Rhizophora</em> and <em>Laguncularia</em> mangroves established over altered rocks of the Quixaba (phonolites, lamprophyres, basanites, trachyandesites and basalts) and Remédios (basanites, melilite and melanophelinites) Formation, under rising relative sea level, about 2 to 3 m below present. This period was the last record of <em>Rhizophora</em> in the FNA. From 6000 to 3600 cal yr BP, the lagoon system was eroded and significantly retrograded, under rising RSL during at least part of time, leaving clay pebbles scattered in the lower/upper shoreface deposit as the only record of its reworking. This process limited mud/mixed flats near the mouth of the Maceió River. Under a relative stability of RSL from 3600 cal yr BP to the present, a progradation of coastal facies, including beach/foredunes ridges, occurred and allowed the development of the modern lagoon system over swales between aeolian sand ridges. Mangroves were only observed during modern times but in environmental conditions very different from those of the previous occurrence. Indeed, <em>Laguncularia</em> coexists with several invasive plants within the narrow mixed flats associated with a small and almost filled tidal creek, whose siltation may be a product of the artificial damming of the Maceió River to supply public water to the archipelago. This study highlights the complex interactions between natural processes, sea-level changes, and human activities in shaping the coastal evolution of the Fernando de Noronha archipelago over the Holocene.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140344810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seismic investigation uncovers formation and spatial distribution of seafloor erosional features on the Changjiang (Yangtze) River subaqueous delta","authors":"Wei Feng,&nbsp;Shihao Liu,&nbsp;Weihua Li,&nbsp;Haifei Yang,&nbsp;Yufeng Chen,&nbsp;Ya Ping Wang","doi":"10.1016/j.margeo.2024.107268","DOIUrl":"https://doi.org/10.1016/j.margeo.2024.107268","url":null,"abstract":"<div><p>River deltas face erosional challenges driven by global changes and human activities leading to diminished sediment supply. Despite extensive researches on erosional processes within the Changjiang River subaqueous delta (CRSD), there exists a knowledge gap concerning the comprehensive spatial distribution of erosional features throughout the CRSD. This study addresses this gap by utilizing a substantial dataset of high-resolution chirp data to analyze the characteristics, distributions, and stratigraphic terminations of seafloor erosional features within the CRSD. The results unveil an expansive erosion area spanning approximately 2900 km², occurring at depths ranging from 10 to 40 m in the modern CRSD. These erosional features manifest as extensive truncations, low-relief scoured seafloor, and cut-and-fill structures, distributed variably across the CRSD. Particularly noteworthy is the identification of an alignment between the suspended sediment front and a 20 m water depth erosional area along the deltaic coast. Erosion in this area is dominated by truncations, extending ∼ 10 km in width, and followed by scoured (several hundred meters wide and ∼ 1–2 m deep on average) seafloor. Slope gradient also influences erosion, with cut-and-fill structures (2 km wide and around 5 m deep) that we attribute to sediment gravity flows are identified on steeper slopes offshore of North Channel. Beyond the 20 m water depth, extensive truncations spanning approximately 20 km wide and lead to outcrops of older strata. The spatial distribution of erosional features, coupled with river outlets and subsurface structure, suggests joint influences from reduced riverine sediments, estuarine engineering, wave actions, and tidal regimes. These findings emphasize the primary impact of sediment discharge reduction and underscore the collective influence of various anthropological and natural factors in shaping the spatial distribution of erosional features across different water depths in the subaqueous delta. Insights from this study contribute to a deep understanding of erosional processes and the ongoing evolution of erosional degradation in deltaic systems worldwide.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140180065","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A tale of a changing basin - a transient model of the 7.17 event leading to the Messinian Salinity Crisis","authors":"Ronja M. Ebner ,&nbsp;Francesca Bulian ,&nbsp;Francisco J. Sierro ,&nbsp;Tanja J. Kouwenhoven ,&nbsp;Paul Th. Meijer","doi":"10.1016/j.margeo.2024.107270","DOIUrl":"https://doi.org/10.1016/j.margeo.2024.107270","url":null,"abstract":"<div><p>Before the Messinian Salinity Crisis (MSC) left its imprint on the sediment record of the Mediterranean Sea in the form of evaporites, the basin had already undergone significant changes. At 7.17 Ma, a drop in δ13C values, as well as a basin-wide shift in the abundance of benthic foraminifers, already attest to a sudden change in the Mediterranean conditions.</p><p>This event coincides with an increase in the amplitude of the insolation curve. It thus stands to question whether a change in the freshwater budget or a change in the connection between the Mediterranean Sea and the Atlantic was the driver for this event. Answering this question would not only help to understand the event itself, but might also help to decipher the early dynamics of the MSC.</p><p>With a computational box model, we investigate the response of the Mediterranean Sea to a varying freshwater budget for a wide range of restriction. The results then let us define scenarios in which we analyse how a gradually changing restriction would express itself in the basin dynamics.</p><p>We find that the change in the freshwater budget alone cannot explain the changes that are attributed with the 7.2 event, but coupled with an increase in restriction most differences can be accounted for. Our results also show that a gradual change in restriction can provoke a non-linear response in the behaviour of the basin, which can appear abrupt when happening on a short enough timescale. Such a change would also enhance the influence of said changes in the freshwater budget.</p><p>This tells us that the processes that most likely triggered the Messinian Salinity Crisis started much earlier and incrementally increased the restriction of the Mediterranean Sea.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0025322724000549/pdfft?md5=ec873d6ba1f5d191d6f6d43119e0e64e&pid=1-s2.0-S0025322724000549-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140180379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multiproxy approach to characterize the sedimentary process of Cape Darnley Bottom Water flow through the Wild Canyon, East Antarctica","authors":"Keiko Takehara ,&nbsp;Minoru Ikehara ,&nbsp;Go-Ichiro Uramoto ,&nbsp;Naohisa Nishida ,&nbsp;Takayuki Omori ,&nbsp;Atsuko Amano ,&nbsp;Yusuke Suganuma ,&nbsp;Takuya Itaki","doi":"10.1016/j.margeo.2024.107269","DOIUrl":"10.1016/j.margeo.2024.107269","url":null,"abstract":"<div><p>To reconstruct the interaction between Antarctic Bottom Water (AABW) and global climate change, extracting information about past AABW formation from the sedimentary record is crucial. The Prydz Bay region, East Antarctica, has high glacier outflow and is a region of vigorous formation of AABW associated with sea ice formation. The Cape Darnley Bottom Water (CDBW), a primary AABW precursor, flows into Wild Canyon west of Prydz Bay. Thus, the sedimentary record of Wild Canyon can serve as an archive for CDBW flow. In this study, to identify the sedimentary processes and mineral compositions characteristic of CDBW flow, we evaluate deep-sea camera imagery, X-ray computed tomography images, grain-size data, and optical and chemical mineralogical analyses. Heavy minerals in the surface sediments are characterized by pyrope-rich almandine garnets (up to 80% of the heavy-mineral assemblage, 0.2%–3.7% of the dry bulk sediment by weight) typical of nearshore sediment derived from Mac. Robertson Land. In addition, ripples on the channel floor indicate sediment transport occurred as tractional bedload, whereas settling of suspended sediment prevailed on the canyon levee. We propose that modern CDBW flow is the dominant process of sediment reworking through sustained high flow velocities, distinctly different from turbidity currents triggered by ice sheet expansion and rapid retreat. Our results further suggest that fine-grained sediments are transported to the canyon levee as CDBW flows through the submarine canyon. These findings will be a key for reconstructing past AABW formation, which is crucial for understanding the response of AABW to future climate change.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140182125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Computed Laminography for the study of biogenic structures in sediment cores: A step between two- and three-dimensional imaging","authors":"Javier Dorador ,&nbsp;Francisco J. Rodríguez-Tovar ,&nbsp;Miros S.J. Charidemou ,&nbsp;Olmo Miguez-Salas","doi":"10.1016/j.margeo.2024.107267","DOIUrl":"10.1016/j.margeo.2024.107267","url":null,"abstract":"<div><p>The study of trace fossils —ecological indicators of environmental parameters such as organic-matter content, oxygenation or sedimentation rate, among others— is a powerful tool for analysing cores from deep-sea sediment. However, the visualization of biogenic structures in soft sediment cores is commonly poor. This problem has usually been solved by using X-ray radiographs from core slabs, and later by non-destructive Computed Tomography (CT). Yet the latter requires complex processing and computer resources to deal with a vast dataset. Computed Laminography (CL) stands as an alternative, non-destructive technique able to manage a small amount of data, providing results similar to X-ray radiographs. This technique is frequently used in other disciplines (e.g. material sciences), but rarely applied in geosciences. In the present study, we explore the usefulness of CL for studying the ichnological content of modern deep-sea deposits from boxcores collected from the Porcupine Abyssal Plain (NE Atlantic). Additionally, we compare results from Linear CL (LCL) and Circumferential CL (CCL) to discuss which is recommended depending on the goal involved. The obtained results confirm the usefulness of CL for the ichnological analysis of sediment cores, with similar results from LCL and CCL. However, recommendations are made to resolve doubtful scenarios and to save time. In light of our findings, the use of CL as a non-destructive technique, calling for a much smaller dataset than CT, can be highly recommended for the study of ichnological content or other internal structures.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0025322724000513/pdfft?md5=216ab7782fb54517eee4a3b07681c15e&pid=1-s2.0-S0025322724000513-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140117078","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatiotemporal variability of suspended sediment concentration in the coastal waters of Yellow River Delta: Driving mechanism and geomorphic implications","authors":"Hongyu Ji ,&nbsp;Shenliang Chen ,&nbsp;Peng Li ,&nbsp;Shunqi Pan ,&nbsp;Xuelei Gong ,&nbsp;Chao Jiang","doi":"10.1016/j.margeo.2024.107266","DOIUrl":"10.1016/j.margeo.2024.107266","url":null,"abstract":"<div><p>Satellite images have revealed a significant decline in the suspended sediment concentration (SSC) near surface in the coastal waters of Yellow River Delta (YRD) in recent years. However, there is limited information on the spatial disparity in SSC distributions and its dynamic mechanism. In this study, we utilize a well-calibrated SSC retrieval algorithm and a depth-averaged numerical modeling approach to investigate the delta and sub-delta scale variation trends and driving mechanisms of SSC in the coastal waters of YRD over the past few decades. The results of this study demonstrate the existence of high turbidity zones in coastal waters of the northern abandoned delta and the active lobe of the YRD. These zones have experienced general decreasing trends of SSC at the interannual timescale. Additionally, the distribution of SSC is significantly higher in dry seasons compared to that in wet seasons. The magnitude and varying trends of SSC are strongly influenced by the total bottom shear stress (BSS) caused by combined effects of waves and currents, although the wave-induced BSS is found to be less significant that the current-induced one, but vary more significantly due to wind forcing in the Bohai Sea. Furthermore, the grain size of seabed sediments plays a dominant role in the sediment mobilization and resuspension processes over interannual and longer timescales. The distribution of high BSS and sediment mobility zones align with the active areas for morphological changes with the YRD exhibiting net accretion in the active river mouth and erosion in the abandoned delta lobes. These findings highlight the multiscale variations and the close relationship between SSC and BSS, providing valuable insights into sediment dynamics with geomorphic evolution in highly human-interfered deltaic systems.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140117554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Safi boulders (Morocco): Evidence of past extreme wave events","authors":"Otmane Khalfaoui ,&nbsp;Imane Joudar ,&nbsp;Nouhaila Erraji Chahid ,&nbsp;Khalid El Khalidi ,&nbsp;Abdenaim Minoubi ,&nbsp;Mohammed Bouchkara ,&nbsp;Bendahhou Zourarah","doi":"10.1016/j.margeo.2024.107265","DOIUrl":"10.1016/j.margeo.2024.107265","url":null,"abstract":"<div><p>Tsunamis and storm surges are among several hazards threatening the Atlantic coast of Morocco. During the last two decades, sedimentological deposits left by these events, in the form of fine-grained sediments (washover) and boulders, have been studied along the Moroccan shores to determine the return period of these events and how they fluctuate in terms of intensity. The present work investigates two new boulder fields located along the Safi coast. Field surveys were accomplished in the two areas to collect the position/elevation and dimensions of 164 boulders using a GPS/DGPS and a traditional meter, respectively. The field data was combined with hydrodynamic equations to estimate the minimum velocity and storm/tsunami wave height to move the measured boulders. In site 1, the boulders are situated on a rocky intertidal platform, while in the second, they are on the top of a cliff. For both sites, the size of the boulders ranges from 0.6 to 5.60 m, 0.54 to 3.6 m, and 0.27 to 1.5 m on the major (a), medium (b), and minor (c) axes, respectively. They reach a volume of up to 25.20 m³ and a weight of 55.44 t. The maximum distance and elevation recorded are around 41.77 m and 13 m, respectively. According to hydrodynamic equations, the coastal platform boulders (site 1) can be moved by tsunami waves with heights between 0.10 and 0.59 m, and storm waves from 0.42 to 2.37 m. To be displaced, the cliff-top boulders (site 2) need tsunami and storm waves with at least 5.91 and 8.64 m, respectively. The results from the field surveys and hydrodynamic equations suggest that both tsunami and storm waves can move the boulders in site 1. For the cliff top-boulders, the data favours tsunamis as a source for this deposit.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-03-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140117074","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}