Marine Geology最新文献

{"title":"Depositional model of the Holocene coquinas - Albardão platform, southern Brazil","authors":"Paul Michael Nii Anang Okoe ,&nbsp;Elírio Ernestino Toldo Júnior ,&nbsp;Cristiano Fick ,&nbsp;Eduardo Puhl ,&nbsp;Maria Luiza Correa da Camara Rosa ,&nbsp;José Carlos Rodrigues Nunes ,&nbsp;Francisco Eduardo G. Cruz ,&nbsp;Vinicius Carbone B. de Oliveira","doi":"10.1016/j.margeo.2024.107346","DOIUrl":"https://doi.org/10.1016/j.margeo.2024.107346","url":null,"abstract":"<div><p>For the past decade, giant deepwater oil discoveries in the pre-salt section of the Campos and Santos basins of Brazil, have brought significant attention to offshore exploration activities along the South Atlantic margins. The prolific Cretaceous coquina deposits in these basins are part of the pre-salt rock record and constitute an effective but complex and heterogeneous hydrocarbon reservoir difficult to predict and model. Parting from this context, an evaluation of the sedimentological, structural and taphonomic criteria for coquinas are essential to better understand and predict the facies distribution and depositional models of the pre-salt coquinas strata. Based on this premise, the present work aims to genetically interpret 133 mixed carbonate-siliciclastic bottom sediments of the Albardão shelf – a modern marine coquina analogue, using facies description, investigating the relationship with hydrodynamic forces, and accessing the influence of morphology and structural framework on their deposition. From these analyses, we recognized a hybrid facies, three modern carbonate facies in analogy to the carbonate rock classification and four siliciclastic facies. These eight facies were then grouped into three facies associations representing high, moderate, and low energy facies. The high energy facies association comprises rudstones (Rf) and grainstones (Gf) with highly fragmented bivalve shells and barnacles abundantly present in the beach system, above the fair-weather wave base limit (FWWB). These facies also occur offshore on bathymetric highs above the storm wave base limit (SWB) but display less reworking than the coastal high energy facies above the FWWB due to wave shoaling. The moderate energy facies association consists of hybrid sand (Hs), sand (S) and muddy sand (mS) occurring between the FWWB and SWB limits in the offshore transition zone with extensive winnowing action and low rate of reworking. The low energy facies association includes sandy mud (sM), mud (M) and micritic mud (Mc), characterized by the decantation of the fine sediments below the offshore SWB limit. The results confirm a bottom facies distribution controlled by depth, shelf profile morphology and energy from incident waves. The fragmented rudstone and fragmented grainstone facies are the best-recognized reservoirs with both having high porosity and high permeability.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141540837","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":"Magmatism along the Nansha Trough on the southern continental margin of the South China Sea: Recent evidence from along-strike seismic profile","authors":"Chufeng Guo ,&nbsp;Yong Tang ,&nbsp;Yinxia Fang ,&nbsp;Chunyang Wang ,&nbsp;Xiaodong Wei ,&nbsp;He Li ,&nbsp;Peng Chao ,&nbsp;Tianyi Yang ,&nbsp;Zhibin Song ,&nbsp;Jianye Ren ,&nbsp;Jiabiao Li","doi":"10.1016/j.margeo.2024.107344","DOIUrl":"https://doi.org/10.1016/j.margeo.2024.107344","url":null,"abstract":"<div><p>The Nansha Trough (NT) is part of the southern continental margin boundary of the South China Sea (SCS). It has undergone complex tectonic superposition and evolutionary processes involving the subduction demise of the Proto-SCS and subsequent spreading of the SCS. This study provides the first systematic identification and analysis of igneous bodies and seamounts along the NT, based on a multi-channel seismic profile (NDL1) recently acquired along it. The seamounts within the trough are of magmatic origin and the carbonate build-ups observed at the summits of some seamounts exhibit a substantial thickness. Igneous bodies within the trough are consistently associated with high P-wave anomalies. Furthermore, at the eastern and western sides, there are distinct gravity-magnetic-anomaly patterns. On the eastern side, Yinqing Seamount, Nanle Hill and volcanic mounds show high gravity and strong negative magnetic anomalies. In contrast, on the western side, Jinghong Seamount, Yangshu Hill and intrusive bodies show less pronounced magnetic anomalies. This difference may be related to differences in magmatic periods. Unlike the extensive post-spreading magmatism in the SCS's northern margin and deep basin, the most widespread magmatic activity in the NT occurred at ca. 16 Ma before decreasing during the Miocene. This decrease may be closely related to subduction cessation in the Proto-SCS and the collision between the Nansha Block and Borneo. The identification and analysis of NT igneous bodies and their evolutionary processes help delineate the southern boundary of magmatism at the SCS margin. They also provide crucial information for constraining the magmatic processes of Proto-SCS subduction termination and SCS spreading evolution.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141540836","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":"Insights on gas hydrate formation and growth within an interbedded sand reservoir from well logging at the Qiongdongnan basin, South China Sea","authors":"","doi":"10.1016/j.margeo.2024.107343","DOIUrl":"10.1016/j.margeo.2024.107343","url":null,"abstract":"<div><p>Although variable well log resolution and its control on saturation estimation has been studied, it has not been directly applied to a specific location to explore the nature of gas hydrate within a sand reservoir. We applied in-situ measurements of resistivities, neutron porosity, and gamma ray at two sites in the Qiongdongnan Basin, South China Sea (QDN-W05–2021 and QDN-W08–2021) to investigate the reservoir parameters of a hydrate-bearing sand reservoir. Our results show that gas hydrate is distributed in 5 zones with a total thickness of 10.7 m and an average saturation of 69% at the QDN-W05–2021 site, while they are distributed in 2 zones with a total thickness of 4.3 m and an average saturation of 49% at the QDN-W08–2021 site. We found that variances in saturations estimated from lateral-extra deep button (RX), phase shift (P40H-P40L), and attenuation (A40H-A40L) resistivities within the laterally mapped continuous sand body were affected by the nature of gas hydrate occurrences. Results indicate gas hydrate forms and accumulates at the center of the sand layer and tends to be less or not present toward the top and base. Integrated with seismic data, the in-situ measurements provide insights in the evolution of a mushroom-shaped, hydrate-gas reservoir system. In the system, free gas is likely horizontally transported from the top-center of the gas chimney to the surrounding areas in the early stage dominated by a warm-gas environment, whereas hydrate forms in the opposite pathway starting from the surrounding areas in the following stage with temperature reducing. Our study suggests that high-resolution in-situ measurements not only are a tool to identify the physical properties, but also can be used to help explain the physical process of hydrate growth and accumulation.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141944204","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":"Submarine volcanism in the Sicilian Channel revisited","authors":"Aaron Micallef ,&nbsp;Jörg Geldmacher ,&nbsp;Sebastian F.L. Watt ,&nbsp;Giulia Matilde Ferrante ,&nbsp;Jonathan Ford ,&nbsp;Emanuele Lodolo ,&nbsp;Dario Civile ,&nbsp;Alastair G.E. Hodgetts ,&nbsp;Meret Felgendreher ,&nbsp;Jacqueline Grech Licari ,&nbsp;Folkmar Hauff ,&nbsp;Silke Hauff ,&nbsp;Jakob Lang ,&nbsp;Kerys Meredew ,&nbsp;Maxim Portnyagin ,&nbsp;Christian Timm ,&nbsp;Christian Berndt ,&nbsp;Danilo Cavallaro ,&nbsp;Filippo Muccini ,&nbsp;Kaj Hoernle","doi":"10.1016/j.margeo.2024.107342","DOIUrl":"https://doi.org/10.1016/j.margeo.2024.107342","url":null,"abstract":"<div><p>The origin and role of volcanism in continental rifts remains poorly understood in comparison to other volcano-tectonic settings. The Sicilian Channel (central Mediterranean Sea) is largely floored by continental crust and represents an area affected by pronounced crustal extension and strike-slip tectonism. It hosts a variety of volcanic landforms closely associated with faults, which can be used to better understand the nature and distribution of rift-related volcanism. A paucity of appropriate seafloor data in the Sicilian Channel has led to uncertainties regarding the location, volume, sources and timing of submarine volcanism. To improve on this situation, we use newly acquired geophysical data (multibeam echosounder and magnetic data, sub-bottom profiles) and dredged seafloor samples to: (i) re-assess the evidence for submarine volcanism in the Sicilian Channel and define its spatial pattern, (ii) infer the relative age and style of magmatism, and (iii) relate this to the dominant tectonic structures in the region. Quaternary rift-related volcanism has been focused at Pantelleria and Linosa, at the northwest boundaries of their respective NW-SE trending grabens. Subsidiary and older volcanic sites potentially occur at the Linosa III and Pantelleria SE seamounts, collectively representing the only sites of recent volcanism that can be directly related to the main rift process. These long-lived polygenetic volcanic landforms have been shaped by magmatism that is directly correlated with extensional faulting and buried igneous bodies. Older volcanic landforms, sharing a similar scale and alignment, occur to the north at Nameless Bank and Adventure Bank. These deeply eroded volcanoes have likely been inactive since the Pliocene and are probably related to earlier stages of crustal thinning and underlying feeder structures in the northern region of the Sicilian Channel. Along a similar alignment, Pinne Bank, SE Pinne Bank and Cimotoe in the northern Sicilian Channel lack a surface volcanic signature but are associated with intrusive bodies or deeply buried volcanic rock masses. Terrible Bank, in the same region, also shows evidence of ancient, polygenetic magmatism, but was subject to significant erosion and lacks a prominent alignment. The much younger volcanism at Graham Volcanic Field and along the northern Capo-Granitola-Sciacca Fault Zone differs markedly from that observed in the other study areas. Here, the low-volume and scattered volcanic activity is driven by shallow-water mafic magma eruptions, which gave rise to small individual cones. These sites are associated with large fault structures away from the main rift axis and may have a distinct magmatic origin. Dispersed active fluid venting occurs across both ancient and young volcanic sites in the region and is directly associated with shallow magmatic bodies within tectonically-controlled basins. Our study provides the foundation for an updated tectonic and magmatic framework","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141438709","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":"Dynamic behaviors of suspended sediment and chlorophyll-a in intertidal flats under episodic meteorological events","authors":"Hun Jun Ha ,&nbsp;Jong Seong Khim ,&nbsp;Ho Kyung Ha","doi":"10.1016/j.margeo.2024.107341","DOIUrl":"https://doi.org/10.1016/j.margeo.2024.107341","url":null,"abstract":"<div><p>Intertidal flats are important shallow-water habitats and buffers against coastal erosion. Strong, short-lasting meteorological events, such as storms and rainfall, are the main mechanisms of transporting (in)organic materials and sediments. Two <em>in-situ</em> mooring systems were installed simultaneously in the tidal channel and mudflat of Jeungdo, Korea, to understand the dynamic behaviors of suspended sediment and chlorophyll-<em>a</em> (chl-<em>a</em>) under the episodic events. During fair-weather periods with a distinct tidal cycle, the sediment in the mudflat was resuspended during the flood and then advected to the tidal channel during the ebb. The maximum suspended sediment concentration (SSC) and chl-<em>a</em> under storm event were approximately 9 and 2 times higher than those under fair-weather periods, respectively. Under rainfall event, the maxima were approximately 7 and 1.2 times higher than fair-weather, suggesting that sediment and microphytobenthos were highest resuspended by the meteorological events. In addition, a time lag (∼ 1.5 h) between SSC and chl-<em>a</em> occurred in the tidal channel during ebb tide with a rainfall event. During the post-rainfall periods, the SSC and chl-<em>a</em> increased, showing a positive relationship with the bed shear stress, suggesting that the rainfall event could reduce sediment stabilization.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141483516","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":"Identification of the Storegga event offshore Shetland","authors":"Jane L. Earland ,&nbsp;James D. Scourse ,&nbsp;Tobias Ehmen ,&nbsp;Sev Kender ,&nbsp;Philippa Ascough","doi":"10.1016/j.margeo.2024.107334","DOIUrl":"https://doi.org/10.1016/j.margeo.2024.107334","url":null,"abstract":"<div><p>The Shetland Islands (UK) are a seminal location for investigating palaeo-tsunami deposits. Onshore evidence suggests three tsunami have occurred during the Holocene: the Storegga tsunami ca. 8150 cal yr BP, the Garth tsunami ca. 5500 cal yr BP and the Dury Voe tsunami ca. 1500 cal yr BP. However, little research has been published on the impact of tsunami on the subtidal shelf where a large amount of North Sea hydrocarbon infrastructure is located. Here, we test the hypothesis that Holocene tsunami impacted shelf sediments, using radiocarbon dating and sedimentological characterization of cores recovered from the Fetlar Basin, offshore east Shetland. The cores contain distinct sand and shell lenses within a Holocene mud sequence, indicating a sudden change in hydrodynamic conditions. Radiocarbon dates bracketing the sand lenses overlap with the published dates for the Storegga event. Dates within the deposit are older (&gt;9 cal. yr BP) which is consistent with reworking and redeposition of earlier sediments. Particle size analysis, ITRAX and MSCL data evidence increases in mean grain size, a reduction in sorting capacity, increased shell concentrations and peaks in associated elements (log(Ca/Fe), log(Ca/Ti) and Sr). These attributes indicate transport of allochthonous material from the inner shelf, and are typical of tsunami backwash-generated submarine debris flows. No evidence was found within the cores for any later Holocene tsunami, which may be due to either bioturbation, active currents, or lack of an initial deposit. The disturbance of sediments, and generation of a submarine debris flow within the Fetlar Basin by the Storegga event highlights the need to assess the potential impact of any future tsunami on planned and existing infrastructure at seabed. Erosion and deposition of allochthonous older marine sediment by the Storegga event also has consequence for interpretation of the coeval 8.2 ka cold event in marine sedimentary records in the tsunami affected region.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S002532272400118X/pdfft?md5=62b32dfbb3a0bdd376af8b7d217a6d3b&pid=1-s2.0-S002532272400118X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141483517","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":"Stratigraphic and paleoceanographic alternations within a Mediterranean semi-enclosed, syn-rift basin during Marine Isotope Stage 5: The Gulf of Corinth, Greece","authors":"Spyros Sergiou ,&nbsp;Maria Geraga ,&nbsp;Sofia Pechlivanidou ,&nbsp;Robert L. Gawthorpe ,&nbsp;Ulysses Ninnemann ,&nbsp;Anna-Nele Meckler ,&nbsp;Sevasti Modestou ,&nbsp;Dimitra Angelopoulou ,&nbsp;Dimitra Antoniou ,&nbsp;Paula Diz ,&nbsp;Lisa McNeill ,&nbsp;Donna J. Shillington ,&nbsp;George Papatheodorou","doi":"10.1016/j.margeo.2024.107340","DOIUrl":"https://doi.org/10.1016/j.margeo.2024.107340","url":null,"abstract":"<div><p>The Gulf of Corinth represents an ideal setting for studying the impact of sea level changes and regional climate on a semi-enclosed, <em>syn</em>-rift basin. Here we investigate the stratigraphic and paleoceanographic variability recorded in the sedimentary succession of the basin over the Marine Isotope Stage (MIS) 5 period when global sea level and climatic conditions along the eastern Mediterranean exhibited pronounced fluctuations. We used sedimentological (granulometry, composition), micropaleontological (planktic and benthic foraminifera), and isotopic (stable δ¹⁸O, δ¹³C, and clumped isotope) proxies on core samples from site M0079A (IODP Expedition 381) combined with additional data from the expedition overview and records from the surrounding area. The sedimentary succession comprises an alternating pattern of a) bioturbated, biogenic-rich deposits associated with increased hemipelagic sedimentation with b) partly bedded, detrital-rich sediments attributed to intercalated sediment gravity flows within the hemipelagic background under low oxic sea-surface conditions, and c) aragonite-rich laminated deposits, indicating either transitional conditions between marine and isolated environment or a highly stratified seawater column and low oxygen seafloor conditions. We find that the Gulf of Corinth lay under marine conditions for nearly the entire MIS 5 period, while the Rion sill would have been possibly shallower, even 10 m, than the current depth. Nevertheless, water exchange was restricted during the MIS 5a – MIS 4 transition when the sea level fluctuated very close to the sill height. The hydrological conditions within the Gulf during most of the highstands MIS 5a, 5c, and 5e reflect higher oxygen levels and/or increased nutrient availability compared to the Holocene and present-day regime. The combined effects of Ionian Sea inflows and enhanced riverine runoff led to increased water column stratification and low oxygen, eutrophic seafloor conditions in the Gulf of Corinth during times of high precipitation in southern Europe and deposition of sapropels S3, S4, and S5 throughout the eastern Mediterranean. In contrast, during periods of widespread cold and arid conditions in the eastern Mediterranean, water column mixing was intense within the Gulf. Prevalent marine conditions are also proposed during the MIS 5b and 5d lowstands, yet associated with predominately bedded-detrital sediments in the Gulf. A complementary investigation in the adjoining Patras Gulf is suggested to fully comprehend the dynamics of climate and sea level changes in complex rift systems.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141422983","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":"An improved method for semi-automated identification of submarine canyons and sea channels using digital bathymetric analysis","authors":"Shenghao Shi,&nbsp;Murray Richardson","doi":"10.1016/j.margeo.2024.107339","DOIUrl":"10.1016/j.margeo.2024.107339","url":null,"abstract":"<div><p>Submarine canyons are the key structures of the transitional area between the deep ocean floor and continental shelf known as the continental slope. They are important submarine features with high ecological, economic, and scientific value. With continual improvements to global and regional marine bathymetry products, digital bathymetric analysis (DBA) techniques must evolve to support ongoing marine geological research and to advance international bathymetric feature catalogs and mapping products. This study aims to further advance the delineation of submarine canyons and associated sea channels using DBA and the recent open-access GEBCO_2019 global bathymetry grid with 15 arc-second resolution, for a small study region in the southern Celtic Sea. A modified semi-automated delineation method is presented based on combining hydrological network analysis and the topographic position index (TPI), a commonly used parameter available in conventional digital terrain analysis toolsets. For the case-study area of interest, 96 submarine canyons were identified, with higher morphological detail than the previous ETOPO1 and SRTM30_PLUS based studies, which identified 81 and 52 submarine canyons, respectively for the same area of interest. The improvements include an increased number of vertices and limbs per canyon, increased positional precision for canyon starting points and endpoints, and the ability to identify associated sea channels. The results also highlight the importance of pre-processing and parameter localization to effectively exploit higher-resolution bathymetric data, which should also improve scale adaptability for application in different types of continental margins and with high-resolution bathymetry products. Future studies will benefit from the TPI-based identification process proposed in this study to identify submarine canyons and channels on other continental slopes, and to delineate different types of linear depressions from high-resolution digital bathymetry.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0025322724001233/pdfft?md5=f28929c05b8cb18122452a1cf0730616&pid=1-s2.0-S0025322724001233-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141394868","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":"Sedimentary record of water-sediment regulation and channel shifts in the Yellow River (Huanghe) Delta","authors":"Shuqing Qiao ,&nbsp;Xuefa Shi ,&nbsp;Jianbu Wang ,&nbsp;Lin Zhou ,&nbsp;Yonggui Yu ,&nbsp;Naishuang Bi ,&nbsp;Limin Hu ,&nbsp;Gang Yang ,&nbsp;Zhengquan Yao","doi":"10.1016/j.margeo.2024.107338","DOIUrl":"https://doi.org/10.1016/j.margeo.2024.107338","url":null,"abstract":"<div><p>Delta are vital habitats for people and biotic communities. Many of the world's large river deltas are shrinking because of relative sea level rise and intensifying human interventions in the basin. Among these, the Yellow River Delta (hereafter YRD) has been enormously impacted by frequent channel avulsions and a Water-Sediment Regulation Scheme (WSRS) through upstream reservoirs since 2002. However, it remains undisclosed how the YRD responses to these human interventions. Here, modern sedimentation and inter-annual to multi-decadal timescales evolution of the YRD were studied using a dataset including 10 sediment cores collected in the subaqueous delta during the 2014 WSRS, satellite images, hydrographic and bathymetric data from 1976 to 2014. Our results show that the sedimentation of the delta can be divided into three stages: 1976–1995, 1996–2001, and 2002–2014. The area of subaerial delta generally increased from 3884 km² to 4441 km² during the whole 1976–2014 period except for a net land loss during 1996–2000. &gt;70% of the delta coastline became artificial after 2000. Bathymetric data reveals that the subaqueous delta was seriously eroded after 1996 due to a shortage of sediment supply, with an estimated 2.3 × 10⁸ t/yr and 1.1 × 10⁸ t/yr of sediment respectively transported to the delta's adjacent sea during 1996–2001 and 2002–2014. The deltaic sediment became coarser due to the impact of the WSRS. Radionuclide ⁷Be uncovers a rapid sediment accumulation of ∼12 cm at the active delta front during the 2014 WSRS. The evolution of the YRD has become complex under the influence of natural and anthropogenic factors. The YRD thus provides an exemplar shift from natural to human-dominated delta. These results are important for the delta management decision making.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141325188","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":"An exceptional record of soft-sediment deformation within Pliocene deposits of Faro Drift (SW Iberia margin) - IODP Expedition 339 Sites U1386 and U1387","authors":"Cristina Roque ,&nbsp;Davide Gamboa ,&nbsp;Filipe M. Rosas ,&nbsp;Naohisa Nishida ,&nbsp;Débora Duarte ,&nbsp;Emmanuelle Ducassou","doi":"10.1016/j.margeo.2024.107335","DOIUrl":"10.1016/j.margeo.2024.107335","url":null,"abstract":"<div><p>The occurrence of soft-sediment deformation structures (SSDS) have long been recognized in several types of sedimentary environments and deposits. However, their presence in contourite drift deposits is still unreported in the literature. In this work, we present the first detailed description of SSDS found within the Pliocene sedimentary record of the Faro Drift, recovered during the Integrated Ocean Drilling Program (IODP) Expedition 339. The Faro Drift is the largest contourite drift of the Contourite Drift Depositional System developed in the Gulf of Cadiz since the Late Miocene by the circulation of the Mediterranean Outflow Water. The SSDS were identified in archive-halves of core sections located between ∼458 and ∼ 510 m below seafloor (mbsf) (hole U1386C), and between ∼599 and ∼ 670 mbsf (hole U1387C). Their identification and characterization was made by visual core description, structural geometrical analysis in core-scan high-resolution images, and scanning electron microcopy (SEM) analysis in selected intervals. The SSDS were classified based on the exhibited geometry, structural configuration and respective kinematics. The main deformation process and potential trigger were inferred from the geometrical and kinematics analysis. We identified five categories of SSDS: i) microfaults (normal and thrust faults), ii) slump sheet (formed by several types of folds, such as eye-folds, fish-hook folds, spiral folds), iii) convolute bedding, iv) folds within debrite mudclasts', and v) sigmoidal-like structures. Although the first three are well known types of SSDS, the folds within debrite mudclasts' and sigmoid-like structures have been scarcely recognized and described at core-scale. The inferred deformation processes responsible for the formation of these SSDS were i) brittle deformation by hydrofracturing and compaction faulting (microfaults), ii) hydroplastic (ductile) deformation (slump folds, folds within debrite mudclasts'), iii) liquefaction (convolute bedding), iv) shearing by flow movement (sigmoid-like structures). The most probable triggering agents seem to have been overloading, downslope movement of slump sheet and debris flow, and shearing by currents.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141406412","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}