Pub Date : 2024-10-04DOI: 10.1016/j.margeo.2024.107408
In Hawaiʻi, tsunamis are often described in orally transmitted legends (moʻolelo). This study examines sedimentary evidence of a possible local submarine landslide-generated tsunami, described in a legend from the south east coast of Maui which originated between the 15th Century CE and the first arrival of Europeans in 1778 CE. Physical evidence for a tsunami, found at the Nu'u Refuge, Maui, is primarily comprised of an extensive coral clast deposit (found 8.5 m above msl and 251 m inland from the shoreline) together with waterworn cobbles which form fracture-embedded wedge clasts in a local basalt escarpment (at up to 8 m above msl). U/Th dating of the coral clasts gives a maximum tsunami deposit age of 1671 CE for the event that may have inspired the local moʻolelo. This depositional sequence is used to characterize the nature of the assumed tsunami in terms of inundation distance, maximum wave runup and minimum flow velocities. A numerical model developed using GeoClaw matches well with the physical evidence. The data and modeling presented here suggest that locally-generated tsunamis from submarine landslides warrant further research attention as sources of destructive high energy marine inundation events.
{"title":"Hawaiian legends of coastal devastation and paleotsunami reconstruction, Nu'u, Kaupō, Maui, Hawai'i","authors":"","doi":"10.1016/j.margeo.2024.107408","DOIUrl":"10.1016/j.margeo.2024.107408","url":null,"abstract":"<div><div>In Hawaiʻi, tsunamis are often described in orally transmitted legends (<em>moʻolelo</em>). This study examines sedimentary evidence of a possible local submarine landslide-generated tsunami, described in a legend from the south east coast of Maui which originated between the 15th Century CE and the first arrival of Europeans in 1778 CE. Physical evidence for a tsunami, found at the Nu'u Refuge, Maui, is primarily comprised of an extensive coral clast deposit (found 8.5 m above msl and 251 m inland from the shoreline) together with waterworn cobbles which form fracture-embedded wedge clasts in a local basalt escarpment (at up to 8 m above msl). U/Th dating of the coral clasts gives a maximum tsunami deposit age of 1671 CE for the event that may have inspired the local <em>moʻolelo</em>. This depositional sequence is used to characterize the nature of the assumed tsunami in terms of inundation distance, maximum wave runup and minimum flow velocities. A numerical model developed using GeoClaw matches well with the physical evidence. The data and modeling presented here suggest that locally-generated tsunamis from submarine landslides warrant further research attention as sources of destructive high energy marine inundation events.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423066","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}
Pub Date : 2024-09-30DOI: 10.1016/j.margeo.2024.107407
As the climate crisis intensifies, estimating sea-level rise will become increasingly relevant, in particular assessing changes in the relative sea level in different regions. One key to comprehending global sea-level changes is the study of past sea-level highstands. Many regional studies help refine the reconstruction of paleo sea levels globally. Thus far, the Middle East remains understudied.
This paper presents evidence for Quaternary sea-level variations along the shores of the western Indian Ocean. Eight coastal outcrops along the northern and eastern coasts of Oman are presented in detail. The sedimentological evidence for sea-level highstands varies within the study area. However, in relation to recent sea-level conditions, all of these marine and beach deposits are now found well above the environments where such formations would typically form. Dating the timing of sea-level highstands remains a challenging task within the study area. In different studies, attempts to 14C date samples from that area were unsuccessful, as the time of sediment deposition lies beyond the dating limit of 14C, precluding a Holocene formation of these sediments. Thus, the sediments are regarded as deposits formed during Pleistocene sea-level highstands, presumably during MIS 5e. For some sections, optically stimulated luminescence dating could provide a solution, as igneous source rocks supply quartz and feldspar. This paper aims to localise eight sea-level related outcrops along the Omani coast and depict their potential for future work, which should include dating and elevation measurements. Through this, our work contributes to the ongoing effort to globally identify records of sea-level changes, as well as providing insights into the regional setting in Oman.
随着气候危机的加剧，估算海平面上升将变得越来越重要，特别是评估不同地区相对海平面的变化。理解全球海平面变化的关键之一是研究过去的海平面高点。许多区域研究有助于完善全球古海平面的重建。本文提供了西印度洋沿岸第四纪海平面变化的证据。本文详细介绍了阿曼北部和东部海岸的八个沿海露头。在研究区域内，海平面高地的沉积学证据各不相同。不过，就最近的海平面状况而言，所有这些海洋和海滩沉积物目前都远高于此类地层通常形成的环境。在研究区域内，海平面高地的时间测定仍然是一项具有挑战性的任务。在不同的研究中，对该地区样本进行 14C 测定的尝试都没有成功，因为沉积物沉积的时间超出了 14C 测定的极限，排除了这些沉积物形成于全新世的可能性。因此，这些沉积物被认为是在更新世海平面高位时期形成的沉积物，推测形成于 MIS 5e。对于某些地段，由于火成岩提供了石英和长石，因此光激发发光测年法可以提供一种解决方案。本文旨在确定阿曼沿海八个与海平面有关的露头的位置，并描绘其未来工作的潜力，其中应包括年代测定和海拔测量。通过这项工作，我们的工作将为目前正在全球范围内确定海平面变化记录的工作做出贡献，并为了解阿曼的区域环境提供见解。
{"title":"Sedimentological evidence of Late Pleistocene Shorelines in Oman","authors":"","doi":"10.1016/j.margeo.2024.107407","DOIUrl":"10.1016/j.margeo.2024.107407","url":null,"abstract":"<div><div>As the climate crisis intensifies, estimating sea-level rise will become increasingly relevant, in particular assessing changes in the relative sea level in different regions. One key to comprehending global sea-level changes is the study of past sea-level highstands. Many regional studies help refine the reconstruction of paleo sea levels globally. Thus far, the Middle East remains understudied.</div><div>This paper presents evidence for Quaternary sea-level variations along the shores of the western Indian Ocean. Eight coastal outcrops along the northern and eastern coasts of Oman are presented in detail. The sedimentological evidence for sea-level highstands varies within the study area. However, in relation to recent sea-level conditions, all of these marine and beach deposits are now found well above the environments where such formations would typically form. Dating the timing of sea-level highstands remains a challenging task within the study area. In different studies, attempts to <sup>14</sup>C date samples from that area were unsuccessful, as the time of sediment deposition lies beyond the dating limit of <sup>14</sup>C, precluding a Holocene formation of these sediments. Thus, the sediments are regarded as deposits formed during Pleistocene sea-level highstands, presumably during MIS 5e. For some sections, optically stimulated luminescence dating could provide a solution, as igneous source rocks supply quartz and feldspar. This paper aims to localise eight sea-level related outcrops along the Omani coast and depict their potential for future work, which should include dating and elevation measurements. Through this, our work contributes to the ongoing effort to globally identify records of sea-level changes, as well as providing insights into the regional setting in Oman.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423064","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}
Pub Date : 2024-09-26DOI: 10.1016/j.margeo.2024.107403
Mission-Specific Platforms (MSPs) have been important members of the scientific ocean drilling family for two decades, operating alongside their impressive siblings JOIDES Resolution and D/V Chikyu. Over this time, 10 MSP expeditions were implemented in 7 different oceans and seas. These MSPs capitalised on alternative platforms and methods, and enabled the scientific community to access new geographical areas and new geological targets that could not be drilled by the JOIDES Resolution or Chikyu. Offshore heave-compensated wireline coring, onshore-mining-style wireline coring, remote seafloor drilling and giant piston coring have all featured on MSP expeditions. Equally diverse were the environments in which these technologies were deployed, from the ice-covered Arctic Ocean to the tropical seas of the Great Barrier Reef, and from the shallow waters of the Yucatan shelf to the ultra-deep hadal depths of the Japan Trench. In this paper we reflect on the diverse technologies of MSPs, how they increased scientific ocean drilling capability in the Integrated Ocean Drilling Program (2003−2013) and International Ocean Discovery Program (2013–2024), and the scientific achievements that they enabled.
{"title":"Twenty years of MSPs: Technologies and Perspectives","authors":"","doi":"10.1016/j.margeo.2024.107403","DOIUrl":"10.1016/j.margeo.2024.107403","url":null,"abstract":"<div><div>Mission-Specific Platforms (MSPs) have been important members of the scientific ocean drilling family for two decades, operating alongside their impressive siblings <em>JOIDES Resolution</em> and <em>D/V Chikyu</em>. Over this time, 10 MSP expeditions were implemented in 7 different oceans and seas. These MSPs capitalised on alternative platforms and methods, and enabled the scientific community to access new geographical areas and new geological targets that could not be drilled by the <em>JOIDES Resolution</em> or <em>Chikyu</em>. Offshore heave-compensated wireline coring, onshore-mining-style wireline coring, remote seafloor drilling and giant piston coring have all featured on MSP expeditions. Equally diverse were the environments in which these technologies were deployed, from the ice-covered Arctic Ocean to the tropical seas of the Great Barrier Reef, and from the shallow waters of the Yucatan shelf to the ultra-deep hadal depths of the Japan Trench. In this paper we reflect on the diverse technologies of MSPs, how they increased scientific ocean drilling capability in the Integrated Ocean Drilling Program (2003−2013) and International Ocean Discovery Program (2013–2024), and the scientific achievements that they enabled.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423063","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}
Pub Date : 2024-09-24DOI: 10.1016/j.margeo.2024.107404
Drowned paleo-coastal and fluvial landforms preserved on continental shelves are important indicators of sea-level changes during the Quaternary. Morphological analyses of paleo-coastal and fluvial submerged features using multibeam bathymetry as basic datasets, were carried out on the Southeast Brazilian Shelf. The aim was to investigate the interaction between incised valleys and submerged barriers and their temporal relationship. Six partially infilled incised valleys with sinuous and meandering features, and up to ∼40 m of fluvial incision were observed, including several morphologies associated with meanders (e.g., point bars, neck, cut-bank). Paleo-coastal features, mainly related to barriers, were found at four depth ranges (DR) in a dip orientation: DR1 (>60 m); DR2 (55 m–60 m); DR3 (50 m–55 m); DR4 (45 m–50 m). The geomorphic results show that valleys and coastal barriers coexisted and that lower and narrower barriers tend to occur near the shelf break. Preliminary geomorphic evolution between incised valleys and coastal barriers encompasses two possible origins: I) paleo-coastal features of DR 2–4 developed during the interstadial fluctuations of sea-level in MIS 3–5 and/or multiple genetic phases with different base level cycles. The valleys had two phases of incisions related to the base level drop below the shelf break: MIS 4 in the shallow incisions (terraces) and MIS 2 in the main incisions. Moreover, the development of DR 1 was related to the post-LGM base level rise; II) All submerged coastal (DR 1–4) and fluvial features developed during post-LGM base level rise (i.e., fluvial and coastal dynamics in the same cycle of base level change). The multiple phases of base-level changes inducing phases of valley incisions and barrier formation is more likely the be a better explanation. From this perspective, geochronological studies using sedimetary cores in the paleo-coastal and fluvial features are crucial to validate these scenarios, and thus contributing to fill knowledge gaps regarding morphosedimentary responses to base-level changes on the western Atlantic margin.
保存在大陆架上的淹没古海岸和河流地貌是第四纪海平面变化的重要指标。利用多波束测深数据作为基本数据集，对巴西东南大陆架上的古海岸和河流淹没地貌进行了形态学分析。目的是研究切谷与水下障碍物之间的相互作用及其时间关系。观测到六个部分被填平的切谷，具有蜿蜒曲折的特征，河道切口长达 40 米，包括与蜿蜒曲折有关的几种形态（如点状条形、颈状、切槽）。在四个深度范围（DR）发现了古海岸特征，主要与障碍物有关，呈倾角方向：DR1（60 米）；DR2（55 米-60 米）；DR3（50 米-55 米）；DR4（45 米-50 米）。地貌结果表明，山谷和海岸屏障共存，较低和较窄的屏障往往出现在陆架断裂附近。切谷与海岸屏障之间的初步地貌演变包括两种可能的起源：I) DR 2-4 的古海岸地貌是在 MIS 3-5 的海平面间期波动中形成的，和/或具有不同基底面周期的多个成因阶段。山谷有两个阶段的切口与大陆架断裂以下的基底面下降有关：浅切口（阶地）为 MIS 4，主切口为 MIS 2。此外，DR 1 的发展与后大地构造时期的基面上升有关；(II) 所有沉积海岸地貌（DR 1-4）和河流地貌都是在后大地构造时期基面上升过程中形成的（即河流和海岸动力学处于同一基面变化周期）。基面变化的多个阶段引起山谷切裂和屏障形成的阶段，更有可能是一种更好的解释。从这个角度看，利用古海岸和河流地貌中的沉积岩芯进行地质年代研究，对于验证这些假设是至关重要的，从而有助于填补大西洋西缘形态沉积对基底变化响应方面的知识空白。
{"title":"Drowned barriers and valleys: A morphological archive of base level changes in the western South Atlantic","authors":"","doi":"10.1016/j.margeo.2024.107404","DOIUrl":"10.1016/j.margeo.2024.107404","url":null,"abstract":"<div><div>Drowned paleo-coastal and fluvial landforms preserved on continental shelves are important indicators of sea-level changes during the Quaternary. Morphological analyses of paleo-coastal and fluvial submerged features using multibeam bathymetry as basic datasets, were carried out on the Southeast Brazilian Shelf. The aim was to investigate the interaction between incised valleys and submerged barriers and their temporal relationship. Six partially infilled incised valleys with sinuous and meandering features, and up to ∼40 m of fluvial incision were observed, including several morphologies associated with meanders (e.g., point bars, neck, cut-bank). Paleo-coastal features, mainly related to barriers, were found at four depth ranges (DR) in a dip orientation: DR1 (>60 m); DR2 (55 m–60 m); DR3 (50 m–55 m); DR4 (45 m–50 m). The geomorphic results show that valleys and coastal barriers coexisted and that lower and narrower barriers tend to occur near the shelf break. Preliminary geomorphic evolution between incised valleys and coastal barriers encompasses two possible origins: I) paleo-coastal features of DR 2–4 developed during the interstadial fluctuations of sea-level in MIS 3–5 and/or multiple genetic phases with different base level cycles. The valleys had two phases of incisions related to the base level drop below the shelf break: MIS 4 in the shallow incisions (terraces) and MIS 2 in the main incisions. Moreover, the development of DR 1 was related to the post-LGM base level rise; II) All submerged coastal (DR 1–4) and fluvial features developed during post-LGM base level rise (i.e., fluvial and coastal dynamics in the same cycle of base level change). The multiple phases of base-level changes inducing phases of valley incisions and barrier formation is more likely the be a better explanation. From this perspective, geochronological studies using sedimetary cores in the paleo-coastal and fluvial features are crucial to validate these scenarios, and thus contributing to fill knowledge gaps regarding morphosedimentary responses to base-level changes on the western Atlantic margin.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142327705","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}
Pub Date : 2024-09-24DOI: 10.1016/j.margeo.2024.107405
<div><div>Sofu Seamount is one of the poorly studied submarine edifices in the Izu-Bonin Arc. There is no known historical record of volcanic activity, thus its eruptive history and volcanic features are completely unknown. However, on October 9, 2023, at least 14 <em>T</em>-phases originating near Sofu Seamount were observed. An 80 km-long raft of floating pumice was observed off Sofu Seamount on October 20. These spatially and temporally coherent observations indicate that an eruption occurred from a deep seafloor vent somewhere near Sofu Seamount. In order to investigate the origin of this submarine eruption, we collected new bathymetric data in 2024 and compared it with older bathymetric data collected in 2022, 2007 and 1987. The bathymetric comparison revealed evidence for explosive eruptions at Sofu Seamount between 2022 and 2024. During this time, a crater, 1.6 km wide and 400 m deep, was formed at the pre-existing central cone on the western part of Sofu Seamount, whose pre-eruption summit depth was 737 m. The maximum negative depth change was 451 m and a volume of 430 × 10<sup>6</sup> m<sup>3</sup> was removed due to the crater formation. A dome-like structure, 1 km wide and 100 m high was constructed northeast of the crater, part of which collapsed as a result of the crater formation. The volcanic products were transported over 6 km downslope and emplaced on the adjacent seafloor where positive depth changes up to 75 m were observed. Landslides also occurred around the crater. The largest slide on the northern flank formed a slide scar that is 3.8 km long and 1 km wide. Here, the maximum negative depth change was 148 m and 140 × 10<sup>6</sup> m<sup>3</sup> of material was removed. The slide materials were deposited downslope where positive depth changes up to 61 m were observed. Considering the occurrence of the earthquake swarm on October 2–8, 2023 and <em>T</em>-phase swarm on October 9, the timing of the eruption can be constrained within October 2023.</div><div>An analysis of volcanic and tectonic morphology reveals a distinct tectonic influence on volcanism at Sofu Seamount. Sofu Seamount is located in a back-arc rift zone where the N–S trending Torishima and Sofu Rifts have formed. The new bathymetric data showed that the rifts have an asymmetric structure and can be divided into two segments, which are identified here as inner and outer rifts. The inner rifts are bounded by steeper fault scarps that have experienced more subsidence than the outer rifts. The western part of Sofu Seamount, where the eruption occurred, is located within the inner rifts, and is heavily dissected by rifting-related normal faults, while the eastern part is located outward of the inner rifts and is not dissected by faults. The October earthquake swarm was more concentrated in the area of the inner rifts and some large earthquakes showed normal fault focal mechanisms with a tension axis approximately in E–W direction. Our morphological observations comb
{"title":"Morphological evidence of an explosive eruption event in October 2023 at Sofu Seamount in the Izu-Bonin Arc","authors":"","doi":"10.1016/j.margeo.2024.107405","DOIUrl":"10.1016/j.margeo.2024.107405","url":null,"abstract":"<div><div>Sofu Seamount is one of the poorly studied submarine edifices in the Izu-Bonin Arc. There is no known historical record of volcanic activity, thus its eruptive history and volcanic features are completely unknown. However, on October 9, 2023, at least 14 <em>T</em>-phases originating near Sofu Seamount were observed. An 80 km-long raft of floating pumice was observed off Sofu Seamount on October 20. These spatially and temporally coherent observations indicate that an eruption occurred from a deep seafloor vent somewhere near Sofu Seamount. In order to investigate the origin of this submarine eruption, we collected new bathymetric data in 2024 and compared it with older bathymetric data collected in 2022, 2007 and 1987. The bathymetric comparison revealed evidence for explosive eruptions at Sofu Seamount between 2022 and 2024. During this time, a crater, 1.6 km wide and 400 m deep, was formed at the pre-existing central cone on the western part of Sofu Seamount, whose pre-eruption summit depth was 737 m. The maximum negative depth change was 451 m and a volume of 430 × 10<sup>6</sup> m<sup>3</sup> was removed due to the crater formation. A dome-like structure, 1 km wide and 100 m high was constructed northeast of the crater, part of which collapsed as a result of the crater formation. The volcanic products were transported over 6 km downslope and emplaced on the adjacent seafloor where positive depth changes up to 75 m were observed. Landslides also occurred around the crater. The largest slide on the northern flank formed a slide scar that is 3.8 km long and 1 km wide. Here, the maximum negative depth change was 148 m and 140 × 10<sup>6</sup> m<sup>3</sup> of material was removed. The slide materials were deposited downslope where positive depth changes up to 61 m were observed. Considering the occurrence of the earthquake swarm on October 2–8, 2023 and <em>T</em>-phase swarm on October 9, the timing of the eruption can be constrained within October 2023.</div><div>An analysis of volcanic and tectonic morphology reveals a distinct tectonic influence on volcanism at Sofu Seamount. Sofu Seamount is located in a back-arc rift zone where the N–S trending Torishima and Sofu Rifts have formed. The new bathymetric data showed that the rifts have an asymmetric structure and can be divided into two segments, which are identified here as inner and outer rifts. The inner rifts are bounded by steeper fault scarps that have experienced more subsidence than the outer rifts. The western part of Sofu Seamount, where the eruption occurred, is located within the inner rifts, and is heavily dissected by rifting-related normal faults, while the eastern part is located outward of the inner rifts and is not dissected by faults. The October earthquake swarm was more concentrated in the area of the inner rifts and some large earthquakes showed normal fault focal mechanisms with a tension axis approximately in E–W direction. Our morphological observations comb","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423062","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}
Pub Date : 2024-09-21DOI: 10.1016/j.margeo.2024.107402
The Alabama Underwater or Drowned Forest is a well-preserved Late Pleistocene (dated to 72–56 ± 8 ka, 2σ) terrestrial landform on the northern Gulf of Mexico continental shelf that provides geomorphic and ecosystem information rarely preserved during the glacial intervals. Stumps of bald cypress (Taxodium distichum (L.) Rich.) trees were exposed in ∼18 m of water following Hurricane Ivan in 2004. This research investigates geomorphic changes to the Mississippi-Alabama-Florida (MAFLA) sand sheet, which presents as shore-oblique Holocene sand ridges, and the exposure and burial of tree stumps following the passage of Hurricane Sally in 2020 using repeat sidescan and bathymetric surveys (2015–2016 and 2021). Using two newly identified tree exposure areas and their geological properties, this research also hypothesized a new location where tree stumps may be outcropping. The bathymetry indicates regions with up to ∼1 m of erosion and deposition over the five years between the two surveys. Similarly, the sidescan sonar indicates changes in the location and numbers of exposed tree stumps as well as between 47,000 and 62,500 tons of sediment erosion within the study area following Hurricane Sally. The 2015 and 2016 data found 25 tree contacts whereas the 2021 survey found 76 tree contacts and only 5 of them occurred in both surveys suggesting the tree exposures are dynamic and presumably changing with the passing of large tropical cyclones. Additionally, the hypothesized exposure location had 26 newly identified tree stump contacts within a mixed texture unit along the sand-mud boundary, confirming our understanding of the geomorphic characteristics leading to the exposure of the buried forest. This research will expand the potential areas for investigations into Late Pleistocene ecosystems and landforms and their associated climatic and ecologic conditions in the Gulf of Mexico as well as in other passive continental margins.
{"title":"Storm-Driven Tree Exposure and Geomorphic Change: Predicting the Distribution of Preserved Late Pleistocene Tree Stumps on the Outer Alabama Continental Shelf","authors":"","doi":"10.1016/j.margeo.2024.107402","DOIUrl":"10.1016/j.margeo.2024.107402","url":null,"abstract":"<div><div>The Alabama Underwater or Drowned Forest is a well-preserved Late Pleistocene (dated to 72–56 ± 8 ka, 2σ) terrestrial landform on the northern Gulf of Mexico continental shelf that provides geomorphic and ecosystem information rarely preserved during the glacial intervals. Stumps of bald cypress (<em>Taxodium distichum</em> (L.) Rich.) trees were exposed in ∼18 m of water following Hurricane Ivan in 2004. This research investigates geomorphic changes to the Mississippi-Alabama-Florida (MAFLA) sand sheet, which presents as shore-oblique Holocene sand ridges, and the exposure and burial of tree stumps following the passage of Hurricane Sally in 2020 using repeat sidescan and bathymetric surveys (2015–2016 and 2021). Using two newly identified tree exposure areas and their geological properties, this research also hypothesized a new location where tree stumps may be outcropping. The bathymetry indicates regions with up to ∼1 m of erosion and deposition over the five years between the two surveys. Similarly, the sidescan sonar indicates changes in the location and numbers of exposed tree stumps as well as between 47,000 and 62,500 tons of sediment erosion within the study area following Hurricane Sally. The 2015 and 2016 data found 25 tree contacts whereas the 2021 survey found 76 tree contacts and only 5 of them occurred in both surveys suggesting the tree exposures are dynamic and presumably changing with the passing of large tropical cyclones. Additionally, the hypothesized exposure location had 26 newly identified tree stump contacts within a mixed texture unit along the sand-mud boundary, confirming our understanding of the geomorphic characteristics leading to the exposure of the buried forest. This research will expand the potential areas for investigations into Late Pleistocene ecosystems and landforms and their associated climatic and ecologic conditions in the Gulf of Mexico as well as in other passive continental margins.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142357014","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}
Pub Date : 2024-09-18DOI: 10.1016/j.margeo.2024.107401
Magnetofossils in the continental shelf sediments of the Yellow and Bohai Seas have long been overlooked. Based on the magnetic results of 88 surface sediments (0–10 cm depth), first-order reversal curve (FORC) diagrams, isothermal remanent magnetization (IRM) acquisition curves from 6 representative samples, and transmission electron microscopy (TEM) observations of 2 samples, the formation and preservation mechanisms of magnetofossils in this region are elucidated. The FORC diagrams consistently show a clear central ridge feature, which indicates the presence of intact magnetofossils in all representative samples. The morphologies observed by TEM are primarily equant and elongated, with minimal or no bullet-shaped (magnetite) magnetofossils. Analysis further reveals a widespread distribution of magnetofossils in the mud areas of the Bohai Sea, North Yellow Sea, and South Yellow Sea, with proportions (contribution to SIRM; SIRM is defined as the remanent magnetization that remains constant as the external magnetic field increases) of <32.5 %, 40.9 % ∼ 44.6 %, and 59.9 % ∼ 66.5 %, respectively. Despite the presence of non-biogenic single domain magnetite, the proportion of magnetofossils can be estimated by the χARM/SIRM value, as they are positively correlated. The surface sedimentary environment of these mud areas is primarily suboxic and characterized by abundant dissolved iron, which facilitate the formation of magnetofossils by magnetotactic bacteria (MTB). It is unlikely that the surface sedimentary environment becomes sulphidic, thereby enabling the preservation of magnetofossils after their formation. The redox state of the study area, crucial for magnetofossil formation, is mainly controlled by the total organic carbon (TOC) content. From north to south, the higher proportion of magnetofossils is coupled with higher TOC content, possibly due to the intensified reducing degree of the suboxic environment, promoting MTB proliferation and thus forming more magnetofossils. The mechanisms governing the formation and preservation of magnetofossils proposed in this study may also be applicable to geological records.
{"title":"Formation and preservation mechanisms of magnetofossils in the surface sediments of muddy areas in the ye llow and Bohai Seas, China","authors":"","doi":"10.1016/j.margeo.2024.107401","DOIUrl":"10.1016/j.margeo.2024.107401","url":null,"abstract":"<div><p>Magnetofossils in the continental shelf sediments of the Yellow and Bohai Seas have long been overlooked. Based on the magnetic results of 88 surface sediments (0–10 cm depth), first-order reversal curve (FORC) diagrams, isothermal remanent magnetization (IRM) acquisition curves from 6 representative samples, and transmission electron microscopy (TEM) observations of 2 samples, the formation and preservation mechanisms of magnetofossils in this region are elucidated. The FORC diagrams consistently show a clear central ridge feature, which indicates the presence of intact magnetofossils in all representative samples. The morphologies observed by TEM are primarily equant and elongated, with minimal or no bullet-shaped (magnetite) magnetofossils. Analysis further reveals a widespread distribution of magnetofossils in the mud areas of the Bohai Sea, North Yellow Sea, and South Yellow Sea, with proportions (contribution to SIRM; SIRM is defined as the remanent magnetization that remains constant as the external magnetic field increases) of <32.5 %, 40.9 % ∼ 44.6 %, and 59.9 % ∼ 66.5 %, respectively. Despite the presence of non-biogenic single domain magnetite, the proportion of magnetofossils can be estimated by the χ<sub>ARM</sub>/SIRM value, as they are positively correlated. The surface sedimentary environment of these mud areas is primarily suboxic and characterized by abundant dissolved iron, which facilitate the formation of magnetofossils by magnetotactic bacteria (MTB). It is unlikely that the surface sedimentary environment becomes sulphidic, thereby enabling the preservation of magnetofossils after their formation. The redox state of the study area, crucial for magnetofossil formation, is mainly controlled by the total organic carbon (TOC) content. From north to south, the higher proportion of magnetofossils is coupled with higher TOC content, possibly due to the intensified reducing degree of the suboxic environment, promoting MTB proliferation and thus forming more magnetofossils. The mechanisms governing the formation and preservation of magnetofossils proposed in this study may also be applicable to geological records.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142271103","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}
Pub Date : 2024-09-13DOI: 10.1016/j.margeo.2024.107400
The archipelagic aprons of the large deep-sea seamounts of the northwestern Pacific Ocean (NWPO) show potential areas for significant reserves of ferromanganese nodules (FMNs). This study used datasets such as depth, backscatter intensity (BI), and optical coverage in conjunction with mineralogical, element geochemical, Sr-Nd-Pb isotopic, and chronological analyses of FMNs of the Suda Guyot (SG), which was located on the central area of the Marcus-Wake seamounts, in the NWPO. The results indicated a Y-shaped distribution of the deposit on the northern apron of the SG. Landslides predated the mineralization processes of the FMN deposit, and the ubiquitous channels in the apron had largely minimal influence on the distribution of nodules. Current mineralization of the deposit has been ongoing for ∼10 Myrs. Continuous weakening of the Antarctic Bottom Water (AABW) resulted in a gradual decrease in bottom water oxygen contents around the SG. This in turn resulted in a decrease in cryptocrystalline Fe-vernadite (δ-MnO2) and elemental contents associated with δ-MnO2 of FMNs, such as Mo, Te, and Tl. Meanwhile, the contribution of Asian dust to the study area increased, leading to increased Fe, which in turn increased amorphous ferrihydrite (FeOOH), and FeOOH-associated elements such as Ti, Pb, and Th. Productivity gradually increased to its peak value around 4–5 Myrs ago, leading to similar trends in REY, Ba, and U. REY contents exhibited a certain correlation with water depth around the SG. The results of this study suggest that the Carbonate Compensation Depth (CCD) variation resulted in higher content of REY of the FMNs in the shallower apron.
{"title":"Geological and oceanographic constrains on the deposit of ferromanganese nodules on the archipelagic aprons of seamounts","authors":"","doi":"10.1016/j.margeo.2024.107400","DOIUrl":"10.1016/j.margeo.2024.107400","url":null,"abstract":"<div><p>The archipelagic aprons of the large deep-sea seamounts of the northwestern Pacific Ocean (NWPO) show potential areas for significant reserves of ferromanganese nodules (FMNs). This study used datasets such as depth, backscatter intensity (BI), and optical coverage in conjunction with mineralogical, element geochemical, Sr-Nd-Pb isotopic, and chronological analyses of FMNs of the Suda Guyot (SG), which was located on the central area of the Marcus-Wake seamounts, in the NWPO. The results indicated a Y-shaped distribution of the deposit on the northern apron of the SG. Landslides predated the mineralization processes of the FMN deposit, and the ubiquitous channels in the apron had largely minimal influence on the distribution of nodules. Current mineralization of the deposit has been ongoing for ∼10 Myrs. Continuous weakening of the Antarctic Bottom Water (AABW) resulted in a gradual decrease in bottom water oxygen contents around the SG. This in turn resulted in a decrease in cryptocrystalline Fe-vernadite (δ-MnO<sub>2</sub>) and elemental contents associated with δ-MnO<sub>2</sub> of FMNs, such as Mo, Te, and Tl. Meanwhile, the contribution of Asian dust to the study area increased, leading to increased Fe, which in turn increased amorphous ferrihydrite (FeOOH), and FeOOH-associated elements such as Ti, Pb, and Th. Productivity gradually increased to its peak value around 4–5 Myrs ago, leading to similar trends in REY, Ba, and U. REY contents exhibited a certain correlation with water depth around the SG. The results of this study suggest that the Carbonate Compensation Depth (CCD) variation resulted in higher content of REY of the FMNs in the shallower apron.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142233721","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}
Pub Date : 2024-09-11DOI: 10.1016/j.margeo.2024.107397
This work aims to establish the role of liquefaction in a shallow submarine environment defined by a canyon head reaching the coast. The study area is the Garrucha submarine canyon head, which is located in the western Mediterranean Sea.
The potential of liquefaction is approached empirically by two methods in parallel, undrained cyclic direct simple shear (UCDSS) test and piezocone penetration test (CPTu) analyses. For both approaches, considering the regional earthquake records, a cyclic load linked to Mw ≤ 6.5 earthquake events or a maximum ground surface acceleration amax of 0.25 g is considered.
The sediment samples analysed are nonplastic sands with low silt/clay contents and can be defined as liquefiable. Geotechnical analysis reveals a high probability of triggering liquefaction in this kind of sediment at depths greater than 3 m below the seafloor. CPTu records are used to assess and improve the liquefaction model for the study area by defining 3 different stratigraphic configurations or liquefiable conditions: uniformly liquefiable, interbedded liquifiable and nonliquefiable.
This work highlights the importance of liquefaction—a process normally underestimated in submarine environments—in the downslope transport of sediment from the upper part of a canyon and, more generally, in canyon head evolution with different potential morphosedimentary consequences.
{"title":"The role of liquefaction in the evolution of shallow submarine canyon heads from a geotechnical perspective: A case study of the Garrucha Canyon (SE Mediterranean)","authors":"","doi":"10.1016/j.margeo.2024.107397","DOIUrl":"10.1016/j.margeo.2024.107397","url":null,"abstract":"<div><div>This work aims to establish the role of liquefaction in a shallow submarine environment defined by a canyon head reaching the coast. The study area is the Garrucha submarine canyon head, which is located in the western Mediterranean Sea.</div><div>The potential of liquefaction is approached empirically by two methods in parallel, undrained cyclic direct simple shear (UCDSS) test and piezocone penetration test (CPTu) analyses. For both approaches, considering the regional earthquake records, a cyclic load linked to Mw ≤ 6.5 earthquake events or a maximum ground surface acceleration a<sub>max</sub> of 0.25 g is considered.</div><div>The sediment samples analysed are nonplastic sands with low silt/clay contents and can be defined as liquefiable. Geotechnical analysis reveals a high probability of triggering liquefaction in this kind of sediment at depths greater than 3 m below the seafloor. CPTu records are used to assess and improve the liquefaction model for the study area by defining 3 different stratigraphic configurations or liquefiable conditions: uniformly liquefiable, interbedded liquifiable and nonliquefiable.</div><div>This work highlights the importance of liquefaction—a process normally underestimated in submarine environments—in the downslope transport of sediment from the upper part of a canyon and, more generally, in canyon head evolution with different potential morphosedimentary consequences.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423065","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}
Pub Date : 2024-08-30DOI: 10.1016/j.margeo.2024.107386
The formation and development of a small Mediterranean deltaic system are investigated through a primary seismic stratigraphic interpretation of a high-resolution seismic profile network, combined with multiple bathymetric data (including multibeam bathymetric imagery) and collated with shallow sediment cores collected with a vibro-corer device.
The submarine delta of the Adra River is divided into a basal patchy seismic unit and five wedge-shaped younger seismic units that are related to the Holocene highstand stabilization. Limited age control indicates that the two uppermost seismic units are very recent, most likely related to a dearth of fluvial fluxes led by channel deviations and by sediment retention. The formation of the three older seismic units is correlated to three humid periods during the Middle Holocene, Late Holocene and Little Ice Age, under a general context of progressive aridification of southeastern Iberia.
The stacking patterns and spatial distribution of individual seismic units document a history of episodic progradation of successive prodeltaic lobes, with a long-term evolution mediated by climatically-induced changes in the river basin and more recent anthropogenic interventions. Overall, the subaqueous deltaic system registers the complete modification of a deltaic system that evolves from a fluvial-dominated delta to recent wave-dominated wedges. In between, the deltaic system exhibits a progressive asymmetric character, due to the instauration of Atlantic waters on the shelf and their subsequent eastward redistribution. The Adra deltaic system is proposed as an outstanding example of a small deltaic system that reacts almost immediately to the complex interaction between natural changes in the system and anthropogenic interventions in the drainage basin.
{"title":"The Late Holocene evolution of the Adra Delta subaqueous system (Northern Alboran Sea): Seismic-stratigraphic and geomorphic evidence of millennial scale climatic and anthropic effects","authors":"","doi":"10.1016/j.margeo.2024.107386","DOIUrl":"10.1016/j.margeo.2024.107386","url":null,"abstract":"<div><p>The formation and development of a small Mediterranean deltaic system are investigated through a primary seismic stratigraphic interpretation of a high-resolution seismic profile network, combined with multiple bathymetric data (including multibeam bathymetric imagery) and collated with shallow sediment cores collected with a vibro-corer device.</p><p>The submarine delta of the Adra River is divided into a basal patchy seismic unit and five wedge-shaped younger seismic units that are related to the Holocene highstand stabilization. Limited age control indicates that the two uppermost seismic units are very recent, most likely related to a dearth of fluvial fluxes led by channel deviations and by sediment retention. The formation of the three older seismic units is correlated to three humid periods during the Middle Holocene, Late Holocene and Little Ice Age, under a general context of progressive aridification of southeastern Iberia.</p><p>The stacking patterns and spatial distribution of individual seismic units document a history of episodic progradation of successive prodeltaic lobes, with a long-term evolution mediated by climatically-induced changes in the river basin and more recent anthropogenic interventions. Overall, the subaqueous deltaic system registers the complete modification of a deltaic system that evolves from a fluvial-dominated delta to recent wave-dominated wedges. In between, the deltaic system exhibits a progressive asymmetric character, due to the instauration of Atlantic waters on the shelf and their subsequent eastward redistribution. The Adra deltaic system is proposed as an outstanding example of a small deltaic system that reacts almost immediately to the complex interaction between natural changes in the system and anthropogenic interventions in the drainage basin.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0025322724001701/pdfft?md5=43d32b4fb917309ad1c5c872018eded5&pid=1-s2.0-S0025322724001701-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142117677","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}
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