Netherlands Journal of Geosciences最新文献

{"title":"New radiocarbon age constraints on the eruption history of the Quill volcano, St. Eustatius, Dutch Caribbean","authors":"Pieter Z. Vroon, Hobie M. van Zadelhoff, Bert van der Valk, Michiel J. van der Meulen, Gareth R. Davies","doi":"10.1017/njg.2023.14","DOIUrl":"https://doi.org/10.1017/njg.2023.14","url":null,"abstract":"The late Pleistocene to Holocene subaerial pyroclastic deposits of the Quill stratovolcano on the Caribbean island of St Eustatius form seven stratigraphic divisions. New radiocarbon ages of charcoal are presented for the second, third and seventh divisions in order to better constrain the Quill’s eruption history. Three samples from the same layer of Division 2 at two localities on the northeast coast yield ages of 18,020 ± 40 (1σ), 18,310 ± 45 and 18,490 ± 45 <jats:sup>14</jats:sup>C yr BP (∼19,800–20,600 yr cal BC). These are considerably younger (∼4400 yr) than a previously published result for this division. A single sample of Division 3 gave an age of 8090 <jats:sup>14</jats:sup>C yr BP (∼7100 yr cal BC) and overlaps with previously published <jats:sup>14</jats:sup>C ages for this division. A charred root in the pyroclastic unit deposited by the last eruption of the Quill (Division 7) gave an age of 919 <jats:sup>14</jats:sup>C yr BP (∼1100–1200 yr cal AD). This result is ∼600 years younger than a previously published age, and its origin is attributed to human activity. The timing of the last eruption of the Quill therefore remains poorly constrained but is older than 600 AD. Terrestrial gastropods found in paleosols and organic material found in small streams that developed in Division 3 indicate that Division 4 must be younger than 6100 ± 500 yr cal BC. The oxygen and carbon isotope composition of the terrestrial gastropods derived from Division 3 paleosols indicates that the C4 and CAM-type vegetation was dominant and that the climate subsequently changed to wetter conditions. The minimum eruption frequency for the Quill volcano is one eruption every ∼1400 years during the past 22,000 years. This eruption frequency of the Quill volcano is of the same order of magnitude as other recent northern Lesser Antilles volcanoes, Soufrière Hills (Montserrat, ∼5000 years) and Mt Liamuiga (St. Kitts, ∼2500 years).","PeriodicalId":501577,"journal":{"name":"Netherlands Journal of Geosciences","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140005345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Large-scale morphological changes and sediment budget of the Western Scheldt estuary 1955–2020: the impact of large-scale sediment management","authors":"Edwin P. L. Elias, Ad J. F. Van der Spek, Zheng Bing Wang, Jelmer Cleveringa, Claire J. L. Jeuken, Marcel Taal, Jebbe J. Van der Werf","doi":"10.1017/njg.2023.11","DOIUrl":"https://doi.org/10.1017/njg.2023.11","url":null,"abstract":"In the Western Scheldt estuary, like in many estuaries, safe navigation, flood protection, and ecological targets require a balanced and sustainable sediment management. A thorough understanding of the morphodynamic functioning of the estuary and its response to changes in hydrodynamics (natural sediment transport) and large-scale interventions is imperative. This paper presents a detailed overview of over 65 years of morphological changes and a comprehensive sediment budget of the Western Scheldt estuary that is based on analysis of a unique series of frequent bathymetric surveys and historical data on human–sediment interactions of dredging, dredge disposal and sand mining. Solving the sediment budget reveals an annual sediment import of 2.2 million m<jats:sup>3</jats:sup>. The highest sediment imports occurred between 1980–1994 and 2005–2020 (2.9 and 3.7 million m<jats:sup>3</jats:sup>/year). A 1.3 million m<jats:sup>3</jats:sup>/year net export prevailed between 1994 and 2005. Natural variations in the hydrodynamics (e.g., tidal asymmetry and amplification) and sediment transports cannot explain the derived temporal variations in sediment import rates. Anthropogenic activities play a dominant role. Capital dredging of the main navigation channel has led to channel deepening and significantly increased dredge and disposal volumes. Disposal on tidal flats and in the secondary channel leads to a long-term storage of sand and, consequently, a local increase in bed level and a sand deficit in the remainder of the system that results in increased sediment imports. Large-scale disposal in the western part of the estuary can (temporarily) reverse the sediment exchange between the estuary and its mouth area, as observed between 1994 and 2005. Apparently, large-scale anthropogenic reallocation of sediment by dredging and/or disposal as part of navigation channel improvement, sand mining or nourishment essentially influences the morphological development of the Western Scheldt estuary. This reveals responsibilities as well as opportunities of sediment management for the Western Scheldt and similar estuaries worldwide.","PeriodicalId":501577,"journal":{"name":"Netherlands Journal of Geosciences","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138543866","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}