Holocene glaucony from the Guadiana shelf, Northern Gulf of Cadiz (SW Iberia): New genetic insights in a sequence stratigraphy context
Autor(a) principal: | |
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Data de Publicação: | 2023 |
Outros Autores: | , , |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
Texto Completo: | http://hdl.handle.net/10400.1/19144 |
Resumo: | Glaucony occurrences have been reported both from exposed transgressive and overlying highstand system tracts. However, its occurrences within highstand deposits are often invoked as the result of underlying condensed section reworking. Detailed textural, mineralogical and geochemical reports of glaucony grains in highstand deposits remain elusive. The northern Gulf of Cadiz shelf (SW Iberia) offers a unique opportunity to investigate late Holocene glaucony authigenesis in a well-documented time-stratigraphic context, where transgressive deposits are locally exposed on the seafloor and are laterally draped by highstand muddy deposits. In this study, glaucony grains extracted from a core retrieved from a highstand muddy depocenter off the Guadiana River were investigated by means of digital microscopy, X-ray diffraction (XRD), and electron microscopic methods (FESEM-EDX and TEM-HRTEM). To better constrain the glaucony origin (autochthonous vs. allochthonous) in highstand muddy deposits, glaucony grains from surficial samples—taken from exposed transgressive deposits—were also investigated. Glauconitization in the studied core can be largely attributed to the replacement of faecal pellets from c. ~4.2–1.0 cal. ka BP. Both XRD and TEM-HRTEM analyses indicate that glaucony consists mainly of an R1, with a minor presence of R0, smectite-rich (nontronite) glauconite-smectite mixed-layer silicate, made up of 35–75% glauconitic layers and 65–25% of interstratified smectite layers. At the mineral lattice level, minor individual 7Å layers (berthierine) were also identified by HRTEM. Shallow radial cracks at the pellet surface, along with globular and vermiform-like biomorphic to low packing density lamellar-flaky nanostructures, mineralogical properties, and K-poor content (average 0.4 atoms p.f.u.) indicate a scarcely mature glauconitization process, attesting to formation of the grains in situ (autochthonous). Glaucony grains from exposed transgressive deposits, i.e., in the tests of calcareous benthic foraminifera, do not share a genetic relationship with the grains investigated in the highstand deposits, thus supporting the autochthonous origin of glaucony within the highstand deposits. Our combined dataset provides evidence of a multiphase history for autochthonous glaucony formation in the Guadiana shelf, as its genesis is traced to both transgressive and highstand conditions. While eustatic sea-level changes favoured glaucony formation under transgressive conditions, factors such as protracted low sediment supply and the establishment of a strong nutrient-rich upwelling system in the study area promoted glaucony development during late Holocene highstand conditions. |
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Holocene glaucony from the Guadiana shelf, Northern Gulf of Cadiz (SW Iberia): New genetic insights in a sequence stratigraphy contextGlauconySequence-stratigraphyHSTContinental shelfGulf of CadizHoloceneGlaucony occurrences have been reported both from exposed transgressive and overlying highstand system tracts. However, its occurrences within highstand deposits are often invoked as the result of underlying condensed section reworking. Detailed textural, mineralogical and geochemical reports of glaucony grains in highstand deposits remain elusive. The northern Gulf of Cadiz shelf (SW Iberia) offers a unique opportunity to investigate late Holocene glaucony authigenesis in a well-documented time-stratigraphic context, where transgressive deposits are locally exposed on the seafloor and are laterally draped by highstand muddy deposits. In this study, glaucony grains extracted from a core retrieved from a highstand muddy depocenter off the Guadiana River were investigated by means of digital microscopy, X-ray diffraction (XRD), and electron microscopic methods (FESEM-EDX and TEM-HRTEM). To better constrain the glaucony origin (autochthonous vs. allochthonous) in highstand muddy deposits, glaucony grains from surficial samples—taken from exposed transgressive deposits—were also investigated. Glauconitization in the studied core can be largely attributed to the replacement of faecal pellets from c. ~4.2–1.0 cal. ka BP. Both XRD and TEM-HRTEM analyses indicate that glaucony consists mainly of an R1, with a minor presence of R0, smectite-rich (nontronite) glauconite-smectite mixed-layer silicate, made up of 35–75% glauconitic layers and 65–25% of interstratified smectite layers. At the mineral lattice level, minor individual 7Å layers (berthierine) were also identified by HRTEM. Shallow radial cracks at the pellet surface, along with globular and vermiform-like biomorphic to low packing density lamellar-flaky nanostructures, mineralogical properties, and K-poor content (average 0.4 atoms p.f.u.) indicate a scarcely mature glauconitization process, attesting to formation of the grains in situ (autochthonous). Glaucony grains from exposed transgressive deposits, i.e., in the tests of calcareous benthic foraminifera, do not share a genetic relationship with the grains investigated in the highstand deposits, thus supporting the autochthonous origin of glaucony within the highstand deposits. Our combined dataset provides evidence of a multiphase history for autochthonous glaucony formation in the Guadiana shelf, as its genesis is traced to both transgressive and highstand conditions. While eustatic sea-level changes favoured glaucony formation under transgressive conditions, factors such as protracted low sediment supply and the establishment of a strong nutrient-rich upwelling system in the study area promoted glaucony development during late Holocene highstand conditions.PDCTM/P/MAR/15289/1999CGL2011-30302-C02-02FJC2021-047046-IDL57/2016/CP1361/CT0009UID/0350/2020MDPISapientiaLópez-Quirós, AdriánLobo, Francisco JoséMendes, IsabelNieto, Fernando2023-02-27T13:33:07Z2023-01-262023-02-24T14:08:31Z2023-01-26T00:00:00Zinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/articleapplication/pdfhttp://hdl.handle.net/10400.1/19144engMinerals 13 (2): 177 (2023)10.3390/min130201772075-163Xinfo:eu-repo/semantics/openAccessreponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãoinstacron:RCAAP2023-07-24T10:31:33Zoai:sapientia.ualg.pt:10400.1/19144Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireopendoar:71602024-03-19T20:08:47.732740Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãofalse |
dc.title.none.fl_str_mv |
Holocene glaucony from the Guadiana shelf, Northern Gulf of Cadiz (SW Iberia): New genetic insights in a sequence stratigraphy context |
title |
Holocene glaucony from the Guadiana shelf, Northern Gulf of Cadiz (SW Iberia): New genetic insights in a sequence stratigraphy context |
spellingShingle |
Holocene glaucony from the Guadiana shelf, Northern Gulf of Cadiz (SW Iberia): New genetic insights in a sequence stratigraphy context López-Quirós, Adrián Glaucony Sequence-stratigraphy HST Continental shelf Gulf of Cadiz Holocene |
title_short |
Holocene glaucony from the Guadiana shelf, Northern Gulf of Cadiz (SW Iberia): New genetic insights in a sequence stratigraphy context |
title_full |
Holocene glaucony from the Guadiana shelf, Northern Gulf of Cadiz (SW Iberia): New genetic insights in a sequence stratigraphy context |
title_fullStr |
Holocene glaucony from the Guadiana shelf, Northern Gulf of Cadiz (SW Iberia): New genetic insights in a sequence stratigraphy context |
title_full_unstemmed |
Holocene glaucony from the Guadiana shelf, Northern Gulf of Cadiz (SW Iberia): New genetic insights in a sequence stratigraphy context |
title_sort |
Holocene glaucony from the Guadiana shelf, Northern Gulf of Cadiz (SW Iberia): New genetic insights in a sequence stratigraphy context |
author |
López-Quirós, Adrián |
author_facet |
López-Quirós, Adrián Lobo, Francisco José Mendes, Isabel Nieto, Fernando |
author_role |
author |
author2 |
Lobo, Francisco José Mendes, Isabel Nieto, Fernando |
author2_role |
author author author |
dc.contributor.none.fl_str_mv |
Sapientia |
dc.contributor.author.fl_str_mv |
López-Quirós, Adrián Lobo, Francisco José Mendes, Isabel Nieto, Fernando |
dc.subject.por.fl_str_mv |
Glaucony Sequence-stratigraphy HST Continental shelf Gulf of Cadiz Holocene |
topic |
Glaucony Sequence-stratigraphy HST Continental shelf Gulf of Cadiz Holocene |
description |
Glaucony occurrences have been reported both from exposed transgressive and overlying highstand system tracts. However, its occurrences within highstand deposits are often invoked as the result of underlying condensed section reworking. Detailed textural, mineralogical and geochemical reports of glaucony grains in highstand deposits remain elusive. The northern Gulf of Cadiz shelf (SW Iberia) offers a unique opportunity to investigate late Holocene glaucony authigenesis in a well-documented time-stratigraphic context, where transgressive deposits are locally exposed on the seafloor and are laterally draped by highstand muddy deposits. In this study, glaucony grains extracted from a core retrieved from a highstand muddy depocenter off the Guadiana River were investigated by means of digital microscopy, X-ray diffraction (XRD), and electron microscopic methods (FESEM-EDX and TEM-HRTEM). To better constrain the glaucony origin (autochthonous vs. allochthonous) in highstand muddy deposits, glaucony grains from surficial samples—taken from exposed transgressive deposits—were also investigated. Glauconitization in the studied core can be largely attributed to the replacement of faecal pellets from c. ~4.2–1.0 cal. ka BP. Both XRD and TEM-HRTEM analyses indicate that glaucony consists mainly of an R1, with a minor presence of R0, smectite-rich (nontronite) glauconite-smectite mixed-layer silicate, made up of 35–75% glauconitic layers and 65–25% of interstratified smectite layers. At the mineral lattice level, minor individual 7Å layers (berthierine) were also identified by HRTEM. Shallow radial cracks at the pellet surface, along with globular and vermiform-like biomorphic to low packing density lamellar-flaky nanostructures, mineralogical properties, and K-poor content (average 0.4 atoms p.f.u.) indicate a scarcely mature glauconitization process, attesting to formation of the grains in situ (autochthonous). Glaucony grains from exposed transgressive deposits, i.e., in the tests of calcareous benthic foraminifera, do not share a genetic relationship with the grains investigated in the highstand deposits, thus supporting the autochthonous origin of glaucony within the highstand deposits. Our combined dataset provides evidence of a multiphase history for autochthonous glaucony formation in the Guadiana shelf, as its genesis is traced to both transgressive and highstand conditions. While eustatic sea-level changes favoured glaucony formation under transgressive conditions, factors such as protracted low sediment supply and the establishment of a strong nutrient-rich upwelling system in the study area promoted glaucony development during late Holocene highstand conditions. |
publishDate |
2023 |
dc.date.none.fl_str_mv |
2023-02-27T13:33:07Z 2023-01-26 2023-02-24T14:08:31Z 2023-01-26T00:00:00Z |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/article |
format |
article |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://hdl.handle.net/10400.1/19144 |
url |
http://hdl.handle.net/10400.1/19144 |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.none.fl_str_mv |
Minerals 13 (2): 177 (2023) 10.3390/min13020177 2075-163X |
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info:eu-repo/semantics/openAccess |
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openAccess |
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application/pdf |
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MDPI |
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MDPI |
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Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
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RCAAP |
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RCAAP |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
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