Diagenesis of upper jurassic concretions from the Antarctic Peninsula

Early-diagenetic calcite concretions are widespread in mudstone-tuff sequences deposited in Late Jurassic oxygen-deficient basins of the Antarctic Peninsula. Although obscured or destroyed in host rocks, original components and sedimentary structures are well preserved in concretions, in spite of si...

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Detalles Bibliográficos
Publicado: 2001
Materias:
calcite
concretion
diagenesis
Jurassic
Antarctica
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_15271404_v71_n1_p88_Scasso
http://hdl.handle.net/20.500.12110/paper_15271404_v71_n1_p88_Scasso
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id paper:paper_15271404_v71_n1_p88_Scasso
record_format dspace
spelling paper:paper_15271404_v71_n1_p88_Scasso2023-06-08T16:19:39Z Diagenesis of upper jurassic concretions from the Antarctic Peninsula calcite concretion diagenesis Jurassic Antarctica Early-diagenetic calcite concretions are widespread in mudstone-tuff sequences deposited in Late Jurassic oxygen-deficient basins of the Antarctic Peninsula. Although obscured or destroyed in host rocks, original components and sedimentary structures are well preserved in concretions, in spite of significant mineralogical and geochcmical change during growth. Early diagenesis led to a rapid and almost total variation in the mineralogy within the concretions, independently of the original host lithologies. Siliceous particles were replaced by chlorite and zeolites in suboxic, alkaline, and moderately reducing conditions on the sea floor and in the first centimeters of burial. These conditions also led to localized early formation of phosphate concretions. Pyrite developed subsequently because of high sulfide abundance in the sulfate reduction zone. Most calcite precipitation took place in the lower part of the sulfate reduction zone in a strongly alkaline environment where sulfide content had been lowered by pyrite precipitation. In this stage, the remaining siliceous elements were dissolved or replaced by calcite. Later diagenetic changes include enlargement of zeolites, minor changes in clay minerals, and the formation of calcite veins. The wide range of δ13C values in cement and vein calcite (-1.4‰ and -20.23‰ PDB) is explained by mixed carbon sources from organic matter oxidation and dissolution of calcareous shells. The low δ18O of calcite (-2.34‰ to -19.72‰ PDB) is the result of recrystallization in contact with high-temperature diagenetic or hydrothermal fluids flushed through micro-fractures in the concretions, which also produced extensive vein formation. Copyright © 2001, SEPM (Society for Sedimentary Geology). 2001 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_15271404_v71_n1_p88_Scasso http://hdl.handle.net/20.500.12110/paper_15271404_v71_n1_p88_Scasso
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic calcite
concretion
diagenesis
Jurassic
Antarctica
spellingShingle calcite
concretion
diagenesis
Jurassic
Antarctica
Diagenesis of upper jurassic concretions from the Antarctic Peninsula
topic_facet calcite
concretion
diagenesis
Jurassic
Antarctica
description Early-diagenetic calcite concretions are widespread in mudstone-tuff sequences deposited in Late Jurassic oxygen-deficient basins of the Antarctic Peninsula. Although obscured or destroyed in host rocks, original components and sedimentary structures are well preserved in concretions, in spite of significant mineralogical and geochcmical change during growth. Early diagenesis led to a rapid and almost total variation in the mineralogy within the concretions, independently of the original host lithologies. Siliceous particles were replaced by chlorite and zeolites in suboxic, alkaline, and moderately reducing conditions on the sea floor and in the first centimeters of burial. These conditions also led to localized early formation of phosphate concretions. Pyrite developed subsequently because of high sulfide abundance in the sulfate reduction zone. Most calcite precipitation took place in the lower part of the sulfate reduction zone in a strongly alkaline environment where sulfide content had been lowered by pyrite precipitation. In this stage, the remaining siliceous elements were dissolved or replaced by calcite. Later diagenetic changes include enlargement of zeolites, minor changes in clay minerals, and the formation of calcite veins. The wide range of δ13C values in cement and vein calcite (-1.4‰ and -20.23‰ PDB) is explained by mixed carbon sources from organic matter oxidation and dissolution of calcareous shells. The low δ18O of calcite (-2.34‰ to -19.72‰ PDB) is the result of recrystallization in contact with high-temperature diagenetic or hydrothermal fluids flushed through micro-fractures in the concretions, which also produced extensive vein formation. Copyright © 2001, SEPM (Society for Sedimentary Geology).
title Diagenesis of upper jurassic concretions from the Antarctic Peninsula
title_short Diagenesis of upper jurassic concretions from the Antarctic Peninsula
title_full Diagenesis of upper jurassic concretions from the Antarctic Peninsula
title_fullStr Diagenesis of upper jurassic concretions from the Antarctic Peninsula
title_full_unstemmed Diagenesis of upper jurassic concretions from the Antarctic Peninsula
title_sort diagenesis of upper jurassic concretions from the antarctic peninsula
publishDate 2001
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_15271404_v71_n1_p88_Scasso
http://hdl.handle.net/20.500.12110/paper_15271404_v71_n1_p88_Scasso
_version_ 1768546507932303360

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