Neoproterozoic subaqueous extrusive-intrusive rocks in the Playa Hermosa Formation in Uruguay: Regional and stratigraphic significance

Volcanic rocks in southern Uruguay are linked to an extensional tectonic regime related to the post-collisional Brasiliano-Pan African orogenic cycle. The ca 580 Ma magmatic event is recorded in the Playa Hermosa Formation. In the upper section of this formation several units were defined. The basal...

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Autores principales:	Sánchez Bettucci, Leda, Koukharsky, Magdalena María Luisa, Pazos, Pablo Jose
Publicado:	2009
Materias:	Neoproterozoic Peperites Playa Hermosa Formation Quartz-syenite breccia Uruguay
Acceso en línea:	https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_1342937X_v16_n1_p134_SanchezBettucci http://hdl.handle.net/20.500.12110/paper_1342937X_v16_n1_p134_SanchezBettucci
Aporte de:	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires

id	paper:paper_1342937X_v16_n1_p134_SanchezBettucci
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spelling	paper:paper_1342937X_v16_n1_p134_SanchezBettucci2023-06-08T16:10:29Z Neoproterozoic subaqueous extrusive-intrusive rocks in the Playa Hermosa Formation in Uruguay: Regional and stratigraphic significance Sánchez Bettucci, Leda Koukharsky, Magdalena María Luisa Pazos, Pablo Jose Neoproterozoic Peperites Playa Hermosa Formation Quartz-syenite breccia Uruguay Volcanic rocks in southern Uruguay are linked to an extensional tectonic regime related to the post-collisional Brasiliano-Pan African orogenic cycle. The ca 580 Ma magmatic event is recorded in the Playa Hermosa Formation. In the upper section of this formation several units were defined. The basal unit is a quartz-syenite brecciated deposit, interpreted as the result of explosive episodes of shallow plutonic quartz-syenite intrusion with signs of hydrothermal alteration. Sedimentary and basaltic lithoclasts are occasionally present in the breccia, implying the emplacement of basalts before of that magmatic event. The middle unit is composed of trachytic hyaloclastites. Local distribution and textural evidence indicate that trachytic volcanic pulses have been followed by an explosive event that produced brecciated deposits. The upper unit of the studied sequence is composed of basalts with thin sedimentary intercalations. Most of the outcropping basalts display the typical micro- and macro-features of hyaloclastites; distinctive of extrusions occurred in wet sediments previous to lithification. Basaltic feeder dikes are common in the lower unit. The study of flow structures in the quartz-syenite brecciated deposits led to the recognition of two basaltic inputs. Such differences are related to the intensity of chloritic alteration, which would be related to water contamination. Basaltic peperites are one of the most impressive features of the Playa Hermosa Formation. Hyaloclastites and peperites largely represented among the studied volcanic rocks, and devitrification textures are all evidences of magma/seawater interactions. In the basaltic fragments of the peperites well preserved orange palagonite appears, while the sandstone fractions have lithic clasts of felsic volcanic rocks, such as rhyolitic lavas with perlitic cracks and lithophysae-like structures. Palagonite chemical analyses suggest marine environment and, at the same time, it proves that the studied section lacks of regional metamorphism. The felsic volcanic lithoclasts contained in sandstones could be related to the felsic volcanic lobes intercalations. The studied magmatic event is important in order to formulate correlations with other Neoproterozoic units distributed around the Dom Feliciano belt, like Camaquã and Campo Alegre basins (Brazil), and in the Kaoko belt (NW Namibia) in Africa. Also, Playa Hermosa Formation presents glacigenic features that are well documented, and reinforce the volcanism around 580 Ma in the Rio de la Plata Craton. © 2009 International Association for Gondwana Research. Fil:Sánchez-Bettucci, L. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Koukharsky, M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Pazos, P.J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2009 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_1342937X_v16_n1_p134_SanchezBettucci http://hdl.handle.net/20.500.12110/paper_1342937X_v16_n1_p134_SanchezBettucci
institution	Universidad de Buenos Aires
institution_str	I-28
repository_str	R-134
collection	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic	Neoproterozoic Peperites Playa Hermosa Formation Quartz-syenite breccia Uruguay
spellingShingle	Neoproterozoic Peperites Playa Hermosa Formation Quartz-syenite breccia Uruguay Sánchez Bettucci, Leda Koukharsky, Magdalena María Luisa Pazos, Pablo Jose Neoproterozoic subaqueous extrusive-intrusive rocks in the Playa Hermosa Formation in Uruguay: Regional and stratigraphic significance
topic_facet	Neoproterozoic Peperites Playa Hermosa Formation Quartz-syenite breccia Uruguay
description	Volcanic rocks in southern Uruguay are linked to an extensional tectonic regime related to the post-collisional Brasiliano-Pan African orogenic cycle. The ca 580 Ma magmatic event is recorded in the Playa Hermosa Formation. In the upper section of this formation several units were defined. The basal unit is a quartz-syenite brecciated deposit, interpreted as the result of explosive episodes of shallow plutonic quartz-syenite intrusion with signs of hydrothermal alteration. Sedimentary and basaltic lithoclasts are occasionally present in the breccia, implying the emplacement of basalts before of that magmatic event. The middle unit is composed of trachytic hyaloclastites. Local distribution and textural evidence indicate that trachytic volcanic pulses have been followed by an explosive event that produced brecciated deposits. The upper unit of the studied sequence is composed of basalts with thin sedimentary intercalations. Most of the outcropping basalts display the typical micro- and macro-features of hyaloclastites; distinctive of extrusions occurred in wet sediments previous to lithification. Basaltic feeder dikes are common in the lower unit. The study of flow structures in the quartz-syenite brecciated deposits led to the recognition of two basaltic inputs. Such differences are related to the intensity of chloritic alteration, which would be related to water contamination. Basaltic peperites are one of the most impressive features of the Playa Hermosa Formation. Hyaloclastites and peperites largely represented among the studied volcanic rocks, and devitrification textures are all evidences of magma/seawater interactions. In the basaltic fragments of the peperites well preserved orange palagonite appears, while the sandstone fractions have lithic clasts of felsic volcanic rocks, such as rhyolitic lavas with perlitic cracks and lithophysae-like structures. Palagonite chemical analyses suggest marine environment and, at the same time, it proves that the studied section lacks of regional metamorphism. The felsic volcanic lithoclasts contained in sandstones could be related to the felsic volcanic lobes intercalations. The studied magmatic event is important in order to formulate correlations with other Neoproterozoic units distributed around the Dom Feliciano belt, like Camaquã and Campo Alegre basins (Brazil), and in the Kaoko belt (NW Namibia) in Africa. Also, Playa Hermosa Formation presents glacigenic features that are well documented, and reinforce the volcanism around 580 Ma in the Rio de la Plata Craton. © 2009 International Association for Gondwana Research.
author	Sánchez Bettucci, Leda Koukharsky, Magdalena María Luisa Pazos, Pablo Jose
author_facet	Sánchez Bettucci, Leda Koukharsky, Magdalena María Luisa Pazos, Pablo Jose
author_sort	Sánchez Bettucci, Leda
title	Neoproterozoic subaqueous extrusive-intrusive rocks in the Playa Hermosa Formation in Uruguay: Regional and stratigraphic significance
title_short	Neoproterozoic subaqueous extrusive-intrusive rocks in the Playa Hermosa Formation in Uruguay: Regional and stratigraphic significance
title_full	Neoproterozoic subaqueous extrusive-intrusive rocks in the Playa Hermosa Formation in Uruguay: Regional and stratigraphic significance
title_fullStr	Neoproterozoic subaqueous extrusive-intrusive rocks in the Playa Hermosa Formation in Uruguay: Regional and stratigraphic significance
title_full_unstemmed	Neoproterozoic subaqueous extrusive-intrusive rocks in the Playa Hermosa Formation in Uruguay: Regional and stratigraphic significance
title_sort	neoproterozoic subaqueous extrusive-intrusive rocks in the playa hermosa formation in uruguay: regional and stratigraphic significance
publishDate	2009
url	https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_1342937X_v16_n1_p134_SanchezBettucci http://hdl.handle.net/20.500.12110/paper_1342937X_v16_n1_p134_SanchezBettucci
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Neoproterozoic subaqueous extrusive-intrusive rocks in the Playa Hermosa Formation in Uruguay: Regional and stratigraphic significance

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