Osagids-types oncoids from La Manga Formation and their paleoecological significance, La Vaina Creek, Mendoza

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Microbial oncoids have been found in the Oxfordian limestones of the La Manga Formation in the La Vaina section at Potimalal River, Mendoza province. The oncoids ocurr either in packstone or floatstone-rudstone or are scattered in the wackestones. They are mostly elliptical, ameboidal and subordinat...

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Detalles Bibliográficos
Autores principales: Palma, R.M., Bressan, G.S., Kietzmann, D.A.
Formato: Artículo publishedVersion
Lenguaje:Inglés
Publicado: 2007
Materias:
Jurassic
La Manga Formation
Oncoids
bivalve
echinoderm
growth rate
lamination
limestone
microorganism
micropaleontology
morphology
oncolite
paleoecology
paleoenvironment
sedimentation rate
Argentina
Mendoza
South America
Bivalvia
Echinodermata
Echinoida
Foraminifera
Mollusca
Nubeculariidae
Serpulidae
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_00044822_v62_n1_p116_Palma
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling paperaa:paper_00044822_v62_n1_p116_Palma2023-06-12T16:40:11Z Osagids-types oncoids from La Manga Formation and their paleoecological significance, La Vaina Creek, Mendoza Rev. Asoc. Geol. Argent. 2007;62(1):116-123 Palma, R.M. Bressan, G.S. Kietzmann, D.A. Jurassic La Manga Formation Oncoids bivalve echinoderm growth rate Jurassic lamination limestone microorganism micropaleontology morphology oncolite paleoecology paleoenvironment sedimentation rate Argentina Mendoza South America Bivalvia Echinodermata Echinoida Foraminifera Mollusca Nubeculariidae Serpulidae Microbial oncoids have been found in the Oxfordian limestones of the La Manga Formation in the La Vaina section at Potimalal River, Mendoza province. The oncoids ocurr either in packstone or floatstone-rudstone or are scattered in the wackestones. They are mostly elliptical, ameboidal and subordinately spherical in shape. Different types of oncoids were recognized, according to their features of envelopes: (1) micritic laminations, (2) grumose laminations, and (3) organism-bearing laminations. Molluscs and echinoid fragments, peloids, and intraclasts acted as oncoid nuclei. Laminae follow the shape of nuclei, especially in the inner zone of the cortices. However, in the outer zones the laminae contain encrusting organisms dominated by nubeculariids and serpulids. Some oncoids, especially the ameboidal or elliptical forms, are characterized by multiple nuclei, represented by small oncoids. The oncoids are associated with bivalves, echinoderms, forams, and serpulids. The fauna is indicative of calm, shallow conditions and the excellent preservation of echinoderms suggests minimal transport prior to burial. Growth histories are in evidence. The oncoids grew in a shallow, low energy, slightly to moderate agitated subtidal normal sea water environment. The limited rolling growth oncoids was probably accompanished by intermittent currents that reoriented the oncoids parallel to stratification. The discontinuous organisms-bearing laminations reflect periods of non-agitation and litification, which facilitated the growth of encrusting organisms on static oncoid particles during a period of low sedimentation rate. Deposition of the oncoid-bearing limestones took place during shallowing of the carbonate interval and associated with emersion, subaerial exposition and paleokarst as consequence of sea level fluctuations. Fil:Palma, R.M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Bressan, G.S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Kietzmann, D.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2007 info:eu-repo/semantics/article info:ar-repo/semantics/artículo info:eu-repo/semantics/publishedVersion application/pdf eng info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_00044822_v62_n1_p116_Palma
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
language Inglés
orig_language_str_mv eng
topic Jurassic
La Manga Formation
Oncoids
bivalve
echinoderm
growth rate
Jurassic
lamination
limestone
microorganism
micropaleontology
morphology
oncolite
paleoecology
paleoenvironment
sedimentation rate
Argentina
Mendoza
South America
Bivalvia
Echinodermata
Echinoida
Foraminifera
Mollusca
Nubeculariidae
Serpulidae
spellingShingle Jurassic
La Manga Formation
Oncoids
bivalve
echinoderm
growth rate
Jurassic
lamination
limestone
microorganism
micropaleontology
morphology
oncolite
paleoecology
paleoenvironment
sedimentation rate
Argentina
Mendoza
South America
Bivalvia
Echinodermata
Echinoida
Foraminifera
Mollusca
Nubeculariidae
Serpulidae
Palma, R.M.
Bressan, G.S.
Kietzmann, D.A.
Osagids-types oncoids from La Manga Formation and their paleoecological significance, La Vaina Creek, Mendoza
topic_facet Jurassic
La Manga Formation
Oncoids
bivalve
echinoderm
growth rate
Jurassic
lamination
limestone
microorganism
micropaleontology
morphology
oncolite
paleoecology
paleoenvironment
sedimentation rate
Argentina
Mendoza
South America
Bivalvia
Echinodermata
Echinoida
Foraminifera
Mollusca
Nubeculariidae
Serpulidae
description Microbial oncoids have been found in the Oxfordian limestones of the La Manga Formation in the La Vaina section at Potimalal River, Mendoza province. The oncoids ocurr either in packstone or floatstone-rudstone or are scattered in the wackestones. They are mostly elliptical, ameboidal and subordinately spherical in shape. Different types of oncoids were recognized, according to their features of envelopes: (1) micritic laminations, (2) grumose laminations, and (3) organism-bearing laminations. Molluscs and echinoid fragments, peloids, and intraclasts acted as oncoid nuclei. Laminae follow the shape of nuclei, especially in the inner zone of the cortices. However, in the outer zones the laminae contain encrusting organisms dominated by nubeculariids and serpulids. Some oncoids, especially the ameboidal or elliptical forms, are characterized by multiple nuclei, represented by small oncoids. The oncoids are associated with bivalves, echinoderms, forams, and serpulids. The fauna is indicative of calm, shallow conditions and the excellent preservation of echinoderms suggests minimal transport prior to burial. Growth histories are in evidence. The oncoids grew in a shallow, low energy, slightly to moderate agitated subtidal normal sea water environment. The limited rolling growth oncoids was probably accompanished by intermittent currents that reoriented the oncoids parallel to stratification. The discontinuous organisms-bearing laminations reflect periods of non-agitation and litification, which facilitated the growth of encrusting organisms on static oncoid particles during a period of low sedimentation rate. Deposition of the oncoid-bearing limestones took place during shallowing of the carbonate interval and associated with emersion, subaerial exposition and paleokarst as consequence of sea level fluctuations.
format Artículo
Artículo
publishedVersion
author Palma, R.M.
Bressan, G.S.
Kietzmann, D.A.
author_facet Palma, R.M.
Bressan, G.S.
Kietzmann, D.A.
author_sort Palma, R.M.
title Osagids-types oncoids from La Manga Formation and their paleoecological significance, La Vaina Creek, Mendoza
title_short Osagids-types oncoids from La Manga Formation and their paleoecological significance, La Vaina Creek, Mendoza
title_full Osagids-types oncoids from La Manga Formation and their paleoecological significance, La Vaina Creek, Mendoza
title_fullStr Osagids-types oncoids from La Manga Formation and their paleoecological significance, La Vaina Creek, Mendoza
title_full_unstemmed Osagids-types oncoids from La Manga Formation and their paleoecological significance, La Vaina Creek, Mendoza
title_sort osagids-types oncoids from la manga formation and their paleoecological significance, la vaina creek, mendoza
publishDate 2007
url http://hdl.handle.net/20.500.12110/paper_00044822_v62_n1_p116_Palma
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