The Ordovician Quebrada Grande Formation, Cordón de Lila (Antofagasta Region, northern Chile): stratigraphicand paleogeographic significance

The Cordón de Lila is located immediately to the south of the Salar de Atacama, in northern Chile. The geology of the Cordón de Lila is characterized by extensive outcrops of Early Paleozoic volcanic and sedimentary rocks (Cordón de Lila Igneous and Sedimentary Complex; CISL) that form the 'Arc...

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Autores principales:	González,Javier, Niemeyer,Hans, Benedetto,Juan L, Brussa,Edsel D
Lenguaje:	English
Publicado:	Servicio Nacional de Geología y Minería (SERNAGEOMIN) 2007
Materias:	Ordovician Brachiopods Graptolites Arequipa-Antofalla Terrane Cordón de Lila northern Chile
Acceso en línea:	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-02082007000200006
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spelling	oai:scielo:S0716-020820070002000062007-09-07The Ordovician Quebrada Grande Formation, Cordón de Lila (Antofagasta Region, northern Chile): stratigraphicand paleogeographic significanceGonzález,JavierNiemeyer,HansBenedetto,Juan LBrussa,Edsel D Ordovician Brachiopods Graptolites Arequipa-Antofalla Terrane Cordón de Lila northern Chile The Cordón de Lila is located immediately to the south of the Salar de Atacama, in northern Chile. The geology of the Cordón de Lila is characterized by extensive outcrops of Early Paleozoic volcanic and sedimentary rocks (Cordón de Lila Igneous and Sedimentary Complex; CISL) that form the 'Arco magmático occidental' (AMO) which is intruded by a multiple suite of Middle Ordovician to Lower Silurian granitoids. In this contribution we report the results of a sedimentological and paleontological study of a recently discovered 1,600 m thick marine Ordovician sedimentary sequence (Quebrada Grande Formation) which unconformably overlies the CISL. The Quebrada Grande Formation comprises three mayor facies associations. In stratigrafic order, these facies associations are: matrix-supported conglomerates (1), interbedded sandstones and siltstones (2) and clast-supported conglomerates (3). Facies association (1) is interpreted as debris flow deposits accumulated in a proximal marine fan-delta setting while the overlying sandstones and siltstones facies (2) represent open-marine platform deposits. Clast-supported conglomerates (3) are the record of high-energy sedimentary episodes during which coarse sediments reached the distal part of the fan-delta. The detrital fraction of the Quebrada Grande Formation is derived from the erosion of the Cambrian?-Lower Ordovician? CISL volcanic arc, the plutonio roots of the arc and its continental basement. The age of this formation is well constrained by the occurrence of brachiopods (Paralenorthis sp., Monorthis transversa Benedetto, and Mollesella? sp.) near the base and graptolites (Tetragraptus sp. and Cryptograptus? sp.) towards the middle of the succession. Both brachiopods and graptolites indicate an Arenigian to early Llanvirnian (Darriwilian) age. The brachiopod assemblage from Cordón de Lila displays affinities with the Famatina basin fauna of western Argentina. The absence of taxa in common between the AMO and the nearby 'Faja Eruptiva de la Puna Occidental' (FEPO) of NW Argentina may result from some kind of environmental barrier or some geographic separation from the Gondwana margin. According to the latter hypothesis, the Quebrada Grande succession developed on the allochtonous Arequipa-Antofalla Terraneinfo:eu-repo/semantics/openAccessServicio Nacional de Geología y Minería (SERNAGEOMIN)Revista geológica de Chile v.34 n.2 20072007-07-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-02082007000200006en10.4067/S0716-02082007000200006
institution	Scielo Chile
collection	Scielo Chile
language	English
topic	Ordovician Brachiopods Graptolites Arequipa-Antofalla Terrane Cordón de Lila northern Chile
spellingShingle	Ordovician Brachiopods Graptolites Arequipa-Antofalla Terrane Cordón de Lila northern Chile González,Javier Niemeyer,Hans Benedetto,Juan L Brussa,Edsel D The Ordovician Quebrada Grande Formation, Cordón de Lila (Antofagasta Region, northern Chile): stratigraphicand paleogeographic significance
description	The Cordón de Lila is located immediately to the south of the Salar de Atacama, in northern Chile. The geology of the Cordón de Lila is characterized by extensive outcrops of Early Paleozoic volcanic and sedimentary rocks (Cordón de Lila Igneous and Sedimentary Complex; CISL) that form the 'Arco magmático occidental' (AMO) which is intruded by a multiple suite of Middle Ordovician to Lower Silurian granitoids. In this contribution we report the results of a sedimentological and paleontological study of a recently discovered 1,600 m thick marine Ordovician sedimentary sequence (Quebrada Grande Formation) which unconformably overlies the CISL. The Quebrada Grande Formation comprises three mayor facies associations. In stratigrafic order, these facies associations are: matrix-supported conglomerates (1), interbedded sandstones and siltstones (2) and clast-supported conglomerates (3). Facies association (1) is interpreted as debris flow deposits accumulated in a proximal marine fan-delta setting while the overlying sandstones and siltstones facies (2) represent open-marine platform deposits. Clast-supported conglomerates (3) are the record of high-energy sedimentary episodes during which coarse sediments reached the distal part of the fan-delta. The detrital fraction of the Quebrada Grande Formation is derived from the erosion of the Cambrian?-Lower Ordovician? CISL volcanic arc, the plutonio roots of the arc and its continental basement. The age of this formation is well constrained by the occurrence of brachiopods (Paralenorthis sp., Monorthis transversa Benedetto, and Mollesella? sp.) near the base and graptolites (Tetragraptus sp. and Cryptograptus? sp.) towards the middle of the succession. Both brachiopods and graptolites indicate an Arenigian to early Llanvirnian (Darriwilian) age. The brachiopod assemblage from Cordón de Lila displays affinities with the Famatina basin fauna of western Argentina. The absence of taxa in common between the AMO and the nearby 'Faja Eruptiva de la Puna Occidental' (FEPO) of NW Argentina may result from some kind of environmental barrier or some geographic separation from the Gondwana margin. According to the latter hypothesis, the Quebrada Grande succession developed on the allochtonous Arequipa-Antofalla Terrane
author	González,Javier Niemeyer,Hans Benedetto,Juan L Brussa,Edsel D
author_facet	González,Javier Niemeyer,Hans Benedetto,Juan L Brussa,Edsel D
author_sort	González,Javier
title	The Ordovician Quebrada Grande Formation, Cordón de Lila (Antofagasta Region, northern Chile): stratigraphicand paleogeographic significance
title_short	The Ordovician Quebrada Grande Formation, Cordón de Lila (Antofagasta Region, northern Chile): stratigraphicand paleogeographic significance
title_full	The Ordovician Quebrada Grande Formation, Cordón de Lila (Antofagasta Region, northern Chile): stratigraphicand paleogeographic significance
title_fullStr	The Ordovician Quebrada Grande Formation, Cordón de Lila (Antofagasta Region, northern Chile): stratigraphicand paleogeographic significance
title_full_unstemmed	The Ordovician Quebrada Grande Formation, Cordón de Lila (Antofagasta Region, northern Chile): stratigraphicand paleogeographic significance
title_sort	ordovician quebrada grande formation, cordón de lila (antofagasta region, northern chile): stratigraphicand paleogeographic significance
publisher	Servicio Nacional de Geología y Minería (SERNAGEOMIN)
publishDate	2007
url	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-02082007000200006
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The Ordovician Quebrada Grande Formation, Cordón de Lila (Antofagasta Region, northern Chile): stratigraphicand paleogeographic significance

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