Paleomagnetic study of upper Miocene rocks from northern Chile: Implications for the origin of late Miocene-Recent tectonic rotations in the southern Central Andes

Paleomagnetic studies in the southern Central Andes have shown the widespread presence of clockwise vertical-axis rotations. Rock units sampled in these studies, however, are heterogeneously distributed in stratigraphic age with most paleomagnetic data from northern Chile being from Mesozoic and low...

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Autores principales:	Somoza, R., Singer, S., Tomlinson, A.
Formato:	JOUR
Materias:	block rotation Miocene paleomagnetism tectonics Chile
Acceso en línea:	http://hdl.handle.net/20.500.12110/paper_21699313_v104_nB10_p22923_Somoza
Aporte de:	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires

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spelling	todo:paper_21699313_v104_nB10_p22923_Somoza2023-10-03T16:39:55Z Paleomagnetic study of upper Miocene rocks from northern Chile: Implications for the origin of late Miocene-Recent tectonic rotations in the southern Central Andes Somoza, R. Singer, S. Tomlinson, A. block rotation Miocene paleomagnetism tectonics Chile Paleomagnetic studies in the southern Central Andes have shown the widespread presence of clockwise vertical-axis rotations. Rock units sampled in these studies, however, are heterogeneously distributed in stratigraphic age with most paleomagnetic data from northern Chile being from Mesozoic and lower Tertiary rocks, whereas most data in the southern Altiplano, Puna, and Cordillera Oriental are from upper Tertiary rocks. In this paper we present the results of a paleomagnetic study on upper Miocene sedimentary rocks and ignimbrites from the Precordillera of northern Chile (at 22° S). These rocks are coeval with the initiation of crustal shortening in the eastern foreland fold-thrust belt which some tectonic models relate to oroclinal rotation of northern Chile. Primary magnetizations in rocks from widely distributed sites in two ignimbrites indicate that no relative rotations have occurred between sites, suggesting the study area has acted as a single coherent block with respect to vertical-axis rotational deformation. Although minor inadequate sampling of paleosecular variation can affect our data set, its time-averaged paleomagnetic direction is indistinguishable from the expected late Miocene reference direction indicating no paleomagnetically significant rotation of the study area since circa 11 Ma. This suggests that late Miocene-Recent oroclinal rotation of the northern Chilean forearc, if present, must be either very low or nonuniform. A direct implication of this result is that much of the unquestionable tectonic rotations detected from upper Miocene rocks in the southern Central Andes is of local origin. Available structural data permit us to relate several of these rotations with shear in dextral transfer zones in the foreland thrust belt on the east side of the Andes. Copyright 1999 by the American Geophysical Union. Fil:Somoza, R. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Singer, S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_21699313_v104_nB10_p22923_Somoza
institution	Universidad de Buenos Aires
institution_str	I-28
repository_str	R-134
collection	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic	block rotation Miocene paleomagnetism tectonics Chile
spellingShingle	block rotation Miocene paleomagnetism tectonics Chile Somoza, R. Singer, S. Tomlinson, A. Paleomagnetic study of upper Miocene rocks from northern Chile: Implications for the origin of late Miocene-Recent tectonic rotations in the southern Central Andes
topic_facet	block rotation Miocene paleomagnetism tectonics Chile
description	Paleomagnetic studies in the southern Central Andes have shown the widespread presence of clockwise vertical-axis rotations. Rock units sampled in these studies, however, are heterogeneously distributed in stratigraphic age with most paleomagnetic data from northern Chile being from Mesozoic and lower Tertiary rocks, whereas most data in the southern Altiplano, Puna, and Cordillera Oriental are from upper Tertiary rocks. In this paper we present the results of a paleomagnetic study on upper Miocene sedimentary rocks and ignimbrites from the Precordillera of northern Chile (at 22° S). These rocks are coeval with the initiation of crustal shortening in the eastern foreland fold-thrust belt which some tectonic models relate to oroclinal rotation of northern Chile. Primary magnetizations in rocks from widely distributed sites in two ignimbrites indicate that no relative rotations have occurred between sites, suggesting the study area has acted as a single coherent block with respect to vertical-axis rotational deformation. Although minor inadequate sampling of paleosecular variation can affect our data set, its time-averaged paleomagnetic direction is indistinguishable from the expected late Miocene reference direction indicating no paleomagnetically significant rotation of the study area since circa 11 Ma. This suggests that late Miocene-Recent oroclinal rotation of the northern Chilean forearc, if present, must be either very low or nonuniform. A direct implication of this result is that much of the unquestionable tectonic rotations detected from upper Miocene rocks in the southern Central Andes is of local origin. Available structural data permit us to relate several of these rotations with shear in dextral transfer zones in the foreland thrust belt on the east side of the Andes. Copyright 1999 by the American Geophysical Union.
format	JOUR
author	Somoza, R. Singer, S. Tomlinson, A.
author_facet	Somoza, R. Singer, S. Tomlinson, A.
author_sort	Somoza, R.
title	Paleomagnetic study of upper Miocene rocks from northern Chile: Implications for the origin of late Miocene-Recent tectonic rotations in the southern Central Andes
title_short	Paleomagnetic study of upper Miocene rocks from northern Chile: Implications for the origin of late Miocene-Recent tectonic rotations in the southern Central Andes
title_full	Paleomagnetic study of upper Miocene rocks from northern Chile: Implications for the origin of late Miocene-Recent tectonic rotations in the southern Central Andes
title_fullStr	Paleomagnetic study of upper Miocene rocks from northern Chile: Implications for the origin of late Miocene-Recent tectonic rotations in the southern Central Andes
title_full_unstemmed	Paleomagnetic study of upper Miocene rocks from northern Chile: Implications for the origin of late Miocene-Recent tectonic rotations in the southern Central Andes
title_sort	paleomagnetic study of upper miocene rocks from northern chile: implications for the origin of late miocene-recent tectonic rotations in the southern central andes
url	http://hdl.handle.net/20.500.12110/paper_21699313_v104_nB10_p22923_Somoza
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Paleomagnetic study of upper Miocene rocks from northern Chile: Implications for the origin of late Miocene-Recent tectonic rotations in the southern Central Andes

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