Paleomagnetism of the Mid-Tertiary Ayacara Formation, southern Chile: Counterclockwise rotation in a dextral shear zone

C. Rojas, M. E. Beck, R. F. Burmester, J. Cembrano, F. Hervé

Resultado de la investigación: Article

27 Citas (Scopus)

Resumen

Relative motions of the southern Chilean forearc are assessed through a paleomagnetic study of teh Eocene-Miocene Ayacara Formation. This marine volcaniclastic unit was studied at three localities, all immediately west of the Liquiñe-Ofqui fault zone (LOFZ), a 1000-km-long, NS-trending intracontinental shear zone with probable Cenozoic right-lateral displacement. A paleomagnetic pole (74.8S; 44.0E; A-95, 8.5°) was calculated by combining 11 site-mean VGP from the Ayacara Fm. with three sites from the nearby Oligocene Cocotue Beach basalts (previously published). When compared with a 20-40 Ma North American cratonic pole rotated into the South American reference framework this pole implies counterclockwise rotation of 14.6±11.8. We speculate that this counterclockwise rotation results from processes that tend to impel a detached sliver of continental crust northward along the continental margin, against a buttress. In our model, northward displacement of the trailing edge of the sliver is accomplished by segmenting the sliver into lens-shaped blocks which rotate counterclockwise as they move northward. The geometry of the LOFZ clearly supports this model, which may have application to other buttressed strike-slip fault zones.

Idioma originalEnglish
Páginas (desde-hasta)45-56
Número de páginas12
PublicaciónJournal of South American Earth Sciences
Volumen7
N.º1
DOI
EstadoPublished - 1 ene 1994

Huella dactilar

paleomagnetism
shear zone
fault zone
strike-slip fault
continental crust
Oligocene
continental margin
Eocene
beach
basalt
Miocene
geometry

ASJC Scopus subject areas

  • Geology
  • Earth-Surface Processes

Citar esto

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abstract = "Relative motions of the southern Chilean forearc are assessed through a paleomagnetic study of teh Eocene-Miocene Ayacara Formation. This marine volcaniclastic unit was studied at three localities, all immediately west of the Liqui{\~n}e-Ofqui fault zone (LOFZ), a 1000-km-long, NS-trending intracontinental shear zone with probable Cenozoic right-lateral displacement. A paleomagnetic pole (74.8S; 44.0E; A-95, 8.5°) was calculated by combining 11 site-mean VGP from the Ayacara Fm. with three sites from the nearby Oligocene Cocotue Beach basalts (previously published). When compared with a 20-40 Ma North American cratonic pole rotated into the South American reference framework this pole implies counterclockwise rotation of 14.6±11.8. We speculate that this counterclockwise rotation results from processes that tend to impel a detached sliver of continental crust northward along the continental margin, against a buttress. In our model, northward displacement of the trailing edge of the sliver is accomplished by segmenting the sliver into lens-shaped blocks which rotate counterclockwise as they move northward. The geometry of the LOFZ clearly supports this model, which may have application to other buttressed strike-slip fault zones.",
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Paleomagnetism of the Mid-Tertiary Ayacara Formation, southern Chile : Counterclockwise rotation in a dextral shear zone. / Rojas, C.; Beck, M. E.; Burmester, R. F.; Cembrano, J.; Hervé, F.

En: Journal of South American Earth Sciences, Vol. 7, N.º 1, 01.01.1994, p. 45-56.

Resultado de la investigación: Article

TY - JOUR

T1 - Paleomagnetism of the Mid-Tertiary Ayacara Formation, southern Chile

T2 - Counterclockwise rotation in a dextral shear zone

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AU - Beck, M. E.

AU - Burmester, R. F.

AU - Cembrano, J.

AU - Hervé, F.

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N2 - Relative motions of the southern Chilean forearc are assessed through a paleomagnetic study of teh Eocene-Miocene Ayacara Formation. This marine volcaniclastic unit was studied at three localities, all immediately west of the Liquiñe-Ofqui fault zone (LOFZ), a 1000-km-long, NS-trending intracontinental shear zone with probable Cenozoic right-lateral displacement. A paleomagnetic pole (74.8S; 44.0E; A-95, 8.5°) was calculated by combining 11 site-mean VGP from the Ayacara Fm. with three sites from the nearby Oligocene Cocotue Beach basalts (previously published). When compared with a 20-40 Ma North American cratonic pole rotated into the South American reference framework this pole implies counterclockwise rotation of 14.6±11.8. We speculate that this counterclockwise rotation results from processes that tend to impel a detached sliver of continental crust northward along the continental margin, against a buttress. In our model, northward displacement of the trailing edge of the sliver is accomplished by segmenting the sliver into lens-shaped blocks which rotate counterclockwise as they move northward. The geometry of the LOFZ clearly supports this model, which may have application to other buttressed strike-slip fault zones.

AB - Relative motions of the southern Chilean forearc are assessed through a paleomagnetic study of teh Eocene-Miocene Ayacara Formation. This marine volcaniclastic unit was studied at three localities, all immediately west of the Liquiñe-Ofqui fault zone (LOFZ), a 1000-km-long, NS-trending intracontinental shear zone with probable Cenozoic right-lateral displacement. A paleomagnetic pole (74.8S; 44.0E; A-95, 8.5°) was calculated by combining 11 site-mean VGP from the Ayacara Fm. with three sites from the nearby Oligocene Cocotue Beach basalts (previously published). When compared with a 20-40 Ma North American cratonic pole rotated into the South American reference framework this pole implies counterclockwise rotation of 14.6±11.8. We speculate that this counterclockwise rotation results from processes that tend to impel a detached sliver of continental crust northward along the continental margin, against a buttress. In our model, northward displacement of the trailing edge of the sliver is accomplished by segmenting the sliver into lens-shaped blocks which rotate counterclockwise as they move northward. The geometry of the LOFZ clearly supports this model, which may have application to other buttressed strike-slip fault zones.

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