Late Paleozoic transpression in Buenos Aires and northeast Patagonia ranges, Argentina

Paleozoic sediments are present in three regions in eastern central Argintina: 1) the Sierras Australes of Buenos Aires, 2) Sierras Septentrionales of Buenos Aires and 3) Northeast Patagonia. All of these deposits share a common deformational imprint imparted by late Paleozoic Gondwanan deformation....

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Guardado en:
Detalles Bibliográficos
Publicado: 1997
Materias:
Palaeozoic
transpression
Argentina
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_08959811_v10_n5-6_p389_Rossello
http://hdl.handle.net/20.500.12110/paper_08959811_v10_n5-6_p389_Rossello
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id paper:paper_08959811_v10_n5-6_p389_Rossello
record_format dspace
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Palaeozoic
transpression
Argentina
spellingShingle Palaeozoic
transpression
Argentina
Late Paleozoic transpression in Buenos Aires and northeast Patagonia ranges, Argentina
topic_facet Palaeozoic
transpression
Argentina
description Paleozoic sediments are present in three regions in eastern central Argintina: 1) the Sierras Australes of Buenos Aires, 2) Sierras Septentrionales of Buenos Aires and 3) Northeast Patagonia. All of these deposits share a common deformational imprint imparted by late Paleozoic Gondwanan deformation. Exposures of these rocks are scattered, variably deformed, and isolated by younger sediments deposited in basins related to the Mesozoic through Tertiary opening of the South Atlantic such as the offshore Colorado Basin. The Sierras Australes of Buenos Aires outcrops are the best preserved. They are mostly located along the Sierras Australes foldbelt, with minor outliers distributed in the adjacent Claromec-basin. The Tunas Formation (early-early late? Permian) is the uppermost unit of the Pillahuinco Group (late Carboniferous-Permian) and is crucial to the understanding of the tectono-sedimentary evolution of the region during the late Paleozoic. The underlying units of the Pillahuinco Group (Sauce Grande, Piedra Azul and Bonete Formations) exhibit a depositional and compositional history characterized by glaciomarine sedimentation and postglacial transgression. They are also characterized by rather uniform quartz-rich compositions indicative of a cratonic provenance from the La Plata craton to the NE. In contrast, the sandstone-rich Tunas Formation has low quartz contents, and abundant volcanic and metasedimentary fragments; paleocurrents are consistently from the SW. Glass-rich tuffs are interbedded with sandstone in the upper half of the Tunas Formation. The age of the deformation in the Sierras Australes is Permian and early-middle Triassic. This is based on metamorphic events indicated by formation of illite at 282 ± 3 Ma, 273 ± 8 Ma, 265 ± 3 Ma, and 260 ± 3 Ma (K/Ar illite) in the Silurian Curamalal Group. Evidence of syntectonic magmatism is provided by a radiometric date of 245 ± 12 Ma (K/Ar hornblende) for the Lopez Lecube Granite, immediately west of the Sierras Australes. In the Sierras Septentrionales of Buenos Aires, Precambrian through early Paleozoic deposits of La Tinta, Sierras Bayas, Las Aguilas and Balcarce Formations rest on Precambrian crystalline basement of the La Plata craton. These exposed rocks are affected by subordinate, right lateral wrench faulting; some thrusting indicates tectonic transport toward the NE. In northeast Patagonia (Sierra Grande region) synkinematic deformation of early Permian (261 ± 5 Ma, Rb/Sr whole rock) age has been identified in Silurian metasediments of the Sierra grande Formation. Bands of deformation in Sierra Grande quartzites indicate right lateral wrenching in a N-S direction. Contraction in a NE-SW direction is evidenced by folding. Three stages of tectonic evolution can be discerned for the above regions: 1) Early Paleozoic platform sedimentation, punctuated by episodes of accelerated subsidence during the Silurian and early Devonian, as shown by transgressive episodes, 2) late Paleozoic sedimentation and deformation, and 3) Meso-Cenozoic extensional inversion due to the South Atlantic opening. The late Paleozoic sedimentation and deformation (stage 2) includes late Carboniferous-earliest Permian glacial deposits of the Sierras Australes and Colorado offshore baisn, deposited during an initial phase of extension, and cratonward foreland subsidence triggered sedimentation of the synorogenic deposits of the Permian Tunas Formation. Tuffs are intercalated in the upper half of this unit. These tuffs are associated with the silicic volcanism along the Andes and Patagonia (Choiyoi magmatic province) that peaked between the late early Permian and late Permian. Likewise, the first widespread appearance of tuffs in the Karoo basin is in the Whitehill Formation, of late early Permian (260 Ma) age. The deformation described in this paper can be considered as part of a large scale intracontinental deformation in SW Gondwanaland inboard of an Andean-type compressive margin. This deformation is characterized by transpression (right lateral wrenching) combined with overthrusting to the NE and N-S horizontal contraction.
title Late Paleozoic transpression in Buenos Aires and northeast Patagonia ranges, Argentina
title_short Late Paleozoic transpression in Buenos Aires and northeast Patagonia ranges, Argentina
title_full Late Paleozoic transpression in Buenos Aires and northeast Patagonia ranges, Argentina
title_fullStr Late Paleozoic transpression in Buenos Aires and northeast Patagonia ranges, Argentina
title_full_unstemmed Late Paleozoic transpression in Buenos Aires and northeast Patagonia ranges, Argentina
title_sort late paleozoic transpression in buenos aires and northeast patagonia ranges, argentina
publishDate 1997
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_08959811_v10_n5-6_p389_Rossello
http://hdl.handle.net/20.500.12110/paper_08959811_v10_n5-6_p389_Rossello
_version_ 1768545195429724160
spelling paper:paper_08959811_v10_n5-6_p389_Rossello2023-06-08T15:48:06Z Late Paleozoic transpression in Buenos Aires and northeast Patagonia ranges, Argentina Palaeozoic transpression Argentina Paleozoic sediments are present in three regions in eastern central Argintina: 1) the Sierras Australes of Buenos Aires, 2) Sierras Septentrionales of Buenos Aires and 3) Northeast Patagonia. All of these deposits share a common deformational imprint imparted by late Paleozoic Gondwanan deformation. Exposures of these rocks are scattered, variably deformed, and isolated by younger sediments deposited in basins related to the Mesozoic through Tertiary opening of the South Atlantic such as the offshore Colorado Basin. The Sierras Australes of Buenos Aires outcrops are the best preserved. They are mostly located along the Sierras Australes foldbelt, with minor outliers distributed in the adjacent Claromec-basin. The Tunas Formation (early-early late? Permian) is the uppermost unit of the Pillahuinco Group (late Carboniferous-Permian) and is crucial to the understanding of the tectono-sedimentary evolution of the region during the late Paleozoic. The underlying units of the Pillahuinco Group (Sauce Grande, Piedra Azul and Bonete Formations) exhibit a depositional and compositional history characterized by glaciomarine sedimentation and postglacial transgression. They are also characterized by rather uniform quartz-rich compositions indicative of a cratonic provenance from the La Plata craton to the NE. In contrast, the sandstone-rich Tunas Formation has low quartz contents, and abundant volcanic and metasedimentary fragments; paleocurrents are consistently from the SW. Glass-rich tuffs are interbedded with sandstone in the upper half of the Tunas Formation. The age of the deformation in the Sierras Australes is Permian and early-middle Triassic. This is based on metamorphic events indicated by formation of illite at 282 ± 3 Ma, 273 ± 8 Ma, 265 ± 3 Ma, and 260 ± 3 Ma (K/Ar illite) in the Silurian Curamalal Group. Evidence of syntectonic magmatism is provided by a radiometric date of 245 ± 12 Ma (K/Ar hornblende) for the Lopez Lecube Granite, immediately west of the Sierras Australes. In the Sierras Septentrionales of Buenos Aires, Precambrian through early Paleozoic deposits of La Tinta, Sierras Bayas, Las Aguilas and Balcarce Formations rest on Precambrian crystalline basement of the La Plata craton. These exposed rocks are affected by subordinate, right lateral wrench faulting; some thrusting indicates tectonic transport toward the NE. In northeast Patagonia (Sierra Grande region) synkinematic deformation of early Permian (261 ± 5 Ma, Rb/Sr whole rock) age has been identified in Silurian metasediments of the Sierra grande Formation. Bands of deformation in Sierra Grande quartzites indicate right lateral wrenching in a N-S direction. Contraction in a NE-SW direction is evidenced by folding. Three stages of tectonic evolution can be discerned for the above regions: 1) Early Paleozoic platform sedimentation, punctuated by episodes of accelerated subsidence during the Silurian and early Devonian, as shown by transgressive episodes, 2) late Paleozoic sedimentation and deformation, and 3) Meso-Cenozoic extensional inversion due to the South Atlantic opening. The late Paleozoic sedimentation and deformation (stage 2) includes late Carboniferous-earliest Permian glacial deposits of the Sierras Australes and Colorado offshore baisn, deposited during an initial phase of extension, and cratonward foreland subsidence triggered sedimentation of the synorogenic deposits of the Permian Tunas Formation. Tuffs are intercalated in the upper half of this unit. These tuffs are associated with the silicic volcanism along the Andes and Patagonia (Choiyoi magmatic province) that peaked between the late early Permian and late Permian. Likewise, the first widespread appearance of tuffs in the Karoo basin is in the Whitehill Formation, of late early Permian (260 Ma) age. The deformation described in this paper can be considered as part of a large scale intracontinental deformation in SW Gondwanaland inboard of an Andean-type compressive margin. This deformation is characterized by transpression (right lateral wrenching) combined with overthrusting to the NE and N-S horizontal contraction. 1997 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_08959811_v10_n5-6_p389_Rossello http://hdl.handle.net/20.500.12110/paper_08959811_v10_n5-6_p389_Rossello

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