Paleomagnetic evidence for a pre-early Eocene (∼ 50 Ma) bending of the Patagonian orocline (Tierra del Fuego, Argentina): Paleogeographic and tectonic implications
The southernmost segment of the Andes of southern Patagonia and Tierra del Fuego forms a ∼ 700 km long orogenic re-entrant with an interlimb angle of ∼ 90° known as Patagonian orocline. No reliable paleomagnetic evidence has been gathered so far to assess whether this great orogenic bend is a primar...
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2010
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0012821X_v289_n1-2_p273_Maffione http://hdl.handle.net/20.500.12110/paper_0012821X_v289_n1-2_p273_Maffione |
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paper:paper_0012821X_v289_n1-2_p273_Maffione2023-06-08T14:35:31Z Paleomagnetic evidence for a pre-early Eocene (∼ 50 Ma) bending of the Patagonian orocline (Tierra del Fuego, Argentina): Paleogeographic and tectonic implications Rossello, Eduardo Antonio Drake Passage Fuegian Andes Magallanes belt paleomagnetism Patagonian orocline tectonics Anisotropy of magnetic susceptibility Antarctica Argentina Drake Passage Early Miocene Global climates Iron sulphide Lower bounds Magallanes belt Magnetic lineations Marine clays Orocline Paleomagnetic evidence Patagonia Relative motion Sampling site South America Strike-slip fault Strike-slip fault systems Tectonic implications Clay minerals Control theory Geomagnetism Glacial geology Iron ores Magnetic anisotropy Magnetic susceptibility Oxide minerals Rotation Structural geology Tectonics bending Cretaceous-Tertiary boundary deformation mechanism displacement Eocene fold and thrust belt iron sulfide magnetic anisotropy magnetite orogeny paleogeography paleomagnetism plate motion reliability analysis seafloor spreading strike-slip fault tectonic setting Argentina Patagonia Tierra del Fuego [(PRV) Argentina] The southernmost segment of the Andes of southern Patagonia and Tierra del Fuego forms a ∼ 700 km long orogenic re-entrant with an interlimb angle of ∼ 90° known as Patagonian orocline. No reliable paleomagnetic evidence has been gathered so far to assess whether this great orogenic bend is a primary arc formed over an articulated paleomargin, or is due to bending of a previously less curved (or rectilinear) chain. Here we report on an extensive paleomagnetic and anisotropy of magnetic susceptibility (AMS) study carried out on 22 sites (298 oriented cores), predominantly sampled in Eocene marine clays from the external Magallanes belt of Tierra del Fuego. Five sites (out of six giving reliable paleomagnetic results) containing magnetite and subordinate iron sulphides yield a positive fold test at the 99% significance level, and document no significant rotation since ∼ 50 Ma. Thus, the Patagonian orocline is either a primary bend, or an orocline formed after Cretaceous-earliest Tertiary rotations. Our data imply that the opening of the Drake Passage between South America and Antarctica (probably causing the onset of Antarctica glaciation and global climate cooling), was definitely not related to the formation of the Patagonian orocline, but was likely the sole consequence of the 32 ± 2 Ma Scotia plate spreading. Well-defined magnetic lineations gathered at 18 sites from the Magallanes belt are sub-parallel to (mostly E-W) local fold axes, while they trend randomly at two sites from the Magallanes foreland. Our and previous AMS data consistently show that the Fuegian Andes were characterized by a N-S compression and northward displacing fold-thrust sheets during Eocene-early Miocene times (50-20 Ma), an unexpected kinematics considering coeval South America-Antarctica relative motion. Both paleomagnetic and AMS data suggest no significant influence from the E-W left-lateral Magallanes-Fagnano strike-slip fault system (MFFS), running a few kilometres south of our sampling sites. We thus speculate that strike-slip fault offset in the Fuegian Andes may range in the lower bound values (∼ 20 km) among those proposed so far. In any case our data exclude any influence of strike-slip tectonics on the genesis of the great orogenic bend called Patagonian orocline. © 2009 Elsevier B.V. All rights reserved. Fil:Rossello, E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2010 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0012821X_v289_n1-2_p273_Maffione http://hdl.handle.net/20.500.12110/paper_0012821X_v289_n1-2_p273_Maffione |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
Drake Passage Fuegian Andes Magallanes belt paleomagnetism Patagonian orocline tectonics Anisotropy of magnetic susceptibility Antarctica Argentina Drake Passage Early Miocene Global climates Iron sulphide Lower bounds Magallanes belt Magnetic lineations Marine clays Orocline Paleomagnetic evidence Patagonia Relative motion Sampling site South America Strike-slip fault Strike-slip fault systems Tectonic implications Clay minerals Control theory Geomagnetism Glacial geology Iron ores Magnetic anisotropy Magnetic susceptibility Oxide minerals Rotation Structural geology Tectonics bending Cretaceous-Tertiary boundary deformation mechanism displacement Eocene fold and thrust belt iron sulfide magnetic anisotropy magnetite orogeny paleogeography paleomagnetism plate motion reliability analysis seafloor spreading strike-slip fault tectonic setting Argentina Patagonia Tierra del Fuego [(PRV) Argentina] |
| spellingShingle |
Drake Passage Fuegian Andes Magallanes belt paleomagnetism Patagonian orocline tectonics Anisotropy of magnetic susceptibility Antarctica Argentina Drake Passage Early Miocene Global climates Iron sulphide Lower bounds Magallanes belt Magnetic lineations Marine clays Orocline Paleomagnetic evidence Patagonia Relative motion Sampling site South America Strike-slip fault Strike-slip fault systems Tectonic implications Clay minerals Control theory Geomagnetism Glacial geology Iron ores Magnetic anisotropy Magnetic susceptibility Oxide minerals Rotation Structural geology Tectonics bending Cretaceous-Tertiary boundary deformation mechanism displacement Eocene fold and thrust belt iron sulfide magnetic anisotropy magnetite orogeny paleogeography paleomagnetism plate motion reliability analysis seafloor spreading strike-slip fault tectonic setting Argentina Patagonia Tierra del Fuego [(PRV) Argentina] Rossello, Eduardo Antonio Paleomagnetic evidence for a pre-early Eocene (∼ 50 Ma) bending of the Patagonian orocline (Tierra del Fuego, Argentina): Paleogeographic and tectonic implications |
| topic_facet |
Drake Passage Fuegian Andes Magallanes belt paleomagnetism Patagonian orocline tectonics Anisotropy of magnetic susceptibility Antarctica Argentina Drake Passage Early Miocene Global climates Iron sulphide Lower bounds Magallanes belt Magnetic lineations Marine clays Orocline Paleomagnetic evidence Patagonia Relative motion Sampling site South America Strike-slip fault Strike-slip fault systems Tectonic implications Clay minerals Control theory Geomagnetism Glacial geology Iron ores Magnetic anisotropy Magnetic susceptibility Oxide minerals Rotation Structural geology Tectonics bending Cretaceous-Tertiary boundary deformation mechanism displacement Eocene fold and thrust belt iron sulfide magnetic anisotropy magnetite orogeny paleogeography paleomagnetism plate motion reliability analysis seafloor spreading strike-slip fault tectonic setting Argentina Patagonia Tierra del Fuego [(PRV) Argentina] |
| description |
The southernmost segment of the Andes of southern Patagonia and Tierra del Fuego forms a ∼ 700 km long orogenic re-entrant with an interlimb angle of ∼ 90° known as Patagonian orocline. No reliable paleomagnetic evidence has been gathered so far to assess whether this great orogenic bend is a primary arc formed over an articulated paleomargin, or is due to bending of a previously less curved (or rectilinear) chain. Here we report on an extensive paleomagnetic and anisotropy of magnetic susceptibility (AMS) study carried out on 22 sites (298 oriented cores), predominantly sampled in Eocene marine clays from the external Magallanes belt of Tierra del Fuego. Five sites (out of six giving reliable paleomagnetic results) containing magnetite and subordinate iron sulphides yield a positive fold test at the 99% significance level, and document no significant rotation since ∼ 50 Ma. Thus, the Patagonian orocline is either a primary bend, or an orocline formed after Cretaceous-earliest Tertiary rotations. Our data imply that the opening of the Drake Passage between South America and Antarctica (probably causing the onset of Antarctica glaciation and global climate cooling), was definitely not related to the formation of the Patagonian orocline, but was likely the sole consequence of the 32 ± 2 Ma Scotia plate spreading. Well-defined magnetic lineations gathered at 18 sites from the Magallanes belt are sub-parallel to (mostly E-W) local fold axes, while they trend randomly at two sites from the Magallanes foreland. Our and previous AMS data consistently show that the Fuegian Andes were characterized by a N-S compression and northward displacing fold-thrust sheets during Eocene-early Miocene times (50-20 Ma), an unexpected kinematics considering coeval South America-Antarctica relative motion. Both paleomagnetic and AMS data suggest no significant influence from the E-W left-lateral Magallanes-Fagnano strike-slip fault system (MFFS), running a few kilometres south of our sampling sites. We thus speculate that strike-slip fault offset in the Fuegian Andes may range in the lower bound values (∼ 20 km) among those proposed so far. In any case our data exclude any influence of strike-slip tectonics on the genesis of the great orogenic bend called Patagonian orocline. © 2009 Elsevier B.V. All rights reserved. |
| author |
Rossello, Eduardo Antonio |
| author_facet |
Rossello, Eduardo Antonio |
| author_sort |
Rossello, Eduardo Antonio |
| title |
Paleomagnetic evidence for a pre-early Eocene (∼ 50 Ma) bending of the Patagonian orocline (Tierra del Fuego, Argentina): Paleogeographic and tectonic implications |
| title_short |
Paleomagnetic evidence for a pre-early Eocene (∼ 50 Ma) bending of the Patagonian orocline (Tierra del Fuego, Argentina): Paleogeographic and tectonic implications |
| title_full |
Paleomagnetic evidence for a pre-early Eocene (∼ 50 Ma) bending of the Patagonian orocline (Tierra del Fuego, Argentina): Paleogeographic and tectonic implications |
| title_fullStr |
Paleomagnetic evidence for a pre-early Eocene (∼ 50 Ma) bending of the Patagonian orocline (Tierra del Fuego, Argentina): Paleogeographic and tectonic implications |
| title_full_unstemmed |
Paleomagnetic evidence for a pre-early Eocene (∼ 50 Ma) bending of the Patagonian orocline (Tierra del Fuego, Argentina): Paleogeographic and tectonic implications |
| title_sort |
paleomagnetic evidence for a pre-early eocene (∼ 50 ma) bending of the patagonian orocline (tierra del fuego, argentina): paleogeographic and tectonic implications |
| publishDate |
2010 |
| url |
https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0012821X_v289_n1-2_p273_Maffione http://hdl.handle.net/20.500.12110/paper_0012821X_v289_n1-2_p273_Maffione |
| work_keys_str_mv |
AT rosselloeduardoantonio paleomagneticevidenceforapreearlyeocene50mabendingofthepatagonianoroclinetierradelfuegoargentinapaleogeographicandtectonicimplications |
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1768543401814261760 |