Paleomagnetic reconstruction of Coahuila, Mexico: the Late Triassic Acatita intrusives
The Acatita plutons intrude the upper Paleozoic of Las Delicias, southern Coahuila. We collected 96 samples from 15 sitesin two plutons from Valle El Sobaco and Sierra Los Remedios for paleomagnetic and 40Ar-39Ar analyses. Separates of hornblende(215.9 ±1.9 Ma, 2σ confidence level), biotite...
| Autor: | |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2005 |
| País: | México |
| Institución: | Universidad Nacional Autónoma de México |
| Repositorio: | Redalyc-UNAM |
| OAI Identifier: | oai:redalyc.org:56844207 |
| Acceso en línea: | https://www.redalyc.org/articulo.oa?id=56844207 |
| Access Level: | acceso abierto |
| Palabra clave: | Ciencias de la Tierra Mexico Pangea Coahuila Late Triassic Paleomagnetism |
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Paleomagnetic reconstruction of Coahuila, Mexico: the Late Triassic Acatita intrusivesRoberto S. Molina GarzaCiencias de la TierraMexicoPangeaCoahuilaLate TriassicPaleomagnetismThe Acatita plutons intrude the upper Paleozoic of Las Delicias, southern Coahuila. We collected 96 samples from 15 sitesin two plutons from Valle El Sobaco and Sierra Los Remedios for paleomagnetic and 40Ar-39Ar analyses. Separates of hornblende(215.9 ±1.9 Ma, 2σ confidence level), biotite (217.3 ±1.2 Ma), and K-feldspar (205.6 ±1.4 Ma) yield nearly flat age spectraalthough none of the data satisfy strict plateau criteria, possibly reflecting slight alteration. The preferred ages are interpreted asfairly precise records of Late Triassic cooling of the plutonic suite, which has yielded concordant U-Pb Zircon ages ca. 220 Ma.Most samples yield north-directed and steep positive magnetizations similar to the late Cenozoic expected field direction. Somesamples, mostly from mafic enclaves, show northwest magnetization of shallow inclination (southeast at one site) with alternatingfields above ~30 mT and thermal demagnetization above ~400°C. The overall mean direction, corrected for 15° northeast dip ofthe overlying lower Cretaceous strata (dec=342.7°, inc=+4.2°; k=35.4, α95=9.4°, n=8 sites) indicates moderate counterclockwise(14°±8°) rotation with respect to the Late Triassic cratonic reference (reference pole: 57.5°N / 84°E), and moderate southwarddisplacement (7°±5°). The Acatita pole falls within a cluster of Late Triassic poles from Africa, South America, and North Americaas restored in North American coordinates. A major difficulty is distinguishing local, small-scale rotations, such as a gentle tilt ofthe pluton after magnetization, from regional events involving large-scale displacements. Rotations such as observed at Acatitaare suggested by synfolding magnetizations (Eocene in age) in the transverse sector of the Sierra Madre Oriental and by primarymagnetizations in Eocene volcanic rocks near Chihuahua. Therefore rotations of Coahuila Island may be a Cenozoic attributerelated to late Laramide deformation. Reconstructions of western equatorial Pangea should place the Coahuiltecano terrane at ornear its present position with respect to North America.Universidad Nacional Autónoma de México2005info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/articleapplication/pdf0016-7169https://www.redalyc.org/articulo.oa?id=56844207Geofísica Internacional (México) Num.2 Vol.44reponame:Redalyc-UNAMinstname:Universidad Nacional Autónoma de Méxicoinstacron:UNAMenhttp://www.redalyc.org/revista.oa?id=568Geofísica Internacionalinfo:eu-repo/semantics/openAccessoai:redalyc.org:568442072025-09-03T18:07:36Z |
| dc.title.none.fl_str_mv |
Paleomagnetic reconstruction of Coahuila, Mexico: the Late Triassic Acatita intrusives |
| title |
Paleomagnetic reconstruction of Coahuila, Mexico: the Late Triassic Acatita intrusives |
| spellingShingle |
Paleomagnetic reconstruction of Coahuila, Mexico: the Late Triassic Acatita intrusives Roberto S. Molina Garza Ciencias de la Tierra Mexico Pangea Coahuila Late Triassic Paleomagnetism |
| title_short |
Paleomagnetic reconstruction of Coahuila, Mexico: the Late Triassic Acatita intrusives |
| title_full |
Paleomagnetic reconstruction of Coahuila, Mexico: the Late Triassic Acatita intrusives |
| title_fullStr |
Paleomagnetic reconstruction of Coahuila, Mexico: the Late Triassic Acatita intrusives |
| title_full_unstemmed |
Paleomagnetic reconstruction of Coahuila, Mexico: the Late Triassic Acatita intrusives |
| title_sort |
Paleomagnetic reconstruction of Coahuila, Mexico: the Late Triassic Acatita intrusives |
| dc.creator.none.fl_str_mv |
Roberto S. Molina Garza |
| author |
Roberto S. Molina Garza |
| author_facet |
Roberto S. Molina Garza |
| author_role |
author |
| dc.subject.none.fl_str_mv |
Ciencias de la Tierra Mexico Pangea Coahuila Late Triassic Paleomagnetism |
| topic |
Ciencias de la Tierra Mexico Pangea Coahuila Late Triassic Paleomagnetism |
| description |
The Acatita plutons intrude the upper Paleozoic of Las Delicias, southern Coahuila. We collected 96 samples from 15 sitesin two plutons from Valle El Sobaco and Sierra Los Remedios for paleomagnetic and 40Ar-39Ar analyses. Separates of hornblende(215.9 ±1.9 Ma, 2σ confidence level), biotite (217.3 ±1.2 Ma), and K-feldspar (205.6 ±1.4 Ma) yield nearly flat age spectraalthough none of the data satisfy strict plateau criteria, possibly reflecting slight alteration. The preferred ages are interpreted asfairly precise records of Late Triassic cooling of the plutonic suite, which has yielded concordant U-Pb Zircon ages ca. 220 Ma.Most samples yield north-directed and steep positive magnetizations similar to the late Cenozoic expected field direction. Somesamples, mostly from mafic enclaves, show northwest magnetization of shallow inclination (southeast at one site) with alternatingfields above ~30 mT and thermal demagnetization above ~400°C. The overall mean direction, corrected for 15° northeast dip ofthe overlying lower Cretaceous strata (dec=342.7°, inc=+4.2°; k=35.4, α95=9.4°, n=8 sites) indicates moderate counterclockwise(14°±8°) rotation with respect to the Late Triassic cratonic reference (reference pole: 57.5°N / 84°E), and moderate southwarddisplacement (7°±5°). The Acatita pole falls within a cluster of Late Triassic poles from Africa, South America, and North Americaas restored in North American coordinates. A major difficulty is distinguishing local, small-scale rotations, such as a gentle tilt ofthe pluton after magnetization, from regional events involving large-scale displacements. Rotations such as observed at Acatitaare suggested by synfolding magnetizations (Eocene in age) in the transverse sector of the Sierra Madre Oriental and by primarymagnetizations in Eocene volcanic rocks near Chihuahua. Therefore rotations of Coahuila Island may be a Cenozoic attributerelated to late Laramide deformation. Reconstructions of western equatorial Pangea should place the Coahuiltecano terrane at ornear its present position with respect to North America. |
| publishDate |
2005 |
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2005 |
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info:eu-repo/semantics/publishedVersion info:eu-repo/semantics/article |
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article |
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publishedVersion |
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0016-7169 https://www.redalyc.org/articulo.oa?id=56844207 |
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0016-7169 |
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https://www.redalyc.org/articulo.oa?id=56844207 |
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en |
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en |
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http://www.redalyc.org/revista.oa?id=568 |
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Geofísica Internacional info:eu-repo/semantics/openAccess |
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Geofísica Internacional |
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openAccess |
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Universidad Nacional Autónoma de México |
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Universidad Nacional Autónoma de México |
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Geofísica Internacional (México) Num.2 Vol.44 reponame:Redalyc-UNAM instname:Universidad Nacional Autónoma de México instacron:UNAM |
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Universidad Nacional Autónoma de México |
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UNAM |
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