Progressive Miocene unroofing of the Big Maria and Riverside Mountains (southeastern California, USA) along the southwestern margin of the Colorado River extensional corridor
{"title":"Progressive Miocene unroofing of the Big Maria and Riverside Mountains (southeastern California, USA) along the southwestern margin of the Colorado River extensional corridor","authors":"Megan E. Flansburg, D. Stockli","doi":"10.1130/ges02564.1","DOIUrl":null,"url":null,"abstract":"The Colorado River extensional corridor (CREC) consists of Miocene meta-morphic core complexes exhumed along top-to-the-NE low-angle detachment faults. The Big Maria and Riverside Mountains of southeastern California (USA) are located on the southwestern margin of the CREC, where little is known about the nature and timing of large-magnitude extension. We present the first detailed (U-Th)/He thermochronometric data from these ranges, elucidating the geometry and timing of upper-crustal extensional unroofing and exhumation. The Riverside Mountains yielded ca. 72–50 Ma zircon (U-Th)/He (ZHe) ages in the hanging wall of the Riverside detachment fault, and the corrugated footwall yielded ca. 50–18 Ma ZHe ages, indicating the preservation of an exhumed ZHe partial retention zone. Apatite (U-Th)/He data further indicate a potential secondary Miocene breakaway in the northeastern end of the range. Although the Big Maria Mountains have been thought to lie outside of the CREC, our new zircon and apatite (U-Th)/He data show that the entirety of the Big Maria Mountains was tectonically exhumed in the footwall of a detachment fault and cooled from >6 km depth between 22 and 15 Ma. ZHe data from both ranges suggest the Big Maria Mountains are part of the CREC and were exhumed from underneath the Riverside Mountains by a contemporaneous but structurally lower detachment—the Big Maria detachment—that is regionally correlative with the breakaway zone that delimits the western CREC margin. This detachment is temporally coeval with the structurally higher detachment system that forms the Whipple-Buckskin-Rawhide-Harcuvar-Harquahala metamorphic core complex belt to the northeast.","PeriodicalId":55100,"journal":{"name":"Geosphere","volume":" ","pages":""},"PeriodicalIF":1.7000,"publicationDate":"2023-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Geosphere","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1130/ges02564.1","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
The Colorado River extensional corridor (CREC) consists of Miocene meta-morphic core complexes exhumed along top-to-the-NE low-angle detachment faults. The Big Maria and Riverside Mountains of southeastern California (USA) are located on the southwestern margin of the CREC, where little is known about the nature and timing of large-magnitude extension. We present the first detailed (U-Th)/He thermochronometric data from these ranges, elucidating the geometry and timing of upper-crustal extensional unroofing and exhumation. The Riverside Mountains yielded ca. 72–50 Ma zircon (U-Th)/He (ZHe) ages in the hanging wall of the Riverside detachment fault, and the corrugated footwall yielded ca. 50–18 Ma ZHe ages, indicating the preservation of an exhumed ZHe partial retention zone. Apatite (U-Th)/He data further indicate a potential secondary Miocene breakaway in the northeastern end of the range. Although the Big Maria Mountains have been thought to lie outside of the CREC, our new zircon and apatite (U-Th)/He data show that the entirety of the Big Maria Mountains was tectonically exhumed in the footwall of a detachment fault and cooled from >6 km depth between 22 and 15 Ma. ZHe data from both ranges suggest the Big Maria Mountains are part of the CREC and were exhumed from underneath the Riverside Mountains by a contemporaneous but structurally lower detachment—the Big Maria detachment—that is regionally correlative with the breakaway zone that delimits the western CREC margin. This detachment is temporally coeval with the structurally higher detachment system that forms the Whipple-Buckskin-Rawhide-Harcuvar-Harquahala metamorphic core complex belt to the northeast.
期刊介绍:
Geosphere is GSA''s ambitious, online-only publication that addresses the growing need for timely publication of research results, data, software, and educational developments in ways that cannot be addressed by traditional formats. The journal''s rigorously peer-reviewed, high-quality research papers target an international audience in all geoscience fields. Its innovative format encourages extensive use of color, animations, interactivity, and oversize figures (maps, cross sections, etc.), and provides easy access to resources such as GIS databases, data archives, and modeling results. Geosphere''s broad scope and variety of contributions is a refreshing addition to traditional journals.