Progressive Miocene unroofing of the Big Maria and Riverside Mountains (southeastern California, USA) along the southwestern margin of the Colorado River extensional corridor

IF 1.7 3区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY
Geosphere Pub Date : 2023-03-16 DOI:10.1130/ges02564.1
Megan E. Flansburg, D. Stockli
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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.
科罗拉多河伸展走廊西南边缘的大玛丽亚和里弗赛德山脉(美国加利福尼亚州东南部)的渐进中新世展开
科罗拉多河伸展走廊(CREC)由沿北东向低角度拆离断层顶部挖掘的中新世变质核杂岩组成。美国加利福尼亚州东南部的大玛丽亚和里弗赛德山脉位于CREC的西南边缘,在那里,人们对大震级延伸的性质和时间知之甚少。我们提供了来自这些范围的第一个详细的(U-Th)/He热年代学数据,阐明了上地壳伸展展开和剥露的几何结构和时间。河滨山脉在河滨拆离断层的上盘中产生了约72–50 Ma的锆石(U-Th)/He(ZHe)年龄,波纹下盘产生了约50–18 Ma的ZHe年龄,表明保留了一个剥露的ZHe部分保留带。磷灰石(U-Th)/He数据进一步表明,该范围东北端存在潜在的中新世次生断裂。尽管大玛利亚山脉被认为位于CREC之外,但我们新的锆石和磷灰石(U-Th)/He数据显示,整个大玛利亚山脉都是在拆离断层的下盘中构造折返的,并在22至15 Ma之间从>6 km的深度冷却。来自这两个山脉的ZHe数据表明,大玛利亚山脉是CREC的一部分,是由同时代但结构较低的分离带——大玛利亚分离带——从河滨山脉下方挖掘出来的,该分离带与划定CREC西部边缘的分离带在区域上是相关的。该拆离在时间上与构造上较高的拆离系统同时代,该拆离系统形成了东北部的Whipple Buckskin-Rawhide Harcuvar Harquahala变质核杂岩带。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Geosphere
Geosphere 地学-地球科学综合
CiteScore
4.40
自引率
12.00%
发文量
71
审稿时长
6-12 weeks
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.
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