Miocene regional hotspot-related uplift, exhumation, and extension north of the Snake River Plain: Evidence from apatite (U-Th)/He thermochronology
Miocene regional hotspot-related uplift, exhumation, and extension north of the Snake River Plain: Evidence from apatite (U-Th)/He thermochronology
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蛇河平原以北中新世区域热点相关的抬升、折返和延伸：来自磷灰石（U-Th）/He热年代学的证据
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发表时间：
2014
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通讯作者：
A. Marsellos
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作者：
J. Vogl;K. Min;A. Carmenate;D. Foster;A. Marsellos
北美洲经过黄石热点地区对落基山脉北部地区的地形产生了深远的影响。与热点相关的最突出的地形特征之一是高地的黄石新月形，它由两个高耸的肩部组成，边界东部斯内克河平原，并汇聚在以黄石地区为中心的地形隆起处。我们对从黄石新月形高地北臂的先锋-博尔德山收集的磷灰石（AHe）进行了单晶（U-Th）/He测年，以限制折返的时间、速率和空间分布。这些数据对负责与热点通过相关的抬升的时间和过程提供了限制。先锋-博尔德山脉代表了由海拔和始新世查利斯火山省保存地层的几何形状定义的地形和结构的顶峰。 AHe 年龄表明，自大约 2000 年以来，Pioneer-Boulder Mountains 顶峰的核心地区已经发生了≥2-3 公里的折返，那里没有保存任何查利斯火山。 11马。查利斯火山得到广泛保存，先锋-博尔德山脉北部和南部局部保留了始新世地形高点，表明这些地区的侵蚀程度极小。年龄-海拔关系表明，大约 10 到 10 年间，折返率约为 0.3 毫米/年。 11 和 8 Ma 为顶峰核心；这种相对较快的挖掘间隔是在超过 30 m.y 的时期之后发生的。在此期间，几乎没有发生区域规模的挖掘活动。折返和地形的空间模式表明，断层并不是顶峰隆升和折返的主要控制因素。相反，NNW 走向的正断层叠加在顶点上，来自 Copper Creek 断层下盘的 AHe 年龄表明断层开始于大约 10 世纪或之后。 10-9 Ma。 11-8 Ma 的区域折返与大约 11-8 Ma 的硅质喷发同步。 10.3 马皮卡博火山场位于紧邻先锋-博尔德山脉顶峰南侧的南侧，这可能是中地壳镁铁质侵入对斯内克河平原东部造成负荷的结果。这种同步性表明，通过弯曲和地幔动力学对隆升的潜在贡献，以及排水网络和基准面的变化，热点过程和折返之间存在因果关系。
Passage of North America over the Yellowstone hotspot has had a profound infl uence on the topography of the northern Rocky Mountains region. One of the most prominent hotspot-related topographic features is the Yellowstone crescent of high terrain, which consists of two elevated shoulders bounding the eastern Snake River Plain and converging at a topographic swell centered on the Yellowstone region. We have applied single-grain (U-Th)/He dating to apatites (AHe) collected from the Pioneer-Boulder Mountains on the northern arm of the Yel- lowstone crescent of high terrain to constrain the timing, rates, and spatial distribution of exhumation. These data provide constraints on the timing and processes responsible for uplift related to passage of the hotspot. The Pioneer-Boulder Mountains represent a topographic and structural culmination defi ned by elevation and by the geometry of preserved strata of the Eocene Challis volcanic province. AHe ages indicate that ≥2–3 km of exhumation has occurred in the core of the Pioneer-Boulder Mountains culmination, where no Challis volcanics are preserved, since ca. 11 Ma. Challis volcanics are extensively preserved and Eocene topographic highs are locally preserved to the north and south of the Pioneer-Boulder Mountains, indicating minimal erosion in those areas. Age-elevation relationships suggest an exhumation rate of ~0.3 mm/yr between ca. 11 and 8 Ma for the culmination core; this relatively rapid interval of exhumation followed a period of >30 m.y. during which little to no regional-scale exhumation occurred. Spatial patterns of both exhumation and topography indicate that faulting was not the primary control on uplift and exhumation of the culmination. Instead, NNW-trending normal faults are superimposed on the culmination, with the AHe ages from the footwall of the Copper Creek fault indicating that faulting began at or after ca. 10–9 Ma. Regional exhumation at 11–8 Ma was synchronous with silicic eruptions from the ca. 10.3 Ma Picabo volcanic fi eld located immediately to the south and with S tilting of the southern fl ank of the Pioneer-Boulder Mountains culmination, which was likely the result of loading of the eastern Snake River Plain by midcrustal mafi c intrusions. This synchroneity suggests a causal relationship between hotspot processes and exhu- mation through potential contributions of fl exure and mantle dynamics to uplift, as well as changes in drainage networks and base level