The Cenozoic history of crustal deformation, surface uplift, and erosion of the central Colorado Plateau (southwestern USA) is distinct from and relatively poorly understood compared with surrounding regions in the North American Cordillera, including the Grand Canyon region and the southwestern Plateau margin. Here, we present new apatite thermochronologic results from Paleozoic-Mesozoic sandstones sampled in the Canyonlands region—the interior of the Colorado Plateau in southeastern Utah. The apatite (U-Th-Sm)/He (He) ages are highly dispersed, with both positive-slope and negative-slope age-effective U (eU) trends. Samples with apatite He results suitable for thermal history modeling are from the Abajo and La Sal mountains intrusive complexes and the Permian, Triassic, and Jurassic rocks sampled near the Colorado River at Lees Ferry, Arizona, and Hite, Utah. Samples with the richest thermal history information have positive-slope apatite He age-[eU] trends, with ages ca. 10 to 5 Ma at [eU] < 10 ppm and ca. 25 to 20 Ma at [eU] > 60 ppm. Modeled thermal histories that best predict this pattern require two periods of rock cooling: one during the middle Cenozoic ca. 30 to 20 Ma and the other since the latest Miocene ca. 6 Ma. The most recent cooling documents the transition from a slowly eroding Miocene landscape to recent rapid erosion that likely postdates 6 Ma and the integration of the modern Colorado River. Middle Cenozoic rock cooling can be attributed to either ∼1 km of erosion between ca. 25 and 15 Ma, as previous workers have suggested in other parts of the Colorado Plateau region, or relaxation of a geothermal gradient transiently doubled by magmatism associated with the vigorous magmatic flare-up that swept through the region ca. 34 to 20 Ma. The ambiguity of using middle Cenozoic rock cooling as a proxy for erosion in this region means that this event should be described using a nongenetic term: the Middle Cenozoic Cooling Event.

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科罗拉多高原峡谷地地区侵蚀和岩浆作用的热年代记录

与包括大峡谷地区和高原西南部边缘在内的北美科迪勒拉山脉的周边地区相比，科罗拉多高原中部（美国西南部）的地壳变形、地表隆起和侵蚀的新生代历史与北美科迪勒拉山脉的周围地区不同，而且了解相对较少。在这里，我们展示了在峡谷地地区（犹他州东南部的科罗拉多高原内部）采样的古生代-中生代砂岩的新磷灰石热年代学结果。磷灰石 (U-Th-Sm)/He (He) 年龄高度分散，具有正斜率和负斜率年龄效应 U (eU) 趋势。适合热历史建模的含磷灰石 He 结果的样品来自 Abajo 和 La Sal 山侵入杂岩，以及在亚利桑那州 Lees Ferry 的科罗拉多河附近采样的二叠纪、三叠纪和侏罗纪岩石，和海特，犹他州。具有最丰富的热历史信息的样品具有正斜率的磷灰石 He 年龄-[eU] 趋势，年龄约为。[eU] < 10 ppm 和约 10 至 5 毫安 [eU] > 60 ppm 时为 25 至 20 Ma。最能预测这种模式的模拟热历史需要两个时期的岩石冷却：一个是在新生代中期。30 至 20 Ma 和其他自最新的中新世约。6 马。最近的冷却记录了从缓慢侵蚀的中新世景观到最近可能在 6 Ma 之后的快速侵蚀以及现代科罗拉多河的融合的转变。中新生代岩石冷却可归因于约 1 公里之间约 1 公里的侵蚀。25 和 15 Ma，正如之前的工作人员在科罗拉多高原地区的其他地区所建议的那样，或与席卷该地区的剧烈岩浆爆发相关的岩浆活动暂时加倍地热梯度的弛豫。34 到 20 毫安。使用中新生代岩石冷却作为该地区侵蚀的代理的模糊性意味着应该使用非遗传术语来描述该事件：中新生代冷却事件。