Provenance of Pennsylvanian–Permian sedimentary rocks associated with the Ancestral Rocky Mountains orogeny in southwestern Laurentia: Implications for continental-scale Laurentian sediment transport systems
Provenance of Pennsylvanian–Permian sedimentary rocks associated with the Ancestral Rocky Mountains orogeny in southwestern Laurentia: Implications for continental-scale Laurentian sediment transport systems
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DOI：
10.1130/l1115.1
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发表时间：
2020-01
期刊：
影响因子：
2.4
通讯作者：
R. Leary;P. Umhoefer;M. Smith;Tyson M. Smith;J. Saylor;N. Riggs;G. Burr;E. Lodes;D. Foley;A. Licht;M. Mueller;Chris Baird
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文献类型：
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作者：
R. Leary;P. Umhoefer;M. Smith;Tyson M. Smith;J. Saylor;N. Riggs;G. Burr;E. Lodes;D. Foley;A. Licht;M. Mueller;Chris Baird
祖先落基山脉系由一系列基底核隆升及其伴生的沉积盆地组成，形成于早宾夕法尼亚—中二叠世。该系统最初是由Paradox、Eagle和Denver盆地中的粗砂岩和砾岩组成的，这些盆地围绕着Front Range和Uncompahgre基底隆起。然而，与祖先落基山脉相邻的盆地的很大一部分充满了碳酸盐或细粒石英物质，这与近端黑砂岩不同。和来自落基山脉祖先附近盆地的碎屑锆石数据的解释表明，它们的很大一部分碎屑沉积物来自阿巴拉契亚和/或北极造山带，并经过长距离运输穿过劳伦西亚进入落基山脉祖先盆地。在这项研究中，我们从丹佛盆地、Eagle盆地、Paradox盆地、北亚利桑那陆架、Pedregosa盆地和Keeler-Lone Pine盆地的地层中提取了72个样品的新的U-Pb碎屑锆石数据，跨度约50 m.，并将这些数据与来自Laurentia各地的241个样品的已发表数据进行了比较。传统的视觉对比和逆向建模方法绘制了祖先落基山脉系统内的沉积物运输路径，表明盆地的近端充满了来自附近基底隆升的碎屑，而这些盆地的远端则充满了本地沉积物和来自边缘劳伦森源（包括北极埃尔斯默里安造山带和可能的北阿巴拉契亚造山带）的沉积物的混合物。这些沉积物通过一个大约2000公里长的海岸和风成系统被运送到劳伦西亚西南部，类似于现代纳米比亚海岸。祖先落基山脉的变形在二叠纪时期放缓，减少了盆地的可容纳性，使边缘碎屑源压倒了该系统。
The Ancestral Rocky Mountains system consists of a series of basement-cored uplifts and associated sedimentary basins that formed in southwestern Laurentia during Early Pennsylvanian–middle Permian time. This system was originally recognized by aprons of coarse, arkosic sandstone and conglomerate within the Paradox, Eagle, and Denver Basins, which surround the Front Range and Uncompahgre basement uplifts. However, substantial portions of Ancestral Rocky Mountain–adjacent basins are filled with carbonate or fine-grained quartzose material that is distinct from proximal arkosic rocks, and detrital zircon data from basins adjacent to the Ancestral Rocky Mountains have been interpreted to indicate that a substantial proportion of their clastic sediment was sourced from the Appalachian and/or Arctic orogenic belts and transported over long distances across Laurentia into Ancestral Rocky Mountain basins. In this study, we present new U-Pb detrital zircon data from 72 samples from strata within the Denver Basin, Eagle Basin, Paradox Basin, northern Arizona shelf, Pedregosa Basin, and Keeler–Lone Pine Basin spanning ∼50 m.y. and compare these to published data from 241 samples from across Laurentia. Traditional visual comparison and inverse modeling methods map sediment transport pathways within the Ancestral Rocky Mountains system and indicate that proximal basins were filled with detritus eroded from nearby basement uplifts, whereas distal portions of these basins were filled with a mix of local sediment and sediment derived from marginal Laurentian sources including the Arctic Ellesmerian orogen and possibly the northern Appalachian orogen. This sediment was transported to southwestern Laurentia via a ca. 2,000-km-long longshore and aeolian system analogous to the modern Namibian coast. Deformation of the Ancestral Rocky Mountains slowed in Permian time, reducing basinal accommodation and allowing marginal clastic sources to overwhelm the system.