Early Cretaceous Provenance, Sediment Dispersal, and Foreland Basin Development in Southwestern Montana, North American Cordillera
Early Cretaceous Provenance, Sediment Dispersal, and Foreland Basin Development in Southwestern Montana, North American Cordillera
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DOI：
10.1029/2020tc006561
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发表时间：
2021-03
期刊：
影响因子：
4.2
通讯作者：
J. Rosenblume;E. Finzel;D. Pearson
中科院分区：
文献类型：
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作者：
J. Rosenblume;E. Finzel;D. Pearson
蒙大拿州西部的下白垩纪库特奈组记录了北美科迪勒拉山脉爱达荷州-蒙大拿后前陆盆地中前渊沉积的开始。早白垩世沉积物扩散的对比模型已经提出。我们使用砂岩岩相学，大-n（n = 600）碎屑锆石U-Pb地质年代学和混合物建模来确定Kootenai组的物源。这些新的数据与文献中的其他数据相结合，提出了三个离散的出处签名。I型砂岩富含石英，U-Pb年龄峰值约为2000年。158，238，410，600和1，035 Ma;它们来源于折返的侏罗纪陆相地层，并通过轴向水系向北迁移。II型砂岩富含岩屑，U-Pb年龄峰值约为2000年。154、166、1，840、1，920、2，080和2，700 Ma;它们是由横向河流沉积的，这些河流从塞维尔带排出了挖出的下-中古生代地层。第三类砂岩含有长石和少量火山岩，其U-Pb年龄谱以ca为主。112和162 Ma的年龄，他们被横向排水，连接造山带的腹地与蒙大拿州西部前陆运输。根据库特奈组的物源分析，蒙大拿州西南部的微妙的早白垩世厚皮变形没有挖掘基底，也没有将前陆划分为当地来源的沉积中心。蒙大拿州西部前陆的沉积物来源与阿尔伯塔北部一致，而与爱达荷州南部不同。这些数据也提供了深入了解的平移历史的造山带腹地在这段时间内。
The Lower Cretaceous Kootenai Formation in western Montana records the onset of foredeep sedimentation in the Idaho‐Montana retroforeland basin of the North American Cordillera. Contrasting models for sediment dispersal during Early Cretaceous time have been proposed. We use sandstone petrography, large‐n (n = 600) detrital zircon U‐Pb geochronology, and mixture modeling to determine the provenance of the Kootenai Formation. These new data combined with additional data from the literature suggest three discrete provenance signatures. Type I sandstones are quartz‐rich with U‐Pb age peaks at ca. 158, 238, 410, 600, and 1,035 Ma; they were sourced from exhumed Jurassic continental strata and transported northward by axial drainages. Type II sandstones are lithic‐rich with U‐Pb age peaks at ca. 154, 166, 1,840, 1,920, 2,080, and 2,700 Ma; they were deposited by transverse rivers that drained exhumed lower‐middle Paleozoic strata from the Sevier belt. Type III sandstones contain feldspars and minor volcanic lithics with U‐Pb age spectra that are dominated by ca. 112 and 162 Ma ages; they were transported by transverse drainages that connected the hinterland of the orogen with the western Montana foreland. Based on provenance analysis of the Kootenai Formation, subtle Early Cretaceous thick‐skinned deformation in southwestern Montana did not exhume basement nor did it partition the foreland into locally sourced depocenters. Sediment sources for the western Montana foreland are consistent with those to the north in Alberta and different than southern Idaho. These data also provide insight into the translational history of terranes in the hinterland of the orogen during this time.