A river runs through it both ways across time: 40Ar/39Ar detrital and bedrock muscovite geochronology constraints on the Neogene paleodrainage history of the Nenana River system, Alaska Range
A river runs through it both ways across time: 40Ar/39Ar detrital and bedrock muscovite geochronology constraints on the Neogene paleodrainage history of the Nenana River system, Alaska Range
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DOI：
10.1130/ges01673.1
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发表时间：
2019-06
期刊：
影响因子：
2.5
通讯作者：
J. Benowitz;Kailyn N. Davis;S. Roeske
中科院分区：
文献类型：
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作者：
J. Benowitz;Kailyn N. Davis;S. Roeske
阿拉斯加山脉是德纳里断层的地形标志，具有不寻常的自然地理特征，内纳纳河发源于分水岭的南侧，在向北穿越山脉之前，沿着山脉前沿穿越一段距离。以前的研究人员认为，从南流到北流的排水系统的变化发生在约。6 Ma，或中新世早期-中期，在阿拉斯加山脉隆起的初始阶段。我们应用40 Ar/39 Ar测年碎屑云母从现代河流沉积物（代理盆源）和地层的新近纪塔纳纳盆地（汇的古Nenana河），位于沿着阿拉斯加山脉的北方前线，进一步研究这一假说。此外，我们获得了40 Ar/39 Ar白云母年龄从基岩额外的来源限制，并比较我们的结果，区域地质年代学数据集和地质填图。在最早的中新世，古Nenana河可能流向南方。到中新世早期，古Nenana河流向北方。在中新世中期，排水重组继续进行，这表明阿拉斯加山脉的岩石隆起的变化历史。到了中新世晚期，随着塔纳纳盆地南部的隆起和侵蚀，沉积物循环发生。现代Nenana河附近的坎特韦尔有一个白云母年龄签名不同于塔纳纳盆地地层，这意味着继续排水重组后，沉积的上新世Nenana砾石。总的来说，Nenana河流域大约在1980年左右改变了流向，向北流动。18 Ma，构造运动驱动。今天，水系重组仍在继续，这表明走滑断层转换造山带可能具有复杂的古水系历史。
The Alaska Range, the topographic signature of the Denali fault, has an unusual physiography, with the Nenana River sourced from the south side of the divide and traversing along the range front some distance before heading north across the mountain range. Previous researchers suggested that a change from south-flowing to north-flowing drainage occurred at ca. 6 Ma, or early-middle Miocene, during initial phases of Alaska Range uplift. We applied 40Ar/39Ar dating of detrital micas from modern river sediment (proxy for basinwide source) and strata of the Neogene Tanana Basin (sink for the paleo–Nenana River), located along the northern front of the Alaska Range, to further investigate this hypothesis. In addition, we acquired 40Ar/39Ar muscovite ages from bedrock for additional source constraints and compared our results to regional geochronology data sets and geological mapping. During the earliest Miocene, the paleo–Nenana River likely flowed south. By the early Miocene, the paleo–Nenana River flowed to the north. During the middle Miocene, drainage reorganization continued, suggesting a variable history of rock uplift in the Alaska Range. By the late Miocene, sediment recycling occurred as the southern extent of the Tanana Basin was uplifted and eroded. The modern Nenana River near Cantwell has a muscovite age signature different than the Tanana Basin strata, implying continued drainage reorganization after the deposition of the Pliocene Nenana Gravel. In summary, the Nenana River drainage changed direction to north-flowing by ca. 18 Ma, driven by tectonism. Drainage reorganization continues today, demonstrating that strike-slip fault transpressive orogens can have complex paleodrainage histories.