Yedoma Cryostratigraphy of Recently Excavated Sections of the CRREL Permafrost Tunnel Near Fairbanks, Alaska
Yedoma Cryostratigraphy of Recently Excavated Sections of the CRREL Permafrost Tunnel Near Fairbanks, Alaska
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DOI：
10.3389/feart.2021.758800
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发表时间：
2022-03
影响因子：
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通讯作者：
M. Kanevskiy;Y. Shur;N. Bigelow;K. Bjella;T. Douglas;David H. Fortier;B. Jones;M. Jorgenson
中科院分区：
文献类型：
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作者：
M. Kanevskiy;Y. Shur;N. Bigelow;K. Bjella;T. Douglas;David H. Fortier;B. Jones;M. Jorgenson
最近在阿拉斯加福克斯的新CRREL永久冻土隧道的挖掘提供了一个独特的机会来研究Yedoma -晚更新世冰和有机物丰富的同生永久冻土的特性。Yedoma在阿拉斯加内陆的许多地方都有描述，主要是在育空-塔纳纳高地。关于这一地区Yedoma的结构和性质的最全面的数据是在费尔班克斯附近的CRREL永久冻土隧道中获得的-这是地球上Yedoma永久冻土最容易接近的大规模暴露之一，研究人员在20世纪60年代中期开始使用。2011年开始并正在进行的新的104米高和104米宽的线性挖掘的扩展，暴露了另外300米保存完好的Yedoma，并提供了过去40，000年沉积的沉积物，这将使我们能够量化同生永冻土形成的速率和模式，沉积历史和Yedoma的地球化学特征，以及它对气候变暖的反应在本文中，我们提出了详细的冷冻地层研究的结果，在隧道和邻近地区。我们的研究数据包括地冰含量、各种地冰体的稳定水同位素组成和放射性碳年龄。根据隧道的冰冻地层填图和隧道上、洞内钻探结果，划分出6个主要的冰冻地层单位：1）活动层; 2）现代中间层（3）相对贫冰的Yedoma粉土，在全新世期间受到热侵蚀和热岩溶作用的改造，（4）晚更新世富冰的Yedoma粉土，具有大的冰楔; 5）相对贫冰的河流砾石; 6）贫冰的基岩。我们的研究揭示了新的和旧的CRREL永久冻土隧道设施的冻土地层学的显着差异。新隧道中的原始同生永冻土在Yedoma形成期间得到了更好的保存，受侵蚀事件的影响较小，尽管许多特征（例如，热岩溶洞穴冰体、融化不整合面、埋藏冲沟）表明，在更新世晚期和全新世期间，最近挖掘的部分中的原始Yedoma粉土也在一定程度上受到热岩溶和热侵蚀的改造。
Recent excavation in the new CRREL Permafrost Tunnel in Fox, Alaska provides a unique opportunity to study properties of Yedoma — late Pleistocene ice- and organic-rich syngenetic permafrost. Yedoma has been described at numerous sites across Interior Alaska, mainly within the Yukon-Tanana upland. The most comprehensive data on the structure and properties of Yedoma in this area have been obtained in the CRREL Permafrost Tunnel near Fairbanks — one of the most accessible large-scale exposures of Yedoma permafrost on Earth, which became available to researchers in the mid-1960s. Expansion of the new ∼4-m-high and ∼4-m-wide linear excavations, started in 2011 and ongoing, exposes an additional 300 m of well-preserved Yedoma and provides access to sediments deposited over the past 40,000 years, which will allow us to quantify rates and patterns of formation of syngenetic permafrost, depositional history and biogeochemical characteristics of Yedoma, and its response to a warmer climate. In this paper, we present results of detailed cryostratigraphic studies in the Tunnel and adjacent area. Data from our study include ground-ice content, the stable water isotope composition of the variety of ground-ice bodies, and radiocarbon age dates. Based on cryostratigraphic mapping of the Tunnel and results of drilling above and inside the Tunnel, six main cryostratigraphic units have been distinguished: 1) active layer; 2) modern intermediate layer (ice-rich silt); 3) relatively ice-poor Yedoma silt reworked by thermal erosion and thermokarst during the Holocene; 4) ice-rich late Pleistocene Yedoma silt with large ice wedges; 5) relatively ice-poor fluvial gravel; and 6) ice-poor bedrock. Our studies reveal significant differences in cryostratigraphy of the new and old CRREL Permafrost Tunnel facilities. Original syngenetic permafrost in the new Tunnel has been better preserved and less affected by erosional events during the period of Yedoma formation, although numerous features (e.g., bodies of thermokarst-cave ice, thaw unconformities, buried gullies) indicate the original Yedoma silt in the recently excavated sections was also reworked to some extent by thermokarst and thermal erosion during the late Pleistocene and Holocene.