Periglacial landscape dynamics in the western Canadian Arctic: Results from a thermokarst lake record on a push moraine (Herschel Island, Yukon Territory)
Periglacial landscape dynamics in the western Canadian Arctic: Results from a thermokarst lake record on a push moraine (Herschel Island, Yukon Territory)
复制标题
加拿大西部北极地区的冰缘景观动态：推式冰碛上热喀斯特湖记录的结果（育空地区赫歇尔岛）
DOI：
10.1016/j.palaeo.2013.04.009
复制
发表时间：
2013
期刊：
影响因子：
--
通讯作者：
S. Wetterich
中科院分区：
文献类型：
--
作者：
J. Lenz;M. Fritz;Lutz Schirrmeister;H. Lantuit;M. Wooller;W. Pollard;S. Wetterich
由于热岩溶发育过程中地面冰的融化，富冰的冻土景观对气候和环境变化非常敏感。北方育空地区的热岩溶过程目前没有很好的记录。加拿大北极西部赫歇尔岛（69°36′N; 139°04′W）的湖泊沉积物提供了全新世早期以来热岩溶湖泊发育的记录。一个727厘米长的湖泊沉积物芯进行了分析，射线照相图像，磁化率，粒度，和地球化学参数（有机碳，氮，稳定碳同位素）。根据8个校准的AMS放射性碳年龄，沉积记录涵盖了过去11,500年，并划分为4个岩石地层单位（A至D），反映了不同的热岩溶阶段。研究区的热岩溶作用开始于约11.5calkaBP。约11.5 ~ 10.0calkaBP，A单元湖泊沉积物开始堆积在由大量地面冰融化和融沉形成的初始湖盆中。在10.0 ~ 7.0 cal ka BP（单元B）之间，湖盆的规模和深度扩大，这是全新世热盛期Talik形成的结果。高于现代的夏季气温导致了湖泊生产力的增加和湖泊集水区广泛的地形扰动。7.0和1.8cal ka BP（单元C）之间的热岩溶湖泊发育的特点是动态平衡，湖盆和talik稳步扩大到周围的富冰地形通过海岸线侵蚀。一旦湖泊变得比最大冬季湖冰厚度更深，热岩溶湖泊沉积物显示出巨大的保存潜力。然而，特定地点的地貌因素，如间歇性的河岸侵蚀或通过热侵蚀山谷或海岸侵蚀破坏湖盆的突然排水，可能会破坏连续沉积。赫歇尔湖1.8 ~ 0.9 cal ka BP的记录间断可能是由于在最近900年D单元重新开始连续沉积之前，湖泊排水或海岸线坍塌引起的异地滑塌所致。
Ice-rich permafrost landscapes are sensitive to climate and environmental change due to the melt-out of ground ice during thermokarst development. Thermokarst processes in the northern Yukon Territory are currently not well-documented. Lake sediments from Herschel Island (69°36′N; 139°04′W) in the western Canadian Arctic provide a record of thermokarst lake development since the early Holocene. A 727cm long lake sediment core was analyzed for radiographic images, magnetic susceptibility, granulometry, and biogeochemical parameters (organic carbon, nitrogen, and stable carbon isotopes). Based on eight calibrated AMS radiocarbon dates, the sediment record covers the last ~11,500years and was divided into four lithostratigraphic units (A to D) reflecting different thermokarst stages. Thermokarst initiation at the study area began ~11.5cal ka BP. From ~11.5 to 10.0cal ka BP, lake sediments of unit A started to accumulate in an initial lake basin created by melt-out of massive ground ice and thaw subsidence. Between 10.0 and 7.0cal ka BP (unit B) the lake basin expanded in size and depth, attributed to talik formation during the Holocene thermal maximum. Higher-than-modern summer air temperatures led to increased lake productivity and widespread terrain disturbances in the lake's catchment. Thermokarst lake development between 7.0 and 1.8cal ka BP (unit C) was characterized by a dynamic equilibrium, where lake basin and talik steadily expanded into ambient ice-rich terrain through shoreline erosion. Once lakes become deeper than the maximum winter lake ice thickness, thermokarst lake sediments show a great preservation potential. However, site-specific geomorphic factors such as episodic bank-shore erosion or sudden drainage through thermo-erosional valleys or coastal erosion breaching lake basins can disrupt continuous deposition. A hiatus in the record from 1.8 to 0.9cal ka BP in Lake Herschel likely resulted from lake drainage or allochthonous slumping due to collapsing shore lines before continuous sedimentation of unit D recommenced during the last 900years.