High-resolution tephrochronology of the Wilson Creek Formation (Mono Lake, California) and Laschamp event using 238U-230Th SIMS dating of accessory mineral rims
High-resolution tephrochronology of the Wilson Creek Formation (Mono Lake, California) and Laschamp event using 238U-230Th SIMS dating of accessory mineral rims
复制标题
使用辅助矿物边缘的 238U-230Th SIMS 测年，对 Wilson Creek 地层（加利福尼亚州莫诺湖）和 Laschamp 事件进行高分辨率年代学分析
DOI：
10.1016/j.epsl.2012.09.013
复制
发表时间：
2012
影响因子：
5.3
通讯作者：
M. Lidzbarski
中科院分区：
文献类型：
--
作者：
J. Vazquez;M. Lidzbarski
莫诺湖周围威尔逊溪地层的沉积物保存了内华达山脉东部由于晚更新世气候变化而产生的冰川和洪流反应的高分辨率档案。威尔逊溪地层学的绝对年代学对于将古气候记录与美国西部和北大西洋地区的其他档案联系起来至关重要。然而，由于开放系统效应和放射性碳储层的不确定性以及丰富的异晶，使用碳酸盐和火山灰对威尔逊溪地层进行年代测定的多次尝试产生了不一致的结果。新离子微探针238U-230Th对幼年火山碎屑中的铜长石和锆石自晶记录的最终结晶增量进行测年，得出的年龄有效地确定了关键火山灰层喷发的年代，并将基底威尔逊溪沉积的时间界定在26.8±2.1和61.7±1.9ka之间。火山灰 (Ash 15) 在最初指定为莫诺湖偏移的地磁偏移期间喷发，其年龄为 40.8±1.9ka，表明该事件是拉尚偏移。新年龄支持磁地层学的沉积年代学，该年代学表明内华达山脉和莫诺盆地对区域气候变化的准同步冰川和水文响应，湖泊充填和冰川积雪融化的间隔与春季日照峰值同相。
Sediments of the Wilson Creek Formation surrounding Mono Lake preserve a high-resolution archive of glacial and pluvial responses along the eastern Sierra Nevada due to late Pleistocene climate change. An absolute chronology for the Wilson Creek stratigraphy is critical for correlating the paleoclimate record to other archives in the western U.S. and the North Atlantic region. However, multiple attempts to date the Wilson Creek stratigraphy using carbonates and tephras yield discordant results due to open-system effects and radiocarbon reservoir uncertainties as well as abundant xenocrysts. New ion microprobe238U-230Th dating of the final increments of crystallization recorded by allanite and zircon autocrysts from juvenile pyroclasts yield ages that effectively date eruption of key tephra beds and delimit the timing of basal Wilson Creek sedimentation to the interval between 26.8±2.1 and 61.7±1.9ka. Tephra (Ash 15) erupted during the geomagnetic excursion originally designated the Mono Lake excursion yields an age of 40.8±1.9ka, indicating that the event is instead the Laschamp excursion. The new ages support a depositional chronology from magnetostratigraphy that indicates quasi-synchronous glacial and hydrologic responses in the Sierra Nevada and Mono Basin to regional climate change, with intervals of lake filling and glacial-snowpack melting that are in phase with peaks in spring insolation.