Holocene sedimentary architecture and paleoclimate variability at Mono Lake, California
Holocene sedimentary architecture and paleoclimate variability at Mono Lake, California
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加利福尼亚州莫诺湖的全新世沉积结构和古气候变化
DOI：
10.1130/2020.2536(19
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
S. Starratt
中科院分区：
文献类型：
--
作者：
S. Zimmerman;S. Hemming;S. Starratt
莫诺湖位于内华达山脉东侧的一个内部排水盆地，它对影响山区降水（主要以积雪形式）的气候变化很敏感。从莫诺陨石坑喷发的粗火山灰以及大约 300 年前保哈岛隆起对湖底的破坏阻碍了从湖中回收岩心的努力。在这项研究中，我们描述了 2007 年、2009 年和 2010 年最近三个活动的岩心地层学，以及火山灰和扰动沉积物的范围和深度。在这些岩心中最成功的 BINGO-MONO10-4A-1N（BINGO/10-4A，2.8 m 水深）中，我们使用岩心地层学、地球化学、放射性碳测年和地层学来表明，该岩心记录了几乎所有全新世的不同比例的碎屑、火山和自生沉积物。大约是南莫诺火山灰。 1350 卡路里年血压（在公元 1950 年之前校准）和 600 年历史的北莫诺-伊尼奥火山灰存在于 BINGO/10-4A 核心中，还有一些更古老、尚未鉴定的火山灰。据推测，层状泥浆表明全新世早期存在一个相对较深的湖泊（距离核心地点 10 m），与该时期该地区的许多记录类似。中全新世和晚全新世单元层理更粗，粒度更粗，自生碳酸盐碎屑数量更多且变化更大，这表明湖泊水位较低，可能是由于有效湿度较低。据推断，湖水位极低可能与极端干旱有关，发生在距今 3500 至 2100 年之间的某个时间。这个间隔可能对应于先前记录的滨海低位和区域性的全新世晚期干旱期。 BINGO/10-4A 核心没有保存中世纪气候异常、小冰河时期和历史时期的完整记录，可能是由于其近岸位置而受到侵蚀。
Mono Lake occupies an internally drained basin on the eastern flank of the Sierra Nevada, and it is sensitive to climatic changes affecting precipitation in the mountains (largely delivered in the form of snowpack). Efforts to recover cores from the lake have been impeded by coarse tephra erupted from the Mono Craters, and by disruption of the lake floor due to the uplift of Paoha Island ~300 yr ago. In this study, we describe the stratigraphy of cores from three recent campaigns, in 2007, 2009, and 2010, and the extents and depths of the tephras and disturbed sediments. In the most successful of these cores, BINGO-MONO10-4A-1N (BINGO/10-4A, 2.8 m water depth), we used core stratigraphy, geochemistry, radiocarbon dates, and tephrostratigraphy to show that the core records nearly all of the Holocene in varying proportions of detrital, volcanic, and authigenic sediment. Both the South Mono tephra of ca. 1350 cal yr B.P. (calibrated years before A.D. 1950) and the 600-yr-old North Mono–Inyo tephra are present in the BINGO/10-4A core, as are several older, as-yet-unidentified tephras. Laminated muds are inferred to indicate a relatively deep lake (³10 m over the core site) during the Early Holocene, similar to many records across the region during that period. The Middle and Late Holocene units are more coarsely bedded, and coarser grain size and greater and more variable amounts of authigenic carbonate detritus in this interval are taken to suggest lower lake levels, possibly due to lower effective wetness. A very low lake level, likely related to extreme drought, is inferred to have occurred sometime between 3500 and 2100 cal yr B.P. This interval likely corresponds to the previously documented Marina Low Stand and the regional Late Holocene Dry Period. The BINGO/10-4A core does not preserve a complete record of the period encompassing the Medieval Climate Anomaly, the Little Ice Age, and the historical period, probably due to erosion because of its nearshore position.