Seismic evidence of up to 200 m lake-level change in Southern Patagonia since Marine Isotope Stage 4
Seismic evidence of up to 200 m lake-level change in Southern Patagonia since Marine Isotope Stage 4
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DOI：
10.1111/j.1365-3091.2011.01296.x
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发表时间：
2012-04-01
期刊：
影响因子：
3.5
通讯作者：
Zolitschka, Bernd
中科院分区：
文献类型：
--
作者：
Gebhardt, Andrea Catalina;Ohlendorf, Christian;Zolitschka, Bernd
马尔湖拉古纳波特罗克艾克位于麦哲伦海峡(巴塔哥尼亚东南部)北部。地震反射剖面揭示了一段高度动态的古气候历史。在湖底以下约30至80米处的东部发现了沙丘，覆盖在较老的湖层之上，这表明该地区可能经历了干燥的条件和强烈的西风。这很可能与海洋同位素第四阶段南极冰芯中记录的一次重大尘埃事件有关。沙丘上覆盖着一系列古海岸线，表明在这一干旱时期之后建立的新湖的水位逐步演变，从而向更潮湿的条件转变。在最初的、快速的、阶梯式的湖平面上升之后，盆地变得更深、更宽，沉积在湖肩上的沉积物指向大约53.5ka之间的较长时期的湖平面高位。BP和30大卡。BP，最大湖平面比干燥地平线高约200米。这一高水位之后是一个年龄不确定的倒退阶段，尽管它一定发生在大约30大卡之间的某个时间。BP和6750年卡。BP。中全新世的干燥条件表现为湖平面的下降，导致湖肩上的盆地范围的侵蚀不整合。第二次阶梯式海侵发生在约5.8至5.4ka之间。BP和约4.7至4ka卡路里。BP与古海岸线在湖肩上的沉积再次不整合，表明了向更湿润条件的转变。
Maar lake Laguna Potrok Aike is located north of the Strait of Magellan (south-eastern Patagonia). Seismic reflection profiles revealed a highly dynamic palaeoclimate history. Dunes were identified in the eastern part of the lake at approximately 30 to 80 m below the lake floor, overlying older lacustrine strata, and suggest that the region experienced dry conditions probably combined with strong westerly winds. It is quite likely that this can be linked to a major dust event recorded in the Antarctic ice cores during Marine Isotope Stage 4. The dunes are overlain by a series of palaeo-shorelines indicating a stepwise water-level evolution of a new lake established after this dry period, and thus a change towards wetter conditions. After the initial, rapid and stepwise lake-level rise, the basin became deeper and wider, and sediments deposited on the lake shoulder at approximately 33 m below present-day lake level point towards a long period of lake-level highstand between roughly 53.5 ka cal. bp and 30 ka cal. bp with a maximum lake level some 200 m higher than the desiccation horizon. This highstand was then followed by a regressional phase of uncertain age, although it must have happened some time between approximately 30 ka cal. bp and 6750 yrs cal. bp. Dryer conditions during the Mid-Holocene are evidenced by a dropping lake level, resulting in a basin-wide erosional unconformity on the lake shoulder. A second stepwise transgression between ca 5.8 to 5.4 ka cal. bp and ca 4.7 to 4 ka cal. bp with palaeo-shorelines deposited on the lake shoulder unconformity again indicates a change towards wetter conditions.