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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Complex exposure histories of chert clasts in the late Pleistocene shorelines of Lake Lisan, southern israel
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Complex exposure histories of chert clasts in the late Pleistocene shorelines of Lake Lisan, southern israel

机译：以色列南部利桑湖更新世晚期海岸线的白垩质碎屑的复杂暴露历史

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摘要

Activities of ~(26)Al and ~(10)Be in five chert clasts sampled from two beach ridges of late Pleistocene Lake Lisan, precursor of the Dead Sea in southern Israel, indicate low rates of chert bedrock erosion and complex exposure, burial, and by inference, transport histories. The chert clasts were derived from the Senonian Mishash Formation, a chert-bearing chalk, which is widely exposed in the Nahal Zin drainage basin, the drainage system that supplied most of the material to the beach ridges. Simple exposure ages, assuming only exposure at the beach ridge sampling sites, range from 35 to 354 ky; using the ratio ~(26)Al/~(10)Be, total clast histories range from 0.46 to 4.3 My, unrelated to the clasts' current position and exposure period on the late Pleistocene beach ridges, 160-177 m below sea level. Optically stimulated luminescence dating of fine sediments from the same and nearby beach ridges yielded ages of 20.0 ± 1.4 ka and 36.1 ± 3.3 ka. These ages are supported by the degree of soil development on the beach ridges and correspond well with previously determined ages of Lake Lisan, which suggest that the lake reached its highest stand around 27000 cal. years BP. If the clasts were exposed only once and than buried beyond the range of significant cosmogenic nuclide production, then the minimum initial exposure and the total burial times before delivery to the beach ridge are in the ranges 50-1300 ky and 390-3130 ky respectively. Alternatively, the initial cosmogenic dosing could have occurred during steady erosion of the source bedrock. Back calculating such rates of rock erosion suggests values between 0.4 and 12 m My~(-1). The relatively long burial periods indicate extended sediment storage as colluvium on slopes and/or as alluvial deposits in river terraces. Some clasts may have been stored for long periods in abandoned Pliocene and early Pleistocene routes of Zahal Zin to the Mediterranean before being transported again back into the Nahal Zin drainage system and washed on to the shores of Lake Lisan during the late Pleistocene.
机译：在以色列南部死海的前更新世晚期的里桑湖（利桑湖）的两个海滩山脊中取样的五个硅质岩屑中，〜（26）Al和〜（10）Be的活动表明，硅质岩基岩的侵蚀率较低，且复杂的暴露，埋葬，并据此推断出运输历史。石碎屑来自于含on石的白垩纪锡诺期Mishash地层，该白垩岩广泛暴露于Nahal Zin流域，该流域向海滩山脊提供了大部分物质。假设仅在海滩山脊采样点进行暴露，则简单暴露年龄为35至354 ky;使用比率（〜26）Al /〜（10）Be，总碎屑历史范围为0.46至4.3 My，与碎屑在海平面以下160-177 m的更新世晚期海滩山脊的当前位置和暴露时间无关。来自相同和附近海滩山脊的细小沉积物的光激发发光年代测定得出的年龄分别为20.0±1.4 ka和36.1±3.3 ka。这些年龄受到海滩山脊上土壤发育程度的支持，并与先前确定的利桑湖年龄相吻合，这表明该湖达到了27000 cal的最高水位。年BP。如果这些碎屑仅暴露一次，而不是被掩埋在明显的宇宙成因核素生产范围之外，那么在被交付到海滩山脊之前，最小的初始暴露和总的掩埋时间分别在50-1300 ky和390-3130 ky的范围内。另外，最初的宇宙成因剂量可能发生在源岩的稳定侵蚀过程中。反算这样的岩石侵蚀速率表明，其值在0.4至12 m My〜（-1）之间。相对较长的埋葬期表明，泥沙的扩展存储为斜坡上的砾石和/或河流阶地上的冲积物。一些碎屑可能已经在Zahal Zin到地中海的废弃的上新世和早更新世路线中长期保存，然后再被运回Nahal Zin排水系统，并在更新世晚期被洗至Lisan湖岸。

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