Extending the aridity record of the Southwest Kalahari: current problems and future perspectives
Extending the aridity record of the Southwest Kalahari: current problems and future perspectives
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DOI：
10.1016/s1040-6182(03)00013-2
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发表时间：
2003-01-01
影响因子：
2.2
通讯作者：
Singhvi, AK
中科院分区：
文献类型：
--
作者：
Bateman, MD;Thomas, DSG;Singhvi, AK
一个广泛的发光为基础的年代框架，使喀拉哈里沙漠的扩张和收缩的重建在过去的50 ka。然而，这一年表主要是基于近地表坑和沉积物暴露。这些是景观上最容易重新激活和重置发光测年“时钟”的点。这被证明是一个限制性的功能，延长古环境重建进一步回到过去的时间。验证这一点的一种方法是对只有在重要阶段才变得活跃的沙漠边缘地区进行采样。另一种方法是寻找和取样深层地层暴露。卡拉哈里西南部Hotazel的Mamatwan锰矿符合这两个标准。该网站的发光测年显示，上部沉积单元跨越至少过去60万年的初步年龄估计，从底层胶结风成单元追溯到最后一个间冰期及以后。Mamatwan的结果与西南卡拉哈里线性沙丘的新数据和先前发表的数据相当，但可以追溯到更远的地方。对西南喀拉哈里的发光年龄的整个数据集的分析得出了重要的推论，表明不同的风成形式（1）在过去的不同时间尺度上活跃，（2）对环境变化具有不同的敏感性，（3）具有不同的时间尺度，它们记录和保存古环境记录。这意味着，未来的光激发光工作和古环境重建必须考虑站点位置及其与沙漠边缘和沉积物沉积风格的关系，以便可以最佳地了解干旱记录的分辨率和持续时间。(C)2003 Elsevier Science Ltd和INQUA。All rights reserved.
An extensive luminescence-based chronological framework has allowed the reconstruction of expansions and contractions of the Kalahari Desert over the last 50 ka. However, this chronology is largely based on near-surface pits and sediment exposures. These are the points on the landscape most prone to reactivation and resetting of the luminescence dating 'clock'. This is proving to be a limiting feature for extending palaeoenvironmental reconstructions further back in time. One way to obviate this is to sample desert marginal areas that only become active during significant and phases. An alternative is to find and sample deep stratigraphic exposures. The Mamatwan manganese mine at Hotazel in the SW Kalahari meets both these criteria. Luminescence dating of this site shows the upper sedimentary unit to span at least the last 60 ka with tentative age estimates from underlying cemented aeolian units dating back to the last interglacial and beyond. Results from Mamatwan are comparable to new and previously published data from linear dunes in the SW Kalahari but extend back much further. Analysis of the entire data set of luminescence ages for the SW Kalahari brings out important inferences that suggest that different aeolian forms (1) have been active over different time scales in the past, (2) have different sensitivities to environmental changes and (3) have different time scales over which they record and preserve the palacoenvironmental record. This implies that future optically stimulated luminescence work and palaeoenvironmental reconstructions must consider both site location and its relationship to desert margins and sediment depositional styles, so that the resolution and duration of the aridity record can be optimally understood. (C) 2003 Elsevier Science Ltd and INQUA. All rights reserved.