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首页> 外文期刊>Quaternary geochronology >Optically stimulated luminescence dating of Ocean Drilling Program core 658B: Complications arising from authigenic uranium uptake and lateral sediment movement
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Optically stimulated luminescence dating of Ocean Drilling Program core 658B: Complications arising from authigenic uranium uptake and lateral sediment movement

机译：海洋钻探计划（Ocean Drilling Program）核心658B的光学激发发光测年：自生铀吸收和横向泥沙运动引起的并发症

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Ocean Drilling Program Site 658 lies under the North African summer dust plume, and ought to be an ideal target for optically stimulated luminescence (OSL) dating, since the main clastic input is far-travelled Saharan dust. However, OSL ages for coarse silt-sized quartz (40-63 mu m) are systematically lower than independent age estimates when dose rates are calculated using a model which assumes detrital U-238, Th-232 and K-40 and excess Th-230 and Pa-231. Ages which are in good agreement with independent age control are obtained from the coarse silt samples when a correction for authigenic uranium uptake is incorporated into the dose rate model. Authigenic uranium uptake occurs under reducing conditions, which are common at the sediment water interface, and some degree of authigenic uranium correction may be required for most marine sediments. Using this revised dose rate model, ages produced using fine silt-sized quartz (4-11 mu m) are up to 100% older than both independent and coarse silt ages. In addition, the fine silt ages show a consistent pattern of age decrease with depth over 1.5 m of core. Th-230 data from Site 658 indicate that this site receives 3 times more sediment laterally than vertically. It is concluded that the fine silt at Site 658 contains a substantial reworked component, making it unsuitable for dating. Conversely the coarse silt fraction, which settles through water at similar to 40 times the rate of fine silt, appears to be derived from dust input over the site at the time of deposition. Since prominent nepheloid (cloudy) layers occur in various deep ocean basins, and the material suspended in these layers often consists of reworked fine silt-sized sediments, coarser material should be dated where possible. (C) 2015 Elsevier B.V. All rights reserved.
机译：海洋钻探计划站点658位于北非夏季尘埃羽流之下，并且应该是光学激发发光（OSL）测年的理想目标，因为主要碎屑输入是散布的撒哈拉尘埃。但是，当使用假设U-238，Th-232和K-40碎屑严重的Th-232模型时计算剂量率时，粗粉砂石英（40-63μm）的OSL年龄总体上低于独立年龄估计。 230和Pa-231。当将自生铀吸收的校正量纳入剂量率模型时，可以从粗粉砂样品中获得与独立年龄控制高度吻合的年龄。自生铀的吸收发生在沉积物水界面常见的还原条件下，大多数海洋沉积物可能需要一定程度的自生铀校正。使用此修订的剂量率模型，使用细粉砂大小的石英（4-11微米）产生的年龄比独立粉砂年龄和粗粉沙年龄都高100％。此外，细粉砂年龄随着岩心1.5 m以上的深度显示出一致的年龄下降规律。来自站点658的Th-230数据表明，该站点的横向沉积物比垂直沉积物多3倍。结论是，站点658处的细粉砂含有大量返工成分，因此不适合定年。相反，通过水沉降的粗粉砂分数约为细粉砂速率的40倍，这似乎是由于沉积时在该位置上输入的粉尘引起的。由于在不同的深海盆地中都出现突出的星状（云状）层，并且这些层中悬浮的物质通常由重制的粉砂大小的沉积物组成，因此应标明较粗的物质。 （C）2015 Elsevier B.V.保留所有权利。

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