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首页> 外文期刊>Quaternary geochronology >Dating Pleistocene deltaic deposits using in-situ Al-26 and Be-10 cosmogenic nuclides
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Dating Pleistocene deltaic deposits using in-situ Al-26 and Be-10 cosmogenic nuclides

机译：使用原位Al-26和Be-10宇宙成因核素约会更新世三角洲沉积物

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摘要

The present study aims at testing the possibility of using the in-situ cosmogenic burial dating technique on deltaic deposits. The sequence analyzed is exposed along the Ligurian coast (north-west Italy) and is made of proximal marine and continental deposits previously considered Pliocene or Plio-Quaternary in age. In the study area two allostratigraphic units were recognized. The lower unit represents the evolution of a small coarse-grained delta developed in a fjord or embayment environment. The coarsening/shallowing upward trend observed within the sections, from bottom to top, suggests that the delta prograded rapidly in the landward portion of the canyon placed opposite to the paleo-river outlet. Within the deltaic sequence the transgressive and highstand system tracts were recognized. The unit 2 is composed by several alluvial fan systems deposited in small incised valleys developed within the previously, uplifted deltaic deposits and successively incised by a braided river system. In-situ produced cosmogenic nuclides were used in order to date the age of the deposition of the deltaic deposits. Results suggest that the studied deltaic sediments belonging to the unit 1 were deposited between 1,300,000 and 200,000 year ago thus during the Lower to Middle Pleistocene, whereas the unit 2 was deposited during the Middle Pleistocene as a consequence of a tectonically driven uplift phase. Furthermore samples collected within the prograding part of the delta show the higher denudation rates. The obtained results demonstrate that burial ages and related erosion rates inferred from cosmogenic nuclides concentrations can be considered as a very useful tool to reconstruct the sea level changes over the past 1 million year. (C) 2015 Elsevier B.V. All rights reserved.
机译：本研究旨在测试在三角洲沉积物中使用原位宇宙成因埋葬年代测定技术的可能性。所分析的层序沿利古里亚海岸（意大利西北部）暴露，并由年龄上被认为是上新世或上新世第四纪的近海海洋和大陆沉积组成。在研究区域中，识别出两个同化地层单位。下部单元代表在峡湾或巢穴环境中形成的小粗粒三角洲的演化。在从底部到顶部的剖面中观察到的粗化/浅化上升趋势表明，三角洲在与古河出口相对的峡谷的陆上部分迅速发展。在三角洲序列内，海侵和高位系统域被识别。单元2由几个冲积扇系统组成，这些系统沉积在先前已隆起的三角洲沉积物内形成的小切谷中，并随后由辫状河系系统切开。为了确定三角洲沉积物的沉积年代，使用了原位产生的宇宙成因核素。结果表明，被研究的属于第一单元的三角洲沉积物是在１３０万到２０万年前之间沉积的，因此是在下至中更新世期间沉积的，而第二单元的沉积是由于构造驱动的隆升期在中更新世沉积的。此外，在三角洲渐进部分收集的样品显示出较高的剥蚀率。获得的结果表明，从宇宙成因核素浓度推断出的埋葬年龄和相关的侵蚀速率可以被认为是重建过去一百万年海平面变化的非常有用的工具。 （C）2015 Elsevier B.V.保留所有权利。

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