Duller Geoff A T, Tooth Stephen, Barham Lawrence, Tsukamoto Sumiko
Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, SY23 3DB, UK.
Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, SY23 3DB, UK.
J Hum Evol. 2015 Aug;85:111-25. doi: 10.1016/j.jhevol.2015.05.003. Epub 2015 Jun 12.
Fluvial deposits can provide excellent archives of early hominin activity but may be complex to interpret, especially without extensive geochronology. The Stone Age site of Kalambo Falls, northern Zambia, has yielded a rich artefact record from dominantly fluvial deposits, but its significance has been restricted by uncertainties over site formation processes and a limited chronology. Our new investigations in the centre of the Kalambo Basin have used luminescence to provide a chronology and have provided key insights into the geomorphological and sedimentological processes involved in site formation. Excavations reveal a complex assemblage of channel and floodplain deposits. Single grain quartz optically stimulated luminescence (OSL) measurements provide the most accurate age estimates for the youngest sediments, but in older deposits the OSL signal from some grains is saturated. A different luminescence signal from quartz, thermally transferred OSL (TT-OSL), can date these older deposits. OSL and TT-OSL results are combined to provide a chronology for the site. Ages indicate four phases of punctuated deposition by the dominantly laterally migrating and vertically aggrading Kalambo River (∼500-300 ka, ∼300-50 ka, ∼50-30 ka, ∼1.5-0.49 ka), followed by deep incision and renewed lateral migration at a lower topographic level. A conceptual model for site formation provides the basis for improved interpretation of the generation, preservation, and visibility of the Kalambo archaeological record. This model highlights the important role of intrinsic meander dynamics in site formation and does not necessarily require complex interpretations that invoke periodic blocking of the Kalambo River, as has previously been suggested. The oldest luminescence ages place the Mode 2/3 transition between ∼500 and 300 ka, consistent with other African and Asian sites where a similar transition can be found. The study approach adopted here can potentially be applied to other fluvial Stone Age sites throughout Africa and beyond.
河流沉积物能够提供有关早期人类活动的优质档案，但解读起来可能很复杂，尤其是在缺乏广泛地质年代学研究的情况下。赞比亚北部的卡兰博瀑布石器时代遗址，已从主要的河流沉积物中获得了丰富的人工制品记录，但其重要性一直受到遗址形成过程的不确定性以及年代学有限的限制。我们在卡兰博盆地中心的新研究利用发光技术来确定年代，并对遗址形成过程中涉及的地貌和沉积过程提供了关键见解。挖掘工作揭示了河道和泛滥平原沉积物的复杂组合。单颗粒石英光激发发光（OSL）测量为最年轻的沉积物提供了最准确的年龄估计，但在较老的沉积物中，一些颗粒的OSL信号已饱和。来自石英的另一种发光信号，热传递OSL（TT - OSL），可以测定这些较老沉积物的年代。将OSL和TT - OSL结果结合起来，为该遗址提供了一个年代序列。年代显示，主要横向迁移和垂直加积的卡兰博河有四个间断沉积阶段（约50万 - 30万年，约30万 - 5万年，约5万 - 3万年，约1.5万 - 0.49万年），随后是深切蚀作用，并在较低地形水平上重新进行横向迁移。一个遗址形成的概念模型为改进对卡兰博考古记录的产生、保存和可见性的解释提供了基础。该模型强调了内在曲流动力学在遗址形成中的重要作用，并不一定需要像之前所建议的那样，采用涉及卡兰博河周期性阻塞的复杂解释。最古老的发光年代将模式2/3的转变定在约50万至30万年之间，这与其他能发现类似转变的非洲和亚洲遗址一致。这里采用的研究方法有可能应用于非洲及其他地区的其他河流石器时代遗址。
