New investigations at Kalambo Falls, Zambia: Luminescence chronology, site formation, and archaeological significance

Abstract

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.

Investigation of the applicability of standardised growth curves for OSL dating of quartz from Haua Fteah cave, Libya

“…It is crucial, therefore, to investigate the variability in the DRCs of single-grain measurements if a significant proportion of measured and accepted grains are rejected due to saturation. Future studies are required to confirm the validity of D e determination based on the 'medium' and 'later' groups for samples older than those investigated in this study (D e values >140 Gy), given the problems of D e estimation in the high-dose range of quartz OSL for samples from some other regions (e.g., Lai, 2010;Lowick and Preusser, 2011;Chapot et al, 2012;Duller et al, 2015).…”

Aerial map demonstrates erosional patterns and changing topography at Isimila, Tanzania (with corrigendum)

“…[11][12][13] Moreover, optically stimulated luminescence dating of deposits at Kalambo Falls suggests multiple, temporally distinct occupations beginning as early as 500 kya. 14 Isimila may provide a unique temporal and geographic window into the Acheulean at the Acheulean-MSA transition in East Africa, although new dates are necessary to better contextualise the site. Within Tanzania, the lower beds of Isimila (Sands 3-5) are broadly contemporaneous with the Ngaloba Beds at Laetoli 15 , which yielded Laetoli Hominid 18 (LH 18), a partial Homo cranium 16,17 .…”

Extended range luminescence dating of quartz and alkali-feldspar from aeolian sediments in the eastern Mediterranean

“…KR-17 and DF-13; Table S2). High residual doses of over 100 Gy were reported elsewhere for fluvial sediments (Hu et al, 2010;Duller et al, 2015), implying low suitability of the TT-OSL signal for dating such sediments. Nevertheless, samples of early-middle Pleistocene age from different sedimentation environments are in agreement with control ages (Arnold et al, 2015).…”