Palaeotopography of a Palaeolithic landscape at AUTHORS: Bestwood 1, South Africa, from ground-penetrating Konstantinos S. Papadimitrios1 Carl-Georg Bank1 radar and magnetometry Steven J. Walker2 Michael Chazan3,4 AFFILIATIONS: In order to investigate the buried landscape at the Fauresmith locality of Bestwood 1, outside the town of Kathu 1Department of Earth Sciences, in the Northern Cape Province, we performed ground-penetrating radar and magnetometry surveys across the University of Toronto, Ontario, Canada sand-filled central portion of the valley. The radar images a strong continuous reflector which we can assign to 2Department of Archaeology, the boundary between the Kalahari sands and underlying Banded Ironstone Formation gravels. Moreover, the University of Cape Town, Cape Town, thickness of the sand delineates a buried depression in the centre of the valley with flat plateaus at the sides. South Africa 3Department of Anthropology, Subtracting the sand thickness from the current topography produces a map of a small stream channel in the University of Toronto, Ontario, Canada northern part of the valley. Analysis of the magnetic gradient data allows us to extend this buried channel further 4Institute of Evolutionary Studies, to the south. Our geophysical survey provides a valuable contribution towards understanding the context of University of the Witwatersrand, hominin occupation along the banks of a small stream in the Kathu Complex. Johannesburg, South Africa Significance: CORRESPONDENCE TO: • We provide an example of combining two geophysical methods to map overburden thickness, useful Michael Chazan for archaeological landscape interpretation. EMAIL: [email protected] Introduction The Kathu Complex is a series of archaeological localities – Kathu Pan, Kathu Townlands and Bestwood – that DATES: Received: 16 Mar. 2017 together represent evidence of extraordinarily intensive occupation through the Earlier Stone Age (Acheulean) and 1-4 Revised: 06 June 2017 the transitional Earlier Stone Age to Middle Stone Age (Fauresmith). The sheer scale of these localities is unusual Accepted: 06 Oct. 2018 and poses challenges for both research and conservation. Published: 30 Jan. 2019 In the research presented here, ground-penetrating radar (GPR) and magnetic gradiometer surveys were conducted to create a 3D subsurface map of the buried Pleistocene landscape at the site of Bestwood 1. GPR was used to HOW TO CITE: Papadimitrios KS, Bank C-G, Walker map and define subsurface boundaries while gradiometer data, correlated to depth from GPR data, were used to increase the extent of mapping. The study site, Bestwood 1 (27°42 S 23°03 E, UTM zone 34 S), is situated in SJ, Chazan M. Palaeotopography of a ′ ′ Palaeolithic landscape at Bestwood 1, a south-facing valley in an isolated hill infilled with Kalahari sands. This hill is located at the western edge of the South Africa, from ground-penetrating Kuruman Hills where this formation grades into the southern edge of the Kalahari Basin3,4 (Figure 1). The sandy radar and magnetometry. S Afr J base of the valley is mostly level over its entire north–south extent of 2.8 km (Figure 2a). Valley walls slope gently Sci. 2019;115(1/2), Art. #4793, 7 pages. https://doi.org/10.17159/ and are composed of Banded Ironstone Formation (BIF) bedrock overlain by scree consisting of flat weathered sajs.2019/4793 slabs of BIF that includes large numbers of stone tools. The stone tools found within the exposed scree are heavily weathered. The boundary between the scree deposits on the hill slopes and the sand infill is gradual and sand has ARTICLE INCLUDES: infiltrated between the BIF slabs in the lower slopes. Peer review ☒ Supplementary material Quarrying for sand and gravel at the southern end of the valley has exposed a stratigraphic sequence of Kalahari ☐ sands with a depth of 2–3 m overlying a deep deposit of BIF gravels extending to a depth of at least 15 m. The DATA AVAILABILITY: interface between the two stratigraphic units is sharp although there is some infiltration of sand into the top of the Open data set ☐ gravel unit and small fragments of BIF in the sands (Figure 2b). All data included ☐ On request from authors Excavations in two areas 100 m apart in a sand quarry at the south end of the valley have exposed large surfaces ☒ Not available (31 m2 in the eastern Block 1 excavation and 14 m2 in the western Block 2 excavation) blanketed by artefacts ☐ Not applicable characteristic of the Fauresmith industry (Figure 2c). In both areas the artefacts lie at the interface between the ☐ Kalahari sands and underlying gravels. Unlike the artefacts found on the hill slopes, those found in the quarry EDITOR: excavation are in good condition with virtually no weathering. These artefacts show little to no signs of mechanical Maryna Steyn damage such as rounded or chipped edges and rarely evidence of differential patination on surfaces. The artefacts are found in a single horizon with some artefacts embedded in clays at the top of the underlying gravel horizon KEYWORDS: (Figure 2b). There is no ‘stacking’ of objects and artefacts are mostly lying horizontally. Because of the scale of archaeology; geophysical survey; occupation, the Bestwood 1 occupation cannot be considered a clearly bounded archaeological site and is best Fauresmith; human evolution; landscape archaeology treated as a palaeotopography of early human occupation. There is no current evidence of areas of high density of artefacts amidst a background of low density, the so-called ‘scatter and patches’, but rather what emerges FUNDING: is a fairly continuous density of artefacts across the excavated areas (see comparison of excavation areas in Canadian Social Science and Table 1). Given that the entire area of the surveyed valley is about 2.8x0.4 km, and that to date similar densities of Humanities Research Council; artefacts have been found in all areas tested, the potential scale of hominin occupation is massive. The goal of the University of Toronto International geophysical survey was to create a 3D map of the contact between the gravels and the overlying sands across the Research Excursions Program entire valley and thus to determine the morphology of the potential landscape of hominin occupation. © 2019. The Author(s). Published under a Creative Commons Attribution Licence. Research Article Volume 115| Number 1/2 https://doi.org/10.17159/sajs.2019/4793 1 January/February 2019 Palaeotopography of a Palaeolithic landscape Page 2 of 7 a b Figure 1: Map showing the geological context of the study area along with the sites mentioned in the text. The banded ironstone (grey) of the Kuruman Hills (Early Proterozoic Transvaal Supergroup) overlies the dolomite (light blue) of the Ghaap Plateau to the east and the Maremane Dome to the west. The Langeberg Hills to the east are outcroppings of quartzite (orange, Late Proterozoic Olifantshoek Supergroup). Between the Langeberg and Kuruman Hills there are exposures of c lavas (green, Middle Proterozoic Transvaal Supergroup). The Kuruman Hills are at the southern margin of the Kalahari Basin and the surface deposits to the north are dominated by sands with occasional surface calcretes. The major drainage is the Kuruman River. Table 1: Comparison of lithic assemblages from excavation areas and test pits. Does not include small flakes and fragments from sieve. Block 1 Block 2 GPR 1 GPR 2 31 m2 14 m2 1 m2 1 m2 Biface and biface fragment† 33 25 1 – Biface tip 3 1 – – Figure 2: Images of Bestwood 1. (a) View of the valley floor. (b) Stratigraphic profile of Block 2 (Western Block) excavation Chopper 1 – – – showing the contact between the gravels and the overlying Polyhedron 1 – – – sands. (c) Block 1 (Eastern Block) excavation showing artefacts, including a hand axe, in situ, at the top of the gravels. Flake 622 422 14 18 Flake fragment 197 179 5 3 Methodology Blade 29 11 1 2 Both ground-penetrating radar and magnetometry surveys were Blade fragment 9 17 1 – undertaken across the sand-filled central portion of the valley. Based Retouched flake 5 4 1 – on the results of the geophysical survey, two test pits were excavated to determine the accuracy with which the survey identified the boundary Core 41 34 2 – between the gravels and the sands and whether the archaeological Slab 25 6 4 1 evidence of hominin occupation extends beyond the area of the sand quarry at the southern end of the valley. Slab fragment 19 – – – Modified slab 22 5 – – Ground-penetrating radar The GPR surveys were conducted using a GSSI SIR-3000 connected Modified slab fragment 4 1 – – to a 200-MHz centre frequency antenna with attached survey wheel (Geophysical Survey Systems Inc., Nashua, New Hampshire, USA). GPR, ground-penetrating radar Traces were recorded every 50 mm in two-way travel time (TWTT, in † Includes all bifacially worked pieces including handaxes and roughouts/preforms nanoseconds) along profiles by moving the GPR antenna in as straight Research Article Volume 115| Number 1/2 https://doi.org/10.17159/sajs.2019/4793 2 January/February 2019 Palaeotopography of a Palaeolithic landscape Page 3 of 7 a c b d e Figure 3: Topographic map of Bestwood 1 with ground-penetrating radar (GPR) and magnetic lines shown along with excavation areas and test pits. (a) GPR shown in red; magnetic lines shown in yellow; grids are marked by brown boxes; the GPR-magnetics correlation line is marked by yellow circles at each end; excavation areas marked in green. Note that one test pit was excavated in each of the grid areas. (b) Satellite image; white box shows the area covered by the topographic map. (c) Grids and excavation areas; (d) GPR lines; and (e) magnetic lines. Research Article Volume 115| Number 1/2 https://doi.org/10.17159/sajs.2019/4793 3 January/February 2019 Palaeotopography of a Palaeolithic landscape Page 4 of 7 a line as was possible.