Paloma De La Peña
email: paloma.delapenya@gmail.com

Fernando Colino

Francesco D'errico

Lyn Wadley

William E Banks

Dominic Stratford

Lucinda Backwell

L Gerardo

Vega Toscano

Lithic technological and spatial analysis of the final Pleistocene at Border Cave, South Africa

Keywords: Lithic, technology, spatial distribution, particle size, Middle Stone Age

This contribution focuses on the recently excavated lithic assemblage from Border Cave Members 1 RGBS, 3 BS, 2 WA and 2 BS. These members were attributed by Beaumont to the Howiesons Poort and post-Howiesons Poort Industries of the southern African Middle Stone Age. Here we consider lithics as indicators of cultural behaviour, site formation processes, and occupation intensity. As such, the assemblage is explored in depth through lithic technology attribute analysis, particle size distribution, and spatial analysis. These lines of inquiry follow the new allostratigraphic divisions proposed for the deposits by Stratford and colleagues. Results show that the lower members share a degree of similarity in terms of flaking strategies and raw material selection, whereas the upper members record a dissimilar set of features, with differentiation between them. The technological and spatial analyses suggest the sporadic presence of different groups at the site, each characterized by distinct sets of knapping techniques and methods but employing related knapping strategies and using similar raw materials.

The interpretation of these members as a palimpsest of sporadic occupation is supported by the low number of archaeological finds by sediment volume. The evidence at hand does not support a Howiesons Poort attribution for the lowest members. The data show that lithics from part of Member 2 WA and 2 BS are in accordance with those of the recently defined Sibudan technocomplex.

INTRODUCTION

Border Cave has one of the longest archaeological stratigraphic sequences in southern Africa with a record that covers Marine Isotopic Stages (MIS) 7 to 2. The stratigraphic, archaeological, and chronometric analyses of Peter [START_REF] Beaumont | Border Cave[END_REF] and subsequent researchers have made it a reference site on the African continent. Furthermore, this site has been instrumental in demonstrating the ancient chronology of the Middle Stone Age (MSA) [START_REF] Beaumont | On a new radiocarbon chronology for Africa South of the Equator[END_REF], which at the time was not clearly associated with the Pleistocene (Thackeray, 1992 and references therein). The [START_REF] Beaumont | Border Cave[END_REF] excavations also showed for the first time the exceptional degree of organic preservation in a southern African MSA context. Such remarkable plant preservation was later documented at other southern African sites such as Klasies River [START_REF] Deacon | Planting an idea: an archaeology of Stone Age gatherers in South Africa[END_REF], Strathalan B [START_REF] Opperman | A 22 000 year-old Middle Stone Age camp site with plant food remains from the north-eastern Cape[END_REF][START_REF] Opperman | Strathalan Cave B, north-eastern Cape Province, South Africa: evidence for human behaviour 29,000-26,000 years ago[END_REF] and Sibhudu [START_REF] Wadley | Middle Stone Age bedding construction and settlement patterns at Sibudu, South Africa[END_REF]. The remarkable plant preservation at Border Cave has recently been corroborated following palaeobotanical investigations, which documented the oldest known evidence of grass bedding construction and cooked starchy rhizomes (Wadley et al., 2020a, b;[START_REF] Sievers | Plant bedding construction between 60,000 and 40,000 years ago at Border Cave, South Africa[END_REF]. Border Cave has also been instrumental in defining a putative precocious stage of the Later Stone Age [START_REF] Beaumont | On a new radiocarbon chronology for Africa South of the Equator[END_REF], but see de la Peña 2015a and [START_REF] Bader | Rethinking the Middle to Later Stone Age transition in southern Africa -A perspective from the highveld of Eswatini[END_REF]. In addition, at this site several human remains and a burial with an associated ornament was documented (Beaudet et al, this volume and d'Errico and Backwell, 2016 for a synthesis of human remains at the site). All of these aspects have made Border Cave a key site in the debate about Homo sapiens cultural behaviour in a specific biome of southern Africa the Indian Ocean coastal belt, which was not particularly well known until very recently [START_REF] Will | Characterizing the Late Pleistocene MSA lithic technology of Sibudu, KwaZulu-Natal, South Africa[END_REF][START_REF] Bader | Recent research on the MSA in KwaZulu-Natal, South Africa[END_REF].

In this work, an in-depth technological and spatial analysis of the lithic artefacts from Members 1 RGBS to 2 BS (~74-44 ka) is presented. These members were attributed to MSA 2/Howiesons Poort (HP) and MSA 3/post-Howiesons Poort industries in previous works [START_REF] Beaumont | Modern man in sub-Saharan Africa prior to 49 000 years BP: a review and evaluation with particular reference to Border Cave[END_REF][START_REF] Grün | Border Cave revisited: a revised ESR chronology[END_REF][START_REF] Grün | On the age of Border Cave 5 human mandible[END_REF][START_REF] Villa | Border Cave and the beginning of the Later Stone Age in South Africa[END_REF]. The material described here was yielded from the recent excavations by Backwell and colleagues (2018, this volume) that commenced in 2015.

Stone tools, objectives, and summary of research questions

Because lithic production at Border Cave informed the structure of this investigation, it is important to state how the lithics were understood in this analysis. Stone tools can provide information on site formation and cultural behaviour, hence our analysis focused on three main aspects of archaeological enquiry, namely lithics as indicators of 1) cultural behaviour, 2) taphonomy, and 3) occupation intensity.

1. Lithics as cultural behaviour indicators are elicited through an in-depth technological analysis following the chaîne opératoire approach (see [START_REF] Karlin | Processus techniques et chaînes opératoires: Comment les préhistoriens s' approprient un concept élaboré par les ethnologues[END_REF][START_REF] Tostevin | Seeing Lithics: A Middle-Range Theory for Testing for Cultural Transmission in the Pleistocene[END_REF]. Stone tools reflect applied technological sequences and subsequent use and abandonment. Thus, this theoretical framework can provide insight into the selection of raw materials, manufacture, use, re-sharpening, and discard of all examined technological objects.

2. With regard to lithics as taphonomic indicators, the particle size distribution of all the lithics [START_REF] Schick | Stone Age Sites in the Making[END_REF][START_REF] Bertran | Particle size distribution of lithic assemblages and taphonomy of Palaeolithic sites[END_REF] (independently of their size) and the distribution of heating attributes [START_REF] Wadley | Responses of South African agate and chalcedony when heated experimentally, and the broader implications for heated archaeological minerals[END_REF] and residues were analysed. Stone Age-bearing cave and rock shelter sites are complex sedimentary environments. The formation of deposits are influenced by a combination of primary and secondary anthropogenic and natural processes [START_REF] Farrand | Sediments and stratigraphy in rockshelters and caves: A personal perspective on principles and pragmatics[END_REF][START_REF] Mallol | Cave and rock shelter sediments[END_REF][START_REF] Schiffer | Toward the identification of formation processes[END_REF][START_REF] Schick | Stone Age Sites in the Making[END_REF]. Natural processes, including sedimentary deposition, erosion, and post-depositional movement, can alter the spatial organization, composition, and chronological signal of the archaeological record [START_REF] Schick | Stone Age Sites in the Making[END_REF][START_REF] Schick | Experimentally-derived criteria for assessing hydrologic disturbance of archaeological sites[END_REF][START_REF] Bertran | Particle size distribution of lithic assemblages and taphonomy of Palaeolithic sites[END_REF][START_REF] Bertran | Perturbation assessment in archaeological sites as part of the taphonomic study: a review of methods used to document the impact of natural processes on site formation and archaeological interpretations[END_REF]). To measure the potential loss of such information, assessment of postdepositional disturbance need to be conducted. To do this, particle shape, size and density of lithics are the main physical criteria used to assess the degree of disturbance in the archaeological deposits analysed here.

3. Lithics as indicators of occupation intensity are explored by combining taphonomic data and spatial analyses. Through spatial analysis of the vertical and horizontal distribution of the lithic artefacts we identify areas of high and low density in order to extrapolate if they are correlated with anthropic or taphonomic processes. The main aims of this analysis are to test whether lithics can be used as proxies for site formation processes, as well as to identify areas of intense occupation using the spatial information acquired from our recent excavations. This exercise complements the in-depth stratigraphic facies and faunal analyses conducted by Stratford and colleagues (this volume). The spatial distribution study aims to understand the nature of the relationship between lithics from the different members and sub-member units examined here, and the synchronic and diachronic relationships between the lithic remains. Understanding these relationships makes it possible to interpret, on the one hand, the organization of the activities of the groups that occupied the cave during short-term events and, on the other, the relationship between these relatively short-term events and long-term events recorded in the stratigraphic sequence. This work is conditioned both by the activities of human groups (frequency, intensity, duration, etc.) and by non-anthropogenic site formation processes (origin, sedimentation rates, erosion, etc.). Therefore, spatial analysis can inform us about cultural behaviour, the modality of occupation, site formation processes, and the intricate interaction between them.

The specific objectives of this manuscript can be summarized in the following questions, associated with the three main aspects related to lithics just mentioned.

Regarding cultural behaviour: What are the main technological strategies represented in the different stratigraphic units? Can we group lithic assemblages according to members and sub-member units?

What are the technological continuities and/or discontinuities between contiguous members and submember units? Do the previous cultural attributions [START_REF] Beaumont | Border Cave[END_REF][START_REF] Beaumont | Contemplating old clues to the impact of future greenhouse climates in South Africa[END_REF][START_REF] Grün | Border Cave revisited: a revised ESR chronology[END_REF] correspond with the technological changes observed in the recently recovered lithic assemblages? Do we observe a punctuated evolution or a gradual continuum in lithic technology through time?

Regarding taphonomic indicators: What does particle size distribution tell us in comparison to experimental knapping assemblages? What are the differences between members and sub-member units regarding particle size? Is heating modification on lithic remains distributed evenly among the members and sub-member units? Are macroscopic residues distributed evenly among the members and sub-member units?

Regarding spatial analysis: How does the spatial distribution of lithics correspond with the member and sub-member unit divisions? More specifically, is there a correspondence between vertical distribution of the assemblages and the stratigraphic divisions? Are artefacts distributed randomly with respect to vertical and horizontal dimensions, or is it possible to distinguish concentrations?

The lithic variability recorded should be related to other lines of enquiry recently undertaken at the site, including the study of plant and faunal remains, taphonomy and stratigraphy [START_REF] Sievers | Plant bedding construction between 60,000 and 40,000 years ago at Border Cave, South Africa[END_REF]

Border Cave site location

Border Cave is situated in northern KwaZulu-Natal 82 km West of the Indian Ocean (27°1'19"S, 31°59'24"E). Named because of its proximity to the border with Eswatini (formerly Swaziland), the site is located in the Lebombo Mountains at the top of a steep cliff at an altitude of 600 masl (Figure 1).

The rock shelter is approximately 50 m wide, 35 m deep and with a West facing opening, overlooking the Eswatini lowveld. The cave formed in the Lower Jurassic felsic extrusive rocks of the Jozini Formation, Lebombo Group, approximately 182.1 ± 2.9 mya [START_REF] Riley | U-Pb zircon (SHRIMP) ages for the Lebombo rhyolites, South Africa: refining the duration of Karoo volcanism[END_REF].

Previous excavations

Raymond Dart initiated excavations at the site in 1934. He dug a narrow trench at the entrance to the shelter (Figure 2, EXC. 1), but unfortunately never published his findings, and the material has since been misplaced. In 1940 a massive pit was dug in the centre of the cave deposit by W. E. Horton, apparently to extract bat guano. He uncovered archaeological and human remains, including an adult partial cranial vault (BC1), the shafts of two femora and tibiae that have since been lost, and a partial adult mandible (BC2) [START_REF] Cooke | Fossil man in the Lebombo Mountains, South Africa: the 'Border Cave', Ingwavuma district[END_REF][START_REF] De Villiers | Human skeletal remains from Border Cave, Ingwavuma district, KwaZulu, South Africa[END_REF][START_REF] Beaumont | Border Cave[END_REF]. A second excavation campaign was conducted by [START_REF] Cooke | Fossil man in the Lebombo Mountains, South Africa: the 'Border Cave', Ingwavuma district[END_REF]Wells in 1941 and1942 (Figure 2, EXC. 2), and led to the noteworthy discovery of an infant burial (BC3) associated with a Conus shell [START_REF] Cooke | Fossil man in the Lebombo Mountains, South Africa: the 'Border Cave', Ingwavuma district[END_REF]d'Errico and Backwell, 2016) that came from Member 1 RGBS. From 1970 to 1975 extensive excavation of the site was conducted by Peter Beaumont, who exposed a 4 m-deep sedimentary sequence of alternating brown sand (BS) and white ash (WA) deposits [START_REF] Beaumont | Border Cave[END_REF][START_REF] Butzer | Lithostratigraphy of Border cave, KwaZulu, south Africa: a middle stone age sequence beginning c. 195,000 BP[END_REF] (Figure 2, EXC 3A). The deposits contained MSA lithic assemblages that he initially ascribed to various phases of the Pietersburg Industry, and an early Later Stone Age assemblage [START_REF] Beaumont | Border Cave[END_REF]. The lithic assemblages were later attributed to MSA 1, MSA 2/HP, MSA 3/post-HP and Early Later Stone Age (ELSA) (Grün and Beaumont,2001). Human remains recovered include an Iron Age skeleton missing the skull (BC4) that was found near the surface in the southern part of the cave, which was directly dated to 340 ± 45 14 C BP (Pta-777) and 480 ± 45 14 C BP (Pta-1318) [START_REF] Beaumont | Modern man in sub-Saharan Africa prior to 49 000 years BP: a review and evaluation with particular reference to Border Cave[END_REF]Beaumont, 1980;Vogel et al., 1986). In 1974, Powell and Beaumont found a nearly complete adult mandible (BC5) while collecting sediment samples from the South section of excavation 3A. It was directly dated by electron spin resonance (ESR) to 74 ± 4 ka [START_REF] Grün | On the age of Border Cave 5 human mandible[END_REF]. A humerus (BC6), proximal ulna (BC7), and two metatarsals (BC8a and BC8b) were recovered from disturbed deposits [START_REF] Grün | Border Cave revisited: a revised ESR chronology[END_REF] but have since been lost. In 1987 Beaumont, Todd and Miller conducted another round of extensive excavations in the shelter (Figure 2, EXC. 4A and EXC. 4B). Changes were made to the stratigraphic sequence, resulting in the oldest deposits, initially called BACO A-D, being renamed Members 5 WA, 5 BS, 6 BS.UP and 6 BS.LR (Figure 2). The BACO A unit was divided into an upper part (Member 4 WA) and a lower part (Member 5 BS). The BACO B unit was renamed 5 WA, BACO C was renamed 6 BS.UP and BACO D changed to 6 BS.LR. Member 1 GBS changed to 4 BS and Member 1 BS.UP.S to 1 BS.LR A [START_REF] Beaumont | Contemplating old clues to the impact of future greenhouse climates in South Africa[END_REF].

Chronology

The MSA deposits at Border Cave have been dated by [START_REF] Grün | Border Cave revisited: a revised ESR chronology[END_REF] and [START_REF] Grün | On the age of Border Cave 5 human mandible[END_REF] using ESR on tooth enamel and with Bayesian modelling of ages conducted by [START_REF] Millard | Bayesian analysis of ESR dates, with application to Border Cave[END_REF].

New luminescence ages derived from feldspar grains in MSA sediments are reported by Tribolo et al. in this volume, who also report new Bayesian age intervals for the different stratigraphic units, and these intervals are derived from the recalculated ESR measurements published by [START_REF] Grün | On the age of Border Cave 5 human mandible[END_REF], as well as the 14 C data of d 'Errico et al. (2012a) and [START_REF] Villa | Border Cave and the beginning of the Later Stone Age in South Africa[END_REF]. In Table 1 a synthesis of the Bayesian age estimates for the members analyzed in this paper is provided. Beaumont's Masters thesis presents the most complete lithic analysis conducted for this site [START_REF] Beaumont | Border Cave[END_REF] and includes a thorough blank analysis, taking into account morphometry, technology and typology of the excavation 3A lithic assemblage. In his study, Beaumont stressed several aspects concerning the typology and technology of the post-HP/MSA 3 at Border Cave. He concluded that the MSA 3 at Border Cave was characterized by the absence of 'crescents' (sic) and a low number of points. He also distinguished an early phase (Members 2 WA and 2 BS.LR C), characterized by 'modified butts' (sic) (facetted platforms) and low values of chalcedony and scaled pieces; and a late phase (the upper part of Member 2 BS) with high values of the latter two. Another aspect stressed for this later phase is the high number of dihedral and polyhedral platforms and radial prepared cores, and very low number of points and retouched pieces (Beaumont, 1978: 103). One of the conclusions of his techno-typological study was that the assemblage of Members 2 BS and 2 WA was probably a 'terminal occurrence within the MSA' (Beaumont, 1978: 103). Although he highlighted the absence of backed pieces, he included trapeze or double truncated backed pieces in the only graphic representation that he made of the MSA 3 (Beaumont, 1978: 137, Fig. 88;Beaumont et al., 1978: 411, Fig. 4B) (Figure S1).

Regarding Member 3 BS, [START_REF] Beaumont | Border Cave[END_REF] mentioned briefly that trimmed base points are typical of Members 2 BS.LR and 2 WA but also occur occasionally in Member 3 BS. The description of the industry for Member 3 BS was presented together with lithics from Members 3 WA and 1 RGBS. He highlighted the abundance of blades (that he associated with the 'punch' technique (sic)), the presence of backed elements (some of them similar to Châtelperron and Abri Audi knives) and the occasional representation of small 'pressured flake' triangular items (Figure S1). In his thesis, he attributed these lithostratigraphic members to the 'Epi-Pietersburg' variant of the old 'Second Intermediate' [START_REF] Beaumont | Border Cave[END_REF]. However, he later attributed all of them to the HP Industry (e.g. [START_REF] Beaumont | Contemplating old clues to the impact of future greenhouse climates in South Africa[END_REF][START_REF] Grün | Border Cave revisited: a revised ESR chronology[END_REF].

Villa and colleagues (2012) also made a technological analysis of Members 2 WA and 2 BS in order to compare the lithic technology to what Beaumont and colleagues (1992) called the Early Later Stone Age (ELSA) Industry in Members 1 WA and 1 BS.LR. In that study, Member 2 WA was characterized as mainly containing blades and elongated flakes with parallel sides 'as the main objectives of the debitage' (Villa et al., 2012: 13209). Core exploitation with bidirectional removals was the main reduction sequence identified (Figure S1). Members 2 BS.LR A and B were characterized as having a decline in blade production, disappearance of unifacial points, drastic reduction in retouched pieces and an increment in bipolar knapping and the use of chalcedony and crystal quartz as raw materials.

MATERIALS AND METHODS

Sample for the technological analysis

We analysed all of the lithic material excavated from 2015 to 2018 and a sample from 2019 from Members 2 BS, 2 WA, 3 BS and 1 RGBS. Most of the material derives from the North profile left by Beaumont's 3A rear trench excavation (excavated 2015Beaumont's 3A rear trench excavation (excavated -2019)), and a small portion corresponds to the South profile of his 4A trench excavation (excavated only in 2018 and 2019) (Figure 2). In total, we analysed 6,450 lithic artefacts/pieces (Table 2). The archaeological layers studied in the lithic analysis are presented in Data S1. Figure 2 shows a general plan of the cave with the location of the areas considered in this analysis, and the distribution of point-plotted lithic artefacts from excavations conducted along the North and South profiles. To group the industries in the lithic analyses we followed the allostratigraphic units proposed by Stratford and colleagues (this volume). The allostratigraphic approach divides depositional sequences into units and packages based on the presence of sedimentary discontinuities. It provides the opportunity to identify sequences and breaks within compositionally similar sediments. The study distinguished between allostratigraphic members: gradational change, paraconformities and disconformities (Stratford et al., this volume). The allostratigraphic members included in this analysis are: 2 BS.UP, 2 BS.LR, 2 WA.UP, 2 WA.MD, 2 WA.LR, 3 BS and 1 RGBS.

Technology and particle size

Technological investigation of the sample involved an attribute analysis following previous lithic methodological studies [START_REF] Bernaldo De Quirós | Proyecto de análisis técnico para las industrias líticas[END_REF][START_REF] Pelegrin | Technologie lithique: le Châtelperronien de Roc-de-Combe (Lot) et de la Côte (Dordogne)[END_REF][START_REF] Inizan | Technology and terminology of knapped stone: followed by a multilingual vocabulary arabic, english, french, german, greek, italian, portuguese, spanish[END_REF][START_REF] Tostevin | Seeing Lithics: A Middle-Range Theory for Testing for Cultural Transmission in the Pleistocene[END_REF]de la Peña, 2015b) which has been adapted for this collection. Our analysis applied the chaîne opératoire concept [START_REF] Karlin | Processus techniques et chaînes opératoires: Comment les préhistoriens s' approprient un concept élaboré par les ethnologues[END_REF], however, we tried to control the subjectivity of this approach through univariate and multivariate statistical analyses, as proposed elsewhere (e.g. de la Peña, 2015b). These included normality tests (Shapiro-Wilk), t-tests, and Mann-Whitney U tests, which were applied to the typometrical attributes, and chi-squared/contingency tables, correspondence analysis, and non-metric multidimensional scaling in order to explore significant relationships between the different attributes. In many instances, there were zero inflated values in the different attributes studied, so non-metric multidimensional scaling was applied to complement the traditional correspondence analysis as we considered it to be more suitable for these data.

As most of the reduction varieties in this assemblage can be referred to as centripetal 'core-prepared' strategies, we have followed the work of [START_REF] Boëda | Identification de chaînes opératoires lithiques du Paléolithique ancien et moyen[END_REF], [START_REF] Boëda | Le débitage discoïde et le débitage Levallois récurrent centripède[END_REF] and [START_REF] Meignen | The Mousterian lithic assemblages from Kebara cave[END_REF].

Regarding core reduction strategies, we also grouped the different varieties into the core classification system of [START_REF] Conard | A unified lithic taxonomy based on patterns of core reduction[END_REF], as it has been used in several recent technological analyses of the South African MSA (e.g., [START_REF] Conard | What is in a name? Characterising the 'post-Howiesons Poort' at Sibudu[END_REF][START_REF] Douze | Techno-cultural characterization of the MIS 5 (c. 105-90 Ka) lithic industries at Blombos Cave, Southern Cape, South Africa[END_REF]. Regarding the core categories, we have added the categories 'core on flake' (explained more extensively for MSA contexts in de la Peña and Wadley, 2014a) and 'bipolar', meaning knapping on anvil cores (as defined in de la Peña, 2011).

There are other pieces generated through knapping reduction that denote different technological choices that can occur during the knapping process, such as trimming gestures, preparation in order to initiate a specific type of blank such as blades, removal of knapping accidents (hinge/step scars), change of direction, etc. These pieces can offer key information for understanding the reduction process. We have named these pieces 'core-related by-products' as in previous analyses (see de la Peña and Wadley, 2014a).

All the blanks that could provide technological or archaeological information were included in an exhaustive attribute analysis. Our technological analysis involved recording both typo-metrical and technological attributes which, indirectly, inform us about the knapping techniques and knapping methods used (as in [START_REF] Inizan | Technology and terminology of knapped stone: followed by a multilingual vocabulary arabic, english, french, german, greek, italian, portuguese, spanish[END_REF][START_REF] Pelegrin | Les techniques de débitage laminaire au Tardiglaciaire: critères de diagnose et quelques réflexions[END_REF]. The variables considered were raw material type, fragment (Yes/No), presence of cortex (following Tostevin, 2012), maximum length, maximum breadth, maximum thickness (all these measurements with the artefact technologically oriented and measured with plastic callipers so as not to damage the tool), weight, type of platform, platform length, platform width, external platform angle (measured with a plastic goniometer), number of dorsal scars, cross section, dorsal scar pattern (Figure S2), blank curvature, knapping accidents, heating attributes and residues (for a more detailed description, see List S1). As a novelty, we also incorporated the attribute 'ridges and nodes', which consisted of counting the points of intersection of dorsal flake negatives or, instead, if there were no intersections between flake scars, the number of ridges (Figure S3). This variable was designed to explore intensity of recurrence in the knapping process. The raw material classification of the attribute analysis considered the specific varieties of rhyolites and basalts in our sample, and a refined classification considering grain size, colour and crystal inclusions was made (see Data S2 for a description of this classification).

All the variables and attributes cover the general typometry of the pieces (length, breadth, thickness and weight of all the blanks), the technique used (platform type, size of the platform and external platform angle), the morphology of the blanks, and therefore related knapping method (shape of the blank, number of scars, dorsal scar pattern, cross-section, curvature), the presence of knapping accidents, and finally attributes on the recurrence of the knapping reflected on the dorsal scar pattern of the flakes (ridges and nodes). The occurrence of these attributes was explored throughout the members.

All the flake fragments and chips that could only offer limited information were classified according to raw material (xenomorphic quartz (X-quartz), automorphic quartz (A-quartz), opaline/agate or rhyolite/basalt (R/B)), weighed, and counted by size class (<2 cm, 2-4 cm, >4 cm). A more general classification for the raw materials was performed for these pieces, as particularly the smaller chips and fragments (<2 cm) were impossible to assign to a specific raw material.

We also tracked heating attributes in all of the lithic assemblage (complete flakes, fragments and chips), in order to see if there were areas, layers or groups of layers particularly disturbed by postdepositional and/or intentional heating. The attributes considered were the ones defined in [START_REF] Wadley | Responses of South African agate and chalcedony when heated experimentally, and the broader implications for heated archaeological minerals[END_REF], notably: rough surface, potlids, white or reddish colour (white for agates, and reddish/orangish colour for chalcedonies), presence of two types of gloss on different scar removals.

We identified as residue any macroscopic particle attached to the lithic and identifiable to the naked eye.

For the statistical analyses we used PAST software (Hamer et al., 2001).

All microscopic observations were made with a Leica Zoom microscope. Photographs were taken with a Canon MD500 digital camera with a 1.8F lens in the Archaeology Laboratory at the Evolutionary Studies Institute, University of the Witwatersrand.

Sample for the spatial analysis

For the distribution study, a total of 955 piece-plotted lithics with three spatial coordinates (X, Y, Z)

were used. We analysed the plotted material from Members 2 BS, 2 WA and 3 BS from the North profile of excavation 3A rear in squares X117, 118, 119 and 120, and Y 109. There is an unexcavated section of deposit in X118.5-119, thus, for the vertical projection analysis (XZ) the area studied was divided into two groups: E and W, to avoid the void generated by the absence of data in this area (Figure 2).

Spatial analysis

With the aim of exploring spatial distribution, occupation intensity and potential areas of postdepositional alteration, a combination of spatial techniques were employed, namely Geographic Information Systems (GIS) and inferential statistics (density analysis and hot spot analysis). The spatial distribution analysis (SDA) mainly focused on analysing whether the lithic artefacts were clustered, dispersed or randomly distributed. It also provided the statistical significance of clusters according to their spatial location, and data on the variables that define the groups. In this work, we applied the Getis-Ord Gi* and Anselin Local Moran's I methodologies to analyse the spatial patterns [START_REF] Anselin | Spatial statistical analysis and geographic information systems[END_REF][START_REF] Mckillup | Geostatistics Explained: An Introductory Guide for Earth Scientists[END_REF][START_REF] Mora Torcal | Inside the palimpsest: identifying short occupations in the 497D Level of Cova Gran (Iberia)[END_REF].

We also performed a spatial density analysis. Kernel density analysis permits calculating the zones with high or low concentrations of artefacts, according to the location and spatial proximity of features under study.

The SDA was conducted in two geometric planes corresponding to the projection of the assemblage on the XY and XZ axes. The SDA on the XZ plane is related to the stratigraphic position and both projections (XY and XZ) explored preferential distribution areas.

In the XZ plane an analysis grid of hexagonal cells was created (6 cm size), whereas in the XY the grid was composed of squares. The hexagon's size does not offer a preferential orientation. The 6 cm size was specifically chosen because of the size of the artefacts, as the majority of them fall under this cutoff size.

The statistical methods were implemented using QSIG software (version 3.16.16-Hannover) and, specifically, with the Hot spot Analysis plugin (version 2.0.0).

RESULTS

Results of the technological analysis

General counts

The attribute analysis and the fragments and chips classification table are provided in Data S3, S4, S5 and S6. A summary of the total count, weight, densities (count/volume and weight/volume) and number of cores and retouched pieces is presented in Table 2. The lowest densities (count/volume and weight/volume) are in Member 3 BS, whereas 2 WA has the highest densities. Most of the lithic remains are flakes, fragments and chips, and there is a low percentage of cores and retouched pieces.

Thus, most of our conclusions derive from the debitage and chips (attributes and frequencies).

Raw materials

From the counts of the classification of flake fragments and chips (2 cm, 2-4 cm and >4 cm) according to raw material, the category R/B (which included rhyolite and basalt) is dominant in all of the members (Figure 3A,B). The main aspects to highlight are how chalcedonies and agates are relevant at the beginning and at the end of the series, that A-quartz appears in Member 2 BS.UP, and that Xquartz occurs in 3 BS and 1 RGBS.

For the pieces that could offer more technological information, we analysed the raw materials in more depth. This classification paid attention to the macroscopic differences between rhyolites, looking at colour, texture, and crystal inclusions (see Data S2 and Figure 3C,D). This assemblage also showed the predominance of the different varieties of igneous rocks (mainly rhyolites) and the presence of other raw materials such as hornfels, quartzite and chert (Figure 3D), with an amethyst chip in 2 WA.UP. This more refined classification shows how 2 WA.MD and LR have MP2 (reddish-orange, fine grain, with crystal inclusions and veins) as the most abundant rhyolite variety, and that they are quite distinct from 2 WA.UP. The three upper allostratigraphic members and sub-member units show the highest variability in the number of raw materials. The chi-squared test of all allostratigraphic members and sub-member units shows that there are significant differences in the distribution of raw materials by member and sub-member unit, p (no assoc.): 5.38E-16. When the relationships are explored by pairs of members and sub-member units that are in stratigraphic contact (Table 3), it

shows that 2 BS.LR and 2 WA.UP, and 2 WA.UP and 2 WA.MD show statistically significant differences, whereas the two 2 BS sub-member units and all the lower allostratigraphic members and sub-member units (from 2 WA.MD to 1 RGBS) cannot be distinguished in this regard. The correspondence analysis groups the allostratigraphic members and sub-member units as follows: a first group with the two allostratigraphic members of 2 BS, another group 2 WA.UP, and then 2 WA.MD, 2 WA.LR, 3 BS and 1 RGBS (Figure 3F, Table S1). The non-metric dimensional analysis (Figure 3G) also separates 2 BS.UP from 2 BS.LR. In all the stratigraphic units the percentage of pieces with no cortex is more than 50% of the sample studied (Figure 3E). There is a trend from 1 RGBS to the upper part of the sequence towards a decrease in cortex percentage.

Cores and core-related by-products

A synthesis of the main types of cores found in the sample is presented in Table 4, and in Data S7 a more detailed description of all the attributes of these cores (typometry and qualitative attributes) is given.

There are some interesting aspects to the core assemblage even though the sample size from the new collection is small and the data are thus not statistically significant.

-The most abundant types of cores are parallel and inclined varieties (Figures 4 and5).

-The parallel variant represented is Levallois recurrent centripetal (as defined by [START_REF] Boëda | Le débitage discoïde et le débitage Levallois récurrent centripède[END_REF] and it occurs in Members 3 BS, 2 WA.UP and 2 BS.LR (Figure 4). These cores show angles between the striking platform and knapping surface ranging from 30 to 60 degrees. In all the cases, the cores appear knapped until exhaustion. In other words, additional preparation and exploitation would have been difficult due to their small size.

All photographs: P. de la Peña

Regarding the core-related by-products, we found 16 of these pieces. These elements point out several technological aspects related to core reduction (Table 4). The most relevant qualitative conclusions deduced from these few pieces are:

-The presence of platform cores for bladelets with two opposed platforms in Members 2 BS.UP and 2 BS.LR (Figure 6A,B).

-The presence of another variant of Levallois core in 2 WA.LR and 3 BS with two opposed platforms.

As can be seen in Figure 6C -The occasional initiation or re-arrangement of blade cores through semicrests in Members 2 WA.LR and 3 BS (Figure 6E, F). The example of BC 3752 from Member 2 WA.LR shows a semicrest produced on a cortical surface, and it was probably at the initial phases of exploitation of the core to produce blades, whereas with the other example it is impossible to tell if it was a maintenance activity to reshape the core volume in order to continue producing blades, or if it is a residual set of removals from the initiation of the core (BC 5553 from Member 2 WA.LR). In the assemblage, there are other types of blanks among the debitage that are indicative of specific modalities of knapping methods. In this regard, among our sample there are 'chordal flakes'. These blanks were defined by [START_REF] Boëda | Le débitage discoïde et le débitage Levallois récurrent centripède[END_REF], and they are characterized by a knapping reduction along the chordal orientation of the core. As a result, the technological axis is oblique to the morphological axis of the piece. There are two types of chordal flakes: 'the ones that have a distal point created by the intersection of two either unilineal or crossed removals opposite the 'back' (core edge), referred to as a "pseudo-Levallois point" by Bordes (1961), while the other type (also called éclat débordant) has a lateral back oriented along the technological axis of the flake that is opposite one or two edges (Faivre et al., 2017: 118). These technological pieces can be produced in Levallois and discoid reductions and they appear in our sample. In particular, there are éclat débordants taking a small portion of the core edge and pseudo-Levallois points with triangular shapes (Figure 7, Figure S4 and Table 4). Moreover, there are a number of these blanks that have triangular shapes, and they fall into the category that

Scales = 1 cm. All photographs: P. de la Peña

There are also flakes and blades that could fall within what has been defined as Levallois flakes and blades. In Table 4 we present these items by allostratigraphic member. A qualitative distinction between the Levallois flakes stands out; on the one hand, there are flakes in Members 2 WA.UP and 2 BS.LR that are characterized by thick platforms (Figure 8A, B, C), probably due to hard mineral percussion [START_REF] Pelegrin | Les techniques de débitage laminaire au Tardiglaciaire: critères de diagnose et quelques réflexions[END_REF]. On the other hand, in Members 2 WA.LR and 3BS there are Levallois blades with bidirectional scar patterns, rectilinear in profile, and with an acute angle between the striking platform and the knapping surface that is probably related to core-related by-products (Figure 8D,E,F). In the Levallois blades there are small removals on the dorsal face close to the platform, and a smooth surface, probably due to passing the hammer over that specific spot, what [START_REF] Pelegrin | Technologie lithique: le Châtelperronien de Roc-de-Combe (Lot) et de la Côte (Dordogne)[END_REF] defines as 'abrasion' (Figure S3). A comparison of the length/breadth ratio of these two 'types' of

Levallois blanks shows how they appear to be different. The ones coming from 2 BS.LR are wide and thick, whereas the ones from 2 WA.LR and 3 BS are more elongated (Figure 8G). A Mann-Whitney U test of the length/breadth ratio showed that they are statistically different p.same:0.00041 (Table S2 andS3). There is a small proportion of these two variants of Levallois flakes that also have triangular shapes (Figure 7), see Timbrell and colleagues (this volume). There are also a number of flakes in the assemblage that fall under the definition of typical and atypical Levallois points (Figure 7). These blanks are studied in depth by Timbrell et al. (this volume). These types of blanks have a triangular shape and unidirectional convergent scar patterns. They might come from Levallois and discoid reductions or, possibly, a specific unipolar convergent Levallois variant, though we have not found any other qualitative clues (such as cores or core-related by-products) to support the presence of this knapping modality. Thus, it seems likely that they were produced through discoidal and Levallois reduction sequences.

Typometry and attribute analysis of flakes

Regarding the typometrical measure of the blanks (length, breadth, thickness, and weight) in our assemblage there were several members that were statistically not normal after the Shapiro Wilk test (Figure S5 and Table S4, 5, 6). Therefore, in order to compare these variables between the different members, we used the non-parametric Kruskal Wallis test. For the length there are significant differences between members (p (same)=0.00008249) and the Mann-Whitney results show that there are statistical differences between all of the contiguous stratigraphic members, except for the lowermost ones from 1 RGBS to 2 WA.MD (Table 5). For the breadth, the Kruskal-Wallis test did not find significance differences between sample medians. Finally, for the thickness, there was a significant distinction between the medians, and in this case all the members are different from 1 RGBS except 2 BS.LR (see Tables S7,8, 9, 10). WA.LR. The Kruskal-Wallis test showed significant differences between the sample medians for breadth and length of the platform values. The Mann-Whitney U test results showed differences between most of the members, although Members 3 BS and 2 WA.LR showed no significant differences in these typometrical attributes (Tables S12 to S15).

For the rest of the qualitative attributes (ridges and nodes, number of scars, dorsal scar pattern, shape of the blanks, profile curvature, sections) chi-squared and Monte Carlo tests (more suitable for smaller samples) of each attribute studied do not show significant differences between the members (Table 7). Nonetheless, there are some aspects worth mentioning regarding the frequencies of the different attributes, which could indicate some differences between the allostratigraphic members and submember units (Figure S6). The intensity of the knapping (recurrence) seems higher in 2 WA.MD (see number of scars and ridges and nodes) for the assemblage studied. The dorsal scar pattern in the lower units (3 BS, 2 WA.LR, 2 WA.MD) show how bidirectional and unidirectional convergent patterns are more abundant in the lower units, whereas in the upper units multidirectional patterns are in the majority (2 WA.UP, 2 BS.LR and 2 BS.UP ). This is in accordance with the presence of two opposed platforms core-related by-products in the lower members and the Levallois recurrent centripetal in 2 WA.UP and 2 BS.LR (vide supra). Members 1 RGBS and 3 BS have the highest proportion of straight and medium profile blanks. The percentage of retouched pieces in all of the members (except 1 RGBS) does not pass 1% of the sample analysed in the attribute analysis (Table 1). Most of the retouched pieces were documented in unit 2 BS.LR. The main categories by order of representation are retouched points (see Timbrell et al., this volume), retouched flakes (pieces with simple retouch somewhere on the dorsal or ventral face), backed pieces, notches and denticulates (Table 4 and the attribute analysis of all these blanks in Data S8). There are also pieces that present macroscopic scars, and these might be due to use, hafting amendments, or trampling. In-depth use-wear analysis will be necessary to assess the causes of these scars.

The retouched points/triangular elements include 10 complete pieces and one fragment. There are several aspects worth noting in this small sample of retouched points (the morphometry and technology of these pieces are presented in Timbrell and colleagues (this volume)). Firstly, the two fossiles directeurs that [START_REF] Beaumont | Border Cave[END_REF] highlighted -Châtelperron/Abri Audi knives and trimmed points -are present in our sample. In Very Dark Brown Ea (Member 3 BS), BC3224 fits the description by Beaumont of 'Châtelperronian' points, with abrupt direct retouch to the lateral left (unique in this sample) and a plain platform (Figure 9F). There is also a refit of BC5050 and BC4710 (Figure 9A), which is a good example of the 'trimmed points' that Beaumont observed at the bottom of Member 2 WA, with the base being shaped through an inverse simple retouch. BC4728 (Figure 9D) from Dark Yellowish Brown Dino shows a similar 'template', as the retouch is identical to the base of the refitted pieces. In unit 2 BS.LR, there are three retouched points in which the platform has been removed (see BC543, BC5209, BC1222 in Timbrell et al., this volume). This could be to facilitate hafting.

Besides the 'Châtelperronian'-like point there are two other pieces with abrupt retouch (close to 90 degrees) that could be classified as quite irregular backed pieces (segments) (Figure 9E).

Regarding the 'retouched flakes', which is the next largest category after the 'points', all of them present simple retouch (around 45 degrees), and the retouch does not usually cover a complete edge.

Some of them have this retouch on the proximal lateral areas of the flake and it could be related to hafting (Figure 9C). Finally, there is a notched piece and a fragmented denticulate in 2 BS.LR (Figure 9G andH). The frequency of retouched pieces per layer is not statistically significant, but the frequency of their type of raw material (Figure S7) is (p (no assoc.): 0.000529). When the chi-squared test is run on contiguous pairs of units, 2 WA.UP and 2 BS.LR show statistically significant differences (Table 8). As a last step in our technological analysis we made a correspondence analysis of all the technological qualitative attributes of the blanks, the raw material distributions (of the attribute analysis) and the retouched pieces. The first axis explains around 59% of the variance. The first axis clearly separates all the units below 2 WA.MD from the ones in the upper half. From this analysis we can tentatively propose four groups based on their proximity: 1 RGBS-3 BS, 2 WA.LR-2 WA.MD, 2 WA.UP, and 2 BS.LR-2 BS.UP (Figure 10A).

The non-metric dimensional analysis of the same attributes gives a slightly different picture, grouping all the lower units (from 1 RGBS to 2 WA.MD) and separating from each other 2 WA.UP, 2 BS.LR and 2 BS.UP (Figure 10B).

Finally, the classical cluster of all these attributes shows how 2 BS.LR separates from all the rest of the units, and groups 2 WA.UP and 2 BS.UP, and then all the lower units from 3 BS to 2 WA.MD. In this last group of the lower members, three sub-groups are distinguished: 1 RGBS, 3 BS and 2 WA.LR, and 2 WA.MD (Figure 10C).

Figure 10. Correspondence analysis (A), non-metric dimensional analysis (B) and classical clustered analysis (C).

The main results of the technology analysis are summarized as follows: lithics from units 2 WA.UP, 2 BS.LR and 2 BS.UP are characterized by discoidal and Levallois reduction, and an abundance of unretouched triangular blanks. However, the three of them have notable differences regarding raw material percentages and frequencies of technical features, and in the multivariate statistical analysis they were clearly separated from each other. Units 2 WA.MD and 2 WA.LR have a much lower percentage of chordal flakes (typical of discoidal reduction) in comparison with the upper lithic assemblages, and instead a specific variant of Levallois reduction towards the production of elongated blanks with two opposed platforms was documented, deduced from core-related by-products. These two sub-member units also have triangular blanks, but they are different from the triangular blanks in Member 2 BS with regard to dorsal scar pattern and elongation. Indeed, the highest elongation index between units 1 RGBS and 2 BS.UP was recorded in unit 2 WA.LR (showing no statistical difference from 3 BS). Unit 2 WA.LR also has crested blades, which are typical of initiation of the cores in some blade reduction knapping methods. In Member 3 BS discoidal and Levallois recurrent reduction methods were also documented on two cores. Member 1 RGBS did not provide any cores (except two tested nodules), but the attribute analysis of the flakes demonstrated continuities with Member 3 BS.

Regarding raw material distribution, different varieties of rhyolite were dominant in all four members.

Finally, the number of cores and core-related by-products is very low. This fact, together with the very low percentage of cortex recorded in all the members, might reflect that relatively little knapping activity took place in this part of the shelter. There are also very few retouched pieces, although together with blanks with macroscars they constitute an important group of our sample given the small area excavated. Some of the morphotypes coincide with previous analysis conducted by [START_REF] Beaumont | Border Cave[END_REF]. The most represented groups are retouched flakes and triangular blanks with some retouch.

Preliminary particle size analysis

As already mentioned, the member with the greatest lithic density is 2 WA (Table 2). However, if we observe the particle size distribution per sub-member unit, there are sometimes remarkable differences between contiguous layers, with some of them having an abundance of chips and bigger flakes, while the immediately adjacent layer show comparatively very low values (Figure 11A).

The particle size analysis by size groups (<2 cm, 2-4 cm, >4 cm) follows a similar particle size pattern of other knapped experimental and archaeological assemblages, with the number of particles decreasing rapidly as the size of particles increases [START_REF] Schick | Stone Age Sites in the Making[END_REF][START_REF] Bertran | Particle size distribution of lithic assemblages and taphonomy of Palaeolithic sites[END_REF]Thomas et al., 2019). This is the case for all the units considered, as shown in the stacked chart (Figure 11B). However, the chi-squared test of the particle size frequencies by groups compared to contiguous members and sub-member units shows, on the one hand, significant differences between all the units from 2 WA.MD to 2 BS.UP and, on the other hand, a similarity in distribution from 3 BS to 2 WA.MD. This could be due to cultural behaviour (frequency of occupation and intensity) or taphonomic factors (Table 9).

The particle size distribution of rhyolite/basalt (R/B) as shown in the ternary plot highlights an interesting aspect. For the R/B (Figure SX) it shows how units 3 BS to 2 WA.MD have a similar pattern distribution with the greatest abundance of small particles. It also groups 2 WA.UP and 2 BS.UP.

Finally, 1 RGBS and 2 BS.LR both have distributions distinct from all of the other members and submember units (Figure 11C). In chalcedonies/agates, the distribution is different, with units 3 BS and 2

WA.LR forming one group and units 2 WA.MD, 2 WA.UP and 2 BS.UP forming a second group, and with units 1 RGBS and 2 BS.LR in between these two groups. The distribution of residues and heating attributes is inversely proportional for units 3 BS, 2 WA.LR and 2 BS.UP (Figure 11D), but not for the rest of the members, which is surprising as one would expect these two qualitative attributes to be inversely proportional to each other.

We also explored the relationship between lithic heating attributes, lithics with residues, poor bone preservation, and bone heating attributes (the latter two features provided by JLC in Stratford et al.

(this volume)) for Member 2 WA (Table 10). This was an exploratory exercise in order to look for potential meaningful relationships between different types of items, similar to the one presented in [START_REF] Rodríguez-Rellán | The exploitation of local lithic resources during the Late Prehistory of Northwest Iberian Peninsula[END_REF]. The Spearman's rank comparison (Figure 11E) shows how lithics with heating attributes have a positive correlation with bones with some degree of burning. This seems logical, although it must be highlighted that this correlation is not very high. However, the lithics with heating attributes have an inverse correlation with bone with poor surface preservation, which again was unexpected. Moreover, the lithics with heating attributes also have a positive correlation with pieces with macroscopic residues. Burnt bone has a positive correlation with poor surface preservation, which was expected, and has an even higher correlation with lithics with residues. These results could be indicating either that there were different sets of activities within the units evaluated here and that lithics and bones are reflecting different sets of activities in some instances, or that the units of analysis are not sensitive enough to assess this. We are aware that these comparisons are inappropriate in data with significant sampling differences. However, as the assemblage is relatively small and the surface excavated too we present this preliminary data as a mere exploratory exercise.

Spatial analysis

XZ (vertical view)

The two spatial distribution analyses (Getis-Ord Gi* and Moran I test) and the kernel density analysis (Figure 12 A, B, Figure S8) show similar results regarding the areas of low and high concentration of artefacts (and their corresponding significant values). The spatial distribution analysis shows several distinct areas of significant concentrations. Moreover, the distribution of the densities shows a similar direction regarding slope of the layers excavated within the members, although there are two areas where this does not apply (vide infra). Member 3 BS shows spatial distribution coherence in the sense that there are not significant spatial distinctions (Figure 12B). This might be due to a low number of artefacts (> 2 cm) in comparison with the upper units (in X118 there is a cold spot).

The artefacts in Member 2 WA do not show a uniform distribution and there are several spatial differences to highlight. There is a significant concentration in the eastern uppermost part (X118)

where there are probably several occupation events, which show continuity with the lowermost limit of Member 2 BS.LR. Considering only the distribution of the artefacts, Member 2 WA could be tentatively divided in two vertical zones, an upper and a lower one. The upper zone shows several events and higher rates of concentration, whereas the lower zone shows a remarkable continuity with Member 3 BS, displaying no significant distribution pattern, with the exception of a concentration spot at the contact between X 117 and X118, and a negative one a few centimetres towards the East.

Member 2 BS also shows several spatial differences. The first one is the significant hot spot at the base of the member, coinciding with the lowest part of Member 2 BS.LR. This concentration seems to be a continuation of the top of Member 2 WA.UP. It is not entirely continuous in square X119. It is interesting to note that just above this high concentration in X118 a negative correlation (meaning a low density of artifacts) is highlighted, which indicates different occupation events within this submember (2 BS.LR).

In the upper part of Member 2 BS (coinciding with the stratigraphic distinction of 2 BS.UP) there is no significant relationship between artefacts. However, there is a vertical dispersion hot spot at the contact between X119 and X120, linking sub-member units 2 BS.UP and 2 BS.LR. in that specific area.

This spot, together with the negative correlation (meaning a low density of artifacts) in Member 3 BS is the only area with a vertical dispersion in this spatial analysis. Although the hot spot between 2 BS.LR and 2 WA.UP in X117-118 has a notable vertical distribution, particularly in the area to the West (Figure 12B).

XY (Plan view)

In order to explore the lithic spatial associations in the hot spot between the top of units 2 WA.UP and the base of unit 2 BS.LR, an exploration of the XY projection of different stratigraphic layers distinguished during excavation in this area of lithic concentration was made. In this regard, three different layers were selected for their close proximity to each other (together measuring less than 15 cm in depth) and their designation to different members: layer Grass Mat 1 in unit 2 BS.LR and layers 'Very Dark Greyish Brown' and 'Light Reddish Brown' in unit 2 WA.UP. The Getis-Ord Gi* method shows how these three layers display significantly different areas of distribution between the three of them (Figure 12C). This exploratory analysis demonstrates that the large concentration of lithic artefacts at the top of unit 2 WA.UP and the base of 2 BS.LR is not homogeneous in plan view.

Distribution of technologically and taphonomically significant pieces

In this section we explore the association between hot spots and technological (chordal and Levallois flakes) and 'taphonomic' pieces (burnt lithics and lithics with macroscopic residues).

The cores do not show any association with the hot spots in the vertical distribution. Levallois flakes appear in the lowermost part of unit 2 BS.LR where there is a high concentration with significant spatial correlation, as well as in the lower part of unit 2 WA.UP, where there is no hot spot.

The chordal flakes fit quite well in those places with the hot spots (Figure S9). Only those that are located at X117 remain rather isolated. Again, the basal part of 2 BS.LR concentrates most of these pieces and reflects a spatial and qualitative difference with respect to the top of 2 WA.UP, which is part of this hot spot but does not have these pieces. The distribution of the triangular blanks or points is similar to that of the Levallois flakes. These artefacts overlap with the high concentration of pieces in the lowermost part of unit 2 BS.LR and with the lower part of unit 2 WA (Figures 12 andS8).

The analysis of pieces with evidence of residues highlights the marginal relationship that exists between them and the areas of intense concentration (Figure S10). These pieces are quite scattered within the series. The pieces at the far end to the West in X117 are striking because it is an area with an already low concentration. The only exception to this is the lowermost part of Member 2 BS.LR.

Finally, the pieces with potlids show a wide distribution throughout the record, but they fit well with the areas of highest concentration of elements (Figure S10). Again, Members 2 WA and 2 BS.LR evidence the greatest number of them, although in 2 WA there is a concentration of them that does not overlap.

DISCUSSION

As stated in the introduction, we consider lithics (encompassing characterization, frequency, size, distribution, raw material, etc.) as potential means by which to glean information (sometimes merely clues) on site formation processes, spatial distribution, and cultural behaviour. In this discussion, we synthesize the evidence offered by the lithics with regard to these three matters and compare our findings with the archaeological record of the MSA of southern Africa for MIS 4 and MIS 3 (see [START_REF] Wurz | Technological trends in the Middle Stone Age of South Africa between MIS 7 and MIS 3[END_REF][START_REF] Wadley | Those marvellous millennia: the Middle Stone Age of southern Africa[END_REF] for some of the most recent syntheses).

The preliminary observation of the density of lithics per layer was that they were seemingly low (in general for all of the layers) in comparison to other archaeological sequences, such as Sibhudu (see for example the HP data provided in de la Peña, 2015b-SM1). At Border Cave, in most of the layers the number of pieces over 2 cm is less than 10, and the median number of pieces per layer between 2-4 cm is five. Stratford et al. (this volume) report that the density of faunal remains in the assemblage is ~5.21 kg/m 3 . This number is significantly lower than that recorded at other Late Pleistocene sites in southern Africa, such as the Still Bay deposits at Blombos, which record 15-34 kg/m 3 [START_REF] Reynard | Using trampling modification to infer occupational intensity during the Still Bay at Blombos Cave, southern Cape, South Africa[END_REF], and the HP and Still Bay deposits at Sibhudu, where faunal density is 60 kg/m 3 [START_REF] Clark | The Howieson's Poort fauna from Sibudu Cave: documenting continuity and change within Middle Stone Age Industries[END_REF][START_REF] Clark | The Still Bay and pre-Still Bay fauna from Sibudu Cave: taphonomic and taxonomic analysis of the macromammal remains from the Wadley excavations[END_REF]. Thus, the low density of lithics in the assemblage studied here is in accordance with the similarly low density of faunal remains, indicating that visits to the shelter were relatively short and/or were made by smaller groups of people. Comparing the lithic count per member and sub-member unit with stratigraphic layers from other assemblages with a similar chronology would be inappropriate, as we would be comparing different units of analysis. In this study the lithics were grouped according to allostratigraphic units as defined by Stratford et al. (this volume). In other MSA lithic analyses, the densities were assessed per layer (see for example [START_REF] Shipton | The Middle to Later Stone Age transition at Panga ya Saidi, in the tropical coastal forest of eastern Africa[END_REF]. Moreover, we know that geogenic factors played a significant role in site formation at Border Cave, and that the geogenic sedimentation rate varied, so volume of sediment is not a constant that can be used to gauge occupation intensity.

The particle size analysis by size groups (<2 cm, 2-4 cm, >4 cm) follows a similar particle size pattern as knapped experimental and other archaeological assemblages, with the number of particles decreasing rapidly as the size of particles increases [START_REF] Schick | Stone Age Sites in the Making[END_REF][START_REF] Bertran | Particle size distribution of lithic assemblages and taphonomy of Palaeolithic sites[END_REF]Bertran et al., , 2018)). However, some differences between sub-member units can be highlighted within our assemblage. The rhyolites and basalts from the lowermost units (1 RGBS to 2 WA.MD) have a similar distribution of particles, whereas from 2 WA.MD upwards the distributions are dissimilar. A comparable pattern was found for the chalcedonies/agates. The reasons for this similarity in the lowermost members could be several;

(1) they result from similar depositional and post-depositional processes (Stratford et al., this volume document mixing in the base of 2 WA, 3 BS and 1 RGBS), or (2) similar number of knapping reduction sequences and/or activities performed in the past in these groups of layers.

The data show that not all the variables are related as one would expect, for example an unexpected correlation was observed between burnt lithics and residues. Conversely, lithics with heating attributes and poor bone preservation in the 2 WA sub-member units are not directly correlated in the Spearman's rank correlation using the faunal data of Stratford et al. (this volume) and the lithic data provided in this analysis. This could be due to different sets of activities in relation to bones and lithics in the same allostratigraphic unit, or to the fact that the selected sub-member divisions do not provide enough resolution to assess these taphonomic questions. Moreover, this could also be due to taphonomic processes in parts of Member 2 WA that are masking correlations (e.g. [START_REF] Aldeias | Evidence for Neandertal use of fire at Roc de Marsal (France)[END_REF].

The spatial distribution of the piece plotted material (artefact distribution of pieces larger than 2 cm) has shown the complexity of this archaeological deposit, and different areas of high significance in spatial relationships (higher densities). There are several noteworthy aspects concerning this line of analysis. In particular, the hot spot at the bottom of Member 2 BS and the top of 2 WA indicates a concentration of activities involving pieces larger than 2 cm. It is worth noting that the distribution of these lithics in plan view (XY), comparing different layers within this hot spot, changes from one layer to another (it is not uniform in plan view), which perhaps implies that different activities were conducted at the site, probably at different moments in time. Stratford et al. (this volume) in their facies analyses described the upper part of 2 WA as 'ashy packets' corresponding to intense anthropogenic activity. However, the absence of structure in that part of the sequence suggested that it was formed through the redistribution of combustion feature bases and ashes through rake-out or dumping, with potentially a later hearth being constructed over the mass of the unit. Unit 2 WA.UP is truncated by a succession of grass mats that overlay the ashy packets (the base of 2 BS.LR). It is interesting to note that the technological analyses have shown different strategies regarding raw material selection and flaking systems for 2 WA.UP and 2 BS.LR. Thus, the base of 2 BS and the top of 2 WA imply a period of intense human occupation, including the construction of hearths and bedding, but the lithic analysis denotes different technological activities related to the two stratigraphic units and associated formation histories. The hot spot in 2 WA. UP extends to 2 WA.MD, which also comprises two laterally extensive combustion features that have been deformed, fragmented, and significantly altered by overlying grass mats (Stratford et al., this volume). From 2 WA.MD to 3 BS the spatial distribution analyses show no significant relationships, and this is potentially in accordance with the post-depositional mixing described for 3 BS, which resulted in the homogenisation of most of the sediments until 1 RGBS (in some parts of the north profile more evident than others) (Stratford et al., this volume). However, the paraconformity described in Stratford et al. (this volume) between 3 BS and 2 WA.LR was not picked up by the different spatial distribution analyses. Members 1 RGBS and 3 BS are described as being mixed (Stratford et al., this volume) and this finding is supported by the similar particle size distribution of lithics in these units, as well as in sub-member 2 WA.LR (for rhyolite/basalts and chalcedonies/agates).

Other MSA assemblages in southern Africa have also shown spatial complexity and the mixing caused by clearly anthropic episodes and other post-depositional processes that have disturbed or attenuated the archaeological signals. Perhaps the best example is Sibhudu Cave [START_REF] Goldberg | Bedding, hearths, and site maintenance in the Middle Stone Age of Sibhudu Cave, KwaZulu-Natal, South Africa[END_REF], where, in the post-HP deposits, several layers have been recognised, whereas for the HP fewer archaeological layers are distinguished. Similar examples come from Bushman Rock Shelter, where several layers and 'features' were distinguished in the 28 unit [START_REF] Porraz | Bushman Rock Shelter (Limpopo, South Africa): a perspective from the edge of the Highveld[END_REF], and the MIS 4 deposits at Pinnacle

Point 5-6, which exhibit a palimpsest of anthropic occupations [START_REF] Karkanas | Interpreting human behavior from depositional rates and combustion features through the study of sedimentary microfacies at site Pinnacle Point 5-6, South Africa[END_REF].

Lithics and cultural behaviour

The in-depth technological analysis has shown different technological trends from 1 RGBS to 2 BS.UP.

Moreover, following the allostratigraphic divisions identified by Stratford et al. (this volume), variability within Brown Sand and White Ash members has been documented in terms of the lithics (in raw materials and flaking systems). This is apparent in the differences in raw material and flake attributes recorded in 2 BS.UP and 2 BS.LR, and in the distinction between 2 WA.UP and the underlying 2 WA.MD and LR units.

Raw material comparisons and implications

Following the chaîne opératoire approach (from raw material procurement to the finished tools), the raw material selection data have pointed out statistically significant changes. The most abundant rocks knapped at the site were rhyolites, however, within rhyolites there were specific varieties that were preferred at different times (Figure 3). In addition, at the beginning and at the end of the series (2 BS.UP and 1 RGBS) chalcedonies/agates and A-quartz (for 2 BS.UP) have more representation among the chips. It seems that there are several rock varieties knapped at the site that appear in the immediate surroundings of the cave in secondary context, such as MP1, MP2 (see Data S2) and chalcedonies. The abundance of these raw materials in the immediate surroundings could be a reason for the low rate of retouched implements, meaning that the proximity of local (secondary sources) eliminated the necessity to resharpen tools by retouch as there were plenty of readily available rocks for knapping. Nonetheless, the low rate of retouch could also be related to the specific area excavated (sample spatial bias) or the specific activities conducted on site, which perhaps did not demand 'robust' retouched functional edges or the resharpening of tools. The percentage of non-cortical flakes (0) is high in all the allostratigraphic units and in all of them surpass 50%. There is a decrease from 1 RGBS to 2 BS regarding the presence of cortex, which may indicate a gradual change in terms of raw material management. With the information at hand, it is difficult to assess what the specific strategies for people at Border Cave were, but what is clear is that there were raw material preferences (specific rhyolite variants) linked to the different periods.

The provisioning and management of raw materials have been amongst the most discussed topics in relation to lithic technological strategies in the past few decades, particularly for MIS 4 (e.g. [START_REF] Minichillo | Raw material use and behavioral modernity: Howiesons Poort lithic foraging strategies[END_REF]Will, 2021). Some authors have linked MIS 4 assemblages to fine-grained raw materials and non-local rock at the archaeological sites studied (although this is the case in sites like Klasies River, other sites do not show this pattern). If we look at the distributions at Border Cave, it does not seem to be the case as 2 BS.UP (associated with MIS 3) has a high percentage of A-quartz and chalcedonies and agates among the chips. [START_REF] Mackay | Coalescence and fragmentation in the late Pleistocene archaeology of southernmost Africa[END_REF] proposed for southern Africa that during MIS 4 there was more 'place provisioning' rather than 'individual provisioning', whereas for the post-HP at Klein Kliphuis he proposed the contrary; individual provisioning. Place provisioning implies the transportation of raw materials to a selected place for the manufacture of artefacts [START_REF] Parry | Expedient core technology and the organization of technology[END_REF]. Individual provisioning implies the continuous transport and maintenance of tools that are used on a daily basis by hunter-gatherers [START_REF] Binford | Organization and formation processes: looking at curated technologies[END_REF]. Between these two theoretical models there is probably a lot of variation in the solutions applied in the MSA. These differences depend on a complex interaction between raw material availability, differential site use, and the position of the localities in the settlement system (Will, 2021). [START_REF] Cochrane | An analysis of lithic artefacts from the ∼60 ka layers of Sibudu Cave[END_REF][START_REF] Cochrane | The transition from Howieson's Poort to post-Howieson's Poort industries in southern Africa[END_REF] was around 20 km away so silcrete pebbles were beyond the daily foraging range. In MIS 3 the coast and thus cobblestone beaches with silcrete pebbles were much closer and consequently the MIS 3 assemblage contains higher frequencies of cobble cortex. These changes in the landscape are considered to be related to lithic curation and occupation intensity. The authors propose an opposite model to that of de la Peña and Wadley (2017) for Sibhudu. They propose that during MIS 4 the site would have seen longer occupations and less movement, resulting in more intense exploitation of the raw materials because the outcrops were further away than during MIS 5 and MIS 3.

Flaking systems: comparisons and implications

The presence of cores and core-related by-products imply that there was a certain amount of on-site knapping. In addition to this clue, the percentage of small particles (<2 cm) varies notably between closely associated layers (Figure 11A). As mentioned, this denotes variability in the use of space, reflecting episodes or events of occupation when knapping or resharpening was conducted, in contrast to other layers which are perhaps related to the use of tools or other activities (therefore the drastic drop in small particles).

The type of cores and core-related by-products, together with the attribute analysis of the flakes, have highlighted several technological similarities and differences between the sub-member unit lithic packages. In several attributes (e.g. typometry of the blanks and platforms, elongation index, presence/absence of certain technologically significant items or bidirectional scar pattern) the lower sub-member units (from 1 RGBS to 2 WA.MD) show a certain degree of similarity, whereas from 2 WA.MD upwards each of the sub-member units show distinct characteristics. In terms of reduction sequences, it seems that discoidal and Levallois recurrent centripetal varieties of knapping appear and disappear. Crested blades appear only in 2 WA.LR and they are the only sign in the technological analysis that indicates clear blade preparation of cores. Platform cores for bladelet production appear and disappear, and they are proof that during MIS 3 there were knapping modalities for the production of small blanks too (as proposed for the HP at Sibhudu by de la Peña and [START_REF] De La Peña | New knapping methods in the Howiesons Poort at Sibudu (KwaZulu-Natal, South Africa)[END_REF].

Levallois recurrent centripetal and discoidal are common in MIS 3 contexts (e.g. [START_REF] Conard | Examining the causes and consequences of short-term behavioral change during the Middle Stone Age at Sibudu, South Africa[END_REF][START_REF] Will | Assemblage variability and bifacial points in the lowermost Sibudan layers at Sibudu, South Africa[END_REF]Will, 2019) although they are not exclusive. [START_REF] Soriano | Blade technology and tool forms in the Middle Stone Age of South Africa: the Howiesons Poort and post-Howiesons Poort at Rose Cottage Cave[END_REF], Douze et al.

(2018) and de la Peña (2015b) describe independent flaking methods associated with MIS 4-HP and of course much older chronologies (Schmidt, 2019). The presence of semicrests for blank production have been described in the MIS 4-HP layers at Sibhudu (de la Peña and [START_REF] De La Peña | New knapping methods in the Howiesons Poort at Sibudu (KwaZulu-Natal, South Africa)[END_REF]de la Peña, 2015b), and two opposed platform (parallel) cores were described by [START_REF] Villa | Border Cave and the beginning of the Later Stone Age in South Africa[END_REF]. In the assemblage studied here, this type of reduction was also documented, but we identified it as a

Levallois variant, though this should be checked when a larger sample is available. In terms of lithic knapping methods, the two opposed platform core is prominent in 2 WA.LR, whereas discoidal is foremost in 2 WA.UP and 2 BS.LR, and it does not disappear. The absence of certain lithic flaking strategies described in other MIS 4 and MIS 3 sequences is noteworthy. In this vein, [START_REF] Villa | The Howiesons Poort and MSA III at Klasies River main site, cave 1A[END_REF] described the 'HP cores' as for the production of blades in the HP at Klasies River, which also appear at Sibhudu for the HP (de la Peña and Wadley, 2014a;de la Peña, 2015b;[START_REF] Soriano | The Still Bay and Howiesons Poort at Sibudu and Blombos: Understanding Middle Stone Age technologies[END_REF][START_REF] Will | Regional patterns of diachronic technological change in the Howiesons Poort of southern Africa[END_REF]. At Border Cave, this is completely absent in the members studied. There is also a total absence of bipolar knapping, which has been described as associated with quartz for the HP (de la Peña, 2015) and quartzite for the post-HP at Sibhudu Cave (de la Peña and Wadley, 2017). This absence is particularly striking for the 2 BS.UP assemblage (vide infra).

Implements

The percentage of retouched pieces is very low in all the sub-member units studied here. This is a normal characteristic of many MSA lithic assemblages, and sometimes when a great number of retouched pieces are encountered, they are pseudo-retouched pieces created by post-depositional processes (de la Peña and Witelson, 2018 and references therein). The most abundant retouched pieces in our assemblage are 'points' or triangular blanks (Timbrell et al., this volume). All the triangular blanks/points from the sub-member units were studied separately in a focused analysis combining technology and morphometry. The results show how different morphologies can be associated with the varieties of knapping (discoidal, Levallois recurrent and Levallois with two opposed platforms). Additionally, the Border Cave sample from Members 2 WA and 2 BS overlaps morphometrically with the Sibudan morphotypes described by [START_REF] Conard | What is in a name? Characterising the 'post-Howiesons Poort' at Sibudu[END_REF] and [START_REF] Conard | Examining the causes and consequences of short-term behavioral change during the Middle Stone Age at Sibudu, South Africa[END_REF].

For Member 3 BS and sub-member units 2 WA.LR-MD it is also worth mentioning the documentation of trimmed base points (Emireh points) and backed knives (Audi knives) described by [START_REF] Beaumont | Border Cave[END_REF] for 2 WA and 3 BS (respectively). To our knowledge, these pieces have only been described at Border

Cave for the MSA of southern Africa. In the new collection, there are two examples of trimmed base points and backed (Audi) knives. The small number of these pieces does not allow us at this stage to further investigate their technological and morphometrical characteristics.

The low number of retouched pieces could mean that there was no need for resharpening in the activities conducted (as there was a nearby source of rocks available), or because the activities conducted at the site did not demand secondary shaped edges. The high representation of triangular blanks (Timbrell et al., this volume) and the low number of backed pieces is striking, as is the complete absence of grindstones, in contrast to the lowermost post-HP layers at Sibhudu Cave, where 18 grindstones or grindstone fragments were documented in layers BYA2i to YA (de la Peña and Wadley, 2017).

Other technologies

Other specialists working on the same assemblage have highlighted other relevant aspects of the material culture associated with Members 1 RGBS to 2 BS. For example, regarding bedding, Sievers et al. (this volume) describe changes in their construction. In units 3 BS, 2 WA and 2 BS.LR sedge nutlets, including Cyperus prolifer and Cyperus pseudovestitus, were documented in the bedding, whereas no sedge remains were recovered from younger bedding in 2 BS.UP.

Within the assemblage from Members 2 WA and 2 BS it is worth mentioning other implements such as the Vachellia karroo thorns interpreted as awls (Beaumont 1978: 37, Fig. 22), warthog tusks with traces of scraping and grinding interpreted as daggers (Figure S1C;Beaumont 1978: 38, Fig. 25;Beaumont et al., 1978: 412) and awls [START_REF] Villa | Border Cave and the beginning of the Later Stone Age in South Africa[END_REF], and a bone in Member 2 WA in the form of a charred rib fragment with notches along one edge (Figure S1; Beaumont 1978, Vol. II: 302, Figs. 7 and 8;[START_REF] Villa | Border Cave and the beginning of the Later Stone Age in South Africa[END_REF].

It is interesting to see how technological traditions change through time in this organic assemblage in comparison with lithic technology trends. It is also worth mentioning that these items are associated with MIS 3, because they are often forgotten about in MSA revisions.

Comparison with previous lithic analyses

The lithic assemblage from Members 1 RGBS and 3 BS was assigned to the epi-Pietersburg [START_REF] Beaumont | Border Cave[END_REF] and later to the HP by [START_REF] Grün | Border Cave revisited: a revised ESR chronology[END_REF]; whereas the lithics from Members 2 WA and 2 BS were assigned to MSA 3/post-HP by [START_REF] Beaumont | Border Cave[END_REF]. The MSA 3/post-HP attribution of 2 WA and 2 BS was also proposed in a more recent analysis conducted by [START_REF] Villa | Border Cave and the beginning of the Later Stone Age in South Africa[END_REF]. In the publication of [START_REF] Grün | Border Cave revisited: a revised ESR chronology[END_REF] an industrial sequence was proposed, but the lithics were not part of the discussion. Thus, for the putative HP the more in-depth analysis is the one of [START_REF] Beaumont | Border Cave[END_REF] concerning excavation 3A rear.

Starting with 1 RGBS and 3 BS [START_REF] Beaumont | Border Cave[END_REF] highlighted the abundance of blades (that he associated with the 'punch' technique (sic)), the presence of backed elements (some of them similar to Châtelperron and Abri Audi knives) and the occasional representation of small 'pressured flake' triangular items (Figure 1C and Figure 9). For Members 2 WA and 2 BS the excavation 3A rear assemblage was characterized by the absence of 'crescents' (sic) and a low number of points. He also distinguished an early phase (Members 2 WA and 2 BS.LR C), characterized by 'modified butts' (sic) (facetted platforms) and low values of chalcedony and scaled pieces; and a late phase (the upper part of Member 2 BS) with high values of the latter two. Another aspect stressed for this later phase is the high number of dihedral and polyhedral platforms and radial prepared cores, and very low number of points and retouched pieces (Beaumont, 1978: 103). One of the conclusions of his techno-typological study was that the assemblage from Members 2 BS and 2 WA was probably a 'terminal occurrence within the MSA' (Beaumont, 1978: 103). Even though he highlighted the absence of backed pieces, in the only graphic representation that he made of the MSA 3 material he included trapeze or double truncated backed pieces (Beaumont, 1978: 137, Fig. 88;Beaumont et al., 1978: 411, Fig. 4B). The revision of a small sample of excavation 3A rear material by [START_REF] Villa | Border Cave and the beginning of the Later Stone Age in South Africa[END_REF] highlighted that 2 WA was characterized by blades and elongated flakes with parallel sides and considered as 'the main objectives of the debitage'. They also characterized the cores from this part of the sequence as having two opposed striking platforms and therefore with bidirectional removals. This type of knapping was associated in that study with a variety of end-products, but mainly 'pointed forms' (sic). They also highlighted an independent flake production in 2 WA by the presence of Levallois flakes and one Levallois core. They also proposed that the knapping technique was direct percussion by stone hammer, and the blows were probably away from the platform edge, making a clear distinction with the lower HP members (which were associated with soft hammer percussion with a stone hammer).

For 2 BS Lower A+B and 2 BS.UP they documented in their analysis a decrease in blade production and retouched pieces, the disappearance of unifacial points and rise of bipolar knapping (associated not with rhyolite varieties but chalcedony and xenomorphic and automorphic quartz). The increase in bipolar knapping from 2 BS.UP was interpreted as 'a change towards the Later Stone Age'.

Before highlighting the specific technological aspects and comparing Beaumont's and Villa et al's.

(2012) results with the present analysis, it must be stressed that there is a striking difference in the [START_REF] Villa | Border Cave and the beginning of the Later Stone Age in South Africa[END_REF] paper in comparison with our assemblage, which is the much higher percentage of cores (2 WA-0.8%, 2 BS-1.7%) and retouched pieces (2 WA-5.2%, 2 BS-3.4%) in their analysis.

Moreover, for 2 BS.UP our assemblage only has one core, whereas for their 2 BS.UP these cores constitute 5.4% of the lithic assemblage. Our analysis has highlighted different flaking strategies and raw material selection. In some instances, we are in accordance with some of the previous propositions, but in others, we offer some nuances and a different set of technological trends.

In our analysis, 1 RGBS was the smallest group and difficult to characterize technologically. However, the different attributes observed (and frequencies of these), and the raw material characterization linked it to 3 BS and 2 WA.LR-MD (see non-metric dimensional analysis in Figure 10). Contrary to [START_REF] Villa | Border Cave and the beginning of the Later Stone Age in South Africa[END_REF], we did not observe clear blade production in 1 RGBS, whereas this was attested for 3 BS and 2 WA.LR. Moreover, regarding the knapping techniques, we observed smaller platforms for 3 BS and 2 WA.LR (with no statistical difference between the two), but 1 RGBS had much higher values (and statistically different from the other members). Knapping techniques are extraordinarily difficult to assess (cf. [START_REF] Driscoll | Their lips are sealed: identifying hard stone, soft stone, and antler hammer direct percussion in Palaeolithic prismatic blade production[END_REF][START_REF] Pelegrin | Les techniques de débitage laminaire au Tardiglaciaire: critères de diagnose et quelques réflexions[END_REF], particularly for southern African rocks (further experimentation is needed as proposed by de la Peña, 2015b). The data regarding platforms contradicts the expectation that platforms in 2 WA should be bigger than in 3 BS and 1 RGBS (as one would expect smaller platforms in blade production), and analyses show a correlation between 2 WA.

LR and 3 BS.

In our assemblage, we see the clearest blade production, meaning elongated blanks (double the length than the breadth, and parallel edges) in 2 WA.LR-3 BS. This is in accordance with [START_REF] Villa | Border Cave and the beginning of the Later Stone Age in South Africa[END_REF] knapping modality from two opposed platform cores for 2 WA (that we described from the debitage attributes and core-related by-products). 2012) cores constitute over 5 % of the lithic assemblage. This could be because there are lateral technological changes within the same sub-member units, as attested in our analysis for example of 2 WA. However, the contrast is so remarkable that a different resolution in the method of excavation between Beaumont's and the recent excavations [START_REF] Backwell | New excavations at Border Cave, KwaZulu-Natal, South Africa[END_REF][START_REF] Backwell | Border Cave: A 227,000-year-old archive from the southern African interior[END_REF] should not be ruled out. Indeed, amongst the material from 1 WA and 1 BS from the new excavations bipolar cores are documented (personal observation PdlP).

This comparison, taking into account only the technological characteristics, points to gradual change from 1 RGBS to 2 WA.MD, and differences in technology in each sub-member above. Moreover, it differentiates two sets of technological characteristics within 2 WA and 2 BS.

On the cultural attribution of this assemblage and technological comparisons

In the past decade, different lithic technological researchers have shown the enormous variability associated with the MSA in southern Africa. Not only for the Still Bay and HP but also for earlier and later time spans [START_REF] Soriano | Blade technology and tool forms in the Middle Stone Age of South Africa: the Howiesons Poort and post-Howiesons Poort at Rose Cottage Cave[END_REF][START_REF] Will | Characterizing the Late Pleistocene MSA lithic technology of Sibudu, KwaZulu-Natal, South Africa[END_REF]Bader, 2015;[START_REF] Douze | Techno-cultural characterization of the MIS 5 (c. 105-90 Ka) lithic industries at Blombos Cave, Southern Cape, South Africa[END_REF]Pazan et al., 2022, among others). Stone tools have also been instrumental in discussions on human complexity in the MSA.

All of this research highlighted a great amount of variability, different from the image proposed in previous decades, which characterized the MSA as monotonous, apart from the Still Bay and HP Industries (see Wurz, 2013 for a synthesis). Even if there have been notable efforts of going beyond mere technological description and trying to explain population dynamics, mobility patterns, and evolutionary strategies during this period [START_REF] Mackay | Coalescence and fragmentation in the late Pleistocene archaeology of southernmost Africa[END_REF]d'Errico et al., 2017;[START_REF] De La Peña | Technological variability at Sibudu Cave: The end of Howiesons Poort and reduced mobility strategies after 62,000 years ago[END_REF][START_REF] Wilkins | Lithic technological responses to Late Pleistocene glacial cycling at Pinnacle Point site 5-6, South Africa[END_REF][START_REF] Archer | Carrying capacity, population density and the later Pleistocene expression of backed artefact manufacturing traditions in Africa[END_REF]Way et al., 2022, among others), a great deal of the debate regarding lithics still revolves around the definition of culture-historic units (e.g. [START_REF] Porraz | The MSA sequence of Diepkloof and the history of southern African Late Pleistocene populations[END_REF]. Indeed, the debate is still heavily influenced by the fossiles directeurs, such as backed pieces or bifacial/unifacial points. Even knapping methods are used as fossiles directeurs, in a similar manner to the technological debate on the Upper Palaeolithic of Europe (de la Peña, 2012; [START_REF] Reynolds | House of cards: cultural taxonomy and the study of the European Upper Palaeolithic[END_REF].

The HP has received much attention by scholars of African prehistory because it shows technical and symbolic characteristics that only developed in an extensive manner much later in other parts of the world. Therefore, the African Middle Stone Age, through the material of the HP, holds some of the oldest symbolic and complex technologies known (see de la Peña, 2020 and references therein).

In the last two decades a great deal of research effort has focused on refining the technological definition of the HP [START_REF] Wurz | The Middle Stone Age at Klasies River, South Africa[END_REF][START_REF] Soriano | Blade technology and tool forms in the Middle Stone Age of South Africa: the Howiesons Poort and post-Howiesons Poort at Rose Cottage Cave[END_REF]Mackay, 2008;[START_REF] Villa | The Howiesons Poort and MSA III at Klasies River main site, cave 1A[END_REF][START_REF] Porraz | The MSA sequence of Diepkloof and the history of southern African Late Pleistocene populations[END_REF]de la Peña andWadley, 2014a, b, 2017;de la Peña, 2015a, b;[START_REF] Soriano | The Still Bay and Howiesons Poort at Sibudu and Blombos: Understanding Middle Stone Age technologies[END_REF]de la Peña et al., 2018;[START_REF] Wilkins | Lithic technological responses to Late Pleistocene glacial cycling at Pinnacle Point site 5-6, South Africa[END_REF][START_REF] Tabrett | The detachment of Levallois flakes using bipolar percussion at Howiesons Poort Shelter, South Africa[END_REF][START_REF] Douze | The Howiesons Poort lithic sequence of Klipdrift Shelter, southern Cape, South Africa[END_REF][START_REF] Will | Regional patterns of diachronic technological change in the Howiesons Poort of southern Africa[END_REF]. Some authors have highlighted its coherence within South Africa, in terms of technological trends [START_REF] Porraz | The MSA sequence of Diepkloof and the history of southern African Late Pleistocene populations[END_REF][START_REF] Mackay | Coalescence and fragmentation in the late Pleistocene archaeology of southernmost Africa[END_REF][START_REF] Soriano | The Still Bay and Howiesons Poort at Sibudu and Blombos: Understanding Middle Stone Age technologies[END_REF] or the fact that different phases can be distinguished techno-typologically [START_REF] Porraz | The MSA sequence of Diepkloof and the history of southern African Late Pleistocene populations[END_REF][START_REF] Douze | The Howiesons Poort lithic sequence of Klipdrift Shelter, southern Cape, South Africa[END_REF].

The HP has been associated with the presence of large, backed pieces (Thackeray, 1991), blade production [START_REF] Wurz | The Middle Stone Age at Klasies River, South Africa[END_REF] (first associated with indirect percussion by Wurz and later associated with soft stone percussion by [START_REF] Soriano | Blade technology and tool forms in the Middle Stone Age of South Africa: the Howiesons Poort and post-Howiesons Poort at Rose Cottage Cave[END_REF], and the putative greater use of non-local rocks (sometimes referred to as 'exotic' [START_REF] Minichillo | Raw material use and behavioral modernity: Howiesons Poort lithic foraging strategies[END_REF]. Mackay and colleagues (2014: 36) highlighted three technological aspects that can be traced across South Africa during the HP: the form of implements (backed pieces with crescent morphologies), the production of small blades, and the fact that assemblage sizes are either proportionally very large (total numbers of artefacts) or very dense (numbers of artefacts per unit volume) relative to other industries. Other authors have identified technological strategies that are not necessarily found across southern Africa, such as bifacial production (de la Peña et al., 2013;[START_REF] Porraz | The MSA sequence of Diepkloof and the history of southern African Late Pleistocene populations[END_REF], bipolar knapping associated with the production of small blanks (de la Peña and [START_REF] De La Peña | New knapping methods in the Howiesons Poort at Sibudu (KwaZulu-Natal, South Africa)[END_REF], de la Peña, 2015a, b) and Levallois core recycling into bipolar cores [START_REF] Tabrett | The detachment of Levallois flakes using bipolar percussion at Howiesons Poort Shelter, South Africa[END_REF]. Notwithstanding these efforts, the main feature used to identify this technological tradition is the presence of backed pieces. In particular, a proliferation of backed pieces specifically seems to be the main criterion used to identify this industry [START_REF] Way | Howiesons Poort backed artifacts provide evidence for social connectivity across southern Africa during the Final Pleistocene[END_REF], because backed pieces also occur before and after the HP in the MSA archaeological record (e.g. [START_REF] Brown | An early and enduring advanced technology originating 71,000 years ago in South Africa[END_REF][START_REF] Wadley | Two moments in time during Middle Stone Age occupations of Sibudu, South Africa[END_REF]. Recently, Archer (2021) observed that both site numbers and backed artefact discard rates increase during the HP across all of southern Africa and suggests that it is the interaction between increased climatic variability and increased population density that accounts for the increased frequency in the production of this tool. Backed artefacts were proposed to correlate with proxy measures of demographic changes, while other tools, such as points, scrapers and denticulates did not show a statistically significant correlation. Way and colleagues (2022) have argued that during this proliferation event backed pieces appeared to follow a very similar template in morphology across southern Africa, and this might be related to cultural similarities, and marks a strengthening of long-distance social ties during MIS 4, as previously proposed by [START_REF] Mackay | Coalescence and fragmentation in the late Pleistocene archaeology of southernmost Africa[END_REF] and d [START_REF] Errico | Identifying early modern human ecological niche expansions and associated cultural dynamics in the South African Middle Stone Age[END_REF].

The presence of a backed piece in 1 RGBS and another in 3 BS should be taken with caution as a fossiles directeurs of the HP. As highlighted, backed pieces are not exclusive to the HP, as they appear before and after it. In this vein, it is worth mentioning that in the entire area of the large excavation 3A rear trench of Beaumont (around 21 m 2 ), Member 1 RGBS provided less than 20 pieces (including fragments), and Members 3 BS and 3 WA provided even fewer backed pieces (Beaumont, 1978, Vol. II). At the site of Sibhudu, layer Grey Sand alone recorded 183 pieces (from Wadley's excavation in 6 m 2 ) (de la Peña and [START_REF] De La Peña | New knapping methods in the Howiesons Poort at Sibudu (KwaZulu-Natal, South Africa)[END_REF]. It must be borne in mind that the absence of backed pieces could be conditioned by the use of the site. We know that on some occasions these pieces were related to projectile use (e.g. [START_REF] Lombard | Hunting with Howiesons Poort segments: pilot experimental study and the functional interpretation of archaeological tools[END_REF]de la Peña et al., 2018), but also to other domestic activities [START_REF] Igreja | Functional insights into the innovative Early Howiesons Poort technology at Diepkloof Rock Shelter (Western Cape, South Africa)[END_REF].

Concerning blade production as a technological trait for the HP. In our sample there are technological clues to sustain the presence of this knapping modality in 3 BS and 2 WA.LR (such as the presence of semicrests and the elongation index data). At Sibhudu different blade knapping methods are associated with the HP, such as 'HP-cores' [START_REF] Soriano | The Still Bay and Howiesons Poort at Sibudu and Blombos: Understanding Middle Stone Age technologies[END_REF], prismatic cores (de la Peña, 2015)

and bladelet cores (de la Peña and Wadley, 2014a, b;[START_REF] Soriano | The Still Bay and Howiesons Poort at Sibudu and Blombos: Understanding Middle Stone Age technologies[END_REF]de la Peña, 2015;[START_REF] Will | Regional patterns of diachronic technological change in the Howiesons Poort of southern Africa[END_REF]. None of these variants, except some examples of platform/bladelet cores, has been observed in the Border Cave assemblage analysed here.

Regarding non-local raw materials as a trait for HP recognition, 2 BS.UP and 1 RGBS show higher percentages of A-quartz and chalcedonies/agates. However, the latter two fine-grained raw materials are locally available at Border Cave, and on the path to the cave these pieces are abundant in secondary context (colluvium).

Concerning a greater occupation intensity [START_REF] Mackay | Coalescence and fragmentation in the late Pleistocene archaeology of southernmost Africa[END_REF], the previously attributed HP members (1 RGBS and 3 BS) show no significant hot spots in this part of the stratigraphy (Figure 12A).

Unlike the HP Industry, the post-Howiesons Poort or MSA 3 has attracted little attention in the past two decades (but see [START_REF] Cochrane | An analysis of lithic artefacts from the ∼60 ka layers of Sibudu Cave[END_REF][START_REF] Cochrane | The transition from Howieson's Poort to post-Howieson's Poort industries in southern Africa[END_REF][START_REF] Conard | What is in a name? Characterising the 'post-Howiesons Poort' at Sibudu[END_REF]or Will, 2019 for a synthesis). Some years ago, [START_REF] Mitchell | Developing the archaeology of marine isotope stage 3[END_REF] wrote that 'post-HP' was a catch-all category and that much work was needed in order to refine a somewhat biased view of this part of the MSA sequence. Mackay and colleagues (2014) subsequently noted that lithic assemblages associated with MIS 3 are more heterogeneous than other MSA industries. The general trend technologically for the beginning of MIS 3 assemblages is a decrease in backed pieces and substitution with side-scrapers (or "knives") and unifacial points. Moreover, in most of the assemblages documented there is a decrease in blade production compared to the HP (see for example the case of Sibhudu (de la Peña and Wadley, 2017)).

In the last 10 years the new team of researchers excavating Sibhudu has defined a new technocomplex within MIS 3 for the eastern part of southern Africa: the Sibudan, named after the type site Sibhudu

Cave in KwaZulu-Natal [START_REF] Conard | What is in a name? Characterising the 'post-Howiesons Poort' at Sibudu[END_REF][START_REF] Conard | Examining the causes and consequences of short-term behavioral change during the Middle Stone Age at Sibudu, South Africa[END_REF][START_REF] Will | Assemblage variability and bifacial points in the lowermost Sibudan layers at Sibudu, South Africa[END_REF]Will, 2019). Will (2019) defines this technocomplex as characterized by different diachronic variations in the sequence of Sibhudu. The general technological trends for this technocomplex are as follows: "Raw material procurement is predominantly local, with the use of various rock types of different granularity and knapping qualities (dolerite, hornfels, quartzite, sandstone, quartz). Knappers used multiple reduction methods alongside each other within each assemblage, encompassing Levallois, discoid, platform, and bipolar methods. The frequency of each method varies markedly throughout the sequence. In terms of blank production, (convergent) flake and blade assemblages characterize the Sibudan". It must be borne in mind that the Sibudan at Sibhudu Cave is restricted to an age of around 58 ka, and much work still needs to be done in terms of comparisons with other sites for the period that spans the end of the HP to the Later Stone Age.

Regarding the post-HP/MSA 3, Will (2019) has summarized how this terminology explains away the variability associated with MIS 3 lithic strategies. Members 2 BS and 2 WA have been associated with this period in previous analyses conducted by Beaumont and Villa et al. (2012). Regarding the unretouched and retouched points (from 3 BS to 2 BS), Timbrell et al. (this volume) have shown a morphometric overlap with the Sibudan morphotypes described by [START_REF] Conard | What is in a name? Characterising the 'post-Howiesons Poort' at Sibudu[END_REF] and [START_REF] Will | Regional patterns of diachronic technological change in the Howiesons Poort of southern Africa[END_REF]. In addition, the technological traits highlighted for 2 WA.UP, 2 BS.LR and 2 BS.UP match the description of the Sibudan by [START_REF] Wilkins | Is it time to retire NASTIES in southern Africa? Moving beyond the culture-historical framework for Middle Stone Age lithic assemblage variability[END_REF]: raw material predominantly local, Levallois, discoidal and platform as the main knapping methods, and an abundance of convergent flakes (unretouched) (Timbrell et al., this volume).

In summary, the previously attributed HP members (1 RGBS and 3 BS) [START_REF] Beaumont | Border Cave[END_REF][START_REF] Villa | Border Cave and the beginning of the Later Stone Age in South Africa[END_REF] show similarities with the lowermost part of 2 WA (previously attributed to the post-HP). The set of attributes in 1 RGBS and 3 BS, with the evidence at hand, does not match the more recent technological trends associated with the HP. In our analysis, Members 2 WA and 2 BS show different technological trends constrained to specific spatial areas, giving a much more complex perspective of the use of the site for the period 80-40 ka. It is difficult to argue for the presence of the HP in this collection. As recently proposed by [START_REF] Wilkins | Is it time to retire NASTIES in southern Africa? Moving beyond the culture-historical framework for Middle Stone Age lithic assemblage variability[END_REF], it seems that heuristically trying to force the lithic record into cultural categories does not offer much in terms of understanding the past and evolutionary strategies. What seems relevant is the different strategies registered in such a small sample of lithics.

Final remarks

Palaeolithic sites are complex entities to analyse. As proposed by Bailey (2006) in his analysis of archaeology and time, archaeological sites usually (if not always) constitute palimpsests to a different degree (also see [START_REF] Schiffer | Toward the identification of formation processes[END_REF]. Bailey distinguished between different types of palimpsests depending on how the different occupations preserved and are still distinguishable over time. He differentiated, for example between true palimpsests (archaeological deposits that record ''a sequence of depositional episodes in which successive layers of activity are superimposed on preceding ones in such a way as to remove all or most of the evidence of the preceding activity'' (Bailey, 2006:204)) or cumulative palimpsests (archaeological deposits that record ''the successive episodes of deposition, or layers of activity, which remain superimposed one upon the other without loss of evidence, but are so re-worked and mixed together that it is difficult or impossible to separate them out into their original constituents'' activity'' (Bailey, 2006:204)). Following this lithic technological and spatial analysis there are different reasons to argue that the layers studied record the sporadic presence of different groups for short stays, each characterized by the use of similar raw materials, different but still related knapping strategies, and different sets of techniques and methods. This is consistent with the low content of remains per sediment volume. There is also evidence that in part of the assemblage studied there have been notable post-depositional processes that complicate understanding of the archaeological record, leading to some deposits that may be more timeaveraged than others. Dedicated spatial analyses will need to be applied to tease out patterns within these units (e.g., Reeves et al., 2019). Border Cave seems to be a special case in terms of MSA sites, in that it samples broader behavioural variability both synchronically and diachronically than other sites, and thus complements what sites with more continuous palimpsests (as defined by Bailey) tell us.

Thus, from a site formation point of view, it suggests a sporadic type of palimpsest.

Figure 1 .

 1 Figure 1. A. Location of Border Cave in southern Africa (map courtesy of A. Val). B. Digital model of the terrain at Border Cave in the Lebombo Mountains in South Africa (F. Colino), with the cave overlooking the Eswatini lowveld.

Figure 2 .

 2 Figure 2. A. Site plan showing the position of the various excavations from 1934 to 2019. The orange overlay shows the position of point-plotted artefacts in excavations conducted by us from 2015 to 2019 along the North wall of excavation (EXC.) 3A and South wall of EXC. 4A. The inset (top right) shows the square names excavated by us according to North and East lines. The grid is the original one established by Cooke et al. (1945) in yards and followed by Beaumont. B. Stratigraphic sequence along the North wall showing all plotted lithics and grass mats/bedding represented by dipping horizontal black lines. The dashed line indicates the bottom limit of Beaumont's excavations. C. Stratigraphic sequence along the South wall with plotted lithics and grass mats/bedding shown as black lines. The asterisks mark the squares studied in this manuscript. Figure A: Lucinda Backwell.

Figure

  Figure B and C courtesy of Guilhem Mauran.

Figure 3 .

 3 Figure 3. Percentage of raw materials for fragments and chips <2 cm (A), and 2-4 cm (B) in the entire assemblage. C. Percentage of the different varieties of rhyolites/basalts in the attribute analysis. D. Count of all the lithics that were not rhyolite or basalt in the attribute analysis. E. Percentage of cortex. F. Correspondence analysis of raw materials (in blue the layers and in black the attributes). G. Non-metric dimensional analysis of raw materials showing only the layers. Note how all the lower allostratigraphic members (from 1 RGBS to 2 WA.MD) group together.

Member 3

 3 BS in Figure 5D, E), although there are fragments that could be classified as what Terradas 406 (2003) calls 'multifacial discoidal'. 407 -There are at least three examples of small platform cores with residual scars towards the production 408 of bladelets. The one from Member 2 BS.LR is a parallel core 'recycled' into a bladelet one (Figure 5F). 409 In Member 2 WA.LR there are two examples of platform cores with two opposed striking platforms 410 and a sub-prismatic volume. 411 -Bipolar cores and cores on flakes only appear in Members 2 WA.UP and 2 BS.UP with one example in 412 each. 413

Figure 4 .

 4 Figure 4. Examples of parallel (Levallois recurrent centripetal) cores in Members 2 WA.UP (A and B) and 3 BS (C). KS = knapping surface; SP = striking platform. The pink numbers denote angle between SP and KS. Scales = 1 cm. All raw materials are different varieties of rhyolites. All photographs: P. de la Peña

  , D there are examples of long overshoot blades (probably due to knapping accidents) that are showing two opposed platform cores with quite an acute angle between the striking platform and the knapping surface (around 40-50 degrees), and alternation between the two striking platforms. Because of this angle we classify the cores from where these pieces derive as parallel/Levallois cores. Alternating between the two striking platforms (Figure 6C, D) produced blanks with rectilinear profiles.

Figure 6 .

 6 Figure 6. Examples of core-related by-products from Members 2 BS.UP, 2 BS.LR and 3 BS. A, B, C and D. Knapping surface face with overshoot. E and F semicrests. C and D show the alternation of two opposed platforms. All raw materials are different varieties of rhyolites except for E that is an agate and F that could be a basalt. Scales = 1 cm. All photographs: P. de la Peña

  Douze et al. (2020) call 'technological points'. All of the triangular blanks from Members 2 BS to 1 RGBS are presented in an in-depth study of technology and geometric morphometrics by Timbrell and colleagues (this volume).

Figure 7 .

 7 Figure 7. Examples of triangular blanks from Members 3 BS, 2 WA and 2 BS. 1. Chordal flakes: pseudo-Levallois points and partially debordant flakes. 2. Levallois flakes. 3. Levallois and pseudo-

Figure 8 .

 8 Figure 8. A, B and C. Levallois blanks probably coming from a recurrent centripetal core. D, E and F. Levallois blanks coming from two opposed platform cores. All the examples are from Members 2 BS.LR, 2 WA.MD, 2 WA.LR and 3 BS. All raw materials are different varieties of rhyolites except C that is a quartzite. Scales = 1 cm. All photographs: P. de la Peña.G. Boxplots of elongation index of different Levallois blanks.

Figure 9 .

 9 Figure 9. Examples of retouched pieces in the layers studied. A and D. Retouched points in Member 2 WA.MD and 2 WA.LR that are similar to the 'Emireh points' described by Beaumont (1978) in the post-Howiesons Poort. B. Retouched flake. C. Retouched Levallois flake with macroscars in the proximal area E. Backed piece. F. Straight-backed retouched point that falls into the 'châlteperronian' definition of Beaumont (1978). G. Notched piece. H. Denticulate. Scales = 1 cm. All raw materials are different varieties of rhyolites. All photographs: P. de la Peña

Figure 11 .

 11 Figure 11. A. Stacked chart showing the particle size distribution per layer of all the artefacts in the lithic assemblage reported in Table 2. B. Stacked area showing the distribution of particle size groups in all the members considered. C. Ternary plot of particle size distribution of rhyolite/basalt. D. Number of pieces with visible residues and burnt attributes per allostratigraphic member. E. Spearman's rank analysis comparing lithics with heating attributes, burnt bone (moderate+highly), poor bone surface preservation, and lithics with residues. The bone data for E is from Stratford et al. (2022).

Figure 12 .

 12 Figure 12. A. Kernel density estimation of lithics in Members 3 BS, 2 WA and 2 BS in excavation squares X117, 118, 119 and 120, XZ projection. B. Hot spot analysis conducted with Getis-Ord Gi* of the same squares and members, XZ projection. C. Getis-Ord Gi* spatial analysis of layers Grass Mat 1 (2 BS.LR), Light Reddish Brown (2 WA.UP) and Very Dark Greyish Brown (2 WA.UP), XY projection.

  , Will (2019), de la Peña and Wadley (2017) highlight how in the change from the HP to the post-HP at Sibhudu there were more local rocks knapped at the site. De la Peña and Wadley (2017) described how local raw materials such as sandstone, quartz, dolerite, and even certain varieties of local ochre increased in the lowermost layers attributed to the post-HP (~58 ka). This was interpreted as one of the many clues in that comparison to indicate lower mobility during the post-HP in comparison to the HP. At Pinnacle Point 5-6 Wilkins et al. (2017) reached different conclusions from their assemblage. During MIS 4 the coast

Table 1 . Bayesian model age estimates (Tribolo et al. this volume) of the members analyzed in this study based on individual ESR (Grün et al., 2003) and 14 C measurements (d'Errico et al., 2012; Villa et al., 2012). The Highest Posterior Density (HPD) at 95 % is shown. Cultural attributions are those given in Grün and Beaumont (2001).

 1

	All ESR measurements

Previous technological analyses of the material in Members 1 RGBS to 2 BS

Table 2 . Lithic total counts, weights, and densities by member. Member Total count Sum count per member Total weight (gr) Sum weight per Member Density (count/volume) Density (weight/volume)

 2

	North profile	2 BS.UP	1074	2523	2826	8095	7.39	23.74
		2 BS.LR	1449		5269
		2 WA.UP	707	2507	2362	6048	13.55	32.69
		2 WA.MD	1156		2652
		2 WA.LR	644		1034
		3 BS	1263	1263	1695	1695	6.161	8.268
		1 RGBS	91	N/A	657	N/A
	South profile	2 BS	4
		2 WA	62

Table 3 . Results of contingency tables of raw materials by allostratigraphic member and sub- member and comparisons between pairs in stratigraphic contact. The bold numbers denote a statistically significant difference.

 3

			V
	N=634	p (no assoc.)	Cramer
	All members	5.38E-16	0.296
	2 BS.UP-2 BS.LR	0.501	0.221
	2 BS.LR-2 WA.UP	9.51E-07	0.445
	2 WA.UP-2 WA.MD 1.10E-04	0.546
	2 WA.MD-2 WA.LR	0.654	0.326
	2. WA.LR-3 BS	0.114	0.509
	3 BS-1 RGBS	0.055	0.608

Table 4 . Synthesis of the main types of cores, core related by-products, Levallois and chordal flakes, 414 and retouched pieces found in the assemblage studied from Members 1 RGBS, 3 BS, 2 WA and 2 BS. 415 CORES

 4

	Bipolar core	1
	Inclined	2		1	1	2
	Parallel		2	2		2
	Platform	1	1	1	2
	Core on flake			1
	Test core or nodule					1	2
	Fragment					3
	CORE

2 BS.UP 2 BS.LR 2 WA.UP 2 WA.MD 2 WA.LR 3 BS 1 RGBS

RELATED BY-PRODUCT 2 BS.UP 2 BS.LR 2 WA.UP 2 WA.MD 2 WA.LR 3 BS 1 RGBS

				1	2	2	1
	Change of knapping direction						2	1
	Semicrest		1			3
	Plunging flake	1	1	3		2	1	1
	Levallois	2	18	1	4	2	3
	Chordal	5	22	14	3		4	2
	RETOUCHED	2 BS.UP 2 BS.LR 2 WA.UP 2 WA.MD 2 WA.LR 3 BS 1 RGBS
	Backed piece						1	1
	Denticulate		1
	Macroscars		4	1	3	2	1	1
	Notch	1	1				1
	Retouched flake		6			1

LEVALLOIS AND CHORDAL FLAKES 2 BS.UP 2 BS.LR 2 WA.UP 2 WA.MD 2 WA.LR 3 BS 1 RGBS

Table 5 . Mann-Whitney U test results for lengths of the blanks. In the lower left the value for the test and in the upper right the p (same) values. The results in bold indicate statistically significant differences.

 5

					2
		2 BS.UP	2 BS.LR	2 WA.UP	WA.MD	2 WA.LR	3 BS	1 RGBS
	2 BS.UP		7.76E-05	0.439	0.007	0.000	0.088	0.536
	2 BS.LR 7.76E-05		0.001	0.660	0.185	0.402	0.041
	2 WA.UP	0.439	0.001		0.049	0.004	0.305	0.957
	2 WA.MD	0.007	0.660	0.049		0.122	0.691	0.145
	2 WA.LR	0.000	0.185	0.004	0.122		0.084	0.006
	3 BS	0.088	0.402	0.305	0.691	0.084		0.335
	1 RGBS	0.536	0.041	0.957	0.145	0.006	0.335

Owing to the fact that blades and elongated blanks have been one of the hallmarks of the HP technological tradition

[START_REF] Wurz | The Middle Stone Age at Klasies River, South Africa[END_REF]

we explored the elongation index among all the members considered in this study. As can be seen in the boxplot of the elongation index, Members 2 WA.LR and 3 BS have the lowest values, which indicates greater elongation. The elongation index was not normally distributed, and so we perfomed a Kruskal-Wallis test for equal medians. The results indicate that lithics from Members 3 BS and 2 WA.LR are not distinct from each other, whereas all the rest of the contiguous members are.

Table 6 . Mann-Whitney U test results for elongation index. The results in bold indicate statistically significant differences

 6

						2
		2 BS.UP	2 BS.LR	2 WA.UP 2 WA.MD	WA.LR 3 BS	1 RGBS
	2 BS.UP		0.001	0.5423	0.057	3.85E-05	0.091 0.178
	2 BS.LR 0.001		1.44E-05 0.519	0.002	0.567 0.018
	2 WA.UP	0.543	1.44E-05		0.016	5.65E-06	0.045 0.266

Table 7 .

 7 Chi-squared and Monte Carlo test results of the qualitative attributes comparing all the

	members.
			Monte
		Chi-square p (no assoc.)	Carlo
	Number of scars	0.603	0.603
	Ridges and nodes	0.366	0.357

Table 8 . Chi-squared test of representation of raw materials of retouched pieces per member. The result in bold indicates a statistically significant difference.

 8

		p (no assoc.) V Cramer
	All members	0.001	0.709
	2 BS.UP-2 BS.LR	0.240	0.685
	2 BS.LR-2 WA.UP	0.021	1.000
	2 WA.UP-2 WA.MD 0.221	1.000
	2 WA.MD-2 WA.LR 0.422	0.742
	2. WA.LR-3 BS	0.377	0.817
	3 BS-1 RGBS	0.199	1.000
	3.1.7. Multivariate analysis of all the attributes

Table 9 . Chi-squared test of particle size distribution separated by groups (<2 cm, 2-4 cm, >4 cm) comparing all the members and pairs of members that are stratigraphically contiguous. The results in bold indicate significant differences.

 9

		p (no assoc.)	V Cramer
	All members	1.41E-35	0.133
	2 BS.UP-2 BS.LR	5.18E-12	0.158
	2 BS.LR-2 WA.UP	2.56E-05	0.110
	2 WA.UP-2 WA.MD	6.05E-12	0.176
	2 WA.MD-2 WA.LR	0.313	0.037
	2. WA.LR-3 BS	0.010	0.072
	3 BS-1 RGBS	7.28E-05	0.126

Table 10 . Number of lithics with heating attributes, burnt bone (moderate+highly), poor bone surface preservation, and lithics with residues in the three sub-member units of 2 WA. The data on bones is from J. Clark (Stratford et al., this volume).

 10

		Lithics with heating attributes	Burnt bone (moderate and highly)	Poor bone surface	Lithics with residues
	2 WA.UP	25	1272	197	36
	2 WA.MD	31	189	25	27
	2 WA.LR	12	156	54	5

  However, we have distinguished within 2 WA different sets of technical characteristics for the upper and lower parts of this member. Unit 2 WA.UP is characterized by an abundance of chordal flakes and the presence of Levallois recurrent centripetal cores. Moreover, the raw materials and the flake attributes distance this sub-member from the lower-middle part. Sub-member 2 WA.UP has more continuity with 2 BS.LR where chordal flakes, Levallois centripetal flakes and cores are well represented. Finally, 2 BS.UP can be distinguished, technologically, from 2 BS.LR. As already mentioned, our assemblage has only one bipolar core for 2 BS.UP, whereas forVilla et al. (

Acknowledgements

This paper is dedicated to the memory of our dear lecturer and mentor L. Gerardo Vega Toscano (PdlP and FC).

PdlP acknowledges a Pouroulis

Family Foundation Fellowship in African Quaternary Archaeology and Hominin Palaeoecology at the University of Cambridge, and the action PID2019-1049449GB-I00 funded by the Spanish FEDER/Ministry of Science and Innovation. PdlP is grateful for the help and advice of Carlos Rodríguez-Rellán. LB was funded by a National Geographic Explorer grant (NGS-54810R-19) and DSI-NRF Centre of Excellence in Palaeosciences (Genus) grant (CEOOP2020-1). FdE was supported by the European Research Council (ERC) under the Horizon 2020 program (QUANTA project, contract no. 951388), the Research Council of Norway through its Centres of Excellence funding scheme, SFF Centre for Early Sapiens Behaviour (SapienCE), project number 262618, the LaScArBx research programme (ANR-10-LABX-52), the Talents Programme [grant number: 191022_001], and the Grand Programme de Recherche 'Human Past' of the Initiative d'Excellence (IdEx) of the University of Bordeaux. We acknowledge Aurore Val and Guilhem Mauran for kindly providing Figures 1a and2 respectively. We are grateful to Amafa for issuing us with the excavation permit (SAH 15/7645), and the Evolutionary Studies Institute at the University of the Witwatersrand for housing the Border Cave material. We thank Olga Vilane the Border Cave tour guide for her assistance during excavations and the local community for their support.

Author contributions

Conceptualization PdlP; Data curation PdlP; Formal analysis PdlP, FC; Funding acquisition LB; Methodology PdlP, FC; Project administration LB; Writing -original draft PdlP, FC, LB, FD, LW, WEB, DS; Writing -review and editing draft PdlP, FC, LB, DS.

Declaration of competing interest

The authors declare that they have no competing financial interests or personal relationships that could have influenced the work reported in this paper.