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L'industrie lithique préoldowayenne du site de Fejej FJ-1

L'industrie lithique préoldowayenne du site de Fejej FJ-1
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   Journal of African Archaeology Vol. 9 (2), 2011, pp. 207–224 207 T HE  E ARLY  O LDOWAN  S TONE -T OOL  A SSEMBLAGE   FROM  F EJEJ  FJ-1 A , E THIOPIA   Deborah Barsky, Cécile Chapon-Sao, Jean-Jacques Bahain, Yonas Beyene, Dominique Cauche, Vincenzo Celiberti, Emmanuel Desclaux, Henry de Lumley, Marie-Antoinette de Lumley, François Marchal, Pierre-Elie Moullé & David Pleurdeau  Abstract   Located in the Omo-Turkana basin at the northern limit of the  Koobi Fora sedimentary Formation, the Fejej region has recently  proven to be a rich study area for understanding early hominin behaviour and paleoenvironmental conditions. Among the rich  fossiliferous and stone artefact localities discovered so far at  Fejej, the FJ-1a archeological site has yielded a faunal and lithic assemblage in primary context. The archeological level is situ- ated within a 15 meter uvial sequence beneath a volcanic tuff. Geochronological data from the FJ-1 sequence indicate an age of nearly 1,9 Ma for the FJ-1a artefact level. The stone industry was knapped from locally available raw materials (mainly quartz and basalt) and rocks had been carefully selected according to  specic petrographical and formal criterion. Hominins mastered  several distinct stone knapping methods and used more or less exhaustive reduction sequences in order to produce small akes. The different techniques used for stone reduction are dened in this paper thanks to a series of rets of akes onto cores. Along with the rets, an in-depth analysis of the akes, cores and worked  pebbles provides an overview of the technological capacities of hominins present at the site nearly 2 million years ago. After the  Fejej FJ-1a site was abandoned the archeological materials were rapidly buried, leaving an almost undisturbed archeological level. This site appears to represent a short episode of hominin occupation.  Résumé   Keywords:  Plio-Pleistocene, rets, stone tool assemblage, Ethiopia, Mode 1, Oldowan, variability, technology, knapping  DOI 10.3213/2191-5784-10196 Published online November 2, 2011 © Africa Magna Verlag, Frankfurt M. Deborah Barsky (corresponding author)   8   dbarsky@hotmail.fr    ; dbarsky@iphes.cat * Area de Prehistoria, Universitat Rovira i Virgili (URV), Avinguda de Catalunya 35, 43002 Tarragona, Spain  and   IPHES, Institut Català de Paleoecologia Humana i Evolució Social, C/Escorxador s/n, 43003 Tarragona, Spain Cécile Chapon-Sao /   Jean-Jacques Bahain  / David Pleurdeau   * Département de Préhistoire du Muséum national d’histoire naturelle, UMR 7194 du CNRS, 1 rue René Panhard, 75013 Paris, France Yonas Beyene * Academic and Research Vice President, University of Wolkite, SNNPR, Ethiopia Dominique Cauche /   Emmanuel Desclaux   * Laboratoire départemental de préhistoire du Lazaret, 33 bis bd. Franck Pilatte, 06300 Nice, France Vincenzo Celiberti  * Centre européen de recherches préhistoriques de Tautavel, Ave. Léon Grégory, 66720 Tautavel, France Henry de Lumley /   Marie-Antoinette de Lumley   * Institut de Paléontologie Humaine, Fondation Albert 1 er   Prince de Monaco, 1 rue René Panhard, 75013 Paris, France François Marchal  * UMR 6578 - Unité d’Anthropologie bioculturelle CNRS/Université de la Méditerranée/EFS, Faculté de Médecine, Sect. Nord, Univ. de la Méditerranée, CS80011, blvd. Pierre Dramard, 13344 Marseille Cedex 15, France Pierre-Elie Moullé   * Musée de préhistoire régionale de Menton, rue Lorédan Larchey, 06500 Menton, France (To cite this pre-press online article, please include the standard reference information, the digital object identier and online publication date)  La région de Fejej est située dans le bassin Omo-Turkana, à la limite septentrionale de la Formation sédimentaire de Koobi  Fora. Récemment, cette région s’est avérée être importante pour la compréhension du comportement des homininés et des condi-tions paléoenvironnementales. Parmi les localités découvertes à  Fejej, riches en fossiles et en industries lithiques, le site archéo - logique de FJ-1a a livré un assemblage de faunes et d’industries dans un contexte primaire. Le niveau archéologique est renfermé dans une séquence sédimentaire uviatile sous un tuf volcanique.  Les données géochronologiques de la séquence de FJ-1 indiquent un âge d’environ 1,9 Ma pour le niveau archéologique FJ-1a. Sur le site, des matières premières locales (essentiellement quartz et basalte) ont servi à tailler les industries lithiques. Les homini - nés ont sélectionné les roches selon des critères pétrographiques et géométriques spéciques. Ils maîtrisaient plusieurs méthodes de débitage différentes et utilisaient des séquences de réduction des nucléus plus ou moins exhaustives, an de produire des éclats de petites dimensions. Cet article décrit les différentes techniques de débitage des roches, par la description d’une série de remon- tages d’éclats sur les nucléus. Ensuite, une analyse approfondie des éclats, des nucléus et des galets taillés permet de comprendre les capacités technologiques des homininés présents sur le site de  FJ-1a il y a près de 2 Ma. Après l’abandon du site par les homi- ninés, les ossements et les industries lithiques furent rapidement enfouis, laissant un niveau archéologique en place, indicatif d’un épisode d’occupation de courte durée.   D. Barsky et al. Journal of African Archaeology Vol. 9 (2), 2011 208 Discovery and general context of the Fejej FJ-1 site The Fejej region is located in the Ethiopian sector of the African Rift system in south-western Ethiopia, only 10 kilometres north of the border between Kenya and Ethiopia ( A SFAW   et al.  1991; L UMLEY  & B EYENE  2004) ( Fig. 1 ). The Fejej fossiliferous sediments lie at the northernmost extremity of the Koobi Fora Forma-tion on the east side of Lake Turkana. This Formation is part of the Plio-Pleistocene Omo Group, which also includes the Shungura, Mursi and Usno Formations in the Lower Omo Valley, and the Nachukui Formation west of Lake Turkana ( H EINZELIN  1983; B ROWN  & F EI - BEL  1986; H ARRIS   et al  . 1988). These sedimentary de-  posits include successive volcanic layers, basalt ows or tephras, which have allowed for the elaboration of a precise geochronological framework based on K-Ar and Ar-Ar dating and tephrochonological data. The Omo Group Formations have registered changing environmental conditions over a period of 4.5 million years. Paleogeographical reconstructions based on the nature of the deposits (deltaic, uvial, lacustrine) have revealed that two major hydrographical systems suc-ceeded one another in the Omo-Turkana basin: 1) an episodic lake system and 2) a large axial uvial system named Turkana River or Paleo-Omo River, that owed towards the Indian Ocean through the Anza Rift ( H AR  - RIS   et al.  1988; B ROWN  & F EIBEL  1991; C ERLING  1994; R  OGERS   et al.  1994; F EIBEL  1997).The Fejej region remained unknown in the exten-sively studied Omo-Turkana Basin until 1989, when the rst survey campaigns were organized (Ministry of Ethiopian Culture Paleoanthropological Inventory Team; Berkeley University, California; New York University, NY) ( A SFAW   et al.  1991; F LEAGLE   et al.  1992). Further surveying brought to light more than 50  paleontological and/or archeological localities, dating from the Oligocene to the Late Pleistocene ( L UMLEY  & B EYENE  2004).The FJ-1 locality is a mesa Formation capped by a layer of volcanic ash and covering a surface area of about 450 x 250 m ( A SFAW   et al. 1991; L UMLEY  & B EYENE  2004). Numerous bone remains (including hominins) and a rich stone industry were discovered around the mesa. Given the large extension of the site, the area was subdivided into sectors (indexed FJ-1a through FJ-1k). Sector FJ-1a was selected for excavation since an especially large concentration of worked pebbles and akes was discovered there. Systematic excavations were initially undertaken over a surface area of 9 m² (December 1992; – Janu-ary 1993) and then further extended to 35 m² (May  – June 1997) and nally to 80 m² (December 1998 ; – January 1999). The archeological material (~4 000 artefacts) is stored at the National Museum of Ethio- pia, Addis Ababa, and a complete interdisciplinary study of the site was published in 2004 ( L UMLEY  & B EYENE  2004). Fig. 1.  Location of the Fejej region (a) and other Plio-Pleis-tocene sedimentary Formations of the Omo-Turkana ba-sin (b, after F EIBEL  1993).  The Early Oldowan Stone-Tool Assemblage from Fejej FJ-1a  Journal of African Archaeology Vol. 9 (2), 2011 209 Stratigraphy and sedimentology of the FJ-1a site at Fejej The FJ-1 depositional sequence is described from three isolated outcrops, stratigraphically correlated to com- pose a single sequence measuring 15 m. The entire sequence is divided into ve major units ( Fig. 2 ).- At the base of the sequence, Unit 1 shows lateral variation with two facies ( C HAPON  2007): the first is composed of silt rich in sands and the second of sands with some silt. Sediments are poorly sorted and correspond to high-energy fluvial deposits.- Unit 2 is a polymictic conglomerate with granitic sands. Channelling gures were observed at the  base of the Unit as well as oblique and cross-  bedded stratication indicating a uvial srcin. Metamorphic heavy minerals from Units 1 and 2 show a low degree of polish, indicating short-distance transport. The Fejej region is dominated to the east by the metamorphic Hamar mountain range, culminating at 2000 m and a basaltic pla-teau gently sloping towards Lake Turkana. The immaturity of the sediment and the type of peb- bles in the conglomerate (quartz, basalt, gneiss,  pegmatite and amphibolite), indicate that this Unit was deposited by temporary rivers owing from the northeastern Hamar mountain range towards the southwest into the Omo-Turkana  basin.- Unit 3 is composed of pale yellow silty sands with two layers of calcrete. The Unit shows a bimodal grain-size distribution with poorly classed, mature sediment of uvial srcin. - Unit 4 is a light grey volcanic tuff with horizon-tal lamina and ripple-mark structures. The tuff is mainly composed of glass shards < 2 mm long and includes tubular carbonated concretions and rhizomes. The presence of angular quartz and feldspar grains indicates that the volcanic glass is contaminated by detritus. This Unit corresponds to a pyroclastic deposit in a calm aquatic environ-ment.- Unit 5 is made up of light brown, silty sands with carbonated concretions. Partially dismantled by erosion, it has not yet been the object of a detailed sedimentary analysis.A trench cut into the sedimentary complex of the FJ-1 mesa revealed that archeological level “C1” is located in the basal part of Unit 3, about 3 m below the tephra layer (Unit 4). Fig. 2. Schematic representation of the lithostratigraphy of the FJ-1 locality deposits ( L UMLEY   et al.  2004a). Geochronology of the FJ-1a site Geochronological data from the FJ-1 sequence is pro-vided by magnetostratigraphy, tephrochronology and ESR dating. Magnetostratigraphic analyses show reverse  polarity in Unit 1 and normal polarity in Units 3 and 4 ( C HAPON  2007). The Fejej FJ-1 Tuff (Unit 4) was chemi-cally analyzed by different methods and there has been debate concerning its correlation with other tephra from the Shungura or Koobi Fora Formations ( A SFAW   et al. 1991; H AILEAB  & F EIBEL  1993; F EIBEL  1999). New results from more recent surveys in the Fejej region suggest that the FJ-1 Tuff may be correlated to the Borana Tuff (Koobi Fora Formation) which, in turn, is correlated with an unnamed tuff from the Upper G Member of the Shungura Formation ( C HAPON  2007; C HAPON  et al. 2008; C HAPON  et al.  2011). The age of the archeological layer is therefore between 1.95 ± 0.03 Ma, onset of the Olduvai Sub-Chron, and 1.869 ±0.021 Ma, 39Ar–40Ar age of KBS Tuff ( C ANDE  & K  ENT  1995; M C D OUGALL  & B ROWN  2006). This proposed age is supported by two Electron Spin Resonance (ESR) dates of 2.40 ±0.54 Ma and 1.96 ±0.32 Ma, obtained from quartz grains sampled from Units 1 and 3 respectively ( L UMLEY   et al.  2004a).   D. Barsky et al. Journal of African Archaeology Vol. 9 (2), 2011 210 Bioindicators  Biochronology Faunal remains were systematically collected from stratigraphical Units 1, 3 (archeological layer C1) and 5 ( Tab. 1 ). Biostratigraphical data suggests relatively homogeneous faunal associations in all three Units corresponding to the Upper G and H Members of the Omo Shungura Formation and to the Upper Burgi and KBS Members of the Koobi Fora Formation. The age of Tab. 1. Synthetic table showing presence/absence of dif-ferent vertebrate taxons in each Stratigraphical Unit of the Fejej FJ-1 site ( E CHASSOUX  et al.  2004). the Fejej FJ-1 assemblage is therefore biostratigraphi-cally dated to between 2.33 and 1.78 Ma ( E CHASSOUX   et al. 2004).Although Unit 1 is stratigraphically earlier than the other fossil bearing Units, the relatively poor preserva-tion of the fossils and the low frequency of remains for each species make it difcult to precisely evaluate the  biostratigraphical position of this level. In addition, species’ presence/absence in Unit 1 is not necessarily signicant (for example, the absence of  Metridiochoerus modestus and  Equus , Tab. 1 ). However, the presence of  Elephas recki  cf.  atavus  indicates that this level cannot  be older than the Omo Shungura Formation’s Upper Member F (2.33 Ma). The presence of the genus  Equus  in Units 3 and 5 suggests that the lower chronological limit for these levels may be situated at 2.32 Ma since this species rst appears in Member G of the Omo Shun -gura Formation. According to the appearance/disappear-ance grid for suids ( W HITE  1995), the presence in Unit 3 of  Metridiochoerus modestus and  Notochoerus scotti  situate this level between 1.89 and 1.80 Ma.The micromammals from archeological level C1, including  Arvicanthis morphotype  niloticus/primae- vus, Heterocephalus  cf. atikoi ,  Lepus capensis  and cf. Coleura afra  indicate an open environment and a semi-arid climate. This faunal association is comparable to the upper levels of the Shungura Formation in the lower Omo Valley (Members E, F and lower G; W ESSELMAN  1984) and also to the Koobi Fora Formations in East Turkana ( B LACK   & K  RISHTALKA  1986).The fauna Fejej FJ-1 can be placed within the pale-oclimatic and paleoenvironmental evolution described for the Omo-Turkana Basin for the last 4 million years and may be assigned to the arid event recognised in this area between 2.3 and 2 Ma.  Paleoecological and taphonomical features of the fauna Paleoecological conditions in the Fejej FJ-1 region at the time of the hominin occupation of the FJ-1a site have been assessed from palynological data and faunal associations, both of which translate an open, grassy landscape with wooded areas ( E CHASSOUX   et al.  2004; U MER    et al. 2004). The pollen analysis indicates an evolution towards increased humidity that probably favoured the development of a mosaic, riverside land-scape with forested mountain ranges. The presence of Crocodylus  and sh remains conrm that there was a nearby water source, as does that of the grass-eating antelope Reduncini (Kob) which is generally found in wet areas such as oodplains. In coherence with the  pollen analysis, species’ diversity indicates a variety of ecological settings around the site. Fejej FJ-1Unit 1Unit 3Unit 5 PrimataX Theropithecus  sp.XXX  Paracolobus  sp.XX  Xenocyon africanus X Canis  sp.XHyaenidaeX  Herpestes (Galerella)  sp.XXFelidaeXX  Deinotherium bozasi X  Elephas recki  ssp.X  Elephas recki  cf. atavus X Ceratotherium simum XX  Diceros bicornis XXXEquidaeXXX  Equus  sp.XX  Hexaprotodon aethiopicus X  Notochoerus scotti XX  Metridiochoerus andrewsi XXX  Metridiochoerus modestus XX  Kolpochoerus limnetes XXX Giraffa pygmaea XX  Pelorovis  sp.XXAlcelaphiniX  Aepyceros shungurae XXX Tragelaphus nakuae XXXHippotraginiXRedunciniXXAntilopiniXX Orycteropus sp.Xcf.  Coleura afra X  Lepus capensis X  Hystrix  sp.X  Arvicanthis  gr. niloticus/primaevus X  Heterocephalus  cf. atikoi XChelonia indet.XX Crocodilus  sp.XXAnura indet.XSauria indet.XColubridae indet.Xcf. Claria  sp.XSiluriforma indet.XFish indet.XX  The Early Oldowan Stone-Tool Assemblage from Fejej FJ-1a  Journal of African Archaeology Vol. 9 (2), 2011 211 Although surface finds tend to be altered and strongly mineralized, bones from archeological level C1 are well preserved. Surface remains from Fejej FJ-1 had undergone signicant taphonomical and second - ary biological modications. In contrast, fossil bones recorded from archeological level C1 do not show traces of secondary modication. Fossils from the ar  -cheological level do not appear to have been rolled nor dispersed and their burial in situ  by uvial sediments was probably rapid. Unlike the surface nds, no carni -vore remains were found in level C1 and bones show no traces of carnivore or rodent activity. While surface nds reect a mixed ensemble, those from level C1 were often found in anatomical connexion, with ret -ting bone fragments discovered adjacent to one another, suggesting a highly localized activity area.Fossils are found associated with stone artefacts. Long bones from level C1 were systematically broken and fractured surfaces display smooth edges typical of intentional breakage, as well as impact scars, while no such traces are observed on the surface nds. Evi -dence of human activity, notably fractures on fresh  bones, is frequently observed on shafts, bone splin-ters and determinable epiphysis. Such traces are ob-served on 35 % of the determinable bones and 41 % of the bone splinters. A signicantly high proportion of  Aepyceros shungurae  bones (46 %) also show this kind of intentional breakage (see E CHASSOUX   et al. 2004 for a detailed taphonomical description). The Fejej FJ-1a site represents a seemingly undisturbed archeological level with knapped stone artefacts as-sociated with a faunal assemblage presenting traces of human intervention. Note that the locality FJ-1e (Unit 3), located about 100 m from FJ-1a, has yielded three hominin dental remains attributed to  Homo aff. H. habilis ( L UMLEY  & M ARCHAL  2004). The Fejej FJ-1a stone assemblage and refts The stone assemblage from Fejej FJ-1a ( L UMLEY   et al.  2004b; B ARSKY   et al. 2006) was knapped from local raw materials collected from the alluvial deposits of a small river near the site. Quartz pebbles are dominant (91 %) compared to basalt (7 %) and only a few arte-facts were knapped from other types of rocks (2;%). By comparison, sampling in the FJ-1 conglomerate (Unit 2), located just below archaeological Unit 3 and prob- ably deposited by the same uvial system, revealed that quartz and basalt pebbles each represent about 35 % of available rock types ( Fig. 3 ). So, at Fejej FJ-1a, the quartz pebbles seem to have been preferentially used. This characteristic is not unique to the Fejej FJ-1a as-semblage and is observed elsewhere in the Lower Omo Valley (Shungura Formation, Ethiopia) where quartz often exceeds 90 % of Oldowan assemblage composi-tion even though it is not numerically more frequent than other petrographic groups in the pebble sources ( D ELAGNES   et al. 2011).The overwhelming dominance of quartz in the archeological assemblage shows that Fejej hominins intentionally sought this rock type out for their tools. The quartz pebbles, although jointed, have few inclu-sions and their suitability for knapping is underlined  by the scarcity of angular fragments (debris) relative to well struck akes, as well as by the numerous re -fits of flakes onto cores ( Figs. 4–10 ). However, almost half of the flakes do show transverse or longitudinal fractures which  probably occurred during their extraction. The probability that knapping occurred on-site is sup-  ported by numerous rets of bro - ken akes: 10 Siret accidents, 5 transversal breaks, 1 ventral face fracture. Preservation in the silty sandy Fejej FJ-1a Unit 3 deposits was optimal and, apart from the Fig. 3.  Frequencies of different rock types in the Fejej FJ-1a stone industry and in the nearby Unit 2 conglomer-ate (Unit 2 sample size=254 pebbles); the most likely raw material source.  Note the overwhelming abundance of quartz in the FJ-1a assemblage. 91 %7 %1 %1 %39 %30 %9 %15 %3 %4 %0102030405060708090100quartzbasaltegneisspegmatitesamphibolitesother rocksFejej FJ-1 archeological level C1Conglomerate (sedimentological Unit 2)
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