Géoarchéologie d'une maison semi-souterraine thuléenne-inuit en contexte périglaciaire - étude des processus taphonomiques
Mémoire
Heloïse Barbel
Maîtrise en sciences géographiques - avec mémoire Maître en sciences géographiques (M. Sc. géogr.)
Québec, Canada
© Heloïse Barbel, 2018
RÉSUMÉ Cette recherche a été effectuée dans la baie de Kuuvik (Nunavik, Canada) pour mieux comprendre les occupations dorsétiennes et thuléennes-inuit dans un contexte biophysique postglaciaire en évolution. Des analyses géomorphologiques, stratigraphiques, micromorphologiques, macrofossiles et géochimiques (FTIR et ICP-AES) ont été effectuées sur une maison semi-souterraine unifamiliale hivernale thuléenne-inuit du site Paaliup Qarmangit 1 et dans la vallée dans laquelle elle s’inscrit afin de documenter les processus de formation et la taphonomie de la structure étudiée.
Les données extra-sites ont permis de reconstituer l’évolution des environnements sédimentaires dans la vallée depuis la dernière glaciation. L’approche intra-site a révélé des occupations dorsétienne (après 143-327 cal A.D.) puis thuléennes-inuit (entre 1317-1413 cal A.D. et 1466-1642 cal A.D) du site. Le caractère stratégique du lieu d’implantation (accessibilité aux matériaux de construction, aux ressources alimentaires et hydriques) pourrait expliquer son utilisation par deux cultures différentes successives. Les résultats montrent la prédominance des processus nivéo-éoliens et de nivation dans la formation de l’unité stratigraphique contenant les restes archéologiques et attestent d’un remaniement post-dépositionnels naturels et/ou anthropiques des artefacts dorsétiens. Des signatures chimiques anthropiques modérées mais significatives ont été détectées dans les sols de la maison semi-souterraine (e.g., Mg, Fe, S). Elles pourraient avoir été atténuées par des processus pédologiques, tels que le lessivage et la remobilisation des éléments par les organismes du sol, et/ou des processus anthropiques, tels qu’un nettoyage régulier de la structure par ses habitants.
iii ABSTRACT This research was carried out in Kuuvik Bay (Nunavik, Canada) to document Dorset and Thule-Inuit occupations in an active periglacial context. Geomorphological, stratigraphical, micromorphological, macrofossil and geochemical (FTIR and ICP-AES) analyses were performed over a single-family semi-subterranean Thule-Inuit house of Paaliup Qarmangit 1 site and the surrounding periglacial valley to document site formation processes of the studied structure and to identify anthropogenic chemical signatures in the soil of the house.
Off-site data enabled to reconstruct the sedimentary environments in the valley since the last glaciation. In-site approach revealed a Dorset occupation of the site (after 143-327 cal A.D.) prior Thule-Inuit settlement (between 1317-1413 cal A.D. and 1466-1642 cal A.D.). Strategic features of the site (such as availability of building material, food, and water resources) may explain its use by two different cultures. Results showed the predominance of niveo-aeolian and nivation processes in the formation of the unit containing archaeological remains and provided evidence of post-depositional natural and/or anthropogenic reworking of Dorset artefacts. Soil of the house recorded moderate but significant anthropogenic chemical signatures (e.g., Mg, Fe, S), which may have been buffered by pedological processes, such as leaching and biological remobilization, and/or anthropogenic processes, such as a regular cleaning (maintenance) of the structure.
iv TABLE DES MATIERES
Résumé ...... iii Abstract ...... iv Table des matières ...... v Liste des figures ...... viii Lite des tableaux ...... x Remerciements ...... xii Avant-Propos ...... xiv Introduction générale ...... 1 I Introduction ...... 1 II Contexte physique et occupations humaines ...... 2 1. Géomorphologie et Quaternaire ...... 4 2. Climat de la baie de Kuuvik ...... 7 3. Occupation humaine ...... 8 III Les établissements humains au Nunavik ...... 12 IV La nécessité d’études géoarchéologiques et taphonomiques en milieu périglaciaire actuel ...... 16 V Problématique, objectifs et hypothèses ...... 17 1. Objectif principal ...... 18 2. Objectifs spécifiques...... 18 3. Hypothèses ...... 18 VI Méthodologie ...... 18 1. Campagne de terrain ...... 19 A. Travaux extra-sites ...... 19 a. Relevés topographiques et géomorphologiques ...... 19 b. Stratigraphie et échantillonnage extra-sites ...... 19 B. Travaux intra-sites ...... 21 2. Traitement des données et analyses en laboratoire ...... 21 A. Cartographie ...... 21 B. Analyses macrofossiles ...... 22 C. Datations 14C ...... 22 D. Analyses micromorphologiques ...... 23 E. Analyses géochimiques ...... 24 a. Analyses FTIR ...... 24
v b. Analyses ICP-AES ...... 25 i. Traitement des échantillons en laboratoire ...... 25 ii. Traitement des données et analyses statistiques ...... 26 c. Analyses Raman ...... 29 d. Analyses CNS ...... 30 VII Structure du mémoire ...... 31 Références ...... 31 Chapitre 1 : Paaliup Qarmangit 1 site geoarchaeology: Taphonomy of a Thule-Inuit semi- subterranean dwelling in a periglacial context, northeast Hudson Bay 38
Résumé ...... 39 Abstract ...... 40 I Introduction ...... 41 II Study site ...... 44 III Methods ...... 48 1. Off-site approach ...... 48 2. In-site approach ...... 49 IV Results ...... 51 1. Off-site geomorphology and stratigraphy...... 51 2. In-site stratigraphy and chrono-stratigraphy...... 56 3. Macrofossil analysis ...... 60 4. Micromorphological data ...... 64 A. Common features ...... 64 B. Specific features of natural sediments - shoreline deposits and soils ...... 64 C. Specific features of sediments found inside the house ...... 66 V Discussion ...... 75 1. Site formation processes at the regional and local scales ...... 75 2. Diachronic settlements: Dorset and Thule-Inuit occupations...... 80 3. Post-depositional reworking of anthropogenic remains ...... 82 VI Conclusion ...... 83 Aknowledgments ...... 85 References ...... 85 Chapitre 2 : Geochemistry of a Thule-Inuit semi-subterranean winter dwelling in a periglacial context...... 95 Résumé ...... 96
vi Abstract ...... 97 I Introduction ...... 98 II Study site ...... 99 III Methods ...... 105 1. FTIR analysis ...... 108 2. ICP-AES analysis ...... 108 A. Sample processing ...... 108 B. Data processing and statistical analysis ...... 109 3. CNS analysis ...... 111 IV Results ...... 111 1. FTIR analysis ...... 111 2. ICP-AES analysis ...... 114 A. Box plots and enrichment factors ...... 114 B. Principal components analysis and clustering analyses ...... 118 3. C/N ratio ...... 121 V Discussion ...... 121 VI Conclusion ...... 127 Acknowledgments ...... 128 References ...... 129 Conclusion générale ...... 133
vii LISTE DES FIGURES Introduction générale Figure 1 : Localisation du site Paaliup Qarmangit 1...... 3 Figure 2 : Altitude maximale et extension des mers postglaciaires et des plans d’eau glaciolacustres du nord de la péninsule d’Ungava...... 6 Figure 3 : Courbe d’émersion de la région Baie de Kuuvik – îles Digges établie à partir de la dation de coquilles marines...... 7 Figure 4 : Zones des types de pergélisol pour la péninsule d’Ungava...... 8 Figure 5 : Localisation des structures archéologiques inventoriées dans la vallée étudiée (A) et cartes du site Paaliup Qarmangit 1 (B) et de la structure 10 (C)...... 10 Figure 6 : Maison unifamiliale, structure 10, vue vers l’ouest/sud-ouest, site Paaliup Qarmangit 1...... 11 Figure 7 : Vue de la vallée étudiée vers l’ouest depuis la structure 10...... 12 Figure 8 : Principales différentiations chronoculturelles de l’Arctique nord-américain et du Groenland...... 13 Figure 9 : Prélèvement d’une boîte de Kubiena...... 24
Chapitre 1 : Paaliup Qarmangit 1 site geoarchaeology: Taphonomy of a Thule-Inuit semi-subterranean dwelling in a periglacial context, northeast Hudson Bay Figure 1: Location of the Paaliup Qarmangit 1 site in Kuuvik Bay, northeast Hudson Bay...... 45 Figure 2: Location of archaeological structures inventoried in the studied valley (A), maps of the Paaliup Qarmangit 1 site (B) and the studied structure (C)...... 47 Figure 3: Single-family semi-subterranean house at the Paaliup Qarmangit 1 site (Structure 10)...... 48 Figure 4: Geomorphological map of Paalliq 1 Valley and location of Structure 10...... 53 Figure 5: Active deflation erosion by longitudinal corridors affecting raised beach RB3. .. 54 Figure 6: Off-site stratigraphic cross-sections...... 55 Figure 7: In-site and peri-site stratigraphic cross-sections and location of sampling...... 58 Figure 8: Test-pit I-7, East stratigraphic cross-section...... 60 Figure 9: Location of identified macrofossils...... 63 Figure 10: Location map of micromorphological thin sections...... 68 Figure 11: Primary microstructures...... 69 Figure 12: Organic components...... 70 Figure 13: Cryogenic and physico-chemical processes...... 71 Figure 14: Main microstructures...... 72 Figure 15: Anthropogenic components...... 73 Figure 16: Raman spectrums...... 74 Figure 17: Site formation processes of the Thule house at the Paaliup Qarmangit 1 site. ... 79
Chapitre 2 : Geochemistry of a Thule-Inuit semi-subterranean winter dwelling in a periglacial context Figure 1: Location of the Paaliup Qarmangit 1 site in Kuuvik Bay, northeast Hudson Bay...... 101
viii Figure 2: Location of archaeological structures inventoried in the Paalliq 1 Valley (A), maps of the Paaliup Qarmangit 1 site (B) and the studied structure (C)...... 104 Figure 3: Single-family semi-subterranean house at the Paaliup Qarmangit 1 site (Structure 10)...... 105 Figure 4: Stratigraphy of the studied house...... 107 Figure 5: Some of the Off-site and In-site FTIR spectrums...... 113 Figure 6: Box plots showing off-site (blue) and in-site (orange) distributions of Fe, S, Ca, Cu, P, Mn and Mg contents...... 115 Figure 7: PCA and AHC results...... 120
ix LITE DES TABLEAUX Introduction générale Table 1: Limite de détections des éléments lors de l'analyse ICP-AES...... 27
Chapitre 1 Table 1: Radiocarbon and calibrated ages of the macrofossils and bone fragments sampled in test pits I-2, I-3, I-4, I-5, I-7 and P-1 (in-site samples)...... 59
Chapitre 2 Table 1: Enrichment factors and off-site element contents...... 117 Table 2: Comparison of our in- and off-site element content measurements with natural variability observed in literature for similar contexts...... 124
x
Le plaisir intarissable de l’apprentissage réside dans l’étendue de notre ignorance, que l’on découvre un peu plus à chaque pas, et qui dévoile des univers de savoirs à acquérir. Elisabeth - 54 av. J.-C.
xi REMERCIEMENTS Je tiens tout d’abord à remercier ma directrice de recherche, Najat Bhiry, sans qui ce projet n’aurait pas vu le jour. Merci pour ta confiance et ton encadrement pendant toute la durée de ce projet, merci de m’avoir fait découvrir le plaisir de travailler au Nunavik.
J’exprime également tous mes remerciements à Dominique Todisco, pour m’avoir co- encadrée tout au long de ce projet. Merci beaucoup pour tous tes précieux conseils, tes encouragements et ta présence constante malgré la distance.
Merci à Pierre Desrosiers ; merci pour ton encadrement sur le terrain, ton aide et tes conseils, merci pour l’intérêt que tu as porté à mes travaux pendant ces trois dernières années. Et merci pour ces innombrables anecdotes qui réchauffaient nos soirées nordiques…
Merci également à James Woollett d’avoir accepté d’être examinateur de ma maîtrise.
J’adresse aussi mes plus sincères remerciement aux professionnel·le·s de recherches sans qui mes travaux n’auraient pu aboutir. Merci à Stéphane Ferré pour son dévouement et son travail remarquable à la réalisation des lames minces, merci pour toutes ces discussions à bâtons rompus. Merci à Myosotis Bourgon Desroches pour toute l’aide qu’elle m’a apportée en paléoécologie, merci pour sa patience et sa sympathie. Merci également à Guillaume Labrecque (datations radiocarbones), François Paquet-Mercier, Alain Brousseau et Stéphane Prémont (analyses géochimiques).
Je tiens également à remercier tous·tes celleux qui m’ont apporté aide et conseils lorsque j’en ai eu besoin. Merci à Michel Caillier, Don Butler, Ann Delwaide, Pascal Bertran, Arnaud Lenoble, Alain Queffelec, Catherine Fox, Donald Cayer, Émilie Saulnier-Talbot, Marcel Blondeau, Jean Luc Mercier, Yves Monette, Daniel Fortier, Martin Lavoie, Martin Simard, Sylvie St-Jacques, Louise Marcoux, Edward Schofield, Javier Tardio, et Dominique Marguerie. Je remercie également particulièrement Gabrielle Filteau, Willie Kumarluk, Camille Le Gall-Payne et Marianne Ricard pour leur aide sur le terrain ; merci à Yann pour son aide au microscope, à Céline Dupont-Hébert pour l’aide à l’identification des ossements et à Samuel Auger pour son aide à l’identification de macrorestes.
xii J’exprime mes plus sincères remerciements à la communauté d’Akulivik pour avoir fait appel à nous pour cette belle collaboration. Je remercie particulièrement nos collaborateur·rice·s sur le terrain, Joanasi Qaqutuk, Thomassie Irqumia, Joseph Tulugak, Davidee Angiyou et Niali Aliqu.
Je remercie sincèrement toute l’équipe administrative du Centre d’études nordiques et du département de géographie de l’Université Laval, pour son accueil et son efficacité.
Merci également au Centre de recherche en sciences naturelles et génie du Canada (CRSNG), à l’Institut polaire français Paul-Émile Victor, au Centre d’études nordiques, à l’Institut Culturel Avataq, à la communauté d’Akulivik et à l’AELIÉS pour leur soutien financier.
Enfin, ma plus profonde gratitude va à mon entourage, qui m’est si cher et sans qui rien de tout cela n’aurait été possible. Merci les poteaux, d’ici et d’ailleurs. Merci à Yodette et Hélory pour votre complicité, votre aide et ces merveilleux moments passés ensembles. Merci à Sébastien, Francis et Jeff pour ces heures de plaisir, de défoulement et de dégustation, merci à Wai et Tommy pour ces soirées musicales merveilleuses et trépidantes, merci à Susa notamment pour toute ton aide linguistique dans une belle joie de vivre permanente. Merci à Maud, Pierre-Olivier, Antoine, Julien, Joanie et tous·tes celleux que je n’ai malheureusement pas la place de mentionner ici. Merci à toi, Céline, d’avoir été aussi présente dans les moments où j’en avais le plus besoin, avec ton humour, ton positivisme et tes conseils inestimables. Merci à mes patates, merci de faire partie de ma vie et d’avoir été là à chaque instant malgré la distance, merci à ma petite éclipse. Merci à la famille Barbel-Le Page pour votre indéfectible soutien depuis le début, d’avoir toujours cru en moi sans jamais remettre en question mes choix de vie ; merci à Patrice et à ma Mini Jo’ pour votre compréhension, votre écoute et vos encouragements à chaque instant, vos conseils, vos colis et votre amour ; à Guillaume pour ta présence et nos interminables skypes ; à Huguette pour ces merveilleux moments passés sur les côtes de notre belle région battue par les vents...
Merci à tous·tes, je vous en suis infiniment reconnaissante.
xiii AVANT-PROPOS A l’exception de l’introduction générale et de la conclusion générale écrites en français, ce mémoire est présenté sous forme de deux articles rédigés en anglais (chapitres 1 et 2). Ils constituent le corps du mémoire et sont présentés tels qu’ils seront soumis aux revues. Ces deux articles sont complémentaires, chacun répondant à différents objectifs spécifiques avec une méthodologie qui lui est propre. Le·a lecteur·rice est par conséquent prié·e d’excuser certaines répétitions tels que la description du site d’étude, chaque article étant complet en lui-même et pouvant être lu indépendamment du reste du mémoire. L’auteure du mémoire est la principale rédactrice et auteure de chaque article.
Les différentes sections du présent mémoire sont :
Introduction générale
Chapitre 1 – Barbel, H., Bhiry, N, Todisco, D., Desrosiers, P. M. & Marguerie, D. – Paaliup Qarmangit 1 site geoarchaeology: Taphonomy of a Thule-Inuit semi-subterranean dwelling in a periglacial context, northeast Hudson Bay. Sera prochainement soumis à la revue Geoarchaeology, An International Journal.
Chapitre 2 – Barbel, H., Todisco, D, Bhiry, N. – Geochemistry of a Thule-Inuit semi- subterranean winter dwelling in a periglacial context. Sera prochainement soumis à la revue Journal of Archaeological sciences.
Conclusion générale
xiv INTRODUCTION GÉNÉRALE
I INTRODUCTION Des études archéologiques et géoarchéologiques réalisées récemment au Nunavik (Québec) et au Labrador ont permis d’acquérir des connaissances diversifiées et nouvelles portant sur l’occupation du territoire durant les derniers 2500 ans, sur les modes de subsistance des populations arctiques passées, et sur les processus de formation des sites. Ces études ont notamment été effectuées sur des sites archéologiques situés sur la rive sud du détroit d’Hudson, dans la région d’Inukjuak ou encore au Labrador, dans les régions de Okak Bay et Uviak Point (Desrosiers et al., 2008; Todisco & Bhiry, 2008b, a; Todisco & Monchot, 2008; Todisco et al., 2009; Aubé-Michaud, 2013; Cencig, 2013; Pharand, 2013; Couture et al., 2015; Couture et al., 2016; Bernier et al., 2017; Couture et al., 2017). Durant notre campagne de terrain de l’été 2015 dans la baie de Kuuvik (côte nord-est de la baie d‘Hudson), un site archéologique thuléen-inuit unique a été inventorié dans une petite vallée périglaciaire située à proximité de l’embouchure estuarienne de la rivière Kuuvik. Ce site est constitué de huit maisons semi-souterraines unifamiliales et six maisons multifamiliales (site Paaliup Qarmangit 1). Ces maisons multifamiliales sont rarement observées au Nunavik, ces dernières étant principalement observées au Labrador et au Groenland (Woollett, 2007).
La baie de Kuuvik (ou Kovik : nom inuktitut qui signifie « lit profond de la rivière »), représente un site culturel de haute importance qui occupe une place centrale dans l’histoire et l’oralité des communautés d’Ivujivik et d’Akulivik (e.g., Kishigami, 1987; Koperqualuk, 2015). De nombreux sites archéologiques y ont été inventoriés. L’un d’entre eux comporte des dizaines d’inuksuit, dont la quasi-totalité est de type tour ; ils sont anormalement hauts en comparaison de ceux retrouvés dans les autres régions du Nunavik (Avataq Cultural Institute, 2016). De nombreuses caches ont également été recensées, la majorité servant au stockage de nourriture, quelques autres étant construites pour entreposer des kayacs. De nombreux ronds de tentes, estimés être associés à une occupation estivale, ont également été identifiés (Avataq Cultural Institute, 2016).
Par ailleurs, en réponse à l’intensification des activités de chasse et de pêche, la communauté d’Akulivik est préoccupée par la construction de nombreuses cabanes (shacks) dans la région. Le développement de ces constructions représente un potentiel danger pour la préservation
1 des sites archéologiques. Leur cartographie a donc été demandée par la communauté d’Akulivik, afin qu’elle puisse s’appuyer sur un document de référence lors de l’émission des permis de construire. Greffée à cette demande émanant de la communauté, une recherche archéologique et géoarchéologique a pu être mise en place. Dans le cadre de celle-ci, le travail géoarchéologique de maîtrise présenté ici vise à mieux comprendre le cadre géomorphologique postglaciaire d’un ensemble de structures d’habitats (site Paaliup Qarmangit 1 - JjGj-14), et notamment les processus de formation d’une structure d’habitat hivernale thuléenne-inuit (structure 10). Plus précisément, cette maîtrise traite des aspects taphonomiques d’une maison semi-souterraine unifamiliale en milieu périglaciaire actuel.
II CONTEXTE PHYSIQUE ET OCCUPATIONS HUMAINES La vallée étudiée (61°35’ N, 77°34' O) se situe dans la baie de Kuuvik, sur la côte nord-est de la baie d’Hudson, au nord-ouest du Nunavik, dans la péninsule d’Ungava (Figure 1).
2 Figure 1 : Localisation du site Paaliup Qarmangit 1.
3 1. GÉOMORPHOLOGIE ET QUATERNAIRE Les formes de terrain dans la région d’étude sont essentiellement le résultat de l’activité glaciaire au Wisconsinien ainsi que de la transgression et de la régression marine postglaciaire (Gray & Lauriol, 1985; Gray et al., 1993). Les phénomènes éoliens, cryogéniques et hydrologiques sont les principaux responsables du remaniement et de l’érosion de surface des sédiments. Ainsi, le bassin versant de la rivière Kuuvik est caractérisé par la présence de sédiments glaciomarins à marins, mis en place lors de la déglaciation et d’invasion marines postglaciaire de la mer de Tyrrell. Il comporte de nombreuses moraines de De Geer, qui se sont développées lors du retrait glaciaire, alors que le front glaciaire de l’inlandsis entrait en contact avec les eaux associées à la transgression marine ; des eskers et des kames sont également présents (Lauriol & Gray, 1987).
Le nord de l’Amérique, est demeuré totalement englacé durant le Wisconsinien, depuis l’interglaciaire Sangamonien (stade isotopique 5) jusqu’à l’Holocène (Andrews, 1989). Durant la dernière glaciation, trois phases d’écoulement glaciaire se sont succédé. La première, caractérisée par un écoulement radial à partir du dôme d’Ungava, a généré vers la baie de Kuuvik un écoulement en provenance de l’est/nord-est. La deuxième, associée au centre de dispersion de Payne, a occasionné un écoulement depuis le sud-est. Enfin, la dernière a été générée depuis la ligne de partage glaciaire étant notamment à l’origine d’un écoulement nord-est en direction de la baie de Kuuvik. Cette ligne de partage aurait occupé la même place de 18 à 8,4 ka B.P. Cette dernière phase d’écoulement a laissé une nappe de till généralement mince (moins d’un mètre) et discontinue en périphérie de la péninsule (Daigneault, 2008).
Le retrait des glaces et la transgression marine postglaciaire se produisirent entre 8 et 7 ka B.P. dans la région de la baie de Kuuvik (Daigneault, 2008). La mer de Tyrrell atteignit un maximum de 117 m d’altitude dans ce secteur (Figure 2), occasionnant un remaniement et un délavage du till sur la quasi-totalité de la zone correspondant à l’actuelle baie de Kuuvik. Ces processus furent à l’origine de la formation de plages sableuses littorales, de dépôts marins et glaciomarins de profondeur (dépôts argileux), et de nombreux cordons et champs de blocs. Les plages soulevées permettent de jalonner le relèvement isostatique et la régression marine subséquents. Les datations radiocarbones effectuées sur des coquilles
4 marines retrouvées dans certaines de ces plages soulevées ont permis de réaliser la courbe régionale de relèvement isostatique. Ainsi, Daigneault (2008) a obtenu douze dates à partir de coquilles échantillonnées sur le territoire entre Kuuvik et les îles Digges, près d’Ivuivik (Figure 2 et Figure 3). L’émersion aurait été effectuée à une vitesse d’environ 4 m par siècle entre 7,4 et 6,1 ka B.P. et de 1,2 m par siècle entre 6,1 ka B.P. et aujourd’hui. Depuis la déglaciation, le paysage se modèle essentiellement sous l’influence des processus périglaciaires, tels que la gélifraction, le soulèvement gélival, l’ostiolisation, ou encore la solifluxion. Ces deux derniers processus sont parfois à l’origine de l’oblitération partielle ou totale de certains paléorivages (Daigneault, 2008).
5 Figure 2 : Altitude maximale et extension des mers postglaciaires et des plans d’eau glaciolacustres du nord de la péninsule d’Ungava (d’après Daigneault (2008)).
6 Hiatella sp. datée dans la vallée d’étude
Figure 3 : Courbe d’émersion de la région Baie de Kuuvik – îles Digges établie à partir de la dation de coquilles marines (âges conventionnels) 1 (d’après Daigneault (2008)). Les points rouges se situent dans la baie de Kuuvik. La coquille datée lors de la présente étude a été calibrée.
2. CLIMAT DE LA BAIE DE KUUVIK La baie de Kuuvik est située dans la zone de pergélisol continu (Figure 4). Selon la classification des climats de Köppen, le climat de la région est de type toundra polaire (Daigneault, 2008). Il est caractérisé par des hivers très froids et long alors que les étés sont courts. L’amplitude thermique annuelle est de plus de 30°C, la température moyenne du mois le plus chaud étant de 7,5°C et celle du mois le plus froid étant de -25°C. Selon Houde (1978), la température moyenne annuelle de l’air est de -7,5 °C, et les précipitations annuelles sont d’environ 400 mm, culminants entre les mois d’août et septembre, alors que les côtes sont libres de glace. Entre 50 et 55 % des précipitations annuelles seraient sous forme de neige. L’on compterait annuellement entre 20 et 40 jours sans gel. Enfin, la vitesse moyenne des vents, soufflant principalement depuis l’ouest, est de 20 km/h (Daigneault, 2008).
1 Coordonnées des points (par ordre d’âge décroissant) : 6 (62°08’25’’N ; 77°52’45’’O) ; 12 (62°27’N ; 77°45’O) ; 8 (62°14’58’’N ; 78°00’35’’O) ; 11 (62°33’55’’N ; 77°58’41’’O) ; 4 (61°46’28’’N ; 77°39’01’’O) ; 1 (61°29’14’’N ; 77°29’08’’O) ; 2(61°35’46’’N ; 77°15’00’’O) ; 5 (61°56’06’’N ; 78°00’00’’O) ; 3 (61°43’46’’N ; 77°50’17’’O) ; 7 (62°10’54’’N ; 78°06’56’’O) ; 10 (62°34’38’’N ; 78°05’25’’O) ; 9 (62°00’19’’N ; 78°02’02’’O).
7 Figure 4 : Zones des types de pergélisol pour la péninsule d’Ungava (d'après Lauriol & Gray, 1987; modifiée par Gagnon, 2011). Le point rouge désigne l’emplacement de la vallée étudiée.
3. OCCUPATION HUMAINE La première mention dans la littérature des sites archéologiques de la Baie de Kuuvik remonte aux années 1920 (Manning, 1946, 1948). L’absence de poste de traite dans cette région et l’importante distance qui la sépare de la communauté la plus proche (à 80 km d’Akulivik) explique probablement le manque de recherches archéologiques dont elle a fait l’objet (Avataq Cultural Institute, 2016). Lors de notre campagne de terrain menée durant l’été 2015 dans la baie de Kuuvik, 839 structures archéologiques (e.g., caches, inuksuit, ronds de tentes, structure légèrement creusées) ont été inventoriées dans 51 sites situés sur les côtes et sur les îles de la baie (Avataq Cultural Institute, 2016).
La vallée étudiée se situe proche de l’embouchure estuarienne de la rivière Kuuvik. Chacune des deux crêtes la délimitant a fait l’objet d’occupations humaines. Sur la crête ouest, se trouvent une dizaine de structures de tentes, caches et inuksuit. En outre, un aménagement axial probablement dorsétien a été identifié dans le fond de la vallée, dans une plage soulevée
8 sableuse (plage soulevée 1 ; cf. infra). Une occupation humaine plus marquée a été observée sur la crête est. Une quinzaine de structures de caches sont présentes dans les champs de blocs délavés de la partie supérieure de la crête. En outre, une vingtaine de structures a été enregistrée dans le secteur Nord de cette crête, à une altitude de 19 ± 3 m. Ce site a été dénommé Paaliup Qarmangit 1 (Figure 5). Sur ce site, une dizaine de maisons semi- souterraines sont présentes ; elles sont associées à des occupations thuléennes-inuit, dont plusieurs grandes maisons multifamiliales, les autres étant des habitations unifamiliales de taille plus modeste (Figure 5). De nombreuses structures de tentes et caches ont également été observées. De concert avec l’archéologue P.M. Desrosiers (Institut Culturel Avataq), l’une des maisons unifamiliales (structure 10), au tunnel d’entrée orienté vers l’ouest et la vallée en contrebas, a été retenue pour faire l’objet d’études plus approfondies (Figure 5, Figure 6, Figure 7).
9 Figure 5 : Localisation des structures archéologiques inventoriées dans la vallée étudiée (A) et cartes du site Paaliup Qarmangit 1 (B) et de la structure 10 (C). La carte de la structure 10 montre l’emplacement des sondages intra-sites (I-1 à I-12) et péri-sites (P-1 à P-4). Le terme « intra-site » réfère aux sondages réalisés à l’intérieur de la structure et à proximité immédiate. Le terme « péri-site » réfère aux sondages effectués plus loin en aval de la structure et qui pourraient avoir été affectés directement ou indirectement par l’activité humaine, ce qui les distingue des sondages extra-sites, situés loin du site Paaliup Qarmangit 1 et éloignés des sites archéologiques.
10 Figure 6 : Maison unifamiliale, structure 10, vue vers l’ouest/sud-ouest, site Paaliup Qarmangit 1.
11 Figure 7 : Vue de la vallée étudiée vers l’ouest depuis la structure 10. La localisation de la structure permet une vue d’ensemble sur la vallée, au relief peu marqué, et la rivière Kuuvik. III LES ÉTABLISSEMENTS HUMAINS AU NUNAVIK L’établissement humain en Arctique de l’Est fut tardif par rapport au reste de l’Amérique en raison du recouvrement de la région par les inlandsis Laurentidien, Innuitien et Groenlandais jusqu’à la fin de la glaciation du Wisconsinien (Andrews, 1989; Desrosiers et al., 2008). Suite à la transgression marine, le retrait des mers postglaciaires durant l’Holocène a libéré de nouvelles terres qui sont devenues habitables plusieurs siècles plus tard. Les premières traces de présence humaine sont attestées vers 4500 B.P. dans le Haut arctique, au Nunavut et au Groenland (Figure 8) (Desrosiers et al., 2008). Le Paléoesquimau correspond au regroupement d’un ensemble de cultures anciennes de l’Arctique de l’Est, le Prédorsétien et le Dorsétien étant les deux manifestations culturelles paléoesquimaudes présentes au Nunavik. Le Néoesquimau succède à ces cultures, et ne désigne, quant à lui, qu’une seule culture, le Thuléen et leurs descendants immédiats, les Inuit (Desrosiers & Gendron, 2015).
12 Figure 8 : Principales différentiations chronoculturelles de l’Arctique nord-américain et du Groenland (Desrosiers & Gendron, 2015).
Selon la théorie généralement acceptée, le peuplement initial de l’Arctique correspond à l’établissement des Paléoesquimaux qui, issus de la région de la Sibérie orientale, se sont implantés sur les côtes de l’Alaska avant de migrer d’ouest en est dans l’Arctique, de l’Alaska jusqu’au Groenland vers 4500 B.P. (Desrosiers & Gendron, 2015). Les Néoesquimaux se seraient développés selon le même modèle, établis dans ces mêmes régions côtières occidentales avant de migrer vers l’est de l’Arctique, il y a environ huit cents ans, remplaçant les populations paléoesquimaudes, avec une discontinuité génétique (Raghavan et al., 2014).
Le Nunavik fit ainsi l’objet d’occupations prédorsétiennes à partir de 2000 B.C., les Dorsétiens s’implantant sur le territoire à partir de 100 B.C. Puis les Thuléens-Inuit leur succédèrent à partir de 1200 A.D (Desrosiers & Gendron, 2015). Plusieurs études récentes ont été effectuées sur des sites archéologiques situés dans la région de Salluit (Desrosiers et al., 2008; Todisco & Bhiry,
13 2008b, a; Todisco & Monchot, 2008; Todisco et al., 2009; Houmard, 2011), d’Inukjuak (Desrosiers et al., 2010; Lemieux et al., 2011), d’Ivujivik (Aubé-Michaud, 2013; Pharand, 2013), de Kangiqsujuaq (Cencig, 2013; Bernier et al., 2017) et de Quaqtaq (Bhiry et al., 2016). Ces études ont notamment permis de mieux comprendre 1) les contextes bio-physiques et géoarchéologiques des sites, 2) les dynamiques d’implantation des populations successives sur le territoire, et 3) pour certaines, les modalités d’évolution culturelle. Elles ont ainsi mis en évidence que les groupes humains sont étroitement dépendants des conditions environnementales et des contraintes de vie, tout en possédant des capacités d’adaptation et des stratégies de subsistance adaptées au milieu.
Par ailleurs, les études réalisées sur l’impact de Petit Âge glaciaire (1450 – 1850 A.D.) sur la culture thuléenne-inuit ne permettent pas, à ce jour, de déterminer si les changements environnementaux, dont le climat, ont impacté les modes de subsistance thuléens-inuit (Woollett, 2007; Lemieux et al., 2011; Cencig, 2013; Gennaretti et al., 2014; Couture et al., 2015; Couture et al., 2016; Couture et al., 2017).
Il est ainsi généralement considéré que les Thuléens-Inuit, une fois implantés en Arctique de l’Est, se sont orientés vers l’exploitation de ressources marines principalement, et terrestres secondairement, ceci se traduisant par une occupation saisonnière du territoire (Woollett, 2003).
La régionalisation de la culture thuléenne-inuit s’observe à travers l’ensemble de l’Arctique de l’Est à partir du XVIIe siècle, se traduisant par une régionalisation du matériel culturel, des technologies, et des modes d’occupation et d’exploitation du territoire (Woollett, 2007). Malgré une grande diversité qui s’est progressivement mise en place dans les modes de subsistance, il a été observé que la chasse au phoque et au caribou est demeurée un pilier central (Henshaw, 2003). Ces changements culturels ont pendant longtemps été attribués à des facteurs environnementaux et notamment aux fluctuations des conditions climatiques (Woollett, 2007). Les recherches de ces dernières décennies se sont penchées sur les facteurs sociaux, économiques et historiques qui auraient impacté le développement des cultures inuit lors des contacts avec les Euro-Canadiens (Woollett, 2007). Il est ainsi considéré que les Thuléens-Inuit du Nunavik auraient connu plus tardivement que le Labrador une influence européenne sur leurs modes de subsistance et d’occupation territoriale (Labrèche, 2003; Woollett, 2003).
14 L’un des changements majeurs chez les Thuléens-Inuit du Labrador et du Groenland s’observe aux XVIIe-XVIIIe siècles dans la structure de l’habitat, avec l’apparition de grandes maisons « communautaires » multifamiliales semi-souterraines (Woollett, 2007). Les hypothèses les plus discutées pour expliquer leur apparition sont celles postulant que leur développement était une réponse adaptative face aux détériorations environnementales du XVIIe siècle, et celles selon lesquelles ces maisons sont le fruit de processus sociaux facilitant l’accumulation de richesses et de prestige encouragés par les contacts avec les Européens et le commerce (Schledermann, 1976b, a; Jordan, 1978). Suite à leurs analyses sur les sites d’Hamilton Inlet et d’Okak Bay, au Labrador, Kaplan et Woollett (2000) associent l’arrivée de ce nouveau type de maisons avec certains phénomènes sociaux, tels la hiérarchisation sociale et l’augmentation de la production économique en vue de générer des surplus.
Les Inuit du Nunavik auraient eu une subsistance essentiellement basée sur l’exploitation des ressources marines avec des incursions saisonnières à l’intérieur des terres (Labrèche, 2003). L’utilisation de l’igloo serait devenue plus généralisée pendant le Petit Âge glaciaire, habitat temporaire permettant une plus grande mobilité pour collecter les ressources alimentaires (Schledermann, 1976a). Toutefois, Lemieux et al. (2011) observent que les campements de maison semi-souterraines hivernales étaient toujours utilisés pendant le Petit Âge glaciaire sur l’île Drayton, suggérant que les conditions environnementales locales permettaient une certaine stabilité en hiver. Les changements environnementaux du Petit Âge glaciaire, par leur influence sur d’autres facteurs écologiques tels que la disponibilité en ressources alimentaires (dont la biomasse animale) et matériaux de construction, auraient ainsi été l’un des facteurs à l’origine des changements observés dans l’habitat thuléen-inuit du Nunavik tels que l’utilisation de l’iglous. Des études approfondies, sur une plus petite échelle géographique notamment, sont encore nécessaires pour discerner davantage l’importance respective des causes anthropiques et environnementales dans l’évolution culturelle thuléenne-inuit (Lemieux et al., 2011).
La réutilisation des sites paléoesquimaux par les Thuléens-Inuit a été fréquemment documentée tant au Nunavik que dans l’Arctique de l’Est en général (Plumet, 1982, 1989; Park, 1993, 2000; Labrèche, 2003; Ryan, 2003a, b; Lemieux et al., 2011). Cette perduration dans l’occupation de mêmes sites sur une longue temporalité met en évidence le caractère central et stratégique que
15 revêtent ces lieux dans les systèmes d’implantation. En effet, ces lieux d’implantation stratégiques répondent systématiquement à certaines caractéristiques telles que : la disponibilité et l’accessibilité aux ressources alimentaires, qu’elles soient marines ou terrestres, la disponibilité des ressources hydriques, lithiques et des matériaux de construction (tourbe), l’existence de plages soulevées sableuses habitables (drainante, aisée à pelleter), un point de vue permettant de dominer une vallée ou une portion littorale (large panorama), ou encore la protection des sites face aux vents dominants (Plumet, 1989; Labrèche, 2003; Lemieux et al., 2011; Moody & Hodgetts, 2013). Aubé- Michaud (2013) a aussi mis en évidence l’importance du contexte géomorphologique dans le choix des lieux d’implantation.
Les études révèlent aussi que les polynies représentaient des lieux d’implantation hivernale de choix (e.g., Henshaw, 2003). Les polynies sont des espaces de mer libre dans la glace de mer, pouvant se former par fragmentation de la banquise sous l’effet des vents et des courants. Elles représentent donc des lieux d’établissement privilégiés des morses et des colonies de phoques annelés et barbus, assurant d’abondantes ressources alimentaires, prévisibles d’une année à l’autre dans le cas des polynies récurrentes (Henshaw, 2003; Lemieux, 2009).
La découverte, en juillet 2015, de maisons multifamiliales et la densité de structures au site Paaliup Qarmangit 1 (JjGj-14) nous ont incité à étudier une des maisons unifamiliales qui leur étaient associées comme première approche de ce site. D’après les membres de la communauté d’Akulivik qui étaient avec nous sur le terrain, une polynie se situant près de la vallée étudiée est régulièrement utilisée pour la chasse pendant l’hiver.
IV LA NÉCESSITÉ D’ÉTUDES GÉOARCHÉOLOGIQUES ET TAPHONOMIQUES EN MILIEU
PÉRIGLACIAIRE ACTUEL De nombreux processus taphonomiques et post-dépositionnels indépendant des activités humaines peuvent affecter l’intégrité d’un site archéologique. Ces processus peuvent occasionner des modifications sur les configurations et l’organisation spatiales des restes archéologiques pendant et après leur déposition (Rick, 1976; Bowers et al., 1983; Schick, 1986; Schick, 1987; Dibble et al., 1997; Vallin et al., 2001; Bertran et al., 2005; Bertran et al., 2006; Bertran et al., 2012; Bertran et al., 2017). Identifier ces processus et en cerner l’action et l’efficience est donc nécessaire à l’étude des sites archéologiques (Thiébaut et al., 2010). La définition de la taphonomie fait encore
16 l’objet de débats et discussions au sein de la communauté scientifique. Cette recherche considère l’approche taphonomique, selon une définition large, comme l’ensemble des méthodes analytiques permettant d’identifier et de caractériser les différents phénomènes et agents qui interviennent lors de la formation des accumulations des vestiges culturels (e.g., artéfacts, écofacts) (Thiébaut et al., 2010), en la considérant, dans notre cas, à l’échelle de la structure archéologique.
Les études taphonomiques en milieu périglaciaire actuel sont peu nombreuses (Todisco et al., 2009) et sont fréquemment issues d’approches expérimentales menées sur quelques années (Lenoble et al., 2008; Todisco et al., 2009; Bertran et al., 2015). Ces résultats expérimentaux sont rarement applicables aux sites archéologiques, ou du moins ne suffisent pas à eux-seuls, de par la durée très courte des expériences au regard de celle mise en jeu dans la formation des sites archéologiques (Lenoble et al., 2008). L’études des processus de formation des sites archéologiques dans l’Arctique permet (1) de mettre en place une nouvelle approche pour étudier les processus de formation des sites en milieux périglaciaires actuels et fossiles, (2) une approche complémentaire aux autres méthodes analytiques couramment adoptées pour documenter les sites thuléens-inuit (e.g., analyses zooarchéologiques), afin de permettre une meilleure compréhension de ces sites archéologiques. Les mauvaises conditions de préservation (e.g., par enfouissement limité) permettant rarement de procéder à une étude taphonomique des structures d’habitat en contexte périglaciaire actuel, les études taphonomiques se consacrent donc habituellement à l’analyse des artefacts et écofacts mis à jour lors des fouilles (e.g., Todisco et al., 2009).
Ainsi, documenter la taphonomie d’une structure d’habitat d’un site de plein air est pertinente, dans la mesure où ces sites sont particulièrement susceptibles d’être affectés par des processus taphonomiques et post-dépositionnels. Dans cette optique, les approches extra-site et intra-site s’avèrent complémentaires afin de replacer le site dans son contexte environnement local et de documenter les processus naturels et anthropiques de formation du site archéologique.
V PROBLÉMATIQUE, OBJECTIFS ET HYPOTHÈSES La problématique de ce projet de recherche est centrée sur les interrogations suivantes : Quels sont les processus de formation de la maison unifamiliale à l’étude ? Existe-t-il des marqueurs anthropiques géochimiques et micromorphologiques spécifiques en lien avec la taphonomie de la
17 structure ? Y a-t-il eu réutilisation par les Thuléens-Inuit d’un site précédemment occupé par les Dorsétiens ?
1. OBJECTIF PRINCIPAL En combinant les approches extra-sites et intra-sites, les études géoarchéologiques ont pour objectif principal de documenter, dans leur cadre environnemental, les occupations dorsétiennes et thuléennes-inuit du site Paaliup Qarmangit 1.
2. OBJECTIFS SPÉCIFIQUES 1) Documenter le contexte géomorphologique dans lequel ont vécu les occupants dorsétiens et thuléens-inuit des sites de la vallée étudiée, dans un contexte périglaciaire;
2) Identifier les processus de formation anthropiques et naturels (bio-pédologiques, cryogéniques, sédimentaires) d’une maison unifamiliale, et les signatures géochimiques des activités thuléennes-inuit dans les sédiments / sols anthropisés;
3) Documenter les éventuelles réutilisations ou phases de remaniements par les Thuléens-Inuit d’un d’ancien site d’occupation dorsétienne ;
3. HYPOTHÈSES 1) Le site a fait l’objet d’occupations dorsétiennes et thuléennes-inuit ; les Thuléens-Inuit auraient alors occasionné un remaniement des vestiges dorsétiens (anthropoturbation). 2) Le site Paaliup Qarmangit 1 a enregistré à différentes échelles (macroscopiquement et microscopiquement) des processus géomorphologiques et taphonomiques qui témoignent des conditions climatiques qui ont prévalu depuis 2000 ans. 3) Les activités domestiques des Thuléens-Inuit ont eu un impact durable sur la chimie des sols de la maison semi-souterraine qui se traduit par des enrichissements et/ou appauvrissements élémentaires.
VI MÉTHODOLOGIE La géoarchéologie est une discipline qui consiste en l’utilisation des méthodes issues des sciences de la terre (géographie physique et géologie) afin de traiter des problématiques archéologiques.
18 1. CAMPAGNE DE TERRAIN Les données ont été collectées dans la vallée étudiée durant la campagne de l’été 2015 (10 juillet - 2 août). Au préalable des travaux de terrain, l’interprétation de photographies aériennes de la baie de Kuuvik (échelle de 1/40 000, 1958), obtenues auprès de l’Université du Québec à Trois- Rivières, et l’étude de la carte géologique des dépôts de surface (Daigneault, 1996) ont été réalisées. Les investigations dans la vallée ont été réalisées suivant deux approches, l’une extra-site et l’autre intra-site.
A. Travaux extra-sites a. Relevés topographiques et géomorphologiques L’identification et la description des types de dépôts, des formes et des processus périglaciaires caractérisant la vallée ont été réalisées. Des relevés de points GPS (GPSMAP 78 Garmin) permettant de délimiter la vallée et les grands ensembles la constituant ont mené à la réalisation d’une carte géomorphologique. Pour ce faire, ont été identifiés : 1) des zones d’affleurement rocheux précambrien avec placage de sable et/ou de matière organique, 2) des champs de blocs (éléments clastiques > 25 cm de diamètre) avec ou sans sable et placage de matière organique, 3) des plages soulevées sableuses partiellement végétalisées et en voie d’érosion, notamment par le ruissellement. Des secteurs présentant des dynamiques particulières ont également été relevés : 1) les zones à solifluxion active, 2) les zones hydromorphes (e.g., étangs, tourbières), y compris au sein des plages soulevées sableuses, 3) les zones de déflation et les zones de solifluxion au sein des plages soulevées sableuses, 4) les principaux ruisseaux et étangs au sein des zones hydromorphes de la vallée. Chacun de ces ensembles a été photographié. Le trait de côte a été défini par la limite des marées hautes moyennes. L’altitude de chaque point a été relevée.
b. Stratigraphie et échantillonnage extra-sites La stratigraphie a pour objectif d’étudier la succession et l’agencement géométrique des unités géologiques ou pédo-sédimentaires en se fondant sur les faciès (Pomerol, 1987). Les faciès sont décrits en tenant compte des critères suivants : la couleur, la texture granulométrique, la structure, les granoclassements, les litages ou stratifications. L’étude stratigraphique a ici pour objectif de documenter la paléogéographie de la vallée étudiée, afin de reconstituer le contexte
19 environnemental dans lequel s’inscrit le site Paaliup Qarmangit 1. Ont été identifiés différents types de dépôts mis en place par des processus sédimentaires. Les lieux d’excavation des coupes a donc fait l’objet d’un choix stratégique afin de rendre compte de la structure des principaux ensembles constitutifs de la vallée et de l’agencement de ces ensembles entre eux. Sept coupes stratigraphiques ont été réalisées dans deux des plages soulevées de la vallée (coupes VP1 C1 à VP1 C7). Les unités stratigraphiques de chacune d’entre elles ont été décrites, dessinées et photographiées. De nombreuses coquilles marines ont été observées dans une des plages soulevées, située à une altitude de 19 ± 3 m et fortement affectée par des processus de déflation. Un échantillon de coquilles a été prélevé dans la coupe excavée dans cette plage soulevée (coupe VP1 C7) pour procéder à une datation radiocarbone.
20 B. Travaux intra-sites Douze sondages intra-sites (sondages I-1 à I12) ont été effectués dans la maison semi souterraine (bourrelet périphérique, plateforme de couchage, plancher et tunnel d’entrée) ainsi qu’à proximité immédiate de son entrée. Quatre sondages péri-sites ont été réalisés en amont de la structure, à 25 mètres et plus (sondages P-1 à P-4). Le terme de péri-site est ici introduit pour désigner les sondages qui ont potentiellement pu être affectés, directement ou indirectement, par les activités humaines, de par leur proximité avec le site archéologique. Ils se distinguent ainsi des sept coupes extra-sites effectuées dans le reste de la vallée. Les positions GPS de l’ensemble de ces sondages ont été relevées. Chacune des unités des coupes a fait l’objet de descriptions et schématisations, et a été photographiée.
Des prélèvements à des fins d’analyses macrofossiles, géochimiques (FTIR et ICP-AES) et de datations radiocarbones ont été effectués dans certains de ces sondages. Neuf boîtes de Kubiena ont été prélevées, permettant de recueillir des échantillons non perturbés et orientés, en vue d’analyses micromorphologiques.
Enfin, les positions GPS de l’ensemble des structures du site Paaliup Qarmangit 1 ont été relevées afin de réaliser la carte détaillée du site. La position de nombreux points situés à différentes altitudes a également été relevée, afin de rendre compte de la (micro)topographie (Figure 5).
2. TRAITEMENT DES DONNÉES ET ANALYSES EN LABORATOIRE A. Cartographie Les photographies aériennes existantes de la région ne couvrant pas le site d’étude, une démarche pour l’acquisition de photographies de ce secteur a permis d’obtenir une photographie satellite en couleurs vraies (RVB) d’une résolution spatiale de 50 cm (WorldView 2, 16-Bit, DRA Off). Cette photographie fut prise le 5 août 2015. La carte géomorphologique de la vallée étudiée a été réalisée à l’aide des logiciels Arc GIS (ESRI) et Illustrator (Adobe). Les tracés ont été effectués à partir des relevés GPS effectués sur le terrain puis affinés à l’aide de la photographie satellite en couleur vraies (RVB). En l’absence de carte topographique à haute résolution du site d’étude, une interpolation spatiale (Krigeage) à partir des relevés GPS a permis de tracer des courbes topographiques. Il est à noter que les données d’élévations obtenues à partir du GPS Garmin présentent une incertitude, notamment de par une couverture satellitaire non-optimale de la région
21 d’étude ; à cette incertitude s’ajoute celle inhérente à la méthode géostatistique de krigeage utilisée pour produire les courbes de niveau. Malgré ces incertitudes, les courbes de niveau obtenues rendent bien compte de la morphologie générale de la vallée. Une carte de localisation des sites archéologiques inventoriés dans la vallée a également été produite à l’aide de ces courbes de niveau.
B. Analyses macrofossiles
Au préalable de la datation des échantillons intra-sites, une analyse des macrorestes a été effectuée afin d’identifier les macrorestes pouvant faire l’objet d’une datation 14C.
Le traitement de l’analyse macrofossiles des échantillons intra-sites a été effectuée au laboratoire de paléoécologie terrestre du Centre d’études nordiques, Université Laval. Un sous-échantillon d’un volume de 25 cc ou de 50 cc a été prélevé dans chaque échantillon, dépendamment du volume initial de l’échantillon. Lorsque cela s’est avéré nécessaire (matériel très décomposé, compact), le sous-échantillon a été porté à ébullition pendant 5 minutes dans une solution de 100 ml d’eau distillée et de KOH, afin de défloculer les agrégats de matière organique. Les sous-échantillons ont par la suite été tamisés, à l’aide d’un faible jet d’eau, dans une série de tamis de différentes tailles (425 µm, 250 µm, 125 µm). Les fractions tamisées ont été mises dans des piluliers désinfectés remplis d’eau distillée et conservées au réfrigérateur, dans le noir et à une température moyenne de 4°C. Elles ont par la suite été observées à l’aide d’une loupe binoculaire (grossissement de 8X à 40X).
C. Datations 14C Les analyses de macrorestes ont mis en évidence le caractère très décomposé de la matière organique. Elles ont aussi permis l’identification et le prélèvement de certains macrofossiles (parties aériennes : e.g., graines, tiges) suffisamment abondants dans l’échantillon pour procéder à une datation 14C (tiges et feuilles de sphaignes et graines d’Empetrum Nigrum). Des fragments de charbon et d’os relevés lors de la fouille ont également été datés. Les échantillons ont subi un prétraitement au laboratoire de Radiochronologie de l’Université Laval afin d’en extraire le 14C. La mesure ICP-MS a été effectuée au Keck Carbon Cycle AMS Facility, département de sciences
22 des systèmes terrestres, Université de Californie. Les dates terrestres obtenues ont été calibrées à l’aide de la courbe IntCal 13 du logiciel Calib 7.10.
Par ailleurs, une coquille de Hiatella sp. de l’échantillon de coquilles marines prélevée dans les dépôts littoraux de la coupe VP1 C7 a été datée. Comme pour les macrofossiles datés, la coquille a subi un prétraitement au laboratoire de Radiochronologie de l’Université Laval afin d’en extraire le 14C. La mesure ICP-AES a été effectuée au Keck Carbon Cycle AMS Facility, département de sciences des systèmes terrestres, Université de Californie. Cette date marine a été calibrée à l’aide de la courbe Marine 13 du logiciel Calib 7.10. Un ΔR de 263 ± 48 ans, calculé par Ross et al. (2012) pour la région du canal de Foxe et du nord de la baie d’Hudson, a été utilisé.
D. Analyses micromorphologiques Les analyses micromorphologiques ont permis d’étudier la composition, la microstructure/texture, l’origine et le remaniement des sédiments par les processus naturels (bio-pédologiques, cryogéniques) et/ou anthropiques (Bullock, 1985; Stoops et al., 2010). En d’autres termes, replacées dans leur contexte macroscopique, elles ont rendu possible l’observation et l’interprétation des micro-organisations pédo-sédimentaires et l’identification de microtraits d’origine anthropique. Des échantillons de sol non perturbés et orientés ont été prélevés au moyen de boîtes de Kubiena (Figure 9).
23 Figure 9 : Prélèvement d’une boîte de Kubiena.
Les échantillons prélevés ont été imprégnés et durcis à la résine époxy, puis découpés en lames minces de 30 µm d’épaisseur au laboratoire ARKEOLAM du Centre d’études nordiques (CEN) et du Groupe de recherche en archéométrie de l’Université Laval. Ces lames ont par la suite été examinées au microscope polarisant (Leica DM 4500P), à un grossissement allant de 10 à 400X, au laboratoire de microscopie et de palynologie du CEN de l’Université Laval de Québec. L’observation en lumière polarisée non analysée (LPNA) et en lumière polarisée analysée (LPA) a ainsi permis l’étude des propriétés optiques des corps cristallins et la reconnaissance des éléments amorphes.
E. Analyses géochimiques a. Analyses FTIR Des analyses Fourier Transform InfraRed spectroscopy (FTIR ) ont été effectuées afin d’identifier d’éventuels composés organiques d’origine anthropique présents dans le sol. Ces analyses présentent un vaste potentiel de mise en application, incluant l’identification de groupes fonctionnels de molécules, la définition de structures atomique et la caractérisation de matériaux
24 dont la nature n’est pas connue sur le terrain (Butler & Dawson, 2013). Les analyses FTIR ont été effectuées dans l’optique de cette dernière approche, afin d’identifier d’éventuels composantes anthropiques dans le sol (cendres, charbon, graisse/graisse brûlée, os etc.).
Les analyses FTIR ont été réalisées au Centre de Recherche sur les Matériaux Avancés de la faculté de Sciences et Génie de l’Université Laval. Les échantillons ont été séchés puis broyés finement et homogénéisés. Un sous-échantillon de 1mg a été prélevé et mis dans un mortier avec 100 mg de bromure de potassium (KBr). Le mélange est homogénéisé à l’aide d’un pilon et la poudre obtenue est répartie en une fine couche sur le moule à pastiller. Les pastilles ainsi constituées sont par la suite pressées dans une presse hydraulique à environ 10 000 livres pendant deux minutes. Les pastilles sont ensuite insérées dans un spectromètre. L’acquisition des données est effectuée à l’aide du spectromètre Nicolet is50 de Thermo Fisher.
b. Analyses ICP-AES Les teneurs de vingt-six éléments ont été mesurées à l’aide d’un spectromètre d’émission atomique au plasma afin d’identifier un éventuel enrichissement ou appauvrissement en certains éléments (majeurs, mineurs et traces) au sein des échantillons archéologiques.
i. Traitement des échantillons en laboratoire Les analyses ICP-AES (Iductively Coupled Plasma - Atomic Emission Spectroscopy) ont été effectuées au Laboratoire des services communs du Centre Eau, Terre, Environnement de l’Institut National de Recherche Scientifique (INRS) de Québec.
Une perte au feu a été effectuée sur un sous-échantillon de 0.5g indépendamment des autres mesures pour déterminer la teneur en matière organique (teneur globale en carbone, en hydrogène, en oxygène et en azote) de l’échantillon. Les creusets en porcelaine contenant les sous-échantillons ont été soumis à une cuisson de 1100°C pendant une heure.
Les échantillons ont été séchés puis broyés finement et homogénéisés. Un sous-échantillon de 1 g. a ensuite été prélevé de chaque échantillon. Les sous-échantillons ont ensuite été mis en solution par fusion alcaline. Les mesures effectuées (exprimées en %) lors de l’analyse ICP-AES ne prennent pas en compte le pourcentage de carbone, d’hydrogène, d’oxygène et d’azote contenus dans l’échantillon. Un facteur de correction a donc par la suite été calculé à partir des résultats de
25 la perte au feu afin d’intégrer les teneurs en matière organique dans le pourcentage total exprimé pour chaque élément par échantillon. Le facteur de correction est le suivant :
1 푓 = 푐 1 − 푃퐴퐹
La valeur 1 au dénominateur est due au fait que le poids du sous-échantillon analysé est de gramme. L’incertitude du spectromètre est de 2 à 3% de la valeur mesurée.
ii. Traitement des données et analyses statistiques Les données ICP-AES comportaient donc le taux de matière organique pour chacun des échantillons analysés. Afin de permettre une comparaison de la teneur en éléments majeurs, en éléments mineurs et en éléments traces entre les échantillons, une normalisation par la teneur en matière organique a été effectuée pour chacune des teneurs en éléments chimiques ; ceci afin que la teneur élémentaire, exprimée en pourcentage, ne dépende plus du taux de matière organique. Les données ICP-AES ont par la suite fait l’objet de plusieurs traitements statistiques afin de rendre compte d’un éventuel enrichissement/appauvrissement élémentaire. Les éléments dont les concentrations étaient trop fréquemment en dessous des seuils de détection n’ont pas été pris en compte dans ces traitements (Table 1). Ainsi, les éléments As, Cd, Mo et Pb ont été écartés.
26 Table 1: Limite de détections des éléments lors de l'analyse ICP-AES (Stéphane Prémont, communication personnelle, 2017).
ÉLEMENT UNITE LIMITE DE DETECTION Al2O3 % 0,001
CaO % 0,0002 Fe2O3 % 0,0002 K2O % 0,016 MgO % 0,0001 MnO % 0,00003 Na2O % 0,022 P2O5 % 0,005 ÉLEMENTS MAJEURS ÉLEMENTS SiO2 % 0,004 TiO2 % 0,0001 S % 0,003 Ba ppm 0,26
Sr ppm 0,07 MINEURS ÉLEMENTS ÉLEMENTS As ppm 13 Cd ppm 1,6 Co ppm 3 Cr ppm 1,8
Cu ppm 1,8 La ppm 1,1 Mo ppm 4 Ni ppm 6 Pb ppm 18 Sc ppm 0,18 ÉLEMENTS TRACES ÉLEMENTS V ppm 2,6 Y ppm 0,4 Zn ppm 0,8 Zr ppm 0,8
La première approche statistique est fondée sur 1) la comparaison des distribution intra-sites et extra-sites à travers l’utilisation de boîtes à moustaches et 2) le calcul des facteurs d’enrichissement, suivant les méthodes de Entwistle et al. (1998) et Butler (2011).
27 Un test de Student a été effectué afin d’estimer la différence entre les échantillons intra-sites et les échantillons de contrôle pour chacun des vingt-trois éléments étudiés. Ce test paramétrique implique que le modèle théorique des observations repose sur des lois faisant partie d’une famille de distributions dont les valeurs sont déterminées par un nombre fini de paramètres (Desbois, 2004). Ainsi, le test de Student repose sur l’acceptation que la distribution des données testées suit une loi normale. La validité de ce prérequis a donc été vérifiée à l’aide d’un test de Kolmogorov Smirnov (K-S). En outre, le test de Student postule aussi l’homogénéité des variances des distributions testées. Un test de Fisher (paramétrique) a donc été également effectué après le test K-S, afin de vérifier l’homogénéité des variances. Une fois ces deux tests effectués, le test de Student a été effectué lorsque les conclusions des deux tests précédents le permettaient, i.e. que les hypothèses de normalité des distribution et d’homogénéité des variance étaient validées. Les tests K-S, de Fisher et de Student ont été réalisés à l’aide des logiciels Matlab 2016 et Excel 2016.
Par la suite, les diagrammes en boîte représentant les distributions des échantillons intra-sites et de contrôle ont été produits et analysés afin d’examiner la dispersion de chaque population d’échantillons. Pour compléter cette première approche statistique, les facteurs d’enrichissement intra-sites ont été réalisés pour chacun des échantillons, pour chacun des éléments, suivant l’approche adoptée par Entwistle et al. (1998) et reprise par Butler (2011). Des intervalles de deux écarts-types ont été retenus comme seuils minimaux d’enrichissement/appauvrissement significatifs. Les diagrammes en boîte et les facteurs d’enrichissement ont été produits à l’aide du logiciel Excel 2016.
La seconde approche statistique a été adoptée pour vérifier et soutenir la première. Des analyses multivariées en composantes principales (ACP) ont ensuite été effectuées dans le logiciel XLstat 2018 afin d’identifier une éventuelle corrélation dans les variations de la concentration des différents éléments. Cette approche présente l’avantage de permettre, le cas échéant, une confrontation de multiples données quantitatives. L’ACP consiste à remplacer les variables qui seraient fortement corrélées à une même composante principale par cette composante principale. Cette approche permet ainsi de déterminer, parmi l’ensemble des variables (les concentrations élémentaires), lesquelles présenteraient les mêmes tendances. En d’autres termes, une importante concentration d’un de ces éléments dans un échantillon serait associée à une (plus)
28 importante concentration des autres éléments. La composante principale rendrait donc compte à elle seule des distributions de tous les éléments qui lui sont fortement corrélés (Shennan, 1988, p.264). Afin de montrer l’importance des choix des méthodes statistiques utilisées, des ACP de corrélation et de covariance ont été effectuées.
Afin de déterminer quelles composantes principales sont nécessaires et suffisantes pour simplifier les données en conservant une représentativité statistiquement valide, les composantes principales présentant une valeur propre supérieure à 1,0 ont été retenues pour l’ACP de corrélation (critère de Kaiser) (Shennan, 1988, p.264). La règle de Cattell a été appliquée pour l’ACP de covariance. À partir de la représentation graphique des valeurs propres en fonction des numéros de composantes principales, cette règle consiste à ne retenir que les composantes principales situées avant le changement abrupte de la pente de la courbe (appelée rupture du coude). Pour les deux ACP, l’étude des cosinus carrés entre les variables et les composantes principales retenues a ensuite permis de documenter plus en détail les relations de corrélation entre les éléments chimiques et ces composantes principales. L’analyse des « biplots » a ensuite été effectuée, afin d’identifier les échantillons qui pourraient se distinguer visuellement des autres. Ces échantillons présenteraient un enrichissement ou appauvrissement élémentaire, fortement corrélé à une composante principale. Une comparaison des résultats obtenus avec les résultats de la première approche (diagrammes en boîte et facteurs d’enrichissement) a été effectuée afin de valider et confronter les résultats.
Afin de vérifier la validité des résultats obtenus par l’ACP, des classifications ascendantes hiérarchiques (CAH) ont été effectuées à l’aide du logiciel XLstat 2018. Elles visent à vérifier si les échantillons qui, visuellement, semblaient se distinguer des autres suivant l’ACP sont également estimés être différents des autres par ces méthodes de groupement plus objectives. Une CAH de dissimilarité a été calculé en utilisant la distance euclidienne (proximité) et la méthode d’agrégation de Ward. Quatre CAH de similarités ont été calculés en utilisant les coefficients de Pearson, Spearman, Gowser et Kendal (proximité) et la méthode d’agrégation du lien moyen.
c. Analyses Raman La spectroscopie Raman a été utilisée dans le but de préciser la nature de certaines particules organiques observées lors de l’analyse micromorphologique. Par l’entremise de cette analyse, nous
29 avons mis en évidence la présence dans les lames KM7.1 et KM7.2 de particules noires opaques amorphes tant en LPA qu’en LPNA, caractérisés par une structure vésiculaire. Des analyses de spectrométrie Raman ont été effectuées afin de qualifier l’origine de ces traits micromorphologiques. L’utilisation de l’analyse Raman afin de d’identifier des composés carbonés noirs (notamment des pigments) est récente (e.g., Coccato et al., 2015). Les études menées jusqu’à présent, encore peu nombreuses, ne permettent que difficilement d’interpréter les spectres en termes de caractérisation des composés (Coccato et al., 2015). L’analyse visait ainsi à contribuer à montrer la complémentarité de cette méthode avec l’analyse micromorphologique pour l’interprétation des lames minces, notamment en contexte archéologique.
Les analyses Raman ont été effectuées au Centre de recherche sur les matériaux avancés (CERMA) de l’Université Laval. Les lames minces étant non couvertes, l’analyse Raman a pu être effectuée directement sur les lames minces présentant les particules à analyser. L’analyse Raman a été effectuée avec le spectromètre Raman HR-800 de Horiba Jobin-Yvon.
d. Analyses CNS Des analyses CNS ont été réalisées afin de calculer le ratio C/N des échantillons de sols analysés par la spectrométrie FTIR et ICP-AES et identifier un enrichissement en azote des sols (Brady & Weil, 2008, p. 504, 545-547). Les analyses ont été effectuées au Laboratoire de chimie analytique du département des sciences du bois et de la forêt de l’Université Laval. Suite à la combustion en fournaise à 1450°C des échantillons, les gaz de combustions ont été recueillis et acheminés vers les détecteurs pour leur dosage respectif. L’appareil utilisé pour le dosage CNS est un Leco Trumac CNS. Le ratio C/N a par la suite été calculé à partir des données CNS à l’aide du logiciel Excel 2016.
30 VII STRUCTURE DU MÉMOIRE Cette maîtrise est structurée sous forme de deux articles rédigés en anglais qui seront prochainement soumis pour publication. L’auteur du mémoire est premier auteur de chaque article.
Le premier chapitre correspondant au premier article répond aux objectifs 1, 2 et 3 du mémoire. Il traite des résultats des analyses géomorphologiques, stratigraphiques, macrofossiles, micromorphologiques et des datations radiocarbones. Il présente l’étude des processus taphonomiques de formation de la maison semi-souterraine étudiée. À travers les approches intra- site et extra-site, nous avons démontré l’importance de replacer le site dans son contexte local afin d’appréhender correctement les processus étudiés et confirmé la pertinence d’adopter une approche multidisciplinaire géoarchéologique comme première étude d’un site archéologique. Ce chapitre sera soumis à la revue Geoarchaeology, An International Journal.
Le second article (deuxième chapitre) est consacré à l’approche géochimique des échantillons intra- sites. Il réponde à l’objectif 2 du mémoire. Des analyses géochimiques (FTIR et ICP-AES) des sols anthropisés des sites archéologiques nordiques ont été utilisées afin de documenter les marqueurs des activités anthropiques. Cette approche, couramment adoptée sur les sites archéologiques des régions tropicales et tempérées, n’a que très peu été utilisée sur des sites archéologiques en contexte périglaciaire actuels (Butler & Dawson, 2013; Brancier, 2016; Butler et al., 2018). Ce chapitre met notamment en évidence l’importance de documenter les processus taphonomiques post- dépositionnels cryo-pédologiques qui peuvent affecter les signatures anthropiques. Cet article sera soumis à la revue Journal of Archaeological Sciences.
La conclusion générale du mémoire permet d’articuler les principaux éléments, complémentaires, qui ressortent de cette étude multidisciplinaire, effectuée selon une approche multiscalaire. Elle ouvre également sur des perspectives de recherche futures en géoarchéologie nordique.
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37 CHAPITRE 1
Paaliup Qarmangit 1 site geoarchaeology: Taphonomy of a Thule- Inuit semi-subterranean dwelling in a periglacial context, northeast Hudson Bay
Heloïse Barbel1, Najat Bhiry1, Dominique Todisco2, Pierre Desrosiers1 and Domonique Marguerie3
1Departement de géographie, and Centre d’études nordiques, Pavillon Abitibi Price, Université Laval, Québec, Canada, G1V 0A6, 2Département de géographie, Université de Rouen, rue Lavoisier, 76821 Mont Saint Aignan, France, 3 Centre de Recherche en Archéologie, Archéosciences et Histoire, Université Rennes 1, avenue du Général Leclerc, 35042 Rennes, France.
38 RÉSUMÉ Une étude géoarchéologique multidisciplinaire a été menée sur le site Paaliup Qarmangit 1 (JjGj-14), situé dans une vallée périglaciaire au Nunavik, Canada. Une étude taphonomique visait à documenter les processus de formation d’une maison hivernale semi-souterraine unifamiliales thuléenne-inuit. Les analyses géomorphologiques et stratigraphiques extra- sites ont permis de reconstituer l’évolution des environnements sédimentaires dans la vallée depuis la dernière glaciation. Le site a fait l’objet d’une occupation dorsétienne après 143- 327 cal A.D. et a par la suite été réutilisé par les Thuléens entre 1317-1413 cal A.D. et 1466- 1642 cal A.D. Le caractère stratégique du lieu d’implantation pourrait expliquer son utilisation par deux cultures successives. Les analyses stratigraphiques, micromorphologiques et macrofossiles intra-sites ont montré la prédominance des processus nivéo-éoliens et de nivations dans la formation de la matrice sédimentaire contenant les restes archéologiques. Les données macrofossiles et les datations radiocarbones montrent l’occurrence de processus de remaniements post-dépositionnels naturels et/ou anthropiques des artefacts dorsétiens.
Mots-clefs : Maison semi-souterraine, habitat thuléen, géoarchéologie, périglaciaire, nivéo- éolien, nivation, Nunavik.
39 ABSTRACT A multidisciplinary geoarchaeological investigation was performed at Paaliup Qarmangit 1 site (JjGj-14), located in a periglacial valley in Nunavik, Canada. A taphonomic approach was carried out to document site formation processes of a single-family semi-subterranean winter Thule-Inuit house. Off-site geomorphological and stratigraphical analyses enabled us to reconstruct the sedimentary environments in the valley since the last glaciation. Valley shoreline sediments deposited during the marine regression were reworked by aeolian, runoff and periglacial processes. The site was first used by Dorset people after 143-327 cal A.D. and then by the Thule-Inuit between 1317-1413 cal A.D. and 1466-1642 cal A.D. Strategic features of the site, such as availability of building material, food, and hydric resources, may explain its use by two different cultures. Intra-site, stratigraphical, micromorphological and macrofossil analyses showed the predominance of niveo-aeolian and nivation processes in the formation of the unit containing archaeological remains. The archaeological record reveals a the action of niveo-aeolian processes throughout both the Medieval Climatic Optimum and the Little Ice Age, likely due to local factors, site location and the bowl-shape of the semi-subterranean house. Macrofossil data and radiocarbon dating have shown post- depositional natural and/or anthropogenic reworking of Dorset artefacts.
Key words: Semi-subterranean house, Thule dwelling, geoarchaeology, periglacial, niveo- aeolian, nivation, Nunavik.
40 I INTRODUCTION Inuit colonized the American Arctic and Greenland during the 13th Century (McGhee, 2000; Friesen & Arnold, 2008; McGhee, 2009; Morrison, 2009). Within a century, they had expanded from their first settlements in Alaska/Bering Strait into the Northeastern American region and then to Greenland (Friesen & Arnold, 2008). The Thule-Inuit were efficient marine mammal hunters, some of them practising large whale hunting (Plumet, 1989; Moody & Hodgetts, 2013; Desrosiers & Gendron, 2015). Following McGhee (1996), subsistence practices enabled them to adopt semi-permanent settlements consisting of communities of semi-subterranean peat houses with roof structures made from tree trunks or whale bones. Studies undertaken in the Northwest Territories suggest that whale hunting was not a common practice for the first Thule-Inuit settlers who hunted more abundant and predictable marine resources such as the ringed seal (Moody & Hodgetts, 2013). On the western coast of Nunavik (northern Québec, Canada), archaeological studies have not revealed any significant whale hunting activities; instead, smaller marine mammals were hunted (Lemieux, Bhiry & Desrosiers, 2011; Bhiry, Marguerie & Lofthouse, 2016). In the Canadian Arctic, winter Thule-Inuit settlements appear to be mainly coastal, especially where polynyas were present. This location favours hunting of sea mammals such as walruses and bearded seals (Henshaw, 2003; Lemieux et al., 2011); (Moody & Hodgetts, 2013). The Thule-Inuit adopted a seasonal economic calendar as a response to the seasonal availability of food resources (Woollett, 1999; Kaplan & Woollett, 2000; Woollett, 2007). Although the seasonal nature of the use of winter semi-subterranean houses is under-explored, the study of this practice would be very relevant for understanding annual residential migration patterns (Foury, 2017).
Modalities of the transition between Dorset and Thule-Inuit periods in the Canadian Arctic are still debated. On the one hand, some authors postulate an overlap between Thule-Inuit and Dorset populations (e.g., McGhee, 2000; Friesen, 2004). Relationships between both populations may have occurred, whether conflictual or not. On the other hand, some conclude that the Dorset people had disappeared prior to the Thule-Inuit arrival (e.g., Park, 1993, 2000; Pinard & Gendron, 2007). The latter hypothesis is supported by recent palaeogenetic studies that show no evidence of genetic admixture (Raghavan, DeGiorgio, Albrechtsen, Moltke, Skoglund, Korneliussen, Grønnow et al., 2014). In any event, the Thule-Inuit use of locations previously occupied by Dorset people has been frequently observed in archaeological sites
41 in Nunavik and, more widely, in the eastern Arctic (Plumet, 1982, 1989; Labrèche, 2003; Ryan, 2003b, a; Lemieux et al., 2011; Bhiry et al., 2016). This diachronic use in commonly explained by the strategic value of the sites (Plumet, 1989; Labrèche, 2003; Lemieux et al., 2011; Moody & Hodgetts, 2013). They were typically located close to sources of building material (e.g. peat) and food resources. At the same time, specific topographic and geomorphological conditions afforded an extensive view of the surrounding area as well as protection against prevailing winds.
Several Thule/Inuit sites have been studied in Nunavik in recent years (Desrosiers, Lofthouse, Bhiry, Lemieux, Monchot, Gendron & Marguerie, 2010; Lemieux et al., 2011; Cencig, 2013; Pharand, 2013; Bhiry et al., 2016; Bernier, Bhiry & Gendron, 2017) using intra- and extra-site approaches. These studies have integrated geomorphological surveys, pollen and macrofossil analyses as well as sedimentological, micromorphological and zooarcheological investigations. The data provide new and relevant insights regarding site formation linked to environmental change and human occupation. In this study, a geoarchaeological approach is adopted in order to highlight the effect of taphonomic processes on archaeological remains, and especially on a Thule semi-subterranean house. Such a study is needed for archeological sites located in a periglacial environment, where post-depositional processes (e.g., freezing-thawing) can cause modifications of the spatial configurations of archaeological remains during and after their deposition (Dibble, Chase, McPherron & Tuffreau, 1997; Vallin, Masson & Caspar, 2001; Bertran, Lenoble, Lacrampe, Brenet, Cretin & Milor, 2005; Bertran, Claud, Detrain, Lenoble, Masson & Vallin, 2006; Bertran, Lenoble, Todisco, Desrosiers & Sørensen, 2012; Bertran, Bordes, Todisco & Vallin, 2017). This study sought to identify such processes and determine their action and extension, which takes precedence over other archaeological approaches (Thiébaut, Coumont & Averbouh, 2010). In this regard, in-site and off-site approaches are complementary and relevant to contextualize the archaeological site and its local environment. They also help to document natural and anthropogenic formation site processes. Taphonomic studies in the active periglacial context are scarce. In Nunavik, a detailed taphonomic study at the Palaeoeskimo Tayara site (northern Québec) documented the impact of solifluction or surface water flow on site formation or spatial patterning (Todisco & Bhiry, 2008b; Todisco, Bhiry & Desrosiers, 2009). Taphonomy studies performed in the active periglacial context
42 typically focus on the taphonomy of archeological artifacts and ecofacts (e.g. spatial redistribution of archaeological remains and integrity of sites) (Todisco et al., 2009) and rarely on archeological dwellings (e.g. collapse and burial processes). This omission is largely due to the poor preservation of dwelling structures at paleolithic sites. Savelle (1984) was the first to perform a study in the present periglacial context to document the taphonomy of an historic Inuit snow dwelling.
Some experimental approaches performed over a short time period have documented the impact of natural processes on archaeological remains (Hilton, 2003; Lenoble, Bertran & Lacrampe, 2008; Bertran, Beauval, Boulogne, Brenet, Chrzavzez, Claud, Costamagno et al., 2009; Bertran et al., 2012; Bertran, Beauval, Boulogne, Brenet, Costamagno, Feuillet, Laroulandie et al., 2015). These experimental results are rarely directly applicable to archaeological sites, especially in active periglacial context, or are at least insufficient, owing in part to the short temporality of these experiences in comparison with the duration involved in archaeological site formation (Lenoble et al., 2008).
The present study deals with the taphonomic investigation of a Thule-Inuit winter dwelling located in northeastern Hudson Bay. The dwelling is well-preserved, but there was a scarcity of artefacts and ecofacts recorded in test pits. This site, identified as Paaliup Qarmangit 1 (JjGj-14), was inventoried during a field survey in collaboration with the Avataq Cultural Institute and members from the Akulivik village during the 2015 summer. According to Inuit partners, a polynya located near the Paalliq 1 Valley is still used by hunters from Akulivik during the winter. Due to the high number of structures (fifteen), their diversity (single and family semi-subterranean houses, caches, etc.) as well as their location, the Paaliup Qarmangit 1 site was selected for detailed geoarchaeological investigations. The main objective of the study was to document the site formation processes of a single family semi- subterranean Thule house located in an active periglacial context. The specific objectives were: 1) to document the paleogeographic context of the valley in which the site is situated, 2) to investigate the re-use of an original Dorset site by the Thule-Inuit and 3) to characterize the burial processes of archaeological remains by natural and/or anthropogenic agents.
43 II STUDY SITE The investigated site is located in the Paalliq area in a small valley on the left bank of the mouth of the Kuuvik River estuary in Kuuvik Bay (Figure 10). The site consists of fifteen semi-subterranean houses of different sizes, each one of which could shelter about five to twenty persons. The Kuuvik Bay lies on Precambrian Narsajuaq terrane and Cap Smith belt rocks (Daigneault, 2008; Baragar, 2015). The Ungava peninsula was covered and scoured by the Laurentian ice sheet during the last glacial period (Daigneault, 2008). Wisconsin glacial activity generated numerous glacially eroded hills and depressions, De Geer moraines, eskers, kames and other till deposits (Gagnon, 2011). In the Kuuvik Bay, the retreat of the ice sheet occurred between ca. 8000 and 7000 B.P., followed by the post-glacial marine transgression of the Tyrell Sea onto the coastline to an altitude of up to about 117 m (Daigneault, 2008). The Tyrell Sea first induced glaciomarine sedimentation of deep-water marine clay. It reworked previous till deposits and generated boulder field formations as well as sandy raised beaches, all of which punctuated the isostatic rebound. Subsequently, aeolian, cryogenic and hydrologic processes reworked post-glacial deposits, partly obliterating the initial configuration of paleo-shorelines (Daigneault, 2008).
Kuuvik Bay lies in the shrub tundra ecozone and is underlain by continuous permafrost (Payette, Garneau, Gauthier & Houle, 2013). The region is characterised by a polar tundra climate with cold winters, short summers and a mean annual air temperature of -7.5°C (Houde, 1978; Daigneault, 2008; Payette et al., 2013). Annual precipitation is about 400 mm, half of which is snow. Monthly precipitation culminates between August and September (Houde, 1978). Westerly winds from the Hudson Bay prevail, with a mean speed of about 20 km/h (Daigneault, 2008).
44 Figure 10: Location of the Paaliup Qarmangit 1 site in Kuuvik Bay, northeast Hudson Bay.
45 Archaeological structures were inventoried on both ridges of the valley (61°35'27.35"N ; 77°34'51.52"O) (Figure 11). On the top of the western ridge, a dozen tent rings, caches, and inuksuit associated with Thule-Inuit occupations were identified, but only a few Dorset artefacts were found. Upstream, a Dorset axial mid-passage feature was found on the raised beach RB1 and was pit-tested. Signs of human occupation are more evident on the eastern ridge of the valley. In addition to fifteen caches found in a boulder field on the top of the ridge, thirty-four archaeological structures were inventoried in the northern area of the eastern ridge. Eighteen of these constitute an archaeological site located in a grassy boulder field in the lower part of the eastern ridge near the estuary shore (Paaliup Qarmangit 2 site). This site includes five shallow semi-subterranean structures associated with Dorset winter houses and nine tent rings associated with Thule/Inuit summer occupations. Five caches and some Dorset artefacts were also recorded. The other fifteen structures were inventoried in an archaeological site located in an upper grassy area near the boulder field used for storage (caches) at an elevation of about 19±3 m. This winter Thule/Inuit site, called Paaliup Qarmangit 1, includes one hunting blind, nine single-family semi-subterranean houses and five multi-family semi-subterranean houses (Figure 11). These five multi- family semi-subterranean houses are one of the rare concentrations of large Thule-Inuit houses in Nunavik. Those large dwellings are more often observed in Labrador and Greenland (Woollett, 2007). This paper presents a geoarcheological study performed on one of the single-family semi-subterranean houses (Structure 10), the tunnel entrance of which is oriented toward the valley (Figure 11 andFigure 12).
46 Figure 11: Location of archaeological structures inventoried in the studied valley (A), maps of the Paaliup Qarmangit 1 site (B) and the studied structure (C). Map of the studied single-family semi-subterranean house shows location of intra-site (I-1 to I-12) and peri-site (P-1 to P-4) test pits. Intra-site test pits refers to test pits excavated inside the house and nearby. The term “peri-site” refers to test pits dug in the vicinity47 of the house which could have been affected directly or indirectly by human activity, distinguishing them from off-site excavations located far from the archaeological sites in the valley.
Figure 12: Single-family semi-subterranean house at the Paaliup Qarmangit 1 site (Structure 10). The dashed line delimits the bed platform and the full line delimits the peripheral wall.
III METHODS Field data were collected in 2015 in the context of an archaeological field survey. Accordingly, one structure was selected at Paaliup Qarmangit 1 site to be sampled in order to have a better idea about the chronology of the site, following off-site, peri-site and on-site approaches. To preserve the integrity of the studied structure, test pits were excavated in small cross sections to collect samples and understand the stratigraphy.
1. OFF-SITE APPROACH Surface deposits, landforms and periglacial processes were identified and described throughout the valley. Seven stratigraphic cross-sections (VP1 C1 - VP1 C7) were excavated in post-glacial deposits, including those in raised beaches, to document the evolution of sedimentary environments. Some test pits were also excavated on the ridges of the valley to determine the thickness of the deposits overlying the bed rock. A Hiatella sp. shell sample was collected in the stratigraphic cross-section VP1 C7 for radiocarbon dating. It was dated using accelerator mass spectrometry (AMS) at CEN’s laboratory and at the Keck Laboratory at the University of California, Irvine (UL-KIU). To correct the marine reservoir effect, this marine age was calibrated using Marin13 calibration curve using Calib 7.10 software (Ross, Utting, Lajeunesse & Kosar, 2012). An offset (ΔR) relative to the model global marine
48 reservoir aged of 263±48 yr was calculated by Ross et al. (2012) for the region of Foxe Channel and northern Hudson Bay. It was thus used to precise the marine dating calibration.
2. IN-SITE APPROACH Twelve in-site test pits (I-1 to I-12) were excavated inside the semi-subterranean house and in proximity to the house. Four peri-site test pits were excavated downstream of the house, at a distance of over 25 m. The deposits found in the peri-site test pits were distinguished from those observed further away in the valley because peri-site sediments may have been directly or indirectly impacted by human activities. Samples for radiocarbon dating and for macrofossil and micromorphological analyses were collected in test pits excavated in the peripheral wall, the bed platform, the floor and the tunnel entrance of the house. Samples were also collected outside of the structure near the tunnel entrance (at a distance of about 2 m), and further away, approximately 20 m downstream of the tunnel entrance. All of the samples were stored at 4°C until processing.
Macrofossil analyses were performed to document the composition of vegetation over time at the site. Analysis of the samples was completed at the Laboratoire de paléoécologie terrestre at the Centre d’études nordiques (CEN), Université Laval. Subsamples of a volume of 25 to 50 cc were collected from each sample, depending on the initial volume. Subsamples were then treated following the protocol outlined by Bhiry and Filion (2001). Deflocculation using boiling KOH solution was performed on samples rich in highly decomposed organic matter. Subsamples were then sieved under water using 425 µm, 250 µm and 125 µm sieves. Sieved fractions were conserved at 4°C in disinfected bottles with distilled water. They were then analyzed using a binocular magnifier (8x to 40x magnification). Macrofossils were identified by comparing the morphological characteristics of plant parts (e.g., seeds, leaves) with specimens from the CEN reference collection. For each subsample, the number of complete macro-remains was counted.
During macrofossil analysis, aerial plant remains such as leaves and twigs of Sphagnum and seeds of Empetrum nigrum were selected for dating. Subsamples from I-3, I-4, I-5, I-7 and P-1 test pits (one for each test pit) were dated using accelerator mass spectrometry (AMS) at CEN’s laboratory and at the Keck Laboratory at the University of California, Irvine (UL-
49 KIU) (Table 2). These terrestrial ages were calibrated using IntCal 13 calibration curve using Calib 7.10 software.
Micromorphological analysis was performed to study microfacies induced by both natural and/or anthropogenic processes (Bullock, 1985; Van Vliet-Lanoë, 1985; Fitzpatrick, 1993; Stoops, de Melo Marcelino & Mees, 2010; Macphail & Goldberg, 2017). This analysis allowed us: 1) to precise and validate our macroscopic observations, 2) to outline genetic processes of observed micro-organisations (e.g., geomorphological, bio-pedological and cryogenic factors) and 3) to identify microartefacts and microecofacts generated by human occupation. Nine unperturbed and oriented samples were collected using Kubiena boxes. Processing was performed at the Laboratoire ARKEOLAM at the CEN, Université Laval. Samples were impregnated, hardened with epoxy resin and sliced into 30 μm-thick sections. The thin sections were analyzed using a Leica DM-4500 polarized microscope in planepolarized light (PPL) and crossed-polarized light (XPL) (10X to 400X magnification) at the microscopy laboratory at CEN, Université Laval.
In addition, a Raman analysis was used as complementary approach to micromorphological analysis. It was performed to identify carbon-based black pigment observed on one of the thin sections. This approach was only recently developed and the identification of the spectrum in terms of components characterisation is still difficult (Coccato, Jehlicka, Moens & Vandenabeele, 2015). The analysis was carried out on uncovered thin sections at PACEA laboratory (Université Bordeaux 1, France).
50 IV RESULTS
1. OFF-SITE GEOMORPHOLOGY AND STRATIGRAPHY The studied valley is oriented south-north, perpendicular to the Kuuvik river estuary. It is delimited by two rock ridges on its eastern and western sides. About 600 m wide and 700 m long, it reaches a maximum elevation of 29±3 m in the upper section (upstream). Boulder fields and vegetated sandy deposits overlaying the Archean bedrock (about 50 cm thick) are located in some of these ridges. Post-depositional processes linked to periglacial activity have affected the post-glacial deposits, generating solifluction features such as small sheets and tongues. These forms occur mainly on the western slope of the valley (Figure 13).
The valley is overlain by post-glacial deposits consisting of regressive sandy shoreline deposits. These deposits constitute six main raised beaches (RB), partly reworked by runoff and deflation processes (Figure 14). The upper beach (RB1), at an elevation between 24 and 27±3 m asl, is significantly affected by deflation and runoff processes. RB2 is located along the western slope at an elevation between 18 and 24±3 m asl. RB3, at an elevation between 17 and 19±3 m asl, is characterized by large deflation corridors and is also locally affected by solifluction. RB4, at an elevation between 6 and 16±3 m asl, is located at the bottom of the eastern slope. RB5, at an elevation between 3 and 4±3 m asl, also shows large deflation areas. Finally, RB6 is the youngest beach that adjoins present shoreline deposits (maximum elevation of 2 m asl) (Figure 13). Downstream, the valley presents well-developed hydromorphic areas with ponds and temporary streams. In addition, cryogenic processes influenced the formation of hummocks and mudboils that affected glaciomarine clay in poorly drained areas (Figure 13).
Stratigraphic cross-sections excavated in raised beaches RB1 and RB3 revealed the sedimentary filling of the valley (Figure 15). Massive fine sandy clay (sub-unit U1.a) and stratified clayey fine sand (sub-unit U1.b) were observed in cross-section VP1 C7 and are associated with a deep-water distal deposition. Unit 2 is gravelly sand (U2); the shell beds in unit U2 of VP1 C7 are the only ones observed in the whole valley (Figure 13 and Figure 15). A Hiatella sp. shell was dated to 6194-6412 yr BP (2σ). Unit U2 is associated with shoreline sediments. A massive clayey silty sandy matrix-supported diamicton was
51 observed in the VP1 C6 stratigraphic cross-section (unit U3) and was interpreted as soliflucted deposits. Above the previous layer, cumulic deposits were observed in stratigraphic cross-section VP1 C2, consisting of alternating medium sandy beds and sandy organic lenses (unit U4). Owing to a nearby summer runoff channel (Figure 13), it is likely that these deposits stem from overland flows and periods of soil stabilization by tundric vegetation respectively. In the upper part of all the stratigraphic cross-sections, massive well-sorted medium sand was found (unit U5). This deposit displayed organic lenses in the VP1 C2 cross-section (Figure 15). Considering the current importance of aeolian processes in the valley, it is likely that these deposits were induced by aeolian activity (Figure 13 and Figure 14). Organic lenses could be linked to periods of stabilization of sandy deposits by tundric vegetation.
52 Figure 13: Geomorphological map of Paalliq 1 Valley and location of Structure 10.
53
Figure 14: Active deflation erosion by longitudinal corridors affecting raised beach RB3 (View to the south). Tundric vegetation patches are being progressively eroded between enlarging corridors.
54 Figure 15: Off-site stratigraphic cross-sections. RB = Post-glacial raised beaches.
55 2. IN-SITE STRATIGRAPHY AND CHRONO-STRATIGRAPHY As shown by in-site and peri-site stratigraphic cross-sections, shoreline deposits (C horizons) covered Archean bedrock (R horizon) in the western ridge of the valley (Figure 16). These deposits are 36 to 70 cm thick (unit U1). Structure 10 was excavated in these regressive post-glacial shoreline deposits. Unit 1 is overlain by alternating sandy and organic laminae (C, Ahb and Hb horizons) (unit U2) that were observed across the whole site. The thickness of sandy and organic laminae is variable, from the millimetric to centimetric scale. Unit U2 is overlain by L, F and H surficial organic horizons (Figure 16).
The stratigraphic cross-sections excavated in the peripheral wall (test pits I-1 and I-2) displayed the following sequence: units U1 and U2 are overlain by alternating units composed of massive pebbly sand (units U4 and U6) and units consisting of organic beds and sandy lenses (U3 and U5). Units U3 and U5 have a “folded” lenticular structure. These sandy lenses were not observed in the North-bis stratigraphic cross-section (test-pit I-1, cross-section excavated after micromorphological sampling), which suggests a local occurrence in these units. It is therefore likely that the massive sandy deposits are anthropoturbated sediments implemented by Thule-Inuit shovelling during the excavation of the house (Ap horizons) (Figure 16). These deposits would have been mixed with organic matter collected from the area surrounding the house (Op horizons). This technique has frequently been observed at Thule-Inuit archaeological sites(McGhee, 1996; Lemieux et al., 2011). A horizontal stone slab was also found at the bottom of the test pit excavated in the floor of the house (test pit I-3) (Figure 16).
On the bed platform (test pit I-7), the organic lamina at the bottom of unit U2 was found under a stone slab. The stratigraphic cross-section was excavated to the left of the slab (Figure 17). Owing to its location on the bed platform, this stone slab likely came from the collapsing of the roof structure. The bed platform is made of an organic matter lamina that was radiocarbon dated to 1466-1642 cal A.D. (Figure 16, Table 2). Radiocarbon dating was performed at similar depths on organic laminae from unit U2 in test pits I-3, I-4 and I- 5. The dates were 1317-1413 cal A.D., 1285-1387 cal A.D. and 1286-1392 cal A.D. respectively (Table 2). As shown in Figure 11, test pit I-3 was excavated at the bottom of
56 the bed platform. I-4 was excavated in the tunnel entrance and I-5 was excavated 2 m west of the test pit I-4 ( Figure 16).
Only a few artefacts and ecofacts were retrieved during the excavation of the test pits. These included a soapstone fragment in test pit I-5 (in unit U2) and a microblade fragment in a peri-site test pit. This microblade thus suggests a Dorset occupation prior to Thule- Inuit settlement (Desrosiers & Gendron, 2015). Charcoal fragments, including a Juniperus charcoal, were retrieved from an organic lamina of the test pit P-1 (in unit U2) and dated to 143-327 cal A.D. (Table 2). Bone fragments were sampled in units U5 and U6 of the peripheric wall (test pit I-2). One of the fragments that showed butchery traces was dated to 1449-1617 cal A.D. (Figure 16, Table 2).
57 58 Figure 16: In-site and peri-site stratigraphic cross-sections and location of sampling. Table 2: Radiocarbon and calibrated ages of the macrofossils and bone fragments sampled in test pits I-2, I- 3, I-4, I-5, I-7 and P-1 (in-site samples).
Age (cal Test Age (yr yr B.P.) Age (cal 14C Dated Lab. pit Unit Depth B.P.) (2σ) A.D.) (2σ) Material Number
Caribou bone fragment I-2 U5 10 cm 380±15 501-333 1449-1617 ULA-6901 showing butchery traces
Sphagnum sp. I-3 U2 10 cm 570±15 633-237 1317-1413 ULA-6803 leaves and stems
Empetrum I-4 U2 16 cm 655±15 665-563 1285-1387 ULA-6804 nigrum seeds
Empetrum I-5 U2 16 cm 645±20 664-558 1286-1392 ULA-6805 nigrum seeds
Sphagnum sp. leaves and I-7 U2 20 cm 340±35 484-308 1466-1642 ULA-6807 Empetrum nigrum seeds
Juniperus P-1 U2 33 cm 1785±15 1807-1623 143-327 ULA-6806 charcoal
59
Figure 17: Test-pit I-7, East stratigraphic cross-section. The stone slab at the right of the photo overlies the lower organic lamina of unit U2 (red dashed line). 3. MACROFOSSIL ANALYSIS Macrofossils from natural soils and those linked either directly or indirectly to anthropogenic activities were discovered at the study site (Figure 18). However, owing to the strong decomposition of organic matter, only a few macrofossils were identified. These include leaves and seeds from Empetrum nigrum, seeds from Eutrema edwardsii, Draba sp., Luzula sp. and Poaceae sp., wood fragments, Sphagnum sp. and moss leaves, and Cenococcum graniforme sclerotia (Figure 18). Data show the relative abundance of Empetrum nigrum seeds (in contrast to its leaves) in the tunnel entrance and just outside the structure (test pits I-4 and I-5). These findings could be explained by a differential taphonomy inducing preferential preservation of seeds during and after their burial in relation to pedogenetic processes and biological (pedofauna) activity (Brady & Weil, 2008, p.499-500). These processes could have caused the complete decomposition of leaves in the other test pits.
60 Besides, Empetrum nigrum fruit has commonly been observed in the Thule diet (Pigford & Zutter, 2014). The relative abundance of seeds in specific areas of the site, if not linked to taphonomy, could thus have been originated by the consumption of Empetrum nigrum fruit.
Macrofossils or microremains linked to human activity include wood charcoal, burnt moss, bone fragments, tan chert and quartzite flakes (Figure 18). Burnt moss was found in an organic lamina underlying the anthropogenic units that formed part of the peripheric wall while Tan chert and quartzite splinters observed near the tunnel entrance. They confirm a Dorset presence prior to the building of the semi-subterranean house by Thule-Inuit. Dark brown to black solid to friable alveolar particles were also frequently observed in the bed platform, in the floor of the house, in the tunnel entrance, outside in proximity to the structure and further downstream (in test pits I-3, I-4, I-5, I-7 and P-1) (Figure 18). These particles are interpreted as burnt fat particles by comparison with the burnt fat aggregates found in Inuit semi-subterranean houses in Labrador (Foury, 2017).
Only a few Chrysosplenium tetrandrum seeds were found in the tunnel entrance (test pit I-4) and on the floor of the house (test pit I-3) along with numerous Eutrema edwardsii seeds (Figure 18). Chrysosplenium tetrandrum is frequently observed in archaeological sites as being derived from human feces (Böcher, Holman & Jakobson, 1968). Eutrema edwardsii is a nitrophilous species found in moderately dry herbaceous environments. This plant is common in both archaeological sites and natural areas, but the concomitant observation of Eutrema edwardsii and Chrysosplenium tetrandrum could indicate an anthropogenic nitrogen enrichment of the soil in the floor of the house. Draba sp. seeds were identified in samples from test pit I-3, which could be associated with phosphorus enrichment of soils following research by Oberndorfer (2016). Montia fontana seeds were identified in samples from test pits I-3, I-4 and I-5. They are particularly numerous in two samples taken from test pits I-4 and I-5 (Figure 18). Montia fontana is frequently observed in wetlands or on rocky outcrops covered by mosses (Invasive Species Specialist Group, 2010; Lansdown, 2014; Payette, Garneau, Gauthier & Houle, 2015; Julve, 2017). Considering the local topo- geomorphological context, the presence of Montia fontana at the site could indicate hydromorphic conditions (i.e., poorly drained soil). The abundance of this Portulacaceae at the base of the H surface horizon of test pit I-4 and in organic laminae from unit U2 of test
61 pit I-3 supports the hypothesis that wet conditions might have been enhanced by the microtopography of the semi-subterranean house during vacancy winter periods.
On the other hand, Montia fontana has frequently been observed at archaeological sites in the Arctic as an apophyte species growing in wet disturbed lands (Fredskild, 1973, 1978, 1988; Zutter, 1999, 2000; Edwards, Schofield & Mauquoy, 2008; Schofield, Edwards & Christensen, 2008; Buckland, Edwards, Panagiotakopulu & Schofield, 2009; Zutter, 2009; Edwards, Erlendsson & Schofield, 2011; Edwards, Schofield, Kirby & Cook, 2011; Schofield & Edwards, 2011; Ledger, 2013; Ledger, Edwards & Schofield, 2014). Oberndorfer (2016) noted the absence of Montia fontana in the vegetation found at archaeological sites near Makkovik (Labrador) and highlighted the importance of boggy conditions for the growth of this species. Finally, Tardío, Molina, Aceituno-Mata, Pardo-de- Santayana, Morales, Fernández-Ruiz, Morales et al. (2011) documented an important cultural use of Montia fontana in the Iberian Peninsula diet, as it is a rich source of fibre, vitamin C and omega 3 fatty acids. However, no such cultural use has been recorded in the Arctic regions.
Organic lenses constituting the peripheric wall are formed of strongly decomposed organic matter. Only a few Sphagnum sp. leaf fragments were identified. It is thus not possible to determine the origin of this organic matter. It may have originated from surface horizons collected nearby by Thule-Inuit inhabitants or from peaty deposits on the banks of a nearby pond (Lemieux et al., 2011).
62 Figure 18: Location of identified macrofossils. 63 4. MICROMORPHOLOGICAL DATA Micromorphological analysis was performed on thin sections retrieved from shoreline deposits (U1) and from the overlying units characterized by alternating sandy and organic laminae. Samples from the peripheral wall and from the inside the house were also analyzed (Figure 19). Mineral and organic components as well as microfeatures associated with biopedological, cryopedological processes and anthropogenic processes were identified and interpreted.
A. Common features Except for the shovelled deposits, the mineral components consist of well to moderately sorted medium to coarse sand (300 - 900 µm) (Figure 20A and B). Sandy deposits are principally constituted of quartz (90%); secondary minerals include feldspar (plagioclase and microcline), biotite, amphibole (hornblende) and clinopyroxene (aegirine). These constituents reflect the mineralogy of the watershed of the Kuuvik River (Baragar, 2015) and likely originate from the Archean gneissic bedrock (more specifically, from the leucocratic granitoid gneiss and the leucocratic grey gneiss that comprise the outcrop in the Kuuvik estuary and in the upstream area of the Kuuvik River). Aegirine is a clinopyroxene frequently observed in metamorphic and volcanic rocks and its presence in studied thin sections also suggests the upstream erosion of the Archean bedrock.
Organic matter mainly consists of dark brown well decomposed and fragmented remains. Organic components include droppings from pedofauna associated with enchytraeids and/or collembolans, lichen remains, ectomycorrhizal mantles, hyphae and sclerotia (Figure 21). Post-sedimentary processes are illustrated by: 1) physico-chemical weathering of biotite (exfoliation), 2) frost shattering affecting bone fragments and sand (comminution), 3) cryoturbation in the active layer with rearranged particles (microcircles) and 4), translocation in the form of capping of the fine material (Fox & Protz, 1981; Fitzpatrick, 1993; Van Vliet- Lanoë, 1998; Todisco & Bhiry, 2008a; Stoops et al., 2010) (Figure 22).
B. Specific features of natural sediments - shoreline deposits and soils Throughout the site, the thin sections of shoreline deposits (unit U1) display a single-grain fabric. Intergrain microaggregate fabric is visible near the point of contact with the organic sandy unit above. Numerous simple and complex packing voids and monic to enaulic related
64 distributions were observed (Figure 20A and B). Thin sections from in-site and peri-site test pits (test pits I-1, I-3, I-4, I-5, I-7, and P1) reveal that the alternating sandy and organic laminae (unit U2) overlying the shoreline deposits are 2 to 20 mm thick and horizontally to subhorizontally arranged (Figure 19). Transition between organic and sandy laminae is sharp or gradual. In sandy laminae, a single grain to intergrain microagregate fabric with a variable organic microaggregate content was observed. The intergrain microaggregate content tends to increase near the point of contact with the overlying organic lamina. This could result from eluviation of constituents from Hb and Ahb horizons associated with pedogenesis in the active layer. Most of the grains are loosely arranged, with many simple and complex packing voids. Packing increases along with an increase in the organic aggregate content, inducing the formation of compound packing voids. Monic to enaulic or porphyric related distribution also occurred (Figure 20C and D).
Organic laminae display a granular fabric containing some sand particles and numerous subrounded aggregates of strongly decomposed organic remains. Organic microaggregates generally occur in soils affected by cryogenic processes (Bertran, 1999). As observed by Fox and Protz (1981), Van Vliet-Lanoë (1987) and Van Vliet-Lanoë (1985), cryogenic compaction associated with cryoturbation and/or differential frost heave occurring at the point of contact between organic and sandy laminae (with different frost susceptibilities) could have caused such a fabric. Packing is generally moderate to high; compound and complex packing void content increased along with sand content (Figure 20D and E). Spongy and lenticular fabric and complex packing voids with enaulic to porphyric related distribution were observed when sand content was low to absent (Figure 20F and Figure 23A). Lenticular fabric generally occurs in frost susceptible fine-grained soils. It can be generated by thermic contraction and cryodesiccation associated with ice lens formation processes (Van Vliet- Lanoë, 1985). Ice lens formation processes occur in wet fine-grained sediments that may be water saturated when soil freezing progresses (Stoops et al., 2010). Thus, a spatial variability of laminae thickness and of mineral and organic components characterises microstructures of alternating organic and sandy laminae. A resulting spatial variability of related distribution, voids and fabric was observed.
65 C. Specific features of sediments found inside the house The sample taken from the floor of the house (test pit I-3) has a distinctive microstructure. The laminae are at least 2 to 6 cm thick, with alternating pure organic laminae (with no sand) and pure/clean sand laminae (with no organic content). A spongy to isoband fabric was noted in the organic laminae, with planar voids and porphyric related distribution (Figure 23B). Numerous diatoms including Pinnularia, Eunotia and Neidium genera were observed (Figure 21F).
Some ecofacts associated with human activities were observed in the peripheral wall, the bed platform, the house floor, the tunnel entrance and in the vicinity (test pits I-1, I-3, I-4, I-5 and I-7). These ecofacts consist of bone fragments and wood charcoals, all of which are moderately to strongly decomposed (Figure 19 and Figure 24). Wood charcoals were also observed downstream of the house (test pit P-1). Two amorphous black vesicular microparticles that were interpreted as possibly being burnt organic matter were observed on thin section KM7.2 (test pit I-5). Raman analysis were performed on these two microparticles to determine their origin (Figure 24B). Using Raman analysis to identify carbon-based black pigments (i.e., products of carbonization) is seldom used and does not yet result in the precise identification of these pigments (Coccato et al., 2015). However, the Raman spectrum shows two bands of major amplitude at CA 1600 cm-1 and CA 1400 cm-1 (Figure 25). This spectrum typically corresponds to emissions by graphitic/carbonaceous matter, with the G band at CA 1600 cm-1 being associated with emissions by hexagonal graphite. The D1 band at CA 1400 cm-1 is a consequence of disorder in the graphite structure. Some D bands of minor importance appear as shoulders on the major D1 band (the D4 band), suggesting significant disorder of the graphite(Coccato et al., 2015). Coccato et al. (2015) describe the significant disorder of the graphite structure for carbonized organic matter particles, including plants. This disorder is reflected in the numerous D4 bands in the D1 band. Given these findings, the Raman analysis performed on vesicular particles from the KM7.2 thin section could indicate the presence of carbonized organic matter.
Micromorphological analysis was performed on units U4, U5 and U6 from the test pits excavated in the peripheral wall to document their structure and components (test-pit I-1). For all these units, the mineral components were found to be poorly sorted with fine to coarse
66 sand with some centimetric cobbles (Figure 23C and D). Organic remains are strongly decomposed. U5 displays heterogeneous organic, sandy and pebbly components. The organic lenses from U5 show a heterogeneous microstructure, with organic matter and few sand displaying a spongy fabric with compound packing voids and porphyric related distribution (Figure 23D). In addition, the sandy organic matter is constituted by a single-grain to intergrain microaggregate fabric with complex and compound voids and enaulic to porphyric distribution. Massive poorly sorted fine to coarse sand with pebbles was found in units U4 and U6, showing loosely arranged grains with simple packing voids, single grain fabric, some intergrain organic microaggregates and monic distribution. The sandy and pebbly components of unit U5 display the same microstructure (Figure 23C). The heterogeneous microstructure of the organic lenses constituting U5 and the poorly sorted particles in U4, U5 and U6 (test pit I-1) support the hypothesis that these sandy deposits were introduced as a result of shoveling by Thule-Inuit during the excavation of the house, which caused the deposits to be mixed with organic matter.
67 68 Figure 19: Location map of micromorphological thin sections. Figure 20: Primary microstructures: A) Sand with single grain fabric, simple packing voids, monic related distribution (KM4.2, PPL); B) Intergrain microaggregate structure near the point of contact with the unit above; single grain fabric with few intergrain organic microaggregates, single and complex packing voids, monic to enaulic related distribution (KM9.2, 2, PPL); C) Organic sand with numerous intergrain microaggregates (KM9.2, PPL); D) Alternating laminae of slightly organic sand and laminae of sandy organic matter; organic laminae show granular microstructure and sandy laminae present numerous organic microaggregates (KM3.1, PPL); E) Alternating laminae of slightly sandy organic matter with laminae of organic sand; slightly sandy organic laminae have granular fabric and prophyric-related distribution; organic sandy laminae display single grain fabric and enaulic distribution (KM5.1, PPL); F) Slightly sandy organic laminae displaying lenticular and spongy to granular fabric, highly decomposed organic components (KM2.2, PPL). 69 Figure 21: Organic components: A) Ectomycorrhizal mantles (EM). The central position, previously filled by a root/rhizome, is currently filled by decayed tissues (T), decomposed and fragmented organic matter (DFOM - KM7.1, PPL); B) Ectomycorrhizal mantles (EM), decomposed and fragmented organic matter (DFOM), and mesofauna droppings from enchytraeids and/or collembolans (D) (KM2.2, PPL); C) Lichen fragment (KM3.1, PPL); D) Hyphae fragments (KM5.2, 10X, PPL); E) Sclerotia (KM3.3, PPL); F) Diatoms (Pinnularia, Eunotia and Neidium genera - arrows) and decomposed linear brownish-orange organic remains (KM1.2, PPL).
70 Figure 22: Cryogenic and physico-chemical processes: A) Capping/trapping of fine material (KM6.2, PPL; KM4.2, PPL); B) Frost- shattered sandy particles (comminution) (KM3.1, PPL); C) Exfoliated biotite (KM5.1, PPL); D) Particle rearrangement/microcircles (KM5.2, PPL).
71
Figure 23: Main microstructures: A) Alternating laminae of organic matter with laminae of slightly organic sands; organic laminae display spongy fabric and porphyric related distribution; slightly organic sandy laminae present few intergrain organic microaggregates and monic to enaulic related distribution (KM7.1, PPL); B) Thick organic matter lamina with very low sand content; spongy to isoband fabric, planar voids, porphyric related distribution (KM1.2, PPL); C) Poorly sorted sand with low organic matter content; few intergrain organic microaggregates, heterogenous grain size (KM8.2, PPL); D) Organic sand and lenses of sandy organic matter; organic sand shows numerous intergrain organic microaggregates and heterogenous grain size; lenses of sandy organic matter reveal a spongy to granular fabric and heterogenous grain size (KM8.2, PPL). For all theses microstructures, the organic components mainly consist of highly decomposed organic matter.
72 Figure 24: Anthropogenic components: A) Conifer wood charcoal (KM7.2, PPL); B) Burnt organic matter (KM7.2, PPL); C) Decomposed bone microfragment (KM2.2, PPL); D) Decomposed bone microfragment (KM2.2, XPL); E) Decomposed bone microfragments (KM7.1, PPL); F) Decomposed bone microfragments (KM7.1, XPL).
73 Figure 25: Raman spectrums. Arrows designate D4 bands. Green circles on photos above each graphic show measurement locations. Each curve is associated to its corresponding point by the color of the center of the point. On both graphs, the G band is associated with emissions by hexagonal graphite. D1 and D4 (arrows) bands show the significant disorder of the graphic structure of the particles. 74 V DISCUSSION
1. SITE FORMATION PROCESSES AT THE REGIONAL AND LOCAL SCALES On the valley, the clay lying over the bedrock was deposited in a deep-water distal environment following the retreat of the Laurentide Ice Sheet. Shoreline sediments were then deposited during the regression of the post-glacial Tyrell Sea, forming raised beaches at different elevations. After land emersion, shoreline deposits were reworked by both runoff and aeolian processes, creating large deflation areas. A Hiatella sp. shell from shoreline deposits on raised beach RB3 (19±3 m a.s.l) was dated at 6194-6412 cal yr B.P. According to the study of emersion curves in the Akulivik-Cap Smith region by Gray, Lauriol, Bruneau and Ricard (1993), the emergence at an altitude of 20 m would have occurred at ca. 3100 14C yr B.P. (conventional age). According to the (Daigneault, 2008) study of the emersion curve at Kuuvik Bay – Digges Islands region, the emergence at an altitude of 20 m would have occurred at ca. 2000 14C yr B.P. (conventional age). The age obtained from the studied site is thus inconsistent with this data. However, it is important to note that such an old date has never been recorded in the Kuuvik Bay region. A Hiatella arctica shell recorded by Gray and Lauriol (1985) at an altitude of 30 m at Akulivik yielded an uncorrected age of 7700±140 14C yr B.P. (UQ-956). Daigneault (2008) also found Hiatella arctica shells in Kuuvik Bay inland at an altitude of 38 m. These yielded a conventional age of 6170±90 14C yr B.P. (GSC- 5420). The difference between uncorrected and calibrated ages is about 400 years (Lavoie, Allard & Duhamel, 2012). Hence, comparing the obtained dating with the literature illustrates the need to refine the model of deglaciation in the Kuuvik Bay region. Currently, the lack of data inhibits the development of a precise model at the regional scale, which means that it is difficult to determine whether the dated shell from shoreline deposits was the result of thanatocoenosis (i.e., specific taphonomy) rather than biocenosis, as was observed in the Tasiujaq Lake region by Lavoie et al. (2012).
The formation processes of the in-site stratigraphic unit U2 are of primary interest since it contains all the archaeological remains that were found at the site. This unit consists of alternating sandy and organic laminae and it overlies the shoreline deposits throughout the site. The sandy laminae show massive structure with moderately sorted particles, ranging from medium to coarse sand. Sandy laminae could result from niveo-aeolian deposition and subsequent post-depositional evolution. Niveo-aeolian deposits display subhorizontal
75 laminated strata of medium to coarse sand (Cailleux, 1974; Dijkmans, 1990; Ruz & Allard, 1995; de Vet & Cammeraat, 2012). The thickness of the niveo-aeolian deposits that were observed by (Lewkowicz & Young, 1991) varies from millimetric to centimetric, which is in accordance with the data from the Paaliup Qarmangit 1 site. Moreover, niveo-aeolian particles tend to become coarser with increasing wind speed whereas sand sorting increases with transport distance (Lewkowicz & Young, 1991). The imperfect sorting of sand particles constituting the sandy laminae of unit U2 could thus be explained by the proximity of the sedimentary source, located upstream in the valley (i.e., sandy raised beaches). At the microscopic scale, sandy laminae from unit U2 display single grain fabric with many simple and complex packing voids. According to Dijkmans and Mücher (1989), fresh niveo-aeolian deposits display microfacies with simple packing voids with vughs and planar voids. The absence of vughs and planar voids in the sandy laminae from unit U2 could be attributed to a local redistribution of niveo-aeolian particles during snowmelt by nivation processes, which may have caused the loss of the primary microstructural characteristics (Dijkmans & Mücher, 1989; Dijkmans, 1990). Following Christiansen (1996), the term nivation is used here in its widest sense to refer to all individual forms, processes and sediments associated with (or intensified by) the presence and disappearance of snow, particularly by perennial and seasonal snowpatches. The main reworking process is likely the surface sheet flow occurring on slopes during the early spring. At this time, the permafrost table is still high and the water infiltration into the frozen ground remains low (Woo, 1993).
In the studied valley, niveo-aeolian deposits likely derived from local sedimentary sources. As shown by the presence of large deflation areas carved into the unvegetated raised sandy beaches where erosional corridors are commonly observed, deflation and niveo-aeolian processes appear to be of major importance. The beaches have a south-north orientation, which is consistent with the prevailing wind direction (Figure 13 and Figure 14). The topographic conditions of the Paaliup Qarmangit 1 site at the top of the ridge may have favoured snow accumulation at the site, as it is protected from prevailing winds by the boulder field upstream (Dijkmans, 1990; Lewkowicz & Young, 1991). By contrast, the absence of stratigraphic unit U2 in cross-sections P-2, P-3 and P-4 could be explained by the exposure to prevailing winds on the downstream slope (Lewkowicz & Young, 1991). Moreover, as it has been show for natural nivation niches, it is likely that the semi-
76 subterranean house (i.e., anthropogenic hollow) favoured snow accumulation and the formation of a small snowpatch (Christiansen, 1996, 1998). Winter niveo-aeolian deposition inside the house would have occurred during vacancy phases (Figure 26).
The micromorphological and macrofossil data from test pit I-3 (excavated in the floor of the semi-subterranean house) and I-4 (located in the tunnel entrance) reinforce the hypothesis supporting the predominance of niveo-aeolian and nivation processes. The house appears to have formed a trough partially filled by (1) snow during winter (favoring niveo-aeolian deposition) and (2), by summer surface and subsurface meltwater flows, which contributed to the development of a wet vegetated area. The sandy laminae from test pit I-3 are 2 to 6 cm thick and have no organic matter content. Conversely, the organic laminae from test pit I-3 are at least 2 cm thick and contain very little mineral content. The absence of organic matter and dominance of mineral content in laminae suggest a low surficial vegetation activity when sandy laminae were deposited. Inversely, there was a lack of sedimentary supply during vegetation growth. The thickness of the sandy laminae may result from significant winter niveo-aeolian deposition inside the house, which was favoured by topographic conditions. The thickness of the organic laminae may be associated with surficial vegetation activity. Moreover, the numerous diatom genera (including Eunotia, Pinnularia and Neidium) identified in the organic laminae from test pit I-3 indicate acidic to slightly acidic dystrophic wet conditions (Spaulding & Edlund, 2008, 2009; Furey, 2010). Together, these diatom taxa and the Montia fontana seeds found in test pit I-4 suggest the existence of wet conditions in this area of the house (Kale & Karthick, 2015; Payette et al., 2015). Such wet conditions inside the house may have resulted from the release of water during the summer melt of the active layer and of the snowpatch, triggering vegetation growth (Figure 26). The tunnel entrance may have served as a drain for the meltwater, causing a redistribution of some aeolian particles in the pronival zone, as has frequently been observed in natural hollows (Schwan, 1986; Christiansen, 1998). This nivation process may have originated the massive structure of sandy laminae constituting unit U2. The pronival redistribution was likely limited in comparison to the same process in natural hollows due to the limited area and the low depth of the house, the low slope of the tunnel entrance and the presence of the peripheral wall (e.g., Christiansen, 1996, 1998). This indirectly human-induced nivation process may
77 thus have reworked the niveo-aeolian deposits and resulted in the loss of niveo-aeolian microstructures.
Numerous studies have shown that climate is a forcing factor in aeolian processes (Ball & Goodier, 1974; Ballantyne, 1981; Filion, 1984; Pye & Paine, 1984; Koster & Dijkmans, 1988; Bélanger & Filion, 1991). Filion (1984) has shown that climate forcing has a particularly noticeable effect on the eastern coast of Hudson Bay, where niveo-aeolian processes tend to predominate over aeolian processes (s.s.) (Bélanger & Filion, 1991). Dating of stratigraphic unit U2 shows a constant stratigraphic trend during a period that overlaps the Medieval Climatic Optimum (sometimes between A.D. 800 – 1350) and the Little Ice Age (A.D. 1450 – 1850) (e.g., Graham, Ammann, Fleitmann, Cobb & Luterbacher, 2011; Gennaretti, Arseneault, Nicault, Perreault & Bégin, 2014) . A marked decrease in surficial vegetation activity and an increase in niveo-aeolian processes might have not occurred during the Little Ice Age at the study site. Organic laminae observed throughout the whole unit may be associated with the stabilization of former niveo-aeolian deposits during the summer time, especially during warmer inter-annual climatic fluctuations (Gennaretti et al., 2014) (Figure 26). The vegetation occurrence and niveo-aeolian/aeolian processes through a period of climate cooling in the region local controlling factors (e.g., topography), generated a local environment which influenced the formation processes of the archaeological site.
78 Figure 26: Site formation processes of the Thule house at the Paaliup Qarmangit 1 site. Roof structure (including wooden poles) is hypothetical. Dry and cold period are associated with high aeolian deposition and low summer vegetation activity. Wet and warm conditions generate a decrease in the aeolian deposition and surficial vegetation growth causing stabilization of sandy deposits. The picture of niveo-aeolian deposits is from Koster (1988).
79 2. DIACHRONIC SETTLEMENTS: DORSET AND THULE-INUIT OCCUPATIONS The Dorset tan chert and quartzite from test pit I-5 and burnt moss fragments found in situ in the organic laminae underlying the deposits associated with the construction of the peripheral wall (test-pit I-2) attest to the occurrence of a Dorset occupation of the site prior to the construction of the Thule-Inuit semi-subterranean house. The Juniperus charcoal from test pit P-1 (Figure 18) outlines a terminus post quem of 143-327 cal A.D. for the Dorset occupation, corresponding to the Classic Dorset phase in Nunavik (Desrosiers & Gendron, 2015). Juniperus communis is the only species of that type encountered in northern Quebec (Payette et al., 2013). Juniperus is a shrub without a main trunk that grows in forest tundra. Since no significant evolution of the tree limit occurred over the last 3800 years in Nunavik, the charcoal likely originated from driftwood (Payette & Lavoie, 1994). The scholarly literature contains very few mentions of Juniperus driftwood, and Alix (1998) noted its low prevalence in the North-American Arctic. It is relevant that no Juniperus driftwood was sampled in Steetland’s collection sites, which include the Akulivik and Ivujivik regions (Steelandt, 2015). This may be explained by the shrub form of Juniperus that grows in forest tundra and rarely reaches 1 m in height (Payette et al., 2013). Steelandt (2015) has shown that the buoyancy of wood decreases rapidly with a decrease in its volume. Given the main water currents traveling north along the eastern shore in James Bay and Hudson Bay, Juniperus driftwood thus likely originated nearby (Steelandt, 2015). This scarcity is thus probably linked to the low volume of wood from this shrub species and the resulting low buoyancy. It is estimated that the time between the death of the shrub and its use by humans was very brief. Therefore, this dating likely indicates a Classic Dorset occupation of the site after 143-327 cal A.D.
Discontinuous winter Thule-Inuit occupations of the site occurred between 1317-1413 cal A.D. and 1466-1642 cal A.D. Radiocarbon dating of the house floor (test pit I-3) indicates a terminus ante quem for the construction of the house. The organic lamina overlying a horizontal stone slab (located at the bottom of the stratigraphic cross-section) was dated at 1317-1413 cal A.D. This stone slab would thus have been part of the floor of the house. The date may thus indicate Thule-Inuit occupation prior to 1317-1413 cal A.D. Moreover, in the peripheral wall (test pit I-2), a bone fragment displaying traces of butchering activities was sampled in the organic matter that the Thule-Inuit used to support the wall (U5). It was
80 probably removed from its original location and put there by the Thule-Inuit when they repaired the house. It was dated at 1449-1617 cal A.D., indicating Thule-Inuit occupation of the site at this period (Figure 16). Finally, dating performed on the bed platform (test pit I-7) may indicate the terminus ante quem for the abandonment of the structure. In this test pit, the organic lamina located at the bottom of unit U2 was dated to 1466-1642 cal A.D. and is overlain by a stone slab (Figure 17). The slab was likely situated there after the destruction of the house, which may indicate abandonment at this time. Moreover, it appears to be younger as compared with dates obtained at similar or lower depths in the floor of the house, in the tunnel entrance and outside of the structure close to the entrance (test pits I-3, I-4 and I-5). The different dates may suggest a stratigraphic hiatus between stratigraphic units U1 and U2 on the bed platform. Since the preparation and maintenance of the bed platform has frequently been observed elsewhere, the observed stratigraphic hiatus may be explained by the regular removal (e.g., site maintenance, cleaning) of organic layers over the bed platform (Figure 26) (Lemieux et al., 2011).
The use of Dorset archaeological sites by the Thule-Inuit has been observed frequently in the Eastern Arctic(Plumet, 1982, 1989; Labrèche, 2003; Ryan, 2003b, a; Lemieux, 2009; Lemieux et al., 2011). The use of locations is advantageous for the procurement of building material (e.g., peat, sand), raw materials (e.g., for lithics), food, and water (Plumet, 1989; Labrèche, 2003; Lemieux et al., 2011; Moody & Hodgetts, 2013). With regard to building material, the geomorphological data show the abundance of sandy deposits that facilitated the construction of the semi-subterranean houses at the Paaliup Qarmangit 1 site. Specifically, the peripheral walls of units U3 and U5 contained organic matter that had been mixed with sand (U4 and U6). However, the organic components of the organic lenses are highly decomposed (U3 and U5). While it is not possible to determine a peaty origin of the organic lenses, it is likely that they originated from the vicinity. The Thule-Inuit inhabitants may either have used surficial organic horizons or peat extracted from the banks of a nearby pond, since peat is commonly used by the Thule-Inuit to construct the peripheral walls of their houses (Figure 26) (McGhee, 1996; Lemieux et al., 2011). In addition, topographic and geomorphological conditions were also important factors in the selection of site location, such as the interest in securing an extensive view of the surrounding area and protection against prevailing winds (Plumet, 1982, 1989; Desrosiers, 2009; Bhiry et al., 2016). The
81 Paaliup Qarmangit 1 site affords a wide view over the studied valley, the Kuuvik River and beyond.
Concerning food resource accessibility, polynyas were suitable locations for ringed seals, bearded seals and walruses (Henshaw, 2003; Lemieux et al., 2011). In the present day, Inuit hunters from Akulivik use a polynya located near the valley in the mouth of the Kuuvik River estuary during the winter. Polynya formation is highly dependant on oceanographic conditions including ocean currents, upwelling or tidal fluctuations (Stirling, 1980; Smith & Rigby, 1981; Stirling, 1997). Schledermann (1980) and Henshaw (2003) have shown the possible persistence of polynyas through time including colder periods such as the Little Ice Age. Our interpretation assumes that polynya occurred near the study site during Thule-Inuit occupation.
3. POST-DEPOSITIONAL REWORKING OF ANTHROPOGENIC REMAINS Dorset lithic flakes were found in the tunnel within an organic lamina that was dated at 1286- 1392 cal A.D. (Figure 16). In Nunavik, the transition from Dorset to Thule-Inuit is estimated to have occurred between A.D. 1000 and A.D. 1200 (Desrosiers & Gendron, 2015). At Paaliup Qarmangit 1 site, Dorset occupation was estimated to have occurred after 143-327 cal A.D. and before Thule-Inuit occupation (1317-1413 cal A.D. and 1466-1642 cal A.D.). Due to the proximity of the test pit I-5 to the structure, it is likely that the Dorset artefacts (flakes) have been affected by post-depositional processes (Figure 26).
These observations raise questions concerning both the extent of this reworking and the natural and/or anthropogenic (Thule) agent(s) which generated it. However, anthropogenic reworking generated by the shoveling of the house, successive reoccupation phases of the structure and a regular clean-up (maintenance) of the house is a probable explanation. Data from the bed platform (test pit I-7) suggest a regular removal of organic layers above it. Moreover, excavation of the peripheral wall found evidence of Thule-Inuit bone fragments in the organic matter used by Thule inhabitants (unit U5), which indicates a reworking of archaeological remains during a possible seasonal repair of the house (Figure 26).
In addition to anthropogenic agents of site disturbance, natural processes such as runoff may have caused this reworking of artefacts. The structural configuration of archaeological remains can indeed be transformed both during and subsequent to their deposition by
82 numerous taphonomic and post-depositional processes, which may or may not be related to past human activities (Rick, 1976; Bowers, Bonnichsen & Hoch, 1983; Schick, 1986; Schick, 1987; Dibble et al., 1997; Vallin et al., 2001; Bertran et al., 2005; Bertran et al., 2006; Bertran et al., 2012; Bertran et al., 2017). This may be particularly true for open-air sites, whose artefacts are susceptible to significant lateral damage or displacement (Bowers et al., 1983; Rasic, 2004). At the Tayara site in northern Nunavik, for example, a detailed taphonomic investigation focusing on site integrity was performed by (Todisco et al., 2009). This study documented the size sorting of artefacts and reorientation of écofacts (bones) by summer water flows. Further analysis over a more extensive excavated area would help to document horizontal and vertical spatial transformations of artefacts at the Paaliup Qarmangit 1 site. Given the geomorphological context, it is possible that some horizontal disturbances occurred, but vertical spatial transformations generated by freeze/thaw cycles were probably limited due to the low frost-susceptibility of sandy deposits (Todisco et al., 2009).
VI CONCLUSION Geomorphological and stratigraphical studies have made it possible to document the evolution of sedimentary environments in the studied valley since the last glaciation. Clay was deposited in a deep-water distal environment during the post-glacial marine transgression. Shoreline sediments were then deposited from the upper to the lower part of the valley throughout the marine regression and isostatic rebound, which formed raised beaches at different elevations. After the emersion, aeolian and runoff processes reworked shoreline deposits of the valley. Periglacial processes such as solifluction and mudboil formation partly reworked the deposits on the valley and on its slopes. This periglacial activity is associated with the establishment of continuous permafrost during land emergence. Hydromorphic ecosystems developed, originated by poorly drained soils, mainly in the lower part of the valley.
Middens are usually the primary object of archaeological study rather than dwellings, since houses ordinarily contain less artefacts. However, our taphonomic study of a semi- subterranean house was performed to document formation processes of the dwelling structure. In particular, we documented formation of the unit U2 that contained archaeological remains. Data revealed the predominance of niveo-aeolian and nivation
83 processes at the origin of alternating sandy and organic laminae in this unit. Deflation areas located upstream in the valley may have been the main sedimentary source of sandy deposits. Whereas a decrease an increase in niveo-aeolian processes may be expected for the Little Ice Age, stratigraphical and micromorphological data and radiocarbon dating would reveal a constancy of niveo-aeolian processes throughout the Medieval Climatic Optimum (A.D. 800- 1350) and the Little Ice Age (A.D. 1450-1850). Niveo-aeolian processes were likely induced by climate-topographic controlling factors that generated a local environment that influenced the formation processes of the archaeological site. Warmer and wetter inter-annual fluctuations may have facilitated surficial vegetation growth, causing the stabilization of sandy deposits (i.e., incipient pedogenesis with thin Ahb/Hb horizons).
Numerous Palaeoeskimo and Thule-Inuit archaeological sites were inventoried in the valley during field work in the summer of 2015. The Paaliup Qarmangit 1 site is the largest one and was occupied by Classic Dorset and Thule people. Structure 10 was first occupied by Dorset inhabitants after 143-327 cal A.D. and then by Thule-Inuit between 1317-1413 cal A.D. and 1466-1642 cal A.D. The use of the site by two different cultures and the significant clustering of the numerous structures is likely due to the strategic features the local environment offers, including the availability of building material, food and water resources.
Macrofossil data and radiocarbon dates have shown that post-depositional natural and/or anthropogenic reworking of Dorset artefacts occurred at this site. The reworking may have been the result of shoveling by the Thule-Inuit, by successive reoccupations of the structure and by the regular maintenance (e.g., clean-up) of the semi-subterranean dwelling. Natural processes such as wind and summer surficial water flows may also have been involved in the reworking of artefacts. It would thus be useful to conduct a detailed taphonomic investigation of archaeological remains through future studies in order to assess any spatial disturbance or redistribution of artefacts/ecofacts.
Finally, this first study of the Paaliup Qarmangit 1 site shows the value of adopting a diverse range of geoarchaeological analytical methods as an initial approach to studying a Dorset/Thule site in Arctic region. Such a preliminary approach may provide relevant archaeological information where extensive excavations are not practicable or are strongly limited.
84 AKNOWLEDGMENTS The authors want to acknowledge the field crew for their support and help during the campaign, particularly our collaborators from Akulivik community, Joanasi Qaqutuk, Thomassie Irqumia, Joseph Tulugak, Davidee Angiyou and Niali Aliqu. We also thank Gabrielle Filteau, Willie Kumarluk, Camille Le Gall-Payne and Marianne Ricard. We also thank the Akulivik community for having originated this collaboration as well as Stephane Ferre (thin sections preparation), Mysostis Bourgon Desroches (paleoecology analysis), Alain Queffelec (Raman analysis), Émilie Saulnier-Talbot (diatoms identification) and Ann Delwaide (charcoal identifications) for their help and support in laboratories. Funding has been provided by the Natural Science and Engineering Research Council of Canada (NSERC), the Institut polaire français Paul-Émile Victor, the Centre for northern studies (CEN), Avataq and Akulivik Community.
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94 CHAPITRE 2
Geochemistry of a Thule-Inuit semi-subterranean winter dwelling in a periglacial context.
Héloïse Barbel1, Dominique Todisco2, Najat Bhiry1
1Department of Geography, and Centre d’études nordiques, Pavillon Abitibi Price, Université Laval, Québec, Canada, G1V 0A6 2Department of Geography and Centre d’études nordiques, rue Lavoisier, Université de Rouen, Rouen, France, 76821 Mont Saint Aignan Cedex
95 RÉSUMÉ Des analyses géochimiques ont été effectuées sur une maison hivernale semi-souterraine unifamiliale thuléenne du site Paaliup Qarmangit 1, situé dans une vallée périglaciaire du Nunavik (Québec, Canada). Cette étude vise à documenter l’impact anthropique sur la chimie des sols, à l’aide d’analyses FTIR et ICP-AES. Les résultats obtenus démontrent la pertinence d’utiliser conjointement des diagrammes en boîtes, des facteurs d’enrichissement, des analyses en composantes principales et des classifications ascendantes hiérarchiques pour documenter les signatures anthropiques de la chimie des sols. Des impacts anthropiques modérés mais significatifs sont observés pour plusieurs éléments. Les données soulignent l’importance et la difficulté de documenter la variabilité naturelle de la teneur élémentaire des sols pour permettre une interprétation non-biaisée des résultats. Les signatures chimiques anthropiques pourraient avoir été atténuées par des processus pédologiques, tels que le lessivage ainsi que des processus anthropiques, tels qu’un nettoyage régulier de la structure par ses habitants.
Mots-clefs : Maison semi-souterraine, habitat thuléen, géoarchéologie, périglaciaire, géochimie, Nunavik.
96 ABSTRACT Geochemical analyses were carried out on a single-family semi-subterranean winter Thule- Inuit house from Paaliup Qarmangit 1 site (JjGj-14), located in a periglacial valley in Nunavik (Quebec, Canada). This study aims to document human impact on soil chemistry using ICP-AES and FTIR analyses. Box plots, enrichment factors, principal component analyses (PCA) and ascending hierarchical clustering (AHC) appear to be suitable complementary statistical approaches to document anthropogenic impact in soil chemistry. Results demonstrate a moderate but significant anthropogenic signature on soil chemistry. Data highlight the importance and difficulty of documenting natural variability of element contents in soil to enable reliable interpretation of results. Cryo-pedological processes, such as leaching and biological remobilization, as well as anthropogenic processes, such as a regular cleaning of the house, may have buffered chemical anthropogenic signatures.
Key words: Semi-subterranean house, Thule dwelling, geoarchaeology, periglacial, geochemistry, Nunavik.
97 I INTRODUCTION Soil geochemical analyses of archaeological site has been widely recognized to be relevant to improve understanding of historic and prehistoric settlements. It includes the study of the elementary records of human occupation in soils (Entwistle & Abrahams, 1997; Wilson, Davidson & Cresser, 2005). The study of the spatial variation of element contents enable to identify the occurrence of archaeological sites and determine their limits (Heidenreich & Navratil, 1973; Sjöberg, 1976; Cavanagh, Buck & Litton, 1988). Elementary analyses have hence been widely used as prospection technics in archaeology (Bintliff, Snodgrass, Waters, Davies & Gaffney, 1992; Aston, Martin & Jackson, 1998; Schlezinger & Howes, 2000; Eckel, Rabinowitz & Foster, 2002). Geochemical analyses of anthropoturbated soils enable to document spatial use and organization of archaeological sites and the rhythmicity of their occupation (e.g. sedentary lifestyle, residential mobility) (Davidson, Dercon, Stewart & Watson, 2006; King, 2008; Middleton, Barba, Pecci, Burton, Ortiz, Salvini & Suárez, 2010). Moreover, this approach can be particularly relevant in the context of few or no architectural remains, historic archives nor artefacts (Cook, Kovacevich, Beach & Bishop, 2006). Despite of this high potential for improving the understanding of archaeological sites, widely used in temperate and tropical contexts (e.g. Terra Preta), only few studies have been performed to document the impact of past human activities on soil chemical components in American northern climates (McCartney, 1979; Moore & Denton, 1988; Derry, Kevan & Rowley, 1999; Frink & Knudson, 2010; Knudson & Frink, 2010; Butler, 2011; Butler & Dawson, 2013; Brancier, 2016; Couture, Bhiry, Monette & Woollett, 2016; Butler & Dawson, 2018; Butler, Lopez–Forment & Dawson, 2018).
Several criteria are fundamental for chemical elements to be considered as anthropic indicators. First, human activities must impact on the natural content of these elements in the soils of the studied archaeological site; Second, anthropogenic in-site variability must clearly appear while compared with natural off-site samples (natural variability); Third, modification of elements contents must be persistently recorded in soil to enable identification of human inputs (Entwistle, Abrahams & Dodgshon, 1998). However, only few attention has been paid until now to formation processes and taphonomy of these elementary archives (Butler & Dawson, 2018). Performing new studies in present periglacial environments will thus contribute to the development of new micro-geoarchaeological methodological tools relevant
98 to better understand functions of northern hunter-gatherer sites, including duration, seasonality and intensity of their occupation (Butler & Dawson, 2018).
Thule-Inuit of Nunavik were efficient marine mammal hunters (Lemieux, Bhiry & Desrosiers, 2011; Bhiry, Marguerie & Lofthouse, 2016). Their subsistence practices enabled them to adopt semi-permanent settlements consisting of communities of subterranean peat houses with roof structures made from whale bones or tree trunks (McGhee, 1996). As a response to the seasonal availability of alimentary resources, they adopted a seasonal economic and residential calendar (Woollett, 1999; Kaplan & Woollett, 2000; Woollett, 2007). Thule-Inuit have impacted on their environment in several ways. This study aims to document their influence over chemical components of a cryosol in a semi-subterranean house located in Kuuvik Bay. It seeks to explore the potential of ICP-AES multi-elementary analyses and Fourier transformed infrared spectrometry (FTIR).
II STUDY SITE The site is located in the Paalliq area in a small valley on the left bank of the mouth of the Kuuvik River estuary in Kuuvik Bay on the northeastern coast of Hudson Bay in the Ungava peninsula, Nunavik (Canada) (Figure 10). The site consists of fifteen semi-subterranean houses of different sizes, each one of which could shelter about five to twenty persons. The Kuuvik Bay lies on Precambrian Narsajuaq terrane and Cap Smith belt rocks (Daigneault, 2008; Baragar, 2015). The Ungava peninsula was covered and scoured by the Laurentian ice sheet during the last glacial period (Daigneault, 2008). Wisconsin glacial activity generated numerous glacially eroded hills and depressions, De Geer moraines, eskers, kames and other till deposits (Gagnon, 2011). In the Kuuvik Bay, the retreat of the ice sheet occurred between 8 000 and 7 000 B.P., followed by the post-glacial marine transgression of the Tyrell Sea onto the coastline to an altitude of up to about 117 m (Daigneault, 2008). The Tyrell Sea first induced glaciomarine sedimentation of deep-water marine clay. It reworked previous till deposits and generated boulder field formations as well as sandy raised beaches, all of which punctuated the isostatic rebound. Subsequently, aeolian, cryogenic and hydrologic processes reworked post-glacial deposits, partly obliterating the initial configuration of paleo- shorelines (Daigneault, 2008).
99 Kuuvik Bay lies in the shrub tundra ecozone and is underlain by continuous permafrost (Payette, Garneau, Gauthier & Houle, 2013). The region is characterised by a polar tundra climate with cold winters, short summers and a mean annual air temperature of -7.5°C (Houde, 1978; Daigneault, 2008; Payette et al., 2013). Annual precipitation is about 400 mm, half of which is snow. Monthly precipitation culminates between August and September (Houde, 1978). Westerly winds from the Hudson Bay prevail, with a mean speed of about 20 km/h (Daigneault, 2008).
Barbel (2018) documented the evolution of sedimentary environments in the studied valley since the last glaciation. Clay was deposited in a deep-water distal environment during the post-glacial marine transgression. Shoreline sediments were then deposited from the upper to the lower part of the valley throughout the marine regression and isostatic rebound, which formed raised beaches at different elevations. After the emersion, aeolian and runoff processes reworked the valley floor shoreline deposits. Periglacial processes such as solifluction and mudboil formation partly reworked the deposits on the valley floor and on the sides of the ridges. This periglacial activity is associated with the establishment of continuous permafrost during land emergence. On the valley floor, the accumulation of water induced vegetation cover and created hydromorphic areas.
100 Figure 27: Location of the Paaliup Qarmangit 1 site in Kuuvik Bay, northeast Hudson Bay.
101 Archaeological structures were inventoried on both ridges of the valley (Figure 11). On the top of the western ridge, a dozen tent rings, caches, and inuksuit associated with Thule- Inuit occupations were identified, but only a few Dorset artefacts were found. Upstream, a Dorset axial mid-passage feature was found on raised beach RB1 and was pit-tested. Signs of human occupation are more evident on the eastern ridge of the valley. In fact, in addition to fifteen caches found in a boulder field on the top of the ridge, thirty-four archaeological structures were inventoried in the northern area of the eastern ridge. Eighteen of these constitute an archaeological site located in a grassy boulder field in the lower part of the eastern ridge near the estuary shore (Paaliup Qarmangit 2 site). This site includes five shallow semi-subterranean structures associated with Dorset winter houses and nine tent rings associated with Thule-Inuit summer occupations. Five caches and some Dorset artefacts were also recorded. The other fifteen structures were inventoried in an archaeological site located in an upper grassy area near the boulder field used for storage (caches) at an elevation of about 19±3 m. This winter Thule-Inuit site, called Paaliup Qarmangit 1, includes one hunting blind, nine single-family semi-subterranean houses and five multi-family semi-subterranean houses (Figure 11). These five multi-family semi- subterranean houses are one of the rare concentrations of large Thule-Inuit houses in Nunavik. Those large dwellings are more often observed in Labrador and Greenland (Woollett, 2007). This paper presents the geochemical study of a geoarcheological research performed on one of the single-family semi-subterranean houses (Structure 10), the tunnel entrance of which is oriented toward the valley (Figure 11 andFigure 12). A first paper is being published to present the taphonomic study we have performed over the site to document formation processes of the dwelling structure (Barbel, 2018). The studied house was excavated in shore-line deposits overlying the bedrock in this area of the ridge. The archaeological remains are contained in the overlying unit, unit U2. This unit consist of alternating organic and sandy laminae. Our data revealed the predominance of niveo- aeolian and nivation processes in the mixing of alternating sandy and organic laminae in this unit. Deflation areas located upstream in the valley may have been the main sedimentary source of sandy deposits. Whereas a decrease in surficial vegetation activity and a subsequent increase in niveo-aeolian processes are usually observed during the Little Ice Age, stratigraphical and micromorphological data and radiocarbon dating show a
102 constancy of niveo-aeolian processes throughout the Medieval Climatic Optimum (A.D. 800-1350) and the Little Ice Age (A.D. 1450-1900), which is likely due to local factors that generated a local environment that influenced the formation processes of the archaeological site. Warmer and wetter inter-annual fluctuations may have facilitated surficial vegetation growth, causing the stabilization of sandy deposits. The studied house was first occupied by Dorset after A.D. 143-327 (Classic Dorset occupation) and then by Thule-Inuit between A.D. 1317-1413 and A.D. 1466-1642. The use of the site by two different cultures and the significant clustering of the numerous structures is likely due to the strategic features the site offers, including the availability of building material, food and hydric resources.
103 Figure 28: Location of archaeological structures inventoried in the Paalliq 1 Valley (A), maps of the Paaliup Qarmangit 1 site (B) and the studied structure (C). Map of the studied single-family semi-subterranean house shows location of intra-site (I-1 to I-12) and peri-site (P-1 to P-4) test pits. Intra-site test pits refers to test pits excavated inside the house and nearby. The term “peri-site” refers to test pits dug in the vicinity104 of the house which could have been affected directly or indirectly by human activity, distinguishing them from off-site excavations located far from the archaeological sites in the valley.
Figure 29: Single-family semi-subterranean house at the Paaliup Qarmangit 1 site (Structure 10). The ashed line delimits the bed platform and the full line delimits the peripheral wall.
III METHODS Twelve in-site test pits (I-1 to I-12) were excavated inside and near the studied semi- subterranean house. Four peri-site test pits were excavated downstream of the house, at over twenty-five meters. We distinguish these deposits from those observed far away in the valley because peri-site deposits could have been impacted directly or indirectly by human activities (Figure 11).
According to the Canadian System of Soil Classification (Soil Classification Working Group, 2002), the studied soil is a regosolic static cryosol. This mineral soil is characterised by LFH horizons underlain by a Aej horizon. Aej horizon is underlain by alternating IIAhb and IIHb horizons with C horizons (cumulic niveo-aeolian deposits, U2). These horizons are underlain by a IIIC horizon (shoreline deposits, U1). An R horizon (bedrock) is observed at the bottom of some cross-sections. Finally, some Ap and Op horizons are observed in the peripheral wall (shoveling deposits consolidated with organic matter). Samples for FTIR and ICP-AES analysis were collected in IIHb and IIAhb horizons and H surficial horizon from test pits excavated in the peripheral wall, the bed platform, the floor of the house, the tunnel entrance and nearby (test pits I-1, I-3, I-4, I-5 and I-7). These samples are the archaeological one. Samples were also collected out in IIAhb horizons and
105 H surficial horizon from a test pit of the structure at about 20 m downstream of the tunnel entrance (test pit P-1). These are control samples (Figure 30).
106 Figure 30: Stratigraphy of the studied house. Thin sections give an overview of the structure of cumulic niveo-aeolian deposits (unit U2).
107 1. FTIR ANALYSIS FTIR (Fourier Transformed InfraRed spectroscopy) analysis were performed to document anthropogenic organic components soil content. FTIR analysis are widely used to identify molecules functional groups, to document atomic structures and to characterise unknown materials (Butler & Dawson, 2013). From this perspective, our FTIR analyse aims to identify anthropogenic components, such as ashes, charcoals, fat or bones, in soils.
FTIR analysis were realized at the Centre de Recherche sur les Matériaux Avancés of Université Laval. Samples were dried, finely crushed and homogenised. 1 mg subsamples were then collected from each sample and melted with 100 mg of KBr. After homogenising the mixture, drops were constituted and squeezed during two minutes at 10 000 lbs using an hydraulic press. FTIR analysis were then performed using a Thermo Fisher Nicolet is50 spectrometer.
2. ICP-AES ANALYSIS ICP-AES spectroscopy was performed to measure soil content of 10 major elements, 3 minor elements and 14 trace elements in order to document enrichment or impoverishment elements content of archaeological samples. This analytical approach was chosen for the large range of elements which may be analyzed simultaneously, rapidly and at low costs.
A. Sample processing ICP-AES analysis were performed at the Laboratoire des Services Communs of the Institut National de Recherche Scientifique, at Québec city. Samples were dried, finely crushed and homogenized. A first sub-sample was then collected to proceed to a loss in ignition to determine organic matter content. A second 1 mg sub-sample was collected and solubilized by alkaline fusion. ICP-AES analysis were then performed using a radially viewed ICP-AES Varian 725 with a cyclonic spray chamber and a Meinhart nebulizer. Element content (weight percentages) obtained didn’t include carbon, hydrogen, oxygen and nitrogen content. A correction factor was thus calculated using loss in ignition data.
1 푓 = 푐 1 − 푃퐴퐹 The number 1 at the denominator is due to the mass of the sub-sample (1 mg). Uncertainty of ICP-AES measurement is about 2% of the measured value.
108 B. Data processing and statistical analysis Data obtained from sample processing included organic matter content of each sample. To enable comparison of major, minor and traces elements content between samples, a normalisation of element contents by the organic matter content for each sample was thus necessary. Two statistical approaches were then adopted to document elementary enrichments or impoverishments. Elements whose content is frequently lower than ICP-AES spectrometer detection thresholds were excluded (As, Cd, Mo and Pb elements).
A first approach using box plots and enrichment factors, following Entwistle et al. (1998) and Butler (2011) methods was adopted.
Difference between in-site and control samples distributions for each of the 23 studied elements was estimated using a Student test. This test is a parametric one: the random theoretical model lies on a probability distribution belonging to a distribution family whose values are fully determined by a finished number of parameters (Desbois, 2004). In this way, the Student test is based on the acceptance that the sampling distribution follows a normal law. The availability of this postulate was thus prior verified proceeding to a Kolmogorov- Smirnov test. Moreover, the homogeneity of the variances is also required to allow the applicability of the Student test. A Fisher test, which is parametric, was thus performed after the K-S test, and prior to the Student test. K-S, Fisher and Student tests were performed using Matlab 2016 and Excel 2016 software. Box plots were then used to represent statistical spread of in-site and control sample for each element. Enrichment factors were finally calculated for each sample, following Entwistle et al. (1998) and Butler (2011) approaches. A two standards deviations range was used to determine the minimum significant value.
The second statistical approach was adopted to verify and support the first one. Principal components analysis (PCA) were performed using XLstat 2018 software to identify correlations between variations of each element content. This approach is very useful to confront multiple quantitative data. PCA consists in replacing variables which are highly correlated to a same principal component with this principal component. This approach allows the identification of sets of variables (i.e element contents) showing the same tendency. In other words, a high content of one of these elements would be associated a high content of others. The principal component would thus synthetize distributions of all the
109 elements which are highly correlated to it (Shennan, 1988, p.264). Different statistical approaches can be adopted to perform a PCA. We hear compare results obtained using correlation and covariance matrices, in order to show the importance of statistical bias which can impact on result interpretations.
Concerning correlation approach, principal components showing eigenvalues higher than 1.0 were considered to be both necessary and sufficient the simplify data while maintaining a valid statistic representativeness (Kaiser rule) (Shennan, 1988, p.264). Concerning covariance approach, Cattell rule was used to identify necessary and sufficient principal components to correctly simplify data while maintaining a valid statistic representativeness. Biplots observations and a study of squared cosines between variables and selected principal components documented relative importance of each principal component to represent each variable. Biplots representing sample distribution as a function of principal components were analyzed to do a visual distinction of samples showing strong enrichments or impoverishments. These samples would show an elementary enrichment or impoverishment highly correlated to the associated principal component. A comparison of the results obtained from this second statistical approach with the results of the first approach was then performed to verify and confront results.
Ascending Hierarchical Clustering (AHC) were then executed using XLstat 2018 software to verify PCA results statistical validity. These analyses aim to verify the validity of the visual interpretation of PCA biplots in terms of elementary enriched or impoverished samples, using a more objective statistical approach. AHC enabled a general indication, and weren’t performed to get precise clustering for the following reasons. First, the method used to determine distance between observations or samples (proximity) introduced a bias linked to the scale effect associated to the different units used to measure element content. We couldn’t perform a centralisation and normalisation of data for then calculate the weighted Euclidean distance as it is usually recommended, because it implies to choose the weight attributed to each variable (and thus decide which one is more relevant than another one, which is precisely one of the elements we seek to identify in our study). Second, a wide variety of methods can be used to determine distance between clusters (aggregation methods). They result from the different statistical methods to determine similarities and dissimilarities,
110 based on different approaches of minimisation of inter- and intra-cluster inertia (heuristic algorithm). Thus, a dissimilarity was calculated using Euclidean distance (proximity) and Ward method (aggregation method); four similarities were calculated using Pearson, Spearman, Gowser and Kendal coefficients (proximity) and unweighted pair-group average (aggregation methods). It has to be noted that XLstat converts similarities into dissimilarities, as the AHC algorithm uses dissimilarities.
3. CNS ANALYSIS CNS analysis was carried out to calculate C/N ratio of studied soil samples and document an eventually nitrogen anthropogenic inputs in soils. CNS analysis was executed at the Laboratoire de chimie analytique of the Département des sciences du bois et de la forêt of Université Laval. Samples were burned at 1450°C using a furnace and flue gases were then collected and piped to the detectors for the dosing. Dosing was performed using a Leco Trumac CNS. C/N ratio was calculated using Excel 2016 software.
IV RESULTS
1. FTIR ANALYSIS FTIR spectrums show important similarities between in-site and control samples None specific in-site pattern is observed. Some of the spectrums are presented in Figure 31. Numerous peaks corresponding to the silicate region are observed over the range CA 450- 1100 cm-1 (the main peak is at CA 1100 cm-1) (Goldberg, Berna & Macphail, 2009). Micromorphological analyses have shown the high predominance of silicate in soils mineral components of raise beaches (Barbel, 2018). Mineral components mainly consist of sand constituted by quartz (90%) and other accessory mineral as feldspar, mica, and pyroxenes. This is in accordance with the Archean gneissic bedrock (more specifically, from the leucocratic granitoid and grey gneiss that comprise the outcrop in the Kuuvik estuary and in the upstream area of the Kuuvik River) (Baragar, 2015).
Peaks at CA 1320-1385 cm-1, 1650 cm-1, 2920 cm-1, 2850 cm-1 and 3400 cm-1constitute the rest of FTIR spectrums. Peaks at CA 1320-1385 cm-1, 1650 cm-1 and 3400 cm-1 are released by O-H bonds. In another hand, 2920 cm-1 and 2850 cm-1 are associated to C-H bonds release (Goldberg et al., 2009). The whole of these peaks is thus likely associated to organic matter
111 content of samples, which is mainly constituted of carbon, hydrogen, oxygen and nitrogen (Goldberg et al., 2009; Butler & Dawson, 2013).
Owing to closeness of peaks associated to silicates with peaks which could be associated to anthropogenic components, such as charcoal and ash (CA 874 cm-1 and 713 cm-1), an overlap of these peaks is possible (Butler & Dawson, 2013; Paquet-Mercier, 2017). Thus, even if present in soil samples, these anthropogenic components couldn’t be identified, owing to the high silicate content. This could explain the absence of peaks associated to charcoal for one of the samples collected in test pit P-1 (Bed 2) whereas numerous charcoal fragments where identified by macrofossils analyses (Barbel, 2018). Moreover, this peaks-overlapping could have been reinforced by the relative low anthropogenic components content of soils in comparison with natural (organic as mineral) components content (Paquet-Mercier, personal communication, 2017).
112 Figure 31: Some of the Off-site and In-site FTIR spectrums.
113 2. ICP-AES ANALYSIS A. Box plots and enrichment factors Kolmogorov-Smirnov, Fisher and Student test results suggest the absence of significant difference between control and in-site samples. Analysing box plots and enrichment factor is a complementary approach to document differences between in-site and control samples and tests statistical bias.
For the whole elements, an important overlapping is observed for control and in-site samples box plots. Some of them are presented in Figure 32. This observation is not contradictory with statistical test results but complete them. Indeed, a Student test aims to document a significant difference between means of two sample populations. The important overlapping observed on box plot graphs is thus coherent with statistical tests results. Moreover, box plots are of main interest to document extreme values, which is very relevant in the context of this study.
Ca, Mn, Cu, P, S, Mg and Fe element soil content are usually related to human occupation and are thus relevant to document anthropogenic impact on soil chemistry (Couture et al., 2016; Butler & Dawson, 2018). An enrichment is graphically shown by an higher amplitude of in-site sample distribution in comparison with control sample distribution while observing element content box plots. Box plots show slight but significant differences between in-site and control samples for several elements. Ca, Mn, Cu and P elements display a significant enrichment for about 25% (3 samples) of the in-site samples. Samples show more frequently Mg, S and Fe enrichments (about 75% (9 samples) of in-site samples are S and Mg enriched and about 35% (4 samples) of in-site samples are Fe enriched) (Figure 32).
114
Figure 32: Box plots showing off-site (blue) and in-site (orange) distributions of Fe, S, Ca, Cu, P, Mn and Mg contents.
115 Enrichment factors show that significant enrichments are observed for all the in-site sample except for I-3_bed4 and P-1_bed2 samples. I-1_U5, I-5_U2_samp1, I-5_U2_samp2 and I- 4_H samples display particularly valuable and diversified enrichments. I-1_U5 sample is significantly Fe, Mg, Ti, Co, Cr, Ni, Sc and V enriched. I-5_U2 samp1 is significantly Mg, S, Cr, La, Ni and Y enriched. It has also to be noted that an important variation is observed between the first and the duplicated measure of Y content for I-1_U5 sample but not for I- 5_U2_samp1 sample. S5_U2_samp2 is P, S, Co, Cr, Cu, La, Ni, Sc, Sr and Y enriched. S4 H sample significant Al, Ca, Fe, Mg, P, S, Ba, Co, Cr, Cu, La, Ni, Sr, Sc and Y enrichments (Table 3).
Graphs localising measured element contents were realised to document the eventual spatial geochemical organization of the studied archaeological site. I-1 and I-5 test pits show enrichments, which is in accordance with enrichment factors result. Except for these test pits, none particular spatial scheme is thus observed.
116 Table 3: Enrichment factors and off-site element contents. All in-site data have been devided by the mean of their respective variable off-site mean. Significant ernichments (red cells) were determined from the mean of control sample values adding two standard deviations (higher limit). Significant impoverishments (green cells) were determined from the mean of comtrol sample values deducting two standard deviations (lower limit). “LDM” = Lower than Detection Limits ; “dup” = duplicated measure.
Al2O3 CaO Fe2O3 K2O MgO MnO Na2O P2O5 SiO2 S TiO2 Ba Co Cr Cu La Ni Sc Sr V Y Zn Zr % % % % % % % % % % % ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm Control samples P-1_bed 1 14,31 2,88 2,68 1,61 0,82 0,04 4,48 0,16 74,34 0,02 0,20 577,52 5,18 33,18 12,44 9,02 20,74 6,53 571,30 40,44 6,53 27,99 62,21 I-2_U2_bed1 14,43 3,52 2,12 1,36 0,67 0,04 4,42 0,89 70,57 0,03 0,19 573,16 9,10 38,99 46,79 36,39 29,89 5,20 575,76 25,99 8,84 75,38 66,28 I-2_U2_bed2 15,26 2,90 1,39 1,74 0,57 0,02 4,89 0,10 74,62 0,02 0,14 621,98 4,21 25,26 23,15 7,79 11,58 4,42 632,51 24,21 4,00 27,36 63,15 I-2_U2_bed3 14,76 2,87 1,61 1,45 0,63 0,03 4,75 0,07 74,64 0,02 0,15 529,63 4,13 28,91 8,26 6,81 16,52 4,96 602,93 26,84 4,03 20,65 83,63 In-site samples
P-1_bed2 1,02 0,94 0,71 0,96 0,98 0,73 1,07 0,37 1,03 0,81 0,80 0,90 LDL 0,95 0,37 0,55 1,11 0,77 1,04 0,74 0,69 0,55 0,94
P-1_ H 1,09 1,19 0,95 1,01 1,16 0,83 1,09 0,81 1,05 1,40 1,12 0,94 LDL 1,20 3,81 0,60 1,01 1,13 1,15 0,91 0,74 1,81 0,86 I-1_U5 0,95 1,02 1,81 0,90 4,60 1,44 0,91 0,98 0,97 1,18 1,68 0,86 2,53 14,47 1,16 0,96 8,10 1,58 0,89 1,86 1,14 1,20 0,73 I-1_U5 dup 1,01 1,12 1,71 0,91 4,27 1,39 0,99 0,90 0,97 1,38 2,65 0,90 2,10 12,02 0,51 0,98 6,71 1,60 0,95 2,03 4,27 1,10 1,09 I-3_bed1 0,97 0,97 0,94 0,98 1,18 0,85 0,95 1,56 0,95 1,65 1,11 0,99 1,20 1,18 0,55 2,48 0,97 1,01 0,95 0,96 1,43 0,84 0,90 I-3_bed3 1,03 1,03 1,09 1,01 1,33 1,10 1,03 0,81 0,99 1,20 1,08 0,94 0,95 1,25 0,28 1,23 1,14 1,11 0,99 1,06 1,10 0,76 1,20 I-3_bed4 1,01 0,99 1,13 0,97 1,08 0,98 1,00 1,44 1,01 1,34 0,99 0,94 1,02 0,98 0,90 1,46 0,76 1,00 1,00 0,94 1,36 0,76 0,87 I-4_bed4 1,02 0,98 0,84 0,96 1,01 0,78 1,06 0,72 1,03 1,41 0,82 0,91 1,16 1,90 1,15 1,11 1,27 0,85 1,00 0,85 0,84 0,78 0,76 I-4_ H 0,97 1,41 1,61 0,90 1,82 1,44 0,94 4,92 0,93 2,45 1,49 0,95 0,85 2,56 0,76 3,14 1,84 1,35 0,96 1,36 2,38 1,31 0,63 I-5_U2_samp1 0,98 1,17 1,16 0,97 1,76 0,81 0,93 2,60 0,99 1,78 1,24 0,95 0,94 2,41 2,24 5,16 2,51 1,06 0,95 0,91 1,99 1,13 1,28 I-5_U2_samp1 dup 0,99 1,14 1,06 0,98 1,59 0,62 0,95 3,01 0,93 2,88 1,01 0,98 1,18 2,54 2,41 5,87 2,24 1,09 0,96 0,91 2,15 1,16 0,97 I-5_U2_samp2 1,15 1,49 1,64 1,09 1,59 0,94 1,02 6,27 1,04 3,88 1,29 1,16 2,10 1,80 3,56 14,69 2,65 1,39 1,11 1,27 5,06 2,00 1,03 I-7_U2_bottom 0,99 1,02 0,98 0,98 1,13 1,11 0,99 1,20 0,98 1,52 1,08 0,97 0,60 1,19 0,66 2,43 0,98 0,99 1,00 0,89 1,36 0,81 0,71 Higher limit 1,06 1,21 1,59 1,22 1,33 1,52 1,10 3,58 1,05 1,53 1,35 1,13 1,83 1,37 2,52 2,90 1,79 1,34 1,09 1,51 1,79 2,33 1,29
Lower limit 0,94 0,79 0,41 0,78 0,67 0,48 0,90 -1,58 0,95 0,47 0,65 0,87 0,17 0,63 -0,52 -0,90 0,21 0,66 0,91 0,49 0,21 -0,33 0,71
117 B. Principal components analysis and clustering analyses Owing to the subjective dimension of results from box plots and enrichment factors approach, a second statistical approach was adopted to compare and verify results. A principal component analysis was performed to determine (1) the validity of the observed pattern of element distributions and (2) the presence of significantly enriched samples.
Concerning principal component analysis performed using covariance matrix, principal components 1 to 6 were selected following Cattell rule. These principal components can be considered to correctly account for the main part of the variance of the distributions (99.680%). PC1 and PC2 represent more than 89% of the global cumulated variance. PC 1 is highly correlated to Mg, Cr, Ni and V elements and PC 2 is highly correlated to Ca, P, S, Ba, Cu, La and Y (squared cosines higher than 0.500) (Figure 33A). In another hand, concerning principal component analysis performed using correlation matrix, principal components 1 to 10 have eigenvalues higher than 1.0 (Kaiser rule). These principal components can be considered to correctly account for the main part of the variance of the distributions (99.995%). PC1 and PC2 represent more than 71% of the global cumulated variance. PC 1 is highly correlated to Fe, Mg, Mn, Na, Ti, Co, Cr, Ni, Sc and V elements and PC 2 is highly correlated to Al, S, Ba, Cu, La, Sr and Y (squared cosines higher than 0.500) (Figure 33B). For both statistical approaches other principal components are not significantly correlated to none of the variable. Due to the high quartz content of sandy substrate and the natural variation of sand content in samples, Si content is not estimated to be relevant to document anthropogenic inputs in the context of this study (Barbel, 2018). The majority of in-site samples cannot be distinguished from off-site samples by biplot observation. However, I-1_U5 sample is highly correlated to PC1 and I-5_U2_samp2 is highly correlated to PC2 (for both covariance and correlation approaches). I-5_U2_samp1 shows lower correlation to PC2 (Figure 33 A and B). A comparison of PCA results with enrichment factors obtained for I-1_U5 and I-5_U2-samp2 samples shows significant enrichments for all elements the elements highly correlated to the principal component which they are respectively highly correlated with. Combining PCA and enrichment factors approaches seems thus to be relevant to 1) validate PCA results and 2) estimate which variable may show significant enrichments.
118 AHC results show, for all the methods used, a clear distinction of S1-U5 and I-5_U2-samp2 (which belong each one to their cluster) from other samples. Figure 33 C and D present two of the five AHC dendrograms we obtained.
119 Figure 33: PCA and AHC results. As mentioned in the method, XLstat converts similarities into dissimilarities, as the AHC algorithm uses dissimilarities (D).
120 3. C/N RATIO Both in-site and off-site values of C/N ratio range moderately from 11.03 to 18.19. None significant pattern of distribution is observed.
V DISCUSSION Box plots suggests in the whole moderate Ca, Mn, Cu and P enrichment and more significant Mg, Fe and S enrichments. Enrichment factors and ICP-AES analysis show I-1_U5, I-4_H and I-5_U2_samp1 and I-5_U2_samp2 samples to be significantly enriched. These results reveal a moderate but significant anthropogenic signature on soil chemistry.
Differences observed between enrichment factors and box plots graphs is related to two different approaches to define the occurrence of an enrichment. Enrichment factors method lies on a probabilistic approach which imply an homogeneity of the distribution on both sides of the mean value. This method focuses on extreme value to determine which sample would be significantly enriched. In another hand, box plots method lies on the spread around the mean and thus tends to neglect few sample which would show significant enrichments. The reliability of the enrichment factors approach lies thus on the normality of the distribution. However, it has to be notice that, even if Kolmogorov-Smirnov test results support this hypothesis, the low number of samples may be an important bias of the method, above all considering that normal distribution is seldom observed in natural context. Moreover, owing to the huge standard deviation of off-site P distribution generated by the very high value obtained for I-2_U2_bed1 sample, I-5_U2_samp1 is not considered to being enriched but we can notice the much higher enrichment factor of this sample in comparison with other in-site samples (to a lesser extent, the same observation can be done for Cu). This reveal the challenging aspect to estimate correctly the natural variation of element content in soils, which is enhanced by the low number of control samples, as observed by Butler (2011) and Butler and Dawson (2018). It underlines the necessity to focus on larger enrichment in order to avoid misidentification of an anthropogenic signal (Butler & Dawson, 2018).
Principal component analysis can be performed using different statistical approaches. We discuss hear covariance and correlation approaches, among those most frequently adopted, to show the necessity to think about the importance of the choice of the statistical approach to avoid bias in interpretation of data. Figure 33 A and B shows graphical difference between
121 both approaches (biplots). This difference is mostly explained by the buffering effect of correlation matrices (Pearson correlation), which eliminate scale effects, while covariance matrices attribute more importance to variable showing higher standard deviation. This imply different squared cosines for each principal component analysis. Thus, even if the correlation biplot may seem at the first sight to be more suitable to detect common tendencies in the variation of elements contents, this approach is statistically irrelevant regarding the interest of this study. This is well illustrated by having a look to Mn, which shows similar correlation as Cr on correlation biplots, whereas Cr is significantly enriched for several in-site samples and Mn is not (Table 3 and Figure 33 A and B). Principal component analysis suggests correlations between in one hand, Fe, Mg, Mn, Ti, Co, Cr, Ni, Sc and V contents (PC1) and in the other hand Al, Ca, P, S, Ba, Cu and La content (PC2), which could be related to a same process (Shennan, 1988, p.266-267). In this way, Bulter and Dawson (2017) have been able to attribute variability of some element contents to natural variability of soil components. However, owing to the lack of clear tendency in biplots, our data don’t able us to detect it. Integrating more samples in our study would likely refine ACP results and able a better interpretation, including an estimation of elements linked to natural variability. It has indeed to be noted that, according to (Hair, 1998, p.342), a ratio of 10 observations per variable is suitable to ensure statistical significance of PCA.
This highlight the importance and difficulty to estimate the natural variability and the underlying questioning of statistic representativeness of samples. A comparison with studies from periglacial environments (whether on archaeological sites or not) was performed to compare our range of natural and anthropogenic variations with the ones observed in other contexts similar to our and document the interpretative limits of our method. Variability of element contents observed from a site to another illustrate the huge variability of natural cryosols geochemical components (Schaefer, Simas, Gilkes, Mathison, Da Costa & Albuquerque, 2008; Butler, 2011; Szymański, Skiba & Wojtuń, 2013; Couture, 2014; Butler & Dawson, 2018). Moreover, Butler and Dawson (2018) and Oonk, Slomp, Huisman and Vriend (2009) have shown the importance of surficial deposits geochemistry in soil chemical signatures. The important overlapping observed for our control and in-site samples box plots could be attributed to such dominant soil formation factors (Butler, personal communication, 2017). However, geochemical analysis of the gneissic complex of northern Cap Smith belt
122 hasn’t yet been performed. It is thus limited to compare our data with those from other studies, even from similar pedological contexts. The same observation can be done for C/N ratio. Comparison with Broll, Tarnocai and Mueller (1999) and Tarnocai and Bockheim (2011) studies reveals a huge natural variation of C/N ratio for Ah an H horizons. It has also to be noticed that the diversity of analytical methods used to measure element contents (e.g. ICP-AES, ICP-MS, ICP-OES and (p)XRF), the scarcity of the raw data communicated in articles, and the absence of pedological context information contribute to make the task more difficult and to limit relevancy of comparisons (e.g., Lubos, Dreibrodt & Bahr, 2016).
To estimate the significance of our range of in-site enriched values, we compared for each element our range of off-site and in-site values with the natural range and in-site enriched values commonly observed in literature (Table 4). Some elements such as Cr, Ni, Cl, Cu, P and Y appear to show higher range value for our sample than for those of Butler (2011), Couture (2014), Butler et al. (2018) and Butler and Dawson (2018). Owing to the important variability between duplicated measures for Y, we don’t consider the enrichment to be significant for this element. In another hand, according to Couture et al. (2016) and Oonk et al. (2009), P, Ca, K, Na, Mg, Cu and Zn may be suitable anthropogenic indicators, which differs from our data. Morover, tendencies observed by Couture et al. (2016) for Co, Cr, Fe, Mn, Mg, Ti and S contents in the floor of the houses of Oakes Bay 1 and Uviak Point site (Thule-Inuit winter dwellings) are contrary to our results. These observations may highlight the difficulty to interpret data and apply results to other sites, even to those presenting the same kind of archaeological context.
123 Table 4: Comparison of our in- and off-site element content measurements with natural variability observed in literature for similar contexts. “=” Similar contents; “+” Our samples show higher contents than natural contents presented in literature; “-“ Our samples show lower contents than natural contents presented in literature; “ND” No data.
ELEMENTS BUTLER ET AL (2018) COUTURE, 2014 BUTLER, 2011 BUTLER AND DAWSON, 2018 (OH HORIZONS) (OH HORIZONS)
AL2O3 = = ND = CAO = = ND = FE2O3 = = ND = K2O = = ND = MGO = (+ for some of our in-site = - ND samples) MNO = = ND = NA2O = = ND + P2O5 = (+ for I-4_H and I- = (+ for I- = (+ for some of our in-site + 5_U2_samp2) 5_U2_samp2) samples) SIO2 ND = ND ND S - (= for some of our in- = = = site samples) TIO2 = = ND = AS ND ND ND ND BA = - = = CD ND ND ND ND CO ND - ND ND CR = (+ for some of = (+ for some of our in-site = (+ for I-1_U5) ND our in-site samples) samples) CU = (+ for some of our in-site samples = (+ for some of our in and one off-site ND + and off--site samples) sample (I- 2_U2_bed1) LA Our amplitude of = for all control samples (except for = (+ for some of = (+ for I-5_U2_samp2) control samples is I-2_U2_bed1 which is higher); + for our in-site samples) much higher most of in-site samples MO = ND ND ND NI = (except I-1_U5 which = (+ for some of = (+ for some of our in-site ND show higher value) our in-site samples) samples) PB = ND ND ND SC = = ND = SR + + ND + V = = ND = Y = (+ for some of our in- = (+ for some of our in-site site samples) (but high ND ND samples) (but high intra-sample intra-sample variability) variability) ZN = (+ for some of our in and off--site = = ND samples) ZR = - ND =
124 Important P enrichments occur in I-4 and I-5 test pits (located in the tunnel entrance and out of the structure, near the former). It has also to be notice that these P contents are much higher than those observed not only in archaeological but also in natural periglacial contexts (Schaefer et al., 2008; Butler, 2011; Szymański et al., 2013; Butler & Dawson, 2018; Butler et al., 2018). S enrichments are also observed for these samples. These enrichments may stem from accumulation of animal liquid and particles residues (Stein, 1992). According to Butler (2011), they may originate from brunt marine mammal oil and fat. However, Couture (2014) observed a S impoverishment of samples from the lampstand. Moreover, a Ca enrichment is also observed for these samples. Butler (2011) and Schaefer et al. (2008) suggest that a phosphorus enrichment associated to a Ca enrichment may result from bone decomposition.
Enrichment factors and box plots approaches and PCA analysis suggest low but significant enrichment of soils. This rise the questioning of a possible buffering of anthropogenic input by natural post-depositional processes, such as leaching (Cook et al., 2006; Oonk et al., 2009; Butler & Dawson, 2018). We use this term as defined by Schaetzl and Anderson (2005, p.348) to refer to the washing out of soluble materials completely out of the solum. Several factors control the thickness of the leached zone. The sandy texture of parent materials, the low thickness of surficial deposits above the slightly sloping bedrock and the high surface and sub-surface flows during summer may have favored and important leaching over years on the studied site, as it has been already observed in similar archeological and geomorphological contexts (Wells, 2010). According to Oonk et al. (2009) taphonomy of elements will differ depending on grain-size and mineralogy of soils. They consider that sandy soils are more likely to show Mg, P, Cu, Zn, Ni and Cr enrichments, which is consistent with our data. Moreover, mineral components of soils mainly consist in quartz minerals, which is relatively inert and contribute to the deepening of the leaching zone (Schaetzl & Anderson, 2005, p.359-360 ; Barbel, 2018).
If we have a look to the potential for the enriched elements to be leached or remobilized by soil organisms and plants, it appears that all the elements showing an enriched content may have undergone biopedological processes which may have buffer the anthropogenic record in soils chemistry. Organisms in soils may indeed have originated an important
125 remobilization of elements, above in cryosols, which have a naturally low content of available nutrients (Tarnocai & Bockheim, 2011; Bellenger, personal communication, 2018).
Phosphorus is frequently considered to be a relevant indicator of human activities (Butler & Dawson, 2018). This is due to the generally low leaching of inorganic phosphorus which could result from anthropogenic inputs. However, it has to be noticed that depending on the nature of anthropogenic inputs, it is possible that much of the phosphorus in anthropogenic organic inputs is present as dissolved organic phosphorus (like in feces). Dissolved organic phosphorus is highly soluble and can be easily leached, above all in fields with high water table, as it is the case in the studied site (Brady & Weil, 2008, p.607). It is thus likely that, depending on the type of human wastes, the phosphorus inputs are subject to undergo a differential record in soils (bones inputs being more sustainable than droppings).
Owing to the mineralogy of mineral soils components in the site (mainly quartz and secondary feldspar, biotite, hornblende and aegirine) Ca, Mg, N and S content in the soils likely mainly originated from organic components (Ping, Michaelson, Kimble & Walker, 2005; Brady & Weil, 2008, p.543-544, 583, 642-645 ; Barbel, 2018). As shown by micromorphological and macrofossils analyses, organic residues were highly decomposed by bio-pedological processes (Barbel, 2018). Owing to their high solubility under their inorganic form, elements are then integrated to soil solution and are then easily leached from soils (Schaetzl & Anderson, 2005, p.233; Brady & Weil, 2008, p. 552, 583, 588, 642). It has to be noted that the leaching of nitrate and sulfate is associated to a co-leaching of non-acidic ions such as Ca2+ and Mg2+ (Brady & Weil, 2008, p. 552, 588-589). A buffering of Ca and Mg my thus have occurred concomitantly with the leaching of nitrates. Measured content of such elements is thus likely to be much lower than the concentration initially generated by human activities (Harnois, 1988; Derry et al., 1999). Moreover, the aerobic environment associated to the sandy texture of soils may have been a factor favorizing stability and leaching of nitrates and sulfates (Brady & Weil, 2008, p. 584, 586). This may explain the occurrence of nitrophilic plants remains in organic layers from the floor of the house and the tunnel entrance (Barbel, 2018), while C/N ratio of soils doesn’t display any tendency.
According to principal components analyses, enrichment factors and box plot graphs, some micronutrients, as, Fe, Mn, Cu and Ni, as other trace elements, such as V, Al, Ba, Co, Cr, La,
126 Ti, Sc and Sr, Y seem to show a significant enrichment for some in-site samples. Micromorphological analysis have shown the predominance of silicate (quartz, felspars, biotite, hornblende) in the composition of mineral components of the soils of the studied, a significant part of micronutrient may thus have originated form mineral components of soils (in-site as off-site samples) (Brady & Weil, 2008, p. 651). Organic residues, particularly anthropogenic inputs such as feces, may have also been an important source of micronutrients (Brady & Weil, 2008, p. 659 and 662). During the decomposition process, some organic compounds react with the micronutrient cations to form organometallic complexes, the chelates, some of them are highly soluble and can be up taken by plants or leached by drainage water (Gylienė, 2001; Brady & Weil, 2008, p.653, 660-661). Hence, anthropogenic nutrients inputs may have contributed to the leaching of less stable soluble cations by modifying the natural nutrient content in soils. Owing to the different stability of the cation- chelating agent bonding, soluble chelates vary in stability (Brady & Weil, 2008, p. 661 and 662). It has also to be noted that the ability of cation to be leached depend on its solubility. For example, Ba, La, Fe(2+) and Sr are soluble whereas Sc, Fe(3+) and Al cations are not (Schaetzl & Anderson, 2005, p. 233, 2005).
Finally, post-depositional anthropogenic processes may have been involved in the taphonomy of anthropogenic inputs. Radiocarbon dating and stratigrahical and micromorphological analyses performed on the studied house have suggest a discontinuous winter human occupation over almost three centuries (Barbel, 2018). Results of ICP-AES analysis may thus indicate a regular cleaning of the semi-subterranean house (Habu & Savelle, 1994; Woollett, 2003).
VI CONCLUSION Our study thus enabled to document a moderate but significant anthropogenic signature on soil chemistry. Enrichment factors, box plots, PCA and AHC appear to be relevant complementary statistical approaches to document anthropogenic impact in soil chemistry. They have highlighted the difficulties and the importance of estimating natural variability of chemical element contents in soils to enable a reliable interpretation of results. Owing to the great variability of natural elements content in cryosols, which partly depend on pedological and biopedological factors, a comparison of data from a site to another is limited. We thus
127 estimate that analysing an important number of off-site samples is the best way to estimate significantly natural variation of element content in soils, which is also important to ensure the significance of statistical analysis.
Significant enrichments were observed of several elements but results didn’t enable the identification of specific areas over the site nor formal identification of specific activities. Data suggest a buffering of anthropogenic input by natural cryo-pedologic post-depositional processes, such as leaching and biological remobilization, and show the importance of developing pedological studies of cryosols in archaeological contexts. Moreover, anthropogenic processes such as a regular cleaning of the semi-subterranean house may have impact the anthropogenic signatures in soils.
Geochemical analyses of soils are still few performed in present periglacial archeological sites. This study thus demonstrates their potential to document discontinuous seasonal settlements. This approach is particularly suitable for studying archaeological sites showing a scarcity of artefacts and ecofacts and/or where extensive excavations are not practicable or are strongly limited. In such archaeological contexts, it may be relevant for future work to document more deeply geochemistry of rare earth elements, as lanthanides (using ICP-MS analyses), which tend to be less affected by leaching and biological remobilization and may leave more lasting signatures in soils.
ACKNOWLEDGMENTS The authors want to acknowledge the field crew for their support and help during the campaign, particularly our collaborators from Akulivik community, Joanasi Qaqutuk, Thomassie Irqumia, Joseph Tulugak, Davidee Angiyou and Niali Aliqu. We also thank Gabrielle Filteau, Willie Kumarluk, Camille Le Gall-Payne and Marianne Ricard. We also thank the Akulivik community for having originated this collaboration as well as Michel Caillier, Don Butler and Jean-Philippe Bellenger for their advices and Stéphane Prémont (ICP-AES analysis) and François Paquet-Mercier (FTIR analysis) for their help and laboratory analysis. Funding has been provided by the Natural Science and Engineering Research Council of Canada (NSERC), the Institut polaire français Paul-Émile Victor, the Centre for northern studies (CEN), Avataq and Akulivik Community.
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132 CONCLUSION GÉNÉRALE Dans le cadre de cette étude, nous avons démontré la pertinence d’adopter une approche multidisciplinaire multiscalaire combinant les analyses extra-sites et intra-sites d’un site archéologique en milieu périglaciaire actuel, notamment lorsque l’étendu des fouilles est limitée (pour diverses raisons). Ont aussi été documentés les processus de formation d’une maison semi-souterraine thuléenne-inuit et les impacts anthropiques sur la chimie des sols de la structure.
Les analyses stratigraphiques et géomorphologiques extra-sites ont permis de reconstituer l’évolution des environnements sédimentaires de la vallée dans laquelle est situé le site archéologique (Paaliup Qarmangit 1) depuis la dernière glaciation. Nos résultats démontrent que la maison étudiée fut habitée par les Dorsétiens après 143-327 cal. A.D. puis par les Thuléens-Inuit entre 1317-1413 cal A.D. et 1466-1642 cal A.D. L’utilisation du site par deux cultures différentes successives et le regroupement d’un nombre conséquent de maisons pourraient être expliqués par les caractéristiques stratégiques locales du lieu d’implantation : accessibilité aux matériaux de construction, aux ressources alimentaires et en eau.
L’étude des processus taphonomiques par l’entremise d’analyses stratigraphiques, micromorphologiques, et macrofossiles a montré la prédominance des processus nivéo- éoliens et de nivation dans la mise en place de l’unité contenant les restes archéologiques (niveau archéologique). Les zones de déflation présentes en amont dans la vallée constituent la principale source de ces dépôts sableux. D’après la chrono-strtigraphie, les processus nivéo-éoliens et de nivation auraient eu lieu tant pendant l’Optimum climatique médiévale (OCP, 800-1350 A.D.) que pendant le Petit Âge glaciaire (PAG, 1450-1850 A.D.). Si l’occurrence de ces processus pendant le PAG peut être associée aux conditions généralement froides et sèches de cette période climatique, ce raisonnement ne peut pas s’appliquer pour expliquer la formation des sédiments nivéo-éoliens et de nivation durant l’OCP. L’explication la plus plausible peut être en lien avec des facteurs locaux telle la forme en dépression de la maison semi-souterraine au sein de laquelle des sédiments nivéo-éoliens vont y être accumulés.
Les analyses stratigraphiques, macrofossiles et les datations radiocarbones ont mis en évidence un remaniement post-dépositionnels des artefacts dorsétiens sur le site. Il pourrait
133 avoir été généré par des facteurs naturels, tels que le ruissellement de surface estivale, ou des facteurs anthropiques, comme le pelletage par les Thuléens-Inuit, un nettoyage régulier de la structure et les réoccupations saisonnières successives de la structure.
En se basant sur les données des analyses FTIR et ICP-AES, il s’avère que l’impact anthropique sur la chimie des sols est modéré mais effectif (e.g., enrichissements en Mg, Fe, S). Les résultats obtenus soulignent l’importance qu’il faut accorder au traitement statistique des données afin de permettre une interprétation non-biaisée des résultats. En effet, il était très pertinent de combiner les facteurs d’enrichissement, les diagrammes en boîte, les analyses en composantes principales (ACP) et les classifications ascendantes hiérarchiques (CAH) afin de documenter les signatures anthropiques chimiques des sols anthropisés nordiques. L’estimation de la variabilité naturelle de la teneur élémentaire des sols est un enjeu important dans de telles analyses. Bien que des études comme la nôtre demeurent jusqu’à présent peu effectuées en milieu périglaciaire actuel, nos résultats montrent leur fort potentiel pour documenter des sites où les restes archéologiques (artéfacts et écofacts) sont parfois peu nombreux (tels les sites thuléens-inuit). Développer les études sur les processus cryogéniques (périglaciaires) et bio-pédologiques dans de tels contextes archéologiques permettrait de préciser la taphonomie des éléments chimiques et les facteurs pouvant atténuer les signatures anthropiques (tels que le lessivage dans la couche active et la remobilisation biologique).
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