No / A proxy climate record from a raised bog in County Fermanagh, Northern Ireland, is presented. The record spans the interval between 2850 cal. yr BC and cal. yr AD 1000 and chronological control is achieved through the use of tephrochronology and 14C dating, including a wiggle-match on one section of the record. Palaeoclimatic inferences are based on a combination of a testate amoebae-derived water table reconstruction, peat humification and plant macrofossil analyses. This multiproxy approach enables proxy-specific effects to be identified. Major wet shifts are registered in the proxies at ca. 1510 cal. yr BC, 750 cal. yr BC and cal. yr AD 470. Smaller magnitude shifts to wetter conditions are also recorded at ca. 380 cal. yr BC, 150 cal. yr BC, cal. yr AD 180, and cal. yr AD 690. It is hypothesised that the wet shifts are not merely local events as they appear to be linked to wider climate deteriorations in northwest Europe. Harmonic analysis of the proxies illustrates statistically significant periodicities of 580, 423-373, 307 and 265 years that may be related to wider Holocene climate cycles. This paper illustrates how the timing of climate changes registered in peat profiles records can be precisely constrained using tephrochronology to examine possible climatic responses to solar forcing. Relying on interpolated chronologies with considerable dating uncertainty must be avoided if the climatic responses to forcing mechanisms are to be fully understood.

No / A laboratory-based experiment was carried out to examine the dissolution characteristics of testate amoebae (Protozoa: Rhizopoda) under acidic conditions. The results suggest a large degree of variability in the dissolution susceptibility of taxa and no straightforward distinction between the relative robustness of xenosomic and idiosomic test types. Individuals from the genus Euglypha have tests composed of thin-walled siliceous plates, which are prone to severe dissolution. Certain other taxa are relatively unaffected by low pH conditions, including Assulina muscorum, Amphitrema flavum and Trigonopyxis arcula type. Differential preservation of subfossil testate amoebae must be acknowledged as a particular problem for peat-based palaeoclimate studies.

No description available.

La recherche développée dans le cadre de cette thèse se centre sur l’analyse de l’évolution et du changement en technologie lithique dans les sociétés de chasseurs-cueilleurs dans la Puna argentine à partir des sites de la localité de Susques, province de Jujuy. La Puna est un désert d’altitude (au-dessus des 3.000 masl). La période chasseur-cueilleur dans la Puna est comprise entre 11.000 et 3.500 ans AP. Ceci implique une séquence chronologique qui s’étend depuis le premier peuplement jusqu’à la domestication des camélidés. Dans un tel contexte, l’évolution des systèmes techniques a alors pu être dynamique durant cette période. L’analyse de 1’évolution technique se base ici sur l’étude des chaines opératoires et des systèmes techniques.Nous nous baserons donc sur une approche technologique, et donc sur la reconstitution des chaînes opératoires lithiques permet de resituer chaque objet dans son contexte technique et offre un cadre méthodologique pour l’interprétation à plusieurs niveaux d’analyse. En étudiant l’évolution des techniques selon deux voies - l’une lente liée au développement continu et intrinsèque des techniques, l’autre rapide, liée à des changements abrupts et externes - nous pouvons mettre en évidence des changements rapides et le rôle des sociétés et de leur environnement au sein de cette évolution. Nous observons un certain nombre d’innovations se produire au long de la séquence, dont la nature est différente; certaines étant liées aux premiers degrés des faits, et d’autres aux derniers degrés. Nous concluons qu’un tel développement a pu se produire grâce au développement de sociétés stables. / The research developed in this work focuses on the analysis of the evolution and change in lithic technology in the societies of hunter-gatherers in the Argentine Puna from the sites of the Susques locality, Jujuy. The Puna is an altitude desert (above 3000 masl). The hunter-gatherer period in Puna is between 11,000 and 3,500 years BP. This implies a chronological sequence that extends from the first settlement to the domestication of camelids. ln this context, the evolution of technical systems could then be dynamic during this period. The analysis of technical change is based here on the study of operative chains and technical systems. So we will use a technological approach, and thus the recovery of lithic reduction sequences can situate each object in his technical context and provides a methodological framework for interpretation at several levels of analysis. By studying the evolution of technology in two ways - one slow due to the continuous development and intrinsic techniques, other fast, due to abrupt changes and external contingencies - , we can highlight fast changes and the role of societies and their environment in this evolution. We see a number of innovations occurring throughout the sequence, whose nature is different, some are related to the first degree of the facts, and other are linked to the last degrees. We conclude that such development could occur through the development of stable societies.

Esta dissertação apresenta o resultado de um levantamento de sítios líticos caçadores-coletores no alto rio das Almas nos contrafortes ocidentais da Serra de Paranapiacaba. Dados sobre as indústrias líticas relacionadas são fornecidos sucintamente e comparadas às pesquisas desenvolvidas no Médio Ribeira por De Blasis (1988). Em acréscimo, esta Dissertação trata de estabelecer parâmetros para a compreensão da formação de sítios arqueológicos detectados em profundidade em porções de alta vertente, datados do Holoceno Médio. A continuidade de grupos caçadores-coletores na área de pesquisa é delimitada entre 5920 e 1000 anos AP e, em face a este período, tratamos de reconstruir os cenários sob transformação ambiental regional em a que estiveram submetidos esses grupos humanos e seus assentamentos. Nossa contribuição é desvincular os estudos sobre grupos caçadores-coletores do cunho hiper-determinista da tecno-tipologia lítica para uma discussão mais ampla que dialogue de forma transdisciplinar com a geomorfologia, a palinologia e a espeleologia. / This thesis provides the results of an archaeological survey focused in hunter-gatherer settlements from Upper Almas valley, on the western side of Paranapiacaba Mountains. Dates from lithics analysis associated to these sites are compared with results from Middle Ribeira valley, developed by De Blasis (1988). In addition, this Thesis treats to establish frames of reference to understand the formation processes of archaeological sites settled during the Middle Holocene in high depth on high portions of the mountains. The hunter-gatherer continuity between 5920 and 1000 yr BP in the studied area is approached by a paleoambiental treatment: our additional goal is to reconstruct the scenarios of environmental transformations in which these human groups developed their History. Furthermore, this thesis provides an instance to reduce the technological approach over these groups, opening an ecosystem approach which includes dates from palinology, geomorphology and espeleology.

The past stability of vegetation patterns in the Markham Valley (6°30’S, 146°30’E), a lowland grassland area of Papua New Guinea, is investigated by pollen analysis of lake deposits and related palaeoecological techniques.¶ The predominantly organic sediments of Lake Wanum (alt. 35 m) span the last 9600 years. A 14C chronology supports the calculation of annual pollen deposition, sediment accumulation, and carbonised particle influx rates. At Yanamugi lake (alt. 170 m), 14C assays of the calcareous muds are influenced by variable ‘hard- water error’. A tentative chronology is based on palaeomagnetic and tephra correlations.¶ Pollen trapping reveals very high contemporary annual deposition rates within forest, but low values over the central lake area. Surface pollen assemblages from different habitats indicate the localised nature of pollen dispersal, although a relatively ‘long-distance component’ from higher altitudes is also recognised.¶ Analysis of floristic data from the herbaceous swamp vegetation of Lake Wanum suggests the existence of two free floating root-mat associations and two or three rooted associations. Water depth appears the primary control on their distribution.¶ Holocene swamp communities analogous with extant associations may be identified in the palynological record of Lake Wanum. Swamp marginal conditions prevail from 9500 BP until 8200 BP when permanent shallow water becomes established. Rooted vegetation associations then predominate until about 5000 BP. Floating vegetation associations first become important at this time, and subsequently (3000 BP to 2000 BP) come to dominate the site. A general trend towards increased water depth is indicated throughout the sequence.¶ Increased representation of dry-land non-forest pollen occurs from 8550 BP, and grassland taxa become more frequent from about 5350 BP. Synchronous trends in carbonised particle influx identify fire as a probable agent of vegetation change.¶ Little change in dry-land vegetation is recorded in the pollen sequence from Yanamugi, although recent encroachment by swamp vegetation occurs. The large proportion of ‘montane’ pollen and spore taxa in the earlier sediments is attributed to variable fluvial influx. ¶ Conditions at Lake Wanum until 8200 BP may reflect the early Holocene aridity widespread in equatorial areas, although the indirect hydrologic effects of rising sea level cannot be discounted. Human impact appears the main determinant of dry-land vegetation change during much of the Holocene.

Lobjectif de cette thèse est la reconstitution des changements climatiques quaternaires à partir de critères sédimentologiques en milieu lacustre. Il sagit entre autre dutiliser les sédiments saisonniers comme un outil de datation précis pour calibrer les reconstitutions paléoclimatiques. Cette démarche permet de mieux comprendre lorigine et/ou la propagation dévénements chauds ou froids générés soit dans lhémisphère Nord, soit dans lhémisphère Sud. Le Lac Baïkal (Sibérie) et le Lac Puyehue (Sud du Chili) contribuent à établir des nouvelles connexions climatiques. Un volet important de la thèse concerne le développement dune méthode nouvelle pour détecter les sédiments laminés saisonniers dans les carottages. La méthode consiste à imprégner les sédiments argileux avec des polymères après avoir préalablement lyophilisé le matériel. Ce travail permet de montrer : (i) que la résolution des reconstitutions paléoclimatiques réalisées à partir des sédiments du Lac Baïkal peut être augmentée, à condition de calibrer le signal sédimentaire ainsi que la chronologie du 14C ; (ii) quil est possible de reconstituer lévolution des précipitations et des réponses de type El Niño à partir des sédiments lacustres du Sud du Chili ; (iii) que la chronologie des événements climatiques de la transition Pléistocène/Holocène est plus complexe, et les épisodes chauds/froids plus nombreux que précédemment décrits ; (iv) que les archives lacustres permettent de compléter les connexions climatiques entre les deux hémisphères.

Pollen analysis of a sediment core from Lake SP02, Melville Peninsula, Nunavut, Canada provides a ~6300 year record of post-glacial vegetation and climate change. Dominant local and regional taxa identified include Cyperaceae, Ericaceae, Artemisia, Salix, and Oxyria. Fossil pollen assemblages, pollen accumulations rates, and variations in sediment organic matter, indicate a period of optimal Holocene warmth between 5300-3900 yr BP, followed by a prolonged period of Neoglacial cooling, as well as a period of relative warmth between 1300-1000 yr BP, interpreted as evidence for the Medieval Warm Period. Variations in pollen abundances and accumulations during the 20th century suggest a response to recent warming that is unprecedented since deglaciation of the Peninsula. Comparisons of the timing and rates of multi-scale climate variations for Melville Peninsula with adjacent sites reveal a potential late Holocene shift in the boundary separating continental and maritime climate regions in the eastern Canadian Arctic.

Pollen analysis of a sediment core from Lake SP02, Melville Peninsula, Nunavut, Canada provides a ~6300 year record of post-glacial vegetation and climate change. Dominant local and regional taxa identified include Cyperaceae, Ericaceae, Artemisia, Salix, and Oxyria. Fossil pollen assemblages, pollen accumulations rates, and variations in sediment organic matter, indicate a period of optimal Holocene warmth between 5300-3900 yr BP, followed by a prolonged period of Neoglacial cooling, as well as a period of relative warmth between 1300-1000 yr BP, interpreted as evidence for the Medieval Warm Period. Variations in pollen abundances and accumulations during the 20th century suggest a response to recent warming that is unprecedented since deglaciation of the Peninsula. Comparisons of the timing and rates of multi-scale climate variations for Melville Peninsula with adjacent sites reveal a potential late Holocene shift in the boundary separating continental and maritime climate regions in the eastern Canadian Arctic.

No description available.