In the semi-arid southwestern US, the lack of continuous records of climate over the last glacial cycle has precluded a complete understanding of the rates and timing of past regional changes in climate. Speleothems can provide high-resolution, continuous record of moisture, temperature, and, potentially, vegetation variations and can be precisely dated by uranium-series disequilibrium. We have produced two U-series dated speleothem δ¹⁸O records from Cave of the Bells (COB). COB is located in Santa Cruz County, Arizona on the east side of the Santa Rita Mountains (31°45'N, 110°45'W; 1700 m). The glacial speleothem δ¹⁸O record (53 to 8.5 ka) confirms that deglaciation in the Southwest proceeded via a stepwise shift, mirroring the Bølling-Allerød warming and Younger Dryas cooling, beginning around 15 ka. There is no evidence of early warming before the decline of the large ice sheets. In Marine Isotope Stage 3 (MIS3; 53 to 30 ka), we observe millennial variations similar to Dansgaard-Oeschger (DO) events first seen in Greenland ice core δ¹⁸O records with wet/cold conditions indicated by our cave record during glacial stadials (cold periods) and dry/warm during glacial interstadials (warmer periods). High-resolution U-series dating allows for refinement of the timing of DO events in MIS3, and spectral analysis confirms the presence of a 1515-year climate cycle during this time. The δ¹⁸O data from a Holocene stalagmite (~6.9 to 3.5 ka) average ~3‰ higher than modern and exhibit substantial multidecadal to multicentury variation. We propose that in addition to drier/warmer conditions in the winter, a stronger summer monsoon and perhaps warmer summer temperatures supplied waters with higher δ¹⁸O values to the cave during the mid-Holocene. Spectral analysis of early part of the δ¹⁸O record reveals variability at periods of 233 years and at 142 and 52. After ~4.9 ka a prominent shift from centennial to multidecadal periods of variability (a 70 to 50-year cycle) is observed and there is a slight decrease in average δ¹⁸O values. This shift is coincident with a hypothesized increase in El Niño activity, which is correlated to wet winters in the modern southwest, in the tropical Pacific at ~5 ka.

This dissertation is a multidisciplinary study combining both archaeological andpaleoecological data to examine the rise of early Formative societies in Uruguay, La Plata Basin.It is contextualized within broader anthropological concerns related to the emergence of culturalcomplexity, the significance of ritual and public architecture in intermediate-level societies, andthe role of human-environment interactions during the mid-Holocene. This investigationgenerated the first Late Quaternary paleoclimatic record, based on pollen and phytolith analyses,documenting that the mid-Holocene (ca. 6,620 to ca. 4,040 bp) was a period of environmentalflux and increased aridity. It describes the occupational history of the Los Ajos site from thecreation of a household-based community integrating a centralized communal space during thePreceramic Mound Component (ca. 4,120 – 3,000- 2,500 bp) to the Ceramic Mound Component(ca. 3,000 2,500 bp to the Contact Period), where Los Ajos acquired a strong public ritualcharacter through the formatilization and spatial segregation of its mounded architecture. Duringthe Ceramic Mound Period, the site exhibited both internal stratification (inner versus outerprecincts) and dual asymmetrical architecture in its central sector, which suggest the emergenceof incipient social differentiation. This study also marks the earliest occurrence of at least twodomesticated crops in the region: corn (Zea mays) and squash (Cucurbita spp.), showing that theearly Formative societies adopted a mixed economy shortly after 4,120 bp. Collectively, theseresults challenge the long-standing view that the La Plata Basin was a marginal area byevidencing an early and idiosyncratic emergence of social complexity never before registered inthis region of South America.

A região cárstica de Lagoa Santa (MG) apresenta uma das evidências de ocupação humana mais antiga das Américas, datada do final do Pleistoceno e início do Holoceno. Um intenso registro arqueológico é observado nos períodos compreendidos entre 10.000 a 8.000 anos AP (antes do presente) e 2.000 a 1.000 anos AP. No período intermediário (Holoceno Médio) observa-se nos sítios arqueológicos uma minimização da representação desses vestígios. Autores denominaram esse período de \"Hiato do Arcaico\" que sugeriria que essas populações teriam emigrado por conta de eventos de seca na região, corroborados por dados provenientes da palinologia. O sítio paleontológico RMT-1, situado na região, pertence à bacia do Ribeirão da Mata e contém sedimentos de natureza aluvial datados entre 5.800-4.500 anos AP. e 2.500-1.500 anos AP. Neles estão contidos restos vegetais (pólen, lenho e folhas fósseis). O presente trabalho teve como objetivo principal identificar taxonomicamente assembléias fósseis de folhas por meio da morfologia com a finalidade de reconhecer com quais características fisionômicas atuais essa assembléia mais se assemelharia. As análises de similaridade confrontadas com 47 listas florísticas do Brasil demonstraram que houve alta correlação com Florestas Estacionais Semideciduais e formações de Cerrado. Não foi possível confirmar nem refutar a hipótese do \"Hiato do Arcaico\" já que não houve a presença de taxa que representariam exclusivamente um clima marcadamente seco, entretanto, sugere-se uma estacionalidade nas formações vegetais mais pronunciada ou uma associação fisionômica diferente das vegetações atuais expressadas por mosaico vegetacional. / The karst region of Lagoa Santa (MG) has one of the most ancient evidences of human occupation in Americas, dated from the end of the Pleistocene and beginning of the Holocene. An intense archaeological register is observed in periods between 10.000 to 8.000 years BP (before present) and 2.000 to 1.000 years BP. In the intermediary period (mid-Holocene) a decrease on the representation of these remains could be observed in the archaeological sites. Authors called this period \"Archaic Gap\" which suggests that these populations have migrated due to drougth events in the region that are corroborated by data from the palinological studies. The paleontological site RMT-1, situated in the same region, belongs to the basin of the Ribeirão da Mata and contains sediments of alluvial nature that are dated from 5.800-4.500 years AP. to 2.500-1.500 years BP. In these sediments plant remains (pollen, wood and fossil leaves) were found. The present study aims to identify fossil assemblages of leaves through the morphology to recognize which present physiognomy is closer to the assemblage. The analyses of similarity faced this assemblage with 47 floristical lists from Brazil, and demonstrated that there was a high correlation with semi-decidous stationary forests and cerrado. It was not possible to confirm neither to refute the hypothesis of the \"Archaic Gap\" since there was no observed taxa that could represent exclusively a markedly dry climate However, a more pronounced seasonality in the plant formations or a physiognomic association different from the present vegetational mosaics are suggested.

A região cárstica de Lagoa Santa (MG) apresenta uma das evidências de ocupação humana mais antiga das Américas, datada do final do Pleistoceno e início do Holoceno. Um intenso registro arqueológico é observado nos períodos compreendidos entre 10.000 a 8.000 anos AP (antes do presente) e 2.000 a 1.000 anos AP. No período intermediário (Holoceno Médio) observa-se nos sítios arqueológicos uma minimização da representação desses vestígios. Autores denominaram esse período de \"Hiato do Arcaico\" que sugeriria que essas populações teriam emigrado por conta de eventos de seca na região, corroborados por dados provenientes da palinologia. O sítio paleontológico RMT-1, situado na região, pertence à bacia do Ribeirão da Mata e contém sedimentos de natureza aluvial datados entre 5.800-4.500 anos AP. e 2.500-1.500 anos AP. Neles estão contidos restos vegetais (pólen, lenho e folhas fósseis). O presente trabalho teve como objetivo principal identificar taxonomicamente assembléias fósseis de folhas por meio da morfologia com a finalidade de reconhecer com quais características fisionômicas atuais essa assembléia mais se assemelharia. As análises de similaridade confrontadas com 47 listas florísticas do Brasil demonstraram que houve alta correlação com Florestas Estacionais Semideciduais e formações de Cerrado. Não foi possível confirmar nem refutar a hipótese do \"Hiato do Arcaico\" já que não houve a presença de taxa que representariam exclusivamente um clima marcadamente seco, entretanto, sugere-se uma estacionalidade nas formações vegetais mais pronunciada ou uma associação fisionômica diferente das vegetações atuais expressadas por mosaico vegetacional. / The karst region of Lagoa Santa (MG) has one of the most ancient evidences of human occupation in Americas, dated from the end of the Pleistocene and beginning of the Holocene. An intense archaeological register is observed in periods between 10.000 to 8.000 years BP (before present) and 2.000 to 1.000 years BP. In the intermediary period (mid-Holocene) a decrease on the representation of these remains could be observed in the archaeological sites. Authors called this period \"Archaic Gap\" which suggests that these populations have migrated due to drougth events in the region that are corroborated by data from the palinological studies. The paleontological site RMT-1, situated in the same region, belongs to the basin of the Ribeirão da Mata and contains sediments of alluvial nature that are dated from 5.800-4.500 years AP. to 2.500-1.500 years BP. In these sediments plant remains (pollen, wood and fossil leaves) were found. The present study aims to identify fossil assemblages of leaves through the morphology to recognize which present physiognomy is closer to the assemblage. The analyses of similarity faced this assemblage with 47 floristical lists from Brazil, and demonstrated that there was a high correlation with semi-decidous stationary forests and cerrado. It was not possible to confirm neither to refute the hypothesis of the \"Archaic Gap\" since there was no observed taxa that could represent exclusively a markedly dry climate However, a more pronounced seasonality in the plant formations or a physiognomic association different from the present vegetational mosaics are suggested.

Finely laminated sediments within Bainbridge Crater Lake, Galapagos, provide a record of El Nino-Southern Oscillation (ENSO) events over the Holocene. Despite the importance of this sediment record, hypotheses for how climate variability is preserved in the lake sediments have not been tested. Here we present results of long-term monitoring of the local climate and limnology and a revised interpretation of the sediment record. Brown-green, organic-rich, siliciclastic laminae reflect warm, wet conditions typical of El Nino events, whereas carbonate and gypsum precipitate during cool, dry La Nina events and persistent dry periods, respectively. Applying this new interpretation, we find that ENSO events of both phases were generally less frequent during the mid-Holocene (similar to 6100-4000 calendar years B.P.) relative to the last similar to 1500 calendar years. Abundant carbonate laminations between 3500 and 3000 calendar years B.P. imply that conditions in the Galapagos region were cool and dry during this period when the tropical Pacific E-W sea surface temperature (SST) gradient likely strengthened. The frequency of El Nino and La Nina events then intensified dramatically around 1750-2000 calendar years B.P., consistent with a weaker SST gradient and an increased frequency of ENSO events in other regional records. This strong interannual variability persisted until similar to 700 calendar years B.P., when ENSO-related variability at the lake decreased as the SST gradient strengthened. Persistent, dry conditions then dominated between 300 and 50 calendar years B.P. (A.D. 1650-1900, +/- similar to 100 years), whereas wetter conditions and frequent El Nino events dominated in the most recent century. Plain Language Summary Sediments accumulating at the bottom of Bainbridge Crater Lake have provided a record of Galapagos climate and the frequency of El Nino events over the past similar to 6000 years. Motivated by the importance of this lake for our understanding of climate in the tropical Pacific Ocean, we have been monitoring the link between climate, lake conditions, and the physical and chemical properties of the lake sediments since 2009. Based on this long-term monitoring, we find that the Bainbridge sediment record preserves both El Nino and La Nina events. This makes Bainbridge a particularly valuable archive of past climate, as most sediment-based records typically preserve only one or the other key phase of tropical Pacific climate.

In the recent past it has become evident that the Earth's climate is changing, and that human activity play a significant role in these changes. One of the regions where the ongoing climate change has been most evident is in the Arctic: the surface temperature has increased twice as much in this region as compared to the global average, in addition, a significant decline in the Arctic sea-ice extent has been observed in the past decades. Climate model studies of past climates are important tools to understand the ongoing climate change and how the Earth's climate may respond to changes in the forcing. This thesis includes studies of the Arctic climate in simulations of the early and mid-Holocene, 9 000 and 6 000 years before present. Changes in the Earth's orbital parameters resulted in increased summer insolation as compared to present day, especially at high northern latitudes. Geological data imply that the surface temperatures in the early to mid Holocene were similar to those projected for the near future. In addition, the geological data implies that the Arctic sea ice cover was significantly reduced in this period. This makes the early to mid-Holocene an interesting period to study with respect to the changes observed in the region at present. Several model studies of the mid-Holocene have been performed through the Paleoclimate Modeling Intercomparison Project (PMIP1 to PMIP3). The simulations have been performed with climate models of varying complexity, from atmosphere-only models in the first phase to fully coupled models with the same resolution as used for future climate simulations in the third phase. The first part of this thesis investigates the simulated sea ice in the pre-industrial and mid-Holocene simulations included in the PMIP2 and PMIP3 ensemble. As the complexity of the models increases, the models simulate smaller extents and thinner sea ice in the Arctic; the sea-ice extent suggested by the proxy data for the mid-Holocene is however not reproduced by the majority of the models. One possible explanation for the discrepancy between the simulated and reconstructed Arctic sea ice extent is missing or inadequate representations of important processes. The representation of atmospheric aerosol direct and indirect effects in past climates is a candidate process. Previous studies of deeper time periods have concluded that the representation of the direct and indirect effects of the atmospheric aerosols can influence the simulated climates, and reduce the equator to pole temperature gradient in past warm climates, in better agreement with reconstructions. The second part of the thesis investigates the influence of aerosol on the early Holocene climate. The indirect effect of reduced aerosol concentrations as compared to the present day is found to cause an amplification of the warming, especially in the Arctic region. A better agreement with reconstructed Arctic sea ice extent is thus achieved. / Under senare tid har det blivit uppenbart att jordens klimat håller på att förändras, och att mänsklig aktivitet spelar en viktig roll för dessa ändringar. Ett av de områden där den pägäende klimatfärändringen har varit tydligast är Arktis: temperaturen vid ytan har ökat dubbelt så mycket här jämfört med det globala genomsnittet. Dessutom har man observerat en betydande nedgång i havsisens utbredning i Arktis de senaste decennierna. Simuleringar gjorda med klimatmodeller av forntida klimat är viktiga verktyg för att förstå de pågående klimatförändringarna och hur jordens klimat påverkas av ändringar i klimatsystemets drivningar. Denna avhandling består av studier av det arktiska klimatet i modellsimuleringar av tidig och mid-holocen, ca. 9 000 och 6 000 år före nutid. Förändringar i jordens bana kring solen resulterade i en ökad sommar-solinstrålning jämfört med nutid, särskilt vid höga nordliga breddgrader. Geologiska data antyder att jordens temperatur vid ytan under denna period kan jämföras med dem vi förväntar för den närmaste framtiden. Vidare indikerar geologiska data att havsisen i Arktisk var kraftigt reducerad under denna period. Detta gör tidig till mid-holocen till en intressant period att studera, med avseende på de förändringar som för närvarande har observerats i området. Flera modellstudier av mitt-holocen har utförts i de olika faserna av Paleoclimate Modeling Intercomparison Project (PMIP1 till PMIP3). Simuleringarna har utförts med klimatmodeller av varierande komplexitet, från atmosfärsmodeller i den första fasen, till fullt kopplade modeller med hög rumslig upplösning i den tredje fasen. I den första delen av denna avhandling undersöks den simulerade havsisen i de förindustriella och mid-holocen simuleringar som ingår i PMIP2 och PMIP3 ensemblerna. Modellerna simulerar mindre utbredning och tunnare havsis i Arktis i den senare PMIP ensemblen, men fortfarande återskapar inte modellerna generelt den havsisutbredning som de geologiska data indikerar. En möjlig förklaring till skillnaderna mellan den simulerade och rekonstruerade havsisutsträckningen kan vara att viktiga processer i klimatsystemet saknas eller inte är tillräckligt väl beskrivna i modellerna. Beskrivningen av atmosfäriska aerosoler och dess effekter på klimatet är en möjlig kandidatprocess. Från studier av forntida varma tidsperioder har man dragit slutsatsen att beskrivningen av aerosoleffekterna påverkar det simulerade klimatet. Bland annat kan man minska temperaturgradienten mellan ekvator och polerna i tidigare varma klimat, vilket bättre överensstämmer med temperaturrekonstruktioner. Den andra delen av avhandlingen undersöker påverkan av aerosoler på klimatet under tidig holocen. Den indirekta effekten som följer av lägre aerosolkoncentrationer i tidig holocen jämfört med i dag, visar sig orsaka en förstärkning av uppvärmningen, särskilt i det arktiska områet, vilket stämmer bättre med havsisrekonstruktioner från denna period. / <p>QC 20130910</p>

No description available.

A 7.09 m lacustrine sediment core was taken from Mariana Lake, Alberta (55º57'N, 112º01'W) to determine if the regional vegetational complex had been affected by the mid-Holocene Hypsithermal. Dating control was provided by 6 radiocarbon dates, with a second degree polynomial fitted to the dates to give an age to depth curve. The basal date of the core is 11 300 ± 110 yr BP. Fossil pollen analysis of the core revealed five distinct pollen zones. Between 11 856 and 10 434 yr BP the study site supported a sparse herb dominated vegetation. A spruce and shrub birch assemblage followed, from 10 434 to 9 100 yr BP, with increased vegetation density. The climate was likely similar to today. This was replaced by a paper birch and spruce complex from 9 100 to 7 638 yr BP likely as a result of warming climate. A mild Hypsithermal effect is recorded between 7 638 and 5 623 yr BP. A forest of decreased crown density was created, with spruce, paper birch and poplar being the major vegetational components. Modern conditions have existed at the site from 5 623 yr BP onwards, though it is hypothesised the regional water budget may have increased slightly around 2 228 yr BP; increased peat development appears to have occurred at this time. Through the use of difference diagrams the site is compared to three other published sites which, along with Mariana Lake, form a north-south transect from the southern Boreal Forest to the northern Alberta Boreal Forest. The hypsithermal vegetation changes varies with distance to the Parkland-Boreal Forest ecotone boundary. It is concluded the parkland did not reach Mariana Lake during the mid-Holocene, though conditions at the site became similar to those at the southern edge of the Boreal Forest that is proximal to the parkland. / Thesis / Bachelor of Arts (BA)

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.

This thesis contributes to increased knowledge on Holocene climate and environmental variability from two complex and sparsely studied areas. Using a speleothem from Gasparee Cave, Trinidad, as a paleoclimate archive, the local expression of the 8.2 ka (thousand years before 1950) climate event and associated patterns of the inter-tropical convergence zone (ITCZ) and rainfall is provided. Subsequent speleothem studies using multi-proxy analysis of stalagmites from Kapsia Cave and Alepotrypa Cave, Greece, provide records of climate, vegetation and human induced changes in the cave environment during parts of the Holocene. The speleothems from the well-studied Neolithic habitation site, Alepotrypa Cave, have produced a climate and habitation record which covers the period of 6.3-1.0 ka. The cave was inhabited between 8.0-5.2 ka and was closed by a tectonic event, which has preserved the settlement. The stable oxygen record shows the first well-dated and robust expression of the 4.2 ka dry event in the Peloponnese, places the timing of the 3.2 ka dry event within an ongoing dry period, and shows a final dry event at 1.6 ka. The North Atlantic as well as more regional drivers, such as the North Sea Caspian Pattern Index is proposed to, in a complex interplay, govern many of the climate trends and events observed. Trace element variation after the site is abandoned indicate what is interpreted as two volcanic eruptions, the Minoan eruption of Thera (Santorini) around 3.6 ka and the 2.7 ka eruption of Somma (Vesuvius). Variations in trace elements during the habitation period show clear human influence, indicating an association with specific cave activities. One of the most interesting prospects for continued work on Alepotrypa Cave is this successful marriage of speleothem studies and archeology. A framework of dates which constrain some behavior of people living in the cave is only the beginning, and there is great potential to continue finding new clues in the speleothem data. / Denna avhandling bidrar till ökad kunskap om klimatets variationer och miljön i två geografiskt skilda områden på låga breddgrader och under tidsperioder inom den Holocena epoken. Genom att använda en droppsten (stalagmit) från Gasparee-grottan, Trinidad, som ett paleoklimatarkiv, har det bland annat varit möjligt att visa att Trinidad upplevde torrare förhållanden under den snabba klimatförändring som observerats ske för 8200 år sedan på många platser i världen. Denna torrare klimatsituation i Trinidad föreslås vara ett resultat av en sydlig förflyttning av den intertropiska konvergenszonen. Övriga stalagmiter som studerats för denna avhandling kommer från Kapsia-grottan och Alepotrypa-grottan som finns på Peloponnesos-halvön i Grekland. Resultaten därifrån speglar dels klimat- och vegetationsvariatoner och dels graden av mänsklig aktivitet, under tiden för ca 8000 år sedan till för 1000 år sedan. Alepotrypa-grottan är känd för att vara en av de större Neolitiska boplatserna i Grekland. Isotop- och spårämnesanalyser av stalagmiterna har bidragit med ny kunskap om tidpunkten för mänsklig aktivitet, hur människorna påverkade grott-miljön samt hur klimatet varierat efter det att grottan, genom en tektonisk händelse, stängdes för människans inverkan. Snabba klimatförändringar, för 4200 och 3200 år sedan, observerade i andra regioner, rekonstrueras här för första gången på Peloponnesos. En snabb förändring mot torrare förhållanden observeras även för 1600 år sedan. De klimatstyrande processerna föreslås vara en kombination av storskaliga processer som den nordatlantiska oscillationen och mer regionala processer som det så kallade North Sea Caspian Pattern Index. Variationer i spårämnen i stalagmiterna efter att Alepotrypa-grottan stängdes kan kopplas till två vulkaniska utbrott, nämligen det Minoiska utbrottet av Thera på ön Santorini kring 3600 år sedan och utbrottet av Somma (Vesuvius) kring 2700 år sedan. Spårämnesvariationer under bo-perioden ger tydliga indikationer på människans påverkan på grottmiljön och som delvis kan länkas till specifika aktiviteter, som eldning av dynga i grottan. Avhandlingen är ett resultat av en framgångsrik kombination av klimatstudier och arkeologisk kunskap och utgör ett viktigt underlag för fördjupat interdisciplinärt forskningssamarbete i Alepotrypa-grottan. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript. Paper 6: Manuscript.</p>