Three stalagmites, JSD 01, JSD 02, and L12, were collected from Libo county in the southern Guizhou provence. JSD 01 and JSD 02 are 14cm long stalagmites from Golden Lion Cave and L12 is a 7.1cm long stalagmite from Dragon Spring Cave. Subsamples were drilled along the central axis for JSD 01V while subsamples of JSD 01H were obtained along the horizontal axis. Subsamples were analyzed for carbon and oxygen stable isotopes. The age determination for stalagmites were done by U-Th dating. The JSD 01 dates range from 93,700 to 95,200 yr B.P.; the JSD 02 dates are from 87,900 to 88,200 yr B.P.. The L12 dates are from 750 to 9,560 yr B.P.. The stalagmite record from Golden Lion Cave is correspondent to the marine isotope stage 5 (MIS 5) in age. The £_18O values of stalagmite JSD 01 record in MIS 5c are ranging from -6.58‰ to -5.17‰ ; £_13C values are from -9.19‰ to -6.84‰. Stalagmite JSD 01H records are ranging from -8.11‰ to -5.7‰ for £_18O and from -9.67‰ to -2.46‰ for £_13C. The £_18O values for stalagmite JSD 02 record in MIS 5c are from -8.15‰ to -7.12 ‰ and are from -9.09‰ to -5.19‰ for £_13C. The results indicate a warm and wet climate prevailing during MIS 5c and MIS 5b in Guizhou. An intensification of summer mosoon would increase in precipitation and vegetation above the cave. Result from JSD record shows data obtained from the horizontal axis may be younger in age than vertical axis in terms of sampling direction. The stalagmite L12 contains two sections: (1) Dates range from 700 to 2,400 yr B.P. between top and 35mm: the £_18O values are ranging from -8.23‰ to -7.07‰ while £_13C values are ranging from -11.61‰ to -6.98 ‰; (2) The £_18O values are ranging from -10.52‰ to -7.54‰ and £_13C values are from -10.75‰ to -6.98‰ between 35mm and 71mm. Results suggest a warm and wet climate prevailing during 9,000-9,600, with lighter £_18O values reflecting a strong summer monsoon. A decline of summer monsoon occurred around 9,000 yr B.P. as shown by a sharp increase in the £_18O. This sudden climatic change might lead to a decrease in vegetation and soil loss above the cave, resulting in the cease growth of the stalagmite. Around 2,400 yr B.P. the growth of stalagmite was resumed. The lighter £_13C values and heavier £_18O values represent a cooler and drier climate in late Holocene. After ~1,000 yr BP, a deforestation event occurred in the area probably which was induced by human activity.

A stalagmite was collected in the Salón de la Permencia of the Majaguas Cave, that is a part of the Majaguas-Cantera Cave System in Cuba. The use of this stalagmite as a natural climate archive is advantageous not only because stalagmites can record continuous episodes of growth that are thousands of years in duration but also because they are easily and reliably dated, using U/Th dating methods. With this method, the stalagmite was reliably dated to 100 ka and was still active when removed from the cave for analysis. The stable isotopes of oxygen and carbon from this stalagmite from Western Cuba presents information of significant influencing factors on Caribbean precipitation records, and past climatic events during the Pleistocene. Due to the lack of high- resolution records for Western Cuba, this study verifies and adds to our knowledge of past climate variability for the Cuban region and the Caribbean as a whole. The δ18O data in MCS-01 shows a pattern that is very similar to the D-O and Heinrich events clearly recorded in the NGRIP ice core, especially at ~82ka and between 78-70ka. This study provides a continuous precipitation record for the area during the Pleistocene, allowing a greater understanding of the climate drivers that have had an impact on past precipitation patterns in this region.

Thesis advisor: Amy E. Frappier / A ~7,000 year stable isotope record from a Central American stalagmite is presented as a record of rainfall and consequently Intertropical Convergence Zone (ITCZ) tropical rain belt strength over the late Pleistocene to mid-Holocene. The "amount effect" explains the well-documented inverse relationship between rainfall amount and stable oxygen isotope values observed in tropical monsoon regions and consequently in stalagmite calcite from those regions. ITCZ rainfall influences much of the Central American tropical region and here a ~7,000 year stable isotope record from stalagmite ATM1 harvested from Actún Tunichil Muknal Cave in Belize is presented as a record of ITCZ influenced rainfall during the late Pleistocene to mid-Holocene (5,561 ± 2,488 BP - 12,605 ± 284 BP). Three major oxygen isotope excursions occur within the record. These excursions correspond to the global cold Younger Dryas and 8.2 ka events and a relatively undocumented wet period around 6,300 bp. The Younger Dryas manifests as a relatively moist period in central Belize while the 8.2 ka event manifests as a relatively dry period. The reason for the opposite responses to cooling elsewhere in the globe is posited to be due to orbital forcings. The 6,300 bp relatively wet period appears to be synoptic in scale and two possible triggers for the isotope excursion are presented: eustatic sea level rise causing lagoonal constriction, warming of water off the coast of Belize, and thus increased evaporation and precipitation over the study region; and hurricane clusters, evidenced in the region in the succeeding 1,000 years, in which the location of the Azores High funnels hurricanes to make landfall near the central Belize region. ATM1 provides evidence for tropical leads and/or lags to global climate events and bolsters the idea that high and low latitude climate relationships are complexly interlinked. / Thesis (MS) — Boston College, 2010. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Geology and Geophysics.

Thesis advisor: Amy Frappier / Tropical cyclones (TCs), known as hurricanes in the Atlantic and Typhoons in the Pacific, are among the most destructive and deadly natural disasters that occur on Earth. Attempts to understand how TCs relate to the global climate system, and future risk assessments are dependent upon having records of TC activity that pre-date the modern meteorological records, which are commonly not older than 130 years (Nott, 2003). Paleotempestology is a sub-discipline of paleoclimatology that attempts to extend the TC record beyond the meteorological record through the use of proxies. Presented here is the establishment of a paleotempestology proxy based on clastic mud being suspended in the water column by floods caused by TCs and deposited in stalagmite CH-1, collected in June of 2007 from Cenote Chaltun-Ha, a low-lying cave from the Yucatán Peninsula. CH-1 was dated by a combination of <super>210</super>Pb, U/Th, and layer counting techniques, creating an age model for its entire length. The years with mud layers were compared to the historical TC record from 1852-2006. Nineteen mud layers were identified for this time period. All of the mud layers deposited in years with at least one TC passing within 330 km of Cenote Chaltun-Ha. A total of 265 mud layers were identified in CH-1 dating from 198 BC to 2006 AD. Relatively high TC frequency, ~16 mud layers/century, was recorded in CH-1 from 198 BC to ~1233 AD. This period was followed by eight centuries of relatively low TC frequency, ~7 mud layers/century. The low frequency period hit a low point in the 1600s with 4 mud layers. Since the 1600s the TC frequency recorded in CH-1 has been on the rise, indicating possible periods of higher than present TC frequency in the future for the Yucatán region. This trend of high TC frequency followed by a sudden drop and subsequent increase is also reported in published sand overwash deposit research. &#948;;<super>18</super>O and &#948;;<super>13</super> values collected from CH-1 provide insight into the timing of regional droughts. A low &#948;;<super>18</super>O value from 1815 provides evidence that "The Year Without a Summer" caused by the 1815 eruption of the Tambora volcano in Indonesia had a climatic effect on the Yucatán. A land-use signal related to the agricultural production boom of Agave Fourcroydes, a succulent plant known as Henequen, in the early 20th century was also detected in &#948;;<super>13</super>C values. / Thesis (MS) — Boston College, 2010. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Geology and Geophysics.

Oxygen and hydrogen isotopes (δ18O, δD) are increasingly powerful tools for reconstructing past hydroclimate variability. The utility of δ18O- and δD-based paleoclimate records, however, depends on our understanding of how well these tracers reflect past climate conditions. The dynamics controlling the relationship between climate and water isotope variability are highly complex and often poorly constrained, especially in the tropics, where many key high-resolution paleoclimate records rely on past rainfall isotopes as proxies for hydroclimate. In this dissertation, I use multi-year timeseries of daily rainfall and biweekly dripwater δ18O from northern Borneo – a site for stalagmite δ18O-based paleoclimate reconstruction in the heart of the West Pacific Warm Pool – to track the cloud-to-calcite transformation of δ18O and its relationship to large-scale climate variability. Chapter 2 investigates the variability of rainfall δ18O variability from northern Borneo on diurnal to interannual timescales and its relationship with local and regional climate. Chapter 3 investigates the rainfall-to-dripwater transformation of climate-related isotopic signals following water transit through the Borneo cave system. Overall, this dissertation provides empirical support for the interpretation of northern Borneo stalagmite δ18O as a robust indicator of regional-scale hydroclimate variability, where higher δ18O reflects regional drying. More generally, this research provides a roadmap for obtaining more nuanced interpretations of speleothem δ18O records from multi-year, high-resolution, paired timeseries of rainfall and dripwater δ18O.

Déchiffrer le climat de l’Holocène est la base d’une meilleure compréhension du climat moderne. En effet, à cette époque le climat en Europe est très complexe est montre de fortes variations spatiales et il reste beaucoup à faire pour améliorer la couverture géographique d’enregistrements bien datés et de haute résolution. En tant qu’archives paléoclimatiques, les spéléothèmes ont de larges avantages concernant leur chronologie et leur résolution temporelle et peuvent aider à combler cette lacune. Dans cette thèse, des stalagmites holocènes ont été sélectionnées selon un transect N-S entre les latitudes 35° et 65°N à l’ouest de l’Europe et du bassin méditerranéen (de la Suède à l’Algérie). Elles ont été datées densément par U-Th et échantillonnées à haute résolution pour analyser leur composition isotopique et géochimique. Le climat de l’Holocène a été déduit des analyses isotopiques de la calcite (δ¹³C, δ¹⁸O) et du rapport Mg/Ca. Combinées avec les données existantes et avec les simulations numériques des modèles, ces nouvelles données ont permis d’émettre des hypothèses sur les processus dynamiques contrôlant les changement climatiques régionaux comme les divers modes impliqués dans la circulation océanique et atmosphérique. Sur un site archéologique particulier, le lien climat/activités humaines a aussi pu être étudié. Les principaux résultats de cette thèse sont : 1) les enregistrements en δ¹⁸O, δ¹³C et Mg/Ca d’une stalagmite de la grotte de Villars (sud-ouest de la France), ont révélé une variabilité décennale à multimillénaire du climat au cours des derniers 14200 ans ainsi que les preuves d’une déforestation il y a environ 1000 ans ; 2) deux stalagmites provenant de la grotte de Villars au sud-ouest de la France et de la grotte Korallgrottan au nord-ouest de la Suède ont enregistré de façon remarquable l’événement climatique du 8.2 ka et les différentes étapes qui le composent montrant des différences régionales de température et d’humidité entre les deux sites. Celles-ci sont associées avec une interruption suivie d’une réorganisation de la circulation océanique et atmosphérique ; 3) les enregistrements en δ¹⁸O et en δ¹³C de deux stalagmites de la grotte de Villars suggèrent aussi l’existence d’une période humide multi-centennale il y a ~7200-7600 liée éventuellement à la fonte de la dernière portion de la calotte de la Laurentide ; 4) les isotopes stables (δ¹⁸O, δ¹³C) d’une stalagmite de la grotte du Père-Noël située au sud-est de la Belgique, révèle de larges variations hydro climatiques entre 10500 et 4200 ans. En particulier, une période sèche multi-centennale est mise en évidence il y a ~5600-6000 ans probablement liée à un changement des vents d’ouest ; 5) au nord de l’Algérie, dans la grotte de Gueldaman, plusieurs stalagmites ont montré, par leur δ¹³C et leur δ¹⁸O, l’impact d’une période sèche sur l’occupation humaine et finalement l’abandon du site par les hommes préhistoriques il y a ~4200 ans. / Deciphering Holocene climate is the basis to understand modern climate change. The Holocene climate of Europe is highly complex and shows large spatial differences; much is to be done to improve the spatial coverage of well-dated, high resolution climate records. Stalagmite as paleoclimate archive has large advantages in its chronology and their temporal resolution and thus can help in answering this question. In this thesis, stalagmites were collected, broadly along a meridional transect from 35 to 65°N, in the west of Europe and Mediterranean basin (from Sweden to Algeria). They were densely dated by the U-Th method and their isotopic and geochemical compositions were analyzed at high spatial resolutions. The Holocene climate was inferred from the stalagmite δ¹³C, δ¹⁸ and Mg/Ca time series. Combining with existent data and model simulations the collected new data was used to understand dynamic processes involved in driving regional change, such as varying modes of ocean and atmospheric circulation. Uniquely, the possible links between the changes of past climate conditions and human activities at an archeological site were examined, too. The main results of this thesis are summarized as: (1) The δ¹⁸O, δ¹³C and Mg/Ca records of a stalagmite from Villars Cave, Southwestern France document a series of decadal to multi-millennial climatic variations over the last 14200 years as well as deforestation ~1000 years ago; (2) The precisely-dated, sub-decadal δ¹⁸O, δ¹³C and Mg/Ca records of stalagmites from Villars Cave, SW-France, and Korallgrottan Cave, NW-Sweden, reveal multiple stage climatic variations in relation to the 8200 year event. Reconstructed variations in both temperature and humidity exhibit different patterns at the two sites, respectively, in the south and north of Europe, which can be associated with the interruption and reorganization of ocean-atmospheric circulation; (3) The δ¹⁸O and δ¹³C records of two stalagmites from Villars Cave suggest multi-century wetness ~7200-7600 years ago which possibly linked to the demise of last portion of Laurentide Ice Sheet; (4) The δ¹⁸O and δ¹³C records of a stalagmite from Pere Noël Cave, Southeastern Belgium reveal large decadal to millennial hydroclimate variations between 10500 and 4200 years ago. Particularly, multi-century enhanced aridity occurred ~5600-6000 years ago which probably had attributed to the changes in regional atmospheric circulation and the westerly jet; (5) The δ¹³C and δ¹⁸O records of two Mid-Holocene stalagmites from Gueldaman GLD1 Cave, Northern Algeria provide evidence of a prolonged drought ~4200 years ago in Western Mediterranean basin. The drought coincides with, and therefore may have contributed to, an abandonment of ancient human occupation of the cave.

Barbados is the easternmost island in the Caribbean region, and is uniquely situated between the Atlantic Ocean and Caribbean Sea. Being an isolated island with a karstified aquifer providing the majority of the nation’s water resources, Barbados has found itself in water scarce situations in recent years. In order to better understand natural shifts in groundwater recharge (which is determined by shifts in precipitation), longer records of precipitation are needed than are available from modern measurements. This study presents a paleoclimate reconstruction for the late Holocene on Barbados using stable and radiogenic isotope ratios in speleothem lamina as proxies. In addition, it introduces the use of novel mineralogical analyses using Raman spectroscopy and large chamber-scanning electron microscopy to supplement the oxygen isotope record. For the past 1,500 years, the speleothem record indicates average δ18O values near -4.1 0/00, maximum δ18O values around -3.2 0/00 that coincide with the Little Ice Age climate event, while minimum δ18O values around -5.3 0/00 occur during the Medieval Climate Anomaly. Raman spectral analysis shows a recent period of increased Mg substitution, which potentially represents anthropogenic changes to the island’s epikarst aquifer caused by European settlement and sugar cane cultivation on Barbados. Electron imaging revealed chemically distinct layers of detritus within the stalagmite sample, facilitating precise sampling for U-series dating while also providing some information on the nature of weathering on the island. Additionally, time series analysis of the isotope record indicates multidecadal and multicentennial periodicities that conform well to that of the Atlantic Multidecadal Oscillation exerting influence on rainfall variability at the decadal scale, and the Intertropical Convergance Zone modulating rainfall at the multicentennial scale. Collectively, these data provide a climate reconstruction for the island of Barbados that is useful for better understanding change in cyclic precipitation patterns, as well as non-destructive methods for speleothem analysis that complement the isotopic study, while allowing sample preservation.

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Climate north of the Atlas Mountain belt in NW Africa is dominated by extratropical disturbances. However, climatic controls to the south, where climate transitions from extratropical to tropical regimes, are poorly understood due to a paucity of both instrumental and palaeoclimate data. In this thesis past climate change between the High Atlas Mountains and Sahara Desert is reconstructed using the stable isotopic composition and radiometric dating of speleothems. A high-resolution record from the mid-Holocene and a discontinuous record covering the past 400,000 years are developed. Supplemented by U-Th dating of a further four samples, these records indicate increased humidity in this area concomitant with the wider African Humid Period, and indicate a link between the West African Monsoon and humidity north of 30&deg;N. Reconstructed glacial-interglacial scale increases in humidity overlap with "green Sahara" conditions and evidence a recurrent humid corridor connecting NW Africa and the central Sahara that is highly relevant to discussions of prehistoric human migrations. Evidence for a strong influence of high-latitude and solar forcing on decadal to millennial time- scales in this area is also presented. Further to this work, the potential of cadmium-to-calcite ratios as a novel proxy for palaeo-hydrology is confirmed using an annually-resolved trace element, stable isotope and calcite fabric dataset from a North Moroccan stalagmite. The first measurements of cadmium-to-calcite ratios in natural speleothem are here presented, and the palaeoclimatic significance and potential of this proxy for aiding the quantitative reconstruction of changes in calcite precipitation behaviour are demonstrated.