Dissertations / Theses: 'Pleistocene Climate Changes'

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Chalk, Thomas B. "Boron based insights into Plio-Pleistocene carbon cycle changes and global climate evolution." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/374239/.

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From the Pliocene to the modern, the Earth’s climate has undergone a vast and significant change from a world dominated by continental ice restricted only to Antarctica with a rhythmic 41 kyr beat, through a period of declining atmospheric CO2 and cooling culminating with the bihemispheric glaciation known today, dominated by 100 kyr cyclicity. Ocean circulation is often given a central role in the dynamics of the late Neogene although many questions, such as the role of the North Atlantic in glacial-interglacial CO2 change remain. It is a well-studied region however and as such provides an ideal location for further study with novel proxies that may potentially provide new insights. Similarly, atmospheric CO2 is often thought to be the most crucial single variable driving Plio-Pleistocene climate change. Atmospheric CO2 reconstructions so far published beyond the end of the 800 ka Dome C ice core record are however few and of relatively low resolution and/or precision. This is at present hampering our understanding of CO2-climate interaction for climates warmer than the present and must be addressed as a priority given humanity’s ever-increasing CO2 emissions and anthropogenic global warming. This thesis aims to address these issues using boron-based proxies in foraminiferal carbonate. The potential power of these boron based proxies to directly quantify the marine carbonate system in the past has an enormous draw, both as a pH-CO2 proxy, but also for identifying the role of the deep ocean circulation changes in ocean carbon storage and release on orbital timescales. The first half of this thesis aims to better address the role of ocean circulation in rapid climate change and carbon storage over glacial-interglacial cycles. δ11B and B/Ca records from benthic foraminifera (Cibicidoides wuellerstorfi) from three cores in the North Atlantic spanning the last full glacial cycle and making up a depth, latitude and longitude transect are presented. These show that over this period, North Atlantic circulation is both dynamic and complex, presenting new and demonstrable links between climate change and the deep ocean carbonate system. Within this record a high-resolution section was taken focusing on the last 40 thousand years to search for any rapid changes in circulation associated with Heinrich events. It is demonstrated here that the boron based proxies can remove ambiguity from the existing records of deep ocean circulation change and challenge the established theory of deep water formation (DWF) shutdown in the Northern hemisphere during H-events. In the second half of this thesis atmospheric CO2 records, beyond the reach of the ice cores, derived from the δ11B of planktonic foraminifera (Globigerinoides ruber) from the tropical Atlantic basin and Caribbean Sea are presented. Here the relationship between the climate system (both in terms of ice-volume/sea level and temperature) is examined in climate states warmer than today. These include a suborbitally resolved record from 1.0-1.2 Ma to observe the nature of CO2 cycles before the ‘over thickening’ of the Laurentide ice sheet and the associated switch from 41 kyr to 100 kyr climate cycles at the Mid Pleistocene Transition (MPT). This study reveals the existence, around 1 million years ago, of high amplitude CO2 cycles with a 41 kyr cyclicity, and a mean CO2 level around 25 ppm above the Late Pleistocene. The relationship between CO2 and ice volume/SL prior to the MPT is significantly different to that post MPT, implying that CO2 decline and some other boundary condition change, probably related to the sub-glacial regolith, were both responsible for this most recent major climatic transition. Also reconstructed is a multisite reconstruction of atmospheric CO2, extending through the last 3.5 million years, including the onset of Northern Hemisphere Glaciation (iNHG). In order to gain a quantitative understanding of the role of CO2 decline in Plio-Pleistocene cooling a comprehensive compilation of sea surface temperature data is also presented. A combination of this record of “global” sea surface temperature data with the longterm CO2 data confirms that Plio-Pleistocene cooling was driven by CO2 decline amplified by the ice-sheet albedo feedback.

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2

Weirauch, Daniel R. "A high-resolution record of climate instability spanning ~1.0 million years across the mid-Pleistocene transition." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 131 p, 2007. http://proquest.umi.com/pqdweb?did=1472642111&sid=21&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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3

Eastwood, Rodney Gordon, and N/A. "Ant Association and Speciation in Lycaenidae (Lepidoptera): Consequences of Novel Adaptations and Pleistocene Climate Changes." Griffith University. Australian School of Environmental Studies, 2006. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20071130.134932.

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The butterfly family Lycaenidae (including the Riodinidae) contains an estimated 30% of all butterfly species and exhibits a diverse array of life history strategies. The early stages of most lycaenids associate with ants to varying degrees, ranging from casual facultative coexistence through to obligate association where the long-term survival of the butterfly is dependent on the presence of its attendant ants. Attendant ants guard the butterflies against predators and parasites during their vulnerable period of larval growth and pupation. The caterpillars, in return, reward the ants by providing attractive secretions from specialized glands in their cuticle. The prevalence of caterpillar-ant associations in the species rich Lycaenidae is in contrast with other Lepidoptera, where ant association appears only as isolated cases in otherwise non ant-associated lineages. This has led to the proposal that ant association may have influenced lycaenid diversification or even enhanced the rates of speciation in the group. In contrast, facultative ant-associated butterflies exhibit high levels of host plant integrity, so it is reasonable to assume that host plants may have played a significant role in their diversification. Since the influence of ants (or plants) on diversification is independent of geographic speciation modes such as vicariance or peripheral isolates, there is an underlying inference of sympatric speciation. Certain prerequisites thought to be important for sympatric speciation, such as mating on the host plant (or in the presence of the appropriate ant) as well as ant dependent oviposition preferences are characteristic of many obligate myrmecophiles. Not surprisingly, it has been suggested that evidence for sympatric speciation is more likely to be found in the Insecta since this additional mode of diversification could account for the large numbers of insect species. This thesis tested the diversification processes in obligate and facultative ant associated lycaenids using comparative methodologies in hierarchical molecular phylogenetic analyses. First, several hypotheses relating to the influence of ants on diversification in obligately ant associated lycaenid butterflies were tested in a phylogeographic analysis of the Australian endemic Jalmenus evagoras. The phylogeographic analysis revealed that regional isolation of butterfly subpopulations coincident with locally adapted ant taxa could generate a phylogenetic pattern in which related lycaenids would be seen to associate with related or ecologically similar ants. Likewise, ecological shifts in habitat preferences by lycaenids could lead to co-diversification with habitat specialist ants, even though in both cases, the ants may play only an incidental role in the diversification process. A comparative methodology was then applied in a molecular phylogenetic analysis of the genus Jalmenus to test for a signal of diversification consistent with shifts in ant partners, and to infer the processes by which ants could influence speciation. Several other specific hypotheses relating to monophyly and taxonomy were also examined. Comparative analysis of the Jalmenus phylogeny found that attendant ant shifts coincided with high levels of sympatry among sister species. This pattern could be explained by sympatric speciation; however, data suggested it was more likely that ant shifts occurred during butterfly population expansions as a result of vegetation and climate changes in the Pleistocene. Fragmentation of populations associating with novel ants could promote rapid ecological and behavioural changes and this could result in reproductive isolation of conspecifics when in secondary contact. Diversification would then continue in sympatry. In contrast, secondary contact of populations associating with the same ant species would result in homogenisation of the two lycaenid lineages or the extinction of one. A phylogeographic analysis of the facultative myrmecophiles, Theclinesthes albocincta/T. hesperia, was then undertaken to infer the evolutionary processes (such as the effects of host plant shifts) that could result in extant demographics. Species-specific questions of taxonomy, relative population ages and dispersal routes in arid Australia were also addressed. Results from the analysis suggested the two taxa were conspecific and had diversified in the late Pleistocene as a consequence of isolation in refugia in and around the arid areas of mainland Australia. However, as was the case in the J. evagoras population analysis in which attendant ant shifts were not detected, host plant shifts were not detected in the population analysis of T. albocincta/hesperia. Host plant or attendant ant shifts manifest more frequently at the species level, thus it was necessary to test the influence of host plant shifts at this higher level. The comparative methodology was then applied to a molecular phylogenetic analysis of the facultative ant-associated section Theclinesthes (comprising Theclinesthes, Sahulana and Neolucia) to test for modes of diversification consistent with host plant shifts. The relative importance of other influences on diversification was also assessed. Akin to the Jalmenus analysis, the prediction that sister species ranges should broadly overlap when a shift in host plants had taken place was upheld in the comparative analysis. Species in the genera Jalmenus and Theclinesthes were found to have diversified in the Pleistocene so were subject to the same climatic oscillations that influenced patterns of vegetation expansion and contraction across much of Australia. Thus, the similarity and predictability of relationships in the comparative analyses based on biological data suggested that host plant shifts have influenced diversification in facultative myrmecophiles by inhibiting gene flow in secondary contact in similar fashion to that of attendant ant shifts identified in the Jalmenus phylogeny. Interpretation of data in these analyses suggested that allopatric diversification was the most common mode of speciation. Isolation was inferred to be the result of fragmentation following long distance dispersal across wide expanses of marginal habitat, or vicariance following the closing of biogeographical barriers. However, attendant-ant and host-plant shifts clearly played an important role in the diversification process, and in the maintenance of species integrity among lycaenid butterflies. Furthermore, exceptions to the predicted patterns of range overlap and ecological shifts provided clues to additional modes of diversification including shifts in habitat preferences and an unusual temporal shift following changes in specific host plant phenology resulting in allochronic diversification. Inferring modes of diversification using comparative methods based on range overlap and biological traits in a phylogenetic context is not new; however, the interpretation presented in this thesis is in contrast with contemporary methods. It is clear that the patterns of species range overlap and the ecological preferences of sister taxa are intimately related among lycaenid species that diversified during the Pleistocene. As a result, different influences on diversification can be highlighted in phylogenies when applying existing comparative methodologies but without necessarily drawing the same conclusions about modes of diversification. A more inclusive explanation for patterns of range overlap among sister taxa is detailed, a consequence of which is a method for estimating rates of extinction in a phylogeny where comprehensive distributional, biological and taxonomic data are available. These patterns and predictions may be applicable to a range of taxa, especially those that have diversified in the Pleistocene. Plans for future studies are outlined.

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4

Eastwood, Rodney Gordon. "Ant Association and Speciation in Lycaenidae (Lepidoptera): Consequences of Novel Adaptations and Pleistocene Climate Changes." Thesis, Griffith University, 2006. http://hdl.handle.net/10072/365668.

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Abstract:

The butterfly family Lycaenidae (including the Riodinidae) contains an estimated 30% of all butterfly species and exhibits a diverse array of life history strategies. The early stages of most lycaenids associate with ants to varying degrees, ranging from casual facultative coexistence through to obligate association where the long-term survival of the butterfly is dependent on the presence of its attendant ants. Attendant ants guard the butterflies against predators and parasites during their vulnerable period of larval growth and pupation. The caterpillars, in return, reward the ants by providing attractive secretions from specialized glands in their cuticle. The prevalence of caterpillar-ant associations in the species rich Lycaenidae is in contrast with other Lepidoptera, where ant association appears only as isolated cases in otherwise non ant-associated lineages. This has led to the proposal that ant association may have influenced lycaenid diversification or even enhanced the rates of speciation in the group. In contrast, facultative ant-associated butterflies exhibit high levels of host plant integrity, so it is reasonable to assume that host plants may have played a significant role in their diversification. Since the influence of ants (or plants) on diversification is independent of geographic speciation modes such as vicariance or peripheral isolates, there is an underlying inference of sympatric speciation. Certain prerequisites thought to be important for sympatric speciation, such as mating on the host plant (or in the presence of the appropriate ant) as well as ant dependent oviposition preferences are characteristic of many obligate myrmecophiles. Not surprisingly, it has been suggested that evidence for sympatric speciation is more likely to be found in the Insecta since this additional mode of diversification could account for the large numbers of insect species. This thesis tested the diversification processes in obligate and facultative ant associated lycaenids using comparative methodologies in hierarchical molecular phylogenetic analyses. First, several hypotheses relating to the influence of ants on diversification in obligately ant associated lycaenid butterflies were tested in a phylogeographic analysis of the Australian endemic Jalmenus evagoras. The phylogeographic analysis revealed that regional isolation of butterfly subpopulations coincident with locally adapted ant taxa could generate a phylogenetic pattern in which related lycaenids would be seen to associate with related or ecologically similar ants. Likewise, ecological shifts in habitat preferences by lycaenids could lead to co-diversification with habitat specialist ants, even though in both cases, the ants may play only an incidental role in the diversification process. A comparative methodology was then applied in a molecular phylogenetic analysis of the genus Jalmenus to test for a signal of diversification consistent with shifts in ant partners, and to infer the processes by which ants could influence speciation. Several other specific hypotheses relating to monophyly and taxonomy were also examined. Comparative analysis of the Jalmenus phylogeny found that attendant ant shifts coincided with high levels of sympatry among sister species. This pattern could be explained by sympatric speciation; however, data suggested it was more likely that ant shifts occurred during butterfly population expansions as a result of vegetation and climate changes in the Pleistocene. Fragmentation of populations associating with novel ants could promote rapid ecological and behavioural changes and this could result in reproductive isolation of conspecifics when in secondary contact. Diversification would then continue in sympatry. In contrast, secondary contact of populations associating with the same ant species would result in homogenisation of the two lycaenid lineages or the extinction of one. A phylogeographic analysis of the facultative myrmecophiles, Theclinesthes albocincta/T. hesperia, was then undertaken to infer the evolutionary processes (such as the effects of host plant shifts) that could result in extant demographics. Species-specific questions of taxonomy, relative population ages and dispersal routes in arid Australia were also addressed. Results from the analysis suggested the two taxa were conspecific and had diversified in the late Pleistocene as a consequence of isolation in refugia in and around the arid areas of mainland Australia. However, as was the case in the J. evagoras population analysis in which attendant ant shifts were not detected, host plant shifts were not detected in the population analysis of T. albocincta/hesperia. Host plant or attendant ant shifts manifest more frequently at the species level, thus it was necessary to test the influence of host plant shifts at this higher level. The comparative methodology was then applied to a molecular phylogenetic analysis of the facultative ant-associated section Theclinesthes (comprising Theclinesthes, Sahulana and Neolucia) to test for modes of diversification consistent with host plant shifts. The relative importance of other influences on diversification was also assessed. Akin to the Jalmenus analysis, the prediction that sister species ranges should broadly overlap when a shift in host plants had taken place was upheld in the comparative analysis. Species in the genera Jalmenus and Theclinesthes were found to have diversified in the Pleistocene so were subject to the same climatic oscillations that influenced patterns of vegetation expansion and contraction across much of Australia. Thus, the similarity and predictability of relationships in the comparative analyses based on biological data suggested that host plant shifts have influenced diversification in facultative myrmecophiles by inhibiting gene flow in secondary contact in similar fashion to that of attendant ant shifts identified in the Jalmenus phylogeny. Interpretation of data in these analyses suggested that allopatric diversification was the most common mode of speciation. Isolation was inferred to be the result of fragmentation following long distance dispersal across wide expanses of marginal habitat, or vicariance following the closing of biogeographical barriers. However, attendant-ant and host-plant shifts clearly played an important role in the diversification process, and in the maintenance of species integrity among lycaenid butterflies. Furthermore, exceptions to the predicted patterns of range overlap and ecological shifts provided clues to additional modes of diversification including shifts in habitat preferences and an unusual temporal shift following changes in specific host plant phenology resulting in allochronic diversification. Inferring modes of diversification using comparative methods based on range overlap and biological traits in a phylogenetic context is not new; however, the interpretation presented in this thesis is in contrast with contemporary methods. It is clear that the patterns of species range overlap and the ecological preferences of sister taxa are intimately related among lycaenid species that diversified during the Pleistocene. As a result, different influences on diversification can be highlighted in phylogenies when applying existing comparative methodologies but without necessarily drawing the same conclusions about modes of diversification. A more inclusive explanation for patterns of range overlap among sister taxa is detailed, a consequence of which is a method for estimating rates of extinction in a phylogeny where comprehensive distributional, biological and taxonomic data are available. These patterns and predictions may be applicable to a range of taxa, especially those that have diversified in the Pleistocene. Plans for future studies are outlined.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Australian School of Environmental Studies
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5

Muteveri, Tinashe. "Effect of pleistocene climatic changes on the evolutionary history of South African intertidal gastropods." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/79791.

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Thesis (PhD)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: Historical vicariant processes due to glaciations, resulting from the large-scale environmental changes during the Pleistocene (0.012-2.6 million years ago, Mya), have had significant impacts on the geographic distribution of species, especially also in marine systems. The motivation for this study was to provide novel information that would enhance ongoing efforts to understand the patterns of biodiversity on the South African coast and to infer the abiotic processes that played a role in shaping the evolution of taxa confined to this region. The principal objective of this study was to explore the effect of Pleistocene climate changes on South Africa′s marine biodiversity using five intertidal gastropods (comprising four rocky shore species Turbo sarmaticus, Oxystele sinensis, Oxystele tigrina, Oxystele variegata, and one sandy shore species Bullia rhodostoma) as indicator species. Sequence data obtained from partial segments of the mitochondrial cytochrome oxidase c subunit 1 (COI), and the nuclear ribosomal DNA (encompassing part of 5.8S, second Internal Transcribed Spacer and part of 28S, hereinafter called ITS2; or comprising part of the first Internal Transcribed Spacer, 5.8S, second Internal Transcribed Spacer and part of 28S, hereinafter called ITS), were used as genetic markers to construct phylogeographic patterns and to investigate demographic histories of the taxa. Population structure was investigated using haplotype network analyses, pairwise ΦST statistics, analysis of molecular variance (AMOVA), isolation by distance analyses, Bayesian analysis of population structure (BAPS) and coalescent analysis of gene flow. Demographic history was analysed through Fu′s Fs tests, mismatch distributions, and Bayesian skyline plots. Demographic analyses suggest that all five intertidal gastropods studied experienced demographic expansions dating to the late Pleistocene. The sandy shore direct developer B. rhodostoma began expansion after the LGM (c. 15 kya) whereas for the four rocky shore broadcast spawners (T. sarmaticus, O. sinensis, O. tigrina, and O. variegata) the onset of expansion coincided with or preceded the LGM (c. 25, 60, 50, 40 kya, respectively). Consistent with recent range expansions and gene flow patterns, the population genetic structure in all species was characterised by shallow or a lack of population differentiation. Oxystele variegata was an exception as it showed a deep disjunction, of late Pleistocene origin, between individuals in the west coast Namaqua Bioregion and those in the south coast Agulhas Bioregion. These results provide strong evidence of the vital role that Pleistocene climatic changes and current regimes played in shaping the nature and distribution of biodiversity on the South African coast. In addition, gene flow in all species, except O. tigrina, was remarkably asymmetrical with the regions around Cape Infanta and Port Elizabeth acting as source populations. Considering the generally weak population genetic structure and gene flow patterns detected for most gastropod species studied here, it is recommended that T. sarmaticus, O. sinensis, O. tigrina and B. rhodostoma be managed as panmictic populations, and that the region encompassing Cape Infanta, and Port Elizabeth should be prioritised for conservation as it appears to harbour source populations. Oxystele variegata was the only species showing distinct population structure and in this instance, species specific conservation efforts should recognize this divergence by treating the two genetic assemblages as distinct management units.
AFRIKAANSE OPSOMMING: Historiese vikariante prosesse kan toegeskryf word aan glasiasie, en het tot gevolg gehad dat grootskaalse veranderinge in die omgewing plaasgevind het tydens die Pleistoseen (,012 - 2.6 miljoen jaar gelede, Mjg). Dit het 'n beduidende impak gehad op die geografiese verspreiding van spesies, veral ook in die mariene stelsels. Die motivering vir hierdie studie was om nuwe data te voorsien wat sal bydrae tot die voortgesette pogings om die patrone van biodiversiteit langs die Suid-Afrikaanse kus te verstaan. Dit sou ook help om die abiotiese prosesse af te lei wat 'n rol gespeel het in die evolusie van taksa wat in hierdie streek voorkom. Die hoofdoel van hierdie studie was om die effek van die Pleistoseen klimaatsveranderinge op Suid-Afrika se mariene biodiversiteit te bepaal deur gebruik te maak van vyf intergety slak spesies as indikatore (vier wat in rotsagtige gebiede voorkom: Turbo sarmaticus, Oxystele sinensis, Oxystele tigrina, Oxystele variegata en 'n sanderige strand spesies: Bullia rhodostoma). Volgorde data verkry vanaf gedeeltelike segmente van die mitochondriale sitochroom oksidase c subeenheid 1 (COI), en die kern ribosomale DNA (bestaande uit 'n deel van 5.8S, tweede interne getranskribeerde spasieërders en 'n deel van 28S), hierna genoem ITS2 is gebruik as genetiese merkers om filogeografiese patrone te dokumenteer en ook om die demografiese geskiedenis van die spesies te ondersoek. Bevolking struktuur is ondersoek deur gebruik te maak van haplotipe netwerk analise, paarsgewyse ΦST statistiek, analise van molekulêre variansie (AMOVA), isolasie deur afstand analise, Bayesiaanse analise van die bevolking struktuur (BAPS) en analise van gene vloei. Demografiese geskiedenis is ontleed deur Fu se Fs toetse, misparing verdelings, en Bayesiaanse luglyn kurwes. Demografiese ontleding dui daarop dat al vyf die intergety slakke wat ondersoek is demografiese uitbreidings ervaar het wat terugdateer tot die einde van die Pleistoseen. Die sanderige strand direkte ontwikkelaar, B. rhodostoma, het die uitbreiding begin na die LGM (c. 15 Kya), terwyl vir die vier rotsagtige kusbewoners wat eiers oor 'n uitgebreide gebiede versprei (T. sarmaticus, O. sinensis, O. tigrina, en O. variegata) het die aanvang van die bevolkings uitbreiding saamgeval met die laaste galsiasie of dit voorafgegaan (c. 25, 60, 50, 40 Kya, onderskeidelik). In ooreenstemming met die onlangse reeks bevolkings uitbreidings, is die bevolking genetiese struktuur in alle spesies gekenmerk deur weinig differensiasie. Oxystele variegata was 'n uitsondering en het 'n ontwrigting van laat Pleistoceen oorsprong getoon tussen individue langs die weskus Namaqua Biostreek en dié in die suid kus Agulhas biostreek. Hierdie resultate voorsien sterk bewyse van die belangrike rol wat die Pleistoseen klimaatsveranderinge gespeel het in die vorming en verspreiding van biodiversiteit langs die Suid-Afrikaanse kus. Daarbenewens, geen vloei in alle spesies, behalwe O. tigrina, was merkwaardig asimmetries. Kaap Infanta en Port Elizabeth verteenwoordig moontlik die bron bevolkings. Met inagneming van die geringe bevolking genetiese struktuur en geenvloei patrone wat waargeneem is vir die meeste slak spesies wat bestudeer is, word dit aanbeveel dat T. sarmaticus, O. sinensis, O. tigrina en B. rhodostoma bestuur word as 'n panmiktiese bevolking, en dat die streek wat Kaap Infanta en Port Elizabeth insluit geprioritiseer moet word vir bewaring. Oxystele variegata was die enigste spesie wat duidelike bevolking struktuur getoon het en in hierdie geval, moet spesie spesifieke bewaringspogings aangewend word.

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Heard, Joshua Andrews. "Late Pleistocene and Holocene Aged Glacial and Climatic Reconstructions in the Goat Rocks Wilderness, Washington, United States." PDXScholar, 2012. https://pdxscholar.library.pdx.edu/open_access_etds/557.

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Eight glaciers, covering an area of 1.63 km2, reside on the northern and northeastern slopes of the Goat Rocks tallest peaks in the Cascades of central Washington. At least three glacial stands occurred downstream from these glaciers. Closest to modern glacier termini are Little Ice Age (LIA) moraines that were deposited between 1870 and 1899 AD, according to the lichenometric analysis. They are characterized by sharp, minimally eroded crests, little to no soil cover, and minimal vegetation cover. Glacier reconstructions indicate that LIA glaciers covered 8.29 km2, 76% more area than modern ice coverage. The average LIA equilibrium line altitude (ELA) of 1995 ± 70 m is ~150 m below the average modern ELA of 2149 ± 76 m. To satisfy climate conditions at the LIA ELA, the winter snow accumulation must have been 8 to 43 cm greater and mean summer temperatures 0.2 to 1.3 ºC cooler than they are now. Late Pleistocene to early Holocene (LPEH) aged moraines are located between 100 and 400 m below the LIA deposits. They have degraded moraine crests, few surface boulders, and considerable vegetation and soil cover. Volcanic ashes indicate LPEH moraines were deposited before 1480 AD while morphometric data suggest deposition during the late Pleistocene or early Holocene. The average LPEH ELA of 1904 ± 110 m is ~ 240 m and ~90 m below the modern and LIA ELAs, respectively. The climate change necessary to maintain a glacier with an ELA at that elevation for LPEH conditions requires the winter accumulation to increase by 47 to 48 cm weq and the mean summer temperature to cool by 1.4 to 1.5 ºC. Last glacial maximum (LGM) moraines are located more than 30 km downstream from modern glacial termini. They are characterized by hummocky topography, rounded moraine crests, complete vegetation cover, and well developed soil cover. Moraine morphometry, soil characteristics, and distance from modern glacial termini indicate that deposition occurred at least 15 ka BP during an expansive cooling event, the last being the LGM. The LGM ELA of 1230 m is ~920 m below the modern ELA. The climate change necessary to maintain a glacier with an ELA at that elevation for LGM conditions requires the mean summer temperature to cool by 5.6 ºC with no change in precipitation.

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Rech, André Rodrigo 1985. "Walking through the flower fields = the role of time and space on the evolution of pollination strategies." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/315723.

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Orientadores: Marlies Sazima, Jeff Ollerton
Texto em português e inglês
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Os padrões encontrados em ecologia são resultado de processos contemporâneos interagindo com uma longa história de contingência. No entanto, poucos estudos têm buscado entender o papel relativo de fatores contemporâneos e pretéritos sobre padrões reprodutivos de plantas. No decorrer dessa tese foram consideradas essas duas dimensões (temporal e espacial) em estudos sobre polinização. A amplitude do estudo em relação ao tempo foi de horas até milênios, da mesma forma que para o espaço, para o qual se considerou desde metros até variações entre diferentes continentes na escala planetária. Os capítulos estão organizados em uma escala crescente de tempo e espaço. No primeiro capítulo foi considerada a variação fina de horas e metros no estudo sobre a polinização de algumas espécies de Davilla; nesse capítulo também são apresentados outros aspectos da história natural na família Dilleniaceae e uma abordagem filogenética para a evolução de algumas características florais. No capítulo 2, ao longo de vários anos, foi verificada a habilidade de visitantes florais depositar pólen, sua frequência e a importância de cada grupo de visitante nas flores de Knautia arvensis nesse período. O capítulo 3 demonstra variações no espaço tanto na morfologia floral e foliar como no crescimento do tubo polínico em diferentes testes de polinização, utilizando Curatella americana com populações distribuídas no Cerrado Brasileiro. No capítulo 4 é apresentada a variação espacial no sistema reprodutivo e a relação dos polinizadores com o nível de polinização cruzada e do passado climático com o nível de autopolinização espontânea, também tratando de C. americana. Para finalizar o capítulo 5 considera 50 inventários distribuidos ao redor do planeta categorizando as plantas em anemófilas ou zoófilas e demonstra o papel da precipitação (presente e passada) e da riqueza de espécies vegetais na prevalência de cada um dos modos de polinização. Como conclusão geral, fica clara a importância de se considerar as dimensões temporal e espacial nas interações entre plantas e polinizadores, a fim de entender como essas evoluem e como impactam na evolução da morfologia floral e nos sistemas de polinização
Abstract: Patterns in ecology are the products of current factors interacting with a longstanding history of contingency. Nevertheless, few studies have attempted to disentangle the contribution of past and current factors on plant reproduction patterns. Here we studied pollination considering both, spatial and temporal dimensions. Time variation goes from hours to millennia as well as space, whose importance was considered from meters to the whole planet. The chapter¿s sequence within the thesis is planned to go from the small to the large scale. We show the importance of fine grained variations such as hours and meters in the flower differentiation and pollination of two Davilla species in the chapter 1. In the chapter 2 we studied pollen deposition and visitation frequency in Knautia arvensis considering a year scale and showed the most important pollinator changing every year. In the Chapters 3 we used Curatella americana with populations studied across Brazilian Cerrado and show spatial variation in flower and leaf morphology and pollen tube growth. Chapter 4 also using C. americana shows the variation on the reproductive system across space, with cross-pollination related to pollinator availability and the level of autogamy underpinned by past climate. To finish, Chapter 5 deal with 50 community-based assessments of wind and animal pollination over the world and show the importance of precipitation (current and past) and plant species richness as major drivers of these proportion. As a general conclusion, it is clear that temporal and spatial factors cannot be ignored in spite to understand floral evolution and the interactions between plant and pollinators
Doutorado
Ecologia
Doutor em Ecologia

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Lisiecki, Lorraine E. "Paleoclimate time series : new alignment and compositing techniques, a 5.3-MYR benthic [exponents] d18O stack, and analysis of Pliocene-Pleistocene climate transitions /." View online version; access limited to Brown University users, 2005. http://wwwlib.umi.com/dissertations/fullcit/3174639.

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Furini, Paulo Roberto. "Modelagem preditiva de distribuição passada e futura de Ficus adhatodifolia Schott., Ficus insipida Willd. e Ficus citrifolia Mil. (Moraceae)." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/59/59139/tde-26052015-143536/.

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As glaciações do Quaternário moldaram os padrões filogeográficos das espécies em geral. Em algumas regiões da América do Sul, (e.g. Cerrado e Caatinga) a mudança estrutural foi mais acentuada, havendo o predomino de savanas, ao passo que em outras regiões (e.g. Amazônica e Mata Atlântica) as mudanças foram menores, formando áreas de refúgios florestais. A Modelagem Preditiva de Distribuição de espécies usa associações entre variáveis ambientais e registros de ocorrência da espécie para estimar modelos que representam as condições ambientais favoráveis à espécie. Neste trabalho foram estudadas três espécies de figueiras Neotropicais com características ecológicas distintas, representando duas linhagens filogenéticas independentes, i.e., seções Americana (Ficus citrifolia) e Pharmacosycea (Ficus adhatodifolia e Ficus insipida). Foram gerados modelos para os cenários passados (Interglacial 140.000 e Glacial 21.000 anos atrás), presente e futuro (2050 e 2070, nos cenários otimistas e pessimistas) para as três espécies estudadas usando o programa Maxent 3.3.3k. Os resultados obtidos mostram que para F. adhatodifolia as variáveis mais importantes nos modelos foram temperatura mínima do mês mais frio e precipitação do mês mais seco. Para F. insipida as variáveis mais importantes nos modelos foram temperatura mínima do mês mais frio e precipitação anual. Para F. citrifolia as variáveis mais importantes nos modelos foram temperatura mínima do mês mais frio e precipitação do mês mais chuvoso. Os modelos projetados no cenário interglacial, para as três espécies estudadas, apresentaram áreas de adequabilidade ambiental próximas ao cenário atual. Durante o período glacial F. adhatodifolia mostrou uma mudança considerável em sua área de ocorrência, ocorrendo em regiões consideradas refúgios para algumas espécies. Ficus insipida apresentou uma retração na sua adequabilidade ambiental, porém mantendo-se na região amazônica, enquanto que F. citrifolia teve um aumento na sua área de adequabilidade. Nos cenários futuros (2050 e 2070) F.adhatodifolia apresentou uma diminuição em sua área de ocorrência em ambos os cenários otimista e pessimista, F. insipida apresentou um aumento em sua área de adequabilidade ambiental e F.citrifolia apresentou uma diminuição e fragmentação na região Amazônica nos cenários otimista e pessimista de 2050 e otimista de 2070. As exigências ambientais e os possíveis padrões filogeográficos das três espécies são discutidos no contexto dos modelos preditivos gerados.
The Quaternary glaciations shaped the phylogeographic patterns of species in general. In some regions of South America (e.g.Cerrado and Caatinga) structural change was more pronounced and savannas predominated, whereas in other regions (e.g. Amazon and Atlantic Forest) changes were minor, forming areas of forest refuges. Species distribution Predictive Modeling uses associations between environmental variables and species occurrence records to estimate models that represent the environmental conditions favorable to the species. In the present study we chose three species of Neotropical Ficus with different ecological characteristics, representing two independent phylogenetic lineages, i.e., sections Americana (Ficus citrifolia) and Pharmacosycea (F.adhatodifolia and F.insipida). We generated models for the past (interglacial 140,000 years ago and Glacial 21,000 years ago), present and future scenarios (2050 and 2070 in optimistic and pessimistic scenarios) for the three study species using Maxent 3.3.3k program. Our results showed thatfor F. adhatodifolia the most important variables in the models were minimum temperature in the coldest month and precipitation in the driest month. For F.insipida the most important variables in the models were minimum temperature in the coldest month and annual precipitation. For F. citrifolia the most important variables in the models were minimum temperature in the coldest month and precipitation in the wettest month. The models designed for the interglacial stage showed areas of environmental suitability similar to the current scenario of the three species. During the glacial period F. adhatodifolia showed a considerable change in its range, occurring in regions considered refuges for some species. Ficus insipida had its environmental suitability decreased, but remained in the Amazon region, while F. citrifolia increased its area of suitability. In the future models (2050 and 2070) F.adhatodifolia showed a decrease in its range on both optimistic and pessimistic scenarios, F.insipida showed an increase in its area of environmental suitability and F.citrifolia has been decreasing and fragmentation in the Amazon region in the optimistic and pessimistic scenarios 2050 and optimistic 2070. The environmental requirements and the potential phylogeographic patterns of the study species are discussed in the context of the generated predictive models.

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Tan, Ning. "Comprendre l’évolution de la cryosphère et du climat du Pliocène à la transition Plio-Pléistocène." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLV032/document.

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Cette thèse est consacrée à l’étude de l’interaction cryosphère-climat depuis le milieu du Pliocène jusqu’au quaternaire pendant l’installation pérenne de la calotte groenlandaise. Nous étudions d’abord les causes du développement et de la disparition de l’importante mais courte glaciation qui a eu lieu pendant le stade isotopique marin M2 (MIS M23.264-¬3.312 Ma). Ensuite, dans le cadre du programme international sur la modélisation du Pliocène (PLIOMIP2), nous étudions le climat de la période chaude du Plaisancien moyen(MPWP, 3.3-3.0Ma). Enfin, la troisième période étudiée est la transition Plio-Pléistocène transition (PPT, 3.0-2.5Ma), que nous avons étudiée grâce à un couplage asynchrone entre un modèle de climat et un modèle de calotte. A travers ces différentes périodes, nous avons amélioré la connaissance des relations entrepCO2, tectonique et climat pendant la transition d’un monde chaud et riche en CO2 vers le monde bien plus froid et à faible pCO2 des glaciations quaternaires. Ce résultat montre l’importance de mieux comprendre les relations entre dynamique océanique, pCO2 et climat
This thesis is devoted tounderstanding the interaction betweencryosphere and climate from the mid Plioceneto the early Quaternary during the onset ofNorthern Hemisphere Glaciation (NHG).Firstly, we investigate the causes for thedevelopment and decay of the large but shortliving glaciation that occurred during MarineIsotope Stage 2 (M2, 3.264-¬3.312 Ma);Secondly, in the framework of the internationalPliocene Model Intercomparison Project(PLIOMIP2), we study the climate of Mid-Piacenzian Warm Period (MPWP, 3.3-3.0Ma).Thirdly, we explore the Plio-PleistoceneTransition (PPT, 3.0-2.5Ma) with anappropriate asynchronously coupled climatecryosphere model. Through these differentperiods, we provide a better understanding ofthe relationship between pCO2, tectonics andclimat during the transition from a warm andhigh-CO2 world to the cold and low-CO2Quaternary glaciations. This work also pointsout the necessity to further study the linkbetween ocean dynamics, carbon cycle andclimate

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Missura, Ronaldo [UNESP]. "Análise morfoestratigráfica da Bacia do Ribeirão dos Poncianos - MG." Universidade Estadual Paulista (UNESP), 2005. http://hdl.handle.net/11449/95600.

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A Bacia do Ribeirão dos Poncianos, situada na região ocidental da Serra da Mantiqueira, porção Mineira. Na área são evidenciados controles estruturais que influenciam a drenagem e a disposição do relevo, bem como os depósitos fluviais encontrados na área. Estes fenômenos puderam ser comprovados pela análise dos dados morfométricos gerados nesta pesquisa. Além dos controles estruturais, também foram estudados materiais sedimentares que estruturam os colúvios existentes em algumas vertentes da área de estudo. Estes colúvios localizam-se a setores da vertente de anfiteatro suspenso desarticulado do nível de base atual e anfiteatro articulado ao nível de base. A análise das amostras destes materiais coluviais e das datas obtidas para estes indicam que são fruto de mudanças climáticas que ocorreram durante o Pleistoceno Superior. Suas origens estão vinculadas a movimentos gravitacionais lentos (colúvios) e soterramento de material vegetal (Turfeiras), os limites entre estes se fazem na forma de discordância erosiva e deposicional. Os materiais encontrados apresentam características diferenciadas o que proporcionou através de sua análise atribuir-lhes como sendo fruto de flutuação climáticas ocorridas no período Quaternário.
The Basin of Ribeirão dos Poncianos, located on ocidental Serra da Mantiqueira, Minas Gerais side. The area show evidences of structural controls on drainage, relief and, fluvial deposits. This process could be proved by the analysis of morphometrical data produced in this research. Moreover the structural controls, also studied the sedimentary materials that structured the coluvium that appear in some slopes on the area. This colluvials material is located in sectors of slope of hollows unlinked to current base level and hollow linked to base level. The analyses of colluvial samples and the ages of this materials indicate that is consequence of climatic changes that occur during Upper Pleistocene. The materials origin its linked to gravitational slow movements (colluvium) and buried organic materials (peat), the limits between this materials is made by erosive and depositional discordance. The materials founded show differentiated characteristics that provided by the analysis to attribute than like a results of climatic changes occurred at Quaternary period.

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Hocknull, Scott Alexander Biological Earth &amp Environmental Sciences Faculty of Science UNSW. "Late Cainozoic rainforest vertebrates from Australopapua: evolution, biogeography and extinction." Awarded by:University of New South Wales. Biological, Earth & Environmental Sciences, 2009. http://handle.unsw.edu.au/1959.4/44580.

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Understanding the evolution, biogeography and extinction of Australopapuan vertebrate lineages is fundamental to determining baseline responses of those groups to past environmental change. In light of predicted climatic change and anthropogenic impact, it is imperative to determine the trajectories of Australia???s modern flora and fauna. In particular, mesothermic rainforest faunas are among Australia???s most vulnerable terrestrial biota under threat from both natural and anthropogenic causes. There is a gap in knowledge of past patterns of change and, in particular, a conspicuous lack of direct evidence of response of rainforest faunas to past climatic change. This study documents the late Cainozoic Australopapuan rainforest vertebrate record and its response to environmental change via adaptive radiation, biogeographical change and extinction. In particular, it provides the first detailed systematic appraisal of Quaternary fossil sites and local faunas from northern Australia. The study documents the only known Quaternary mesothermic rainforest fauna in Australia and its transition to a xeric-adapted fauna during the middle Pleistocene. The fossil assemblages analysed are comprised of dozens of species, including several new genera and species. Each fossil taxon shares a close phylogenetic relationship with others either known only from the Australian Tertiary record or from Quaternary-Recent New Guinea and Wet Tropics rainforests. The presence of many species is evidence of previously much larger distributions followed by subsequent massive range retractions. Detailed documentation of this rare fauna testifies to rainforest stability in central eastern Queensland until approximately 280,000 years ago, when the development of an El Nino dominated climate generated variable climatic patterns that could not support aeseasonal rainforest. Extinction of this late Pleistocene rainforest fauna serves as one of only two examples of major rainforest faunal turnover in Cainozoic Australia, the other occurring in the late Miocene. These two major extinction events are compared. The late Pleistocene faunal extinction differs from the late Miocene event in being biased towards large-bodied, terrestrial herbivores and carnivores (both reptile and mammal). This study also combines fossil and phylogenetic data with latest understanding of palaeogeography, tectonics and sea level history along Australia???s northern margin to provide hypotheses of faunal dispersal between New Guinea and mainland Australia throughout the Neogene.

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McGarry, Siobhan Frances. "Multi-proxy Quaternary palaeoenvironmental records from speleothem pollen and organic acid fluorescence." Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341161.

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Price, Gilbert J. "Pleistocene palaeoecology of the eastern Darling Downs." Thesis, Queensland University of Technology, 2006. https://eprints.qut.edu.au/16271/1/Gilbert_Price_Thesis.pdf.

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Several late Pleistocene fossil localities in the Kings Creek catchment, Darling Downs, southeastern Queensland, Australia, were examined in detail to establish an accurate, dated palaeoecological record for the region, and to test human versus climate change megafauna extinction hypotheses. Accelerator Mass Spectrometry (AMS 14C) and U/Th dating confirm that the deposits are late Pleistocene in age, but the dates obtained from the two methods are not in agreement. Fluvial depositional accumulation processes in the catchment reflect both high-energy channel and low-energy episodic overbank deposition. The most striking taphonomic observations for vertebrates in the deposits include: 1) low representation of post-cranial elements; 2) high degree of bone breakage; 3) variable abrasion but most identifiable bone elements with low to moderate degree of abrasion; 4) low rates of bone weathering; 5) low degree of carnivore bone modification; and 6) low degree of articulated or associated specimens. Collectively, those data suggest that the material was transported into the deposit from the surrounding proximal floodplain and that the assemblages reflect hydraulic sorting. A multifaceted palaeoecological investigation revealed significant habitat change between superposed assemblages of site QML796. The basal fossiliferous unit contained species that indicate the presence of a mosaic of habitats including riparian vegetation, vine thickets, scrubland, open and closed woodlands, and open grasslands during the late Pleistocene. Those woody and scrubby habitats contracted over the period of deposition so that by the time of deposition of the youngest horizon, the creek sampled a more open type environment. Sequential faunal horizons show a step-wise decrease in taxonomic diversity that cannot be explained by sampling or taphonomic bias. The decreasing diversity includes loss of some, but not all, megafauna and is consistent with a progressive local loss of megafauna in the catchment over an extended interval of time. Collectively, those data are consistent with a climatic cause of megafauna extinction, and no specific evidence was found to support human involvement in the local extinctions. Better dating of the deposits is critically important, as a secure chronology would have significant implications regarding the continent-wide extinction of the Australian megafauna.

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Price, Gilbert J. "Pleistocene palaeoecology of the eastern Darling Downs." Queensland University of Technology, 2006. http://eprints.qut.edu.au/16271/.

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Several late Pleistocene fossil localities in the Kings Creek catchment, Darling Downs, southeastern Queensland, Australia, were examined in detail to establish an accurate, dated palaeoecological record for the region, and to test human versus climate change megafauna extinction hypotheses. Accelerator Mass Spectrometry (AMS 14C) and U/Th dating confirm that the deposits are late Pleistocene in age, but the dates obtained from the two methods are not in agreement. Fluvial depositional accumulation processes in the catchment reflect both high-energy channel and low-energy episodic overbank deposition. The most striking taphonomic observations for vertebrates in the deposits include: 1) low representation of post-cranial elements; 2) high degree of bone breakage; 3) variable abrasion but most identifiable bone elements with low to moderate degree of abrasion; 4) low rates of bone weathering; 5) low degree of carnivore bone modification; and 6) low degree of articulated or associated specimens. Collectively, those data suggest that the material was transported into the deposit from the surrounding proximal floodplain and that the assemblages reflect hydraulic sorting. A multifaceted palaeoecological investigation revealed significant habitat change between superposed assemblages of site QML796. The basal fossiliferous unit contained species that indicate the presence of a mosaic of habitats including riparian vegetation, vine thickets, scrubland, open and closed woodlands, and open grasslands during the late Pleistocene. Those woody and scrubby habitats contracted over the period of deposition so that by the time of deposition of the youngest horizon, the creek sampled a more open type environment. Sequential faunal horizons show a step-wise decrease in taxonomic diversity that cannot be explained by sampling or taphonomic bias. The decreasing diversity includes loss of some, but not all, megafauna and is consistent with a progressive local loss of megafauna in the catchment over an extended interval of time. Collectively, those data are consistent with a climatic cause of megafauna extinction, and no specific evidence was found to support human involvement in the local extinctions. Better dating of the deposits is critically important, as a secure chronology would have significant implications regarding the continent-wide extinction of the Australian megafauna.

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Grant, Katharine M. "Sea-level change, monsoon variability, and eastern Mediterranean climate over the Late Pleistocene." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/362005/.

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A new, radiometrically constrained chronology is developed for a continuous, highresolution relative sea-level (RSL) record from the Red Sea that spans the past 500,000 years (500 ka BP). The method is based on indirect correlation of the RSL record with speleothem δ18O records from Soreq cave, Israel (for the period 0-150 ka BP), and from Sanbao Cave, China (for the period 150-500 ka BP). The new RSL record allows ice-volume (sea-level) phase relationships with key climate-system variables to be examined, without bias from icecore or orbital timescales. The effects of ice-volume changes on monsoon variability are also examined. In a separate development, the Soreq-synchronised interval of the RSL record is used to produce residual oxygen isotope (δ18O) records for the eastern Mediterranean; these represent regional environmental signals which are unbiased by ice-volume and sourcewater effects. Results suggest that, over the last glacial cycle, changes in polar climate and ice-volume were tightly coupled, with centennial-scale response times, and rates of sea-level rise reached at least 1.2 m per century during periods of significant ice-volume reduction. Results also suggest that, at the last five glacial terminations, ice-volume changes generally lagged insolation and atmospheric CO2 rises by ~2-7 kyr. This supports the Milankovitch theory of ice-age cycles, and disputes suggestions that CO2-driven feedback processes initiated glacial terminations. It is shown that ice-volume changes can partly explain East Asian monsoon (EAM) variability. In particular, rapid rates of ice-volume reduction at glacial terminations can account for rapid, millennial-scale variability in summer and winter EAM proxies. This observation is consistent with meltwater pulses into the North Atlantic at terminations leading to a delayed intensification of the summer EAM. Evidence also suggests that changes in different monsoon systems of the northern hemisphere were synchronous during periods of ice-volume minima. Regarding the East African summer monsoon (EAfSM), no systematic phasing is observed between precession minima and EAfSM maxima, and so the common use of a 3-kyr lag to date EAfSM records appears to be too generalised. The new palaeo-environmental reconstructions for the Mediterranean presented here suggest that local precipitation did not increase substantially during the deposition of sapropels S1, S3 and S4, whereas net moisture availability may have been elevated during the interval of sapropel S5 deposition, and within colder glacial periods of the last glacial cycle. The most climatically variable period of the last glacial cycle in the Mediterranean (~30-60 ka BP) coincides with marine isotope stage (MIS) 3.

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Jones, Andrew G. "Testing the Freshwater Routing Hypothesis for Abrupt Climate Change with a Hudson River Paleodischarge Record." Thesis, Boston College, 2015. http://hdl.handle.net/2345/bc-ir:104217.

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Thesis advisor: Jeremy Shakun
The mechanisms of abrupt climate change during the last glacial period are not yet fully understood. The objective of this research is to use oxygen isotope and magnesium/calcium ratios from foraminifera in a marine sediment core <200 km southeast of New York City (Ocean Drilling Program 174 Site 1073A) to test the hypothesis that changes in freshwater run-off patterns during intermediate extensions of the Laurentide Ice Sheet caused abrupt climate change by disrupting the Atlantic thermohaline circulation. The combination of foraminiferal δ18O and Mg/Ca yields salinity as an isolated variable, which is used as a proxy for Hudson River discharge through ~42,000-28,000 years ago. This thesis reviews the literature on abrupt climate change and compares the Hudson River paleodischarge record to established records of abrupt climate events observed in Greenland ice cores. It concludes that a higher resolution of data points is required to evaluate the impact of Hudson River discharge on abrupt climate change
Thesis (BS) — Boston College, 2015
Submitted to: Boston College. College of Arts and Sciences
Discipline: Departmental Honors
Discipline: Earth and Environmental Sciences

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Baxstrom, Kelli W. "Climate and Vegetation Change in Late Pleistocene Central Appalachia: Evidence fromStalagmites and Lake Cores." Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1554978401327246.

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Lang, David. "Continental climate and ocean circulation change during the Pliocene-Pleistocene intensification of Northern Hemisphere Glaciation." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/385217/.

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The overall aim of this thesis, comprising three main chapters, is to investigate the characteristics and mechanisms of climate change across the Pliocene-Pleistocene intensification of Northern Hemisphere Glaciation (iNHG) through the application of geochemical techniques to sediment cores with high rates of accumulation from the North Atlantic Ocean. Chapter 3 assesses the origin of sediment colour cycles at Integrated Ocean Drilling Program Site U1313 (41°N, 3.4 km water depth) that show a remarkable correlation with global climate variability over the past 5 million years. The work presented shows that these cycles are controlled by variations in %CaCO3 driven by eolian dust deposition from North America not CaCO3 dissolution (the classic interpretation). Observed change at the secular timescale in a proxy record for dust accumulation from this site is consistent with wetter-than-modern conditions on North America during the warm early Pliocene. Chapter 4 presents a record of the Nd isotope composition of the deep North Atlantic (Site U1313) between 3.3 and 2.4 Ma, measured on fish debris. This represents the first orbitally resolved record of variations in water mass mixing in this region across iNHG derived using a quasi-conservative proxy. In contrast to existing benthic foraminiferal δ13C records, the Site U1313 dataset provides evidence for large glacial incursions of southern sourced water masses to the deep North Atlantic Ocean through iNHG. An important role for Atlantic meridional overturning circulation variability in amplifying glacial-interglacial cycles during this interval is inferred. Chapter 5 presents new, sub-orbitally resolved, palaeoceanographic records (Nd isotope, benthic δ18O, benthic δ13C and ice rafted debris) spanning the key Early Pleistocene glacial Marine Isotope Stage 100 (2.52 Ma) from sites situated in the deep (Site U1313, 3.4 km water depth) and intermediate (Ocean Drilling Program Site 981, 2.2 km water depth) North Atlantic. In contrast to Late Pleistocene records, Site U1313 Nd isotope measurements reveal no evidence for shoaling of North Atlantic deep water beyond the background glacial state during sub-orbital ice rafting events. At Site 981, Nd isotopes demonstrate the continuous influence of Iceland-Scotland Overflow Water (ISOW). High frequency variability in benthic δ13C at this site therefore records the changing composition of ISOW, suggesting that Dansgaard-Oeschger paced climate variability was a feature of the high northern latitudes during MIS 100 even when such variability is not expressed in deep-ocean overturning at Site U1313. Together these results provide significant insights into Pliocene-Pleistocene climate and ocean circulation change, and overturn several existing paradigms. In contrast to previous interpretations of benthic δ13C records (from which northern sourced deep water was inferred to have dominated the Pliocene to Early Pleistocene Atlantic), new Nd isotope records reveal incursions of southern sourced water, including during key glacial intervals across iNHG. These previously unobserved changes in North Atlantic overturning were likely an important feedback on atmospheric carbon dioxide decline during iNHG. Further, evidence against a Pliocene “superconveyer” helps to reconcile the paleoclimate record with numerical model expectations of future climate change. Finally the work highlights the advantages to complementing traditional palaeoclimatic/palaeoceanographic proxies with high-resolution radiogenic isotope records.

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Peryam, Thomas, and Thomas Peryam. "Sedimentation, Climate Change and Tectonics: Dynamic Stratigraphy of the Pliocene-Pleistocene Fish Creek-Vallecito Basin, California." Thesis, University of Oregon, 2012. http://hdl.handle.net/1794/12519.

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In order to better understand the interactions between climate change, landscape erosion and sedimentation, a detailed study was conducted on Plio-Pleistocene non-marine deposits of the Palm Spring Group in the Fish Creek-Vallecito basin, California, USA. Three inter-related studies focused on (1) local response to global climate change in late Pliocene-early Pleistocene time, (2) large-scale evolution of lithofacies architecture, and (3) climate modulation of late Pliocene sediment flux on Milankovitch time scales. Stable isotopes and paleosol classification reveal that between ~4.0 and 0.75 Ma, aridity increased in the study area concurrent with a shift towards a less intense and more winter-dominated precipitation regime. These changes are interpreted to reflect the long-term waning of summer monsoon precipitation in southern California. A dramatic and enigmatic reorganization of basin strata occurred at 2.9 Ma. Detailed basin analysis shows that locally-derived sediment was supplied by the predecessors of two modern drainages, Vallecito and Carrizo creeks. Initial progradation of alluvial deposits from these two sources across the Colorado River delta plain began between 4.0-3.4 Ma. At 2.9 Ma, rapid progradation of these two deposystems was coeval with emplacement of a megabreccia and transgression of Borrego Lake. My data indicate that tectonic realignments at both local and regional scales drove this reorganization. Time series analysis of rock magnetic data from a densely-sampled stratigraphic section of the lacustrine Tapiado Formation reveals that between 2.9 and ~2.75 Ma landscape denudation in the Carrizo Creek catchment was partly modulated by orbital obliquity. Peaks in landscape denudation implied by my data correspond to obliquity highs. More frequent high intensity precipitation events (i.e. monsoons and tropical storms) probably drove increased erosion during these time periods relative to obliquity lows. The breakdown of this relationship at around 2.75 Ma corresponds to a dramatic increase in northern hemisphere glaciation and may reveal a reduction in monsoonal influence in southern California. A geologic map of the Fish Creek-Vallecito basin is included as a supplemental file to this dissertation. This dissertation contains previously published and unpublished coauthored material.

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Bischoff, Juliane. "Microbial communities and their response to Pleistocene and Holocene climate variabilities in the Russian Arctic." Phd thesis, Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2013/6889/.

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The Arctic is considered as a focal region in the ongoing climate change debate. The currently observed and predicted climate warming is particularly pronounced in the high northern latitudes. Rising temperatures in the Arctic cause progressive deepening and duration of permafrost thawing during the arctic summer, creating an ‘active layer’ with high bioavailability of nutrients and labile carbon for microbial consumption. The microbial mineralization of permafrost carbon creates large amounts of greenhouse gases, including carbon dioxide and methane, which can be released to the atmosphere, creating a positive feedback to global warming. However, to date, the microbial communities that drive the overall carbon cycle and specifically methane production in the Arctic are poorly constrained. To assess how these microbial communities will respond to the predicted climate changes, such as an increase in atmospheric and soil temperatures causing increased bioavailability of organic carbon, it is necessary to investigate the current status of this environment, but also how these microbial communities reacted to climate changes in the past. This PhD thesis investigated three records from two different study sites in the Russian Arctic, including permafrost, lake shore and lake deposits from Siberia and Chukotka. A combined stratigraphic approach of microbial and molecular organic geochemical techniques were used to identify and quantify characteristic microbial gene and lipid biomarkers. Based on this data it was possible to characterize and identify the climate response of microbial communities involved in past carbon cycling during the Middle Pleistocene and the Late Pleistocene to Holocene. It is shown that previous warmer periods were associated with an expansion of bacterial and archaeal communities throughout the Russian Arctic, similar to present day conditions. Different from this situation, past glacial and stadial periods experienced a substantial decrease in the abundance of Bacteria and Archaea. This trend can also be confirmed for the community of methanogenic archaea that were highly abundant and diverse during warm and particularly wet conditions. For the terrestrial permafrost, a direct effect of the temperature on the microbial communities is likely. In contrast, it is suggested that the temperature rise in scope of the glacial-interglacial climate variations led to an increase of the primary production in the Arctic lake setting, as can be seen in the corresponding biogenic silica distribution. The availability of this algae-derived carbon is suggested to be a driver for the observed pattern in the microbial abundance. This work demonstrates the effect of climate changes on the community composition of methanogenic archae. Methanosarcina-related species were abundant throughout the Russian Arctic and were able to adapt to changing environmental conditions. In contrast, members of Methanocellales and Methanomicrobiales were not able to adapt to past climate changes. This PhD thesis provides first evidence that past climatic warming led to an increased abundance of microbial communities in the Arctic, closely linked to the cycling of carbon and methane production. With the predicted climate warming, it may, therefore, be anticipated that extensive amounts of microbial communities will develop. Increasing temperatures in the Arctic will affect the temperature sensitive parts of the current microbiological communities, possibly leading to a suppression of cold adapted species and the prevalence of methanogenic archaea that tolerate or adapt to increasing temperatures. These changes in the composition of methanogenic archaea will likely increase the methane production potential of high latitude terrestrial regions, changing the Arctic from a carbon sink to a source.
Die Arktis ist in den gegenwärtigen Diskussionen zum Klimawandel von besonderem Interesse. Die derzeitig beobachtete globale Erwärmung ist in den hohen nördlichen Breiten besonders ausgeprägt. Dies führt dazu, dass ehemals gefrorene Böden zunehmend tiefer auftauen und daher im Boden enthaltene Kohlenstoffquellen für die mikrobielle Umsetzung und Mineralisierung zur Verfügung stehen. Aufgrund dieser Prozesse entstehen klimarelevant Gase, darunter Kohlendioxid und Methan, die aus den Böden und Sedimenten freigesetzt werden können. Wenn man bedenkt, dass in den nördlichen Permafrostgebieten die Hälfte des weltweit unter der Bodenoberfläche gelagerten Kohlenstoffs gelagert ist, wird die Bedeutung dieser Region für das Verständnis des globalen Kohlenstoffkreislaufes und der möglichen Treibhaus-gasemissionen sichtbar. Trotz dieser Relevanz, sind die am Kohlenstoffumsatz beteiligten Mikroorganismen in der Arktis wenig untersucht und ihre Anpassungsfähigkeit an die gegenwärtigen Klimaveränderungen unbekannt. Die vorliegende Arbeit untersucht daher, wie sich Klimaveränderungen in der Vergangenheit auf die Anzahl und Zusammensetzung der mikrobiellen Gemeinschaften ausgewirkt haben. Dabei liegt ein besonderer Fokus auf die methanbildenden Archaeen, um das Verständnis der mikrobiellen Methandynamik zu vertiefen. Im Rahmen dieser Arbeit wurden drei Bohrkerne aus zwei verschiedenen Standorten in der russischen Arktis untersucht, darunter terrestrischer Permafrost und Seesedimente aus Sibirien und Chukotka, Russland. Mittels der Identifikation und Quantifizierung von mikrobiellen Genen und charakteristischen Bestandteilen der mikrobiellen Zellmembran war es möglich, fossile mikrobielle Gemeinschaften in Seesedimenten mit einem Alter von bis zu 480 000 Jahren und in Permafrostablagerungen mit einem Alter von bis zu 42 000 Jahren zu rekonstruieren. Es wurde gezeigt, dass es während vergangener warmen Perioden zu einem Wachstum von Bakterien und Archaeen in allen untersuchten Standorten gekommen ist. Dieser Trend konnte auch für die Gemeinschaft der methanogenen Archaeen gezeigt werden, die während warmen und insbesondere feuchten Klimabedingungen in großer Anzahl und Diversität vorhanden waren, was wiederrum Rückschlüsse auf mögliche Methanemissionen erlaubt. In den terrestrischen Permafroststandorten wird der Temperaturanstieg als direkte Ursache für die gefundene Reaktion der mikrobiellen Gemeinschaft vermutet. Im Gegenzug dazu, führte der Temperaturanstieg im untersuchten arktischen See wahrscheinlich zu einer erhöhten Primärproduktion von organischem Kohlenstoff, die wiederum das Wachstum der Mikroorganismen antrieb. Weiterhin konnte im Rahmen dieser Arbeit gezeigt werden, dass Methanosarcina-verwandte Spezies in der Russischen Arktis weit verbreitet sind und sich an veränderte Umweltbedingungen gut anpassen können. Im Gegensatz dazu stehen Vertreter von Methanocellales und Methano-microbiales, die nicht in der Lage sich an veränderte Lebensbedingungen anzupassen. Im Rahmen dieser Arbeit konnte erstmalig gezeigt werden, dass es in früheren Warmphasen zu einem vermehrten Wachstum der an der Umsetzung des organischen Kohlenstoffs beteiligten Mikroorganismen in der Russischen Arktis gekommen ist. Im Zusammenhang mit der zukünftigen Erwärmung der Arktis kann also von einer Veränderung der am Kohlenstoffkreislauf beteiligten Mikroorganismen ausgegangen werden kann. Mit den steigenden Temperaturen werden sich einige Vertreter der methanproduzierenden Mikroorganismen an die veränderten Bedingungen anpassen können, während Temperatur-empfindliche Vertreter aus dem Habitat verdrängt werden. Diese Veränderungen in der mikrobiellen Gemeinschaft können die Methanproduktion der hohen noerdlichen Breiten erhoehen und dazu beitragen, dass aus der Arktis als eine Kohlenstoffsenke eine Kohlenstoffquelle wird.

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22

Bradley, Dawn Marie. "Implications of Late Pleistocene Climatic Change on the Morphological Variations of the Neanderthal." Digital Archive @ GSU, 2006. http://digitalarchive.gsu.edu/geosciences_theses/4.

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In this research, the relationship of climatic changes between 130k to 28k years BP to concurrent morphological variations in Neanderthals was tested. Traditional anthropological studies attribute robust Neanderthal morphological traits as an adaptation to a cold environment. A database of previously completed terrestrial paleoclimatic reconstructions in Europe and the Mediterranean was compiled and used to create a series of GIS-generated timeslice maps. Regional climatic conditions were then related to changes in Neanderthal appearances, morphology and disappearances as evident in the archaeological record. To establish climatic conditions, existing studies were compiled from two regions: Europe and the Mediterranean. The European data are based on pollen assemblage sequences from terrestrial lacustrine cores. The Mediterranean data are based on established ƒÔ18O/16O and ƒÔ13C/12C maximum and minimum events recorded in speleothems. The GIS perspective allows these changes to be viewed at significant time to better correlate regional climatic changes with known Neanderthal morphological variation and to extend the investigation both temporally, including Stage 4 and Stage 5e, and geographically, into the Mediterranean from similarly completed studies.

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Wall-Palmer, Deborah. "Response of pteropod and related faunas to climate change and ocean acidification." Thesis, University of Plymouth, 2013. http://hdl.handle.net/10026.1/1398.

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Recent concern over the effects of ocean acidification upon calcifying organisms in the modern ocean has highlighted the aragonitic shelled thecosomatous pteropods as being at a high risk. Laboratory studies have shown that increased pCO2, leading to decreased pH and low carbonate concentrations, has a negative impact on the ability of pteropods to calcify and maintain their shells. This study presents the micropalaeontological analysis of marine cores from the Caribbean Sea, Mediterranean Sea and Indian Ocean. Pteropods, heteropods and planktic foraminifera were picked from samples to provide palaeoenvironmental data for each core. Determination of pteropod calcification was made using the Limacina Dissolution Index (LDX) and the average shell size of Limacina inflata specimens. Pteropod calcification indices were compared to global ice volume and Vostok atmospheric CO2 concentrations to determine any associations between climate and calcification. Results show that changes in surface ocean carbonate concentrations throughout the Late Pleistocene did affect the calcification of thecosomatous pteropods. These effects can be detected in shells from marine sediments that are located well above the aragonite lysocline and have not undergone post-depositional dissolution. The results of this study confirm the findings of laboratory studies, showing a decrease in calcification during interglacial periods, when surface ocean carbonate concentrations were lower. During glacial periods, calcification was enhanced due to the increased availability of carbonate. This trend was found in all sediments studied, indicating that the response of pteropods to past climate change is of global significance. These results demonstrate that pteropods have been negatively affected by oceanic pH levels relatively higher and changing at a lesser rate than those predicted for the 21st Century. Results also establish the use of pteropods and heteropods in reconstructing surface ocean conditions. The LDX is a fast and appropriate way of determining variations in surface water carbonate saturation. Abundances of key species were also found to constrain palaeotemperatures better than planktic foraminifera, a use which could be further developed.

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24

Pilaar, Birch Suzanne Elizabeth. "Human adaptations to climate change and sea level rise at the pleistocene-holocene transition in the Northeastern Adriatic." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607721.

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Missura, Ronaldo. "Análise morfoestratigráfica da Bacia do Ribeirão dos Poncianos - MG /." Rio Claro : [s.n.], 2005. http://hdl.handle.net/11449/95600.

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Orientador: Iandara Alves Mendes
Banca: Regina Célia de Oliveira
Banca: Cenira Maria Lupinacci da Cunha
Resumo: A Bacia do Ribeirão dos Poncianos, situada na região ocidental da Serra da Mantiqueira, porção Mineira. Na área são evidenciados controles estruturais que influenciam a drenagem e a disposição do relevo, bem como os depósitos fluviais encontrados na área. Estes fenômenos puderam ser comprovados pela análise dos dados morfométricos gerados nesta pesquisa. Além dos controles estruturais, também foram estudados materiais sedimentares que estruturam os colúvios existentes em algumas vertentes da área de estudo. Estes colúvios localizam-se a setores da vertente de anfiteatro suspenso desarticulado do nível de base atual e anfiteatro articulado ao nível de base. A análise das amostras destes materiais coluviais e das datas obtidas para estes indicam que são fruto de mudanças climáticas que ocorreram durante o Pleistoceno Superior. Suas origens estão vinculadas a movimentos gravitacionais lentos (colúvios) e soterramento de material vegetal (Turfeiras), os limites entre estes se fazem na forma de discordância erosiva e deposicional. Os materiais encontrados apresentam características diferenciadas o que proporcionou através de sua análise atribuir-lhes como sendo fruto de flutuação climáticas ocorridas no período Quaternário.
Abstract: The Basin of Ribeirão dos Poncianos, located on ocidental Serra da Mantiqueira, Minas Gerais side. The area show evidences of structural controls on drainage, relief and, fluvial deposits. This process could be proved by the analysis of morphometrical data produced in this research. Moreover the structural controls, also studied the sedimentary materials that structured the coluvium that appear in some slopes on the area. This colluvials material is located in sectors of slope of hollows unlinked to current base level and hollow linked to base level. The analyses of colluvial samples and the ages of this materials indicate that is consequence of climatic changes that occur during Upper Pleistocene. The materials origin its linked to gravitational slow movements (colluvium) and buried organic materials (peat), the limits between this materials is made by erosive and depositional discordance. The materials founded show differentiated characteristics that provided by the analysis to attribute than like a results of climatic changes occurred at Quaternary period.
Mestre

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Prieto, Alfredo, and Rafael Labarca. "The Late Pleistocene Southern Fuego-Patagonian Archaeological Sites: New Findings, New Problems." Pontificia Universidad Católica del Perú, 2014. http://repositorio.pucp.edu.pe/index/handle/123456789/113607.

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The Fuego-Patagonian Late Pleistocene archaeological sites are scarce; we have only a handful of them for understanding a periodof time that extends for about 1000 years. These deposits coincide with a period of substantial environmental changes that contributed to the extinction of megafauna in the region, as in the rest of the Americas. All sites registered are located in caves and rock shelters. Attempts to find new sites in other contexts of the region have not yet yielded the expected results. However, thanksto recent work done by paleobiologists seeking to obtain increasingly detailed records of climate change and its causes, we are ableto propose new research directions.
Los sitios arqueológicos finipleistocénicos de Fuego-Patagonia austral son bastante escasos. Se cuenta con apenas cinco de ellos para comprender un período que se extiende por cerca de 1000 años. Estos yacimientos coinciden con una etapa de cambios ambientales muy marcados y asisten a la extinción de la megafauna en la región, al igual que en el resto del continente americano. Todos ellos se ubican en cuevas y aleros rocosos. Los intentos por hallar nuevos emplazamientos en otros contextos del área no han dado los frutos esperados aún. Sin embargo, se analizan otras posibilidades de búsqueda a la luz de los resultados de los trabajos recientes de los paleobiólogos comprometidos en obtener registros cada vez más acuciosos del cambio climático y sus causas.

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Vázquez, Rivera Héctor. "Changing Climate and Geographical Patterns of Taxonomic Richness." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31721.

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The geographic variation of taxonomic richness may be directly determined by climate through contemporaneous/ecological processes, versus other (e.g., historical/evolutionary processes) that happen to be collinear with contemporaneous climate. In Chapter 1 I evaluated hypotheses from both groups of explanations in North America. If contemporaneous climate controls patterns of richness, then richness should vary with climate through time in the same way that richness varies with current climate through space. Over the last ca. 11,000 yr, richness-temperature relationships remained reasonably constant. Between 12,000 and 14,000 yr BP, when climate fluctuated rapidly, richness gradients as a function of temperature were significantly shallower. If historical climate over the last 21,000 years determines patterns of richness, then historical climate should be a better predictor of richness than contemporaneous climate. I rejected historical-climate as a better predictor of richness. Contemporaneous climate stands as the most plausible explanation for contemporaneous patterns of richness, at least over the last 11,000 yr. In Chapter two, I tested the prediction that richness of most taxa should increase with temperature in all but the warmest and driest areas. Climate warming during Pleistocene-Holocene transition led richness increases in wet areas, but richness declines in dry regions, as expected from current richness-climate relationships. A decline in small mammal species richness in Northern California since the late Pleistocene was expected from the current richness-climate relationship for this group in North America. These results contest the view that future global warming may lead to species extinction rates that would qualify as the sixth mass extinction in the history of the earth. In chapter three, I first tested the hypothesis that richness gradients mainly reflect the sum of individual species climatic tolerances. I tested this hypothesis for birds, mammals and trees native to eastern North America (ENA, where there are no major barriers to dispersal). The number of species present in any given area in ENA is usually much smaller than the number of species in the continental pool that tolerate the climatic conditions in that area. Second, I tested several explanations for patterns of unfilled potential richness. Unfilled potential richness is inconsistent with postglacial dispersal lags, climatic variability since the Last Glacial Maximum, or with biotic interactions. In contrast, unfilled richness is highly consistent with a probabilistic model of species climate occupancy. Individual species climatic tolerances is not the process generating the main current patterns of richness, nor are post-glacial dispersal lags, climatic variability since the LGM or biotic interactions. This thesis is consistent with the hypothesis that contemporaneous climate directly controls spatial patterns of richness. Generally, there seems to be little need to invoke historical processes as determinants of current gradients of richness.

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Wakefield, Amy E. "The Diatom Record of Environmental Change Across the Pliocene-Pleistocene Transition at Lake El'gygytgyn, Northeast Russia." Bowling Green State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1494764871353507.

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Martinez, Sandrine. "Palaeoecology of the Mount Etna bat fauna, coastal Eastern Queensland." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/40979/1/Sandrine_Martinez_Thesis.pdf.

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Global warming is already threatening many animal and plant communities worldwide, however, the effect of climate change on bat populations is poorly known. Understanding the factors influencing the survival of bats is crucial to their conservation, and this cannot be achieved solely by modern ecological studies. Palaeoecological investigations provide a perspective over a much longer temporal scale, allowing the understanding of the dynamic patterns that shaped the distribution of modern taxa. In this study twelve microchiropteran fossil assemblages from Mount Etna, central-eastern Queensland, ranging in age from more than 500,000 years to the present day, were investigated. The aim was to assess the responses of insectivorous bats to Quaternary environmental changes, including climatic fluctuations and recent anthropogenic impacts. In particular, this investigation focussed on the effects of increasing late Pleistocene aridity, the subsequent retraction of rainforest habitat, and the impact of cave mining following European settlement at Mount Etna. A thorough examination of the dental morphology of all available extant Australian bat taxa was conducted in order to identify the fossil taxa prior to their analysis in term of species richness and composition. This detailed odontological work provided new diagnostic dental characters for eighteen species and one genus. It also provided additional useful dental characters for three species and seven genera. This odontological analysis allowed the identification of fifteen fossil bat taxa from the Mount Etna deposits, all being representatives of extant bats, and included ten taxa identified to the species level (i.e., Macroderma gigas, Hipposideros semoni, Rhinolophus megaphyllus, Miniopterus schreibersii, Miniopterus australis, Scoteanax rueppellii, Chalinolobus gouldii, Chalinolobus dwyeri, Chalinolobus nigrogriseus and Vespadelus troughtoni) and five taxa identified to the generic level (i.e., Mormopterus, Taphozous, Nyctophilus, Scotorepens and Vespadelus). Palaeoecological analysis of the fossil taxa revealed that, unlike the non-volant mammal taxa, bats have remained essentially stable in terms of species diversity and community membership between the mid-Pleistocene rainforest habitat and the mesic habitat that occurs today in the region. The single major exception is Hipposideros semoni, which went locally extinct at Mount Etna. Additionally, while intensive mining operations resulted in the abandonment of at least one cave that served as a maternity roost in the recent past, the diversity of the Mount Etna bat fauna has not declined since European colonisation. The overall resilience through time of the bat species discussed herein is perhaps due to their unique ecological, behavioural, and physiological characteristics as well as their ability to fly, which have allowed them to successfully adapt to their changing environment. This study highlights the importance of palaeoecological analyses as a tool to gain an understanding of how bats have responded to environmental change in the past and provides valuable information for the conservation of threatened modern species, such as H. semoni.

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Mathias, Frank Furlong Jr. "A Plio-Pleistocene Record of Lacustrine Ostracodes from Butte Valley, California: Faunal Responses to Tectonic and Climatic Change." Kent State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=kent1404725598.

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31

Shackford, Julia Keegan. "Continuous Late Pleistocene Paleoclimate Record from the Southwest African Margin: A Multi-Proxy Approach." unrestricted, 2005. http://etd.gsu.edu/theses/available/etd-04212005-174202/.

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Thesis (M.S.)--Georgia State University, 2005.
Title from title screen. Beth A. Christensen, committee chair; W. Crawford Elliott, Eirik J. Krogstad, Deborah Freile, committee members. Description based on contents viewed Dec. 22, 2006. Includes bibliographical references (p. 107-112).

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Doughty, Alice Marie. "10Be Cosmogenic Exposure Ages of Late Pleistocene Moraines Near the Maryburn Gap of the Pukani Basin, New Zealand." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/DoughtyAM2008.pdf.

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Carolin, Stacy Anne. "Geochemistry of karst deposits in Borneo detailing hydroclimate variations in the Warm Pool across the late Pleistocene." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52277.

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Variability in the tropical ocean-atmospheric system causes global scale climate anomalies, most evident in the El Niño-Southern Oscillation’s coupled climate feedbacks. Despite being an area of high interest, many questions still remain regarding the west Pacific warm pool’s response to external forcing, particularly its response to increases in anthropogenic greenhouse gases. Paleoclimate reconstructions coupled with model simulations provide insight into the tropical Pacific’s role in past climate variability necessary to the development of robust climate projections. Most paleoclimate records, however, still lack the resolution, length, and chronological control to resolve rapid variability against a background of orbital-scale variations. Here we present stalagmite oxygen isotope (δ18O) reconstructions from Gunung Mulu National Park (4oN, 115oE ), in northern Borneo, that provide reproducible centennial-scale records of western Pacific hydrologic variability that are precisely U/Th-dated and continuous throughout most of the late Pleistocene (0-160 thousand years ago, kybp). The record comprises an entire glacial-interglacial cycle, which allows us to investigate orbital-scale climate forcings and compare two well-dated glacial terminations in the western tropical Pacific. The ice- volume-corrected δ18O records suggest that glacial boundary condtions, which include significantly lower atmospheric carbon dioxide levels, did not drive significant changes in Mulu rainfall δ18O. Similarly, Borneo stalagmite δ18O is poorly correlated to either global sea level shifts or Sunda Shelf areal exposure is not evident. The Borneo record does vary in phase with local mid-fall equatorial insolation, suggesting that precessional forcing may impart a strong influence on hydroclimate variability in the warm pool. This is best illustrated across Glacial Termination II, when the oscillation of equatorial fall insolation is large and out of phase with ice sheet decay. We also use a subset of well-dated, high-resolution stalagmite δ18O records from Mulu to investigate millennial-scale climate variability during Marine Isotope Stages 3-5 (30-100kybp). We find that regional convection likely decreased during the six massive iceberg discharges defined in the North Atlantic sediment records (“Heinrich events”). The inferred drying (increased stalagmite δ18O) during Heinrich events is consistent with a southward shift of the Intertropical Convergence Zone – the dominant paradigm to explain global climate anomalies originating in the north Atlantic (ref). However, any hydrologic variability related to Dansgaad-Oeschgar (D/O) events, millennial-scale sawtooth temperature anomalies of the last glacial period first evident in the Greenland ice records, is notably absent in the stalagmite records. . The Mulu stalagmite record’s absence of D/O signal, however, is in marked contrast to the regional west Pacific marine records and suggests D/O events and Heinrich events may be characterized by fundamentally different climate mechanisms and feedbacks.

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Alizadeh, Kamaleddin [Verfasser], Hermann [Akademischer Betreuer] Behling, Markus [Gutachter] Hauck, and Erwin [Gutachter] Bergmeier. "Investigating Environmental (Climate and Vegetation) Change of Eastern Amazonia During Pleistocene and Holocene Using Multi-Proxy Analysis / Kamaleddin Alizadeh ; Gutachter: Markus Hauck, Erwin Bergmeier ; Betreuer: Hermann Behling." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2018. http://d-nb.info/1150509481/34.

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Price, Catherine R. "Late Pleistocene and Early Holocene small mammals in South West Britain : environmental and taphonomic implications, and their role in archaeological research." Thesis, University of South Wales, 2001. https://pure.southwales.ac.uk/en/studentthesis/late-pleistocene-and-early-holocene-small-mammals-in-south-west-britain-environmental-and-taphonomic-implications-and-their-role-in-archaeological-research(0fdb87f2-abcf-4676-9bd3-0a23c9922caf).html.

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This project examines small mammal faunas from cave sites in south-west England and south Wales. The aims are threefold: To examine the rapid environmental changes taking place in the Late Pleistocene and early Holocene: To understand the processes by which small mammal remains were deposited in the caves examined: To demonstrate the value of small mammal studies as an archaeological tool. All identifiable small mammal remains from twelve selected sites are listed. Ten of the sites are new material. As the species examined here are seldom exploited by humans, the small mammals provide a record of the past environment unaffected by human selection of particular species, as might be the case in larger mammal assemblages. An examination of possible agents of accumulation is provided for each site to identify any bias introduced by prey selection. Reconstructions of the environment local to each cave at the time of deposition are offered. The evidence provided by the small mammals is related to the archaeological findings from each cave, to demonstrate the effect of human habitation of cave sites on the depositional and post-depositional processes shown by the microfauna. The environmental evidence provided by the study reflects a wider landscape rather than merely the immediate surroundings of the cave, and so gives a basis for human exploitation patterns in the area accessible from the cave. Reconstructions of the ecological mosaics formed by the rapidly changing climate of the period and the topographic variation around the cave sites are provided, demonstrating the potential complexity of the environment in which the humans and other fauna of the period existed. It is hoped that this will encourage archaeologists to look beyond the general division of environmental boundaries in this period, and to examine the local variation in habitat availability and use.

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Wei-Kang, Ho, and 何瑋剛. "Late Pleistocene Climate Changes of Northern Vietnam: Geochemical Characters of a Speleothem." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/60549248559606027878.

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碩士
國立臺灣大學
地質科學研究所
89
Speleothems are chemical deposits of CaCO3, usually calcite, precipitated from seepage waters derived from the overlying ground surface. Due to sufficient uranium content in speleothem, they are suitable for U-Th dating and can provide high resolution and continued paleo-environmental information up to 450ka. It can also be correlated with the other high resolution materials, such as ice cores and sediment cores drilled from deep sea. We collected a stalagmite in a cave located 40 km to the south of Hanoi, Vietnam. d13C and d18O values and trace element concentrations are conducted for this stalagmite. The age of the beginning and termination of this stalagmite are determined as 18 and 10ka respectively by U-Th dating method. Based on our results, the paleo-environmental change in north Vietnam is clearly understood. Between 11ka and 10ka, d18O values change rapidly, suggesting heavy rainfall at that time. d13C values become more negative in 17ka and 15ka, indicating that the relative abundance of two groups of plants (C3, C4) changed after LGM. The result of trace element can further explain the events identified above. The fluctuation of Mg/Sr ratios in this research have a good correlation with the change of oxygen isotope of GISP2. We can find Younger Dryas event in north Vietnam by this result. And there are two cold events in this time interval.

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Hermanowski, Barbara. "Pleistocene and Holocene environmental changes in the Brazilian Amazon region." Doctoral thesis, 2013. http://hdl.handle.net/11858/00-1735-0000-0022-5E2F-9.

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38

Lund, David Charles. "Millennial-scale surface and deep water oscillations in the N.E. Pacific : implications for late pleistocene climate change." Thesis, 1997. http://hdl.handle.net/1957/28117.

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39

Carto, Shannon Leigh. "Climate model study of the role of global climate in the late Pleistocene migration of anatomically modern humans out of Africa." Thesis, 2006. http://hdl.handle.net/1828/2114.

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According to the "Out-of-Africa 2" theory of human evolution all living humans today descend from a group of Anatomically Modern Homo sapiens or Anatomically Modem Humans that evolved in Africa 200,000 years ago and subsequently migrated out of Africa and spread into the rest of the World around 100,000 years. As a result an interest has developed in establishing a concrete theory of the factors that compelled and/or motivated our ancestors to venture out of their African origins at this time. Interestingly, the Earth's Last Glacial Cycle also dates from this period--stretching from 115,000 to 10,000 years ago. Current paleoclimate evidence suggests that the climatic repercussions of this glacial cycle in Africa resulted in a shift towards a drier and somewhat cooler climate state and the fragmentation of the formerly extensive forested African landscape. As a result, theories of early human migration have cited African climate change during the late Pleistocene as a determinant; however, the mechanisms responsible for the development of hyper-arid conditions in Africa at this time have remained unresolved. Although, past global climate change has been ascribed to changes in radiative forcing and changes in atmospheric carbon dioxide, recent paleoclimate studies have revealed that African climate is sensitive to changes in SSTs in the Atlantic, as it appears that subtropical Africa was more arid when North Atlantic sea surface temperatures (SSTs) were cold during glacial periods. The forcing mechanism believed to be responsible for the development of these cold SSTs are the so-called Heinrich Events that are documented as massive surges of icebergs (from high-latitude ice sheets) into the North Atlantic Ocean during high-latitude glaciations. These Heinrich events resulted in the release of large quantities of freshwater into the North Atlantic, which in turn led to a weakening on the global ocean thermohaline circulation and widespread cooling throughout the region. In particular, marine sediment records from the Nordic Sea document a widespread cooling and ice-rafting event that occurred around 105 kya, known as Heinrich event 9. In order to investigate the climate processes responsible for promoting cooler and drier conditions in Africa during the migration event of AMH (around 100 kya) I used the University of Victoria Earth System Climate Model (UVic ESCM) to conduct two climate model experiments that compared the global-scale response of climate at 105 kya, in particular the Atlantic Ocean and the African climate system, to: 1) orbitally-controlled solar radiation and atmospheric carbon dioxide forcing appropriate for 105 kya and 2) the combined effect of orbitally-controlled solar radiation and atmospheric carbon dioxide at 105 kya, and North Atlantic freshwater forcing. The ultimate goal of this study is to understand how low-latitude and high-latitude climate processes affect the African climate. Overall the comparative analysis of these two climate model states revealed that the complex interaction between orbitally-controlled solar radiation and atmospheric CO2 forcing at 105 kya produced a significant part of the cooling and drying in Africa at this time interval. However, the model also indicated that the climate perturbations, caused by the freshwater forcing, amplified the cooling and drying that was already taking place in Africa due to orbital and CO2 forcing. Guided by paleoclimate data, archaeological data and the results of this study, I consider it likely that the development of hyper-arid conditions in Africa around 100 kya served as the impetus for the migration event of AMH out of Africa, as these climate changes would have rendered Africa unsuitable for hominid occupation at this time. These climate model results also provide compelling evidence that high-latitude cold events, induced by Heinrich Events, are strongly covariant with African aridity, and thus provide support to previous assertions that North Atlantic climate changes can be effectively propagated throughout the globe to produce seemingly simultaneous climate change.

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Rabanus-Wallace, Mark Timothy. "Climate-driven ecological changes through the last glacial period: innovations in plant ancient DNA and stable isotope palaeoecology." Thesis, 2017. http://hdl.handle.net/2440/114508.

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The impact of climate-driven ecological changes can be understood by reconstructing the effects of past climate variation on the flora and fauna. This thesis develops and applies new methods for inferring the history of the graminoid-dominated steppes of the northern Holarctic and Patagonia as they declined during the end of the Last Glacial Period (25,000–10,000 years ago). Stable nitrogen isotope data are used to argue for the pivotal role that landscape moisture played in the decline of the Pleistocene megafauna, and a new method for inferring relative changes in plant-available moisture from herbivore collagen isotopic measurements is developed. Experimental methods for working with botanical ancient DNA are presented, tested, and used to explore the taxonomy and evolutionary histories of three ancient plant species, ultimately yielding the two oldest known draft chloroplast genome sequences, dating to between 50,000 and 80,000 years ago. The results confirm the strongly-reticulated phylogenies characteristic of plants evolved to employ great plasticity as an adaptive ability, even with minimal sexual reproduction. All new genetic methods are tested with the aid of a newly designed program SimWreck, which simulates sequence data with the known characteristics of ancient DNA.
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Biological Sciences, 2017.

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41

Marcott, Shaun Andrew. "Late Pleistocene and Holocene glacier and climate change." Thesis, 2011. http://hdl.handle.net/1957/21129.

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This dissertation presents results from three studies that address major scientific questions in glacial geology and paleoclimatology for the late Pleistocene and Holocene using relatively new geochemical and statistical techniques. Each of the studies attempts to answer a longstanding question in the respective field using geochemical or statistical methods that have not been applied to the problem thus far. A longstanding question in glaciology is the nature and mechanism of the so- called "Heinrich events" of the last ~60 ka. These massive iceberg discharge events into the North Atlantic from the partial breakup of the Laurentide Ice Sheet are identified from distinct ice rafted debris and detrital carbonate layers in marine sediment cores. The mechanism associated with the initiation of these events is commonly thought to be related to internal ice sheet instabilities. However, Heinrich events consistently occur following a long cooling trend that culminates in an extreme cold event, thus suggesting a possible triggering mechanism by climate. Recent modeling work has proposed an oceanic mechanism associated with ocean warming, but no physical evidence has been made available to date. To test this ocean-warming hypothesis, we measured temperature sensitive trace metals and stable isotopes in benthic foraminifera from a sediment core collected in the western North Atlantic that spans the last six Heinrich events and compared our results to climate model simulations using CCSM3. Our results show subsurface warming occurred prior to or coeval with nearly all of the Heinrich events of the last ~60 ka, thus implicating subsurface ocean warming as the main trigger of these rapid breakups of the Laurentide Ice Sheet. In the field of glacial geology a longstanding question has been the timing of alpine glacial advances during the Holocene. A number of studies have interpreted several Holocene glacial advances in western North America, but age control is based largely on relative dating techniques, which have been shown to be in error by up to 10,000 yrs in some cases. Based on 124 ¹⁰Be surface exposure ages from twenty cirque moraines in ten mountain ranges across western North America, glacier were retreating from moraine positions during the latest Pleistocene or earliest Holocene and not throughout the Holocene epoch as previously assumed, thus requiring a refined interpretation of Holocene glacial activity in western North America and the associated climate forcing. In the field of paleoclimatology a question regarding how global temperature varied over the entirety of the Holocene epoch has remained to be answered for some time. While many temperature reconstructions exist for the last 2000 years, a full Holocene temperature stack does not exist, despite its potential utility of putting modern climate change into a full interglacial perspective. Based on a global composite of 73 proxy based temperature record, a Holocene temperature stack was constructed and used to demonstrate that a general cooling of ~1°C has occurred from the early to mid Holocene and that centennial and millennial scale variability is modest. We account for both temperature calibration and chronologic uncertainties using a Monte Carlo based approach. Our results are consistent with prior reconstructions of the last 2000 years and now allow for a full Holocene temperature perspective for evaluation with present and future climate change.
Graduation date: 2011
Access restricted to the OSU Community, at author's request, from May 5, 2011 - May 5, 2012

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42

Griffiths, Michael Lindgren. "Late-Pleistocene climate evolution of the southern sub-equatorial tropics from east-Indonesian speleothems." Thesis, 2010. http://hdl.handle.net/1959.13/807577.

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Research Doctorate - Doctor of Philosphy (PhD)
The climate evolution of the southern sub-equatorial tropics during marine isotope stage (MIS)5a/b and the Holocene is explored using geochemical tracers from speleothems on Flores island, Indonesia. Oxygen isotope measurements from two precisely-dated stalagmites reveal that the Australian-Indonesian monsoon increased during the Younger Dryas (YD) cooling event, when Atlantic meridional overturning circulation was relatively weak. Monsoon precipitation intensified even more rapidly from 11 to 7 ka ago, when the Indonesian continental shelf was flooded by global sea-level rise. Analysis of oxygen (δ18O) and hydrogen (δD) isotope ratios from speleothem fluid inclusions shows that inclusion-δ18O values vary in phase with speleothem calcite δ18O during the Holocene, confirming that calcite δ18O primarily reflects variations in the δ18O of meteoric rainfall. Cave drip-water temperatures, reconstructed from coupled measurements of δ18O in speleothem calcite and fluid inclusions, remained relatively constant through the Holocene but were significantly cooler during the YD, consistent with the high northern latitudes. To help confirm the stable isotope records, trace elements were used to reconstruct the position of the austral summer inter-tropical convergence zone and east Indonesian rainfall variability during the Holocene. Mg/Ca and Sr/Ca ratios correlate significantly with one another, and with δ18O and δ13C, throughout the record suggesting that the trace element ratios were dominated by prior calcite precipitation, a process whereby degassing in the vadose zone during periods of low recharge causes deposition of calcite and disproportionate loss of Ca2+ ions (relative to Mg2+ and Sr2+) ‘upstream’ of the stalagmite. Comparison of speleothem δ18O time-series from Flores and Borneo shows that they vary in unison for much of the Holocene. However, there is an exception during the mid-Holocene when a distinct anomaly in δ18O in the Borneo record, possibly caused by a change in the circulation of the Australian-Indonesian summer monsoon (AISM) in response to a period of positive IOD-like conditions in the eastern Indian Ocean, occurred between the two regions. A stalagmite reconstruction of Indo-Pacific climate through the interval 84 - 91 ka shows that the lower-frequency oxygen isotope trend indicates that the AISM was largely controlled by local summer insolation during this time, while the carbon isotopes show a pattern that is closer linked with northern polar-latitude ice-core records. Most notably, an abrupt decrease in the temperature-controlled δ13C values at the MIS 5a/b transition occurs in parallel with GIS 21 in the GISP2 δ18O and CH4 records highlighting the strong connection between the IPWP and North Atlantic during the last glacial period.

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Alizadeh, Kamaleddin. "Investigating Environmental (Climate and Vegetation) Change of Eastern Amazonia During Pleistocene and Holocene Using Multi-Proxy Analysis." Doctoral thesis, 2017. http://hdl.handle.net/11858/00-1735-0000-002E-E318-8.

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44

Peerdeman, Frank M. "The Pleistocene climatic and sea-level signature of the Northeastern Australian continental margin." Phd thesis, 1993. http://hdl.handle.net/1885/139973.

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45

Doughty, Alice Marie. "¹⁰Be cosmogenic exposure ages of late pleistocene moraines near the Maryburn Gap of the Pukani Basin, New Zealand /." 2008. http://www.library.umaine.edu/theses/theses.asp?highlight=1&Cmd=abstract&ID=GEO2008-003.

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46

Teske, Peter R., Isabelle Papadopoulos, Christopher D. McQuaid, Brent K. Newman, and Nigel P. Barker. "Climate change, genetics or human choice: why were the shells of mankind’s earliest ornament larger in the Pleistocene than in the Holocene?" 2007. http://hdl.handle.net/10962/d1006001.

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The southern African tick shell, Nassarius kraussianus (Dunker, 1846), has been identified as being the earliest known ornamental object used by human beings. Shell beads dated from ~75,000 years ago (Pleistocene era) were found in a cave located on South Africa's south coast. Beads made from N. kraussianus shells have also been found in deposits in this region dating from the beginning of the Holocene era (<10,000 years ago). These younger shells were significantly smaller, a phenomenon that has been attributed to a change in human preference. We investigated two alternative hypotheses explaining the difference in shell size: a) N. kraussianus comprises at least two genetic lineages that differ in size; b) the difference in shell size is due to phenotypic plasticity and is a function of environmental conditions. To test these hypotheses, we first reconstructed the species' phylogeographic history, and second, we measured the shell sizes of extant individuals throughout South Africa. Although two genetic lineages were identified, the sharing of haplotypes between these suggests that there is no genetic basis for the size differences. Extant individuals from the cool temperate west coast had significantly larger shells than populations in the remainder of the country, suggesting that N. kraussianus grows to a larger size in colder water. The decrease in fossil shell size from Pleistocene to Holocene was likely due to increased temperatures as a result of climate change at the beginning of the present interglacial period. We hypothesise that the sizes of N. kraussianus fossil shells can therefore serve as indicators of the climatic conditions that were prevalent in a particular region at the time when they were deposited. Moreover, N. kraussianus could serve as a biomonitor to study the impacts of future climate change on coastal biota in southern Africa.

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Murad, Waheed. "Late Quaternary Vegetation History And Climate Change In The Gobi Desert, South Mongolia." Doctoral thesis, 2011. http://hdl.handle.net/11858/00-1735-0000-000D-EF60-5.

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48

Lister, Guy. "Late Pleistocene Alpine deglaciation and post-glacial climatic developments in Switzerland the record from sediments in a peri-alpine lake basin /." 1985. http://catalog.hathitrust.org/api/volumes/oclc/24036988.html.

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49

Theden-Ringl, Fenja. "Common cores in the high country. The archaeology and environmental history of the Namadgi Ranges." Phd thesis, 2018. http://hdl.handle.net/1885/149482.

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This thesis provides an update to the Aboriginal and environmental histories of the ‘high country’ in southeastern Australia from the terminal Pleistocene to the recent past. Its focus is the Namadgi Ranges, representing the northern-most outliers of the Australian Alps. The study combines archaeological excavations of rock shelter sites – from Wee Jasper in the north to the southern Namadgi valleys – with environmental reconstructions from adjacent peatlands. In a context of changing local environments, the findings provide new perspectives on when and how Aboriginal people were active in the mountains, and allow for a re-evaluation of existing archaeological models of occupation and technological change. AMS radiocarbon dates, sediment geochemistry, quantitative stone artefact analyses and other proxies contribute to solidifying the chronology and characteristics of high country habitation. Evidence of terminal Pleistocene activities is found at Wee Jasper in the Namadgi foothills, but remains elusive at higher elevations (> 1000 m). The revised datasets also reveal a previously unidentified period of low-intensity habitation across the ranges from the early to mid Holocene period (8000 to 5000 BP), possibly in response to a Holocene ‘climatic optimum’. The new evidence suggests that people may have largely abandoned the high country from 5000 or 4500 BP. From 2000 BP, however, evidence of habitation reappears, culminating in evidence for a maximum of occupation during the past 1000 years. In combination with an evaluation of known archaeological data from the high country and around its margins, the findings presented herein contradict several existing occupational and technological models, and also caution against the application of broad-scale cultural models across southeastern Australia. A regional environmental history is constructed by analyses of sediments that started to build up 16,000 years ago as the climate warmed. Fire event reconstruction based on charcoal, stratigraphic clues in peat sediments, geochemical signatures of landscape productivity and instability, and a faunal record from Wee Jasper provide a detailed record of change. Comparison of the archaeological and palaeoenvironmental datasets reveals a potential link in these two records, in the form of a tentatively identified signal of anthropogenic burning during the early to mid Holocene. More generally, the environmental history provides a backdrop of changing climates and landscape processes to which Aboriginal people adapted and responded over thousands of years.

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Dissertations / Theses on the topic 'Pleistocene Climate Changes'

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