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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Quantitative Reconstruction of the Late Miocene Monsoon Climates of Southwest China: A Case Study of the Lincang Flora From Yunnan Province

Jacques, Frédéric M.B., Guo, Shuang Xing, Su, Tao, Xing, Yao Wu, Huang, Yong Jiang, Liu, Yu Sheng, Ferguson, David K., Zhou, Zhe Kun 01 May 2011 (has links)
The Miocene Lincang leaf assemblage is used in this paper as proxy data to reconstruct the palaeoclimate of southwestern Yunnan (SW China) and the evolution of monsoon intensity. Three quantitative methods were chosen for this reconstruction, i.e. Leaf Margin Analysis (LMA), Climate Leaf Analysis Multivariate Program (CLAMP), and the Coexistence Approach (CA). These methods, however, yield inconsistent results, particularly for the precipitation, as also shown in European and other East Asian Cenozoic floras. The wide range of the reconstructed climatic parameters includes the Mean Annual Temperature (MAT) of 18.5-24.7°C and the Mean Annual Precipitation (MAP) of 1213-3711. mm. Compared with the modern Lincang climate (MAT, 17.3°C; MAP, 1178.7. mm), the Miocene climate is slightly warmer, wetter and has a higher temperature seasonality. A detailed comparison on the palaeoclimatic variables with the coeval Late Miocene Xiaolongtan flora from the eastern part of Yunnan allows us to investigate the development and interactions of both South Asian and East Asian monsoons during the Late Miocene in southwest China, now under strong influence of these monsoon systems. Our results suggest that the monsoon climate has already been established in southwest Yunnan during the Late Miocene. Furthermore, our results support that both Southeast Asian and East Asian monsoons co-occurred in Yunnan during the Late Miocene.
22

Quantitative Climate Reconstructions of the Late Miocene Xiaolongtan Megaflora from Yunnan, Southwest China

Xia, Ke, Su, Tao, Liu, Yu S., Xing, Yao W., Jacques, Frédéric M.B., Zhou, Zhe Kun 15 May 2009 (has links)
The late Miocene Xiaolongtan megaflora from Kaiyuan in southeast Yunnan (23°48′45″N, 103°11′52″E, 1050 m a.s.l.) was chosen for palaeoclimatic reconstruction using three quantitative techniques, i.e. the Coexistence Approach (CA), Leaf Margin Analysis (LMA), and the Climate-Leaf Analysis Multivariate Program (CLAMP). The reconstructed climatic parameters are also compared with those of the two adjacent Miocene floras currently available in Yunnan, i.e. the early to middle Miocene carpological Mangdan flora (24°24′N, 97°49′E, 1620 m a.s.l.) and the late Miocene Lühe palynoflora (25°10′N, 101°22′E, 1930 m a.s.l.). Quantitative analyses of the Xiaolongtan flora supports the previous qualitative results of a southern, humid subtropical climate, being more humid and having a slightly higher mean annual temperature (MAT) than today. The MATs calculated by CA, LMA, and CLAMP overlap (16.7-19.2 °C, 22.3 ± 2.05 °C, 18.1 ± 1.2 °C, respectively) and are close to the present day value (19.7 °C). The overlapping of temperatures derived using the three techniques is unusual and probably related to the low latitude of the Xiaolongtan area and the southern subtropical nature of its vegetation. Both the mean temperatures of the warmest month (WMT) and of the coldest month (CMT) reconstructed by CA (WMT = 25.4-26.0 °C, CMT = 7.7-8.7 °C) and CLAMP (WMT = 25.9 ± 1.6 °C, CMT = 10.8 ± 1.9 °C) are similar to those of today (WMT = 24.3 °C, CMT = 12.8 °C), but great changes appear in the mean annual precipitation (MAP). The CLAMP results suggest a higher precipitation (1964 ± 335.9 mm) than CA (1215-1639 mm), but they are much higher than the present MAP (820.5 mm). This is consistent with results from the Lühe palynoflora, which also developed under a warmer subtropical climate with higher precipitation (803.6-1254.7 mm) than that of today (815.9 mm). In contrast, the Mangdan flora, situated in a more complicated topographic region to the west of Xiaolongtan and near the Sino-Myanmar border, implies a slightly lower precipitation (1170-1300 mm) than that of today (1300-1400 mm). Overall, the wetter climate during the late Miocene around the Xiaolongtan area suggests that the Himalayas had not yet uplifted to its present altitudes at that time.
23

Lagerstroemia (Lythraceae) Pollen from the Miocene of Eastern China

Liu, Yu, Zetter, Reinhard, Ferguson, David K., Zou, Charley 01 December 2008 (has links)
A newly discovered fossil pollen taxon is described as Lagerstroemia cathayensis sp. nov. on the basis of a combination of morphological characters including prolate shape with no or weakly developed pseudocolpi and rugulate-verrucate tectum. The fossil pollen was recovered from a Miocene deposit in Zhejiang province, eastern China. It resembles pollen of extant Lagerstroemia subcostata Koehne and L. limii Merrill, both species still occurring near the fossil site in Zhejiang province and further extending into other regions of southern China, Japan, India and the Philippines. This record represents the only description of Cenozoic pollen grains of the genus Lagerstroemia from East Asia examined by means of scanning electron microscopy. The occurrence of Lagerstroemia together with some temperate plants (i.e. Keteleeria, Acer, Carpinus, Fagus) at the fossil site suggests that the climate in eastern China during the Miocene was similar to that of today.
24

The Anatomical Characteristics of a Giant Miocene Amphicyonid (Carnivora) Humerus From Pakistan

Viranta, Suvi, Hussain, S. Taseer, Bernor, Raymond L. 06 May 2004 (has links) (PDF)
A recently discovered distal humerus shows that very large bodied amphicyonids existed in Pakistan in the Early Miocene. Movements on their elbow joint are interpreted to be very similar to those of modern bears. They had powerful front limbs, which were probably used to grasp the prey. Taxonomic affinities of the specimen are also discussed.
25

Geology of a Vent of the Mount Dutton Formation (Miocene) Southwest Tushar Mountains, Utah

Blackman, John Tristan January 1985 (has links)
No description available.
26

Stabilní izotopy uhlíku a kyslíku ve schránkách foraminifer jako klíč k interpretaci paleoprostředí ve středním miocénu karpatské předhlubně (Centrální Paratetyda) / Carbon and Oxygen Stable Isotope Ratio from Foraminiferal Tests as a Key to the Paleoenvironmental Interpretations in the Middle Miocene of the Carpathian Foredeep (Central Paratethys)

Scheiner, Filip January 2015 (has links)
The (Lomnice) LOM-1 borehole records a nutrient-rich quiet environment of the outer shelf to upper bathyal in the Mid Badenian (sensu Hohenegger et al. (2014)) of the Carpathian Foredeep. The LOM-1 borehole is rich of a fossil content with a relatively good preservation. The studied section can be correlated with the interval from 14.6 Ma (the FO of Orbulina spp.) to 13.42 Ma (the LO of Sphenolithus heteromorphus) which agrees with the beginning of the "Middle Miocene Climate Transition". The foraminifera for the carbon and oxygen stable isotope analysis were picked from the fraction 0.063-2 mm. The suitability for the stable isotope analysis was carefully evaluated based on the inner wall preservation. The isotopic analysis was done for fifteen samples with total 373 tests analyzed. Each analysis was performed from exactly one test. The following foraminiferal genera from different paleobiotops were used for the isotope analysis: Globigerina bulloides; Orbulina universa, Praeorbulina glomerosa; Globigerinoides spp.; Uvigerina spp.; Heterolepa dutemplei; Cibicidoides spp.; Gyroidinoides spp. and Melonis pompilioides to document the isotopic signal for the superficial and bottom waters. The oxygen and carbon isotope analysis from foraminiferal tests were used for the verification of the...
27

Neogene fluvial deposits along the south-west coast of South Africa understanding the palaeoclimate through proxies

Sciscio, Lara January 2011 (has links)
Branched glycerol dialkyl glycerol tetraether (GDGTs) membrane lipids have been used as a new proxy for the reconstruction of terrestrial palaeoclimates. These biomarkers (or molecular ‗fossils‘) in conjunction with palynology, have been effective in the novel analysis of Miocene organic-rich sediments from three South African west coast sites at Rondeberg, Noordhoek and Langebaanweg. Lastly, a Quaternary south coast site at Rietvlei, South Africa, was also studied to further elucidate the extent of use of this new proxy. The fluvial peat and organic-rich deposits of the Elandsfontyn Formation (Sandveld Group) were investigated at Noordhoek, Langebaanweg and Rondeberg to provide new evidence for the climate and vegetation patterns during Miocene in this region. Drill-core and quarry samples from all four sites were freeze-dried, powered, and prepared for biogeochemical and palynological analyses. The methylation index of branched tetraethers (MBT) and cyclisation ratio of branched tetraethers (CBT) proxies were used to calculate the mean annual air temperature (MAAT) and pH values of the organic-rich horizons at time of deposition. The Branched versus isoprenoid index of tetraethers (BIT) was used to assess the relative contributions of marine archaeal and terrestrial bacterial tetraethers, and thereby assess the validity of the MBT, CBT and calculated palaeoenvironmental factors. The results presented in this thesis suggest that the use of the MBT/CBT proxy has significant potential in southern Africa, and may complement previously attempted palaeoclimatic and palaeoecological studies of Neogene-aged South African sediments. This type of research has the capacity to provide palaeoenvironmental information where other proxies may be absent. Results indicate that all sites yielded branched tetraether membrane lipids with the exception of Rondeberg, where GDGTs were below detection as a result of poor preservation conditions. Palynological investigation confirmed proxy derived temperatures. Furthermore palynomorph analyses supplemented earlier studies of the Noordhoek site and were piloted for the Rondeberg site, reaffirming alternating sequences of tropical and subtropical palynofloras. The MAATs, likewise, show variability and pronounced trends through time at the Langebaanweg and Noordhoek sites, generally corresponding with the variation and diversity of the pollen population. The terrestrial MAAT results appear to compliment Southern Hemisphere sea level changes associated with Antarctic glaciations. Additionally, this data shows a pattern similar to the Southern and Northern Hemisphere marine isotope records of relative fluctuations in the global climate and sea level change from the early to middle Miocene. The application of these past climate change indicators have been proved to be useful in the reconstruction of South Africa Miocene palaeoclimates, and may aid in understanding the consequences of climate change in the Cape region.
28

Descrição morfológica e posicionamento filogenético de um lagarto (Reptilia, Squamata) do Mioceno Inferior da Formação Chichínales, General Roca, Província de Río Negro, Argentina / Morphological description and phylogeny of a lizard (Reptilia, Squamata) from the Lower Miocene, Chichínales Formation, General Roca, Río Negro Province, Argentina

Quadros, Ana Bottallo de Aguiar 29 January 2016 (has links)
Embora os escamados sejam comumente encontrados em sítios fossilíferos cenozóicos sul−americanos, materiais esqueléticos completos são raros. Apenas alguns poucos exemplares assim foram registrados, com a maioria dos achados representando materiais fragmentários de crânio e mandíbulas ou vértebras isoladas. Dentre as localidades provedoras de vertebrados fósseis na América do Sul, a Formação Chichínales se destaca pela recente descoberta, em seus sedimentos, de um crânio quase completo de um lagarto teiídeo previamente desconhecido. Dada a fauna associada, a idade da formação é definida como Mioceno Temprano (Colhuehuapense). No presente estudo, conclui−se, através de uma análise filogenética contendo 39 espécies viventes e fósseis de escamados e 149 caracteres osteológicos, que este material pertence a uma nova espécie do gênero contemporâneo Callopistes. Uma descrição morfológica detalhada do fóssil, obtida através de análises estereoscópicas e de microtomografia computadorizada de alta resolução (CT Scan), também é apresentada. A matriz morfológica foi analisada com o auxílio do software TNT Versão 1.1, seguindo o princípio de máxima parcimônia, com todos os caracteres tratados com a mesma pesagem, resultando em quatro árvores igualmente parcimoniosas, que foram então utilizadas para a construção de uma árvore de consenso estrito. Em todas as quatro árvores, o novo táxon posicionou−se dentro da família Teiidae como um membro do clado formado pelas demais espécies viventes de Callopistes. Entretanto, não foi possível estabelecer uma relação de grupo−irmão inequívoca entre as duas espécies de Callopistes presentes na análise e o fóssil. A atual distribuição das duas espécies viventes de Callopistes e a localidade de onde foi recuperado o fóssil em estudo indicam que esse gênero possuía uma distribuição muito mais ampla no passado, chegando a áreas patagônicas cis−Andinas, diferentemente das áreas trans−Andinas de altitude onde as duas espécies atuais estão restritas / Although squamates are commonly found in most Caenozoic south american fossil beds, complete skeletal materials are rare. Only a few examples exist, with most findings representing fragmentary cranial or jaw materials or isolated vertebrae. Among the known South American vertebrate fossil localities, the Chichínales formation rendered recently a mostly complete skull of a previously unknown teiid lizard. Given the associated fauna, the age of the formation is defined as Early Miocene (Colhuehuapense). Here, I show that this fossil represents a new species of the extant genus Callopistes through a phylogenetic analysis of extant and extinct squamates that includes 39 taxa and 149 osteological characters. I also provide a detailed description of the new fossil teiid based on both stereoscopical and high-resolution X−ray computed tomography (CT Scan) analyses. The data matrix was analyzed performing a equally weighted parsimony analysis using the software TNT Version 1.1 that resulted in four equally most parsimonius trees, which were then used to built a strict consensus tree. In all four trees, the fossil lizard was recovered within the Callopistes lineage, nested inside the family Teiidae. Nevertheless, I was unable to establish which of the two Callopistes species present in the analysis were more closely related to the fossil. The present distribution of the two extant species of Callopistes and the locality from where the fossil was recovered indicate that this genus had a much broader distribution in the past, reaching cis−Andean areas of Patagonia, apart from the trans−Andean areas where the two extant species are restricted
29

Additional Research and Taxonomic Resolution of Salamanders (Amphibia: Caudata) from the Mio-Pliocene Gray Fossil Site, TN

Darcy, Hannah E 01 May 2015 (has links)
The Gray Fossil Site (GFS), a Mio-Pliocene (4.5–7 Ma) locality in the southern Appalachians, boasts the most diverse pre-Pleistocene salamander fauna in North America: Desmognathus sp., Plethodon sp., Notophthalmus sp., a Spelerpinae-type plethodontid, and Ambystoma sp. Because greater taxonomic resolution can result in more precise paleobiological interpretations, additional specimens were studied here. ETMNH 8045, a nearly complete articulated ambystomatid, appears most like Ambystoma maculatum in dentition and vertebral proportions. ETMNH 18219, an isolated vomer, is consistent with modern Pseudotriton and Gyrinophilus in possessing a postdentigerous process and a similar dentigerous row morphology. If these taxa, or species of similar ecological preferences, occurred around the GFS, it seems unlikely they co-inhabited the sinkhole lake. Aquatic stages of Pseudotriton and terrestrial Gyrinophilus last multiple years; their presence could further support a perennial lake interpretation. Modern A. maculatum preferentially breed in vernal pools; confirmed identification could suggest local seasonal wetlands.
30

Sciurids (Rodentia: Sciuridae) of the Late Mio-Pliocene Gray Fossil Site and the Late Miocene Tyner Farm: Implications on Ecology and Expansion of the Sciurid Record

Crowe, Cheyenne J 01 May 2017 (has links)
Sciurids are one of the most diverse mammalian groups today, but the fossil record does not reflect that diversity. The purpose of this project was to identify sciurids from two late Miocene sites—the Gray Fossil Site (GFS) of Tennessee, and Tyner Farm of Florida—and use those identifications to infer the ecology of the two. From the GFS four sciurids were identified: Eutamias or Neotamias, Glaucomys, and two tree squirrels (Sciurini). Two sciurids were identified from Tyner Farm: a chipmunk attributed to Tamiina, and a ground squirrel attributed to Marmotina. Paleoenvironmental inferences based on the sciurids present at both sites are consistent with previous work. The GFS Eutamias or Neotamias is the first record of a western chipmunk population in eastern North America; the GFS tree squirrels are the earliest record of a tree squirrel in eastern North America. The GFS Glaucomys is the earliest record of the genus.

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