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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.
41

Elementos para um debate sobre o clima no Éon Fanerozoico / Elements for a climate debate in the Phanerozoic Eon

Campos Junior, Newton Monteiro de 12 December 2017 (has links)
O objetivo deste trabalho de pesquisa é o de buscar entender os tempos e eventos que determinaram as grandes mudanças climáticas no Éon Fanerozoico. Técnicas são constituídas, metodologias estabelecidas, e por vezes são aceitas como sendo as verdades científicas. Com as inovações nas técnicas, com o mudar das ciências, mudam as evidências, mudam as verdades, fazendo mudar nossa percepção do passado. Este trabalho apresenta elementos para um debate sobre o clima da Terra no Fanerozoico, estabelecido a partir de pesquisas bibliográficas sobre evidências passadas e atuais. / The goal of this research work is to understand the times and events that determined the great climatic changes in the Phanerozoic Eon. Techniques are constituted, methodologies are established, and are sometimes accepted as scientific truths. With innovations in techniques, with the change of science, change the evidence; change the truths, making change our perception of the past. This paper presents elements for a discussion on the Earth\'s climate in Phanerozoic established from bibliographical research on past and current evidences.
42

Caracterização paleogeográfica de costões rochosos da porção sul do município de Ubatuba - SP / Paleogeographical characterization of rocky shores of the southern portion of the municipality of Ubatuba, SP, Brazil

Teles, Renata Diniz 06 September 2016 (has links)
como uma tarefa importante das ciências relacionadas aos ambientes litorâneos. É importante progredir com os estudos, por meio da revisão e reinterpretação dos dados já existentes e da proposição de dados adicionais que elucidem as divergências que permeiam o delineamento das curvas de variação do nível do mar na costa brasileira e melhorem o diagnostico dos paleoníveis. A importância desses pesquisas reside no fato de que as variações contribuíram diretamente na formação e evolução das áreas costeiras. O município de Ubatuba possui grande potencial para a ocorrência de indicadores biológicos e geomorfológicos de paleoníveis marinhos, ainda pouco estudados em todo o litoral paulista. Estudos prévios que encontraram paleoindicadores biológicos de variações holocênicas do NM em alguns costões rochosos de Ubatuba, são um bom exemplo desse potencial. No presente trabalho avaliou-se 3 costões no município citado, quanto a suas características geomorfológicas e geológicas, e suas potencialidades para a ocorrência de indicadores de variação do NM. Os resultados apresentados permitem concluir que esses costões apresentam características peculiares que permitem o desenvolvimento e preservação de registros de NM. Pode-se inferir que as bandas de ouriços pormenorizadas no presente estudo definem níveis marinhos pretéritos, bem como os níveis de plataformas de abrasão marinha inativas aqui caracterizados. Tanto as plataforma quanto a presença das bandas sugerem pelo menos três estabilizações de NM mais alto que o atual, o que corrobora a literatura. Para estabelecer correlações entre as áreas estudas e delas com outras áreas do município, serão necessários estudos futuros, que contemplem ainda a datação de amostras de restos biogênicos, para que se possa relacionar os dados espaciais aqui apresentados com referencias temporais. / Responding to issues related to marine paleolevels reiterated increasingly as an important task of the science related to coastal environments. It is important to make progress with the studies through the review and reinterpretation of existing data and additional data proposition elucidating the differences that permeate the design of the variation curves sea level on the Brazilian coast and improve the diagnosis of paleolevels. The importance of these studies lies in the fact that changes have contributed directly to the formation and evolution of coastal areas. The city of Ubatuba has great potential for the occurrence of biological and geomorphological indicators of marine paleolevels, still understudied throughout the São Paulo coast. Previous studies have found that biological paleoindicadores of Holocene variations of sea level in some rocky shores of Ubatuba, are a good examples of this potential. In the present study we evaluated three rocky shores in Ubatuba as its geomorphological and geological features, and its potential for the occurrence of NM variation indicators. The results allow us to conclude that these shores have peculiar characteristics that enable the development and preservation of NM records. It can be inferred that the hedgehogs bands detailed in this study define tenses sea levels as well as levels of inactive marine abrasion platforms here characterized. Both the platform and the presence of the bands suggest at least three higher NM stabilizations that the current, which corroborates the literature. To establish correlations between them and studied areas with other areas of the municipality will require further study, still contemplating the dating of samples of biogenic remains, so that you can relate to the spatial data presented herein with temporal references.
43

Correlation, Paleogeography, and Provenance of the Neoproterozoic Eastern Uinta Mountain Group, Goslin Mountain Area, Northeastern Utah

Rybczynski, Daniel J. 01 May 2009 (has links)
Geologic mapping, facies analysis, sedimentary petrography, and detrital zircon analyses of undivided eastern Uinta Mountain Group stratigraphy are presented to better understand the depositional environments and tectonic setting of the Uinta Mountain Group basin. Subdivided units have been modified and correlated from previous work and include the Red Pine Shale, Hades Pass, Crouse Canyon, Outlaw Trail, and Diamond Breaks formations. Three lower-order maximum flooding surfaces associated with the lower Outlaw Trail formation, lower Hades Pass formation, and Red Pine Shale are interpreted. The relative magnitude of each lower-order transgression increases up section along with increasing diversity of palynomorph assemblages found in organic shale intervals. Six facies associations exist within the section and are interpreted as braided fluvial conglomerate, braided fluvial sandstone and conglomerate, braided fluvial sandstone, low-energy braided fluvial sandstone, mudflat, and offshore depositional environments. Both marine and non-marine interpretations are plausible for mudflat and offshore environments; however, previous interpretations of correlative Red Pine Shale exposures suggest a marine environment. The coarsest fluvial environments are restricted to the northern half of the study area and likely coincide with proximity to a tectonically-active northern basin margin. Paleocurrent analysis and the restriction of some subaqueous deposits to the north show northward-dipping depositional slopes, which suggest a tectonic control. Provenance work suggests three general sediment sources existed: an eastern source where ~1.1 Ga and lesser ~1.4 Ga detritus dominate, an east-northeastern source where ~1.8 Ga detritus dominate, and a north-northeastern arkosic source where ~2.7 Ga detritus dominate. Results suggest that during lower-order lowstands, sediments derived from eastern sources dominate. Higher concentrations of ~1.8 Ga and ~2.7 Ga detritus is likely coincident with proximity to the northern basin margin. During lower-order highstands, eastern or northern sources may dominate; northern sources appear more prominently within the Outlaw Trail formation, while eastern sources appear more prominently within the Red Pine Shale. Reasons for this may be linked to the magnitude of the transgressive interval sampled. These relationships, in conjunction with observations of previous studies, suggest the eastern Uinta Mountain Group was deposited in a half-graben style rift, a strike-slip basin, or some combination of the two.
44

Morphology, paleogeographic setting, and origin of the Middle Wilcox Yoakum Canyon, Texas Coastal Plain

Dingus, William Frederick, 1959- 18 June 2013 (has links)
The Yoakum Canyon is the largest of the Gulf Coast Eocene erosional gorges and is interpreted as a buried submarine channel. It can be traced for 67 miles from the Wilcox fault zone, which defines the position of the early Eocene shelf edge, nearly to present outcrop. This paper expands on previously published descriptions of the canyon using a more extensive subsurface data base. Decompaction of the canyon shale-fill reveals that original depths of the canyon exceeded 3500 ft (1067 m). Apparent canyon wall slump scarps and a peripheral chaotic zone, interpreted as an incipient slump feature, are comparable to similar features of the late Quaternary Mississippi submarine canyon. The Yoakum canyon formed within the Garwood subembayment to the west of and adjacent to the Middle Wilcox continuation of the Rockdale delta system. Quantitative mapping of facies adjacent to the Yoakum shale indicate the following sequence of events: 1) Muddy, distal deltaic and shelf facies of the lower Middle Wilcox were deposited during a retrogradation. 2) A resurgence of progradation deposited the upper Middle Wilcox deltaic sands atop the unconsolidated, lower Middle Wilcox continental margin muds creating a density inversion which initiated slump failure of the continental margin sediments. 3) Headward erosion of the canyon across the shelf occurred contemporaneously with a subsidence-induced transgression caused by a decrease in the sediment supply. The Yoakum canyon was excavated by a combination of slumping and current scour. 4) The canyon was filled with hemipelagic and prodelta muds. 5) Progradation of the Upper Wilcox (Carrizo) deltaic sands capped the sequence. / text
45

Dynamic stratigraphy and sediment partitioning of high-supply fluvial succession in Maastrichtian source-to-sink system

Ned, Allison Marie 30 October 2013 (has links)
The sediment budget and paleogeography was reconstructed for the Maastrichtian fluvial to coastal plain Lance Formation (>200m thick) that developed coevally with the shoreline/shelf Fox Hills Sandstone (>200m thick) and deep-water Lewis Shale (>750m thick) in a complete source-to-sink system in the Washakie and Great Divide Basins of south central Wyoming. The system initiated during the final Western Interior Seaway (WIS) transgression and the onset of the Laramide Orogeny rapid subsidence (>2km in 1.9 My) that largely outpaced sediment flux into the basin so the system became and remained a deep-water (>500m water depth) basin beyond the Lance-Fox Hills shelf prism. The active tectonic setting and rapid subsidence caused the Lance fluvial and coastal plain deposits to aggrade and accumulate behind the generally rising shoreline trajectory of the Fox Hills Sandstone. The depositional succession is subdivided into 15 clinothem units and the Lance Formation is best exposed in outcrops in clinoforms 10, 11, and 12. Subsurface analysis correlates key stratigraphic surfaces across the basin to define the sediment budget and clinoform architecture. Field analysis along clinoform 12 on the east side of the basin details facies and paleohydraulic dimensions. Sediment partitioning shows the regressive and transgressive systems tracts (RST and TST) form complementary wedges such that the RST thickens basinward and the TST thins basinward, reflecting the preferential storage of sediment. Channels measured in the field and subsurface datasets are similar in thickness (2m-16m) and suggest braided channel morphology with channel belts from 6.2-8.4km. N/NE paleocurrent trends departing from the subsurface dataset and previous studies of the system provide evidence of possible tidal influences in a developed shoreline embayment or an east to west supply from the basement-cored Rawlins and Sierra Madre Uplifts in the east. The fluvial Lance Formation paleogeography associated with the RST and TST is primarily driven both by modest, Late Cretaceous relative sea level changes and sediment supply linked to the tectonic setting and climate. / text
46

Sedimentology, stratigraphy, and paleogeography of the Fort Crittenden Formation (Upper Cretaceous), southeastern Arizona

Hayes, Michael John, 1962- January 1986 (has links)
No description available.
47

Study of the south-eastern Baltic Sea development applying geological modeling methods / Pietrytinės Baltijos jūros raidos analizė taikant geologinio modeliavimo metodus

Šečkus, Jonas 07 July 2009 (has links)
The main subject of the present research is the geological development of the south-eastern Baltic Sea in Holocene (11000 – 0 calendar years before the present) and prediction of its development in the future (0-1000 calendar years after the present). The present is calendar years 2000AD. The working area is estimated between longitude 18ºE - 21º30’E and latitude between 54ºN - 56º30’N including the onshore and offshore of Lithuania. The quantitative and qualitative geological information and the geological interpretation allowed the 4D modeling of the south-eastern Baltic Sea. Detailed comparison of the influence of isostatic and eustatic components has made it possible to distinguish between these two factors and to create the isostatic intensity models. Last investigations of the global sea level rise (IPCC 2001, 2007) and the model of the recent tectonic activity in the region were used for creation of the prognosis scenarios of relief development in the future. The 4D models created in this dissertation are very well understandable for specialists and for wider readership not engaged in scientific research. The results presented in the dissertation can be useful also by archaeologists and biologists. The results of the model show all the drawbacks of geological material collected so far and outline new perspectives for marine geologists, i.e. demonstrate what works should be done in the future to get more precise results. / Pagrindinis tyrimų tikslas buvo atkurti pietrytinės Baltijos jūros raidą holocene (11000 – 0 kalendorinių metų iki dabar) ir atlikti jūros raidos prognozę iki 1000 metų nuo dabar. Tirtasis regionas apima Lietuvos teritoriją (tiek atviroje jūroje, tiek sausumoje), jo koordinatės yra 18ºE - 21º30’E rytų ilgumos ir 54ºN - 56º30‘N šiaurės platumos. Kokybinė ir kiekybinė geologinė informacija bei jos geologinė interpretacija leido sukurti pietrytinės Baltijos jūros raidos 4D modelius. Detalus kiekybinis eustatinių bei izostatinių vandens lygio pokyčių palyginimas leido atskirti šiuos faktorius bei nustatyti izostatinio komponento intensyvumą holoceno metu. Kiekybiškai įvertinus tektoninius judesius ir vandens lygio pokyčius buvo atlikta pietrytinės Baltijos jūros raidos prognozė. Erdviniai 4 D modeliai pateikti šiame darbe yra lengvai suprantami ne tik specialistams, tačiau ir plačiai visuomenei. Disertacijoje pateikti modeliai gali būti naudingi archeologams bei biologams, tuo pačiu geologams parodydami esančių duomenų trūkumus bei nubrėžiantys naujas perspektyvas tyrimams, kurie turėtų būti atlikti norint gauti kiek galima detalesnius rezultatus.
48

Study of the south-eastern Baltic Sea development applying geological modeling methods / Pietrytinės Baltijos jūros raidos analizė taikant geologinio modeliavimo metodus

Šečkus, Jonas 07 July 2009 (has links)
The main subject of the present research is the geological development of the south-eastern Baltic Sea in Holocene (11000 – 0 calendar years before the present) and prediction of its development in the future (0-1000 calendar years after the present). The present is calendar years 2000AD. The working area is estimated between longitude 18ºE - 21º30’E and latitude between 54ºN - 56º30’N including the onshore and offshore of Lithuania. The quantitative and qualitative geological information and the geological interpretation allowed the 4D modeling of the south-eastern Baltic Sea. Detailed comparison of the influence of isostatic and eustatic components has made it possible to distinguish between these two factors and to create the isostatic intensity models. Last investigations of the global sea level rise (IPCC 2001, 2007) and the model of the recent tectonic activity in the region were used for creation of the prognosis scenarios of relief development in the future. The 4D models created in this dissertation are very well understandable for specialists and for wider readership not engaged in scientific research. The results presented in the dissertation can be useful also by archaeologists and biologists. The results of the model show all the drawbacks of geological material collected so far and outline new perspectives for marine geologists, i.e. demonstrate what works should be done in the future to get more precise results. / Pagrindinis tyrimų tikslas buvo atkurti pietrytinės Baltijos jūros raidą holocene (11000 – 0 kalendorinių metų iki dabar) ir atlikti jūros raidos prognozę iki 1000 metų nuo dabar. Tirtasis regionas apima Lietuvos teritoriją (tiek atviroje jūroje, tiek sausumoje), jo koordinatės yra 18ºE - 21º30’E rytų ilgumos ir 54ºN - 56º30‘N šiaurės platumos. Kokybinė ir kiekybinė geologinė informacija bei jos geologinė interpretacija leido sukurti pietrytinės Baltijos jūros raidos 4D modelius. Detalus kiekybinis eustatinių bei izostatinių vandens lygio pokyčių palyginimas leido atskirti šiuos faktorius bei nustatyti izostatinio komponento intensyvumą holoceno metu. Kiekybiškai įvertinus tektoninius judesius ir vandens lygio pokyčius buvo atlikta pietrytinės Baltijos jūros raidos prognozė. Erdviniai 4 D modeliai pateikti šiame darbe yra lengvai suprantami ne tik specialistams, tačiau ir plačiai visuomenei. Disertacijoje pateikti modeliai gali būti naudingi archeologams bei biologams, tuo pačiu geologams parodydami esančių duomenų trūkumus bei nubrėžiantys naujas perspektyvas tyrimams, kurie turėtų būti atlikti norint gauti kiek galima detalesnius rezultatus.
49

Application of intertidal salt-marsh foraminifera to reconstruct late Holocene sea-level change at Kariega Estuary, South Africa.

Strachan, Kate Leigh. January 2013 (has links)
Unclear predictions surrounding climate change, associated sea-level rise and potential impacts upon coastal environments have placed an emphasis on the importance of sea-level change. Past sea-level fluctuations have been measured using biological and geomorphological forms of evidence. One such biological proxy is salt-marsh foraminifera, which have been used as a high-resolution indicator of past sea-level change, based on the assumption that surface foraminiferal assemblages are similar in composition to buried fossil foraminifera. In South Africa, there is ongoing research seeking to produce high-resolution records of sealevel change, however foraminifera remain an underutilized source of proxy evidence. This research applies salt-marsh foraminifera as precise indicators of relative sea-level change at Kariega Estuary on the Eastern Cape coastline of South Africa. Distributions of modern foraminiferal assemblages were investigated, revealing vertical zonation across the intertidal zone. The foraminiferal and marsh vegetation zones were in part similar and overlapped to a certain extent, identifying three zones; high, low and tidal flats. This suggested foraminiferal distribution is a direct function of elevation relative to tidal fluctuation. A 94 cm core consisting of peat, sand and clay sediments was extracted from the salt marsh. A chronological framework for the core was based on five AMS radiocarbon age determinations of both bulk sediment and shell fragment samples placing the record within the last 1500 years Before Present (BP). The basal shell age was a clear outlier to all bulk sediment ages, possibly as a result of shell recrystallisation. The bulk sediment age determinations suggested two possible age reversals, potentially linked to sedimentary hiatus or contamination. These inconsistencies in the chronology were best viewed as separate age models. The core was analysed at a high resolution, whereby fossil foraminifera were extracted every 2 cm’s down the core. A transfer function was applied to calculate the former elevation at which each core sample once existed, to produce a relative sea-level reconstruction. The reconstruction was related to the age models to produce two possible sea-level curve scenarios. Reconstructed curves from both scenarios depict a 0.5 m (±0.16 m) sealevel highstand at 1500 cal years BP followed by a lowstand of -0.6 m (±0.03 m). Scenario One reached its lowest recorded sea-level between 600 cal years BP and 500 cal years BP and then fluctuated below present day levels. Scenario Two reached its lowest recorded sea-level around 1200 cal years BP, followed by low amplitude fluctuations and a relatively stable period from 100 cal years BP till the present day. The 1500 cal years BP highstand recorded for both scenarios correlates well with existing palaeoenvironmental literature from the southern African coastline. Chronological limitations associated with the remainder of the record hinder inter-comparison with previous studies. The outcomes of this research suggest that intertidal saltmarsh foraminifera demonstrate enormous potential for the high-resolution reconstruction of relative sealevel change in the South African context. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.
50

Palynostratigraphic And Palynofacies Investigation Of The Oligocene-miocene Units In The Kars-erzurum-mus Sub-basins (eastern Anatolia)

Sancay, Recep Hayrettin 01 August 2005 (has links) (PDF)
Eleven dinoflagellates, acritarchs, and pollen biozones have been identified in Upper Eocene to Pliocene sediments combined from MuS, Tekman, Tercan-ASkale, Pasinler-Horasan basins and the Bayburt-Kars Plateau in this study. FAD&amp / #8217 / s of Compositae (tubuliflorae type), Slowakipollenites hipoph&auml / eoides, Mediocolpopollis compactus, Monoporopollenites gramineoides and Umbelliferae at the base of Rupelian, FAD of Wetzeliella gochtii in the middle Rupelian, LAD of Ascostomocystis potane in the late Rupelian, LAD of Wetzeliella gochtii in the latest Rupelian, LAD of Deflandrea spp. in the latest Chattian, peak occurrences of Chriptoredium spp. in the early and late Aquitanian, FAD of Hystrichosphaeropsis obscura, followed by FAD of Membranilarnacea ?picena in the late Aquitanian should have particular emphasis for palynostratigraphic divisions in regional correlations and indicate that a continuous deposition took place in Eastern Anatolia from Late Eocene to the end of the Early Miocene. A relatively deeper marine deposition prevailed during the Late Eocene, which was followed by a shallowing-upward deposition during the Oligocene in MuS, Tekman, Tercan-ASkale, and Pasinler-Horasan basins. These basins were also characterized by an Early Miocene regional transgression, and terrestrial (lacustrine and fluvial) deposition during the Late Miocene-Pliocene whereas terrestrial conditions have been predominating since Late Eocene in the Bayburt-Kars Plateau. Paleoclimatological reconstructions of Eastern Anatolian Oligocene-Miocene sediments suggest temperate to subtropical climates in which mean annual temperatures vary between 15,6 to 21,3 &deg / C, mean temperatures of the coldest and the warmest month are 5.0 to 13.3 &deg / C and 24.7 to 28.1 &deg / C, respectively, and mean annual precipitation is 1122.0 to 1522.0 mm.

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