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Landsystem analysis of three outlet glaciers, southeast IcelandLee, Rebecca E. January 2016 (has links)
Landsystem analysis is a commonly applied methodology which focuses on process-form relationships when applied in glacial environments. It can be used to understand and recreate the geomorphological evolution of glacial deposits from modern and ancient sediments. The purpose of this study is to examine the forefields of three closely located outlet glaciers of the Vatnajökull Ice Cap in southeast Iceland to determine the factors affecting the landsystems of these glaciers. A combination of digital based methods and field work focusing on geomorphology and sedimentology were used to define the landsystems. A classification code and associated symbology was used in this study to create consistency of landsystem analysis and can be used in future similar studies of glacial environments. The three glaciers, Morsárjökull, Skaftafellsjökull and Svínafellsjökull were chosen due to their shared source and close proximity, lying within adjacent valleys. The historical changes of the three glaciers have been well documented with aerial photographs, historical maps and glacier margin measurements. LiDAR were used to interpolate 2 m digital elevation models (DEM) of the three glacier forefields. These glaciers have varying topography, bedrock type and ice distribution (hypsometry, equilibrium line altitude (ELA)) which impacts the deposition at the glacier margin. The forefields of Morsárjökull and Skaftafellsjökull exhibit many similarities in the distribution and scale of landforms similar to the characteristics of the established active temperate landsystem commonly found in Iceland. However, the forefield of Svínafellsjökull has many differences compared to Skaftafellsjökull and Morsárjökull in the scale, type and distribution of landforms and sediments. Bedrock type, hypsometry and glacial debris content are major factors that influence differences in these landsystems. These three forefields may be used as analogues to enhance understanding of paleoenvironmental conditions that existed along the southern margin of Pleistocene glaciers that covered much of northern North America and Europe in the past. / Thesis / Master of Science (MSc)
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Insights into New Zealand Glacial Processes from studies of glacial geomorphology and sedimentology in Rakaia and other South Island ValleysHyatt, Olivia Marie January 2010 (has links)
This thesis investigates the assertion by many early and more recent New Zealand glacial workers, that the high catchment rainfall and low seasonality in New Zealand create unique glacial sedimentary and geomorphic processes. Specifically the thesis examines the nature of glacial sedimentology and geomorphology in South Island, New Zealand focussing on the Rakaia Valley, as most of the early studies that suggested a distinct New Zealand process environment were based on South Island, East Coast glacial valleys. The thesis provides insights into glacial processes operating at glacial termini of late Quaternary glaciers in this region. The primary findings are as follows:
Glacial terminus landforms (moraines) and sediments are described in two eastern (Rakaia and Ashburton Lakes) and one western (Waiho) valley of South Island. There are three main types of landforms 1) outwash head, 2) push moraines and 3) ice-contact fans. Outwash heads and push moraines have been identified before in New Zealand, but ice-contact fans have not. The spatial relationships between the three landforms can be complex especially where there is a fluctuating glacier terminus. Outwash heads are the dominant landform, with ice-contact fans deposited at a stationary terminus with channelised meltwater and push moraines preserved during retreat accompanied with outwash head incision. Both ice-contact fans and push moraines
are prone to reworking into the outwash head. Supraglacial material comprises a small cap on the moraines and is usually insignificant in this system. The nature of past glacier termini can be gained from detailed study of these three landform relationships and their sediment record. The dominance of glacifluvial processes at the glacier terminus is a reflection of the low seasonality, abundant catchment rainfall, coupled with a large sediment supply. Preservation and deposition
of the push moraines and ice-contact fans are controlled by glacifluvial processes on an outwash head, which in turn are controlled by the mass balance of the glacier.
Sedimentology, stratigraphy and facies architecture were examined in the lower Rakaia Valley and elsewhere. The main environments recorded by these sediments are largely proglacial
lacustrine and fluvial including 1) outwash gravels, with deposition of a sequence of glacier-fed, Gilbert-type deltas deposited over buried ice at Bayfield Cliff, 2) lacustrine silts and sands, 3) sub-aqueous ice-contact fans, 4) sub-aqueous mass flow deposits, and 5) supraglacial melt out material. These glacilacustrine facies are widespread during both retreats and advances. Sub-aqueous deltas are the primary ice terminus form, in this mid-valley lacustrine setting, which
record termini advance and retreats. Syn- and postdepositional deformation of lacustine facies are also common as a result of pushing and overriding from the fluctuating glacier termini. Buried ice is also widespread and many of these deposits display evidence of disruption of sedimentation by its meltout. This implies that stagnant tongues of ice were often buried by
outwash and lacustrine sediments.
From the sediments and geomorphology described in this thesis, two main glacier terminus settings in New Zealand valleys are apparent A) when the glacier terminus is on or abutting its outwash fan-head, or B) when the glacier terminus is within its trough.
Both the geomorphic and edimentological findings allow a better understanding of New Zealand glacial chronologies. Firstly, the sedimentology permits the identification of many more advances and retreats than are recorded in surface sediments. At Rakaia Valley, facies record six significant advances and retreats and many more small oscillations over the last 200 000 years. The geomorphic understanding and high resolution mapping has identified many more ice termini in the valleys than were previously recognised and allow the insights into ice margin
behaviour through time. This includes the changing location of outwash heads and glacial troughs, with a migration up-valley since the OIS 6 advance/s, in the Rakaia Valley. The glacier
overran its outwash head to reach its LGM position, and subsequently retreated slowly over about 10,000 years, back to its outwash head. It then changed to a calving margin and continued retreating but with no terminal moraines preserved, only lateral features.
The research in this thesis has contributed to greater understanding of the New Zealand glacial system. Although low seasonality and large volumes of meltwater do play a role, and equally important control in New Zealand valleys is that of tectonics in terms of delivering huge sediment supply. This sediment supply enables large outwash head and fans to accumulate, which allow large stable lakes to form during glacier recession. The data and interpretations from
this thesis will underpin the development of a New Zealand glacial land system, of which other valleys such as the Himalayas have. This land system development is important for
understanding the temperate, high sediment yield glacial environment end member.
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Insights into New Zealand Glacial Processes from studies of glacial geomorphology and sedimentology in Rakaia and other South Island ValleysHyatt, Olivia Marie January 2010 (has links)
This thesis investigates the assertion by many early and more recent New Zealand glacial workers, that the high catchment rainfall and low seasonality in New Zealand create unique glacial sedimentary and geomorphic processes. Specifically the thesis examines the nature of glacial sedimentology and geomorphology in South Island, New Zealand focussing on the Rakaia Valley, as most of the early studies that suggested a distinct New Zealand process environment were based on South Island, East Coast glacial valleys. The thesis provides insights into glacial processes operating at glacial termini of late Quaternary glaciers in this region. The primary findings are as follows: Glacial terminus landforms (moraines) and sediments are described in two eastern (Rakaia and Ashburton Lakes) and one western (Waiho) valley of South Island. There are three main types of landforms 1) outwash head, 2) push moraines and 3) ice-contact fans. Outwash heads and push moraines have been identified before in New Zealand, but ice-contact fans have not. The spatial relationships between the three landforms can be complex especially where there is a fluctuating glacier terminus. Outwash heads are the dominant landform, with ice-contact fans deposited at a stationary terminus with channelised meltwater and push moraines preserved during retreat accompanied with outwash head incision. Both ice-contact fans and push moraines are prone to reworking into the outwash head. Supraglacial material comprises a small cap on the moraines and is usually insignificant in this system. The nature of past glacier termini can be gained from detailed study of these three landform relationships and their sediment record. The dominance of glacifluvial processes at the glacier terminus is a reflection of the low seasonality, abundant catchment rainfall, coupled with a large sediment supply. Preservation and deposition of the push moraines and ice-contact fans are controlled by glacifluvial processes on an outwash head, which in turn are controlled by the mass balance of the glacier. Sedimentology, stratigraphy and facies architecture were examined in the lower Rakaia Valley and elsewhere. The main environments recorded by these sediments are largely proglacial lacustrine and fluvial including 1) outwash gravels, with deposition of a sequence of glacier-fed, Gilbert-type deltas deposited over buried ice at Bayfield Cliff, 2) lacustrine silts and sands, 3) sub-aqueous ice-contact fans, 4) sub-aqueous mass flow deposits, and 5) supraglacial melt out material. These glacilacustrine facies are widespread during both retreats and advances. Sub-aqueous deltas are the primary ice terminus form, in this mid-valley lacustrine setting, which record termini advance and retreats. Syn- and postdepositional deformation of lacustine facies are also common as a result of pushing and overriding from the fluctuating glacier termini. Buried ice is also widespread and many of these deposits display evidence of disruption of sedimentation by its meltout. This implies that stagnant tongues of ice were often buried by outwash and lacustrine sediments. From the sediments and geomorphology described in this thesis, two main glacier terminus settings in New Zealand valleys are apparent A) when the glacier terminus is on or abutting its outwash fan-head, or B) when the glacier terminus is within its trough. Both the geomorphic and edimentological findings allow a better understanding of New Zealand glacial chronologies. Firstly, the sedimentology permits the identification of many more advances and retreats than are recorded in surface sediments. At Rakaia Valley, facies record six significant advances and retreats and many more small oscillations over the last 200 000 years. The geomorphic understanding and high resolution mapping has identified many more ice termini in the valleys than were previously recognised and allow the insights into ice margin behaviour through time. This includes the changing location of outwash heads and glacial troughs, with a migration up-valley since the OIS 6 advance/s, in the Rakaia Valley. The glacier overran its outwash head to reach its LGM position, and subsequently retreated slowly over about 10,000 years, back to its outwash head. It then changed to a calving margin and continued retreating but with no terminal moraines preserved, only lateral features. The research in this thesis has contributed to greater understanding of the New Zealand glacial system. Although low seasonality and large volumes of meltwater do play a role, and equally important control in New Zealand valleys is that of tectonics in terms of delivering huge sediment supply. This sediment supply enables large outwash head and fans to accumulate, which allow large stable lakes to form during glacier recession. The data and interpretations from this thesis will underpin the development of a New Zealand glacial land system, of which other valleys such as the Himalayas have. This land system development is important for understanding the temperate, high sediment yield glacial environment end member.
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Different generation of controlled moraines in the glacier foreland of Midtdalsbreen, Norway / Tvärställt styrda moränslätter alldeles invid Midtdalsbreen glaciär, NorgeAllègre, Xavier January 2018 (has links)
A series of small mounds (< 3m) were sampled in the foreland of Midtdalsbreen outlet glacier, southern Norway. These landforms were interesting, especially at site number 1 because they were located very close to a higher Little Ice Age (LIA) moraine (> 5 m), thereby informing the dynamic of the glacier after the LIA at this location. It was yet to determine if these specific mounds are controlled moraines. If they are controlled moraines, then this would have implication for the glacier dynamics and the geometry of the snout after the LIA. It could be determined, based on the landform record evidence, whether the ice at the snout of Midtdalsbreen was thin and cold shortly after the LIA. Furthermore, whether the landscape was deglaciated by downwasting and then by backwasting was the main question addressed in relation to the nature of the mound and the thickness of ice at the snout during and after the LIA. In order to better understand the nature of the landform record and the mounds near the LIA moraine, satellite imagery coupled with careful field investigations were used in the foreland of the Midtdalsbreen outlet glacier. A geomorphological map was produced, and it was useful to put the mounds in a geographical context. Further sedimentological investigation; including clast-shape analyze, produced more evidence about the inner nature of these landforms. Both few controlled moraines and other landforms throughout the glacier foreland indicate that the ice geometry for Midtdalsbreen, shortly after the LIA was such that the snout of the glacier was a thin sheet of ice flowing against the previously deposited LIA moraine. The sedimentology of the controlled moraine is such that the sediments are deposited in steeply dipping layers, and they could even be misinterpreted as permafrost terrains at first glimpse. However, other sedimentological evidences such as the presence of sorted sand and sometimes dipping beds of gravels in addition to the geomorphological mapping make it meaningful to interpret few of the mounds as controlled moraines. A modern analogue to these controlled moraines is dirt cones present on top of the glacier snout as well as controlled moraines a few hundred of meter from the snout. Observations both on the glacier snout and on the foreland involve that dirt-cones later evolve into these sedimentological hummocky units with steeply dipping layers within the paleo-landscape. These observations constrain the thickness of ice at the snout of Midtdalsbreen after the LIA as well as the glacier dynamic during its melt: for controlled moraines to be generated by glaciers, these accumulations of sediments would have to thaw by downwasting and then by backwasting, directly at the glacier snout. This process -comprising of different stages- allows enough time to deposit controlled moraine. It is then a thin, cold-based sheet of ice which is by the end responsible for the deposition of such a landform record. There was even dead-ice present on the landscape at that point. After deposition of dirt cones on top of the ice, important meltwater action is contributing to the glacifluvial origin of these hummocks which evolve from dirt-cones onto the glacier, to ice-cored moraines, and then to controlled moraines onto the foreland. Details about the multistage processes leading to the formation of controlled moraines is also at the center of the investigations. / <p>Updated version, september 2019.</p>
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Origin, Sedimentological Characteristics, and Paleoglacial Significance of Large Latero-Frontal Moraines in Deglaciating Regions of Perú and IcelandNarro Pérez, Rodrigo Alberto January 2021 (has links)
This thesis investigates the origin, sedimentological characteristics, and paleoglacial significance of large latero-frontal moraines and moraine-dammed glacial lakes and their potential to generate glacial lake outburst flood (GLOF) events in the Cordillera Blanca, Perú and Iceland. This topic is particularly important as the potential for GLOF events in high altitude regions is increasing as ongoing global climate warming causes rapid glacier recession and the growth of lakes impounded by unstable moraines.
The first chapter of this thesis introduces the characteristics of moraine dammed lakes and GLOFs and provides details of the study areas in Perú and Iceland that were selected for this work (Chapter 1). Chapter 2 investigates the glacial history of the Cordillera Blanca, Perú through the compilation, mapping, and analysis of dated moraines in the region. The formation of moraines by different glaciers in the same region at approximately the same time is interpreted to indicate a period of regional climate conditions that were favourable for glacier expansion and/or equilibrium. Six stages of glacial activity are identified from this analysis, ranging in age from older than 35 thousand years (Stage 1) to modern (Stage 6).
The third chapter of this thesis identifies the geomorphic and sedimentologic characteristics of a moraine-dammed supraglacial lake (Llaca Lake) in the Cordillera Blanca, Perú. The combined use of imagery collected with an uncrewed-aerial vehicle (UAV), field sedimentological observations and geomorphological mapping allowed the creation of a landsystem model that summarizes the current geomorphic and sedimentologic environment of Llaca Lake (Chapter 3). This is the first study to describe the landform-sediment assemblages in a tropical moraine-dammed supraglacial lake and provides a framework for further landsystem analysis of growing supraglacial lakes that are at risk of GLOF events.
The fourth chapter of this thesis describes the sedimentary architecture of the eastern lateral moraine of Gígjökull in southern Iceland. An uncrewed-aerial vehicle was used to acquire high resolution photographs of an exposure through the lateral moraine that allowed the identification of seven lithofacies types and three lithofacies associations. Documentation of the sedimentary architecture of the eastern lateral moraine of Gígjökull enhances understanding of moraine development and the identification of areas of hydrogeological weakness that can reduce the structural integrity of the moraine.
The research findings presented in this thesis utilize a glacial sedimentological and geomorphological approach to investigating the relationship between current and past glacial processes in the study areas, and the role that these processes play in determining the characteristics and stability of large ice marginal moraines that impound glacial lakes. This work also furthers our understanding of the dynamic surface processes at work in high altitude regions such as the Cordillera Blanca. Identifying and determining the relationships between current and past processes, sediments and landforms will enhance understanding of the role of large moraines damming glacial lakes in other high-altitude regions such as the Himalayas, British Columbia, Patagonia, and New Zealand and the associated risk of GLOF events. / Thesis / Doctor of Science (PhD)
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Late Pleistocene Glacial Geology of the Hope-Waiau Valley System in North Canterbury, New ZealandRother, Henrik January 2006 (has links)
This thesis presents stratigraphic, sedimentological and geochronological results from valley fill and glacial moraines of the Hope-Waiau Valleys in North Canterbury, New Zealand. The findings demonstrate that a substantial portion of the modern valley fill comprises in-situ sedimentary sequences that were deposited during the penultimate glaciation (OIS 6), the last interglacial (OIS 5) and during the mid-late last glacial cycle (OIS 3/2). The sediments survived at low elevations in the valley floor despite overriding by later glacial advances. Sedimentologically, the fill indicates deposition in an ice marginal zone and consists of paraglacial/distal-proglacial aggradation gravels and ice-proximal/marginal-subglacial sediments. Deposition during glacial advance phases was characterized by the sedimentation of outwash gravels and small push moraines while glacial retreat phases are dominated by glaciolacustrine deposits which are frequently interbedded with debris flow diamictons. The overall depositional arrangement indicates that glacial retreat from the lower valley portion occurred via large scale ice stagnation. Results from infra-red stimulated luminescence (IRSL) dating gives evidence for five large aggradation and degradation phases in the Hope-Waiau Valleys over the last 200 ka. Combined with surface exposure dating (SED) of moraines the geochronological results indicate that glacial advances during OIS 6 were substantially larger in both ice extent and ice volume than during OIS 4-2. The last glacial maximum (LGM) ice advance occurred prior to 20.5 ka and glacial retreat from extended ice positions began by ~18 ka BP. A late glacial re-advance (Lewis Pass advance) occurred at ~13 ka BP and is probably associated with a regional cooling event correlated to the Antarctic Cold Reversal (ACR). The findings from the Hope-Waiau Valleys were integrated into a model for glaciations in the Southern Alps which uses data from a snow mass balance model to analyse the sensitivity of glacial accumulation to temperature forcing. Model results indicate that in the central hyperhumid sector of the Southern Alps ice would expand rapidly with minor cooling (2-4℃) suggesting that full glaciation could be generated with little thermal forcing. Some Quaternary glacial advances in the Southern Alps may have been triggered by regional climate phenomena (e.g. changes in ENSO mode) rather than requiring a thermal trigger from the Northern Hemisphere.
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Análise e correlação de seqüências de 3a ordem do Subgrupo Itararé (PC), entre a região de Sorocaba-Itapetininga, SP, e a região ao sul do Arco de Ponta Grossa, Bacia do Paraná, Brasil / 3rd order sequence stratigraphy of Itararé Subgroup (Neopaleozoic), within Sorocaba - Itapetininga (SP) and the south area of Ponta Grossa Arch, Parana Basin, BrazilVieira, Gabriel Luiz Perez 21 August 2007 (has links)
O Subgrupo Itararé apresenta o registro sedimentar mais expressivo da glaciação que assolou a Bacia do Paraná durante o Neopaleozóico. Próximo à borda leste da bacia, em especial na área do estudo, entre os municípios de Sorocaba e Itapetininga, este registro é caracterizado basicamente por depósitos glaciomarinhos, representativos de períodos de mar relativamente mais baixo intercalados com registros de mar relativamente alto. Através da definição e análise de fácies foi possível identificar, na área do estudo, 15 (quinze) unidades faciológicas: Diamictito maciço compactado, Diamictito maciço não compactado, Diamictito maciço compactado deformado, Diamictito tabular, Diamictito lenticular, Arenito maciço tabular, Arenito maciço lenticular, Arenito com estratificação gradacional, Arenito com estratificação cruzada e granodecrescência ascendente, Arenito com estratificação cruzada de baixo ângulo e truncamentos, Siltito maciço, Siltito maciço com clastos dispersos, Folhelho ou argilito maciço, Folhelho ou argilito maciço, com clastos dispersos e Interlaminado. A análise dessas fácies, bem como seu agrupamento em associações diagnósticas (AF1, AF2, AF3 e AF4), permitiu o reconhecimento de tratos de sistemas deposicionais, TSMB, TST, TSMA e TSRGi, os quais, por sua vez, levaram à identificação de 9 (nove) seqüências de 3ª ordem, que permitiram o estabelecimento um arcabouço cronoestratigráfico para os sedimentos do Subgrupo Itararé, ao longo do perfil selecionado na área do estudo. Para se realizar a correlação pretendida entre os sedimentos do Subgrupo Itararé na área do estudo e os aflorantes na região localizada ao sul do Arco de Ponta Grossa no Paraná e Santa Catarina, foram identificados planos ou horizontes que podem ser utilizados, segundo suas características, como datum litoestratigráfico e datum bioestratigráfico. Os resultados das análises palinológicas, bem como os próprios dados físicos de superfície, demonstraram confiabilidade e viabilidade de correlação. A análise petrográfica efetuada em quatro amostras de arenitos revelou porosidades da ordem de 8 a 13%, o que permitiu caracterizar esses sedimentos como potencialmente bons para reservatórios relativamente a hidrocarbonetos ou aqüíferos. / The Itararé Subgroup (Carboniferous-Permian) of the Paraná Basin of southeastern Brazil contains the thickest, most extensive and one of the longest records of late Paleozoic glaciation in all of the Gondwana supercontinent. In the studied area, situated between the cities of Sorocaba and Itapetininga, São Paulo State, this record is characterized by glaciomarine sediments depicting intercalation of periods of high and low relative sea-level. Facies analysis of the glacigenic sediments allowed the identification of 15 lithofacie units: compact massive diamictite, massive non compact diamictite, massive non compact deformed diamictite, tabular diamictite, lenticular diamictite, massive tabular sandstone, massive lenticular sandstone, sandstone with gradational bedding, sandstone with cross bedding and normal grading, sandstone with low angle cross bedding and truncations, massive siltstone, massive siltstone with clasts, massive shale or mudstone, massive shale or mudstone with dispersed clasts and laminites. The analysis of facies and their clustering into the associations AF1, AF2, AF3 and AF4 enabled the identification of the systems tracts TSMB, TST, TSMA and TSRGi and 9 sequences of 3rd order. These provided the base to set up a local chronostratigraphic framework for the Itararé Subgroup in the studied area. In view of the possibility of correlation between the sediments of the studied area and those outcropping in the south of the Ponta Grossa arch, in the States of Paraná and Santa Catarina, some datum planes were determined. The results of the palinological analysis as well as the surface data surveyed pointed out that this correlation is feasible. Petrographic analysis of 4 samples of sandstones indicated porosities between 8 and 13 % which characterize them as potentially reservoirs for water and hydrocarbon.
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Late Pleistocene Glacial Geology of the Hope-Waiau Valley System in North Canterbury, New ZealandRother, Henrik January 2006 (has links)
This thesis presents stratigraphic, sedimentological and geochronological results from valley fill and glacial moraines of the Hope-Waiau Valleys in North Canterbury, New Zealand. The findings demonstrate that a substantial portion of the modern valley fill comprises in-situ sedimentary sequences that were deposited during the penultimate glaciation (OIS 6), the last interglacial (OIS 5) and during the mid-late last glacial cycle (OIS 3/2). The sediments survived at low elevations in the valley floor despite overriding by later glacial advances. Sedimentologically, the fill indicates deposition in an ice marginal zone and consists of paraglacial/distal-proglacial aggradation gravels and ice-proximal/marginal-subglacial sediments. Deposition during glacial advance phases was characterized by the sedimentation of outwash gravels and small push moraines while glacial retreat phases are dominated by glaciolacustrine deposits which are frequently interbedded with debris flow diamictons. The overall depositional arrangement indicates that glacial retreat from the lower valley portion occurred via large scale ice stagnation. Results from infra-red stimulated luminescence (IRSL) dating gives evidence for five large aggradation and degradation phases in the Hope-Waiau Valleys over the last 200 ka. Combined with surface exposure dating (SED) of moraines the geochronological results indicate that glacial advances during OIS 6 were substantially larger in both ice extent and ice volume than during OIS 4-2. The last glacial maximum (LGM) ice advance occurred prior to 20.5 ka and glacial retreat from extended ice positions began by ~18 ka BP. A late glacial re-advance (Lewis Pass advance) occurred at ~13 ka BP and is probably associated with a regional cooling event correlated to the Antarctic Cold Reversal (ACR). The findings from the Hope-Waiau Valleys were integrated into a model for glaciations in the Southern Alps which uses data from a snow mass balance model to analyse the sensitivity of glacial accumulation to temperature forcing. Model results indicate that in the central hyperhumid sector of the Southern Alps ice would expand rapidly with minor cooling (2-4℃) suggesting that full glaciation could be generated with little thermal forcing. Some Quaternary glacial advances in the Southern Alps may have been triggered by regional climate phenomena (e.g. changes in ENSO mode) rather than requiring a thermal trigger from the Northern Hemisphere.
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Análise e correlação de seqüências de 3a ordem do Subgrupo Itararé (PC), entre a região de Sorocaba-Itapetininga, SP, e a região ao sul do Arco de Ponta Grossa, Bacia do Paraná, Brasil / 3rd order sequence stratigraphy of Itararé Subgroup (Neopaleozoic), within Sorocaba - Itapetininga (SP) and the south area of Ponta Grossa Arch, Parana Basin, BrazilGabriel Luiz Perez Vieira 21 August 2007 (has links)
O Subgrupo Itararé apresenta o registro sedimentar mais expressivo da glaciação que assolou a Bacia do Paraná durante o Neopaleozóico. Próximo à borda leste da bacia, em especial na área do estudo, entre os municípios de Sorocaba e Itapetininga, este registro é caracterizado basicamente por depósitos glaciomarinhos, representativos de períodos de mar relativamente mais baixo intercalados com registros de mar relativamente alto. Através da definição e análise de fácies foi possível identificar, na área do estudo, 15 (quinze) unidades faciológicas: Diamictito maciço compactado, Diamictito maciço não compactado, Diamictito maciço compactado deformado, Diamictito tabular, Diamictito lenticular, Arenito maciço tabular, Arenito maciço lenticular, Arenito com estratificação gradacional, Arenito com estratificação cruzada e granodecrescência ascendente, Arenito com estratificação cruzada de baixo ângulo e truncamentos, Siltito maciço, Siltito maciço com clastos dispersos, Folhelho ou argilito maciço, Folhelho ou argilito maciço, com clastos dispersos e Interlaminado. A análise dessas fácies, bem como seu agrupamento em associações diagnósticas (AF1, AF2, AF3 e AF4), permitiu o reconhecimento de tratos de sistemas deposicionais, TSMB, TST, TSMA e TSRGi, os quais, por sua vez, levaram à identificação de 9 (nove) seqüências de 3ª ordem, que permitiram o estabelecimento um arcabouço cronoestratigráfico para os sedimentos do Subgrupo Itararé, ao longo do perfil selecionado na área do estudo. Para se realizar a correlação pretendida entre os sedimentos do Subgrupo Itararé na área do estudo e os aflorantes na região localizada ao sul do Arco de Ponta Grossa no Paraná e Santa Catarina, foram identificados planos ou horizontes que podem ser utilizados, segundo suas características, como datum litoestratigráfico e datum bioestratigráfico. Os resultados das análises palinológicas, bem como os próprios dados físicos de superfície, demonstraram confiabilidade e viabilidade de correlação. A análise petrográfica efetuada em quatro amostras de arenitos revelou porosidades da ordem de 8 a 13%, o que permitiu caracterizar esses sedimentos como potencialmente bons para reservatórios relativamente a hidrocarbonetos ou aqüíferos. / The Itararé Subgroup (Carboniferous-Permian) of the Paraná Basin of southeastern Brazil contains the thickest, most extensive and one of the longest records of late Paleozoic glaciation in all of the Gondwana supercontinent. In the studied area, situated between the cities of Sorocaba and Itapetininga, São Paulo State, this record is characterized by glaciomarine sediments depicting intercalation of periods of high and low relative sea-level. Facies analysis of the glacigenic sediments allowed the identification of 15 lithofacie units: compact massive diamictite, massive non compact diamictite, massive non compact deformed diamictite, tabular diamictite, lenticular diamictite, massive tabular sandstone, massive lenticular sandstone, sandstone with gradational bedding, sandstone with cross bedding and normal grading, sandstone with low angle cross bedding and truncations, massive siltstone, massive siltstone with clasts, massive shale or mudstone, massive shale or mudstone with dispersed clasts and laminites. The analysis of facies and their clustering into the associations AF1, AF2, AF3 and AF4 enabled the identification of the systems tracts TSMB, TST, TSMA and TSRGi and 9 sequences of 3rd order. These provided the base to set up a local chronostratigraphic framework for the Itararé Subgroup in the studied area. In view of the possibility of correlation between the sediments of the studied area and those outcropping in the south of the Ponta Grossa arch, in the States of Paraná and Santa Catarina, some datum planes were determined. The results of the palinological analysis as well as the surface data surveyed pointed out that this correlation is feasible. Petrographic analysis of 4 samples of sandstones indicated porosities between 8 and 13 % which characterize them as potentially reservoirs for water and hydrocarbon.
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