Academic literature on the topic 'Periodo glacial - Pleistoceno'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Periodo glacial - Pleistoceno.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Periodo glacial - Pleistoceno"
1
López-García, J. M., L. Póvoas, and J. Zilhão. "Nota sobre la taxonomía de Microtus (Iberomys) (Arvicolinae, Rodentia) del Pleistoceno superior de la Gruta do Caldeirão (Tomar, Portugal) e interpretación paleoclimática de la asociación de roedores." Estudios Geológicos 76, no. 1 (July 10, 2020): 128. http://dx.doi.org/10.3989/egeol.43622.542.
Full textAbstract:
Gruta do Caldeirão es un yacimiento arqueológico en cueva situado en Tomar (Portugal, oeste de la península Ibérica), que contiene una importante secuencia perteneciente al Pleistoceno superior, adscrita culturalmente al Paleolítico medio (Musteriense) y Paleolítico superior (Solutrense-Magdaleniense), que incluye industria lítica, restos humanos y restos de grandes y pequeños vertebrados. La revisión e interpretación de la asociación de roedores de la secuencia, previamente publicada en los años 90 del siglo pasado, nos ha permitido remarcar tres importantes conclusiones: 1) la única especie del subgénero Iberomys presente en la secuencia es la especie endémica actual de topillo Microtus (Iberomys) cabrerae (topillo de Cabrera); 2) la asociación de roedores está dominada en toda la secuencia por especies relacionadas con bosques abiertos, como el ratón de campo (Apodemus sylvaticus) y especies relacionadas con espacios abiertos-húmedos como los topillos mediterráneo y lusitánico (Microtus (Terricola) spp.), remarcando la presencia de un hámster extinto (Allocricetus bursae) en el nivel K y tres especies de topillos que no tienen representación actual en la zona circundante a la cavidad (Microtus arvalis - topillo campesino, Microtus agrestis – topillo agreste y Chionomys nivalis - topillo nival); 3) Finalmente, el método del Modelo Bioclimático, aplicado a la asociación de roedores, otorga resultados acordes con que la ocupaciones solutrenses situadas entre los niveles H y Fa están relacionadas con un periodo frío equiparado con el Último Máximo Glacial (LGM), indicado por las dataciones de radiocarbono y anteriores estudios de susceptibilidad magnética de la secuencia.
2
Zech, R., Y. Huang, M. Zech, R. Tarozo, and W. Zech. "A permafrost glacial hypothesis to explain atmospheric CO<sub>2</sub> and the ice ages during the Pleistocene." Climate of the Past Discussions 6, no. 5 (October 15, 2010): 2199–221. http://dx.doi.org/10.5194/cpd-6-2199-2010.
Full textAbstract:
Abstract. Over the past several 100 ka glacial-interglacial cycles, the concentration of atmospheric CO2 was closely coupled to global temperature, which indicates the importance of CO2 as a greenhouse gas. The reasons for changes in atmospheric CO2 have mainly been sought in the ocean, yet proxy evidence does not support the notion of increased oceanic carbon storage during glacials. Here we present results from the first permafrost loess sequence in Siberia spanning two glacial cycles (~240 ka), which reveal that permafrost soils repeatedly sequestered huge amounts of terrestrial carbon during glacial periods. This can be explained with permafrost favouring more intensive waterlogging conditions and better preservation of soil organic matter. Terrestrial carbon stored in permafrost soils was released upon warming and provided a powerful feedback mechanism for the glacial terminations. We outline a "permafrost glacial hypothesis" building on integrated annual insolation forcing, which readily explains the observed succession of the ice ages during the Pleistocene, including the mid-Pleistocene transition.
3
Schachtman, Nathan S., Kelly R. MacGregor, Amy Myrbo, Nora Rose Hencir, Catherine A. Riihimaki, Jeffrey T. Thole, and Louisa I. Bradtmiller. "Lake core record of Grinnell Glacier dynamics during the latest Pleistocene deglaciation and the Younger Dryas, Glacier National Park, Montana, USA." Quaternary Research 84, no. 1 (July 2015): 1–11. http://dx.doi.org/10.1016/j.yqres.2015.05.004.
Full textAbstract:
Few records in the alpine landscape of western North America document the geomorphic and glaciologic response to climate change during the Pleistocene–Holocene transition. While moraines can provide snapshots of glacier extent, high-resolution records of environmental response to the end of the Last Glacial Maximum, Younger Dryas cooling, and subsequent warming into the stable Holocene are rare. We describe the transition from the late Pleistocene to the Holocene using a ~ 17,000-yr sediment record from Swiftcurrent Lake in eastern Glacier National Park, MT, with a focus on the period from ~ 17 to 11 ka. Total organic and inorganic carbon, grain size, and carbon/nitrogen data provide evidence for glacial retreat from the late Pleistocene into the Holocene, with the exception of a well-constrained advance during the Younger Dryas from 12.75 to 11.5 ka. Increased detrital carbonate concentration in Swiftcurrent Lake sediment reflects enhanced glacial erosion and sediment transport, likely a result of a more proximal ice terminus position and a reduction in the number of alpine lakes acting as sediment sinks in the valley.
4
Buoncristiani, Jean-François, and Michel Campy. "Late Pleistocene Detrital Sediment Yield of the Jura Glacier, France." Quaternary Research 56, no. 1 (July 2001): 51–61. http://dx.doi.org/10.1006/qres.2001.2243.
Full textAbstract:
AbstractMeasures of present-day glacial erosion vary widely with the technique employed. This paper quantifies the glacial material trapped in a proglacial lake during the Würm glacial period. The Combe d'Ain site was occupied by a meltwater lake where all the detrital material entering it from the Jura glacier accumulated. Sediment yield is computed from three factors: (1) the size of the sediment source area, (2) the length of time the system operated, and (3) the volume of sediment trapped. The sediment budget of the lake system suggests a detrital sediment yield of 4400±1700 metric tons per square kilometer and per calendar year. This represents a denudation rate of 1.6±0.6 mm per year, illustrating that mechanical erosion by the Jura glacier is more intensive than other processes of erosion.
5
Weir, Jason T., Oliver Haddrath, Hugh A. Robertson, Rogan M. Colbourne, and Allan J. Baker. "Explosive ice age diversification of kiwi." Proceedings of the National Academy of Sciences 113, no. 38 (August 29, 2016): E5580—E5587. http://dx.doi.org/10.1073/pnas.1603795113.
Full textAbstract:
Molecular dating largely overturned the paradigm that global cooling during recent Pleistocene glacial cycles resulted in a burst of species diversification although some evidence exists that speciation was commonly promoted in habitats near the expanding and retracting ice sheets. Here, we used a genome-wide dataset of more than half a million base pairs of DNA to test for a glacially induced burst of diversification in kiwi, an avian family distributed within several hundred kilometers of the expanding and retracting glaciers of the Southern Alps of New Zealand. By sampling across the geographic range of the five kiwi species, we discovered many cryptic lineages, bringing the total number of kiwi taxa that currently exist to 11 and the number that existed just before human arrival to 16 or 17. We found that 80% of kiwi diversification events date to the major glacial advances of the Middle and Late Pleistocene. During this period, New Zealand was repeatedly fragmented by glaciers into a series of refugia, with the tiny geographic ranges of many kiwi lineages currently distributed in areas adjacent to these refugia. Estimates of effective population size through time show a dramatic bottleneck during the last glacial cycle in all but one kiwi lineage, as expected if kiwi were isolated in glacially induced refugia. Our results support a fivefold increase in diversification rates during key glacial periods, comparable with levels observed in classic adaptive radiations, and confirm that at least some lineages distributed near glaciated regions underwent rapid ice age diversification.
6
Verbitsky, Mikhail Y., Michel Crucifix, and Dmitry M. Volobuev. "A theory of Pleistocene glacial rhythmicity." Earth System Dynamics 9, no. 3 (August 20, 2018): 1025–43. http://dx.doi.org/10.5194/esd-9-1025-2018.
Full textAbstract:
Abstract. Variations in Northern Hemisphere ice volume over the past 3 million years have been described in numerous studies and well documented. These studies depict the mid-Pleistocene transition from 40 kyr oscillations of global ice to predominantly 100 kyr oscillations around 1 million years ago. It is generally accepted to attribute the 40 kyr period to astronomical forcing and to attribute the transition to the 100 kyr mode to a phenomenon caused by a slow trend, which around the mid-Pleistocene enabled the manifestation of nonlinear processes. However, both the physical nature of this nonlinearity and its interpretation in terms of dynamical systems theory are debated. Here, we show that ice-sheet physics coupled with a linear climate temperature feedback conceal enough dynamics to satisfactorily explain the system response over the full Pleistocene. There is no need, a priori, to call for a nonlinear response of the carbon cycle. Without astronomical forcing, the obtained dynamical system evolves to equilibrium. When it is astronomically forced, depending on the values of the parameters involved, the system is capable of producing different modes of nonlinearity and consequently different periods of rhythmicity. The crucial factor that defines a specific mode of system response is the relative intensity of glaciation (negative) and climate temperature (positive) feedbacks. To measure this factor, we introduce a dimensionless variability number, V. When positive feedback is weak (V∼0), the system exhibits fluctuations with dominating periods of about 40 kyr which is in fact a combination of a doubled precession period and (to smaller extent) obliquity period. When positive feedback increases (V∼0.75), the system evolves with a roughly 100 kyr period due to a doubled obliquity period. If positive feedback increases further (V∼0.95), the system produces fluctuations of about 400 kyr. When the V number is gradually increased from its low early Pleistocene values to its late Pleistocene value of V∼0.75, the system reproduces the mid-Pleistocene transition from mostly 40 kyr fluctuations to a 100 kyr period rhythmicity. Since the V number is a combination of multiple parameters, it implies that multiple scenarios are possible to account for the mid-Pleistocene transition. Thus, our theory is capable of explaining all major features of the Pleistocene climate, such as the mostly 40 kyr fluctuations of the early Pleistocene, a transition from an early Pleistocene type of nonlinear regime to a late Pleistocene type of nonlinear regime, and the 100 kyr fluctuations of the late Pleistocene. When the dynamical climate system is expanded to include Antarctic glaciation, it becomes apparent that climate temperature positive feedback (or its absence) plays a crucial role in the Southern Hemisphere as well. While the Northern Hemisphere insolation impact is amplified by the outside-of-glacier climate and eventually affects Antarctic surface and basal temperatures, the Antarctic ice-sheet area of glaciation is limited by the area of the Antarctic continent, and therefore it cannot engage in strong positive climate feedback. This may serve as a plausible explanation for the synchronous response of the Northern and Southern Hemisphere to Northern Hemisphere insolation variations. Given that the V number is dimensionless, we consider that this model could be used as a framework to investigate other physics that may possibly be involved in producing ice ages. In such a case, the equation currently representing climate temperature would describe some other climate component of interest, and as long as this component is capable of producing an appropriate V number, it may perhaps be considered a feasible candidate.
7
Palacios, David, Nuria de Andrés, Juan I. López-Moreno, and José M. García-Ruiz. "Late Pleistocene deglaciation in the upper Gállego Valley, central Pyrenees." Quaternary Research 83, no. 3 (May 2015): 397–414. http://dx.doi.org/10.1016/j.yqres.2015.01.010.
Full textAbstract:
Deglaciation processes in the upper Gállego Valley, central–southern Pyrenees, were studied using geomorphological mapping and 36Cl cosmogenic dating of moraine and rock glacier boulders, as well as polished bedrock. Although the precise position of the Gállego Glacier during the global last glacial maximum is not known, there is evidence that ice tongues retreated to the headwaters, which caused subdivision of the main glacier into a number of individual glaciers prior to 17 ka. A range of ages (16 to 11 ka) was found among three tributary valleys within the general trend of deglaciation. The retreat rate to cirque was estimated to be relatively rapid (approximately 5 km per ka). The mapped glacial sedimentology and geomorphology appears to support the occurrence of multiple minor advances and retreats, or periods of stasis during the late deglaciation. Geomorphological and geological differences among the tributary valleys, and error estimates associated with the results obtained, prevented unambiguous correlations of the advances with the late Pleistocene cold periods. During the latter advances, small glaciers and rock glaciers developed close to the cirque headwalls, and co-occurred under the same climatic conditions. No evidence for Holocene re-advance was found for any of the three tributary valleys.
8
Eyles, N., and John J. Clague. "Landsliding caused by Pleistocene glacial lake ponding–an example from central British Columbia." Canadian Geotechnical Journal 24, no. 4 (November 1, 1987): 656–63. http://dx.doi.org/10.1139/t87-080.
Full textAbstract:
Sections cut through the Quaternary sediment fill of the Fraser River valley in central British Columbia provide evidence for large-scale landsliding during Pleistocene time. Especially notable are thick, laterally extensive diamict beds, consisting mainly of Tertiary rock debris, that occur near the base of glaciolacustrine sequences. These beds were deposited by subaqueous debris flows during one or more periods of lake ponding when advancing Pleistocene glaciers blocked the ancestral Fraser River. The association of diamict beds and glaciolacustrine sediments deposited during periods of glacier advance may indicate a genetic link between slope failure and lake filling. These observations (1) demonstrate the adverse effects of high pore pressures on the stability of slopes underlain by poorly indurated Tertiary rocks and (2) extend the known history of landslides involving these rocks back into the Pleistocene. Key words: landslides, debris flows, Pleistocene, glacial lake.
9
Blard, Pierre-Henri, Jérôme Lave, Kenneth A. Farley, Victor Ramirez, Nestor Jimenez, Léo C. P. Martin, Julien Charreau, Bouchaïb Tibari, and Michel Fornari. "Progressive glacial retreat in the Southern Altiplano (Uturuncu volcano, 22°S) between 65 and 14 ka constrained by cosmogenic 3He dating." Quaternary Research 82, no. 1 (July 2014): 209–21. http://dx.doi.org/10.1016/j.yqres.2014.02.002.
Full textAbstract:
AbstractThis work presents the first reconstruction of late Pleistocene glacier fluctuations on Uturuncu volcano, in the Southern Tropical Andes. Cosmogenic 3He dating of glacial landforms provides constraints on ancient glacier position between 65 and 14 ka. Despite important scatter in the exposure ages on the oldest moraines, probably resulting from pre-exposure, these 3He data constrain the timing of the moraine deposits and subsequent glacier recessions: the Uturuncu glacier may have reached its maximum extent much before the global LGM, maybe as early as 65 ka, with an equilibrium line altitude (ELA) at 5280 m. Then, the glacier remained close to its maximum position, with a main stillstand identified around 40 ka, and another one between 35 and 17 ka, followed by a limited recession at 17 ka. Then, another glacial stillstand is identified upstream during the late glacial period, probably between 16 and 14 ka, with an ELA standing at 5350 m. This stillstand is synchronous with the paleolake Tauca highstand. This result indicates that this regionally wet and cold episode, during the Heinrich 1 event, also impacted the Southern Altiplano. The ELA rose above 5450 m after 14 ka, synchronously with the Bolling–Allerod.
10
Angel, I., O. Guzman, and J. Carcaillet. "Pleistocene Glaciations in the Northern Tropical Andes, South America (Venezuela, Colombia and Ecuador)." Cuadernos de Investigación Geográfica 43, no. 2 (September 15, 2017): 571. http://dx.doi.org/10.18172/cig.3202.
Full textAbstract:
This article presents an overview of glaciation studies in the northern tropical Andes (Venezuela, Colombia and Ecuador) mostly based on glacial geochronological data. The oldest dated evidences of glaciations are recorded in the Colombian Andes at the Bogotá Plain between 3000-3500 m a.s.l., dated between 1-3 Ma. Maximum extent of former glaciers in the northern Andes seems to have occurred prior to the global Last Glacial Maximum (gLGM). In the Venezuelan-Mérida Andes, former glaciers mostly reached the lowest recorded elevations during MIS 5-MIS 4, whereas in the Colombian Andes Andes, the maximum extents are recorded prior to 38 ka. In the Ecuadorian Andes the most extensive glacial cover probably occurred during MIS 8. In the northern tropical Andes, studied glacier advances are mainly related to MIS 2 period between the final gLGM to the Oldest Dryas (~18 ka-15 ka). Glacier advances during the Younger Dryas (~ 12.7 ka-11.7 ka) are not extensively evidenced and mainly restricted to elevations higher than ~ 3500 m a.s.l.
Dissertations / Theses on the topic "Periodo glacial - Pleistoceno"
1
Lindemann, Douglas da Silva. "Alterações atmosféricas e oceânicas durante o super-interglacial Marine Isotope Stage 31." Universidade Federal de Viçosa, 2016. http://www.locus.ufv.br/handle/123456789/7800.
Full textAbstract:
Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2016-06-06T14:30:21Z
No. of bitstreams: 1
texto completo.pdf: 7032650 bytes, checksum: a6869e490453b254e2494ce476874fd8 (MD5)Made available in DSpace on 2016-06-06T14:30:21Z (GMT). No. of bitstreams: 1 texto completo.pdf: 7032650 bytes, checksum: a6869e490453b254e2494ce476874fd8 (MD5) Previous issue date: 2016-02-16
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Climas passados são ferramentas indispensáveis para o entendimento das projeções de clima futuro devido suas condições forcantes serem diferentes das condições atuais e futuras, devido a emissão antropogênica de gases de efeito estuda. Por meio da comparação entre simulações e reconstruções climáticas em períodos passados a sensibilidade climática pode ser aferida para diferentes componentes. Portanto, o objetivo deste estudo é avaliar as respostas dos componentes oceânicos e atmosféricos a alteração na topografia da Antártica e variações nos parâmetros orbitais da Terra. Para tanto, foi utilizado o modelo climático global acoplado SPEEDY-NEMO. Foram realizadas uma simulação controle (CONTROL) e três simulações de sensibilidades (MIS31, ORBIT e TOPO). Para avaliar o desempenho do SPEEDY-NEMO em representar o clima atual, a simulação CONTROL foi comparada com reanálises, onde percebeu-se que, os principais aspectos do clima foram bem representados pelo modelo com desvios padrões muito semelhantes aos encontrados nas reanálises. Todavia, o gelo marinho ainda precisa de melhorias na sua representação. Nos experimentos com sensibilidades, elevados valores de anomalias positivas de temperatura do ar e oceanos foram identificados sobre o Hemisfério Norte (HN), por influência das condições orbitais impostas. Ainda nas simulações com alterações orbitais, é observado significativas variações nos campos de vento próximo à superfície e precipitação, como por exemplo a ausência das monções sul-americana e africana durante o período de verão austral. Mudanças astronômicas também influenciaram o ENSO. As condições encontradas demonstram uma condição muito semelhante ao de um El Niño permanente, ou seja, com valores de TSM mais elevados se comparados com o CONTROL. Na componente oceânica também foi identificado uma significativa alteração no transporte de calor oceânico no sentido das altas latitudes do HN. Também foi observado que a alteração da topografia da Antártica exerce uma influência muito significativa no sistema oceano – atmosfera das altas latitudes do Hemisfério Sul.
Past climates are indispensable tools for the understanding of future climate projections because their conditions are different from current and future conditions, related to the anthropogenic emission of greenhouse gases. Moreover, through the comparison between climate simulations and reconstructions in past periods the climatic sensitivity to specific agents can be checked. Therefore, this study goals to evaluate the responses of oceanic and atmospheric components to change in the Antarctic topography of changes in the Earth's orbital parameters. To this end, we used the global coupled climate model SPEEDY-NEMO. Four experiments are performed: a control simulation (CONTROL) and three sensitivity simulations (MIS31, ORBIT and TOP). To assess the performance of the SPEEDY-NEMO in represent the current climate the CONTROL was compared with reanalysis, where it was noticed that the main aspects of the climate were well represented by the model with standard deviations very similar to those found in the reanalysis. However, the sea ice still needs improvements in its representation. In the sensitivity experiments, positive anomalies of air and ocean temperatures over the northern hemisphere (NH) influenced by orbital conditions were identified. In the simulations with orbital changes, significant variations observed in surface winds and precipitation are noticed, such as the absence of South American and African monsoon during the austral summer. Astronomical changes also influenced the ENSO. Indeed, anomalous condition resemble a permanent El Niño, i.e. higher SST compared with the CONTROL. Oceanic transport changes have also been identified toward to the high latitudes of the NH. It was also observed that the change in the topography of Antarctica exerts a significant influence on the ocean-atmosphere system of the high latitudes of the southern hemisphere.
2
Knutz, Paul C. "Late Pleistocene glacial fluctuations and palaeoceanography on the continental margin of north-west Britain." Thesis, Cardiff University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247749.
Full text
3
Korotkikh, Elena. "A High Resolution Record of the Eemian Interglacial and Transition to the Next Glacial Period from Mount Moulton (West Antarctica)." Fogler Library, University of Maine, 2009. http://www.library.umaine.edu/theses/pdf/KorotkikhE2009.pdf.
Full text
4
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.
Full textAbstract:
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.
5
Le, Meur Emmanuel. "Spécificité de l'isostasie en contexte glaciaire : présentation et application d'un modèlede réponse terrestre." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10058.
Full textAbstract:
Sous l'effet de charges en surface, la terre s'affaisse pour retrouver un etat d'equilibre isostatique. Inversement, quand ces charges viennent a disparaitre, la surface remonte pour retrouver sa configuration initiale. Dans le cas d'une calotte glaciaire, la taille mais aussi la vitesse a laquelle peut evoluer la masse de glace est a l'origine d'une reponse hautement specifique et particulierement de comportements transitoires associes. Apres avoir introduit la notion d'isostasie, nous decrivons quelles peuvent etre les consequences a la fois de la taille et de la vitesse d'evolution de la charge sur la reponse terrestre. Cela permet de preciser la specificite du contexte glaciaire en matiere de charge a la surface de la terre. Ensuite sont presentes les nombreux impacts que cette reponse isostatique peut avoir en retour sur la dynamique glaciaire, ainsi que les facons d'en rendre compte. Cette premiere partie aura montre tout l'interet de developper un modele de terre elabore, dont la physique a la base s'avere plus rigoureuse que dans les parametrisations usuelles utilisees jusqu'a maintenant dans les modeles de glace. Les caracteristiques majeures ainsi que les equations a la base de ce modele sont alors presentees en detail et revelent le degre de sophistication de cette nouvelle approche. La richesse de donnees issues de mesures sur les zones de rebond postglaciaire comme la fennoscandie sont un excellent moyen de valider ce genre de modele. En comparant les resultats du rebond simule avec ces donnees il est possible d'estimer le realisme du modele. Bien que l'ensemble de ces donnees ne soit pas simultanement reproduit de maniere parfaite, le modele montre cependant un comportement suffisamment realiste pour pouvoir par la suite etre couple a un modele de glace. Les resultats de cette incorporation sont alors compares a ceux obtenus avec les parametrisations usuelles au cours d'une simulation l'evolution de la calotte antarctique au cours du dernier cycle glaciaire. Ces resultats confirment le relativement bon comportement de notre modele complet de terre par rapport aux autres approches, ce qui tendrait a discrediter l'emploi de certaines de ces parametrisations de la reponse terrestre dans les modeles evolutifs de calottes glaciaires
6
Fabre, Adeline. "Modélisation 3D de l'écoulement des calottes glaciaires : application à la calotte du Groenland et aux calottes de l'hémisphère nord au dernier maximum glaciaire." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10014.
Full textAbstract:
Le systeme climatique terrestre est forme de plusieurs composantes qui interagissent etroitement (atmosphere, calottes de glace, oceans, lithosphere et biosphere). La modelisation numerique permet d'etudier ces interactions. Dans ce travail, l'ecoulement de plusieurs calottes glaciaires est modelise et on s'attache particulierement a l'etude de leurs interactions avec l'atmosphere. Celles-ci sont determinees par l'altitude de la surface de la calotte, les temperatures en surface et l'accumulation. Un modele 3d d'ecoulement de calotte glaciaire, developpe au sein de l'equipe modelisation du lgge, est presente. Il est teste sur une calotte theorique dans le cadre d'un projet europeen d'intercomparaison de modeles. Il est ensuite applique a la calotte du groenland, en simulant la reponse de la calotte sous des climats differents du climat actuel et en etudiant son evolution au cours du dernier cycle interglaciaire-glaciaire. La sensibilite du modele a la parametrisation de l'accumulation est mise en evidence. Le modele est enfin applique a la reconstruction des calottes de glace presentes dans l'hemisphere nord (laurentide et fennoscandie) au dernier maximum glaciaire (il y a environ 21 000 ans). Trois methodes sont utilisees pour calculer les conditions climatiques en entree du modele. Dans les deux premieres, ces conditions sont determinees par une parametrisation calibree sur les valeurs actuelles: les resultats ainsi obtenus ne sont pas satisfaisants. La troisieme methode utilise les temperatures en surface et les precipitations issues de simulations du climat du dernier maximum glaciaire, realisees avec le modele de circulation generale de l'atmosphere du lmd. Le couplage entre les deux modeles necessite un traitement de donnees complexe, mais les calottes obtenues sont en meilleur accord avec les donnees geologiques sur l'extension et l'epaisseur des calottes a cette epoque
7
Krinner, Gerhard. "Simulations du climat des calottes de glace." Phd thesis, Université Joseph Fourier (Grenoble), 1997. http://tel.archives-ouvertes.fr/tel-00716408.
Full textAbstract:
Ce travail traite de la simulation numérique du climat des grandes calottes de glace, en particulier des calottes de l'Antarctique et du Groenland, toujours existantes, dans des conditions climatiques différentes, à l'aide de modèles de circulation générale de l'atmosphère (MCGA). Le MCGA à grille variable LMDz a été adapté aux spécificités du climat polaire et validé pour le climat actuel. L'approche d'une grille variable, qui permet d'utiliser le MCGA à haute résolution spatiale (autour de 100 km) sur la région d'intérêt à un coût numérique raisonnable, a été validée en analysant la dynamique atmosphérique au bord de la région ciblée à l'aide d'un schéma de suivi des cyclones individuels. Des simulations du climat du Dernier Maximum Glaciaire (DMG) ont été faites pour le Groenland et l'Antarctique et analysées en tenant compte des archives glaciaires disponibles. Une explication possible des différences entre les deux méthodes principales de reconstruction des paléotempératures - l'analyse des isotopes de l'eau et la mesure directe de la température de la glace dans le trou de forage - au centre du Groenland a pu être proposée. Cette explication est basée sur des changements de paramètres climatiques locaux. C'est la première fois que l'approche de grille variable a été utilisée dans un MCGA pour des simulations du climat polaire à l'échelle de quelques années. Les simulations paléoclimatiques faites avec LMDz sont à une résolution spatiale inégalée à ce jour. Finalement, le climat du DMG, simulé par plusieurs MCGA dans le cadre du projet international PMIP (Paleoclimate Modelling Intercomparison Programme), a été analysé, et des implications des résultats pour l'interprétation des enregistrements glaciaires ont été discutées.
8
Bintz, Pierre. "Du Tardiglaciaire à l'Holocène dans les alpes du nord françaises : approches chronostratigraphique, paléoclimatique et culturelle." Phd thesis, Université Joseph Fourier (Grenoble), 1994. https://tel.archives-ouvertes.fr/tel-00723796.
Full textAbstract:
Les donnees sur la transition tardiglaciaire-holocene (de 14500 a 6000 bp) s'appuient sur les resultats livres par le gisement de st. Thibaud-de-couz (savoie, chartreuse) et une dizaine de sites a stratigraphies developpees qui ont fait l'objet de fouilles recentes. Ces sites representent des remplissages karstiques qui permettent d'avoir une vision precise mais ponctuelle sur les modalites du passage du dernier glaciaire a l'interglaciaire actuel. L'approche chronostratigraphique assure les bases chronologiques des evolutions naturelles et culturelles. L'etude d'une douzaine de sequences stratigraphiques a permis de distinguer quelques types d'enregistrement sedimentaire propres a chaque phase de l'evolution climato-sedimentaire. La reconstruction de l'evolution paleoclimatique a ete faite selon deux approches complementaires: 1) la sedimentologie met particulierement en evidence les manifestations de l'humidite qui sous climat froid engendre une importante sedimentation detritique et sous climat chaud des depots carbonates ; 2) l'etude des faunes de mollusques terrestres permet de preciser les conditions paleoecologiques et climatiques locales ; la presence d'une association a columella de type periglaciaire est significative. Les resultats mettent particulierement en evidence le caractere instable du climat. Le probleme des occupations humaines est aborde a travers l'etude des outillages lithiques sous deux aspects: 1) l'etude petrographique permet de localiser les gites d'approvisionnement en silex et d'avoir des indications sur les territoires parcourus ; 2) la caracterisation des systemes culturels est basee sur les series lithiques considerees en terme d'ensembles structures ; dans ce but une methode de classement hierarchise est proposee. Les grandes etapes de l'evolution chronoculturelle sont precisees ; elles sont marquees par de profondes mutations qui caracterisent les cultures de la fin du paleolithique superieur au mesolithique et par l'emergence des premieres phases de la neolithisation. Une synthese integrant l'ensemble des donnees bioclimatiques et culturelles permet de proposer un modele de transition dernier glaciaire-interglaciaire actuel caracterisee par une succession de cycles a regimes climatiques contrastes situes a la charniere de deux periodes a climats plus stables. La mise en parallele des donnees culturelles suggere une relation forte entre evolutions culturelles et changements bioclimatiques
9
Coletti, Anthony J. "A Gcm Comparison of Plio-Pleistocene Interglacial-Glacial Periods in Relation to Lake El’gygytgyn, Ne Arctic Russia." 2013. https://scholarworks.umass.edu/theses/1113.
Full textAbstract:
Until now, the lack of time-continuous, terrestrial paleoenvironmental data from the Pleistocene Arctic has made model simulations of past interglacials difficult to assess. Here, we compare climate simulations of four warm interglacials at Marine Isotope Stage (MIS) 1 (9ka), 5e (127 ka), 11c (409 ka), and 31 (1072 ka) with new proxy climate data recovered from Lake El’gygytgyn, NE Russia. Climate reconstructions of the Mean Temperature of the Warmest Month (MTWM) indicate conditions 2.1, 0.5 and 3.1 ºC warmer than today during MIS 5e, 11c, and 31 respectively. While the climate model captures much of the observed warming during each interglacial, largely in response to boreal summer orbital forcing, the extraordinary warmth of MIS 11c relative to the other interglacials in the proxy records remain difficult to explain. To deconvolve the contribution of multiple influences on interglacial warming at Lake El’gygytgyn, we isolated the influence of vegetation, sea ice, and circum-Arctic land ice feedbacks on the climate of the Beringian interior. Vegetation-land surface feedback simulations during all four interglacials show expanding boreal forest cover with increasing summer insolation intensity. A deglaciated Greenland is shown to have a minimal effect on Northeast Asian temperature during the warmth of stage 11c and 31 (Melles et al., 2012). A prescribed enhancement of oceanic heat transport into the Arctic ocean has some effect on Beringian climate, suggesting intrahemispheric coupling seen in comparisons between Lake El’gygytgyn and Antarctic sediment records might be related to linkages between Antarctic ice volume and ocean circulation. The exceptional warmth of MIS 11c remains enigmatic however, relative to the modest orbital and greenhouse gas forcing during that interglacial. Large Northern Hemisphere ice sheets during Plio-Pleistocene glaciation causes a substantial decrease in Mean Temperature of the Coldest Month (MTCM) and Mean Annual Precipitation (PANN) causing significant Arctic aridification. Aridification and frigid conditions can be linked to a combination of mechanical forcing from the Laurentide and Fennoscandian ice sheets on mid-tropospheric westerly flow and expanded sea-ice cover causing albedo-enhanced feedback.
Books on the topic "Periodo glacial - Pleistoceno"
1
Gibbard, Philip L. Pleistocene history of the Lower Thames Valley. Cambridge [England]: Cambridge University Press, 1994.
Find full text
2
The Pleistocene History of the Middle Thames Valley. Cambridge: Cambridge University Press, 1985.
Find full text
3
Bar-Yosef, Ofer, Miryam Bar-Matthews, and Avner Ayalon. 12,000–11,700 cal BP. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780199329199.003.0002.
Full textAbstract:
We take up the question of “why” cultivation was adopted by the end of the Younger Dryas by reviewing evidence in the Levant, a sub-region of southwestern Asia, from the Late Glacial Maximum through the first millennium of the Holocene. Based on the evidence, we argue that the demographic increase of foraging societies in the Levant at the Terminal Pleistocene formed the backdrop for the collapse of foraging adaptations, compelling several groups within a particular “core area” of the Fertile Crescent to become fully sedentary and introduce cultivation alongside intensified gathering in the Late Glacial Maximum, ca. 12,000–11,700 cal BP. In addition to traditional hunting and gathering, the adoption of stable food sources became the norm. The systematic cultivation of wild cereals begun in the northern Levant resulted in the emergence of complex societies across the entire Fertile Crescent within several millennia. Results of archaeobotanical and archaeozoological investigations provide a basis for reconstructing economic strategies, spatial organization of sites, labor division, and demographic shifts over the first millennium of the Holocene. We draw our conclusion from two kinds of data from the Levant, a sub-region of southwestern Asia, during the Terminal Pleistocene and early Holocene: climatic fluctuations and the variable human reactions to natural and social calamities. The evidence in the Levant for the Younger Dryas, a widely recognized cold period across the northern hemisphere, is recorded in speleothems and other climatic proxies, such as Dead Sea levels and marine pollen records.
4
Holmes, Jonathan, and Philipp Hoelzmann. The Late Pleistocene-Holocene African Humid Period as Evident in Lakes. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190228620.013.531.
Full textAbstract:
From the end of the last glacial stage until the mid-Holocene, large areas of arid and semi-arid North Africa were much wetter than present, during the interval that is known as the African Humid Period (AHP). During this time, large areas were characterized by a marked increase in precipitation, an expansion of lakes, river systems, and wetlands, and the spread of grassland, shrub land, and woodland vegetation into areas that are currently much drier. Simulations with climate models indicate that the AHP was the result of orbitally forced increase in northern hemisphere summer insolation, which caused the intensification and northward expansion of the boreal summer monsoon. However, feedbacks from ocean circulation, land-surface cover, and greenhouse gases were probably also important.Lake basins and their sediment archives have provided important information about climate during the AHP, including the overall increases in precipitation and in rates, trajectories, and spatial variations in change at the beginning and the end of the interval. The general pattern is one of apparently synchronous onset of the AHP at the start of the Bølling-Allerød interstadial around 14,700 years ago, although wet conditions were interrupted by aridity during the Younger Dryas stadial. Wetter conditions returned at the start of the Holocene around 11,700 years ago covering much of North Africa and extended into parts of the southern hemisphere, including southeastern Equatorial Africa. During this time, the expansion of lakes and of grassland or shrub land vegetation over the area that is now the Sahara desert, was especially marked. Increasing aridity through the mid-Holocene, associated with a reduction in northern hemisphere summer insolation, brought about the end of the AHP by around 5000–4000 years before present. The degree to which this end was abrupt or gradual and geographically synchronous or time transgressive, remains open to debate. Taken as a whole, the lake sediment records do not support rapid and synchronous declines in precipitation and vegetation across the whole of North Africa, as some model experiments and other palaeoclimate archives have suggested. Lake sediments from basins that desiccated during the mid-Holocene may have been deflated, thus providing a misleading picture of rapid change. Moreover, different proxies of climate or environment may respond in contrasting ways to the same changes in climate. Despite this, there is evidence of rapid (within a few hundred years) termination to the AHP in some regions, with clear signs of a time-transgressive response both north to south and east to west, pointing to complex controls over the mid-Holocene drying of North Africa.
5
The Late Glacial in north-west Europe: Human adaptation and environmental change at the end of the Pleistocene. London: Council for British Archaeology, 1991.
Find full text
6
Notice of tertiary fossils from Labrador, Maine, &c.: And remarks on the climate of Canada, in the newer Pliocene or Pleistocene period. [S.l: s.n., 1987.
Find full text
7
Lurcock, Pontus, and Fabio Florindo. Antarctic Climate History and Global Climate Changes. Oxford University Press, 2017. http://dx.doi.org/10.1093/oxfordhb/9780190676889.013.18.
Full textAbstract:
Antarctic climate changes have been reconstructed from ice and sediment cores and numerical models (which also predict future changes). Major ice sheets first appeared 34 million years ago (Ma) and fluctuated throughout the Oligocene, with an overall cooling trend. Ice volume more than doubled at the Oligocene-Miocene boundary. Fluctuating Miocene temperatures peaked at 17–14 Ma, followed by dramatic cooling. Cooling continued through the Pliocene and Pleistocene, with another major glacial expansion at 3–2 Ma. Several interacting drivers control Antarctic climate. On timescales of 10,000–100,000 years, insolation varies with orbital cycles, causing periodic climate variations. Opening of Southern Ocean gateways produced a circumpolar current that thermally isolated Antarctica. Declining atmospheric CO2 triggered Cenozoic glaciation. Antarctic glaciations affect global climate by lowering sea level, intensifying atmospheric circulation, and increasing planetary albedo. Ice sheets interact with ocean water, forming water masses that play a key role in global ocean circulation.
8
Lurcock, Pontus, and Fabio Florindo. Antarctic Climate History and Global Climate Changes. Oxford University Press, 2017. http://dx.doi.org/10.1093/oxfordhb/9780190699420.013.18.
Full textAbstract:
Antarctic climate changes have been reconstructed from ice and sediment cores and numerical models (which also predict future changes). Major ice sheets first appeared 34 million years ago (Ma) and fluctuated throughout the Oligocene, with an overall cooling trend. Ice volume more than doubled at the Oligocene-Miocene boundary. Fluctuating Miocene temperatures peaked at 17–14 Ma, followed by dramatic cooling. Cooling continued through the Pliocene and Pleistocene, with another major glacial expansion at 3–2 Ma. Several interacting drivers control Antarctic climate. On timescales of 10,000–100,000 years, insolation varies with orbital cycles, causing periodic climate variations. Opening of Southern Ocean gateways produced a circumpolar current that thermally isolated Antarctica. Declining atmospheric CO2 triggered Cenozoic glaciation. Antarctic glaciations affect global climate by lowering sea level, intensifying atmospheric circulation, and increasing planetary albedo. Ice sheets interact with ocean water, forming water masses that play a key role in global ocean circulation.
9
Weiss, Harvey, ed. Megadrought and Collapse. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780199329199.001.0001.
Full textAbstract:
This is the first book to treat the major examples of megadrought and societal collapse, from the late Pleistocene end of hunter–gatherer culture and origins of cultivation to the 15th century AD fall of the Khmer Empire capital at Angkor, and ranging from the Near East to South America. Previous enquiries have stressed the possible multiple and internal causes of collapse, such overpopulation, overexploitation of resources, warfare, and poor leadership and decision-making. In contrast, Megadrought and Collapse presents case studies of nine major episodes of societal collapse in which megadrought was the major and independent cause of societal collapse. In each case the most recent paleoclimatic evidence for megadroughts, multiple decades to multiple centuries in duration, is presented alongside the archaeological records for synchronous societal collapse. The megadrought data are derived from paleoclimate proxy sources (lake, marine, and glacial cores; speleothems, or cave stalagmites; and tree-rings) and are explained by researchers directly engaged in their analysis. Researchers directly responsible for them discuss the relevant current archaeological records. Two arguments are developed through these case studies. The first is that societal collapse in different time periods and regions and at levels of social complexity ranging from simple foragers to complex empires would not have occurred without megadrought. The second is that similar responses to megadrought extend across these historical episodes: societal collapse in the face of insurmountable climate change, abandonment of settlements and regions, and habitat tracking to sustainable agricultural landscapes. As we confront megadrought today, and in the likely future, Megadrought and Collapse brings together the latest contributions to our understanding of past societal responses to the crisis on an equally global and diverse scale.
Book chapters on the topic "Periodo glacial - Pleistoceno"
1
Wiedmer, R. Michael, Alan R. Gillespie, David R. Montgomery, and Harvey M. Greenberg. "Further evidence for the Matanuska megaflood hypothesis, Alaska." In Untangling the Quaternary Period—A Legacy of Stephen C. Porter. Geological Society of America, 2021. http://dx.doi.org/10.1130/2021.2548(19).
Full textAbstract:
ABSTRACT The Matanuska lowland north of Anchorage, Alaska, was episodically glaciated during the Pleistocene by the merged westward flow of the Matanuska and Knik glaciers. During the late Wisconsin glaciation, glacial Lake Atna filled the Copper River Basin, impounded by an ice dam blocking the Matanuska drainage divide at Tahneta Pass and the adjacent Squaw Creek headwaters and ice dams at other basin outlets, including the Susitna and Copper rivers. On the Matanuska lowland floor upvalley from the coalesced glacier’s late-Wisconsin terminus, a series of regularly spaced, symmetrical ridges with 0.9-km wavelengths and heights to 36 m are oriented normal to oblique to the valley and covered by smaller subparallel ridges with wavelengths typically ~80 m and amplitudes to 3 m. These and nearby drumlins, eskers, and moraines were previously interpreted to be glacial in origin. Borrow-pit exposures in the large ridges, however, show sorting and stratification, locally with foreset bedding. A decade ago we reinterpreted such observations as evidence of outburst flooding during glacial retreat, driven by water flushing from Lake Atna through breaches in the Tahneta Pass and Squaw Creek ice dam. In this view, the ridges once labeled Rogen and De Geer moraines were reinterpreted as two scales of fluvial dunes. New observations in the field and from meter-scale light detection and ranging (LiDAR) and interferometric synthetic aperture radar (IfSAR) digital elevation models, together with grain-size analyses and ground-penetrating radar profiles, provide further evidence that portions of the glacial landscape of the Matanuska lowlands were modified by megaflooding after the Last Glacial Maximum, and support the conclusion that the Knik Glacier was the last active glacier in the lowland.
2
Bianchi, Thomas S. "The Holocene and Global Climate Change." In Deltas and Humans. Oxford University Press, 2016. http://dx.doi.org/10.1093/oso/9780199764174.003.0008.
Full textAbstract:
The Pleistocene Epoch, often referred to as the Ice Age, lasted from approximately 2.6 million to 11,700 years ago. The last major ice advance began about 110,000 years ago, and the most recent episode of maximum ice coverage, the Last Glacial Maximum, began about 26,500 years ago and ended approximately 19,000 years ago. Thereafter, glacier retreat began, largely ending by about 11,700 years ago. That marked the beginning of the Holocene interglacial geologic epoch, which continues to the present. During the last glacial period, sea level was much lower because so much water was locked up in ice sheets, largely at the poles. This lowering of the sea level exposed the margins of the continents (the continental shelves) around the world. When the Ice Age ended, sea level started to rise during the deglacial period, a process that continued into the Holocene. Deltaic regions received meltwaters from the thawing glaciers, along with glacier- derived sediments. Of particular note in the late Holocene is a climate episode called the Medieval Warm Period, originally identified by the English botanist Hubert Lamb. The Medieval Warm Period was a time of warm climate in the North Atlantic region and may have also impacted other areas around the world. It lasted from about the years 950 to 1250. Later in this chapter, I will discuss this climate anomaly, along with something called the “Hockey Stick” debate, which relates to exceptional warming during recent centuries of the Holocene (i.e., global warming). In any case, all modern and paleodeltas formed during periods of peak sea level in the Holocene. These new deltas had fertile soils that were constantly irrigated by the flow of fresh water, which promoted early settlement by humans. So, the Holocene started near the end of the retreat of the Pleistocene glaciers, and human civilizations arose entirely in the Holocene Epoch. To view the Holocene, simply look around you today. In this chapter, I will explore the natural and human-induced causes of global climate change and how they impact deltaic regions.
3
Denlinger, Roger P., David L. George, Charles M. Cannon, Jim E. O’Connor, and Richard B. Waitt. "Diverse cataclysmic floods from Pleistocene glacial Lake Missoula." In Untangling the Quaternary Period—A Legacy of Stephen C. Porter, 333–50. Geological Society of America, 2021. http://dx.doi.org/10.1130/2021.2548(17).
Full textAbstract:
ABSTRACT In late Wisconsin time, the Purcell Trench lobe of the Cordilleran ice sheet dammed the Clark Fork of the Columbia River in western Montana, creating glacial Lake Missoula. During part of this epoch, the Okanogan lobe also dammed the Columbia River downstream, creating glacial Lake Columbia in northeast Washington. Repeated failure of the Purcell Trench ice dam released glacial Lake Missoula, causing dozens of catastrophic floods in eastern Washington that can be distinguished by the geologic record they left behind. These floods removed tens of meters of pale loess from dark basalt substrate, forming scars along flowpaths visible from space. Different positions of the Okanogan lobe are required for modeled Missoula floods to inundate the diverse channels that show field evidence for flooding, as shown by accurate dam-break flood modeling using a roughly 185 m digital terrain model of existing topography (with control points dynamically varied using automatic mesh refinement). The maximum extent of the Okanogan lobe, which blocked inundation of the upper Grand Coulee and the Columbia River valley, is required to flood all channels in the Telford scablands and to produce highest flood stages in Pasco Basin. Alternatively, the Columbia River valley must have been open and the upper Grand Coulee blocked to nearly match evidence for high water on Pangborn bar near Wenatchee, Washington, and to flood Quincy Basin from the west. Finally, if the Columbia River valley and upper Grand Coulee were both open, Quincy Basin would have flooded from the northeast. In all these scenarios, the discrepancy between modeled flood stages and field evidence for maximum flood stages increases in all channels downstream, from Spokane to Umatilla Basin. The pattern of discrepancies indicates that bulking of floods by loess increased flow volume across the scablands, but this alone does not explain low modeled flow stages along the Columbia River valley near Wenatchee. This latter discrepancy between modeled flood stages and field data requires either additional bulking of flow by sediment along the Columbia reach downstream of glacial Lake Columbia, or coincident dam failures of glacial Lake Columbia and glacial Lake Missoula.
4
Waitt, Richard B. "Roads less travelled by—Pleistocene piracy in Washington’s northwestern Channeled Scabland." In Untangling the Quaternary Period—A Legacy of Stephen C. Porter, 351–84. Geological Society of America, 2021. http://dx.doi.org/10.1130/2021.2548(18).
Full textAbstract:
ABSTRACT The Pleistocene Okanogan lobe of Cordilleran ice in north-central Washington State dammed Columbia River to pond glacial Lake Columbia and divert the river south across one or another low spot along a 230-km-long drainage divide. When enormous Missoula floods from the east briefly engulfed the lake, water poured across a few such divide saddles. The grandest such spillway into the Channeled Scabland became upper Grand Coulee. By cutting headward to Columbia valley, upper Grand Coulee’s flood cataract opened a valve that then kept glacial Lake Columbia low and limited later floods into nearby Moses Coulee. Indeed few of the scores of last-glacial Missoula floods managed to reach it. Headward cutting of an inferred smaller cataract (Foster Coulee) had earlier lowered glacial Lake Columbia’s outlet. Such Scabland piracies explain a variety of field evidence assembled here: apparently successive outlets of glacial Lake Columbia, and certain megaflood features downcurrent to Wenatchee and Quincy basin. Ice-rafted erratics and the Pangborn bar of foreset gravel near Wenatchee record late Wisconsin flood(s) down Columbia valley as deep as 320 m. Fancher bar, 45 m higher than Pangborn bar, also has tall foreset beds—but its gravel is partly rotted and capped by thick calcrete, thus pre-Wisconsin age, perhaps greatly so. In western Quincy basin foreset beds of basaltic gravel dip east from Columbia valley into the basin—gravel also partly rotted and capped by thick calcrete, also pre-Wisconsin. Yet evidence of late Wisconsin eastward flow to Quincy basin is sparse. This sequence suggests that upper Grand Coulee had largely opened before down-Columbia megaflood(s) early in late Wisconsin time. A drift-obscured area of the Waterville Plateau near Badger Wells is the inconspicuous divide saddle between Columbia tributary Foster Creek drainage and Moses Coulee drainage. Before flood cataracts had opened upper Grand Coulee or Foster Coulee, and while Okanogan ice blocked the Columbia but not Foster Creek, glacial Lake Columbia (diverted Columbia River) drained over this saddle at about 654 m and down Moses Coulee. When glacial Lake Columbia stood at this high level so far west, Missoula floods swelling the lake could easily and deeply flood Moses Coulee. Once eastern Foster Coulee cataract had been cut through, and especially once upper Grand Coulee’s great cataract receded to Columbia valley, glacial Lake Columbia stood lower, and Moses Coulee became harder to flood. During the late Wisconsin (marine isotope stage [MIS] 2), only when Okanogan-lobe ice blocked the Columbia near Brewster to form a high lake could Missoula floodwater from glacial Lake Missoula rise enough to overflow into Moses Coulee—and then only in a few very largest Missoula floods. Moses Coulee’s main excavation must lie with pre-Wisconsin outburst floods (MIS 6 or much earlier)—before upper Grand Coulee’s cataract had receded to Columbia valley.
5
Wignall, Paul B. "6. What happened to the Ice Age megafauna?" In Extinction: A Very Short Introduction, 96–116. Oxford University Press, 2019. http://dx.doi.org/10.1093/actrade/9780198807285.003.0006.
Full textAbstract:
The Ice Age or Pleistocene Period, from 2.6 million to 11,650 years ago, was a time when the climate cycled from glacial to interglacial states every 100,000 years or so, resulting in significant sea-level changes. During the last glacial maximum, numerous large, terrestrial animals disappeared, now termed the Pleistocene megafauna extinction. Its cause has been one of the most highly contested topics in palaeontology in recent years. ‘What happened to the Ice Age megafauna?’ describes how although the losses overall were trivial compared to the scale experienced during the big five mass extinctions, they were highly selective and very similar on all continents. The two main culprits proposed have been climate change and humans.
6
Elias, Scott. "Millennial and Century Climate Changes in the Colorado Alpine." In Climate Variability and Ecosystem Response in Long-Term Ecological Research Sites. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195150599.003.0033.
Full textAbstract:
Ecosystems are the products of regional biotic history, shaped by environmental changes that have occurred over thousands of years. Accordingly, ecological changes take place at many timescales, but perhaps none is more significant than the truly long-term scale of centuries and millennia, for it is at these timescales that ecosystems form, break apart, and reform in new configurations. This is certainly true in the alpine regions, where glaciations have dominated the landscape for perhaps 90% of the last 2.5 million years (Elias 1996a). In the alpine tundra zone, the periods between ice ages have been relatively brief (10,000–15,000 years), whereas glaciations have been long (90,000–100,000 years). Glacial ice has been the dominant force in shaping alpine landscapes. Glacial climate has been the filter through which the alpine biota has had to pass repeatedly in the Pleistocene. This chapter discusses climatic events during the last 25,000 years (figure 18.1). At the beginning of this interval, temperatures cooled throughout most of the Northern Hemisphere, culminating in the last glacial maximum (LGM), about 20,000–18,000 yr b.p. (radiocarbon years before present). The Laurentide and Cordilleran ice sheets advanced southward, covering most of Canada and the northern tier of the United States. Glaciers also crept down from mountaintops to fill high valleys in the Rocky Mountains. In the Southern Rockies, the alpine tundra zone crept downslope into what is now the subalpine, beyond the reach of the relatively small montane glaciers. By about 14,000 yr b.p., the glacier margins began to recede, leading eventually to the postglacial environments of the Holocene. It is now becoming apparent that the climate changes that drove these events were surprisingly rapid and intense. This chapter examines the evidence for these climatic changes and the biotic response to them in the alpine zone of Colorado. To reconstruct the environmental changes of this period, we must rely on proxy data, that is, the fossil record of plants and animals, combined with geologic evidence, such as the age and location of glacial moraines in mountain valleys. As of this writing, the principal biological proxy data that have been studied in the Rocky Mountains are fossil pollen and insects.
7
Graham, Alan. "Quaternary North American Vegetational History: 1.6 Ma to the Present." In Late Cretaceous and Cenozoic History of North American Vegetation (North of Mexico). Oxford University Press, 1999. http://dx.doi.org/10.1093/oso/9780195113426.003.0011.
Full textAbstract:
The Quaternary Period encompasses the Pleistocene and the Holocene or Recent Epochs. The date used for the beginning of the Pleistocene depends upon which globally recognizable event is selected as representing a significant break with the preceding Pliocene Epoch. Candidates include the Gauss-Matuyama magnetopolarity boundary (~2.8 Ma; see Quaternary International, 1997); the initiation of widespread permafrost, a frigid Arctic Ocean, and rapid glaciation in the high northern latitudes (~2.4 Ma; Shackleton and Opdyke, 1977; Shackleton et al., 1984); or the African Olduvai paleomagnetic event between 1.87 and 1.67 Ma. The transition from hothouse to icehouse conditions was gradual, but the Pleistocene is typified at Vrica, Italy, as beginning at ~1.67 Ma (Aguirre and Pasini, 1985; Richmond and Fullerton, 1986; oxygen isotope stage 62), and that is the date used here. In the conterminous United States the Elk Creek till of Nebraska is 2.14 m.y. in age (Hallberg, 1986), and the onset of the full ice age is represented by the onset of repeated glaciations at ~850 Kya when glaciers extended down the Mississippi River Valley. Subsequently, glacial-interglacial conditions fluctuated until the latest retreat at ~11 Kya that began the Holocene or Recent Epoch. The chronology of ice age events began with the publication of Louis Agassiz’s (1840) Etudes surles Glaciers. In the absence of evidence to the contrary, a single glacial advance was envisioned as blanketing the high latitudes. In the 1940s Willard E Libby at the University of Chicago perfected the technique of radiocarbon dating, and Flint and Rubin (1955) applied this methodology of “isotopic clocks” to establishing the absolute chronology of drift deposits from the eastern and midwestern United States. Their radiocarbon dates showed evidence of two or more times of continental-scale glaciations; older organic material was “radiocarbon inert” and beyond the ~40-Ky range of the technique. A standard chronology eventually became established for North America that included four major glacial stages (Nebraskan, oldest; Kansan; Illinoian; and Wisconsin) separated by four interglacials (Aftonian, oldest; Yarmouth, Sangamon, and the present Holocene).
8
Stevenson, Janelle. "Vegetation and climate of the Last Glacial Maximum in Sulawesi." In The Archaeology of Sulawesi: Current Research on the Pleistocene to the Historic Period, 17–29. ANU Press, 2018. http://dx.doi.org/10.22459/ta48.11.2018.03.
Full text
9
Emery, K. O., and David Neev. "Synopsis." In The Destruction of Sodom, Gomorrah, and Jericho. Oxford University Press, 1995. http://dx.doi.org/10.1093/oso/9780195090949.003.0010.
Full textAbstract:
The two large lakes named Samra and Lisan existed in the Dead Sea graben from 350,000 to 120,000B.p. and 60,000 to 12,000B.p. Their sediments tentatively are correlated with the European Riss and Würm glacial epochs. Thick marls are the chief sediments in the deep water north basin. Rocksalt deposition dominated within the troughs of both north and south basins throughout the intervening Riss-Würm Interglacial stage. Lithology of Lisan Formation (Würm) in that basin indicates rapid and extreme fluctuations of level. Eight major climatic cycles are recorded during Würm glaciation when the level fluctuated between -180 m m.s.l. and probably lower than -400 m m.s.l. Rocksalt was deposited within both basins during warm dry phases of the Lisan stage. At the present state of knowledge no specific tectonic or volcanic activities can be tied to these climatic events. The Holocene Period was similar lithologically to that of the Lisan Formation and transition between them was gradual. Primarily the difference between the two was change in relative time span between alternate wet and dry phases. Dry phases of Holocene gradually became longer while wet ones with Dead Sea transgressions became shorter. Tectonic regimes during the first part—the Natufian age to Early Bronze III, 12,000 to 4400 B.P.—seem to have been milder than later ones, end of Early Bronze III to the present. The severe earthquake that destroyed Sodom and Gomorrah in 4350 B.P. was followed by a 300-year long subphase of gradually warming climate that became extremely dry during the latter part of the Intermediate Bronze age. Climatic Wet Phase III began about 3900 B.P. It was the longest, about 800 years, and most intense wet phase of Holocene and it probably was associated with volcanism. No abrupt cultural or demographic changes are known during transition from Epi-Paleolithic or Geometric Kebaran from the last glacial phase of the Pleistocene Period through Natufian to the early part of Holocene Pre-Pottery Neolithic. The reason for this stability is not clear especially because average temperatures of global oceans during the latest Pleistocene glaciation were appreciably lower than those during Early Holocene (Emiliani, 1978).
10
Smith, Robert B., and Lee J. Siegel. "Ice over Fire: Glaciers Carve the Landscape." In Windows into the Earth. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195105964.003.0010.
Full textAbstract:
Yellowstone, the Tetons, and Jackson Hole were shaped by multiple catastrophes. Huge volcanic eruptions and powerful earthquakes played major roles. Finishing touches were added by another kind of calamity: A rare global Ice Age produced gigantic glaciers that buried the landscape with ice two-thirds of a mile thick in places. The glaciers carved mountains, canyons, and lake basins. They dumped large piles of debris and redirected the flow of rivers. The Yellowstone—Teton region is a world-class example of how land was reshaped by glaciers during what is known as the Pleistocene Ice Age. The Ice Age was not a single glacial period, but many intermittent cold spells interspersed with warmer periods during which the ice melted. The timing of major glacial periods is notoriously uncertain. Although continental ice sheets did not quite reach as far south as Yellowstone, a regional icecap and large glaciers covered the Yellowstone—Teton country during three major episodes of at least the past 300,000 years—and perhaps the past 2 million years. The last of these big glaciers retreated about 14,000 years ago, although some argue they did not recede until 10,000 to 12,000 years ago. Today, small glaciers in the Teton Range are found only above 10,000 feet. During each major episode, most of Yellowstone National Park was buried beneath an icecap as much as 3,500 feet thick, among the largest in the ancient Rocky Mountains. Gigantic masses of ice flowed down from the high Yellowstone Plateau, carving and scouring the Earth’s surface, diverting and damming rivers into their present forms, steepening mountain fronts, and deepening lakes. The ice helped sculpt the Grand Canyon of the Yellowstone. More than anything, the thick ice scraped Yellowstone’s volcanic topography, further smoothing the plateau and helping to excavate the basin occupied by Yellowstone Lake. Jackson Hole became a rendezvous of glaciers converging from the north, north-east, and west. Ice up to 2,000 feet thick scooped out the valley floor. The glaciers left tall ridges of rocky debris now covered by lush conifer forests. Such ridges, called moraines, helped shape Jackson Lake.