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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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Carrara, Paul E. "Holocene and latest Pleistocene glacial chronology, Glacier National Park, Montana." Canadian Journal of Earth Sciences 24, no. 3 (March 1, 1987): 387–95. http://dx.doi.org/10.1139/e87-041.
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Moraines of two different age groups have been identified fronting the present-day glaciers and snowfields in Glacier National Park, Montana. The subdued, vegetated moraines of the older group have been found at 25 sites, mainly in the central part of the Lewis Range. These older moraines are in places overlain by the Mazama ash. Although the exact age of the moraines has not been determined by radiocarbon dating, vegetative evidence and correlation with other pre-altithermal age moraines in the Rocky Mountains suggest that these older moraines date from 10 000 BP or earlier. Whether these moraines are the product of a separate advance after the end of the Wisconsin glaciation or are simply the product of the last advance or stillstand of Wisconsin glaciers before final deglaciation is not known.Moraines of the younger group, consisting of fresh bouldery rubble, are common throughout Glacier Park. Tree-ring analyses indicate that some of these younger moraines were deposited by advances that culminated during the mid-19th century. At that time there were more than 150 glaciers in Glacier Park. This episode of mid-19th century climatic cooling resulted in the most extensive glacial advance in this region since the end of the Wisconsin glaciation.Present-day glaciers have shrunk drastically from their mid-19th century positions; more than half the glaciers present during that time no longer exist. Much of this retreat occurred between 1920 and the mid-1940's, corresponding to a period of above-average summer temperatures and below-average annual precipitation in this region. Between 1966 and 1979, several of the larger glaciers in the Mount Jackson area of Glacier Park advanced as much as 100 m.
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Daruka, I., and P. D. Ditlevsen. "Changing climatic response: a conceptual model for glacial cycles and the Mid-Pleistocene Transition." Climate of the Past Discussions 10, no. 2 (March 13, 2014): 1101–27. http://dx.doi.org/10.5194/cpd-10-1101-2014.
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Abstract. Milankovitch's astronomical theory of glacial cycles, attributing ice age climate oscillations to orbital changes in Northern Northern-Hemisphere insolation, is challenged by the paleoclimatic record. The climatic response to the variations in insolation is far from trivial. In general the glacial cycles are highly asymmetric in time, with slow cooling from the interglacials to the glacials (inceptions) and very rapid warming from the glacials to the interglacials (terminations). We shall refer to this fast-slow dynamics as the "saw-tooth" shape of the paleoclimatic record. This is non-linearly related to the time-symmetric variations in the orbital forcing. However, the most pronounced challenge to the Milankovitch theory is the Mid-Pleistocene Transition (MPT) occurring about one million years ago. During that event, the prevailing 41 kyr glacial cycles, corresponding to the almost harmonic obliquity cycle were replaced by longer saw-tooth shaped cycles with a time scale around 100 kyr. The MPT must have been driven by internal changes in climate response, since it does not correspond to any apparent changes in the orbital forcing. In order to identify possible mechanisms causing the observed changes in glacial dynamics, it is relevant to study simplified models with the capability of generating temporal behavior similar to the observed records. We present a simple oscillator type model approach, with two variables, a temperature anomaly and an ice volume analogous, climatic memory term. The generalization of the ice albedo feedback is included in terms of an effective multiplicative coupling between this latter climatic memory term (representing the internal degrees of freedom) and the external drive. The simple model reproduces the temporal asymmetry of the late Pleistocene glacial cycles and suggests that the MPT can be explained as a regime shift, aided by climatic noise, from a period 1 frequency locking to the obliquity cycle to a period 2–3 frequency locking to the same obliquity cycle. The change in dynamics has been suggested to be a result of a slow gradual decrease in atmospheric greenhouse gas concentration. The presence of chaos in the (non-autonomous) glacial dynamics and a critical dependence on initial conditions raises fundamental questions about climate predictability.
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Di Nicola, Luigia, Stefan Strasky, Christian Schlüchter, Maria Cristina Salvatore, Naki Akçar, Peter W. Kubik, Marcus Christl, Haino Uwe Kasper, Rainer Wieler, and Carlo Baroni. "Multiple cosmogenic nuclides document complex Pleistocene exposure history of glacial drifts in Terra Nova Bay (northern Victoria Land, Antarctica)." Quaternary Research 71, no. 1 (January 2009): 83–92. http://dx.doi.org/10.1016/j.yqres.2008.07.004.
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AbstractGeomorphological and glacial geological surveys and multiple cosmogenic nuclide analyses (10Be, 26Al, and 21Ne) allowed us to reconstruct the chronology of variations prior to the last glacial maximum of the East Antarctic Ice Sheet (EAIS) and valley glaciers in the Terra Nova Bay region. Glacially scoured coastal piedmonts with round-topped mountains occur below the highest local erosional trimline. They represent relict landscape features eroded by extensive ice overriding the whole coastal area before at least 6 Ma (pre-dating the build-up of the Mt. Melbourne volcanic field). Since then, summit surfaces were continuously exposed and well preserved under polar condition with negligible erosion rates on the order of 17 cm/Ma. Complex older drifts rest on deglaciated areas above the younger late-Pleistocene glacial drift and below the previously overridden summits. The combination of stable and radionuclide isotopes documents complex exposure histories with substantial periods of burial combined with minimal erosion. The areas below rounded summits were repeatedly exposed and buried by ice from local and outlet glaciers. The exposure ages of the older drift(s) indicate multiple Pleistocene glacial cycles, which did not significantly modify the pre-existing landscape.
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Berends, Constantijn J., Bas de Boer, and Roderik S. W. van de Wal. "Reconstructing the evolution of ice sheets, sea level, and atmospheric CO<sub>2</sub> during the past 3.6 million years." Climate of the Past 17, no. 1 (February 1, 2021): 361–77. http://dx.doi.org/10.5194/cp-17-361-2021.
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Abstract. Understanding the evolution of, and the interactions between, ice sheets and the global climate over geological timescales is important for being able to project their future evolution. However, direct observational evidence of past CO2 concentrations, and the implied radiative forcing, only exists for the past 800 000 years. Records of benthic δ18O date back millions of years but contain signals from both land ice volume and ocean temperature. In recent years, inverse forward modelling has been developed as a method to disentangle these two signals, resulting in mutually consistent reconstructions of ice volume, temperature, and CO2. We use this approach to force a hybrid ice-sheet–climate model with a benthic δ18O stack, reconstructing the evolution of the ice sheets, global mean sea level, and atmospheric CO2 during the late Pliocene and the Pleistocene, from 3.6 million years (Myr) ago to the present day. During the warmer-than-present climates of the late Pliocene, reconstructed CO2 varies widely, from 320–440 ppmv for warm periods to 235–250 ppmv for the early glacial excursion ∼3.3 million years ago. Sea level is relatively stable during this period, with maxima of 6–14 m and minima of 12–26 m during glacial episodes. Both CO2 and sea level are within the wide ranges of values covered by available proxy data for this period. Our results for the Pleistocene agree well with the ice-core CO2 record, as well as with different available sea-level proxy data. For the Early Pleistocene, 2.6–1.2 Myr ago, we simulate 40 kyr glacial cycles, with interglacial CO2 decreasing from 280–300 ppmv at the beginning of the Pleistocene to 250–280 ppmv just before the Mid-Pleistocene Transition (MPT). Peak glacial CO2 decreases from 220–250 to 205–225 ppmv during this period. After the MPT, when the glacial cycles change from 40 to 80 120 kyr cyclicity, the glacial–interglacial contrast increases, with interglacial CO2 varying between 250–320 ppmv and peak glacial values decreasing to 170–210 ppmv.
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Bezusko, L., S. Mosyakin, and A. Bezusko. "Paleoclimatic reconstruction for the late pleistocene period of the plain part of Ukraine." Visnyk of the Lviv University. Series Geography, no. 38 (December 15, 2010): 3–11. http://dx.doi.org/10.30970/vgg.2010.38.2205.
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The article summarizes the results of quantitative paleoclimatic reconstructions conducted using different methods based on the palinological records of the Upper Pleistocene deposits of the plain part of Ukraine. Quantitative climatic characteristics for the Riss-Wurm interglacial period, Dubno interstadial and the Last Glacial Maximum are provided. It is concluded that primary refugia of thermophilic and hydrophilic trees on the plain areas did not exist during the Last Glacial Maximum. Key words: paleoclimatic reconstructions, Late Pleistocene, Riss-Wurm interglacial period, Dubno interstadial.
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Murray, Donald R. "Late Pleistocene Glacier Dynamics and Paleoclimate Of South-Western Montana and North-Eastern Idaho. U.S.A." Annals of Glaciology 14 (1990): 350. http://dx.doi.org/10.1017/s0260305500009216.
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Reliable reconstructions of paleoglaciers using topographic maps and aerial photographs allow calculation of effective basal shear stresses along the longitudinal profiles of these glaciers. Glacial flow theory applied to these shear stresses provides an estimate of the component of mass flux due to internal deformation. Assuming basal slip to be zero at the point where deformation mass flux is a maximum, minimum average accumulation gradients (above the equilibrium-line altitude (ELA)) and ablation gradients (below the ELA) can be calculated and minimum mass flux at the ELA can be estimated using the continuity equation. Average net winter accumulation can also be calculated by dividing the mass flux at the ELA by the accumulation area. Because local climate controls the mass balance of a glacier, and therefore the accumulation and ablation gradients, this model provides information on the climatic setting of these paleoglaciers. This model also allows estimation of basal slip as a factor in point estimates of glacial flow. Application of the continuity model above and below the ELA generates additional estimates of mass flux at discrete points along the glacier. The difference between deformation mass flux and continuity flux at these points yields a first approximation of basal slip, which is highly variable along the glacier. The model was tested on the Big Timber glacier of west-central Montana and applied to several other late Pleistocene glaciers in the northern Rocky Mountains of south-western Montana and north-eastern Idaho. Low ablation gradients (<4.0 mm m-1) suggest a climate during the late Pleistocene comparable to the present-day climate of the Brooks Range in Alaska. Calculated average net winter accumulation for the area is well below modern values, again indicating that the climate was much drier during the full glacial period. Basal sliding accounts for most (>90%) of the glacial flow near the terminus of each glacier but is variable along the rest of the glacier. While the mass-balance values are minima, they are assumed to be reasonable approximations of the actual values unless very high basal slip rates occurred along the entire length of each glacier.
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Keller, O., and E. Krayss. "Die hochwürmzeitlichen Rückzugsphasen des Rhein-Vorlandgletschers und der erste alpine Eisrandkomplex im Spätglazial." Geographica Helvetica 42, no. 2 (June 30, 1987): 169–78. http://dx.doi.org/10.5194/gh-42-169-1987.
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Abstract. The Upper Pleistocene Wurm Glaciation Recessional Stades of the Alpine foreland glaciers of the Rhine area, and the first Alpine boundary complex of the Late Pleistocene. In the Rhine area of the Wurm glaciation, the recessional Stades can be morphologically subdivided by means of glacial boundary complexes. The Würm-Stem-on-the-Rhine complex is evidence for an upper Wurm readvance of the foreland glaciers after an intensive melting period (± 16 000 y BP?). The first Late Pleistocene readvance of the local northern Alpine glaciers appears as the Würm-Weissbad complex (± 14 000 y BP?), while in the main network of the glaciation no reaction is recognizable. In the Upper Pleistocene of the Wurm, the equilibrium line of the Rhine glacier was at an elevation of 1000 m. The first readvance of local glaciers in the Late Pleistocene took place at an elevation of about 1500 m.
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Agatova, Anna R., and Roman K. Nepop. "Pleistocene glaciations of the SE Altai, Russia, based on geomorphological data and absolute dating of glacial deposits in Chagan reference section." Geochronometria 44, no. 1 (March 30, 2017): 49–65. http://dx.doi.org/10.1515/geochr-2015-0059.
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AbstractGeomorphological evidence of at least two Pleistocene glacial epochsis noted within the Chagan-Uzun river basin, SE Altai. A review and analysis of all available absolute dates for reference Chagan section is presented. The highest correlation amongst all TL dates is observed for the lens of glacio-lacustrine sediments – the most suitable among glacial deposits for luminescence dating, and indicates its possible Middle Pleistocene age. IRSL dates obtained from feldspar indicate a Middle Pleistocene age of moraines already in the upper part of the section. The small number of obtained IRSL dates does not allow making geochronological reconstructions of the Pleistocene glaciations, but gives the possibility for further experiments with different variation of OSL (IRSL) techniques. Strong low temperature peak in TL signal and strong response to IR stimulation are specific regional quartz features, which could be explained by combination of short transportation distance and low number of depositional cycles for mineral grains. Available radiocarbon dates of carbonate concretions from this section are not related to the age of moraine sedimentation and most likely indicate the period of the Chagan river incision into the ancient glacial deposits.This study has shown that TL method is not valid for dating glacial sediments and TL dates cannot be utilized as chronostratigraphic markers. Generally, the Chagan section could hardly serve as a reference section for the Altai stratigraphy; available depositional correlation schemes for the Russian Altai and Siberia which are based on several TL dates obtained in the last century needs to be improved.
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Murray, Donald R. "Late Pleistocene Glacier Dynamics and Paleoclimate Of South-Western Montana and North-Eastern Idaho. U.S.A." Annals of Glaciology 14 (1990): 350. http://dx.doi.org/10.3189/s0260305500009216.
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Reliable reconstructions of paleoglaciers using topographic maps and aerial photographs allow calculation of effective basal shear stresses along the longitudinal profiles of these glaciers. Glacial flow theory applied to these shear stresses provides an estimate of the component of mass flux due to internal deformation. Assuming basal slip to be zero at the point where deformation mass flux is a maximum, minimum average accumulation gradients (above the equilibrium-line altitude (ELA)) and ablation gradients (below the ELA) can be calculated and minimum mass flux at the ELA can be estimated using the continuity equation. Average net winter accumulation can also be calculated by dividing the mass flux at the ELA by the accumulation area. Because local climate controls the mass balance of a glacier, and therefore the accumulation and ablation gradients, this model provides information on the climatic setting of these paleoglaciers.This model also allows estimation of basal slip as a factor in point estimates of glacial flow. Application of the continuity model above and below the ELA generates additional estimates of mass flux at discrete points along the glacier. The difference between deformation mass flux and continuity flux at these points yields a first approximation of basal slip, which is highly variable along the glacier.The model was tested on the Big Timber glacier of west-central Montana and applied to several other late Pleistocene glaciers in the northern Rocky Mountains of south-western Montana and north-eastern Idaho. Low ablation gradients (<4.0 mm m-1) suggest a climate during the late Pleistocene comparable to the present-day climate of the Brooks Range in Alaska. Calculated average net winter accumulation for the area is well below modern values, again indicating that the climate was much drier during the full glacial period. Basal sliding accounts for most (>90%) of the glacial flow near the terminus of each glacier but is variable along the rest of the glacier. While the mass-balance values are minima, they are assumed to be reasonable approximations of the actual values unless very high basal slip rates occurred along the entire length of each glacier.
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Giraudi, Carlo, and Massimo Frezzotti. "Late Pleistocene Glacial Events in the Central Apennines, Italy." Quaternary Research 48, no. 3 (November 1997): 280–90. http://dx.doi.org/10.1006/qres.1997.1928.
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The study of glacial evidence in the Gran Sasso Massif of the Central Apennines, Italy, has allowed the last maximum advance and the subsequent stadial phases to be dated and the mean annual temperature and quantity of precipitation in the form of snow to be assessed for a number of periods. The glaciers probably reached their maximum extension (Campo Imperatore Stade) ca. 22,600 14C yr B.P. and started to retreat ca. 21,000 yr B.P., leaving behind three recessional moraines. After a first interstade (Fornaca Interstade), the Fontari Stade appears to have taken place shortly after 16,000 yr ago. Ca. 15,000 yr ago the glacier started retreating, leaving behind four more recessional moraines. An interstade (Venacquaro Interstade) preceded the Mount Aquila Stade, datable at ca. 11,000 yr B.P. A strong correlation is evident between the glacial phases on land and the isotopic variations in cores from the Tyrrhenian Sea.
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Vázquez, Osvaldo Jiménez, Marjorie M. Condis, and Elvis García Cancio. "Vertebrados post-glaciales en un residuario fósil de Tyto alba scopoli (Aves: Tytonidae) en el occidente de." Revista Mexicana de Mastozoología (Nueva Epoca) 9, no. 1 (January 1, 2005): 85. http://dx.doi.org/10.22201/ie.20074484e.2005.9.1.168.
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Resumen: Se estudió un depósito fosilífero cavernario localizado en el occidente de Cuba y constituido por regurgitaciones de estrígidas. Este depósito fue el resultado de la actividad trófica de la lechuza (Tyto alba), la cual depredó anfibios, reptiles, aves y mamíferos, y fue fechado entre el Holoceno Temprano a Medio (C 14 -7 864 ± 96 años AP). Este estudio mostró una panorámica de la fauna antigua procedente de paisajes terrestres con bosques húmedos en sabanas, con posterioridad a la culminación de la última fase árida del Pleistoceno-Holoceno. Palabras clave: Paleontología; Tafonomía, Tyto alba, Regurgitaciones, Pleistoceno-Holoceno, Cuba. Abstract: A cave fossiliferous deposit formed for barn owl pellets in western part of Cuba are studied. This were results barn owl (Tyto alba) predation on amphibians, reptiles, birds and mammals and are dated in Early-Middle Holocene (C 14 -7 864 ± 96 years BP). These studies show an ancient faunal picture from terrestrial landscapes with moist forest in savannas after last Pleistocene-Holocene arid period. Key words: Paleontology, Tafonomy, Tyto alba, ,Regurgitations, Pleistocene-Holocene.
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Vázquez, Osvaldo Jiménez, Marjorie M. Condis, and Elvis García Cancio. "Vertebrados post-glaciales en un residuario fósil de Tyto alba scopoli (Aves: Tytonidae) en el occidente de." Revista Mexicana de Mastozoología (Nueva Epoca) 9, no. 1 (January 1, 2005): 85. http://dx.doi.org/10.22201/ie.20074484e.2005.9.1.169.
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Resumen: Se estudió un depósito fosilífero cavernario localizado en el occidente de Cuba y constituido por regurgitaciones de estrígidas. Este depósito fue el resultado de la actividad trófica de la lechuza (Tyto alba), la cual depredó anfibios, reptiles, aves y mamíferos, y fue fechado entre el Holoceno Temprano a Medio (C 14 -7 864 ± 96 años AP). Este estudio mostró una panorámica de la fauna antigua procedente de paisajes terrestres con bosques húmedos en sabanas, con posterioridad a la culminación de la última fase árida del Pleistoceno-Holoceno. Palabras clave: Paleontología; Tafonomía, Tyto alba, Regurgitaciones, Pleistoceno-Holoceno, Cuba. Abstract: A cave fossiliferous deposit formed for barn owl pellets in western part of Cuba are studied. This were results barn owl (Tyto alba) predation on amphibians, reptiles, birds and mammals and are dated in Early-Middle Holocene (C 14 -7 864 ± 96 years BP). These studies show an ancient faunal picture from terrestrial landscapes with moist forest in savannas after last Pleistocene-Holocene arid period. Key words: Paleontology, Tafonomy, Tyto alba, ,Regurgitations, Pleistocene-Holocene.
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Barrows, Timothy T., John O. Stone, L. Keith Fifield, and Richard G. Cresswell. "Late Pleistocene Glaciation of the Kosciuszko Massif, Snowy Mountains, Australia." Quaternary Research 55, no. 2 (March 2001): 179–89. http://dx.doi.org/10.1006/qres.2001.2216.
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AbstractLate Pleistocene glaciation of the Australian mainland was restricted to a small area of the southeastern highlands. Geomorphic mapping of the area and exposure dating using thein situproduced cosmogenic isotope10Be provides evidence for at least two distinct glaciations. The Early Kosciuszko glaciation consisted of a single glacier advance before 59,300 ± 5400 years ago (Snowy River Advance). The Late Kosciuszko glaciation comprised three glacier advances 32,000 ± 2500 (Headley Tarn Advance), 19,100 ± 1600 (Blue Lake Advance), and 16,800 ± 1400 years ago (Mt. Twynam Advance). The Early Kosciuszko glaciation was the most extensive and the Late Kosciuszko advances were progressively less extensive. These periods of glaciation in the highlands correspond to episodes of periglacial activity and peaks in lake levels and river discharge at lower elevations in southeastern Australia. Glacier advances on the Kosciuszko Massif correlate with advances in Tasmania, South America, and New Zealand and are broadly representative of hemispheric climate changes during the last glacial cycle.
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Rainsley, Eleanor, Chris S. M. Turney, Nicholas R. Golledge, Janet M. Wilmshurst, Matt S. McGlone, Alan G. Hogg, Bo Li, et al. "Pleistocene glacial history of the New Zealand subantarctic islands." Climate of the Past 15, no. 2 (March 14, 2019): 423–48. http://dx.doi.org/10.5194/cp-15-423-2019.
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Abstract. The New Zealand subantarctic islands of Auckland and Campbell, situated between the subtropical front and the Antarctic Convergence in the Pacific sector of the Southern Ocean, provide valuable terrestrial records from a globally important climatic region. Whilst the islands show clear evidence of past glaciation, the timing and mechanisms behind Pleistocene environmental and climate changes remain uncertain. Here we present a multidisciplinary study of the islands – including marine and terrestrial geomorphological surveys, extensive analyses of sedimentary sequences, a comprehensive dating programme, and glacier flow line modelling – to investigate multiple phases of glaciation across the islands. We find evidence that the Auckland Islands hosted a small ice cap 384 000 ± 26 000 years ago (384±26 ka), most likely during Marine Isotope Stage 10, a period when the subtropical front was reportedly north of its present-day latitude by several degrees, and consistent with hemispheric-wide glacial expansion. Flow line modelling constrained by field evidence suggests a more restricted glacial period prior to the LGM that formed substantial valley glaciers on the Campbell and Auckland Islands around 72–62 ka. Despite previous interpretations that suggest the maximum glacial extent occurred in the form of valley glaciation at the Last Glacial Maximum (LGM; ∼21 ka), our combined approach suggests minimal LGM glaciation across the New Zealand subantarctic islands and that no glaciers were present during the Antarctic Cold Reversal (ACR; ∼15–13 ka). Instead, modelling implies that despite a regional mean annual air temperature depression of ∼5 ∘C during the LGM, a combination of high seasonality and low precipitation left the islands incapable of sustaining significant glaciation. We suggest that northwards expansion of winter sea ice during the LGM and subsequent ACR led to precipitation starvation across the middle to high latitudes of the Southern Ocean, resulting in restricted glaciation of the subantarctic islands.
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Huybers, P. "Pleistocene glacial variability as a chaotic response to obliquity forcing." Climate of the Past Discussions 5, no. 1 (January 21, 2009): 237–50. http://dx.doi.org/10.5194/cpd-5-237-2009.
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Abstract. The mid-Pleistocene transition from 40 ky to ~100 ky glacial cycles is generally characterized as a singular transition attributable to scouring of continental regolith or a long-term decrease in atmospheric CO2 concentrations. Here an alternative hypothesis is suggested, that Pleistocene glacial variability is chaotic and that transitions from 40 ky to ~100 ky modes of variability occur spontaneously. This alternate view is consistent with the presence of ~80 ky glacial cycles during the early Pleistocene and the lack of evidence for a change in climate forcing during the mid-Pleistocene. A simple model illustrates this chaotic scenario. When forced at a 40 ky period the model chaotically transition between small 40 ky glacial cycles and larger 80 and 120 ky cycles which, on average, give the ~100 ky variability.
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Huybers, P. "Pleistocene glacial variability as a chaotic response to obliquity forcing." Climate of the Past 5, no. 3 (September 3, 2009): 481–88. http://dx.doi.org/10.5194/cp-5-481-2009.
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Abstract. The mid-Pleistocene Transition from 40 ky to ~100 ky glacial cycles is generally characterized as a singular transition attributable to scouring of continental regolith or a long-term decrease in atmospheric CO2 concentrations. Here an alternative hypothesis is suggested, that Pleistocene glacial variability is chaotic and that transitions from 40 ky to ~100 ky modes of variability occur spontaneously. This alternate view is consistent with the presence of ~80 ky glacial cycles during the early Pleistocene and the lack of evidence for a change in climate forcing during the mid-Pleistocene. A simple model illustrates this chaotic scenario. When forced at a 40 ky period the model chaotically transitions between small 40 ky glacial cycles and larger 80 and 120 ky cycles which, on average, give the ~100 ky variability.
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Orvis, Kenneth H., and Sally P. Horn. "Quaternary Glaciers and Climate on Cerro Chirripó, Costa Rica." Quaternary Research 54, no. 1 (July 2000): 24–37. http://dx.doi.org/10.1006/qres.2000.2142.
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Glacial lake sediments and glacial geomorphology in Valle de las Morrenas, a glacial trough on the north face of Cerro Chirripó, Costa Rica, provide evidence on high-altitude Pleistocene conditions in Central America. The most recent glacier in the valley (Chirripó stage I) receded very rapidly near the end of the Younger Dryas chronozone. Radiocarbon dates on basal organic sediments from lakes beneath upper, middle, and lower limits of that glacier fall close together, and two-sigma calibrated ages overlap for the period 9700–9600 cal yr B.P. Earliest datable transition sediments from the central lake date to 12,360–11,230 cal yr B.P. Larger, older moraines, and associated trimlines, allowed reconstruction of three paleoglaciers (Chirripó stages II, III, and IV). Computer analysis of hypsometry using published tropical-glacier vertical mass balance profiles yields ELAs of 3506–3523, 3515–3537, and 3418–3509 m, respectively; Chirripó II ELA-estimate positions applied to Chirripó I yield an ELA of 3538–3546 m. We infer minimal temperature depressions of 7.4–8.0°C for the Chirripó I–IV stages. Modeling the behavior of modern tropical glaciers yields basinwide net accumulation estimates of 440–620, 550–830, and 960–1760 mm yr−1 for the Chirripó II, III, and IV stages.
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VERBRUGGEN, Cyriel. "Quaternary palaeobotanical evolution of Northern Belgium." Quaternary geology of Belgium: new perspectives 2, no. 1-2 (April 1, 2000): 99–110. http://dx.doi.org/10.20341/gb.2014.013.
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The palaeobotanical data set of northern Belgium has to be divided into two parts: a post-glacial part including the Lateglacial and the Holocene period, and a Pleistocene part including the entire period between the beginning of the Quaternary and the end of the Weichselian glacial. A continuous and sufficiently documented record is present for the post-glacial period. As a standarised summary has been published recently (Verbruggen et al., 1996), this period is not discussed systematically. This paper focusses on the Pleistocene part of the data. The main problem about this data is the fact that most of it is unpublished. By incorporating the unpublished data and confronting them with the present-day theories from the neighbouring countries, it became possible to present an overview of the Pleistocene palaeobotany of northern Belgium. Interesting new data are added for the Saalian-, Eemian- and Early-Weichselian period.
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Winter, J. W. "Responses of Non-volant Mammals to Late Quaternary Climatic Changes in the Wet Tropics Region of North-eastern Australia." Wildlife Research 24, no. 5 (1997): 493. http://dx.doi.org/10.1071/wr96035.
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It is generally recognised that the distribution of vertebrates in rainforest and wet sclerophyll forest of the Wet Tropics region of north-eastern Australia is profoundly influenced by the formation of two rainforest refugia at the height of Pleistocene glacial periods. Anomalies in the distribution of non-volant mammals indicate that other events may be equally important. In this paper, past geographical occurrence of non-volant mammals is examined by equating the mammals’ known temperature tolerance with palaeoclimatic temperature zones. It is hypothesised that dispersal and vicariant phases taking place since the most recent glacial period have had a profound influence on current patterns of distribution. A major dispersal phase of cool-adapted species occurred after the glacial period, and continuous populations were subsequently fragmented into upland isolates by expansion of warm rainforest during the late post-glacial period. These upland isolates remain substantially unchanged to the present day. Species shared either with New Guinea or south-eastern Australia arrived in the region during the most recent post-glacial period. Clarification of periods of vicariance and dispersal provides a conceptual framework for testing relative divergences of populations within and between regions.
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Winsor, Kelsey, Kate M. Swanger, Esther Babcock, Rachel D. Valletta, and James L. Dickson. "Rock glacier characteristics serve as an indirect record of multiple alpine glacier advances in Taylor Valley, Antarctica." Cryosphere 14, no. 1 (January 2, 2020): 1–16. http://dx.doi.org/10.5194/tc-14-1-2020.
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Abstract. The geomorphic record indicates that alpine glaciers in the McMurdo Dry Valleys of southern Victoria Land, Antarctica, appear to advance during interglacial periods in response to ice-free conditions in the Ross Sea. Few records of these advances are preserved and/or subaerially exposed, complicating the interpretations of regional glacier response to climate changes. Here, we present geophysical and geochemical analyses of a rock glacier that originates from icefalls fed by alpine Doran Glacier in central Taylor Valley. The rock glacier exhibits a trend of increased weathering of granitic clasts via ventifaction and grussification down-flow. Meltwater ponds on the rock glacier exhibit variable salinity that ranges from freshwater to higher than seawater, with the highest salinity pond near the rock glacier toe. Ground-penetrating radar analyses reveal the feature to possess a primarily clean ice interior, with layers of englacial debris. Stable isotopic data from three ice cores support a glacial origin for the ice within the rock glacier. These data suggest that the current morphology of the rock glacier is the result of multiple events of increased ice contribution caused by advances of Doran Glacier, which is the main source of ice to the rock glacier. We therefore demonstrate the potential of ice-cored rock glaciers to record multiple advances and retreats of Dry Valley glaciers, permitting the interpretation of glacial responses to Pleistocene and Holocene climate change even where direct records are not present.
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Salomonsen, Inger. "Origin of a deep buried valley system in Pleistocene deposits of the eastern central North Sea." Danmarks Geologiske Undersøgelse Serie C 12 (December 31, 1995): 7–19. http://dx.doi.org/10.34194/seriec.v12.7106.
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In the North Sea, the sedimentary development of the late Tertiary and early Quaternary was dominated by deltaic sedimentation in a fast subsiding basin. During the Pleistocene, pronounced climatic changes affected the sedimentation of the area and progradation of the delta systems ceased. The Middle and Upper Pleistocene sedimentary successions consist of alternations of marine and fluvial deposits, partly reworked during glacial periods. Seismic records from the Danish sector of the North Sea reveal numerous deep incisions cut down from various levels of the Middle and Upper Pleistocene successions. These incisions are concluded to form a pattern of buried valleys. Detailed seismic stratigraphic analysis shows the occurrence of various internal unconformities within these buried valleys. It is concluded that the valleys originate from a river system developed in periods of repeated sea-level changes. Pluvial erosion during glacial sea-level lowstand and glacial meltwater action is proposed to have been responsible for the origin of the valley system. Thus, in Middle and Upper Pleistocene glacial periods drainage and associated sediment transport occurred from Northwest and Central European land areas via a presently buried river system in the southeastern North Sea towards a depositional basin north and northwest of the Danish North Sea sector.
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Ivashchenko, N. N., V. M. Kotlyakov, D. M. Sonechkin, and N. V. Vakulenko. "On Bifurcations Inducing Glacial Cycle Lengthening During Pliocene/Pleistocene Epoch." International Journal of Bifurcation and Chaos 24, no. 08 (August 2014): 1440018. http://dx.doi.org/10.1142/s0218127414400185.
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In the Pliocene (about two–five million years ago) global climate fluctuated with a period corresponding well to the 41-thousand-year cycle of changes in the Earth's axis obliquity. Then, this period disappeared, despite the fact that the obliquity cycle even slightly increased its swing and, therefore, the climatic response to this external climate forcing would have only strengthened. By analyzing paleoclimatic records covering the whole Pliocene and Pleistocene epoch, we show that the climatic response to the obliquity cycle simply became unstable, and therefore unobservable. At the same time, through the period-doubling bifurcation, which is well-known in dynamical system theory, new stable, and so observable, climatic fluctuations have been excited with an approximately doubled period. Further, these fluctuations experienced several secondary bifurcations, and, as a result, their periods increased even more.
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MacGregor, Kelly R., Catherine A. Riihimaki, Amy Myrbo, Mark D. Shapley, and Krista Jankowski. "Geomorphic and climatic change over the past 12,900 yr at Swiftcurrent Lake, Glacier National Park, Montana, USA." Quaternary Research 75, no. 1 (January 2011): 80–90. http://dx.doi.org/10.1016/j.yqres.2010.08.005.
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AbstractGlaciated alpine landscapes are sensitive to changes in climate. Shifts in temperature and precipitation can cause significant changes to glacier size and terminus position, the production and delivery of organic mass, and in the hydrologic energy related to the transport of water and sediment through proglacial environments. A sediment core representing a 12,900-yr record collected from Swiftcurrent Lake, located on the eastern side of Glacier National Park, Montana, was analyzed to assess variability in Holocene and latest Pleistocene environment. The spectral signature of total organic carbon content (%TOC) since ~ 7.6 ka matches that of solar forcing over 70–500 yr timescales. Periodic inputs of dolomite to the lake reflect an increased footprint of Grinnell Glacier, and occur during periods when sediment sinks are reduced, glacial erosion is increased, and hydrologic energy is increased. Grain size, carbon/nitrogen (C/N) ratios, and %TOC broadly define the termination of the Younger Dryas chronozone at Swiftcurrent Lake, as well as major Holocene climate transitions. Variability in core parameters is linked to other records of temperature and aridity in the northern Rocky Mountains over the late Pleistocene and Holocene.
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Liu, Weiguo, Zhonghui Liu, Jimin Sun, Chunhui Song, Hong Chang, Huanye Wang, Zheng Wang, and Zhisheng An. "Onset of permanent Taklimakan Desert linked to the mid-Pleistocene transition." Geology 48, no. 8 (May 12, 2020): 782–86. http://dx.doi.org/10.1130/g47406.1.
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Abstract The initial occurrence of desert landscape or eolian sand dunes is thought to have occurred long before the Pleistocene, and desertification was subsequently enhanced under cold, dusty glacial conditions. However, when and how the desert landscape persisted during both glacial and interglacial periods, defined as “permanent” desert here, remain elusive. Here, we present carbonate carbon isotope and grain-size records from the Tarim Basin, western China, revealing a detailed desertification history for the Taklimakan Desert. Our records demonstrate that after desiccation of episodic lakes at ca. 4.9 Ma, alternations of eolian sand dunes and fluvial and playa-like conditions persisted for a long period until 0.7 Ma in the Tarim Basin. The onset of permanent desert landscape around 0.7–0.5 Ma occurred concurrently with the climatic reorganization across the mid-Pleistocene transition. The occurrence of mountain glaciers on the Tibetan Plateau and atmospheric circulation changes may have controlled the formation and extreme aridification of the permanent desert in inland Asia since the mid-Pleistocene transition.
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Nikitin, Dmitry S., Vitaly R. Akhmedzyanov, Dmitry Yu Demezhko, and Mikhail D. Khutorskoi. "The reconstruction of the paleotemperature of the Earth’s surface on Yuzhny Island (Novaya Zemlya archipelago) according to geothermal data." Georesursy 21, no. 3 (September 1, 2019): 136–40. http://dx.doi.org/10.18599/grs.2019.3.136-140.
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According to the complex geothermal investigation results (thermal conductivity, rocks thermal heterogeneity measurements as well geothermal gradient and heat flow calculation) on Yuzhny Island of Novaya Zemlya archipelago (Pavlovskoye lead-zinc field), the paleotemperature on the surface in the historical past are modeled. The results of the climatic history reconstruction in this region are discussed. An earlier heat flow estimate on on Yuzhny Island of Novaya Zemlya archipelago (46 mW/m2) could be underestimated if we assume the glacier absence during the “Pleistocene / Holocene warming”. In this case, the calculated heat flow will be 55 mW/m2. If during the “small glacial period” the glacier existence lasted for 20 thousand years, then the first heat flow estimate is more likely.
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Aciego, S. M., K. M. Cuffey, J. L. Kavanaugh, D. L. Morse, and J. P. Severinghaus. "Pleistocene ice and paleo-strain rates at Taylor Glacier, Antarctica." Quaternary Research 68, no. 3 (November 2007): 303–13. http://dx.doi.org/10.1016/j.yqres.2007.07.013.
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AbstractIce exposed in ablation zones of ice sheets can be a valuable source of samples for paleoclimate studies and information about long-term ice dynamics. We report a 28-km long stable isotope sampling transect along a flowline on lower Taylor Glacier, Antarctica, and show that ice from the last glacial period is exposed here over tens of kilometers. Gas isotope analyses on a small number of samples confirm our age hypothesis. These chronostratigraphic data contain information about past ice dynamics and in particular should be sensitive to the longitudinal strain rate on the north flank of Taylor Dome, averaged over millennia. The imprint of climatic changes on ice dynamics may be discernible in these data.
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Montalvo-Fernández, Grecia, Lorenzo Felipe Sánchez-Teyer, Germán Carnevali, Andrew P. Vovides, Ricardo Gaytán-Legaria, Matilde Margarita Ortíz -García, Jaime Alejandro Muñoz-López, and Jaime Martínez Castillo. "Impact of Late Pleistocene-Holocene climatic fluctuations on the phylogeographic structure and historical demographics of Zamia prasina (Cycadales: Zamiaceae)." Botanical Sciences 97, no. 4 (December 19, 2019): 588–608. http://dx.doi.org/10.17129/botsci.2195.
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Background: Glacial periods during the Pleistocene have been hypothesized to have greatly influenced geographical patterns of genetic structure and demography of many tropical species. The Glacial Refugium Hypothesis proposes that, during cold, dry glacial periods, populations of moisture-affinities tropical species were restricted to sheltered, humid areas and that, during warmer and more humid interglacial periods, these populations expanded. Some mountain regions in the tropics acted as refugia during the cold, dry periods of the Pleistocene for several temperate forest taxa, which recolonized the humid areas farther north during the interglacial periods.Questions: (1) Did Late Pleistocene-Holocene climate changes affect the historical demophraphy of Zamia prasina? (2) Does the historical distribution of Zamia prasina agree with the Glacial Refugium Hypothesis?Study species: Zamia prasina W.Bull. (Zamiaceae), the only cycad native to the Yucatan Peninsula Biotic Province (YPBP). Methods: Five individuals were collected in 23 populations and characterized using two DNA regions: plastid atpF-atpH, and nuclear ITS2. Genetic diversity, phylogeographic structure, historical demography, and potential distributions were assessed. Results: Our results showed moderately high genetic diversity and low, but significant, phylogeographic structure. Two genetic groups were identified, one in the eastern part of the Peninsula, the other in the western. The changes in historical demography suggest that Z. prasina experienced a population expansion following the warm conditions of the Holocene.Conclusions: The population dynamics of Zamia prasina are in accordance with the Glacial Refugium Hypothesis.
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Vakulenko, N. V., N. N. Ivashchenko, V. M. Kotlyakov, and D. M. Sonechkin. "On periods of multiplying bifurcation of early pleistocene glacial cycles." Doklady Earth Sciences 436, no. 2 (February 2011): 245–48. http://dx.doi.org/10.1134/s1028334x11020115.
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Blaise, Bertrand. "Clay-Mineral Assemblages from Late Quaternary Deposits on Vancouver Island, Southwestern British Columbia, Canada." Quaternary Research 31, no. 1 (January 1989): 41–56. http://dx.doi.org/10.1016/0033-5894(89)90084-7.
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AbstractOn Vancouver Island, the Dashwood Drift, Cowichan Head Formation, Quadra Sand, and Vashon Drift were deposited during late Pleistocene glacial and interstadial periods and show large variations in clay-mineral contents partly related to changing climatic conditions. Glacial deposits are characterized by iron-rich chlorite, illite (both well crystallized), and smectite with a morphology reflecting rapid derivation from volcanic rocks. The clay mineralogy of nonglacial deposits is more complex, and is marked by the presence of vermiculite, kaolinite, halloysite, and irregular mixed-layer minerals. Nonglacial clay minerals are poorly preserved and show a higher state of alteration due to pedogenesis. Large variations in nonglacial deposits compared to glacial deposits are also due to secondary factors such as selective sorting, soil and rock source variations, differences in sedimentary environment, and diagenesis. These secondary factors do not seem to obliterate significantly the climatic imprint on the clay minerals. These studies also permit the recognition of glacially reworked sediments, the determination of relationships between two units in the same section, and the establishment of the conditions of clay-mineral formation.
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Jiménez-Moreno, Gonzalo, Hülya Alçiçek, M. Cihat Alçiçek, Lars van den Hoek Ostende, and Frank P. Wesselingh. "Vegetation and climate changes during the late Pliocene and early Pleistocene in SW Anatolia, Turkey." Quaternary Research 84, no. 3 (November 2015): 448–56. http://dx.doi.org/10.1016/j.yqres.2015.09.005.
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Pollen analysis was done on lacustrine sedimentary sequences dated by micromammals as late Pliocene–early Pleistocene that outcrop in two Neogene graben basins from SW Turkey. This study shows vegetation changes from steppe-like to more forested environments, very similar to the cyclic oscillations related to late Pleistocene glacial–interglacial climate changes. Artemisia was abundant during cold–arid periods, indicating that this species was already widespread in this area during the latest Pliocene and the beginning of the Pleistocene. A review of pollen records from Anatolia agrees with this study, suggesting that the spreading of this arid species occurred during a major climatic change: the beginning of the first glaciations and probably a change in seasonality towards summer aridity. Artemisia temporarily disappeared from the region during warm–wet periods and thus we suggest that glacial–interglacial-type oscillations already occurred in the area during the late Pliocene–early Pleistocene.
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O'Regan, Matt, Jan Backman, Natalia Barrientos, Thomas M. Cronin, Laura Gemery, Nina Kirchner, Larry A. Mayer, et al. "The De Long Trough: a newly discovered glacial trough on the East Siberian continental margin." Climate of the Past 13, no. 9 (September 28, 2017): 1269–84. http://dx.doi.org/10.5194/cp-13-1269-2017.
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Abstract. Ice sheets extending over parts of the East Siberian continental shelf have been proposed for the last glacial period and during the larger Pleistocene glaciations. The sparse data available over this sector of the Arctic Ocean have left the timing, extent and even existence of these ice sheets largely unresolved. Here we present new geophysical mapping and sediment coring data from the East Siberian shelf and slope collected during the 2014 SWERUS-C3 expedition (SWERUS-C3: Swedish – Russian – US Arctic Ocean Investigation of Climate-Cryosphere-Carbon Interactions). The multibeam bathymetry and chirp sub-bottom profiles reveal a set of glacial landforms that include grounding zone formations along the outer continental shelf, seaward of which lies a > 65 m thick sequence of glacio-genic debris flows. The glacial landforms are interpreted to lie at the seaward end of a glacial trough – the first to be reported on the East Siberian margin, here referred to as the De Long Trough because of its location due north of the De Long Islands. Stratigraphy and dating of sediment cores show that a drape of acoustically laminated sediments covering the glacial deposits is older than ∼ 50 cal kyr BP. This provides direct evidence for extensive glacial activity on the Siberian shelf that predates the Last Glacial Maximum and most likely occurred during the Saalian (Marine Isotope Stage (MIS) 6).
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Lakeman, Thomas R., John J. Clague, and Brian Menounos. "Advance of alpine glaciers during final retreat of the Cordilleran ice sheet in the Finlay River area, northern British Columbia, Canada." Quaternary Research 69, no. 2 (March 2008): 188–200. http://dx.doi.org/10.1016/j.yqres.2008.01.002.
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Sharp-crested moraines, up to 120 m high and 9 km beyond Little Ice Age glacier limits, record a late Pleistocene advance of alpine glaciers in the Finlay River area in northern British Columbia. The moraines are regional in extent and record climatic deterioration near the end of the last glaciation. Several lateral moraines are crosscut by meltwater channels that record downwasting of trunk valley ice of the northern Cordilleran ice sheet. Other lateral moraines merge with ice-stagnation deposits in trunk valleys. These relationships confirm the interaction of advancing alpine glaciers with the regionally decaying Cordilleran ice sheet and verify a late-glacial age for the moraines. Sediment cores were collected from eight lakes dammed by the moraines. Two tephras occur in basal sediments of five lakes, demonstrating that the moraines are the same age. Plant macrofossils from sediment cores provide a minimum limiting age of 10,550–10,250 cal yr BP (9230±5014C yr BP) for abandonment of the moraines. The advance that left the moraines may date to the Younger Dryas period. The Finlay moraines demonstrate that the timing and style of regional deglaciation was important in determining the magnitude of late-glacial glacier advances.
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Lacey, J. H., M. J. Leng, A. Francke, H. J. Sloane, A. Milodowski, H. Vogel, H. Baumgarten, and B. Wagner. "Mediterranean climate since the Middle Pleistocene: a 640 ka stable isotope record from Lake Ohrid (Albania/Macedonia)." Biogeosciences Discussions 12, no. 16 (August 20, 2015): 13427–81. http://dx.doi.org/10.5194/bgd-12-13427-2015.
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Abstract. Lake Ohrid (Macedonia/Albania) is an ancient lake with a unique biodiversity and a site of global significance for investigating the influence of climate, geological and tectonic events on the generation of endemic populations. Here, we present oxygen (δ18O) and carbon (δ13C) isotope data on carbonate from the upper ca. 248 m of sediment cores recovered as part of the Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) project, covering the past 640 ka. Previous studies on short cores from the lake (up to 15 m, < 140 ka) have indicated the Total Inorganic Carbon (TIC) content of sediments to be highly sensitive to climate change over the last glacial–interglacial cycle, comprising abundant endogenic calcite through interglacials and being almost absent in glacials, apart from discrete bands of early diagenetic authigenic siderite. Isotope measurements on endogenic calcite (δ18Oc and δ13Cc) reveal variations both between and within interglacials that suggest the lake has been subject to hydroclimate fluctuations on orbital and millennial timescales. We also measured isotopes on authigenic siderite (δ18Os and δ13Cs) and, with the δ18OCc and δ18Os, reconstruct δ18O of lakewater (δ18Olw) through the 640 ka. Overall, glacials have lower δ18Olw when compared to interglacials, most likely due to cooler summer temperatures, a higher proportion of winter precipitation (snowfall), and a reduced inflow from adjacent Lake Prespa. The isotope stratigraphy suggests Lake Ohrid experienced a period of general stability through Marine Isotope Stage (MIS) 15 to MIS 13, highlighting MIS 14 as a particularly warm glacial, and was isotopically freshest during MIS 9. After MIS 9, the variability between glacial and interglacial δ18Olw is enhanced and the lake became increasingly evaporated through to present day with MIS 5 having the highest average δ18Olw. Our results provide new evidence for long-term climate change in the northern Mediterranean region, which will form the basis to better understand the influence of major environmental events on biological evolution within the lake.
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Spellman, Garth M., and John Klicka. "Testing hypotheses of Pleistocene population history using coalescent simulations: phylogeography of the pygmy nuthatch ( Sitta pygmaea )." Proceedings of the Royal Society B: Biological Sciences 273, no. 1605 (September 26, 2006): 3057–63. http://dx.doi.org/10.1098/rspb.2006.3682.
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In this paper, we use mitochondrial NADH dehydrogenase subunit 2 sequences to test Pleistocene refugial hypotheses for the pygmy nuthatch ( Sitta pygmaea ). Pygmy nuthatches are a common resident of long-needle pine forests in western North America and demonstrate a particular affinity with ponderosa pine ( Pinus ponderosa ). Palaeoecological and genetic data indicate that ponderosa pine was isolated in two Pleistocene refugia corresponding to areas in the southern Sierra Nevada in the west and southern Arizona and New Mexico in the east. We use coalescent simulations to test the hypothesis that pygmy nuthatches tracked the Pleistocene history of their preferred habitat and persisted in two refugia during the periods of glacial maxima. Coalescent simulation of population history does not support the hypothesis of two Pleistocene refugia for the pygmy nuthatch. Instead, our data are consistent with a single refuge model. Nucleotide diversity is greatest in the western populations of southern and coastal California. We suggest that the pygmy nuthatch expanded from a far western glacial refuge into its current distribution since the most recent glacial maximum.
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Cook, Benjamin D., Mark Adams, Peter B. Mather, and Jane M. Hughes. "Statistical phylogeographic tests of competing 'Lake Carpentaria hypotheses' in the mouth-brooding freshwater fish, Glossamia aprion (Apogonidae)." Marine and Freshwater Research 63, no. 5 (2012): 450. http://dx.doi.org/10.1071/mf11222.
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Glacial cycles during the Pleistocene reduced sea levels and created new land connections in northern Australia, where many currently isolated rivers also became connected via an extensive paleo-lake system, ‘Lake Carpentaria’. However, the most recent period during which populations of freshwater species were connected by gene flow across Lake Carpentaria is debated: various ‘Lake Carpentaria hypotheses’ have been proposed. Here, we used a statistical phylogeographic approach to assess the timing of past population connectivity across the Carpentaria region in the obligate freshwater fish, Glossamia aprion. Results for this species indicate that the most recent period of genetic exchange across the Carpentaria region coincided with the mid- to late Pleistocene, a result shown previously for other freshwater and diadromous species. Based on these findings and published studies for various freshwater, diadromous and marine species, we propose a set of ‘Lake Carpentaria’ hypotheses to explain past population connectivity in aquatic species: (1) strictly freshwater species had widespread gene flow in the mid- to late Pleistocene before the last glacial maximum; (2) marine species were subdivided into eastern and western populations by land during Pleistocene glacial phases; and (3) past connectivity in diadromous species reflects the relative strength of their marine affinity.
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Bursik, Marcus I., and Alan R. Gillespie. "Late Pleistocene Glaciation of Mono Basin, California." Quaternary Research 39, no. 1 (January 1993): 24–35. http://dx.doi.org/10.1006/qres.1993.1003.
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AbstractMoraines in the canyons of Mono Basin are separable into relative-age groups on the basis of clast-sound velocities in exposed boulders, moraine morphology, and weathering features on boulder surfaces. Tioga, Tenaya, Tahoe, and Mono Basin moraine deposits each have distinct weathering characteristics and therefore constitute different relative-age groups. The Tioga glacial episode at June Lake may postdate ∼25,200(?)-yr-old basaltic lavas, and the Tenaya episode may have occurred ∼30,700 yr ago. A comparison of the glacial and lacustrine records of Mono Basin over the past 40,000 yr, based on new interpretations of radiometric ages, is consistent with the hypothesis that maximum glacial and maximum pluvial periods were not necessarily synchronous.
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Tao, Ruisong, Chang Xu, Yunliang Wang, Xiaoyan Sun, Chunxiang Li, Junye Ma, Jiasheng Hao, and Qun Yang. "Spatiotemporal Differentiation of Alpine Butterfly Parnassius glacialis (Papilionidae: Parnassiinae) in China: Evidence from Mitochondrial DNA and Nuclear Single Nucleotide Polymorphisms." Genes 11, no. 2 (February 11, 2020): 188. http://dx.doi.org/10.3390/genes11020188.
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The Apollo butterfly, Parnassius glacialis, is one of the most charming members of its genus and includes two subspecies locally distributed in montane areas of south-central China and Japan. In this study, we investigated the genetic structure and demographic history of P. glacialis by analyzing partial sequences of four mitochondrial genes and nuclear single nucleotide polymorphisms (SNPs) via genotyping-by-sequencing (GBS) of samples from nearly the entire known distributional range in China. The mitochondrial DNA (mtDNA) data demonstrated that a total of 39 haplotypes were present, and the species was estimated to have diverged about 0.95 million years ago during the middle Pleistocene transition into two main clades that likely formed during the Kunlun-Huanghe tectonic movement. The two clades then dispersed independently in distinct geographic areas alongside the mountainous routes in central and southern China, most likely driven by the Pleistocene glacial-interglacial cycles. Nuclear SNP analysis was generally congruent with mtDNA results at the individual level. A minor incongruence of genetic structures that was detected between mtDNA and nuclear SNP data from the Laojunshan and Tiantangzhai populations was likely due to secondary contact and male-biased dispersal. Our work demonstrates that complicated dispersal-vicariance evolutionary processes likely led to the current geographic distribution of P. glacialis in China, particularly the uplift of the Qinghai-Tibet Plateau and related climatic oscillations during the Quaternary period.
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Lechler, Alex R., Katharine W. Huntington, Daniel O. Breecker, Mark R. Sweeney, and Andrew J. Schauer. "Loess–paleosol carbonate clumped isotope record of late Pleistocene–Holocene climate change in the Palouse region, Washington State, USA." Quaternary Research 90, no. 2 (July 5, 2018): 331–47. http://dx.doi.org/10.1017/qua.2018.47.
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AbstractThe Channeled Scabland–Palouse region of the Pacific Northwest (PNW) of the United States preserves geomorphic and pedosedimentary records that inform understanding of late Pleistocene–Holocene paleoclimate change in a region proximal to the last glacial period Cordilleran Ice Sheet. We present a clumped (Δ47) and conventional (δ18O, δ13C) isotopic study of Palouse loess–paleosol carbonates in combination with carbonate radiocarbon (14C) dating to provide new measures of regional late–last glacial (~31–20 cal ka BP) and Holocene soil conditions. Average clumped isotope temperatures (T(Δ47)) for last glacial Palouse loess–paleosol carbonates (9±4°C) are significantly lower than those for Holocene-aged carbonates (T(Δ47)=18±2°C) in study sections. Calculated soil water δ18OVSMOWvalues (−16±2‰) for last glacial carbonates are also offset relative to those for Holocene-aged samples (−11±1‰), whereas calculated soil CO2δ13CVPDBvalues are similar for the Holocene (−16.9±0.2‰) and late–last glacial (−16.7±1.1‰) periods. Together, these paleoclimate metrics indicate late–last glacial conditions of pedogenic carbonate formation in the C3grassland soils of the Palouse were measurably colder (9±5°C) than during the Holocene and potentially reflect a more arid last glacial paleoclimate across the Palouse, findings in agreement with previous proxy studies and climate model simulations for the region.
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Casazza, Lorraine R. "Pleistocene reefs of the Egyptian Red Sea: environmental change and community persistence." PeerJ 5 (June 28, 2017): e3504. http://dx.doi.org/10.7717/peerj.3504.
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The fossil record of Red Sea fringing reefs provides an opportunity to study the history of coral-reef survival and recovery in the context of extreme environmental change. The Middle Pleistocene, the Late Pleistocene, and modern reefs represent three periods of reef growth separated by glacial low stands during which conditions became difficult for symbiotic reef fauna. Coral diversity and paleoenvironments of eight Middle and Late Pleistocene fossil terraces are described and characterized here. Pleistocene reef zones closely resemble reef zones of the modern Red Sea. All but one species identified from Middle and Late Pleistocene outcrops are also found on modern Red Sea reefs despite the possible extinction of most coral over two-thirds of the Red Sea basin during glacial low stands. Refugia in the Gulf of Aqaba and southern Red Sea may have allowed for the persistence of coral communities across glaciation events. Stability of coral communities across these extreme climate events indicates that even small populations of survivors can repopulate large areas given appropriate water conditions and time.
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Preusser, Frank, Benjamin U. Müller, and Christian Schlüchter. "Luminescence Dating of Sediments from the Luthern Valley, Central Switzerland, and Implications for the Chronology of the Last Glacial Cycle." Quaternary Research 55, no. 2 (March 2001): 215–22. http://dx.doi.org/10.1006/qres.2000.2208.
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AbstractThe advancing glaciers of the last glacial maximum either eroded or deeply buried older sediments in the Swiss Alpine Foreland. However, part of the Swiss Plateau was not covered by ice and is therefore an excellent area for investigating climate and environmental change during the Upper Pleistocene. Repeated fluvial sequences can be studied in several pits along the Luthern Valley. The chronological framework is based on lithostratigraphy, pollen analysis, U/Th dating, and recently, heavy mineral analysis and luminescence dating. The oldest unit, the Untere Zeller Schotter braided river deposit, represents cold climate conditions and presumably a glaciation prior to the Eemian Interglaciation. The last interglacial period and the very beginning of the last glacial cycle is represented by the Mittlere Zeller Schotter, sediments of a meandering fluvial system. Younger braided river sediments, the Obere Zeller Schotter, seem to correlate with the cold climate of oxygen isotope stage (OIS) 4. Weathering of the top of the Obere Zeller Schotter is likely to represent the OIS 3. The advancing Reuss glacier caused erosion of the recent Luthern Valley, cutting into older sediments, with local loess accumulation during the last glacial maximum as indicated by cover sediments on top of the fluvial sequence.