Quaternary Glaciations in the Río Mendoza Valley, Argentine Andes

1993 ◽  
Vol 40 (2) ◽  
pp. 150-162 ◽  
Author(s):  
Lydia E. Espizua
Keyword(s):  
Soil Profile ◽  
Fission Track ◽  
Rock Weathering ◽  
Relative Age ◽  
Glacier System ◽  
The Andes ◽  
Rock Varnish ◽  
The Last Glacial Maximum ◽  
Quaternary Glaciations ◽  
The Last Glacial

AbstractIn the Río Mendoza valley, five Pleistocene drifts and one Holocene drift are distinguished by multiple relative-age criteria, including surface-rock weathering, development of rock varnish, moraine morphology, soil-profile development, and stratigraphic relationships. Several absolute ages suggest a preliminary chronology. During the oldest (Uspallata) glaciation, a system of valley glaciers flowed 110 km from the Andean drainage divide and 80 km from Cerro Aconcagua to terminate at 1850 m. Drift of this ice advance is older than a widespread tephra dated by fission-track at 360,000 ± 36,000 yr. During the Punta de Vacas advance, ice terminated at 2350 m, while during the subsequent Penitentes advance, the glacier system ended at 2500 m. A travertine layer overlying Penitentes Drift has U-series age of 24,200 ± 2000 yr B.P. The distribution of Horcones Drift, which is inferred to represent the last glacial maximum, delimits an independent ice stream that flowed 22 km down Horcones valley to 2750 m. A later readvance (Almacenes) reached 3250 m. Confluencia Drift is considered to be Neoglacial in age and extends downvalley to 3300 m. The moraine sequence is compared with those studied by Caviedes (1972) along Río Aconcagua on the Chilean flank of the Andes.

scholarly journals Dynamics of mountain ice caps during glacial cycles: the case of Patagonia

1997 ◽  
Vol 24 ◽  
pp. 81-89 ◽  
Author(s):  
Nick Hulton ◽  
David Sugden
Keyword(s):  
Glacial Cycle ◽  
Glacial Cycles ◽  
Ice Caps ◽  
Ice Cap ◽  
The Andes ◽  
Cap Model ◽  
Present Distribution ◽  
The Last Glacial Maximum ◽  
Quaternary Glaciations ◽  
The Last Glacial

We use a time-dependent ice-cap model to predict the pattern of growth and decay of the Patagonian ice cap during a simulated glacial cycle. The purpose is to illuminate the internal system dynamics and identity thresholds of stability related to the underlying topography. This is a necessary step if former ice-cap behaviour is to be linked to climatic change. The model, which is fully described elsewhere, portrays ice extent and surface altitude at intervals of 1000–5000 years. The modelling suggests that there are two stable ice-cap states largely influenced by topography, namely, the present distribution of upland ice fields and the long, linear ice cap along the Andes as represented by the Last Glacial Maximum. Both states can coexist in equilibrium with a climate similar to that of the present day. There is a third, larger variable state in which a more extensive ice cap extends into the adjacent plains, as occurred during early Quaternary glaciations. Warmer and/or drier conditions are required to remove all these ice caps. There are five ice centres during ice-cap growth.

scholarly journals Dynamics of mountain ice caps during glacial cycles: the case of Patagonia

1997 ◽  
Vol 24 ◽  
pp. 81-89 ◽  
Author(s):  
Nick Hulton ◽  
David Sugden
Keyword(s):  
Glacial Cycle ◽  
Glacial Cycles ◽  
Ice Caps ◽  
Ice Cap ◽  
The Andes ◽  
Cap Model ◽  
Present Distribution ◽  
The Last Glacial Maximum ◽  
Quaternary Glaciations ◽  
The Last Glacial

We use a time-dependent ice-cap model to predict the pattern of growth and decay of the Patagonian ice cap during a simulated glacial cycle. The purpose is to illuminate the internal system dynamics and identity thresholds of stability related to the underlying topography. This is a necessary step if former ice-cap behaviour is to be linked to climatic change. The model, which is fully described elsewhere, portrays ice extent and surface altitude at intervals of 1000–5000 years. The modelling suggests that there are two stable ice-cap states largely influenced by topography, namely, the present distribution of upland ice fields and the long, linear ice cap along the Andes as represented by the Last Glacial Maximum. Both states can coexist in equilibrium with a climate similar to that of the present day. There is a third, larger variable state in which a more extensive ice cap extends into the adjacent plains, as occurred during early Quaternary glaciations. Warmer and/or drier conditions are required to remove all these ice caps. There are five ice centres during ice-cap growth.

Glacier Modeling and the Climate of Patagonia during the Last Glacial Maximum

1994 ◽  
Vol 42 (1) ◽  
pp. 1-19 ◽  
Author(s):  
Nick Hulton ◽  
David Sugden ◽  
Antony Payne ◽  
Chalmers Clapperton
Keyword(s):  
Mass Balance ◽  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Equilibrium Line Altitude ◽  
Last Glacial ◽  
Ice Cap ◽  
The Andes ◽  
The Antarctic ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractIce cap modeling constrained by empirical studies provides an effective way of reconstructing past climates. The former Patagonian ice sheet is in a climatically significant location since it lies athwart the Southern Hemisphere westerlies and responds to the latitudinal migration of climatic belts during glacial cycles. A numerical model of the Patagonian ice cap for the last glacial maximum (LGM) is developed, which is time-dependent and driven by changing the mass balance/altitude relationship. It relies on a vertically integrated continuity model of ice mass solved over a finite difference grid. The model is relatively insensitive to ice flow parameters but highly sensitive to mass balance. The climatic input is adjusted to produce the best fit with the known limits of the ice cap at the LGM. The ice cap extends 1800 km along the Andes and has a volume of 440,000 km3. During the LGM the equilibrium line altitude (ELA) was lower than at present by at least 560 m near latitude 40°S, 160 m near latitude 50°S, and 360 m near latitude 56°S. The latitudinal variation in ELA depression can be explained by an overall fall in temperature of about 3.0°C and the northward migration of precipitation belts by about 5° latitude. Annual precipitation totals may have decreased by about 0.7 m at latitude 50°S and increased by about 0.7 m at latitude 40°S. The ELA rises steeply by up to 4 m per kilometer from west to east as the westerlies cross the Andes and this prevents ice growth to the east. The limited decrease in temperature during the LGM could be related to the modest migration of the Antarctic convergence between South America and the Antarctic Peninsula.

Population genetic structure of long-tailed pygmy rice rats (Oligoryzomys longicaudatus) from Argentina and Chile based on the mitochondrial control region

2010 ◽  
Vol 88 (1) ◽  
pp. 23-35 ◽  
Author(s):  
Raúl E. González-Ittig ◽  
Hernán J. Rossi-Fraire ◽  
Gustavo E. Cantoni ◽  
Eduardo R. Herrero ◽  
Rosendo Benedetti ◽  
...  
Keyword(s):  
Gene Flow ◽  
Genetic Structure ◽  
Control Region ◽  
Phylogenetic Trees ◽  
Mitochondrial Control Region ◽  
The Andes ◽  
Single Clade ◽  
The Last Glacial Maximum ◽  
Oligoryzomys Longicaudatus ◽  
The Last Glacial

The rodent Oligoryzomys longicaudatus (Bennett, 1832) (Rodentia, Cricetidae) inhabits southern forests of Argentina and Chile, a region severely affected by glaciations during the Pleistocene–Holocene periods. We evaluate here the diversity of the mitochondrial control region to characterize the genetic structure of this species from forests and bushy areas of seven populations from Argentina and four populations from Chile. Statistical analyses showed shallow haplotype trees and mismatch distributions compatible with recent range expansions. The presence of “private” haplotypes indicates that current levels of gene flow among populations of each country would be low to moderate. Significant differences in haplotype frequencies were detected between eastern and western populations, indicating that the Andes mountains would be an effective geographic barrier for gene flow despite the existing valleys that could act as corridors for dispersion. A single clade containing all the haplotypes was recovered in the phylogenetic trees, suggesting postglacial dispersion from a single refugium during the Last Glacial Maximum. The higher effective size and levels of polymorphism in populations from Chile suggest that the refugium was located in this country. The asymmetric gene flow from Chile to Argentina may reflect a recent colonization of the eastern populations.

Subdivision of Late Pleistocene Moraines in the Cordillera Blanca, Peru, Based on Rock-Weathering Features, Soils, and Radiocarbon Dates

1993 ◽  
Vol 39 (2) ◽  
pp. 133-143 ◽  
Author(s):  
Donald T. Rodbell
Keyword(s):  
Late Pleistocene ◽  
Linear Models ◽  
Rock Weathering ◽  
Radiocarbon Dates ◽  
Cordillera Blanca ◽  
Progressive Development ◽  
Ca 50 ◽  
Northern Peru ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractThe progressive development of unusual rock-weathering features and soils and minimum-limiting radiocarbon dates provide a basis for subdividing four groups of late Pleistocene moraines on the west side of the Cordillera Blanca, northern Peru (9°20′1°000′S, 77°10′-77°30′W). Boulders on the youngest late Pleistocene moraines have 10 to 14-cm-tall weathering posts; soils on these moraines yield mean profile development index (PDI) values of 0.05 ± 0.04 (±1σ). These moraines date between ca. 13,500 and 9700 ± 500 yr B.P., older than previously postulated. The next older moraines have boulders with weathering-post heights between 20 and 25 cm and soils with PDI values of 0.08 ± 0.07, and were deposited prior to 13,280 ± 190 yr B.P., probably during the last glacial maximum (marine isotope stage 2). Moraines from an older glaciation have boulders with weathering posts between 39 and 50 cm high, soils that yield PDI values of 0.21 ± 0.07, and are older than 19,700 ± 340 yr B.P. Boulders on moraines from a still older glaciation have lost ca. 50% of their above-ground volume, and have weathering posts between 62 and 70 cm high. PDI values for soils on these moraines are 0.32 ± 0.06. Linear and logarithmic models of weathering-post and soil development with time are used to estimate minimum and maximum ages for the two oldest moraine groups. Linear models suggest that the second oldest moraines are between ca. 20,500 and 46,500 yr B.P., and that the oldest moraines are between ca. 29,000 and 72,000 yr B.P. In contrast, logarithmic models suggest ages of greater than ca. 75,500 yr B.P. and greater than ca. 500,000 yr B.P., respectively.

scholarly journals Formation and decay of peat bogs in the vegetable belt of Switzerland

2021 ◽  
Vol 114 (1) ◽  
Author(s):  
Markus Egli ◽  
Guido Wiesenberg ◽  
Jens Leifeld ◽  
Holger Gärtner ◽  
Jan Seibert ◽  
...  
Keyword(s):  
Agricultural Land ◽  
Arable Land ◽  
Late Glacial ◽  
Water Levels ◽  
Peat Bogs ◽  
Glacier System ◽  
The Alps ◽  
Swiss Jura ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractThe rapidly collapsing glacial systems of the Alps produced a large number of melt-water lakes and mires after the Last Glacial Maximum (LGM) in the Late Glacial period. The Rhone-Aare-glacier system gave rise to large moorlands and lakes in the region of the Three Lakes Region of Western Switzerland. When moorlands are formed, they are efficient sinks of atmospheric carbon, but when transformed to agricultural land they are significant C sources. In addition, mires can be used as archives for reconstructing landscape evolution. We explored in more detail the dynamics of the landscape of the Three Lakes Region with a particular focus on the formation and degradation of mires. The Bernese part of the Three Lakes Region developed to become—after the optimisation of the water-levels of the Swiss Jura—the vegetable belt of Switzerland. The situation for agriculture, however, has now become critical due to an overexploitation of the peatland. Until c. 13 ka BP the entire region was hydrologically connected. An additional lake existed at the western end of the plain receiving sediments from the Aare river. Around 13 ka BP, this lake was isolated from the Aare river and completely silted up until c. 10 ka BP when a mire started to form. In the valley floor (‘Grosses Moos’), the meandering Aare and the varying level of the nearby lake of Neuchâtel caused a spatio-temporally patchy formation of mires (start of formation: 10–3 ka BP). Strong morphodynamics having high erosion and sedimentation rates and a high variability of the chemical composition of the deposited material prevailed during the early Holocene until c. 7.5 ka BP. The situation remained relatively quiet between 5 and 2 ka BP. However, during the last 2000 years the hydrodynamic and geomorphic activities have increased again. The optimisation of the Swiss Jura water-levels during the nineteenth and twentieth centuries enabled the transformation of moorland into arable land. As a consequence, the moorland strongly degraded. Mean annual C-losses in agricultural land are c. 4.9 t ha−1 and c. 2.4 t ha−1 in forests. Because forests limit, but not stop, the degradation of mires, agroforestry might be tested and propagated in future as alternative land-use systems for such sensitive areas.

Rock weathering, soil development and colonization under a changing climate

1992 ◽  
Vol 338 (1285) ◽  
pp. 269-277 ◽  
Keyword(s):  
Organic Matter ◽  
Water Availability ◽  
Ice Sheets ◽  
Soil Development ◽  
The Arctic ◽  
Rock Weathering ◽  
Freeze Thaw ◽  
Precipitation Regimes ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Antarctic continental soils are arid, saline and lacking in organic matter, whereas maritime soils, in a wetter environment, range from structureless lithosols to frozen peat. Two important factors in the development and diversity of their associated terrestrial communities are water availability and the period of exposure since deglaciation. The retreat of ice sheets offers new sites for colonization by microbes, plants and animals. The interactions between snow lie, freeze-thaw cycles, wet-dry cycles and the length of the summer are considered as critical in determining the extent and rate of localized changes in weathering and pedogenesis. The implications of higher temperatures and differing precipitation regimes are considered in relation to weathering, soil development and the establishment and development of terrestrial communities. It is concluded that, in the context of decades, most changes will be slow and localized. They are unlikely to be of regional significance, unlike some of those in the Arctic. They will, however, provide a good model of how present soils and communities developed at the end of the last glacial maximum.

Sign in / Sign up

Export Citation Format

Share Document