- Email: [email protected]
Relationship between recent fluctuations of glacier snouts and outburst floods of glacier-dammed lakes in north western Karakoram Mountains, Pakistan
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Abstracts / Quaternary International 279-280 (2012) 462–565
Here, a 600-year record of dust ratio was reconstructed. It shows that dust events occurred frequently in two periods over the past 600 years, i.e., from the early 15th century to the middle 16th century, and from the late 18th century to the early 20th century. And the Malan ice core record indicates that dust event frequency displayed a clear decrease trend over the past 200 years. The decrease trend might be caused mostly by the natural processes, including increasing precipitation and weakening westerly which might be related with global warming. EVIDENCE OF YOUNGER DRYAS ARIDITY SUCCESSIONS IN THE MIDWEST OF U.S.A
IN
DUNE-PALEOSOL
Hong Wang. University of Illinois at Urbana-Champaign, United States E-mail address: [email protected]
Two dune-paleosol successions were found in the Illinois River Valley in U.S.A. The most significant observation is that a paleosol/gyttja complex separates two late-glacial dune sequences at both sites. The optically stimulated luminescence (OSL) dates indicate that upper dune sand is the Younger Dryas (YD) interval and 14C dates indicate that the gyttja and underlying paleosol is a Bølling/Allerød (B/A) equivalent unit. The paleosol reflects a warmer and more humid climatic condition and the gyttja accumulated in either a swamp or nearshore position of a lake, which fundamentally differs from dry climate associated late-glacial dune formation. Detailed 14C and OSL dating analyses were applied to both successions and reflectance (L*a*b*), magnetic susceptibility, total carbonate content, trace and rare earth element analyses were applied over 5-cm increments at one site. These results confirm that dry YD and wet B/A climates prevailed in the Illinois River Valley. We propose that during the Northern Hemisphere (NH) warming, the jet streams shifted northward, allowing warm/moist airmasses from the Gulf of Mexico persisted in the Midwest, which increased summer precipitation supporting a healthy habitat and stabilizing the landscape. During the NH cooling, the jet stream shifted southward forcing the dry airmasses from the Arctic and Northern Pacific into the Midwest, which ultimately reduced summer precipitation, destabilized the landscape, and caused the YD dune field to form. ROCK MAGNETIC INVESTIGATION OF LOESS DEPOSITS IN LUONAN BASIN (CENTRAL CHINA) AND ITS PALEOCLIMATIC IMPLICATIONS - A CASE STUDY Xiaoyong Wang. Nanjing University, China E-mail address: [email protected]
The Luonan Basin, located at the natural boundary of environment of China, is regarded as an important place for early human evolution during the early to middle Pleistocene. We carried out a combined mineral-magnetic and geochemical investigation on a loess deposits from Liuwan Paleolithic site in the Luonan basin. Results indicate a mixture of magnetic minerals, including magnetite/maghemite, hematite/goethite and iron sulfides, was present in the Liuwan loess deposits. Both loess and paleosol horizons of the lower part (6.5-11.8m) show lower and uniform values in magnetic susceptibility (c), susceptibility of Anhysteretic Remanent Magnetization (cARM),and Saturation Isothermal Remanent Magnetization(SIRM). Which may result from dissolution of magnetic minerals by paleogroundwater. Though magnetic parameters (c, cARM and SIRM) show higher values in paleosol horizons and lower values in loess horizons for the upper section (0-6.5m), field investigation and geochemical evidence suggest they can't reflect the strength of pedogenesis accurately. Magnetic parameters related to grain size of magnetic minerals such as SIRM/c and cARM /SIRM are found to be significantly correlated with the Chemical Index of Alteration (CIA) and field observation, which all show smaller amplitude than their counterpart in the Chinese Loess Plateau, suggesting Luonan area had experienced a relatively smaller variability of paleoclimates and pleoenvironments during the period when the upper part of the Liuwan loess were deposited. RELATIONSHIP BETWEEN RECENT FLUCTUATIONS OF GLACIER SNOUTS AND OUTBURST FLOODS OF GLACIER-DAMMED LAKES IN NORTH WESTERN KARAKORAM MOUNTAINS, PAKISTAN Tetsuya Waragai. Nihon University, Japan E-mail address: [email protected]
The relationship between the historical glacier fluctuation and the outburst flood of glacier-dammed lakes was analyzed at Hunza Valley in the Karakoram Mountains, Pakistan. As a result, glaciers such as Batura, Pasu, Ghulkin, Hasanabad, Minapin, Ghulmet and Biafo have repeated glacier progressions of about 10-20 years after long retreat periods (18601907, 1913-1960 and 1980-) since AD 1860. In addition, it is thought from the growing environment of Jeniperus distributing in the Valley that temperate periods (1865-1895, 1915-1950 and 1975-1995) appeared in the 20-25 year cycle repeatedly. A relationship between the glacier fluctuation and such climatic condition shows that the glaciers accompanied with a response time of 10-12 years have sensitively responded to climatic changes in the Valley. While, six periods of the outburst flood in Hunza and Shimshal valleys, which appeared in the about 20year cycle correspond to the retreat periods of the glaciers. It shows that the glacier retreat depending on climatic warming is the trigger of the outburst flood of glacier-dammed lakes, which is preceding the increasing of the melting ice and the expansion of lake area. COMPARISON OF MIS 4 AND 6 GLACIATIONS, YUKON TERRITORY, CANADA Brent Ward. Simon Fraser University, Canada E-mail address: [email protected]
Yukon Territory has been repeatedly affected by the northern Cordilleran Ice Sheet (CIS). This ice complex produced irregular, digitate, horseshoeshaped glacial limits on the plateau area of central Yukon. Many of these ice flows had separate source areas and dynamics but three broad mappable chrono-geomorphic regions have been defined that were thought to represent regionally coherent advances of the Cordilleran Ice Sheet. However, the mapped limit for the penultimate “Reid” glaciation actually represents two separate glaciations. In central Yukon, the assumed Marine Oxygen Isotope Stage (MIS) 6 age for the penultimate Reid Glaciation is confirmed by the presence of Old Crow tephra (124 ka) above deglacial Reid outwash along the Pelly River. There is no evidence for a MIS 4 glaciation that is more extensive than MIS 2 in central Yukon. In contrast, cosmogenic 10Be ages on boulders of 54-51 ka (n¼4) on penultimate drift in western Yukon Territory confirm that MIS 4 glaciation was extensive in parts of Yukon Territory. We name this glaciation the Gladstone, the first confirmed MIS 4 glaciation in the Canadian Cordillera. The situation is more complex to the west as sections exposed at the penultimate limit along White River in SW Yukon indicate that the MIS 4 Gladstone has an almost identical extent to an older, likely MIS 6 glaciation. Thus, there is a dichotomy between MIS 4 and 6 glacial extents for at least two of the source areas for the northern portion of the Cordilleran Ice Sheet, indicating different glaciological responses to climatic forcing during glaciations. The northern CIS was a precipitation-limited system and we propose that variation in regional precipitation, specifically how moisture penetrates the St. Elias and Coast mountains, is a possible cause of the differences between glacial advances. Causes for this regional variation in precipitation remain unclear. TEPHROSTRATIGRAPHY OF THE POTROK AIKE MAAR LAKE SEDIMENT SEQUENCE Stefan Wastegård. Stockholm University, Sweden E-mail address: [email protected]
There is increasing evidence that the Southern Ocean plays a key role for a better understanding of the global climate system. The southern hemisphere contains over 90% of the worlds ice and 81% of its total surface is covered by oceans. The most extreme oceanic character is between 40 and 60 S where only 2% of the earth's surface consists of land. One of very few permanent lakes between these latitudes is the 100 m deep Laguna Potrok Aike (52 58’S, 70 23’W) in southern Patagonia, Argentina, formed by a volcanic maar eruption several hundred thousand years ago. Seven holes were drilled in 2008 in the framework of the ICDP-funded PASADO project. The 106 m reference profile consists of laminated and sand-layered lacustrine silts with an increasing number of coarse gravel layers and turbidites with depth. In total, 24 visible tephra layers document the regional volcanic history and open the possibility to establish an independent age control supported by tephrochronology. The tephra horizons
Abstracts / Quaternary International 279-280 (2012) 462–565
Here, a 600-year record of dust ratio was reconstructed. It shows that dust events occurred frequently in two periods over the past 600 years, i.e., from the early 15th century to the middle 16th century, and from the late 18th century to the early 20th century. And the Malan ice core record indicates that dust event frequency displayed a clear decrease trend over the past 200 years. The decrease trend might be caused mostly by the natural processes, including increasing precipitation and weakening westerly which might be related with global warming. EVIDENCE OF YOUNGER DRYAS ARIDITY SUCCESSIONS IN THE MIDWEST OF U.S.A
IN
DUNE-PALEOSOL
Hong Wang. University of Illinois at Urbana-Champaign, United States E-mail address: [email protected]
Two dune-paleosol successions were found in the Illinois River Valley in U.S.A. The most significant observation is that a paleosol/gyttja complex separates two late-glacial dune sequences at both sites. The optically stimulated luminescence (OSL) dates indicate that upper dune sand is the Younger Dryas (YD) interval and 14C dates indicate that the gyttja and underlying paleosol is a Bølling/Allerød (B/A) equivalent unit. The paleosol reflects a warmer and more humid climatic condition and the gyttja accumulated in either a swamp or nearshore position of a lake, which fundamentally differs from dry climate associated late-glacial dune formation. Detailed 14C and OSL dating analyses were applied to both successions and reflectance (L*a*b*), magnetic susceptibility, total carbonate content, trace and rare earth element analyses were applied over 5-cm increments at one site. These results confirm that dry YD and wet B/A climates prevailed in the Illinois River Valley. We propose that during the Northern Hemisphere (NH) warming, the jet streams shifted northward, allowing warm/moist airmasses from the Gulf of Mexico persisted in the Midwest, which increased summer precipitation supporting a healthy habitat and stabilizing the landscape. During the NH cooling, the jet stream shifted southward forcing the dry airmasses from the Arctic and Northern Pacific into the Midwest, which ultimately reduced summer precipitation, destabilized the landscape, and caused the YD dune field to form. ROCK MAGNETIC INVESTIGATION OF LOESS DEPOSITS IN LUONAN BASIN (CENTRAL CHINA) AND ITS PALEOCLIMATIC IMPLICATIONS - A CASE STUDY Xiaoyong Wang. Nanjing University, China E-mail address: [email protected]
The Luonan Basin, located at the natural boundary of environment of China, is regarded as an important place for early human evolution during the early to middle Pleistocene. We carried out a combined mineral-magnetic and geochemical investigation on a loess deposits from Liuwan Paleolithic site in the Luonan basin. Results indicate a mixture of magnetic minerals, including magnetite/maghemite, hematite/goethite and iron sulfides, was present in the Liuwan loess deposits. Both loess and paleosol horizons of the lower part (6.5-11.8m) show lower and uniform values in magnetic susceptibility (c), susceptibility of Anhysteretic Remanent Magnetization (cARM),and Saturation Isothermal Remanent Magnetization(SIRM). Which may result from dissolution of magnetic minerals by paleogroundwater. Though magnetic parameters (c, cARM and SIRM) show higher values in paleosol horizons and lower values in loess horizons for the upper section (0-6.5m), field investigation and geochemical evidence suggest they can't reflect the strength of pedogenesis accurately. Magnetic parameters related to grain size of magnetic minerals such as SIRM/c and cARM /SIRM are found to be significantly correlated with the Chemical Index of Alteration (CIA) and field observation, which all show smaller amplitude than their counterpart in the Chinese Loess Plateau, suggesting Luonan area had experienced a relatively smaller variability of paleoclimates and pleoenvironments during the period when the upper part of the Liuwan loess were deposited. RELATIONSHIP BETWEEN RECENT FLUCTUATIONS OF GLACIER SNOUTS AND OUTBURST FLOODS OF GLACIER-DAMMED LAKES IN NORTH WESTERN KARAKORAM MOUNTAINS, PAKISTAN Tetsuya Waragai. Nihon University, Japan E-mail address: [email protected]
The relationship between the historical glacier fluctuation and the outburst flood of glacier-dammed lakes was analyzed at Hunza Valley in the Karakoram Mountains, Pakistan. As a result, glaciers such as Batura, Pasu, Ghulkin, Hasanabad, Minapin, Ghulmet and Biafo have repeated glacier progressions of about 10-20 years after long retreat periods (18601907, 1913-1960 and 1980-) since AD 1860. In addition, it is thought from the growing environment of Jeniperus distributing in the Valley that temperate periods (1865-1895, 1915-1950 and 1975-1995) appeared in the 20-25 year cycle repeatedly. A relationship between the glacier fluctuation and such climatic condition shows that the glaciers accompanied with a response time of 10-12 years have sensitively responded to climatic changes in the Valley. While, six periods of the outburst flood in Hunza and Shimshal valleys, which appeared in the about 20year cycle correspond to the retreat periods of the glaciers. It shows that the glacier retreat depending on climatic warming is the trigger of the outburst flood of glacier-dammed lakes, which is preceding the increasing of the melting ice and the expansion of lake area. COMPARISON OF MIS 4 AND 6 GLACIATIONS, YUKON TERRITORY, CANADA Brent Ward. Simon Fraser University, Canada E-mail address: [email protected]
Yukon Territory has been repeatedly affected by the northern Cordilleran Ice Sheet (CIS). This ice complex produced irregular, digitate, horseshoeshaped glacial limits on the plateau area of central Yukon. Many of these ice flows had separate source areas and dynamics but three broad mappable chrono-geomorphic regions have been defined that were thought to represent regionally coherent advances of the Cordilleran Ice Sheet. However, the mapped limit for the penultimate “Reid” glaciation actually represents two separate glaciations. In central Yukon, the assumed Marine Oxygen Isotope Stage (MIS) 6 age for the penultimate Reid Glaciation is confirmed by the presence of Old Crow tephra (124 ka) above deglacial Reid outwash along the Pelly River. There is no evidence for a MIS 4 glaciation that is more extensive than MIS 2 in central Yukon. In contrast, cosmogenic 10Be ages on boulders of 54-51 ka (n¼4) on penultimate drift in western Yukon Territory confirm that MIS 4 glaciation was extensive in parts of Yukon Territory. We name this glaciation the Gladstone, the first confirmed MIS 4 glaciation in the Canadian Cordillera. The situation is more complex to the west as sections exposed at the penultimate limit along White River in SW Yukon indicate that the MIS 4 Gladstone has an almost identical extent to an older, likely MIS 6 glaciation. Thus, there is a dichotomy between MIS 4 and 6 glacial extents for at least two of the source areas for the northern portion of the Cordilleran Ice Sheet, indicating different glaciological responses to climatic forcing during glaciations. The northern CIS was a precipitation-limited system and we propose that variation in regional precipitation, specifically how moisture penetrates the St. Elias and Coast mountains, is a possible cause of the differences between glacial advances. Causes for this regional variation in precipitation remain unclear. TEPHROSTRATIGRAPHY OF THE POTROK AIKE MAAR LAKE SEDIMENT SEQUENCE Stefan Wastegård. Stockholm University, Sweden E-mail address: [email protected]
There is increasing evidence that the Southern Ocean plays a key role for a better understanding of the global climate system. The southern hemisphere contains over 90% of the worlds ice and 81% of its total surface is covered by oceans. The most extreme oceanic character is between 40 and 60 S where only 2% of the earth's surface consists of land. One of very few permanent lakes between these latitudes is the 100 m deep Laguna Potrok Aike (52 58’S, 70 23’W) in southern Patagonia, Argentina, formed by a volcanic maar eruption several hundred thousand years ago. Seven holes were drilled in 2008 in the framework of the ICDP-funded PASADO project. The 106 m reference profile consists of laminated and sand-layered lacustrine silts with an increasing number of coarse gravel layers and turbidites with depth. In total, 24 visible tephra layers document the regional volcanic history and open the possibility to establish an independent age control supported by tephrochronology. The tephra horizons