Cosmogenic Radionuclide

14,000,000 Leading Edge Experts on the ideXlab platform

Scan Science and Technology

Contact Leading Edge Experts & Companies

Scan Science and Technology

Contact Leading Edge Experts & Companies

The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform

Robert C. Finkel - One of the best experts on this subject based on the ideXlab platform.

  • the pingding segment of the altyn tagh fault 91 e holocene slip rate determination from Cosmogenic Radionuclide dating of offset fluvial terraces
    Journal of Geophysical Research, 2012
    Co-Authors: Annesophie Meriaux, J Van Der Woerd, Cecile Lasserre, Robert C. Finkel, Frederick J. Ryerson, Paul Tapponnier, Xiwei Xu
    Abstract:

    Morphochronologic slip-rates on the Altyn Tagh Fault (ATF) along the southern front of the Pingding Shan at 90.5E are determined by Cosmogenic Radionuclide (CRN) dating of seven offset terraces at two sites. The terraces are defined based upon morphology, elevation and dating, together with fieldwork and high-resolution satellite analysis. The majority of the CRN model ages fall within narrow ranges (<2 ka) on the four main terraces (T1, T2, T3 and T3′), and allow a detailed terrace chronology. Bounds on the terrace ages and offsets of 5 independent terraces yield consistent slip-rate estimates. The long-term slip-rate of 13.9+/-1.1 mm/yr is defined at the 95% confidence level, as the joint rate probability distribution of the rate derived from each independent terrace. It falls within the bounds of all the rates defined on the central Altyn Tagh Fault between the Cherchen He (86.4E) and Akato Tagh (88E) sites. This rate is 10 mm/yr less than the upper rate determined near Tura at 87E, in keeping with the inference of an eastward decreasing rate due to progressive loss of slip to thrusts branching off the fault southwards but it is greater than the 9+/-4 mm/yr rate determined at 90E by GPS surveys and other geodetic short-term rates defined elsewhere along the ATF. Whether such disparate rates will ultimately be reconciled by a better understanding of fault mechanics, resolved transient deformations during the seismic cycle or by more accurate measurements made with either approach remains an important issue.

  • quaternary glaciation of the himalayan tibetan orogen
    Journal of Quaternary Science, 2008
    Co-Authors: Lewis A Owen, Marc W Caffee, Robert C. Finkel, Yeong Bae Seong
    Abstract:

    Glacial geological evidence from throughout the Himalayan–Tibetan orogen is examined to determine the timing and extent of late Quaternary glaciation in this region and its relation to similar changes on a global scale. The evidence summarised here supports the existence of expanded ice caps and extensive valley glacier systems throughout the region during the late Quaternary. However, it cannot yet be determined whether the timing of the extent of maximum glaciation was synchronous throughout the entire region or whether the response was more varied. The lack of organic material needed for radiocarbon dating has hindered past progress in glacial reconstruction; however, application of optically stimulated luminescence and terrestrial Cosmogenic Radionuclide methods has recently expanded the number of chronologies throughout the region. Limits to the precision and accuracy available with these methods and, more importantly, geological uncertainty imposed by processes of moraine formation and alteration both conspire to limit the time resolution on which correlations can be made to Milankovitch timescales (several ka). In order to put all studies on a common scale, well-dated sites have been re-evaluated and all the published terrestrial Cosmogenic nuclide ages for moraine boulders and glacially eroded surfaces in the Himalayan–Tibetan orogen have been recalculated. Locally detailed studies indicate that there are considerable variations in the extent of glaciation from one region to the next during a glaciation. Glaciers throughout monsoon-influenced Tibet, the Himalaya and the Transhimalaya are likely synchronous both with climate change resulting from oscillations in the South Asian monsoon and with Northern Hemisphere cooling cycles. In contrast, glaciers in Pamir in the far western regions of the Himalayan–Tibet orogen advanced asynchronously relative to the other regions that are monsoon-influenced regions and appear to be mainly in phase with the Northern Hemisphere cooling cycles. Broad patterns of local and regional variability based on equilibrium-line altitudes have yet to be fully assessed, but have the potential to help define changes in climatic gradients over time. Copyright © 2008 John Wiley & Sons, Ltd.

  • a lateglacial rock avalanche event tianchi lake tien shan xinjiang
    Quaternary International, 2006
    Co-Authors: Ling Zhu, Lewis A Owen, Yeong Bae Seong, Robert C. Finkel
    Abstract:

    Abstract The genesis of a diamicton deposit that dams Tianchi Lake in the eastern Tien Shan, Xinjiang, China, has been debated for many years, and it has generally been considered to have been either the result of landsliding or glacial deposition. Using geomorphic, sedimentological and geochronological techniques we re-examined this deposit to help elucidate its origin. The outer margin of the deposit can be traced up the adjacent hillside, where a series of steps within the bedrock are present and likely represent landslide scars. Within the lake the deposit has an undulating surface. The deposit is unstratified, comprising angular monomictic clasts that coarsen upward into boulders, which armor the surface. All these features suggest that the deposit was formed by landsliding. Furthermore, 10Be Cosmogenic Radionuclide surface exposure dating of boulders on the levee of the deposit show that the deposit probably formed during the Lateglacial, possibly at ∼12 ka and is likely coincident to the Younger Dryas Stade. The sedimentological and geomorphic evidence support our view that the diamicton deposit is not of glacial origin, but was deposited by rock avalanching during the Lateglacial.

  • late quaternary landscape evolution in the kunlun mountains and qaidam basin northern tibet a framework for examining the links between glaciation lake level changes and alluvial fan formation
    Quaternary International, 2006
    Co-Authors: Lewis A Owen, Robert C. Finkel, Ma Haizhou, Patrick L Barnard
    Abstract:

    Abstract The Qaidam Basin in Northern Tibet is one of the largest hyper-arid intermontane basins on Earth. Alluvial fans, pediment surfaces, shorelines and a thick succession of sediments within the basin, coupled with moraines and associated landforms in the adjacent high mountain catchments of the Kunlun Mountains, record a complex history of Late Quaternary paleoenvironmental change and landscape evolution. The region provides an ideal natural laboratory to examine the interaction between tectonics and climate within a continent–continent collision zone, and to quantify rates of landscape evolution as controlled by climate and the associated glacial and hydrological changes in hyper-arid and adjacent high-altitude environments. Geomorphic mapping, analysis of landforms and sediments, and terrestrial Cosmogenic Radionuclide surface exposure and optically stimulated luminescence dating serve to define the timing of formation of Late Quaternary landforms along the southern and northwestern margins of the Qaidam Basin, and in the Burhan Budai Shan of the Kunlun Mountains adjacent to the basin on the south. These dates provide a framework that suggests links between climatic amelioration, deglaciation, lake desiccation and alluvial fan evolution. At least three glacial advances are defined in the Burham Budai Shan of the Kunlun Mountains. On the northern side of this range these occurred in the penultimate glacial cycle or early in the last glacial cycle, during the Last Glacial Maximum (LGM)/Lateglacial and during the Holocene. On the south side of the range, advances occurred during the penultimate glacial cycle, MIS-3, and possibly the LGM, Lateglacial or Holocene. Several distinct phases of alluvial fan sedimentation are likewise defined. Alluvial fans formed on the southern side of the Kunlun Mountains prior to 200 ka. Ice-contact alluvial fans formed during the penultimate glacial and during MIS-3. Extensive incised alluvial fans that form the main valley fills north of the Burham Budai and extend into the Qaidam Basin are dated to ∼30 ka. These ages suggest that there was a period of alluvial fan aggradation and valley filling that persisted until desiccation of the large lakes in the Qaidam Basin post ∼30 ka led to base level lowering and active incision of streams into the valley fills. The continued Lateglacial and Holocene desiccation likely led to further degradation of the valley fills. Ice wedge casts in the Qaidam Basin date to ∼15 ka, indicating significant Lateglacial climatic amelioration, while Holocene loess deposits north of the Burham Bdudai suggest that aridity has increased in the region since the early Holocene. From these observations, we infer that the major landscape changes within high glaciated mountains and their adjacent hyper-arid intermontane basins, such as the Kunlun Mountains and Qaidam Basin, occur rapidly over millennial timescales during periods of climatic instability.

  • landscape response to deglaciation in a high relief monsoon influenced alpine environment langtang himal nepal
    Quaternary Science Reviews, 2006
    Co-Authors: Patrick L Barnard, Robert C. Finkel, Lewis A Owen, Katsuhiko Asahi
    Abstract:

    Abstract Significant glacial fluctuations and rapid paraglacial reworking of glacigenic sediments characterize the Middle and Late Holocene of the Langtang Khola Valley, Central Nepal Himalaya. Geomorphic mapping and beryllium-10 Cosmogenic Radionuclide (CRN) dating of moraines and paraglacial fans were undertaken to test the existing paraglacial fan, terrace and moraine chronologies. The new dating compares favorably with prior studies that utilized radiocarbon, adding additional support to the assumption that fan and terrace formation are strongly linked to deglaciation. Fan and terrace denudation rates are so rapid in this region, averaging ∼33 mm/yr, that no depositional landforms older than 5 ka are preserved within 250 m of the valley floor. In this region, high rates of denudation during the Late Quaternary are driven by a combination of rapid tectonic uplift, numerous glacial fluctuations and intense weathering driven by an active monsoon climate. Extensive reworking of glacigenic sediments in Langtang during the latter half of the Holocene is consistent with studies completed in other areas of the Himalaya that are strongly influenced by the monsoon.

Lewis A Owen - One of the best experts on this subject based on the ideXlab platform.

  • quaternary glaciation of the himalayan tibetan orogen
    Journal of Quaternary Science, 2008
    Co-Authors: Lewis A Owen, Marc W Caffee, Robert C. Finkel, Yeong Bae Seong
    Abstract:

    Glacial geological evidence from throughout the Himalayan–Tibetan orogen is examined to determine the timing and extent of late Quaternary glaciation in this region and its relation to similar changes on a global scale. The evidence summarised here supports the existence of expanded ice caps and extensive valley glacier systems throughout the region during the late Quaternary. However, it cannot yet be determined whether the timing of the extent of maximum glaciation was synchronous throughout the entire region or whether the response was more varied. The lack of organic material needed for radiocarbon dating has hindered past progress in glacial reconstruction; however, application of optically stimulated luminescence and terrestrial Cosmogenic Radionuclide methods has recently expanded the number of chronologies throughout the region. Limits to the precision and accuracy available with these methods and, more importantly, geological uncertainty imposed by processes of moraine formation and alteration both conspire to limit the time resolution on which correlations can be made to Milankovitch timescales (several ka). In order to put all studies on a common scale, well-dated sites have been re-evaluated and all the published terrestrial Cosmogenic nuclide ages for moraine boulders and glacially eroded surfaces in the Himalayan–Tibetan orogen have been recalculated. Locally detailed studies indicate that there are considerable variations in the extent of glaciation from one region to the next during a glaciation. Glaciers throughout monsoon-influenced Tibet, the Himalaya and the Transhimalaya are likely synchronous both with climate change resulting from oscillations in the South Asian monsoon and with Northern Hemisphere cooling cycles. In contrast, glaciers in Pamir in the far western regions of the Himalayan–Tibet orogen advanced asynchronously relative to the other regions that are monsoon-influenced regions and appear to be mainly in phase with the Northern Hemisphere cooling cycles. Broad patterns of local and regional variability based on equilibrium-line altitudes have yet to be fully assessed, but have the potential to help define changes in climatic gradients over time. Copyright © 2008 John Wiley & Sons, Ltd.

  • a lateglacial rock avalanche event tianchi lake tien shan xinjiang
    Quaternary International, 2006
    Co-Authors: Ling Zhu, Lewis A Owen, Yeong Bae Seong, Robert C. Finkel
    Abstract:

    Abstract The genesis of a diamicton deposit that dams Tianchi Lake in the eastern Tien Shan, Xinjiang, China, has been debated for many years, and it has generally been considered to have been either the result of landsliding or glacial deposition. Using geomorphic, sedimentological and geochronological techniques we re-examined this deposit to help elucidate its origin. The outer margin of the deposit can be traced up the adjacent hillside, where a series of steps within the bedrock are present and likely represent landslide scars. Within the lake the deposit has an undulating surface. The deposit is unstratified, comprising angular monomictic clasts that coarsen upward into boulders, which armor the surface. All these features suggest that the deposit was formed by landsliding. Furthermore, 10Be Cosmogenic Radionuclide surface exposure dating of boulders on the levee of the deposit show that the deposit probably formed during the Lateglacial, possibly at ∼12 ka and is likely coincident to the Younger Dryas Stade. The sedimentological and geomorphic evidence support our view that the diamicton deposit is not of glacial origin, but was deposited by rock avalanching during the Lateglacial.

  • late quaternary landscape evolution in the kunlun mountains and qaidam basin northern tibet a framework for examining the links between glaciation lake level changes and alluvial fan formation
    Quaternary International, 2006
    Co-Authors: Lewis A Owen, Robert C. Finkel, Ma Haizhou, Patrick L Barnard
    Abstract:

    Abstract The Qaidam Basin in Northern Tibet is one of the largest hyper-arid intermontane basins on Earth. Alluvial fans, pediment surfaces, shorelines and a thick succession of sediments within the basin, coupled with moraines and associated landforms in the adjacent high mountain catchments of the Kunlun Mountains, record a complex history of Late Quaternary paleoenvironmental change and landscape evolution. The region provides an ideal natural laboratory to examine the interaction between tectonics and climate within a continent–continent collision zone, and to quantify rates of landscape evolution as controlled by climate and the associated glacial and hydrological changes in hyper-arid and adjacent high-altitude environments. Geomorphic mapping, analysis of landforms and sediments, and terrestrial Cosmogenic Radionuclide surface exposure and optically stimulated luminescence dating serve to define the timing of formation of Late Quaternary landforms along the southern and northwestern margins of the Qaidam Basin, and in the Burhan Budai Shan of the Kunlun Mountains adjacent to the basin on the south. These dates provide a framework that suggests links between climatic amelioration, deglaciation, lake desiccation and alluvial fan evolution. At least three glacial advances are defined in the Burham Budai Shan of the Kunlun Mountains. On the northern side of this range these occurred in the penultimate glacial cycle or early in the last glacial cycle, during the Last Glacial Maximum (LGM)/Lateglacial and during the Holocene. On the south side of the range, advances occurred during the penultimate glacial cycle, MIS-3, and possibly the LGM, Lateglacial or Holocene. Several distinct phases of alluvial fan sedimentation are likewise defined. Alluvial fans formed on the southern side of the Kunlun Mountains prior to 200 ka. Ice-contact alluvial fans formed during the penultimate glacial and during MIS-3. Extensive incised alluvial fans that form the main valley fills north of the Burham Budai and extend into the Qaidam Basin are dated to ∼30 ka. These ages suggest that there was a period of alluvial fan aggradation and valley filling that persisted until desiccation of the large lakes in the Qaidam Basin post ∼30 ka led to base level lowering and active incision of streams into the valley fills. The continued Lateglacial and Holocene desiccation likely led to further degradation of the valley fills. Ice wedge casts in the Qaidam Basin date to ∼15 ka, indicating significant Lateglacial climatic amelioration, while Holocene loess deposits north of the Burham Bdudai suggest that aridity has increased in the region since the early Holocene. From these observations, we infer that the major landscape changes within high glaciated mountains and their adjacent hyper-arid intermontane basins, such as the Kunlun Mountains and Qaidam Basin, occur rapidly over millennial timescales during periods of climatic instability.

  • landscape response to deglaciation in a high relief monsoon influenced alpine environment langtang himal nepal
    Quaternary Science Reviews, 2006
    Co-Authors: Patrick L Barnard, Robert C. Finkel, Lewis A Owen, Katsuhiko Asahi
    Abstract:

    Abstract Significant glacial fluctuations and rapid paraglacial reworking of glacigenic sediments characterize the Middle and Late Holocene of the Langtang Khola Valley, Central Nepal Himalaya. Geomorphic mapping and beryllium-10 Cosmogenic Radionuclide (CRN) dating of moraines and paraglacial fans were undertaken to test the existing paraglacial fan, terrace and moraine chronologies. The new dating compares favorably with prior studies that utilized radiocarbon, adding additional support to the assumption that fan and terrace formation are strongly linked to deglaciation. Fan and terrace denudation rates are so rapid in this region, averaging ∼33 mm/yr, that no depositional landforms older than 5 ka are preserved within 250 m of the valley floor. In this region, high rates of denudation during the Late Quaternary are driven by a combination of rapid tectonic uplift, numerous glacial fluctuations and intense weathering driven by an active monsoon climate. Extensive reworking of glacigenic sediments in Langtang during the latter half of the Holocene is consistent with studies completed in other areas of the Himalaya that are strongly influenced by the monsoon.

  • climatic and topographic controls on the style and timing of late quaternary glaciation throughout tibet and the himalaya defined by 10be Cosmogenic Radionuclide surface exposure dating
    Quaternary Science Reviews, 2005
    Co-Authors: Lewis A Owen, Marc W Caffee, Robert C. Finkel, Patrick L Barnard, Ma Haizhou, Katsuhiko Asahi, Edward Derbyshire
    Abstract:

    Abstract Temporal and spatial changes in glacier cover throughout the Late Quaternary in Tibet and the bordering mountains are poorly defined because of the inaccessibility and vastness of the region, and the lack of numerical dating. To help reconstruct the timing and extent of glaciation throughout Tibet and the bordering mountains, we use geomorphic mapping and 10 Be Cosmogenic Radionuclide (CRN) surface dating in study areas in southeastern (Gonga Shan), southern (Karola Pass) and central (Western Nyainqentanggulha Shan and Tanggula Shan) Tibet, and we compare these with recently determined numerical chronologies in other parts of the plateau and its borderlands. Each of the study regions receives its precipitation mainly during the south Asian summer monsoon when it falls as snow at high altitudes. Gonga Shan receives the most precipitation (>2000 mm a −1 ) while, near the margins of monsoon influence, the Karola Pass receives moderate amounts of precipitation (500–600 mm a −1 ) and, in the interior of the plateau, little precipitation falls on the western Nyainqentanggulha Shan (∼300 mm a −1 ) and the Tanggula Shan (400–700 mm a −1 ). The higher precipitation values for the Tanggula Shan are due to strong orographic effects. In each region, at least three sets of moraines and associated landforms are preserved, providing evidence for multiple glaciations. The 10 Be CRN surface exposure dating shows that the formation of moraines in Gonga Shan occurred during the early–mid Holocene, Neoglacial and Little Ice Age, on the Karola Pass during the Lateglacial, Early Holocene and Neoglacial, in the Nyainqentanggulha Shan date during the early part of the last glacial cycle, global Last Glacial Maximum and Lateglacial, and on the Tanggula Shan during the penultimate glacial cycle and the early part of the last glacial cycle. The oldest moraine succession in each of these regions varies from the early Holocene (Gonga Shan), Lateglacial (Karola Pass), early Last Glacial (western Nyainqentanggulha Shan), and penultimate glacial cycle (Tanggula Shan). We believe that the regional patterns and timing of glaciation reflect temporal and spatial variability in the south Asian monsoon and, in particular, in regional precipitation gradients. In zones of greater aridity, the extent of glaciation has become increasingly restricted throughout the Late Quaternary leading to the preservation of old (≫100 ka) glacial landforms. In contrast, in regions that are very strongly influenced by the monsoon (≫1600 mm a −1 ), the preservation potential of pre-Lateglacial moraine successions is generally extremely poor. This is possibly because Lateglacial and Holocene glacial advances may have been more extensive than early glaciations and hence may have destroyed any landform or sedimentary evidence of earlier glaciations. Furthermore, the intense denudation, mainly by fluvial and mass movement processes, which characterize these wetter environments, results in rapid erosion and re-sedimentation of glacial and associated landforms, which also contributes to their poor preservation potential.

Marc W Caffee - One of the best experts on this subject based on the ideXlab platform.

  • annama h chondrite mineralogy physical properties cosmic ray exposure and parent body history
    Meteoritics & Planetary Science, 2017
    Co-Authors: Tomas Kohout, Marc W Caffee, Kees C. Welten, M Laubenstein, Jakub Haloda, Patricie Halodova, M M M Meier, Colin Maden, H Busemann, Jens Hopp
    Abstract:

    The fall of the Annama meteorite occurred early morning (local time) on April 19, 2014 on the Kola Peninsula (Russia). Based on mineralogy and physical properties, Annama is a typical H chondrite. It has a high Ar-Ar age of 4.4 Ga. Its cosmic ray exposure history is atypical as it is not part of the large group of H chondrites with a prominent 7–8 Ma peak in the exposure age histograms. Instead, its exposure age is within uncertainty of a smaller peak at 30 ± 4 Ma. The results from short-lived Radionuclides are compatible with an atmospheric pre-entry radius of 30–40 cm. However, based on noble gas and Cosmogenic Radionuclide data, Annama must have been part of a larger body (radius >65 cm) for a large part of its cosmic ray exposure history. The 10Be concentration indicates a recent (3–5 Ma) breakup which may be responsible for the Annama parent body size reduction to 30–35 cm pre-entry radius.

  • A noble gas and Cosmogenic Radionuclide analysis of two ordinary chondrites from Almahata Sitta
    Meteoritics & Planetary Science, 2012
    Co-Authors: Matthias M. M. Meier, Marc W Caffee, Kunihiko Nishiizumi, Kees C. Welten, Jon M. Friedrich, Peter Jenniskens, Muawia H. Shaddad, Rainer Wieler
    Abstract:

    We present the results of a noble gas (He, Ne, Ar) and Cosmogenic Radionuclide (10Be, 26Al, 36Cl) analysis of two chondritic fragments (#A100, L4 and #25, H5) found in the Almahata Sitta strewn field in Sudan. We confirm their earlier attribution to the same fall as the ureilites dominating the strewn field, based on the following findings: (1) both chondrite samples indicate a preatmospheric radius of approximately 300 g cm-2, consistent with the preatmospheric size of asteroid 2008 TC3 that produced the Almahata Sitta strewn field; (2) both have, within error, a 21Ne/26Al-based cosmic ray exposure age of approximately 20 Ma, identical to the reported ages of Almahata Sitta ureilites; (3) both exhibit hints of ureilitic Ar in the trapped component. We discuss a possible earlier irradiation phase for the two fragments of approximately 1020 Ma, visible only in Cosmogenic 38Ar. We also discuss the approximately 3.8 Ga (4He) and approximately 4.6 Ga (40Ar) gas retention ages, measured in both chondritic fragments. These imply that the two chondrite fragments were incorporated into the ureilite host early in solar system evolution, and that the parent asteroid from which 2008 TC3 is derived has not experienced a large break-up event in the last 3.8 Ga. (Less)

  • quaternary glaciation of the himalayan tibetan orogen
    Journal of Quaternary Science, 2008
    Co-Authors: Lewis A Owen, Marc W Caffee, Robert C. Finkel, Yeong Bae Seong
    Abstract:

    Glacial geological evidence from throughout the Himalayan–Tibetan orogen is examined to determine the timing and extent of late Quaternary glaciation in this region and its relation to similar changes on a global scale. The evidence summarised here supports the existence of expanded ice caps and extensive valley glacier systems throughout the region during the late Quaternary. However, it cannot yet be determined whether the timing of the extent of maximum glaciation was synchronous throughout the entire region or whether the response was more varied. The lack of organic material needed for radiocarbon dating has hindered past progress in glacial reconstruction; however, application of optically stimulated luminescence and terrestrial Cosmogenic Radionuclide methods has recently expanded the number of chronologies throughout the region. Limits to the precision and accuracy available with these methods and, more importantly, geological uncertainty imposed by processes of moraine formation and alteration both conspire to limit the time resolution on which correlations can be made to Milankovitch timescales (several ka). In order to put all studies on a common scale, well-dated sites have been re-evaluated and all the published terrestrial Cosmogenic nuclide ages for moraine boulders and glacially eroded surfaces in the Himalayan–Tibetan orogen have been recalculated. Locally detailed studies indicate that there are considerable variations in the extent of glaciation from one region to the next during a glaciation. Glaciers throughout monsoon-influenced Tibet, the Himalaya and the Transhimalaya are likely synchronous both with climate change resulting from oscillations in the South Asian monsoon and with Northern Hemisphere cooling cycles. In contrast, glaciers in Pamir in the far western regions of the Himalayan–Tibet orogen advanced asynchronously relative to the other regions that are monsoon-influenced regions and appear to be mainly in phase with the Northern Hemisphere cooling cycles. Broad patterns of local and regional variability based on equilibrium-line altitudes have yet to be fully assessed, but have the potential to help define changes in climatic gradients over time. Copyright © 2008 John Wiley & Sons, Ltd.

  • Cosmogenic Radionuclide and fine matrix analyses of blockfields northern sweden indications for quaternary origins
    2008
    Co-Authors: Bradley W Goodfellow, Marc W Caffee, Arjen P Stroeven, Derek Fabel, Ola Fredin, M H Derron, Richard Bintanja, Stewart Freeman
    Abstract:

    Cosmogenic Radionuclide and fine matrix analyses of blockfields, northern Sweden: Indications for Quaternary origins

  • climatic and topographic controls on the style and timing of late quaternary glaciation throughout tibet and the himalaya defined by 10be Cosmogenic Radionuclide surface exposure dating
    Quaternary Science Reviews, 2005
    Co-Authors: Lewis A Owen, Marc W Caffee, Robert C. Finkel, Patrick L Barnard, Ma Haizhou, Katsuhiko Asahi, Edward Derbyshire
    Abstract:

    Abstract Temporal and spatial changes in glacier cover throughout the Late Quaternary in Tibet and the bordering mountains are poorly defined because of the inaccessibility and vastness of the region, and the lack of numerical dating. To help reconstruct the timing and extent of glaciation throughout Tibet and the bordering mountains, we use geomorphic mapping and 10 Be Cosmogenic Radionuclide (CRN) surface dating in study areas in southeastern (Gonga Shan), southern (Karola Pass) and central (Western Nyainqentanggulha Shan and Tanggula Shan) Tibet, and we compare these with recently determined numerical chronologies in other parts of the plateau and its borderlands. Each of the study regions receives its precipitation mainly during the south Asian summer monsoon when it falls as snow at high altitudes. Gonga Shan receives the most precipitation (>2000 mm a −1 ) while, near the margins of monsoon influence, the Karola Pass receives moderate amounts of precipitation (500–600 mm a −1 ) and, in the interior of the plateau, little precipitation falls on the western Nyainqentanggulha Shan (∼300 mm a −1 ) and the Tanggula Shan (400–700 mm a −1 ). The higher precipitation values for the Tanggula Shan are due to strong orographic effects. In each region, at least three sets of moraines and associated landforms are preserved, providing evidence for multiple glaciations. The 10 Be CRN surface exposure dating shows that the formation of moraines in Gonga Shan occurred during the early–mid Holocene, Neoglacial and Little Ice Age, on the Karola Pass during the Lateglacial, Early Holocene and Neoglacial, in the Nyainqentanggulha Shan date during the early part of the last glacial cycle, global Last Glacial Maximum and Lateglacial, and on the Tanggula Shan during the penultimate glacial cycle and the early part of the last glacial cycle. The oldest moraine succession in each of these regions varies from the early Holocene (Gonga Shan), Lateglacial (Karola Pass), early Last Glacial (western Nyainqentanggulha Shan), and penultimate glacial cycle (Tanggula Shan). We believe that the regional patterns and timing of glaciation reflect temporal and spatial variability in the south Asian monsoon and, in particular, in regional precipitation gradients. In zones of greater aridity, the extent of glaciation has become increasingly restricted throughout the Late Quaternary leading to the preservation of old (≫100 ka) glacial landforms. In contrast, in regions that are very strongly influenced by the monsoon (≫1600 mm a −1 ), the preservation potential of pre-Lateglacial moraine successions is generally extremely poor. This is possibly because Lateglacial and Holocene glacial advances may have been more extensive than early glaciations and hence may have destroyed any landform or sedimentary evidence of earlier glaciations. Furthermore, the intense denudation, mainly by fluvial and mass movement processes, which characterize these wetter environments, results in rapid erosion and re-sedimentation of glacial and associated landforms, which also contributes to their poor preservation potential.

Jon Harbor - One of the best experts on this subject based on the ideXlab platform.

  • Cosmogenic nuclide evidence for minimal erosion across two subglacial sliding boundaries of the late glacial fennoscandian ice sheet
    Geomorphology, 2006
    Co-Authors: Jon Harbor, Arjen P Stroeven, Derek Fabel, D Elmore, Johan Kleman, Anders Clarhall, David Fink
    Abstract:

    Abstract The existence of sliding and frozen bed areas under ice sheets is significant in understanding basal thermal regimes, patterns of erosion and landform development, and in constraining boundary conditions for the reconstructions of ice sheets. Recognition of subglacial boundaries between sliding and frozen-bed areas for former ice sheets is typically based on distinct morphological contrasts between areas with glacial landform assemblages and relict areas showing little alteration of pre-existing features. Some of these boundaries, especially on continental shield areas, however, are clearly visible from air photos but have minimal topographic expression. Understanding the chronology and erosional development of such boundaries is important to provide insight into the pattern and persistence of basal conditions under ice sheets. Geomorphic evidence and Cosmogenic Radionuclide concentrations of bedrock outcrops on either side of two sliding boundaries on Ultevis and Arvestuottar, low-relief upland plateaus in northern Sweden, are consistent with negligible erosion in relict landscape (frozen bed) areas due to the last glaciation, but also indicate insignificant erosion in the sliding areas. Such a pattern and magnitude of landscape modification indicates that sliding was short lived in these areas, likely as a transient phase during deglaciation. These sites demonstrate that short periods of sliding are in some cases sufficient to produce landscapes that are recognized as ‘glacial’ from air photos. Thus, regions of sliding identified on shield areas must be viewed as the cumulative total area that has experienced sliding at any time during a glaciation. The actual extent of sliding areas during any single ice sheet phase is presumably considerably less than this cumulative total, which has important implications for establishing appropriate basal boundary conditions for ice sheet reconstructions.

  • using Cosmogenic Radionuclide concentrations to determine glacial erosion across alpine valleys
    Radiocarbon, 2006
    Co-Authors: Linda L Horn, Jon Harbor, D Elmore, Pankaj Sharma, Adam Dunne, Andrew Elmore
    Abstract:

    s 49 rate of stopped negative muons I_(z), the chemical compound factor fc, the probability of nuclear capture fD and the probability f* of the reaction channel after nuclear μ' capture to the investigated nuclide. The production due to fast muons is given by Pμ,fast(z) _ fast a with the flux of fast muons μ,fast The energy-dependent cross section a is given by a = a° Fe07 according to the Wolfendale rule with the mean muon energy Emean in GeV at the considered depth. With the PSI irradiations, the following probabilities f* of particle emission channels after u capture have been measured: f* _ (5.2 ± 0.6) 10'3 for O(μ',vμapxn)10Be [x =1-3], and f* _ (1.4 ± 0.4) 10'3 for S(μ',vaxn)26A1 [x = 2-4,6]. From the result of the oxygen irradiation and the earlier result obtained for 26A1 from the irradiation of quartz (Strack et al. 1994), the production ratio of 26A1 to 10Be after,u' capture in quartz has been deduced to be P(26Al)fP(i°Be) = 7.3 ± 1.5 (Heisinger et al. in preparation). In another experiment, the channel probability from Ca to 36C1 was measured. For the determination of the fast muon cross section a° of 10Be (from 0),14C (from 0), 26A1(from Si, S and Al), 36C1 (from Ca), 53Mn (from Fe) and 250Pb (from Tl), several targets have been irradiated at CERN. This work is still in progress. Depth profiles of 10Be and 26A1 in natural quartz samples were measured in northern Bavaria up to depths of 260 m and were compared with calculated profiles taking into account erosion. From this comparison, the erosion rate in the last million years was determined to be ca. 51um yr-1(Heisinger et al. in preparation).

  • quantifying the erosional impact of the fennoscandian ice sheet in the tornetrask narvik corridor northern sweden based on Cosmogenic Radionuclide data
    Geografiska Annaler Series A-physical Geography, 2002
    Co-Authors: Arjen P Stroeven, Derek Fabel, Jon Harbor, Clas Hattestrand, Johan Kleman
    Abstract:

    Despite spectacular landform evidence of a dominant role for glacial action in shaping landscapes under former northern hemisphere ice sheets, there is little quantitative evidence for rates and patterns of erosion associated with specific glaciations. Here we use Cosmogenic nuclide data to assess rates of subglacial erosion underneath the Fennoscandian ice sheet. By testing whether there are remnant nuclide concentrations in samples taken from sites that include both relict areas and features and landscapes typically associated with vigorous glacial erosion, we can constrain the level and pattern of modification that resulted from the last glaciation. Cosmogenic 10Be and 36Cl data from the Tornetrask region confirm the temporal and spatial variability of glacial erosion suggested by geomorphological mapping. At some sites, glacial erosion estimates in what appear to be heavily scoured areas indicate erosion of only c. 2 ± 0.4 m of bedrock, based on Cosmogenic nuclide inheritance. This implies that the generation of severely scoured terrain in this study area required multiple glaciations. The overall modification produced by ice sheets along glacial corridors may be more restricted than previously thought, or may have occurred preferentially during earlier Quaternary glacial periods.

  • a relict landscape in the centre of fennoscandian glaciation Cosmogenic Radionuclide evidence of tors preserved through multiple glacial cycles
    Geomorphology, 2002
    Co-Authors: Arjen P Stroeven, Derek Fabel, Clas Hattestrand, Jon Harbor
    Abstract:

    The presence of well-developed tors, boulder fields, and weathering mantles in the Parkajoki area of northeastern Sweden, near the centre of Fennoscandian glaciation, has been used to suggest that these landscapes were preserved during all glacial cycles since ice-sheet initiation in the late Cainozoic. This implies that all successive large-scale glaciations must have had frozen bed conditions across this area to allow for subglacial landscape preservation. Cosmogenic 10Be and 26Al data from three tors and a meltwater channel in the Parkajoki area were used to test this hypothesis of landscape preservation through multiple glacial cycles. Apparent exposure ages of tor summit bedrock surfaces ranging between 79 and 37 ka in an area deglaciated at ∼11 ka are consistent with the interpretation of these features as relict landforms that have survived glaciation with little or no erosion. Single nuclide minimum exposure age data require that the tors have survived at least two complete glacial cycles. This estimate is based on (i) the approximate duration of periods of ice sheet cover versus ice free conditions as deduced from the DSDP 607 marine benthic foraminifer oxygen isotope record, in conjunction with (ii) a record of Fennoscandian ice sheet flow traces (and hence, ice sheet extent), and (iii) noting that Cosmogenic nuclides are accumulated only during ice free periods. In addition, mean Cosmogenic 26Al/10Be concentration ratios from two of the sites indicate a minimum model total history of 605 ka and a maximum erosion rate of 1.6 m Ma−1. Thus, the numerical ages confirm the overall qualitative interpretation of landscape preservation through multiple glacial cycles.

David Fink - One of the best experts on this subject based on the ideXlab platform.

  • evidence for slow late glacial ice retreat in the upper rangitata valley south island new zealand
    Quaternary Science Reviews, 2018
    Co-Authors: James Shulmeister, Glenn D Thackray, David Fink, Stefan Winkler, Rosabella Borsellino, Maree Hemmingsen, Tammy M Rittenour
    Abstract:

    Abstract A suite of Cosmogenic Radionuclide ages taken from boulders on lateral and latero-terminal moraines in the Rangitata Valley, eastern South Island, New Zealand demonstrates that relatively thick ice occupied valley reaches inland of the Rangitata Gorge until c. 21 ka. Thereafter ice began to thin, and by c. 17 ka it had retreated 33 km up-valley of the Rangitata Gorge to the Butler-Brabazon Downs, a structurally created basin in the upper Rangitata Valley. Despite its magnitude, this retreat represents a minor ice volume reduction from 21 ka to 17 ka, and numerous lateral moraines preserved suggest a relatively gradual retreat over that 4 ka period. In contrast to records from adjacent valleys, there is no evidence for an ice-collapse at c. 18 ka. We argue that the Rangitata record constitutes a more direct record of glacial response to deglacial climate than other records where glacial dynamics were influenced by proglacial lake development, such as the Rakaia Valley to the North and the major valleys in the Mackenzie Basin to the south-west. Our data supports the concept of a gradual warming during the early deglaciation in the South Island New Zealand.

  • catchment scale denudation and chemical erosion rates determined from 10be and mass balance geochemistry mt lofty ranges of south australia
    Geomorphology, 2016
    Co-Authors: Erick A Bestland, Caterina Liccioli, Lesja Soloninka, David J Chittleborough, David Fink
    Abstract:

    Abstract Global biogeochemical cycles have, as a central component, estimates of physical and chemical erosion rates. These erosion rates are becoming better quantified by the development of a global database of Cosmogenic Radionuclide 10 Be (CRN) analyses of soil, sediment, and outcrops. Here we report the denudation rates for two small catchments (~ 0.9 km 2 ) in the Mt. Lofty Ranges of South Australia as determined from 10 Be concentrations from quartz sand from the following landscape elements: 1) dissected plateaux, or summit surfaces (14.10 ± 1.61 t km − 2  y − 1 ), 2) sandstone outcrops (15.37 ± 1.32 t km − 2  y − 1 ), 3) zero-order drainages (27.70 ± 1.42 t km − 2  y − 1 ), and 4) stream sediment which reflect a mix of landscape elements (19.80 ± 1.01 t km − 2  y − 1 ). Thus, the more slowly eroding plateaux and ridges, when juxtaposed with the more rapidly eroding side-slopes, are leading to increased relief in this landscape. Chemical erosion rates for this landscape are determined by combining Cosmogenic denudation rates with the geochemical mass balance of parent rock, soil and saprolite utilizing zirconium immobility and existing mass balance methods. Two different methods were used to correct for chemical weathering and erosion in the saprolite zone that is shielded at depth from CRN production. The corrected values are higher than uncorrected values: total denudation of 33.24 or 29.11 t km − 2  y − 1 , and total chemical erosion of 15.64 or 13.68 t km − 2  y − 1 . Thus, according to these methods, 32–40% of the denudation is taking place by chemical weathering and erosion in the saprolite below CRN production depth. Compared with other similar areas, the overall denudation and chemical erosion rates are low. In most areas with sub-humid climates and tectonic uplift, physical erosion is much greater than chemical erosion. The low physical erosion rates in these Mt. Lofty Range catchments, in what is a relatively active tectonic setting, are thought to be due to low rainfall intensity during the winter wet season, which inhibits physical erosion such as land-sliding and debris flows.

  • Cosmogenic Radionuclide chronology of pre last glacial cycle moraines in the western arthur range southwest tasmania
    Quaternary Science Reviews, 2010
    Co-Authors: K Kiernan, David Fink, David Greig, Charles Mifud
    Abstract:

    Cosmogenic 10Be and 26Al exposure ages of 12 boulders from two moraine complexes in the Western Arthur Range of southwest Tasmania, which previously were considered to have been deposited during the Last Glacial Maximum, predate the Last Glacial Cycle. Zero-erosion minimum exposure ages range from 95 ka to 232 ka based on weighted mean 10Be and 26Al ages per boulder. For a reasonable choice of erosion rates, 10Be boulder ages range from 105 to 326 ka, respectively. Although a direct association of moraine construction to a specific marine isotope stage (MIS) glaciation is not definitive, erosion-corrected exposure ages indicate glacial advances commensurate with MIS-6 and -10, although the latter advance may be attributable to MIS-8 if the erosion rate correction is an over-estimate. Given the relatively close proximity of the dated moraines to their source cirques, this new Cosmogenic glacial chronology implies a very limited extent for any younger glacial advances that occurred in the Western Arthur Range during the Last Glacial Cycle (post MIS-5) including the global LGM.

  • Cosmogenic nuclide evidence for minimal erosion across two subglacial sliding boundaries of the late glacial fennoscandian ice sheet
    Geomorphology, 2006
    Co-Authors: Jon Harbor, Arjen P Stroeven, Derek Fabel, D Elmore, Johan Kleman, Anders Clarhall, David Fink
    Abstract:

    Abstract The existence of sliding and frozen bed areas under ice sheets is significant in understanding basal thermal regimes, patterns of erosion and landform development, and in constraining boundary conditions for the reconstructions of ice sheets. Recognition of subglacial boundaries between sliding and frozen-bed areas for former ice sheets is typically based on distinct morphological contrasts between areas with glacial landform assemblages and relict areas showing little alteration of pre-existing features. Some of these boundaries, especially on continental shield areas, however, are clearly visible from air photos but have minimal topographic expression. Understanding the chronology and erosional development of such boundaries is important to provide insight into the pattern and persistence of basal conditions under ice sheets. Geomorphic evidence and Cosmogenic Radionuclide concentrations of bedrock outcrops on either side of two sliding boundaries on Ultevis and Arvestuottar, low-relief upland plateaus in northern Sweden, are consistent with negligible erosion in relict landscape (frozen bed) areas due to the last glaciation, but also indicate insignificant erosion in the sliding areas. Such a pattern and magnitude of landscape modification indicates that sliding was short lived in these areas, likely as a transient phase during deglaciation. These sites demonstrate that short periods of sliding are in some cases sufficient to produce landscapes that are recognized as ‘glacial’ from air photos. Thus, regions of sliding identified on shield areas must be viewed as the cumulative total area that has experienced sliding at any time during a glaciation. The actual extent of sliding areas during any single ice sheet phase is presumably considerably less than this cumulative total, which has important implications for establishing appropriate basal boundary conditions for ice sheet reconstructions.

Related terms

Cosmogenic Radionuclide - 15 days free trial to Access Experts & Abstracts