P–PINI: A cosmogenic nuclide burial dating method for landscapes undergoing non-steady erosion

Nørgaard, Jesper; Jansen, John D.; Neuhuber, Stephanie; Ruszkiczay-Rüdiger, Zsófia; Knudsen, Mads Faurschou

doi:10.1016/j.quageo.2022.101420

Cited by 10 publications

(11 citation statements)

References 46 publications

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“…Further research is needed in this and similar landscapes to separate (i) exposure and burial from (ii) bedrock erosion histories and (iii) the effects of boulder transportation, disturbance, burial and recycling. This may require establishing the full range and variability of TCN inventories across different landscape domains, on landforms in those domains, and for different nuclides across and at depth within multiple rock and boulder surfaces (Skov et al, 2020, Knudsen et al, 2020, Nørgaard et al, 2023, Andersen et al, 2020).…”

Section: Discussionmentioning

confidence: 99%

Inherited terrestrial cosmogenic nuclides in landscapes of selective glacial erosion: lessons from Lochnagar, Eastern Grampian Mountains, Scotland

Hall,

Sugden,

Binnie

et al. 2024

J Quaternary Science

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Inheritance from prior exposure often complicates the interpretation of terrestrial cosmogenic nuclide (TCN) inventories in glaciated terrain. Lochnagar, a mountain in eastern Scotland, holds a clear geomorphological record of corrie glaciation and the thinning of the last Scottish ice sheet over the last ~15 ka. Yet attempts to date the main stages in deglaciation after sampling of 21 granite boulders for 10Be, 26Al and 14C from corrie moraines, an ice sheet lateral moraine and boulder spreads revealed widespread, but variable, TCN inheritance. Only the youngest boulder ages fit within the range of expected deglaciation ages. To identify the sources of geological uncertainty, we provide simple models of ice cover duration and erosion histories for plateau, corrie and strath landscape domains, identify the variable nuclide inheritance that derives from different sources for boulders in these domains, and outline the effects of rotation, splitting and erosion of boulders during glacial transport. The combined effects increase clustering around arbitrary mean TCN values that exceed deglaciation ages. A further implication is that boulders have survived beneath overriding ice sheets. Such boulder trapping at Lochnagar may have resulted from topographic controls on katabatic winds and surface ablation acting on a thinning, cold‐based ice sheet.

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Section: Discussionmentioning

confidence: 99%

Inherited terrestrial cosmogenic nuclides in landscapes of selective glacial erosion: lessons from Lochnagar, Eastern Grampian Mountains, Scotland

Hall,

Sugden,

Binnie

et al. 2024

J Quaternary Science

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“…While the largest extent of the north Alpine glaciers (Most Extensive Glaciation of the Swiss Foreland cf. Schlüchter, 1988) was assigned to the Möhlin glaciation (Preusser et al, 2011) and recently dated to 500±100 ka and thus to MIS 12 through burial dating with cosmogenic 26 Al and 10 Be (Dieleman et al, 2022), a re-evaluation of the reported concentrations of the cosmogenic nuclides yielded an age that is more consistent with MIS 6 (Nørgaard et al, 2023). The Quaternary fill of overdeepenings can now be placed into the aforementioned chronological framework of glacial advances onto the Swiss plateau during the past glaciations (Figure 8).…”

Section: Chronological Frameworkmentioning

confidence: 99%

Overdeepening or tunnel valley of the Aare glacier on the northern margin of the European Alps: Basins, riegels, and slot canyons

Schlunegger,

Kissling,

Bandou

et al. 2024

Preprint

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Abstract. This work summarizes the results of an interdisciplinary project where we aimed to explore the origin of overdeepenings or tunnel valleys through a combination of a gravimetry survey, drillings, dating and a synthesis of previously published work. To this end, we focused on the Bern area, Switzerland, situated on the northern margin of the European Alps. In this region, multiple advances of piedmont glaciers during the Quaternary glaciations resulted in the carving of the main overdeepening of the Aare River valley (referred to as Aare main overdeepening). This bedrock depression is tens of km long and up to several hundreds of meters to a few kilometers wide. We found that in the Bern area, this main overdeepening is made up of two >200 m-deep troughs that are separated by a c. 5 km-long and up to 150 m-high transverse rocky ridge, interpreted as a riegel. The basins and the riegel are overlain by a >200 m- and 100 m-thick succession of Quaternary sediments, respectively. The bedrock itself is made up of a Late Oligocene to Early Miocene suite of consolidated clastic deposits, which are part of the Molasse foreland basin, whereas the Quaternary suite comprises a middle Pleistocene to Holocene succession of glacio-lacustrine gravel, sand and mud. A synthesis of published gravimetry data revealed that the upstream stoss side of the bedrock riegel is c. 50 % flatter than the downstream lee side. In addition, information from >100 deep drillings reaching depths >50 m suggests that the bedrock riegel is dissected by an anastomosing network of slot canyons. We propose that these canyons established the hydrological connection between the upstream and downstream basins during their formation. Based on published modelling results, we interpret that the riegels and canyons were formed through incision of subglacial meltwater during a glacier’s decay state, when large volumes of meltwater were released. Such a situation has repeatedly occurred since the Middle Pleistocene Transition approximately 800 ka ago, when large and erosive piedmont glaciers began to advance far into the foreland. This resulted in the deep carving of the inner-Alpine valleys, and additionally in the formation of overdeepenings on the plateau on the northern margin of the Alps.

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“…Further removed from these correlative landform ages is the timing of surface-breaking faulting. For example, available evidence implies deposition of the ancient basin-filling Nenana Gravel between 4.5 and 1 Ma (Athey et al, 2006;Nørgaard et al, 2023), effectively leaving a 4.5 million yearlong time interval during which faulting of the unit may have occurred. Hence, the rates resulting from the correlations of Bemis (2010) contain prominent but unquantifiable epistemic uncertainty in that it is unclear what relationship the assigned ages bear to either landform formation or hypothesized abandonment via faulting.…”

Section: Landform Age Uncertaintiesmentioning

confidence: 99%

Supplemental Material: Rapid active thrust faulting at the northern Alaska Range front

Bender¹,

al.²

2023

Preprint

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P–PINI: A cosmogenic nuclide burial dating method for landscapes undergoing non-steady erosion

Cited by 10 publications

References 46 publications

Inherited terrestrial cosmogenic nuclides in landscapes of selective glacial erosion: lessons from Lochnagar, Eastern Grampian Mountains, Scotland

Inherited terrestrial cosmogenic nuclides in landscapes of selective glacial erosion: lessons from Lochnagar, Eastern Grampian Mountains, Scotland

Overdeepening or tunnel valley of the Aare glacier on the northern margin of the European Alps: Basins, riegels, and slot canyons

Supplemental Material: Rapid active thrust faulting at the northern Alaska Range front

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