Evaluating the temperature dependence of bedrock hillslope erosion in the Mont Blanc massif using in situ cosmogenic 3He-10Be-14C

The erosion of cold bedrock hillslopes in alpine environments depends not only on rates of frost weathering and accumulated rock damage, but additionally on the removal of the weathered material from the bedrock surface. In the Mont Blanc massif, steep bedrock faces with exposure ages sometimes much older than 50,000 years sit in close proximity to actively-eroding rockwalls, suggesting a more complex relationship between temperature and erosion rates than encompassed by the proposed &#8220;frost-cracking window.&#8221; Stochastic events like rockfalls and rock avalanches, despite their rarity, contribute a non-trivial proportion of the total sediment budget in alpine permafrost regions, adding to the contribution from background &#8220;steady-state&#8221; erosion. Employing a methodology based on the combination of in-situ cosmogenic nuclides 3He -10Be-14C, we test the temperature-dependence of high-alpine erosion while taking into account erosional stochasticity.From cosmogenic 10Be concentrations of amalgamated samples collected on the Aiguille du Midi (3842 m a.s.l.) in the Mont Blanc massif, we find an order of magnitude difference in erosion rate across the peak&#8217;s surface. Our preliminary measured erosion rates, ranging between appx. 0.03 mm yr-1 and 1.0 mm yr-1, correlate neither with modern temperature measurements from borehole thermistors, nor with our current estimates of bedrock cosmogenic 3He-derived paleotemperatures. The corresponding cosmogenic 14C/10Be ratios (between 1.70 and 4.0) for these erosion rates indicate that our measurements are not biased by recent stochastic rockfall events. Our current results therefore suggest that on geomorphic timescales, bedrock hillslope erosion rates are not set solely by rates of frost-cracking, but rather by the combined effects of frost-cracking and permafrost thaw-induced rockfalls. These insights are relevant both for short-term monitoring of alpine permafrost and associated geohazards under a warming climate, as well as studies of proposed &#8220;buzzsaws&#8221; operating on glacial-interglacial timescales.

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Limited Pliocene/Pleistocene glaciation in Deep Freeze Range, northern Victoria Land, Antarctica, derived from in situ cosmogenic nuclides

Antarctic Science ◽

10.1017/s0954102003001603 ◽

2003 ◽

Vol 15 (4) ◽

pp. 493-502 ◽

Cited By ~ 29

Author(s):

PETER OBERHOLZER ◽

CARLO BARONI ◽

JOERG M. SCHAEFER ◽

GIUSEPPE OROMBELLI ◽

SUSAN IVY OCHS ◽

...

Keyword(s):

Cosmogenic Nuclides ◽

Dry Valleys ◽

Climate Regime ◽

Erosion Rates ◽

Terra Nova Bay ◽

New Information ◽

Victoria Land ◽

Exposure Ages ◽

Middle Pliocene

The question of how stable the climate in Antarctica has been during the last few million years compared to the rest of the planet is still controversial. This study attempts to add new information to the discussion by reconstructing the timing and spatial extent of glacial advances in northern Victoria Land over tens of thousands to millions of years. In Terra Nova Bay region, surface exposure ages and erosion rates of glacially rounded bedrock and glacial erratics have been determined using the cosmogenic nuclides 3He, 10Be and 21Ne. Three morphological units have been analysed. They yield minimum ages of 11 to 34 ka, 309 ka, and 2.6 Ma, respectively. Erosion rates were as low as 20 cm Ma−1 since middle Pliocene time. Taking erosion into account, the oldest surface is 5.3 Ma old. Pleistocene glacier advances had considerable extent, reaching up to 780 m above modern ice levels, but have been restricted to the valleys since at least mid-Pliocene. The existence of landscapes of mid-Pliocene age in northern Victoria Land implies that the climatic stability of the McMurdo Dry Valleys is not unique within the Transantarctic Mountains, but rather the expression of a constantly cold and hyperarid climate regime in entire Victoria Land.

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Benthic Habitats and the Effects of Fishing

Benthic Habitats and the Effects of Fishing ◽

10.47886/9781888569605.ch37 ◽

2005 ◽

Keyword(s):

Gulf Of Mexico ◽

Benthic Communities ◽

Continental Shelves ◽

Order Of Magnitude ◽

Natural Change ◽

Nitrogen Contents ◽

Magnitude Difference ◽

Range Of Values ◽

Potential Tool

Abstract. Sediment oxygen consumption (SOC) is metabolically related to the benthic community productivity of continental shelves and margins. These areas have economical relevance for regional fisheries. The aim of this study is to evaluate SOC of the soft-bottom benthic communities in the southwestern Gulf of Mexico and provide rates in areas of varied trawling incidence in the region. Box-cored sediment was incubated at in situ temperature in benthic microcosm incubation chambers and sub-sampled for bacteria, meiofauna, and macrofauna. Environmental factors were measured in bottom water and sediment. The SOC values ranged from 6.12 to 79.9 mL O2 • m–2 • d–1 and correlated significantly to depth, grain size, and nitrogen contents in the sediment. A significant correlation was also found between SOC and the infaunal biomass. The proportion of bacteria to meiofauna and bacteria to macrofauna could be related to SOC in different regions. The range of SOC values from the continental shelves in the southwestern Gulf of Mexico were within the range of values recorded in seasonally pulsed sites and highly organic matter enriched areas within the region. We found an order of magnitude difference between the metabolic rates derived from SOC in this study and those reported for the northern Gulf of Mexico. The SOC rates can indicate bottom conditions in a region and should be considered as a potential tool in evaluating natural change and the effects of fishing activities on seabed habitats.

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Examining erosion in New Zealand over millennial timescales using in-situ 10Be and 14C

10.5194/egusphere-egu2020-9309 ◽

2020 ◽

Author(s):

Duna Roda-Boluda ◽

Taylor Schilgen ◽

Maarten Lupker ◽

Wittmann Hella ◽

Prancevic Jeff ◽

...

Keyword(s):

New Zealand ◽

Erosion Rate ◽

Sediment Flux ◽

Short Term ◽

Sediment Fluxes ◽

Landslide Activity ◽

Erosion Rates ◽

Order Of Magnitude

Landslides are the major erosional process in many orogens, and one of the most sensitive erosional process to tectonic and climatic perturbations. However, it remains extremely difficult to constrain long-term or past rates of landslide activity, and hence their contribution to long-term landscape evolution and catchment sediment fluxes, because the physical records of landsliding are often removed in <102 yrs. Here, we use the in-situ 10Be and in-situ 14C concentrations of recent landslide deposits and catchments from the Fiordland and the Southern Alps of New Zealand to: (a) estimate landslide frequencies over 103-104 yr timescales, which we compare against landslide inventories mapped from air photos (<102 yrs) to estimate changes in landslide activity, (b) quantify catchment-averaged erosion rates, and landslide&#8217;s contribution to those erosional fluxes, and (c) test whether paired 14C-10Be measurements can be used to trace erosional depth-provenance and identify transient erosion rate changes. We show that 10Be concentrations on landslide deposits can be used to estimate landslide recurrence intervals and frequency over 103 yr timescales, and that 14C/10Be ratios reflect the depth-provenance of sediment, and possibly transient changes in erosion rates. The comparison of our 10Be-based long-term landslide frequencies with short-term published inventories suggests that landslide frequencies have increased towards the present by up to an order of magnitude. We compare sediment fluxes inferred from these long- and short-term landslide inventories with sediment flux estimates derived from 10Be catchment-averaged erosion rates, which allows us to examine fluctuations in erosion rate estimates from 101 to 103 yrs timescales.&#160;

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On Cosmic-Ray Exposure Ages of Terrestrial Rocks: A Suggestion

Radiocarbon ◽

10.1017/s0033822200014971 ◽

1995 ◽

Vol 37 (3) ◽

pp. 889-898 ◽

Cited By ~ 3

Author(s):

Devendra Lal

Keyword(s):

Cosmic Ray ◽

Cosmogenic Nuclides ◽

Clear Definition ◽

Erosion Rates ◽

Exposure Age ◽

Exposure History ◽

Definition Of ◽

Exposure Ages ◽

Cosmic Ray Exposure Ages

An important recent development in the field of geomorphology has been the application of in-situ cosmic-ray-produced nuclides to obtain model erosion rates and surface exposure ages. These concepts emerged some four decades ago in studies of cosmogenic nuclides in meteorites, but cannot generally be used analogously for terrestrial rocks. The differences in the two cases are outlined. For the case of steady-state erosional histories, the terrestrial surface exposure ages depend on the half-life of the radionuclide studied. A suggestion is made for presenting the surface exposure ages, which allows a clear definition of the meaning of the estimated exposure ages. In the case of a discrete exposure history, the meaning of “exposure age”—which should more appropriately be called “event age”—is however quite unambiguous.

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Viscosity of Mixtures of α-Tocopherol Acetate + Mesitylene

Zeitschrift für Naturforschung A ◽

10.1515/zna-2009-7-813 ◽

2009 ◽

Vol 64 (7-8) ◽

pp. 503-506

Author(s):

Elżbieta Szwajczaka ◽

Ryszard Stagraczyński ◽

Henryk Herba ◽

Jolanta Świergielb ◽

Jan Jadżyn

Keyword(s):

Temperature Dependence ◽

Negative Deviation ◽

Viscosity Measurements ◽

Maximum Value ◽

Tocopherol Acetate ◽

Strong Negative Deviation ◽

Order Of Magnitude ◽

Increasing Temperature ◽

Magnitude Difference ◽

Vitamine E

AbstractThe paper presents results of the share viscosity measurements performed as a function of temperature and concentration for mixtures of α-tocopherol acetate (vitamine E acetate) and mesitylene, two liquids of essentially different viscosity (four order of magnitude difference at 280 K). The viscosity/ temperature dependence for pure α-tocopherol acetate as well as for the mixtures studied can be well described with the Vogel-Fulcher-Tammann equation. The viscosities of the mixtures exhibit a strong negative deviation from the rule of additive dependence on concentration and for increasing temperature the maximum value of the deviation shows an exponential decreasing.

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Cosmogenic in situ production of radionuclides: Exposure ages and erosion rates

Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms ◽

10.1016/s0168-583x(00)00204-4 ◽

2000 ◽

Vol 172 (1-4) ◽

pp. 790-795 ◽

Cited By ~ 20

Author(s):

B Heisinger ◽

E Nolte

Keyword(s):

Erosion Rates ◽

Exposure Ages ◽

In Situ Production

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Precision of terrestrial exposure ages and erosion rates estimated from analysis of cosmogenic isotopes produced in situ

Journal of Geophysical Research Atmospheres ◽

10.1029/95jb02911 ◽

1995 ◽

Vol 100 (B12) ◽

pp. 24637-24649 ◽

Cited By ~ 30

Author(s):

Alan R. Gillespie ◽

Paul R. Bierman

Keyword(s):

Cosmogenic Isotopes ◽

Erosion Rates ◽

Exposure Ages

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TEM Studies and Contact Resistance of Au/Ni/Ti/Ta/n-GaN Ohmic Contacts

MRS Proceedings ◽

10.1557/proc-764-c3.17 ◽

2003 ◽

Vol 764 ◽

Cited By ~ 3

Author(s):

D.N. Zakharov ◽

Z. Liliental-Weber ◽

A. Motayed ◽

S.N. Mohammad

Keyword(s):

Contact Resistance ◽

Ohmic Contacts ◽

High Resolution Electron Microscopy ◽

X Ray ◽

Electron Energy Loss Spectrometry ◽

Resolution Electron ◽

Order Of Magnitude ◽

Contact Surfaces ◽

Electron Energy Loss ◽

Magnitude Difference

AbstractOhmic Ta/Ti/Ni/Au contacts to n-GaN have been studied using high resolution electron microscopy (HREM), energy dispersive X-ray spectrometry (EDX) and electron energy loss spectrometry (EELS). Two different samples were used: A - annealed at 7500C withcontact resistance 5×10-6 Ω cm2 and B-annealed at 7750C with contact resistance 6×10-5 Ω cm2. Both samples revealed extensive in- and out-diffusion between deposited layers with some consumption ofGaNlayerand formation of TixTa1-xN50 (0<x<25) at the GaN interface. Almost an order of magnitude difference in contact resistances can be attributed to structure and chemical bonding of Ti-O layers formed on the contact surfaces.

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