Knowledge graph centered on Cosmogenic ¹⁰Be surface exposure dating with 72 nodes and 137 connections. Top connected: Rocky Mountain Biological Laboratory, Gothic, precipitation, biogeochemical reactions, Colorado River.
Method synopsis
Standard method for determining exposure ages of rock surfaces using in-situ produced cosmogenic ¹⁰Be nuclides measured by accelerator mass spectrometry. Involves sample collection, quartz purification, chemical processing, and AMS measurement.
Synthesized from method descriptions across 1 paper using this protocol.
Procedure from a recent peer-reviewed implementation
Collected quartz monzonite and quartzite boulders with broad horizontal surfaces deposited on moraine crests. Sampled boulders on average 53 ± 23 cm (1σ) measured above ground surface. Sample thickness and mass ranged from 2–4 cm and 1–3 kg, respectively.
Quantities: 24 total samples from 6 sites, boulder surfaces averaged 53 ± 23 cm heightDuration: Not specifiedConditions: Field sampling conducted at sites across East River watershed
Data were collected in the field by measuring the angle above the horizon at 20° azimuthal increments using a compass and clinometer.
Quantities: Measurements at 20° azimuthal increments (18 measurements per sample)Duration: Not specifiedConditions: Field conditions at sample locations
Equipment: compass, clinometer
Sample preparation for cosmogenic analysis
Samples were crushed and sieved to target grain size of 250–850 μm. Quartz grains were isolated using rare earth hand magnet, Outotec magnetic roll separator, froth flotation, and dilute acid treatment. Quartz purification accomplished by repeated etching in dilute hydrofluoric acid.
Quantities: Target grain size 250–850 μm, sample masses 1–3 kg
Duration: Not specified
Conditions: Laboratory processing at University of Massachusetts Amherst
Equipment: rare earth hand magnet, Outotec magnetic roll separator, hydrofluoric acid
¹⁰Be measurement
¹⁰Be fraction isolated using ion chromatography and chemically isolated using procedures of Ditchburn and Whitehead (1994) and Stone (2001). Samples heated in quartz crucible with gas torch until BeO glowed orange for 1 minute, then packed with Nb powder into targets for measurement by accelerator mass spectrometry.
Quantities: ¹⁰Be/⁹Be ratios measured against AMS standard 07KNSTD with known ratio of 2.85 × 10⁻¹²Duration: Not specifiedConditions: Lawrence Livermore National Laboratory
Equipment: quartz crucible, gas torch, accelerator mass spectrometer