Cosmogenic 36Cl accumulation in unstable landforms 2. Simulations and measurements on eroding moraines

Marek G Zreda, F. M. Phillips, D. Elmore

Research output: Contribution to journalArticle

76 Citations (Scopus)

Abstract

Cosmogenic 36Cl surface exposure ages obtained for multiple boulders from single landforms are usually characterized by a variance larger than that of the analytical methods employed. This excessive boulder-to-boulder variability, progressively more profound with increasing age of landforms, is due to removal of soil and gradual exposure of boulders at the surface. In our gradual exposure model, boulders are initially buried in moraine matrix. With time, erosion lowers the moraine surface and the boulders are gradually exposed to cosmic rays. Because the cosmic ray intensity changes with depth, the boulders are subjected to variable production rates of the cosmogenic 36Cl. Initial depth of boulders and their chemical composition are variable, which results in different amounts of the accumulated cosmogenic 36Cl and thus different apparent ages of boulders. The shape of the resulting distribution of the apparent ages and the coefficient of variation depend on the erosion depth, while the first moment is a function of the true surface age and the erosion depth. These properties of the apparent age distributions permit calculation of the surface age, the erosion depth, and also the average erosion rate. We tested the model calculations using 26 boulders from a late Pleistocene moraine at Bishop Creek, Sierra Nevada, California. -from Authors

Original languageEnglish (US)
Pages (from-to)3127-3136
Number of pages10
JournalWater Resources Research
Volume30
Issue number11
StatePublished - 1994
Externally publishedYes

Fingerprint

Landforms
landforms
landform
Erosion
moraine
Cosmic rays
simulation
erosion
boulder
cosmic ray
exposure models
erosion rate
age structure
analytical method
Soils
analytical methods
chemical composition
Pleistocene
matrix
Chemical analysis

ASJC Scopus subject areas

  • Aquatic Science
  • Environmental Science(all)
  • Environmental Chemistry
  • Water Science and Technology

Cite this

Cosmogenic 36Cl accumulation in unstable landforms 2. Simulations and measurements on eroding moraines. / Zreda, Marek G; Phillips, F. M.; Elmore, D.

In: Water Resources Research, Vol. 30, No. 11, 1994, p. 3127-3136.

Research output: Contribution to journalArticle

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