Stochastic processes of soil production and transport: Erosion rates, topographic variation and cosmogenic nuclides in the Oregon coast range

Arjun Heimsath, William E. Dietrich, Kunihiko Nishiizumi, Robert C. Finkel

Research output: Contribution to journalArticle

206 Citations (Scopus)

Abstract

Landscapes in areas of active uplift and erosion can only remain soil-mantled if the local production of soil equals or exceeds the local erosion rate. The soil production rate varies with soil depth, hence local variation in soil depth may provide clues about spatial variation in erosion rates. If uplift and the consequent erosion rates are sufficiently uniform in space and time, then there will be tendency toward equilibrium landforms shaped by the erosional processes. Soil mantle thickness would adjust such that soil production matched the erosion. Previous work in the Oregon Coast Range suggested that there may be a tendency locally toward equilibrium between hillslope erosion and sediment yield. Here results from a new methodology based on cosmogenic radionuclide accumulation in bedrock minerals at the base of the soil column are reported. We quantify how soil production varies with soil thickness in the southern Oregon Coast Range and explore further the issue of landscape equilibrium. Apparent soil production is determined to be an inverse exponential function of soil depth, with a maximum inferred production rate of 268 m Ma-1 occurring under zero soil depth. This rate depends, however, on the degree of weathering of the underlying bedrock. The stochastic and large-scale nature of soil production by biogenic processes leads to large temporal and spatial variations in soil depth; the spatial variation of soil depth neither supports nor rejects equilibrium morphology. Our observed catchment-averaged erosion rate of 117 m Ma-1 is, however, similar to that estimated for the region by others, and to soil production rates under thin and intermediate soils typical for the steep ridges. We suggest that portions of the Oregon Coast Range may be eroding at roughly the same rate, but that local competition between drainage networks and episodic erosional events leads to landforms that are out of equilibrium locally and have a spatially varying soil mantle.

Original languageEnglish (US)
Pages (from-to)531-552
Number of pages22
JournalEarth Surface Processes and Landforms
Volume26
Issue number5
DOIs
StatePublished - May 2001
Externally publishedYes

Fingerprint

stochasticity
erosion rate
erosion
coast
soil depth
soil
spatial variation
landform
bedrock
uplift
cosmogenic radionuclide
mantle
episodic event
drainage network
sediment yield
soil column
hillslope
event
methodology
temporal variation

Keywords

  • Be and Al
  • Dynamic equilibrium
  • Erosion
  • Landscape evolution
  • Soil production

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)
  • Earth-Surface Processes
  • Geography, Planning and Development

Cite this

Stochastic processes of soil production and transport : Erosion rates, topographic variation and cosmogenic nuclides in the Oregon coast range. / Heimsath, Arjun; Dietrich, William E.; Nishiizumi, Kunihiko; Finkel, Robert C.

In: Earth Surface Processes and Landforms, Vol. 26, No. 5, 05.2001, p. 531-552.

Research output: Contribution to journalArticle

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