Abstract
Abstract. Recent work has highlighted a strong, worldwide, alpine glacial impact on
orogen erosion rates over the last 2 Ma. While it may be assumed that
glaciers increased erosion rates when active, the degree to which past
glaciations influence Holocene erosion rates through the adjustment of
topography is not known. In this study, we investigate the influence of
long-term tectonic and post-glacial topographic controls on erosion in a
glaciated orogen: the Olympic Mountains, USA. We present 14 new 10Be and
26Al analyses which constrain Holocene erosion rates across the Olympic
Mountains. Basin-averaged erosion rates scale with basin-averaged values of 5 km local relief, channel steepness, and hillslope angle throughout the range,
similar to observations from non-glaciated orogens. These erosion rates are
not related to mean annual precipitation or the marked change in Pleistocene
alpine glacier size across the range, implying that glacier modification of
topography and modern precipitation parameters do not exert strong controls
on these rates. Rather, we find that despite spatial variations in glacial
modification of topography, patterns of recent erosion are similar to those
from estimates of long-term tectonic rock uplift. This is consistent with a
tectonic model where erosion and rock uplift patterns are controlled by the
deformation of the Cascadia subduction zone.
Funder
European Research Council
Subject
Earth-Surface Processes,Geophysics
Cited by
8 articles.
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