March 2023 Meeting: Cascade Range magmatic uplift signaled by geophysical signals and disequilibrium topography of the Columbia River Gorge, USA – Nate Klema

Meeting Details:

Where: Fort Lewis College, Durango, CO, Sitter Family Hall, Room 710
When: Happy Hour and Dinner served from 5:30 to 6:30, talk and raffle from 6:30-on
Speaker: Nate Klema, University of Oregon
Talk Title: Cascade Range magmatic uplift signaled by geophysical signals and disequilibrium topography of the Columbia River Gorge, USA

Abstract of Talk:

In volcanic arcs topography is built through a combination of magmatic and tectonic processes
offset by erosion. Here the highest elevations are generally associated with the arc front where
mantle-derived magma is focused to the surface, resulting in the voluminous emplacement of
both erupted and intruded material. Both modes of magma emplacement contribute to
topographic growth, however little is understood about how these magmatic forcings interact
with background tectonics or climate-driven erosion to shape arc topography on geologic
timescales. Here we leverage the cross section of the Cascade Arc generated through persistent
fluvial incision of the Columbia River in the Columbia River Gorge to isolate the intrusive and
extrusive components of uplift and show that arc scale topography can be built through
persistent magmatism, and that signatures of landscape disequilibrium in fluvial tributaries of the
Columbia reflect these magmatic drivers. We show how ongoing magmatic forcing on the upper
crust from the emplacement of intrusions is recorded in regional geophysical signals, and argue
that resultant deviatoric stress concentrations in the upper crust can explain enigmatic arcmarginal
normal faulting, as well as off-axis focusing of monogenetic vents fields.