1. Dead orogens: Are they really? Crustal vP/vS ratio is
After Christensen, JGR 1996
Crustal vP/vS ratio is
sensitive to lithology:
Quartz most abundant
in the Cordillera and
older orogenic belts.
After Lowry & Pérez-Gussinyé, Nature 2011

2. Moho temperature from Te
from Pn velocity
Moho temperature from Te
Wet Qtz/Wet Olv
Dry Ano/Dry Olv
Schutt et al., e.g., this meeting…
 water & crustal
lithology contribute
to Te variations
Low-Te Cordillera:
High-Te Stable Interior:
Wet Quartz
Dry Feldspar
Wet Olivine
Dry Olivine

3. For Te < 30 km in
the Cordillera,
crustal lithology is
sometimes evident…
For larger Te in the
stable interior,
mantle water tends
to dominate the
picture.
Based on mapped
Te variation, the
Appalachian orogen
in central Atlantic
states seem
interesting…
vP/vS Te