Geology Reference
In-Depth Information
A
Most recent
cooling event
Earlier
cooling event
Cooling Models
Earlier cooling event
Uplifted
PAZ or PRZ
PAZ or
PRZ
PAZ or
PRZ
0
40
0
12
60
Cooling Ages
at 20 Ma
Cooling Ages
Today
B
White Mtns.,
California
Bedrock
Sample
depth below
unconformity
5 km
Sample site
Cenoz. fill
Cenoz. volc.
Mesoz. basment
C
0
White Mtns.
Cooling Ages
U-Th-He
Fission-
Track
Laramide
cooling
2
40°C
apatite (U-Th)/He
partial retention
zone
60°C
4
80°C
apatite fission-track
partial annealing zone
6
110°C
rapid exhumation
at 12 Ma
Pliocene
faulting
8
0
20
40
60
80
Apparent Age (Ma)
Fig. 7.21
Reconstruction of rock uplift and paleogeothermal gradients with low-temperature thermochronology.
A. Models for cooling ages in the crust. (Left) Ages at 20 Ma. Below the base of the partial retention zone (PRZ) or
partial annealing zone (PAZ), cooling ages are zero, whereas above the top of the PAZ or PRZ, cooling ages record
cooling due to previous erosion or thermal events. If the ages are all about the same, they indicate rapid cooling of
a crustal thickness at least as thick as is preserved. (Right) Ages at present. Ages below the modern PAZ or PRZ
