1. Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center By David A. John

2. Introduction  Steeply tilted late Oligocene caldera system  record a number of unusual features  Extremely thick (>4-5.5 km) caldera related deposits  Lack of evidence of structural doming  Preservation of compositional zoning  Cogenetic plutonic rocks are exposed over depth range of~10 km

6. Stillwater Caldera Complex  Job Canyon (29-28 Ma)  Poco Canyon (25-23 Ma)  Eleven Mile Canyon (25-23 Ma)  Composite Freeman Creek pluton

10. Unusual features  Extreme thickness caldera related deposits (>4-5.5 km)

13. Unusual features continued  Preservation of compositional zoning

15. Caldera collapse  Miocene extension  Basement rocks tilted 40°-90°  Subvertical ring-fracture faults (>3-5 km) depth  Piston like blocks  Lack of evidence of structural doming

19. Conclusions  Oligocene caldera complex in the southern Stillwater Range  Extremely thick caldera related deposits due to extreme subsidence  Cogenetic plutonic rocks over a depth range of ~10 km due to tilting during Miocene extension