tilted middle tertiary ash-flow calderas and subjacent granitic plutons, southern stillwater range,...
Post on 21-Dec-2015
217 views
TRANSCRIPT
![Page 1: Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center](https://reader035.vdocuments.us/reader035/viewer/2022062407/56649d555503460f94a32b34/html5/thumbnails/1.jpg)
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
![Page 2: Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center](https://reader035.vdocuments.us/reader035/viewer/2022062407/56649d555503460f94a32b34/html5/thumbnails/2.jpg)
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
![Page 3: Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center](https://reader035.vdocuments.us/reader035/viewer/2022062407/56649d555503460f94a32b34/html5/thumbnails/3.jpg)
![Page 4: Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center](https://reader035.vdocuments.us/reader035/viewer/2022062407/56649d555503460f94a32b34/html5/thumbnails/4.jpg)
![Page 5: Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center](https://reader035.vdocuments.us/reader035/viewer/2022062407/56649d555503460f94a32b34/html5/thumbnails/5.jpg)
![Page 6: Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center](https://reader035.vdocuments.us/reader035/viewer/2022062407/56649d555503460f94a32b34/html5/thumbnails/6.jpg)
Stillwater Caldera Complex
Job Canyon (29-28 Ma) Poco Canyon (25-23 Ma) Eleven Mile Canyon (25-23 Ma) Composite Freeman Creek pluton
![Page 7: Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center](https://reader035.vdocuments.us/reader035/viewer/2022062407/56649d555503460f94a32b34/html5/thumbnails/7.jpg)
![Page 8: Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center](https://reader035.vdocuments.us/reader035/viewer/2022062407/56649d555503460f94a32b34/html5/thumbnails/8.jpg)
![Page 9: Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center](https://reader035.vdocuments.us/reader035/viewer/2022062407/56649d555503460f94a32b34/html5/thumbnails/9.jpg)
![Page 10: Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center](https://reader035.vdocuments.us/reader035/viewer/2022062407/56649d555503460f94a32b34/html5/thumbnails/10.jpg)
Unusual features
Extreme thickness caldera related deposits (>4-5.5 km)
![Page 11: Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center](https://reader035.vdocuments.us/reader035/viewer/2022062407/56649d555503460f94a32b34/html5/thumbnails/11.jpg)
![Page 12: Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center](https://reader035.vdocuments.us/reader035/viewer/2022062407/56649d555503460f94a32b34/html5/thumbnails/12.jpg)
![Page 13: Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center](https://reader035.vdocuments.us/reader035/viewer/2022062407/56649d555503460f94a32b34/html5/thumbnails/13.jpg)
Unusual features continued
Preservation of compositional zoning
![Page 14: Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center](https://reader035.vdocuments.us/reader035/viewer/2022062407/56649d555503460f94a32b34/html5/thumbnails/14.jpg)
![Page 15: Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center](https://reader035.vdocuments.us/reader035/viewer/2022062407/56649d555503460f94a32b34/html5/thumbnails/15.jpg)
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
![Page 16: Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center](https://reader035.vdocuments.us/reader035/viewer/2022062407/56649d555503460f94a32b34/html5/thumbnails/16.jpg)
![Page 17: Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center](https://reader035.vdocuments.us/reader035/viewer/2022062407/56649d555503460f94a32b34/html5/thumbnails/17.jpg)
![Page 18: Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center](https://reader035.vdocuments.us/reader035/viewer/2022062407/56649d555503460f94a32b34/html5/thumbnails/18.jpg)
![Page 19: Tilted middle Tertiary ash-flow calderas and subjacent granitic plutons, southern Stillwater Range, Nevada : Cross sections of an Oligocene igneous center](https://reader035.vdocuments.us/reader035/viewer/2022062407/56649d555503460f94a32b34/html5/thumbnails/19.jpg)
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