COMPARISON OF DIKE AZIMUTHS IN THE INDEPENDENCE DIKE SWARM, CALIFORNIA, TO PALEOMAGNETIC DATA—IMPLICATIONS FOR CENOZOIC VE...
INTRODUCTION <ul><li>Geographic extent —Eastern Transverse Ranges to the central Sierra Nevada; 500 km </li></ul><ul><li>H...
PURPOSE To evaluate the consistency of IDS trends with vertical axis rotations based on published paleomag results for Mio...
COMPARISON OF DIKE AZIMUTHS TO PALEOMAGNETIC ROTATIONS Sierra Nevada and ranges to the east  Northeastern Mojave Desert
COMPARISON OF DIKE AZIMUTHS TO PALEOMAGNETIC ROTATIONS Eastern Mojave Desert Southern Mojave Desert and  Eastern Transvers...
DISCUSSION Mean domain azimuths of Independence dikes as measured today Mean domain azimuths of Independence dikes restore...
DISCUSSION Total Independence dikes azimuths restored for paleomagnetic rotations where paleomagnetic data available Total...
DISCUSSION <ul><li>Large deviations from the main trend of IDS may reflect: </li></ul><ul><li>Dike intrusions of other age...
CONCLUSIONS <ul><li>In most cases, local orientations of IDS are consistent with Miocene and younger rotations  </li></ul>...
THE END
Upcoming SlideShare
Loading in …5
×

COMPARISON OF DIKE AZIMUTHS IN THE INDEPENDENCE DIKE SWARM, CALIFORNIA, TO PALEOMAGNETIC DATA—IMPLICATIONS FOR LATE CENOZOIC VERTICAL AXIS ROTATIONS

410 views

Published on

Presentation for GSA-Cordilleran Section Meeting given May 2005

Published in: Technology, Travel
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
410
On SlideShare
0
From Embeds
0
Number of Embeds
12
Actions
Shares
0
Downloads
2
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide
  • COMPARISON OF DIKE AZIMUTHS IN THE INDEPENDENCE DIKE SWARM, CALIFORNIA, TO PALEOMAGNETIC DATA—IMPLICATIONS FOR LATE CENOZOIC VERTICAL AXIS ROTATIONS

    1. 1. COMPARISON OF DIKE AZIMUTHS IN THE INDEPENDENCE DIKE SWARM, CALIFORNIA, TO PALEOMAGNETIC DATA—IMPLICATIONS FOR CENOZOIC VERTICAL AXIS ROTATIONS R. F. Hopson Geological Information Services Reno, Nevada J. W. Hillhouse and K. A. Howard U.S. Geological Survey Menlo Park, California
    2. 2. INTRODUCTION <ul><li>Geographic extent —Eastern Transverse Ranges to the central Sierra Nevada; 500 km </li></ul><ul><li>Host rocks —PC to Jurassic sedimentary, igneous, metamorphic </li></ul><ul><li>Ages —139 –159 Ma, peaking ~148 Ma </li></ul><ul><li>Composition —Mafic to silicic </li></ul><ul><li>Texture —Microcrystalline to medium-grained, some porphyritic </li></ul><ul><li>Other —Cluster in domains (most dikes exhibit a preferred orientation) </li></ul>
    3. 3. PURPOSE To evaluate the consistency of IDS trends with vertical axis rotations based on published paleomag results for Miocene volcanic rocks METHODS <ul><li>Determined azimuths of ~3800 dikes in 40 domains by measuring orientations on geologic maps and aerial photographs </li></ul><ul><li>Dike orientations analyzed with Stereoplot and StereoWin </li></ul>
    4. 4. COMPARISON OF DIKE AZIMUTHS TO PALEOMAGNETIC ROTATIONS Sierra Nevada and ranges to the east Northeastern Mojave Desert
    5. 5. COMPARISON OF DIKE AZIMUTHS TO PALEOMAGNETIC ROTATIONS Eastern Mojave Desert Southern Mojave Desert and Eastern Transverse Ranges
    6. 6. DISCUSSION Mean domain azimuths of Independence dikes as measured today Mean domain azimuths of Independence dikes restored for paleomagnetic rotations where paleomagnetic data available
    7. 7. DISCUSSION Total Independence dikes azimuths restored for paleomagnetic rotations where paleomagnetic data available Total Independence dikes azimuths as measured today
    8. 8. DISCUSSION <ul><li>Large deviations from the main trend of IDS may reflect: </li></ul><ul><li>Dike intrusions of other ages </li></ul><ul><li>Crack filling at angles oblique or perpendicular to the swarm </li></ul><ul><li>Pre-Miocene rotations </li></ul><ul><li>Unrecognized domain boundaries between sites with paleomagnetic determinations and the dikes. </li></ul>
    9. 9. CONCLUSIONS <ul><li>In most cases, local orientations of IDS are consistent with Miocene and younger rotations </li></ul><ul><li>Several domains where dikes do not line up with the swarm </li></ul><ul><li>More age dates are needed, especially where dikes vary from the regional trend </li></ul><ul><li>IDS has limited usefulness for constraining late Cenozoic rotations </li></ul>
    10. 10. THE END

    ×