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Marine Incursions: Implications for crustal thinning and regional strain

Marine Incursions: Implications for crustal thinning and regional strain. Kristin McDougall U.S. Geological Survey Flagstaff, Arizona 86001 kris@usgs.gov with assistance from Ana Luisa Carreno, Rebecca Dorsey, Arturo Martin, and Michael Oskin. Questions. Number of incursions Age Extent

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Marine Incursions: Implications for crustal thinning and regional strain

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  1. Marine Incursions: Implications for crustal thinning and regional strain Kristin McDougall U.S. Geological Survey Flagstaff, Arizona 86001 kris@usgs.gov with assistance from Ana Luisa Carreno, Rebecca Dorsey, Arturo Martin, and Michael Oskin

  2. Questions • Number of incursions • Age • Extent • Environment

  3. Locations • Lower Colorado River • Salton Trough • Gulf of California

  4. Correlation lower Colorado River, Salton Trough, and Gulf of California

  5. Middle Miocene microfossils • Range of reworked planktic foraminifers or calcareous nannofossils

  6. Age diagnostic Middle Miocene Taxa Sections • Hermosillo/Guaymas • Cerro Prieto • Fish Creek • Whitewater/Cabazon • Laguna Salada • San Felipe • Tres Marias Islands

  7. Middle Miocene microfossils • Range of reworked planktic foraminifers or calcareous nannofossils

  8. Correlation lower Colorado River, Salton Trough, and Gulf of California

  9. Gulf of California Late Miocene ~ 6-8 MaPlio-Pleistocene <5.3 Ma

  10. Salton Trough Late Miocene ~ 6-8 Ma Plio-Pleistocene < 5.3 Ma

  11. Age of the Fish Creek section

  12. Whitewater and Cabazon Sections

  13. Paleoecology of the Whitewater and Cabazon sections

  14. Lower Colorado River

  15. Distribution of Foraminifers in the Bouse Formation

  16. Cross section of LCRP wells between Cibola and Parker

  17. Biofacies

  18. Paleoecology

  19. Questions • Number of incursions • Age • Extent • Environment

  20. Middle Miocene incursion • 11-14 Ma • In situ faunas suggest this incursion extends at least as far north as the Hermosillo and Guaymas • Reworked microfossils found further north. • The age of the sediments middle Miocene faunas are reworked in to becomes older to the north. • Northern limit of this incursion has not been determined. • Deposition occurred during warm climatic conditions and high sea level.

  21. Late Miocene incursion • 6-7 Ma • Extends as far north as San Gorgonio Pass, California, and as far east as Yuma, Arizona. • Wide variety of environments in a warm climatic interval and high sea level

  22. Plio-Pleistocene incursion • Post 5.3 Ma • Extends throughout most of the Salton Trough and lower Colorado River region as well as the current Gulf of California. • The marine section was strongly affected by the Colorado River, which rapidly filled the area with fresh water and sediment, reducing the marine influence • Wide variety of depositional environments

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