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Divergent Plate Boundaries

Divergent Plate Boundaries. Lithologic Associations. Global Patterns of Divergence. Doming continental lithosphere. What Processes are Illustrated? What Geologic Features would be Preserved?. Processes Accompanying Doming. Normal Faulting Earthquakes Volcanism

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Divergent Plate Boundaries

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  1. Divergent Plate Boundaries Lithologic Associations

  2. Global Patterns of Divergence

  3. Doming continental lithosphere What Processes are Illustrated? What Geologic Features would be Preserved?

  4. Processes Accompanying Doming • Normal Faulting • Earthquakes • Volcanism • What is the source of the magma? • Based on this source, what type of volcanism would you expect?

  5. The Dome Collapses – Rift Valleys, Horsts, Grabens and Half Grabens In Addition to the Faulting and Volcanism, What Other Processes would Operate Here? What types of rocks would you expect?

  6. Additional Processes Accompanying Collapse of the Dome • Weathering • Erosion • Deposition

  7. Additional Processes Accompanying Collapse of the Dome • How much weathering would you expect in this setting? • What would be the composition of the sediment? • How much modification of sediment would take place during transport? • What textures would you expect? • What patterns of deposition would you expect?

  8. As Lithosphere Stretches • Lithosphere thins • Mafic magma is added intrusively and extrusively • What happens to the density of the lithosphere? • Why? • What happens to the buoyancy of the lithosphere? • What is the result of this?

  9. Lithosphere Subsides Below Sea Level • Modern Linear Seas: Red Sea, Dead Sea, Persian Gulf • What would be the geologic record of this? • What happens to the tectonic activity on the edges of the continents?

  10. From Rifting to Drifting • Passive Margins of Continents drift away from axis of tectonic activity - Mid-Ocean Ridge (MOR) • As distance from MOR increases, continental margins cool, become more dense and subside – continental shelves • What kinds of sediments would you expect?

  11. From Doming to Rifting to Drifting

  12. Example of Rift Lithologic Association • Mesozoic rift basins up and down the Eastern Seaboard • Igneous and Sedimentary record in rift basins

  13. Evidence of Rifting – Palisades Sill

  14. Palisades Sill – lower contact

  15. Evidence of Relief – “Fanglomerates”

  16. Evidence of Relief - Arkose

  17. Rift Basins – Closed Drainage - Lakes

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