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Early Mesozoic Tectonics

Early Mesozoic Tectonics. Eastern North American - Continental Breakup American West - The tale of 5 Orogenies. Early Mesozoic Plate Tectonics. Two main fronts: Breakup of Pangea Building of the American West. Paleogeography. Pangaea began to separate. Paleogeography.

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Early Mesozoic Tectonics

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  1. Early Mesozoic Tectonics Eastern North American - Continental Breakup American West - The tale of 5 Orogenies

  2. Early Mesozoic Plate Tectonics • Two main fronts: • Breakup of Pangea • Building of the American West

  3. Paleogeography • Pangaea began to separate

  4. Paleogeography • Tethys seaway formed • Site of modern Mediterranean

  5. Paleogeography • Rifting began first in north, then spread south

  6. Tectonic Events in Eastern U.S. • Rifting created fault basins • Evaporites accumulated as seawater leaked into basin

  7. Geologic Evidence of the Breakup Rifting: Volcanics Faulting Deep Basins

  8. Geologic Evidence of the Breakup Late Triassic and Early Jurassic sedimentary and volcanic rocks deposited in these basins comprise the Newark Supergroup. These grabens and half-grabens filled with sediment eroding from the Appalachians, as well as basaltic lava flows and diabase intrusions (sills and dikes).

  9. Tectonic Events in Eastern U.S. • Basins • Filled with clastic sediments • Arkose rich • Rapid deposition

  10. Tectonic Events in Eastern U.S. • Palisades Sill • Mafic intrusion associated with rifting • Near New York City

  11. Geologic Evidence of the Breakup The sediment in these Newark basins was deposited in continental sedimentary environments such as: 1.Alluvial fans 2.Rivers and floodplains (alluvial) 3.Lakes (lacustrine) 4.Deserts (aeolian or eolian) The sedimentary rocks are primarily non-marine red arkosic sandstone, siltstones, and shales. Dinosaur tracks are present locally. Some of the lake deposits are black and gray shales with the remains of fish, aquatic reptiles, and freshwater invertebrates.

  12. Geologic Evidence of the Breakup Dinosaur tracks in Newark Supergroup rocks, Dinosaur State Park, Rocky Hill, Connecticut.

  13. Geologic Evidence of the Breakup Trails in red Triassic siltstone, Culpeper Basin, Virginia.

  14. Geologic Evidence of the Breakup Impression of a non-marine bivalve in freshwater shale, Deep River Basin, North Carolina.

  15. Geologic Evidence of the Breakup Mudcracks in gray and red Triassic lacustrine shales, Culpeper Basin, Virginia.

  16. Geologic Evidence of the Breakup Columnar jointing in Early Jurassic lava flow, the Orange Mountain Basalt, in the Newark Basin, New Jersey.

  17. Geologic Evidence of the Breakup The Palisades along the western shore of the Hudson River, Palisades Park, NJ. The Palisades Sill is one of the largest and best-known sills in the U. S., and is about 300 m thick.

  18. Geologic Evidence of the Breakup

  19. Geologic Evidence of the Breakup

  20. Watchung Ridges Looking north from the hawk watch platform, towards Martinsville and the Second Watchung Ridge.

  21. Watchung Ridges Looking west from the hawk watch platform, towards the Quarry .

  22. Orange Mountain Basalt Great Falls of the Passaic River at Paterson, NJ, cuting through the Orange Mountain Basalt

  23. Orange Mountain Basalt Pillow basalts in the Orange Mountain Basalt

  24. Orange Mountain Basalt Paterson NJ

  25. Paleogeography • Salt domes • Thick evaporites built up in modern Gulf of Mexico • Formed salt domes • Petroleum reserves

  26. The Gulf of Mexico In the south-central US and the Gulf of Mexico area, limestones and evaporites were deposited in shallow seas. Deposition of evaporites probably began in the Triassic and continued into the Jurassic, indicating an arid climate. Salt and gypsum beds in the Gulf of Mexico exceed 1000 m thick. This suggests that the Gulf functioned as a great evaporating basin, concentrating waters from the Atlantic Ocean.

  27. North-south trending seismic profile illustrating movement of salt after deposition.

  28. Early Mesozoic Plate Tectonics

  29. Early Mesozoic Plate Tectonics • Pangea

  30. Tectonic Events in Western U.S. • Grew by accretion of exotic terrane • Island arc terranes • Accreted Golconda Arc • Microplates • Accreted Sonomia • Southeastern Oregon • Northern California and Nevada

  31. Cordilleran Tectonics • Antler • Sonoman • Nevadan • Sevier • Laramide

  32. Antler Orogeny • What? • Collision with Antler Arc or • Klamuth terrane • When? • Late Mississippian to Pennsylvannian • Where? • Mainly Nevada, No. California, SE Oregon and Idaho

  33. Antler Orogeny

  34. Antler Orogeny

  35. Antler Orogeny

  36. Antler Orogeny

  37. Antler Orogeny

  38. Sonoman Orogeny • What? • Collision with Sonomia Microcontinent • Golconda Terrane • When? • Late Permian to Early Triassic • Where? • Mainly Nevada and SE Oregon and N California

  39. Tectonic conditions and paleogeography along the Cordilleran region during the Late Permian and Early Triassic.

  40. Tectonic Events in Western U.S. • Accretion • Golconda Arc • Sonomia

  41. Sonoman Orogeny

  42. Sonoman Orogeny

  43. Sonoman Orogeny

  44. The American West

  45. Sonoman Orogeny

  46. Sonoman Orogeny • Subduction of oceanic plate and collision/overthrusting of Microcontinent (Sonomia) and island arc (Golconda Terrane) with western North American craton.

  47. Nevadan Orogeny • What? • Subduction zone moved under North Amer. • Batholiths and Melange • When? • Late Jurassic • Where? • Mainly California and Nevada

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